Protecting people against radiation exposure in the event of a radiological attack

Article Outline

• 1. Introduction
  • 1.1. Background
    • 1.1.1. Security of radiation sources
    • 1.1.2. Radiation-related malevolence
  • 1.2. Aim of the report
  • 1.3. Intended audience
• 2. Characterising the situation
  • 2.1. Potential scenarios
    • 2.1.1. Threat
    • 2.1.2. Initiators
    • 2.1.3. Common features
  • 2.2. Special features
    • 2.2.1. Location
    • 2.2.2. Public perception
    • 2.2.3. Source term characterisation
    • 2.2.4. Covert situations
    • 2.2.5. Public sentiment
    • 2.2.6. Advance warning
    • 2.2.7. Criminal investigation
    • 2.2.8. Challenges
  • 2.3. Planning
    • 2.3.1. ‘All-hazard’ planning
    • 2.3.2. Disaster management
    • 2.3.3. Medical preparedness
    • 2.3.4. Psychological issues
    • 2.3.5. Exercises
  • 2.4. Exposure
    • 2.4.1. Quantification
    • 2.4.2. Pathways
  • 2.5. Initial reaction
    • 2.5.1. Reacting to an explosion
    • 2.5.2. Reacting to an IND
  • 2.6. Response phases
    • 2.6.1. Rescue and early actions
    • 2.6.2. Recovery
    • 2.6.3. Restoration
  • 2.7. Links
• References
• Copyright

Executive summary

 

(a) This report is intended to respond to a widespread need for professional advice on measures to be undertaken should a radiological attack occur, leading to the malicious exposure of people to radiation and radioactive substances. Its main aim is to provide recommendations for protecting rescuers and affected members of the public against the radiation exposure that might be incurred as a result of such an event. The report re-affirms the applicability of the standing Commission’s recommendations to those potential situations. The Commission expects that relevant intergovernmental international organisations would establish guidance to assist national authorities to develop arrangements to deal with radiological attacks on the basis of the advice given in this report.

(b) The recommendations in the report are conceptually applicable to a wide range of conceivable attacks. These include the utilisation of radioactive materials for malicious purposes, such as the use of a ‘radioactive dispersion device’ (RDD), the sabotage of a nuclear facility to cause an unplanned release of radioactive material, and, in extreme cases, the detonation of an improvised nuclear device (IND). Since international advice and recommendations for dealing with nuclear accidents exist, and given that the special nuclear materials needed to construct an IND are not expected to be readily available, this report is mainly concerned with radiological attacks involving RDDs.

(c) Preparing for and responding to a radiological attack should be aimed at protecting people against arbitrary and unpredictable radiation exposure situations. Where national authorities have emergency plans in place for radiological accidents, the recommendations in the report provide additional or supplemental guidance. It should be noted, however, that although many aspects of the possible emergency scenarios resulting from a radiological attack may be similar to those arising from radiological accidents, these two types of emergencies differ in many respects. One difference is that a radiological attack would most likely be targeted at a public area, possibly located in an urban environment, where the presence of radiation or radioactive material is not anticipated and where there may be limited preparedness for responding with radiological protection measures. Moreover, the non-urban environmental dispersion conditions commonly assumed for planning emergencies in nuclear facilities may not be applicable to urban scenarios. The characterisation of the radiation source and its impact would probably be different as well. In addition, particular issues associated with the malicious character of the event, such as the criminal investigation that is likely to follow, will have an influence on the emergency planning and response.

(d) Planning for radiological protection in the aftermath of a radiological attack requires the establishment of appropriate programmes at both local and national levels. These programmes need to ensure that first responders and rescuers are adequately trained and have the proper equipment to identify the presence of radiation and radioactive contamination, and that radiation protection specialists are available to advise local and other relevant authorities. Whenever there is credible indication that an emergency is in fact a malicious attack, it may be prudent to assume that radiological, chemical, and/or biological agents are involved until proven otherwise. Therefore, if such credible indication exists, the situation calls for the adoption of an all-hazard approach to the response, which should be based on universal precautions combined with a prompt capability to identify all hazards present. This approach needs extensive co-ordination and co-operation of the responsible institutions, as well as experts in the fields of biological, chemical, and radiological threats and their associated hazards.

(e) Radiological attacks are characterised by the presence of radioactive substances. The quantity describing the amount of radioactive substances is the (radio) activity.¹ According to their activity, radioactive substances emit radiation that may expose both members of the public and rescuers coming to their aid. Radiation may be delivered from sources outside the body (external exposure) or by radioactive substances that may be incorporated into the body via inhalation, ingestion, or through open wounds or the skin (internal exposure). The potential health consequences caused by the exposure will depend on the amount of radiation received, the types of radiation involved, and the organs exposed. The amount of radiation exposure is measured in terms of the radiation dose² incurred by the affected individual.

(f) In most postulated scenarios associated with a radiological attack, radiation doses incurred by the majority of exposed people will probably be relatively small, perhaps lower than the typically elevated levels of the background radiation that is ubiquitous in nature, e.g. of the order of tens of millisieverts or less. Nonetheless, it is assumed that low radiation doses have the potential to induce some health effects (termed ‘stochastic’ effects), such as cancer and hereditable harm, that may become manifest many years after the exposure. The probability of occurrence of stochastic effects is very small, although it is assumed to increase proportionally with dose, and at low doses, the such effects are unlikely to be detectable. Conversely, people (perhaps only a small number) could also be exposed to high radiation doses, e.g. of the order of thousands of millisieverts. If such dose levels are incurred, clinically visible health effects (termed ‘deterministic’ effects) are almost certain to appear, usually as burns and other tissue reactions, within days of the exposure. Deterministic effects affect the functioning of tissues and organs with a severity that increases with dose. In severe cases, they can cause the death of exposed individuals. In radiological attacks with RDDs, only people closer to the event may incur the high doses required to induce deterministic effects (and only if large amounts of activity were involved). People affected by the detonation of an IND, and under some conditions, those affected by the radiological consequences of an act of sabotage in a nuclear installation, are more likely to be subject to high doses. The effects of different radiation doses and the likelihood of observable consequences are summarised in Table 1.

Table 1. Summary of radiation induced health effects

Dose	Effects on individuals	Consequences for an exposed population
Very low dose: about 10mSv (effective dose) or less	No acute effects; extremely small additional cancer risk	No observable increase in the incidence of cancer, even in a large exposed group
Low dose: towards 100mSv (effective dose)	No acute effects, subsequent additional cancer risk of less than 1%	Possible observable increase in the incidence of cancer, if the exposed group is large (perhaps greater than about 100,000 people)
Moderate dose: towards 1000mSv (acute whole body dose)	Nausea, vomiting possible, mild bone marrow depression; subsequent additional cancer risk of about 10%	Probable observable increase in the incidence of cancer, if the exposed group is more than a few hundred people
High dose: above 1000mSv (acute whole body dose)	Certain nausea, likely bone marrow syndrome; high risk of death from about 4000mSv of acute whole body dose without medical treatment.	Observable increase in the incidence of cancer
	Significant additional cancer risk

(g) The relationship between exposure routes, protective actions, and response phases in the aftermath of a radiological attack will vary depending on the specific circumstances. Exposure routes include: direct exposure to the source, source fragments or a damaged facility; external exposure from deposited contamination and contaminated skin and clothes; external exposure and internal contamination from the plume of dispersed radioactive substances; inhalation of resuspended material; inadvertent ingestion of contamination; and ingestion of contaminated food and water. The response phases are usually classified as rescue, recovery, and restoration. A large number of protective measures are available, some specific for each phase and some covering various phases.

(h) The aim of the protective measures must be to prevent deterministic effects and restrict the likelihood of stochastic effects. In addition to protecting people against the unpredictable exposure situations that will be created by an attack, the objectives include minimising the overall impact in terms of environmental contamination and general disruption, and attempting to restore normality as quickly as possible. The response must essentially be to: identify and characterise the emergency situation; provide medical care for injured people; attempt to avoid further exposures; gain control of the situation; prevent the spread of radioactive materials; provide accurate and timely information to the public; and institute a process for returning to normality, while dealing with psychological issues, such as distress, and misattribution and fear of illness, which will be major concerns. In the immediate response phase, exclusion distances usually employed in relation to explosives are a good starting point for controlling the site for radiation levels, and typical precautions at medical facilities for infectious agents are sufficient as a starting point for handling people that may be contaminated with radioactive material. It is emphasised that taking actions to avert exposures is much more effective than possible medical treatment after exposure has occurred. Treatment after an exposure is liable to reduce the number of health effects slightly (e.g. by a factor of approximately 2–3); in comparison, interventions with protective actions to avert the exposure occurring is likely to reduce the number of health effects by up to several orders of magnitude (e.g. by factors of approximately 10–1000).

(i) Responders undertaking recovery and restoration operations should be protected according to normal occupational radiological protection standards, and should not exceed internationally accepted occupational dose limits. This restriction may be relaxed for informed volunteers undertaking urgent rescue operations, and is not applicable for volunteered life-saving actions whenever the benefit to others clearly outweighs the rescuer’s own risk. However, since specific protection measures have been recommended for female workers who may be pregnant or are nursing an infant, and taking account of the unavoidable uncertainties surrounding early response measures in the event of a radiological attack, female workers in those conditions should not be employed as first responders undertaking life-saving or other urgent actions. The recommended dose guidance values for restraining the occupational exposure of responders are shown in Table 2.

Table 2. Guidance for occupational exposure

Type of emergency operation		Dose guidance value
Rescue operations*	Saving life, preventing serious injury, or actions to prevent the development of catastrophic conditions.	In principle, for life-saving operations, no dose restrictions are recommended if, and ONLY IF, the benefit to others clearly outweighs the rescuer’s own risk
	Other immediate and urgent actions to prevent injuries or large doses to many people	All reasonable efforts should be made to keep doses below twice the maximum single year limits (see below)
Other operations, including recovery and restoration operations		Normal occupational dose limits apply, i.e.:
		• a limit on effective dose of 20mSv/year, averaged over 5years (i.e., a limit of 100mSv in 5years), with the further provision that in any single year:
		• the effective dose should not exceed 50mSv and
		• the equivalent dose should not exceed –150mSv for the lens of the eye –500mSv for the skin (average dose over 1cm2 of the most highly irradiated area of the skin), and –500mSv for the hands and feet

*Under conditions that may lead to doses above normal occupational exposure limits, workers should be volunteers and should be instructed in dealing with radiation hazards to allow them to make informed decisions. Female workers who may be pregnant or nursing should not participate in such operations.

(j) The immediate countermeasures to protect the public in the rescue phase are primarily caring for people with traumatic injuries and controlling access to the scene, and subsequently providing affected people with respiratory protection measures and, whenever necessary and feasible, minimising the possible spread of contamination with radioactive material. Caring for people should be supported by triage and disposition following quick assessments of the approximate dose incurred and the physiological status of the affected people. Subsequent urgent actions in this phase include: personal decontamination, sheltering, iodine prophylaxis (if radioiodines are involved), and temporary evacuation. In the recovery phase, definitive relocation and resettlement may be needed in extreme cases. Each of these countermeasures has a degree of associated penalties, and typically would provide the most benefit if the reduction of the avertable dose for the affected population was around the levels shown in Table 3.

Table 3. Recommended avertable doses for undertaking countermeasures

Countermeasure	Avertable dose (for which the countermeasure is generically optimised)
Sheltering	∼10mSv in 2 days (of effective dose)
Temporary evacuation	∼50mSv in 1 week (of effective dose)
Iodine prophylaxis (if radioiodine is present)	∼100mSv (of equivalent dose to the thyroid)
Relocation	∼1000mSv or ∼100mSv first year (of effective dose)

(k) The recovery phase may require restoration and clean up, the safe management of the radioactive waste remaining from these operations, management of corpses containing significant amounts of radioactive substances, and dealing with long-term prolonged exposure situations caused by remaining radioactive residues. In the latter case, the recommended generic criteria for justifying intervention with radiation protection measures are shown in Table 4.

Table 4. Recommended generic criteria for intervention in prolonged exposure situations

Intervention	Criteria (existing annual effective dose, mSv/year)
Almost always justifiable	Towards 100
May be justifiable	≳10
Unlikely to be justifiable	≲10

Source: ICRP (1999, Fig. 6).

(l) The quantitative recommendations given in Table 3, Table 4 cannot always be used directly as quantities such as equivalent dose and effective dose are not directly measurable. They should be used as the basis for developing (at the planning stage) operational intervention levels expressed in directly measurable quantities. The recommended guidance is based solely on radiological protection considerations and should be seen purely as a decision-aiding tool aimed at helping the competent authorities to prepare for the aftermath of a radiological attack. The guidance is expected to serve as input to a final, and usually wider, decision-making process that may include other societal concerns, consideration of lessons learned in the past from other events, and the participation of interested parties. Simplification of criteria and corresponding training and exercising would allow for better implementation; however, during the response to an actual event, emergency managers may need to take other factors, such as other hazards or specific conditions, into account in operational decisions.

(m) A potential consequence of a radiological attack is the radioactive contamination of goods such as water, food, and other commodities for public consumption. This possible outcome, however, is unlikely to lead to significant internal contamination of a large number of people because of the large amounts of radioactive material that would be required to reach high levels of contamination in mass-produced or -distributed supplies. While the levels of contamination of consumer goods and the resulting levels of annual effective dose could be very low, the effective control of contamination for radiation protection purposes could become amenable and warranted above certain activity concentration levels. The values in Table 5 represent the approximate levels of activity concentration in contaminated substances above which control for radiological protection purposes can be considered in case of a radiological attack. Consumer goods with activity concentration below the levels in Table 5 are excluded from the scope of the recommendations in this report.

Table 5. Recommended exclusion levels

Nuclides	Activity concentration (Bq/g)
Artificial α-emitters	0.01
Artificial β-/γ-emitters	0.1
Head of chain activity level, 238U, 232Th	1.0

(n) An intergovernmental international consensus on radiological criteria for radionuclides in commodities was recently reached under the aegis of the IAEA. National authorities may wish to take these criteria into account for deciding on control measures following a radiological attack.

(o) The process of radiological protection intervention measures in the aftermath of a radiological attack should result in a systematic and flexible approach to the response, taking into account the conditions present and invoking protective actions as warranted by the circumstances. It is helpful to understand that there are recommendations that are always applicable, others that are often applicable, and others that are only applicable in the most severe circumstances (for instance, as many potential scenarios clearly cannot induce immediate severe radiation injuries, recommendations on these effects are not always applicable). In order to prevent over reaction, it is essential that radiological protection decisions reflect the magnitude of the radiological attack.

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References 

1. ICRP, 1999. Protection of the public in situations of prolonged radiation exposure: the application of the Commission’s system of radiological protection to controllable radiation exposure due to natural sources and long-lived radioactive residues. ICRP Publication 82. Ann. ICRP 29(1/2).
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GLOSSARY

 

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Absorbed dose

The absorbed dose is defined as the average energy absorbed from radiation by a tissue, organ, or the whole body per unit mass of such tissue, organ, or the whole body (ICRP, 1991a, Paragraph S2). The special name for the unit of absorbed dose is ‘gray’ (Gy) which is equivalent to J/kg (another unit used in some countries is the ‘rad’; 100rad=1Gy).

Accident

Any unintended event, including operating errors, equipment failures, or other mishaps, the consequences or potential consequences of which are not negligible from the point of view of radiological protection.

Action level

The level of dose rate or activity concentration above which remedial actions or protective actions should be carried out in chronic exposure or emergency exposure situations.

Activation

The production of radionuclides by irradiation.

Activity

The quantity activity, A, for an amount of radionuclide in a given energy state at a given time is defined as A=dN/dt, where dN is the expectation value of the number of spontaneous nuclear transformations from the given energy state in the time interval dt. The unit of activity is the reciprocal second, termed the ‘becquerel’ (Bq).

Annual limit of intake (ALI)

The intake by inhalation, ingestion, or through the skin of a given radionuclide in a year by the reference man which would result in a committed dose equal to the relevant dose limit. The ALI is expressed in units of activity (see ICRP, 1993b, 1995a,b, 1996).

Anxiety and fear

The term ‘anxiety and fear’ includes the concepts of horror, dread, fright, alarm, trepidation, and apprehension that may be caused by the malicious use of radioactive materials.

Avertable (or averted) dose³

The dose to be saved by a protective action; i.e. the difference between the dose to be expected with the protective action and that to be expected without it is the dose saved by implementing a protective action for each conceivable pathway of exposure.

Collective dose

An expression for the total radiation dose incurred by a population, defined as the product of the number of individuals exposed to a source and their average radiation dose. The collective dose is expressed in man-sieverts (man-Sv).

Committed dose

The committed dose (absorbed dose, equivalent dose, or effective dose) is defined as the summation integral of the dose rate over time, from the time of exposure to a time that if not specified will be taken to be 50 years for adults.

Control

In the context of control over radioactive sources, the Commission uses the term ‘control’ to include checking, monitoring, and verifying the safety and security of such sources, as well as ensuring that corrective or enforcement measures are taken if the results indicate the need for them. Control over radiation sources should be commensurate with their potential for causing radiation induced health effects.

Countermeasure

An action aimed at alleviating the consequences of an accident.

Critical group

A group of members of the public that is reasonably homogeneous with respect to its exposure for a given radiation source and given exposure pathway, and is typical of individuals receiving the highest effective dose or equivalent dose (as applicable) by the given exposure pathway from the given source.

Decontamination

The removal or reduction of contamination by a physical or chemical process.

Deterministic effect

A radiation effect for which a threshold level of dose generally exists above which the severity of the effect is greater for a higher dose.

Dose

A measure of the radiation received or ‘absorbed’ by a target. The quantities termed ‘absorbed dose’, ‘organ dose’, ‘equivalent dose’, ‘effective dose’, ‘committed equivalent dose’, or ‘committed effective dose’ are used, depending on the context. The modifying terms are often omitted when they are not necessary for defining the quantity of interest (see Radiation dose, Absorbed dose, Equivalent dose, Effective dose, and Avertable dose).

Dose limit

The value of the effective dose or the equivalent dose to individuals from controlled practices that shall not be exceeded.

Effective dose

The quantity E, defined as a summation of the tissue equivalent doses, each multiplied by the appropriate tissue weighting factor

where H_T is the equivalent dose in tissue T and w_T is the tissue weighting factor for tissue T. From the definition of equivalent dose, it follows that

where w_R is the radiation weighting factor for radiation R and D_T,R is the average absorbed dose in the organ or tissue T. The unit of effective dose is J/kg, termed the ‘sievert’ (Sv).

Emergency plan

A description of the objectives, policy, and concept of operations for the response to an emergency, and of the structure, authorities, and responsibilities for a systematic, co-ordinated, and effective response.

Employer

Within the context of this document, the employer will be the legal person with recognised responsibility, commitment, and duties towards workers in the rescue operations, i.e. in his or her ‘employment’, by virtue of a mutually agreed relationship. A self-employed person is regarded as being both an employer and a worker.

Equivalent dose

The quantity H_T,R, defined as

where D_T,R is the absorbed dose delivered by radiation type R averaged over a tissue or organ T, and w_R is the radiation weighting factor for radiation type R.

When the radiation field is composed of different radiation types with different values of w_R, the equivalent dose is

The unit of equivalent dose is J/kg, termed the ‘sievert’ (Sv).

Exposure

The Commission uses the term ‘exposure’ in a generic sense to mean the process of being exposed to radiation or radionuclides, the significance of exposure being determined by the resulting radiation dose (ICRP, 1991a, Paragraph S4). Exposure is thereforethe act or condition of being subject to irradiation. Exposure can be either external (irradiation by sources outside the body) or internal (irradiation by sources inside the body). Exposure can be classified as either normal or potential exposure; either occupational, medical, or public exposure; and, in intervention situations such as those following a radiological attack, either emergency or chronic exposure. The term ‘exposure’ is also used in radiodosimetry to express the amount of ionisation produced in air by ionising radiation.

Exposure pathways

The routes by which radioactive material can reach or irradiate humans.

Improvised nuclear device (IND)

A crude weapon made using fissionable nuclear material that has been acquired illicitly and is capable of sustaining a fission chain reaction. Such a device might be entirely improvised or might be based on a military nuclear weapon. The hazard is due to the energy and radiation resulting from a nuclear chain reaction or from the decay of the products of a chain reaction.

Intake

The process of taking radionuclides into the body by inhalation, ingestion, or through the skin.

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Intervening organisation 

An organisation designated or otherwise recognised by a government as being responsible for managing or implementing any aspect of an intervention.

Intervention

Any action intended to reduce or avert exposure or the likelihood of exposure to sources that are not part of a controlled practice or which are out of control as a consequence of an accident or, within the context of this document, are involved in a radiological attack.

Intervention level

The level of avertable dose at which a specific protective action or remedial action is taken in an emergency exposure situation or a chronic exposure situation.

Investigation level

The value of a quantity such as effective dose, intake, or contamination per unit area or volume at or above which an investigation should be conducted.

Ionising radiation

For the purposes of radiation protection, radiation capable of producing ion pairs in biological material(s).

Irradiation and contamination

The concept of irradiation, either from a source or to a person, is straightforward: irradiation means the action of either emitting radiation (by a source) or incurring radiation (by a body, e.g. a person, a tissue, an organ). The concept of contamination is more subtle and prone to be misunderstood. The term is used to mean either radioactive substances on surfaces, or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirable, or the process giving rise to their presence in such places. Also used less formally to refer to a quantity, namely the activity present on a surface (or on unit area of a surface). It should be noted that the translation of the term ‘contamination’ into some other languages may introduce a connotation that is not present in English; while the English language term ‘contamination’ refers only to the presence of activity, and gives no indication of the magnitude of the hazard involved, this is not always the connotation given in other languages. A radiological attack may irradiate without contaminating (e.g. if the source used is not dispersible), or contaminate the environment without a significant irradiation of people, or contaminate people externally (e.g. on the skin) or internally (e.g. as a result of an intake of dispersed radioactive substances), and these contaminations could irradiate different parts of the body from inside, or result in a combination of all these scenarios.

Justification

In the aftermath of a radiological attack, one of the issues is to justify the introduction (or continuation) of disruptive countermeasures or what is termed ‘justification of intervention’. The Commission recommends that any proposed intervention should do more good than harm, i.e. the reduction in detriment resulting from the reduction in dose should be sufficient to justify the harm and the costs, including social costs, of the intervention.

Member of the public

In a general sense, any individual in the population except, for the purposes of this document, when subject to occupational exposure (e.g. working in rescue operations). For the purpose of verifying compliance with dose restrictions for public exposure, it is the representative individual in the relevant critical group.

Monitoring

The measurement of dose or contamination for reasons related to the assessment or control of exposure to radiation or radioactive substances, and the interpretation of the results.

Occupational exposure

All exposures of workers incurred in the course of their work, e.g. the exposure of rescuers.

Operational intervention level (OIL)

A calculated level, measured by instruments or determined by laboratory analysis, that corresponds to an intervention level or action level. OILs are typically expressed in terms of dose rates or activity of radioactive material released, time-integrated air concentrations, ground or surface concentrations, or activity concentrations of radionuclides in environmental, food, or water samples. An OIL is a type of action level that is used immediately and directly (without further assessment) to determine the appropriate protective actions on the basis of an environmental measurement.

Optimisation of protection in interventions

The form, scale, and duration of the intervention should be optimised so that the net benefit of the reduction of dose, i.e. the benefit of the reduction in radiation detriment, less the detriment associated with the intervention, should be maximised. This principle is termed ‘optimisation of protection in interventions’.

Orphan sources

The terms ‘orphan’ and ‘orphaned’ source have been used internationally to describe a radioactive source that is not under regulatory control, either because it has never been under regulatory control, or because it has been abandoned, lost, misplaced, stolen, or transferred without proper authorisation.

Projected dose

Projected dose is the dose estimated for the population at risk for each exposure pathway without taking possible protective actions into account.

Prolonged exposure situations Radioactive

residues from a malicious event may remain in the environment for a long time (e.g. years), adding to the radioactive substances that were present in the environment before the attack. These residues may contribute to prolonged exposure situations.

Protective action

An intervention intended to avoid or reduce doses to members of the public in chronic or emergency exposure situations.

Public exposure

Exposure incurred by members of the public from radiation sources, excluding any occupational or medical exposure and the normal local natural background radiation, but including exposure from authorised sources and practices and from intervention situations, e.g. the situation resulting from a radiological attack.

Radiation and radioactive

A substance is considered to be radioactive if it exhibits radioactivity. Radioactivity is the phenomenon whereby atoms undergo spontaneous random disintegration, usually accompanied by the emission of radiation (e.g. alpha, beta, gamma, or neutron radiation). There has been an imprecise use of the terms ‘radiation’ and ‘radioactive’ to qualify sources potentially amenable for malicious uses. A source of radiation exposure is not necessarily ‘radioactive’. Typical non-radioactive radiation sources are various types of electrical generators of radiation, such as x-ray apparatus and particle accelerators, which emit radiation while in operation but their emitting properties cease as soon as the electricity supply is cut. Conversely, radioactive radiation sources (or radioactive sources in short) emit radiation because they contain radioactive substances. Typical examples of radioactive sources are the sealed capsules containing radionuclides, such as ⁶⁰Co and ¹³⁷Cs, which never cease to emit radiation with decaying intensity. Of these, only those containing a significant amount of radioactive substance are relevant for malicious purposes. (The amount of radioactivity involved in a radiological attack is usually referred to as the ‘source term’.) In summary, all radiation sources, be they radioactive or non-radioactive, may be a safety concern; conversely, not all radiation sources but just those radioactive sources containing a significant amount of radioactive substance may also be a security concern in relation to potential terrorist attacks.

Radiation dose

The health significance of a radiological attack will be determined by the resulting radiation exposure of people and, specifically, by the radiation dose incurred by the individuals being irradiated. The Commission uses the term ‘radiation exposure’ in a broad sense to mean the process of being exposed to radiation or radioactive material and, specifically, it uses the term ‘radiation dose’ as a generic name expressing the amount of energy received by matter from radiation exposure (ICRP, 1991a, Paragraph S4). With different qualifiers, the term ‘dose’ gives rise to various dosimetric quantities.

Radioactive half-life

For a radionuclide, the time required for the activity to decrease, by a radioactive decay process, by half.

Radioactive residues

The Commission uses the term ‘radioactive residues’ to mean radioactive materials that have remained in the environment from early operations (including past practices) and accidents (ICRP, 1991a, Paragraph 219).

Radioactive waste

The Commission uses the term ‘radioactive waste’ to mean any (radioactive) material that will be or has been discarded, being of no further use (ICRP, 1997c, Paragraph 3).

Radioactive dispersion devices (RDDs)

The detonation of conventional explosives shrouding an ordinary radioactive source, such as those commonly used in medicine and industry, has been dubbed in the press as a ‘dirty bomb’, but may be more properly referred to as an ‘RDD’. The dispersion of radioactive material into the environment may be achieved without explosives, by opening the source container if the material is dispersible, or processing the source to make it dispersible.

Residual dose

Residual dose⁴ is the remaining dose from each pathway (projected dose minus averted dose). For long-term decisions that would usually involve prolonged exposure situations to residual doses that may remain long after the event, the relevant quantity is the annual (effective) dose, which can be presented as: the existing annual dose, i.e. the summation of the annual doses caused by all the persisting sources of prolonged exposure already existing in the human habitat where the situation occurs; the additional annual dose, i.e. the annual dose that is added to the existing annual dose as a result of the event; and/or the averted annual dose, i.e. the annual dose that is removed from the existing annual dose by the protective actions that might be taken.

Risk

A multi-attribute quantity expressing hazard, danger, or chance of harmful or injurious consequences associated with actual or potential exposures. It relates to quantities such as the probability that specific deleterious consequences may arise and the magnitude and character of such consequences.

Safety assessment

A review of the aspects of design and operation of the intervention following a radiological attack that are relevant to the radiological protection of people, including analysis of the provisions for safety and protection established, and the analysis of risks associated with the event.

Security vis-à-vis safety

Although the concept of security of radiation sources is not new in radiation safety standards, it has acquired new dimensions following international concerns on potential nuclear terrorism. The use of the term ‘security’ has been widely confused with the wider concept of safety, the confusion being aggravated by linguistic problems (in many major languages, the concepts of safety and security are expressed with the same word). In the Commission’s parlance, the safety of a source denotes the assembly of administrative, technical, and managerial features aimed at diminishing the likelihood of people incurring radiation harm as a result of radiation exposure from such a source. In contrast, the security of a source refers to features aimed at preventing any unauthorised possession of, and actions with, the source, by ensuring that control over it is not relinquished or improperly acquired. Source security is a necessary, but not sufficient, subsidiary condition for source safety.

Source

The Commission uses the term ‘source’ to indicate what may cause radiation exposure. Sources range from nuclear installations and other nuclear facilities usually holding huge inventories of radioactive fission and activation products, to simple sealed sources of radioactive materials. The term is also used more generally to indicate the cause of exposure to radiation or to radionuclides in radioactive substances, and not necessarily an individual physical source of radiation. For instance, if radioactive materials are released from an installation to the environment, the installation as a whole may be regarded as a source; if they are already dispersed in the environment, the portion of them to which people are exposed may be considered a source.

Source term: radioactivity

Except for INDs, which require separate treatment, the strength of a radiological attack is defined by the amount of radioactive material involved in the event (and its radioisotopic composition), which is termed the ‘source term’. The principal quantity defining the source term is the activity (hereinafter referred to as radioactivity)⁵ of the radioactive substances involved in the event for each of the radionuclides involved. This describes how much radiation the dispersed substances are emitting. The unit of radioactivity is the reciprocal second, which is termed ‘becquerel’ (Bq) [although another unit of radioactivity used in some countries is the curie (Ci), which is defined as the radioactivity content of 1g of radium]. One becquerel is an extremely small amount of radioactive substance as it is much smaller than a billionth of 1Ci (1Ci=3.7×10¹⁰Bq). In the event of the explosion of an IND, in addition to radiation emitted by the radioactivity created in the event, there may be a significant flux of neutrons that will occur within the first minute after the explosion.

Special fissionable materials

Special fissionable material includes: plutonium, except that with isotopic concentration exceeding 80% in ²³⁸Pu, ²³³U, and uranium enriched in the isotope 235 or 233.

Stochastic effects of radiation

Radiation effects, generally occurring without a threshold level of dose, whose probability is proportional to the dose and whose severity is independent of the dose.

Supervised area

Any area not designated as a controlled area but which is kept under review for occupational exposure conditions, even though specific protective measures and safety provisions are not normally needed.

Worker

Any person who works, whether full time, part time or temporarily, for an employer and who has recognised rights and duties in relation to occupational radiation protection. A self-employed person is regarded as having the duties of both an employer and a worker. Rescuers are regarded as workers.

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1. Introduction 

1.1. Background 

(1) Over the years, the Commission’s recommendations (ICRP, 1959, ICRP, 1964, ICRP, 1966, ICRP, 1977, ICRP, 1991a) have presumed that, as a precondition for proper radiological protection, sources of radiation exposure have to be subject to proper security measures. This presumption is reflected in the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources (IAEA, 1996a), usually referred to as the ‘BSS’, which follow ICRP recommendations and require that the control over sources shall not be relinquished under any circumstances. Source security is a necessary, although not sufficient, condition to ensure source safety. If a source is not secure, it is not safe; conversely, sources that are secure are not necessarily safe.

(2) Secured sources can, and have, become unsecured through a variety of circumstances. Historically, in the most common cases, control over the source was relinquished inadvertently, and then the source was misused, without any premeditated malicious intent. In other cases, many sources have been found to be orphaned of any control and were therefore completely unsecured. A relatively large number of radiological accidents have occurred because of these unintentional breaches in source security or because an orphan source was inadvertently found. The detailed causes and consequences of some of these accidents have been reported internationally (IAEA, 1988a, IAEA, 1996b, IAEA, 1998a, IAEA, 1998b, IAEA, 1998c, IAEA, 2000a, IAEA, 2000b, IAEA, 2000c, IAEA, 2002a, IAEA, 2002b).

(3) These cases of inadvertent breaches of source security have provided an indication of what might occur if radioactive materials were used intentionally to create harm. There is the potential for premeditated criminal breaches in source security that may eventually lead to the malicious use of radioactive materials. An example of a radiological attack based on this type of scenario could be the deliberate dispersion of the radioactive content of a source in a public area. Such an event has the potential for exposing people to radiation and causing significant environmental contamination, which would require specific radiological protection measures. Before the events of 11 September 2001, information on security of radioactive sources had been publised internationally (IAEA, 1998c, IAEA, 1999a, IAEA, 2001c). Following these events, the issue has been re-addressed both at international level (IAEA, 2003c) and also by various national organisations (e.g. HPS, 2004, NCRP, 2001), particularly regarding the possibility of malicious uses of unsecured radioactive sources. An international Code of Conduct on Safety and Security of Radioactive Sources has been established recently (IAEA, 2001b, IAEA, 2004a), with a clearly defined scope of ‘dangerous’ sources (IAEA, 2003a, IAEA, 2003b). More recently, international agreement has been reached on guidance for export/import of sources (IAEA, 2004e) in order to implement relevant requisites in the Code. The Commission expects that adherence to the Code’s requirements will strengthen the necessary control of radioactive sources – a prerequisite to ensure that they are properly secured.

(4) There are a number of reasons why radiation is of unique concern in relation to malicious events. On the negative side, radiation is perceived as a mysterious pollutant, and past experience with radiation emergencies has shown that there are problems in dealing with this perception. The public have, in general, exaggerated fears because radiation is invisible and odourless, and its effects may only be apparent hours, days, weeks, or even many years after exposure. Radiological attacks are more likely than other malicious events to give rise to psychological problems among members of the public, public officials, and professionals in other fields because of the fear of radiation and a misunderstanding of its consequences. The perceived risk is a major contributor to the anxiety and fear that may be induced by a malicious act – an extra dimension presenting additional challenges to those who will have to manage the health consequences of such an event. There will be difficulties in responding to a radiological attack because those who handle the situation at an early stage, if not appropriately trained, will share much of the anxiety and fear about radiation, and they will probably have little experience in dealing with such an emergency.

(5) Relatively low levels of radiation exposure, such as those that will likely remain after a radiological attack, are often mistakenly viewed as a substantial hazard, and this is the main element in the creation of anxiety and fear. Contrary to public perception, radiation is actually a weak carcinogen. At low levels of exposure, the health risks attributable to radiation, such as the risk of developing cancer, are very low – so low that any potential effect is, in fact, undetectable by epidemiological techniques. Radiation protection professionals should, however, do whatever they reasonably can to constrain unjustified radiation exposure of people, because the prevalent scientific opinion is that for protection purposes, a small but finite risk of deleterious effects should be attributed to radiation exposure above background levels, even at low levels. Unfortunately, justifiable radiation protection efforts without proper communication with the public can themselves become a contributor to anxiety and fear as people can misinterpret them as an indication that they are subject to a high risk.

(6) On the positive side, in comparison with biological or chemical attacks, the area over which radioactive contamination occurs can be readily delineated if appropriate radiation measurement instruments are available (with the possible exception of contamination due to some α-emitting radioisotopes). Moreover, radiation is one of the most studied agents in toxicology and medicine, including its carcinogenic potential, and therefore many sources of information on the health effects of radiation are available. As a result of these studies, sound criteria for conventional radiological emergencies have already been developed, which are relevant and can be applied in the event of a radiological attack. Furthermore, it is generally recognised that there would be far fewer fatalities following a radiological attack, in contrast to the number of immediate fatalities that could be caused by biological or chemical agents, or simply by a large explosive blast.

1.2. Aim of the report 

(7) The main aim of this report is to provide radiological protection recommendations for protecting people’s health in the aftermath of a radiological attack. These recommendations are based on conceivable scenarios of specific radiological attacks aimed at exposing people to radiation, or contaminating the environment, creating anxiety and fear, and resulting in disruption. The report does not address the means by which the source of radiation was obtained by the attackers.

(8) The Commission notes that whether or not an ‘attack’ is the trigger of a situation of radiological concern, the aftermath of either intended or unintended events of this type are, in fact, very similar: namely, the potential for unexpected exposure of people to radiation. The intent that caused the radiological condition may be different, but the outcome and the necessary response actions are essentially the same. However, there are differences between an emergency that may arise from an accident and those associated with a radiological attack. These differences are described in the report. If a radiological attack were to occur, authorities and radiological protection experts could be faced with a situation where radiation and/or radioactive material are in a place where it was not expected or explicitly planned to be. Whatever the scenario, the final objectives should be to protect people in unpredictable exposure situations, to minimise the impact, and to quickly restore the situation to normal. When this fact is realised, the response must essentially:

(9) Capabilities need to be in place to ensure the effective performance of these response actions, and relevant international requirements and guidance have been established (IAEA, 2002c, IAEA, 2003b). These capabilities will include those that are generic for all types of emergencies (e.g. continuously available emergency contact points, command and control, public communication arrangements, initial all-hazards assessment) and those that are specific to radiological emergencies (e.g. radiological assessment, monitoring, and protection capabilities) (IAEA, 1997c, IAEA, 1999b, IAEA, 2000d). These capabilities will need to be applied in a systematic and flexible manner to perform the response functions effectively according to the event scenario.

(10) It is to be noted that the recommendations in the report are mainly based on the scientific assessment of the health risks associated with radiation exposure that may arise in the aftermath of certain scenarios involving radiological attacks. However, some members of the public and sometimes their political representatives may have alternative views on the radiation risks attributable to such situations. This usually results in differently perceived needs for response and a different level of protection. The desired level of protection may be higher than that for other exposure situations. For instance, the risk attributable to living in areas with typically elevated natural radiation exposures are usually ignored by society, while relatively minor exposures to artificial radioactive residues remaining in the environment are a cause of concern and sometimes prompt unnecessary protective actions. This reality of social and political attributes, generally unrelated to radiological protection, will influence the final decision on the level of protection following a radiological attack.

(11) Therefore, the Commission emphasises that this report should be viewed as providing decision-aiding recommendations based principally on scientific considerations of radiological protection, rather than an automatic formula for making decisions. The recommendations in the report, therefore, provide supplemental guidance and input to a wider decision-making process that may include: other societal concerns; other hazards that may be present; consideration of lessons learned in the past from other events; and the participation of relevant stakeholders. The process of planning for radiological attacks should result in a systematic, yet flexible, approach to the response, taking the conditions present into account, and invoking protective actions as warranted by the circumstances.

1.3. Intended audience 

(12) The Commission intends this report to be of help to responsible officials, regulatory bodies, and advisory agencies with competence in emergency response – in particular, those agencies dealing with possible radiological attacks and their aftermath at local, regional, national, and international level. The report provides guidance to these bodies on the fundamental principles on which appropriate intervention with protective actions may be undertaken in response to such an event. Different conditions are likely to apply in different countries, and the Commission, therefore, wishes to emphasise that the report should not be viewed as a universal text on radiological protection in the event of a radiological attack.

(13) The Commission recognises that one of the problems to be faced in relation to the types of situations discussed in this report is the lack of a common understanding on the basic issues among scientists, decision makers, the media, and the public at large. Unfortunately, since the events of 11 September 2001, reactions of many people have created some confusion in the comprehension of the security concerns associated with radioactive substances. For instance, the basic concepts of radiation source vis-à-vis radioactive source and irradiation vis-à-vis contamination are widely confused, as are source safety vis-à-vis source security.

(14) The concepts, quantities, and units used in radiological protection are also often misunderstood. Confused communication, mainly caused by the loose use of terminology, sometimes exacerbated by difficulties in translation, has contributed to increased public anxiety on this issue. As the report may also be of interest to people other than radiation protection professionals, such as security specialists and non-radiation experts involved in decision-making processes relating to emergency situations, and because of the prevailing misunderstandings on the topic, the report is supplemented with information intended to help the reader to understand the Commission’s terminology and policies in the context of radiological emergencies. Relevant complementary information is provided in the Glossary.

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2. Characterising the situation 

2.1. Potential scenarios 

(15) Scenarios for the malicious intent of causing radiation exposure are characterised in terms of their threat. To respond effectively, it is necessary to recognise and anticipate the type of threat that might trigger such an event. Methodologies for categorising threats have been developed internationally, for instance, in the International Handbook on the Physical Protection of Nuclear Materials and Facilities (IAEA, 2002e), but they relate specifically to nuclear materials and facilities rather than to other radioactive materials or specifically to radiation sources. However, these methodologies could generally be applied to radiological attacks. A more important point is that the type and amount of radioactive material has a greater impact on the response needed, rather than how the source was obtained. This issue is reflected in more generalised emergency planning categorisation schemes expounded in international requirements (IAEA, 1997b, IAEA, 2002c, IAEA, 2003b).

(16) It should be recognised that a radiological attack could have many initiators and that it is impossible to characterise all the possible scenarios. Some conceivable scenarios are described in Annex A and summarised below:

(17) As described above, the possible scenarios vary widely in scale, genesis, and likelihood but they are rather similar in their ultimate consequence, namely unexpected situations of uncontrolled public radiation exposure and possible radioactive contamination of the environment. While no single event can be used as a basis for development of response plans, a number of common features can be recognised as follows:

2.2. Special features 

(18) As is the case for radiological accidents, the radiation emergency arising from a radiological attack will usually occur unexpectedly. The response to protect people, clean up the area, and return to normality would, in principle, be the same for both situations. However, compared with an emergency at a regulated installation, that resulting from a radiological attack would present a number of special features.

(19) An emergency resulting from a radiological attack would most likely occur in a public area where there is no expectation of radiation or radioactive material and where there may be limited preparedness for responding with radiological protection measures. The area is most likely to be an urban location, where emergency services are usually more substantial and concentrated. However, for these locations, the dispersion conditions commonly used for emergencies in nuclear facilities may not be applicable. In this sense, the planning and preparedness are likely to differ from those usually associated with the radiological scenarios that may result from nuclear accidents.

(20) The public perception of a radiological attack will be different from that of some radiological accidents, even if the radiation impacts were objectively similar. The feeling of the public might be that a radiological attack poses the greater risk. This in turn may cause public alarm far beyond the normal reaction to the actual hazards, and it may become increasingly difficult to reassure the public or to manage the consequences effectively. There will, therefore, be a need to keep the media and public informed with clear and accurate information, and the mechanism for doing so needs to be addressed at the planning stage.

(21) The method to deduce the characteristics of the radioactive material is one of the most important differences between conventional radiological emergency response planning and the planning required for responding to RDD and IND events. In the former, reasonable assumptions can be made about the radioactive material involved in the situation as the types of sources, facilities, material inventory, etc. are usually known a priori. In the case of a radiological attack and indeed for chemical and biological attacks, it is very unlikely that there will be any information available in the early response phase upon which to characterise the source term, although the range of credible source terms can be anticipated somewhat. Estimates of source term, however, usually have less practical bearing on the management of the response than the use of quantified operational criteria established as part of the planning process and, critically, identifying the radionuclide(s) involved. Precise information to evaluate a source term will only be known some time after the event as a result of environmental monitoring, sampling, and analysis conducted throughout the emergency response (IAEA, 1999b). The degree of certainty about the magnitude of the source term will improve as additional measurement capability becomes available. As the results from the measurements are compiled, crude estimates of the source term can be made, working backwards to start estimating how much radioactive material may have been involved.

(22) An even more difficult situation presents itself when there is a covert radiological situation, i.e. the presence of the material is not apparent until someone happens to measure it or a person presents with a radiation injury. Then the challenge is to track back from detection to determine where the material is, how much there was, who else might be involved, and how to make recommendations for protection. A scenario of particular concern to emergency response planners is an attack involving chemical, biological, or radioactive material being covertly dispersed in a congested public place, such as a subway system during the rush hour. In a very short period of time, and long before any one is aware of the situation, small quantities of material could be all over a large city. Although the quantity of radioactive material in any one location would not be at all likely to cause adverse health effects, the public distress and magnitude of the response might be significant as the forensic investigation attempted to understand the extent and magnitude of the impacted areas. While the reaction of the public to a given event has not been fully investigated, the evidence of public reaction to emergencies in the past seems to indicate that they do not panic, and it appears that the possibility of tremendous panic is not substantiated by history.

(23) An important facet of human behaviour that must be recognised as a distinct characteristic in response to any type of event or accident is that the public are likely to rush to the scene to try and assist with rescue efforts. Since the presence of radioactive material is not likely to be known in these first moments, there will be many individuals who will quickly be in need of survey, treatment, etc. Furthermore, without proper controls, it may be difficult to assess and control the spread of contamination as people enter or exit the scene of the event.

(24) Many law-enforcement agencies, federal agencies, security forces, and emergency services will have intelligence and contingency plans in place to deal with various types of events. These plans are likely to cater for a wide spectrum of events including bomb threats, extortion demands, aircraft hijacking, and hostage taking. It is likely that these plans will have been reviewed and updated in the light of recent malicious acts.

(25) In cases where a heightened level of threat may exist, e.g. during major events such as sporting occasions, or in areas that are particularly vulnerable to malicious acts, such as subway systems, the threat level may justify the installation of instruments to detect the possible ingress of radioactive material or devices. Such large-scale deployment of detection devices would be expensive and onerous, so its need must obviously be commensurate with the level of risk. Another option, possibly less costly, is to equip security personnel with electronic direct reading of radiation exposure, although this method would not be effective for the detection of alpha-emitters such as ²³⁹Pu.

(26) Furthermore, graded systems for communicating assessments of threat may be introduced that allow first responders to take additional precautions when responding to events where a heightened level of threat of radiological attack may exist in a given area. For example, if a fire emergency at an apparently ordinary building is suspected to have been caused by a terrorist attack, fire fighters may be required to monitor the scene for the presence of deliberately introduced radioactive materials; conversely, if there is no question of a terrorist attack (e.g. because of a low assessed threat level), fire fighters would not normally monitor the scene. Systems for communicating threat levels may include generic coding systems at national or regional level and/or of specific buildings or areas identified as potential targets and therefore at higher threat levels.

(27) Another important difference between a conventional radiological accident and a radiological attack is that after the latter, local police will always be involved and may need to declare the area a crime scene in order to begin forensic investigations. If it is confirmed that the event was cause by a deliberate act, the emergency response and forensic investigation will rapidly escalate from local police to regional and national law-enforcement officials. Unfortunately, the objectives of forensic investigations and evidence preservation often conflict with those of radiological protection. Specifically, the very material needed to try to estimate the source term and make protective action recommendations may be determined to be forensic evidence that must be tightly controlled. This possibility could have two unfortunate results: first, it could slow down the process of developing critical protective action recommendations because the law-enforcement officials would have to approve the release of the information to the decision makers; and second, there might be a conflict with communicating the public health information and recommendations because law-enforcement officials may be reluctant to release any information that might be considered forensic evidence or hinder the ongoing investigation.

(28) Therefore, one of the most critical preplanning issues is how the various law-enforcement and investigation groups will work collaboratively with the radiological protection groups so that use of critical data is effectively accomplished. This is also essential to ensure that the critical information is available to assessment groups so that recommendations can be made. Other obviously critical issues are: who is in charge of the information; how the information flows; and how law enforcement interfaces with radiological protection. An integrated emergency response organisation, such as an ‘incident command system’ (ICS) (IAEA, 2003b) that is used in many countries, provides for rapid integration, co-ordination, and expansion of response for all types of emergencies. It is based on having common terminology, modular organisation, integrated communications, unified command structure, consolidated emergency plans, designated emergency facilities, and comprehensive resource management. Law enforcement issues need to be integrated within such a framework.

(29) An emergency resulting from a radiological attack poses a series of distinct challenges requiring difficult decisions by the responding authorities, as they may offer choices between sets of unwelcome or unattractive alternatives. An unrealised threat poses the most fundamental dilemma, as the threat may never become a reality and may never become known to the general public. On the one hand, authorities may wish to demonstrate due diligence in confronting and dealing with a threat, while on the other hand, they may experience considerable difficulty in committing extensive resources to combat a threat that may never materialise.

2.3. Planning 

(30) In developing an emergency preparedness programme, the following infrastructure elements are internationally required to be considered at local and national level: authority; organisation; co-ordination; plans and procedures; logistic support and facilities; training drills and exercises; and quality assurance (IAEA, 1997b, IAEA, 2002c, IAEA, 2003b). Among many other elements, this will include the designation of a continuously available contact point for receiving and acting on information, an emergency management organisation (such as the ICS), arrangements for technical information management, and public communication arrangements. More specifically, planning for attacks involving radioactive material needs to ensure that: first responders are trained and have the proper instruments to identify the presence of radiation; radiological specialists are readily available to respond promptly to suspected hazards to advise first responders’ local authorities and others; and robust operational criteria have been established in advance for taking protective measures under various scenarios. Given credible indication that an attack has occurred, it may be prudent to assume that such an attack does involve radiological, chemical, and/or biological hazards until proven otherwise. This dictates the adoption of an all-hazard approach to emergency response based on wide-ranging precautions combined with a prompt capability to identify all hazards present. This approach must consider the need for a subjective assessment of the likelihood of the event and of the ‘radiation-related’ anxiety and fear that will probably be associated with it.

(31) Current international guidance emphasises the need for all-hazard planning, where radiological emergency plans are well integrated with arrangements and resources in place for conventional emergencies. The nature of radiological attacks adds a new dimension to this concept of all-hazard planning. It is very difficult to prejudge what type of toxic compounds (nuclear, chemical, or biological) or weapons (classical or nuclear) will be used. This is further complicated by the possibility of multiple attacks and the presence of simultaneous hazards, e.g. chemical, biological, and radiological, being involved. Multiple simultaneous attacks at different locations would place an additional strain on the response capabilities of a country. Moreover, a unique feature to be considered is the possibility that there may be a suicidal approach for a radiological attack. Nevertheless, the ICS model can be applied to organising an effective co-ordinated response.

(32) Planning for emergencies resulting from a radiological attack, and managing unexpected disasters in general, share similar concerns. Disasters are typically handled by civil defence operations and these can provide a useful framework for dealing with a range of emergencies. Dealing with the aftermath of a radiological attack may, however, differ in some respects from dealing with a radiological emergency arising from an accident in a regulated facility, due to the difficulty in planning for random acts that may occur anywhere in a wide range of circumstances. The local authorities at a place where a radiological attack occurs may not have an emergency response plan to deal specifically with radiological emergencies, or have any experience in dealing with such emergencies. Moreover, they may not have immediate access to radiation detection equipment or other resources necessary to protect response personnel and the public. It is necessary to develop at least a basic capability for such events.

(33) Medical preparedness for a radiological attack is, in many respects, similar to the preparation needed to respond to other attacks that involve chemical or biological materials. The first section of Annex B describes a number of issues related to medical emergency planning vis-à-vis the various possible threats of radiological attacks. The Commission intends to develop particular guidelines to assist the medical profession in the preparation for responding to radiological attacks.

(34) If a radiological attack has been threatened, the situation is not unlike the anticipatory preparations that may be arranged for chemical and biological attacks. Depending on the planning and arrangements made by local authorities, medical facilities may receive a notice that some type of threat has been made so that they can be prepared should the event actually occur.

(35) An important improvement would be for local medical service personnel to be able to recognise overexposed patients, even if they are not able to deal with their long-term medical care. In the event that individuals are overexposed, they could be treated at a specialised regional centre rather than locally. In fact, centres with specialised burn and haematological units are usually fairly well equipped to handle radiation overexposure cases. The allocation of scarce resources to develop a local or national radiation medical centre to specifically deal with a remote contingency may not be justified. The medical treatment of patients does not, generally, need to be hampered by the hazards of the contamination, provided that simple precautions – not radically different from those normally employed in sterile work – are taken to reduce the spread of contamination.

(36) One characteristic that will affect medical planning is the fact that the number of potentially affected people is unknown. Since radiological attacks may occur anywhere, planning should be part of national guidelines for emergency medical services and hospitals, including smaller, general care facilities (IAEA, 2004c). The guidelines should ensure that, throughout the country, medical personnel have a user-friendly reference guide on the basic measures required to deal with the urgent care of potentially overexposed and/or contaminated casualties.

(37) Psychological impacts are likely to pose a significant challenge, and these issues need to be addressed in planning the response to a radiological attack. Following a radiological attack, healthcare providers’ offices, medical clinics, and hospitals will be deluged with symptomatic and asymptomatic people seeking evaluation, care, and guidance for possible radiation exposure or contamination. A well-organised, effective medical response will instil hope and confidence, reduce anxiety, and support the continuity of basic community functions. Healthcare providers will need appropriate training in advance, as they may also be subject to fear and anxiety. Ensuring clear communications and the availability of advance information are key elements in the successful preparation for managing the consequences of a radiological attack. Advance planning should also recognise the necessity for dealing with post-traumatic stress, and the concerns that may be engendered for decades following the event.

(38) Responding to the mental health needs of the community as a whole raises many challenges of preparation. In addition to a dedicated area, staffing, contact registry, and intensified primary care follow-up efforts, intervention for people concerned with unexplained symptoms should involve brochures, fact sheets, and literature about self-management approaches to medically unexplained symptoms. The use of an on-site advocate who can help people with unexplained symptoms to overcome perceived barriers to care helps to defuse people’s notions that ‘no one cares’ and affords clinicians a way to reduce the pressure to meet these people’s needs.

(39) An important lesson to be learned from emergency response exercises is that the results of early monitoring and assessment activities differ widely because of different assumptions in the size of the source term. Therefore, exercises on radiological attacks often do not give decision makers a true understanding of the difficulties that would be faced in a real event. The scenario is presumed, and the radiological assessment team can quickly generate conjectural recommendations that will find little parallelism with what will really happen in practice. The likely reality is that the only information known is that there was an explosion, that radiation detectors are alarming, and that the wind is blowing in a given direction, and yet government officials and news reporters will demand immediate answers to questions, such as should people evacuate and how far away should they move. The lack of early information will, in fact, have a significant impact on the extent of what might be recommended for protective actions. In order to maintain confidence and reduce confusion, it is considered appropriate to establish a ‘standard’ response strategy that is triggered by key observable parameters and criteria, to train all personnel, including political decision makers, to implement the plan efficiently and effectively, and then adjust the details of the strategy as better assessments of the circumstances become available. Despite the above reservations, the Commission recommends that exercises on plausible scenarios of radiological attacks should be performed, that political decision makers should participate, and that limited drills should be performed on specific response functions to ensure that detailed issues are covered adequately.

2.4. Exposure 

(40) Radiological attacks are likely to result in dispersion of radioactive substances. ‘Radioactivity’ is the term used to describe the phenomenon of radiation emission, which is quantified in terms of the activity of the emitting source. Activity is a quantity assessed in units termed ‘becquerels’ (Bq) [although, in the past, the term ‘curie’ (Ci) was – and still is – widely used]. One becquerel represents an extremely small amount of activity (conversely, 1 Ci represents a significant amount of activity, as it equates to 37 thousand million Bq). Both individual members of the public and rescuers coming to their help may be exposed to the radiation emitted by the radioactive substances. The types of radiation expected to be emitted from an RDD include: alpha particles, which have high-linear-energy transfer (LET) properties but low penetrability into tissue (and therefore are only relevant if the emitting substance is incorporated into the body); beta particles, which are able to penetrate relatively thin tissues, such as the skin; and, fundamentally, gamma radiation, which can penetrate the full body. In case of INDs, neutrons will also contribute to the radiation field.

(41) Depending on the amount of radiation exposure, whether it is from outside the body (external) or from uptake of radioactive substances (inhalation, ingestion, or uptake through wounds or skin) (internal), various health effects can occur. The amount of radiation exposure is measured in terms of the radiation dose incurred by the affected people. The relevant quantity is termed ‘absorbed dose’ and is assessed in units called ‘grays’ (in the past, the unit ‘rad’ was used). However, different types of radiation have different effectiveness to induce damage. Besides, different organs and tissues have different sensitivities to radiation exposure. Therefore, the absorbed dose has to be weighted to take account of these differences. The respective weighting factors are termed ‘radiation weighting factors’, w_R, and ‘tissue weighting factors’, w_T; their values are recommended by the Commission (ICRP, 1991a). The quantities resulting from the absorbed dose weighting for the effectiveness of the different radiation types and the radiation sensitivity of different organs and tissues are termed ‘equivalent dose’ and ‘effective dose’, respectively, and are measured in a unit termed ‘sieverts’ (Sv) (in the past, the unit ‘rem’ was used). The equivalent dose is used to express tissue and organ doses, and the effective dose is used for assessing the whole body implications. The following scheme provides a visual relation among the relevant quantities, namely: the activity, A; the absorbed dose in a tissue, D_T; the equivalent dose in that tissue, H_T, that results from weighting the absorbed dose by the radiation weighting factors, w_R; and, finally, the effective dose, E, that results from weighting the equivalent dose by the tissue weighting factors, w_T, and summing up over all tissues.

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(42) It should be noted, however, that the equivalent dose and the effective dose can only be employed for ‘normal’ radiation protection purposes, i.e. for situations causing relatively low doses that may merely induce low probability and delayed health effects (stochastic effects). Formally, neither the equivalent dose nor the effective dose should be used to quantify radiation exposure to the high doses that are able to cause serious and early pathological effects. Moreover, for radiation with high-LET properties (such as alpha radiation), the relative biological effectiveness varies depending upon the type of radiation injury, the organ irradiated, and the time over which the irradiation is delivered, which will require separate considerations.

(43) An additional difficulty is that radiation detection instruments cannot measure the dosimetric quantities relating to the human body, such as the equivalent dose and the effective dose. These can only be estimated from directly measurable quantities of external exposure, which are termed ‘operational quantities’. The operational quantities are recommended by the International Commission on Radiation Units and Measurements (ICRU). These have been introduced by the Commission in Publication 60 (ICRP, 1991a, Paragraph 138), and adopted in international standards for checking compliance (IAEA, 1996a). There are four operational quantities of particular interest in the measurement of radiation fields for radiological protection purposes. These are: the ambient dose equivalent, H*(d); the directional dose equivalent, H′(d); the individual dose equivalent, penetrating, H_p(d); and the individual dose equivalent, superficial, H_s(d). They are based on the concept of the dose equivalent at a point and not on the concept of equivalent dose, and are used for calibrating measuring instrumentation purposes of radiation protection.

(44) Given the above difficulties, for reasons of simplification and readability, this report will only use equivalent dose and effective dose to quantify radiation exposure at both low and high levels. For the same reasons, the report will use a submultiple of the sievert, termed ‘millisievert’ (mSv) as the unit of these quantities, which is equal to a thousandth of a sievert (1mSv=100 thousandths of 1 rem or 100 millirem). In order to put these amounts into perspective, it should be noted that the level of effective dose that is unavoidably incurred from natural radiation exposure by people living for 1 year in an area of low background radiation is approximately 1mSv (the global average effective dose from natural background radiation is 2.4mSv/year, and high background levels are typically approximately 10mSv/year; in a few areas of the world, the background levels can be even higher than 100mSv/year).

(45) The potential radiation exposure can vary considerably in magnitude, depending upon factors such as the particular type and nature of the attack, the total amount of radioactive material and the different radionuclides involved, the energy with which they are dispersed into the environment, the nature of the surrounding environment, and the mechanisms of radionuclide dispersion and transfer. In most cases, there will be a limited set of exposure routes to consider. When planning protective actions, it is important to identify the possible exposure pathways and to evaluate their relative importance. These aspects need to be considered in the development of response plans, operational criteria, ‘standard’ response strategies, and detailed implementation of protective actions. Different protective actions may need to be implemented to avoid or reduce the radiation exposure, depending particularly upon the pathway by which exposure is liable to occur, as well as upon the body organs or tissues that are likely to be irradiated and the dose that is projected to be received.

(46) People directly involved in a radiological attack will include members of the public in the affected areas and also rescuers responding to the event. There are two main mechanisms that may lead to these people being exposed to radiation: external exposure, that is radiation received from a source outside the body (including radioactive material deposited on the skin); and internal exposure received from radioactive material that is inhaled, ingested, absorbed through intact skin and wounds, or introduced into tissues as fragments which are either radioactive or contain radioactive contamination. The overall risk to the individual person represents the summation of effects of external and internal exposures.

(47) Pathways of external radiation exposure include:

(48) Pathways of internal radiation exposure include:

(49) The ultimate consequences of the event will also be influenced by the particular characteristics of the affected environment. For example, the external radiation dose can vary considerably between urban (Kelly, 2002) and rural environments, the type and amount of deposition on various surfaces, and the living habits of the exposed population. Seasonal variations in environmental conditions can also influence the levels of contamination in local products in areas where deposition of radionuclides has occurred.

2.5. Initial reaction 

(50) Initial reaction to a radiological attack will depend upon the initiating event, e.g. whether it is an explosion or, in extreme cases, an IND. Following the first response, there will be a number of evolving response phases and different types of interventions involving specific protective actions, such as: control of access to the public; sheltering; evacuation; administration of prophylactics measures; decontamination of people, land and property; relocation; control of water, foods and other commodities of public consumption; livestock and animal protection; waste management and control; refinement of access control; release of personal property, land and buildings; re-entry of non-emergency workforce; and re-inhabitation of homes. Some of these protective actions will be discussed in detail in Chapter 5.

(51) Many of the postulated scenarios are for some type of explosive initiating event, which in fact are the easier events to respond to because the initiation is obvious. Many countries equip first responders, such as fire fighters, with some type of radiation detection capability onboard their vehicles. These first responders will usually react in the same way as they would for any other type of explosion and situations potentially involving hazardous material, namely establishing a perimeter for access control, taking life-saving measures, and aiming to control the situation. For most types of situations, the standoff distance that fire brigades typically establish when responding to an explosion is also adequate when radioactive material is involved. When the results from radiological surveys are available, the perimeter can be adjusted as needed.

(52) As described before, an IND is a nuclear weapon originating from diverted special nuclear material that produces a nuclear explosion. An IND can have a wide range of nuclear yields depending upon the degree of sophistication in design. A very simple device may blow itself apart giving a very small explosion and yield – rather like a criticality accident. If the design is such as to promote the nuclear explosive power, the yield can be increased so as to be not dissimilar to the atomic bombs at Hiroshima and Nagasaki. The nuclear yield achieved by such an IND produces extreme heat, powerful shockwaves, and prompt radiation that would be acutely lethal for a significant distance. If nuclear yield is not achieved, the result would likely resemble an RDD in which fissile weapons material was utilised.

(53) Given this wide range of yields, and therefore potential impacts on the public, the Commission has not dealt specifically with the radiological consequences of an IND. The Commission, however, wishes to stress that the blast effects are likely to be the most serious aspect although, potentially, large areas may become contaminated as the plume of radioactive materials (fallout) disperses. Although the scale may be larger, the basic concepts in the radiological response to such an event are no different from those for other radiological attacks; namely, the need to establish control boundaries, to qualify the levels of contamination, treat people, and take action to protect the rest of the population.

2.6. Response phases 

(54) The response to an emergency, including those that involve a radiological attack, will generally take place in three distinct phases, namely rescue, recovery, and restoration (some emergency planners use the terms ‘early’, ‘intermediate’, and ‘long term’ in describing these phases of response). Their characteristics will be briefly described hereinafter. The recommended protective actions and guidelines will be addressed in the following chapters.

(55) The rescue phase must recognise that the immediate aftermath of an incident is likely to be chaotic, and the emergency services’ initial efforts must focus on bringing the scene under a measure of control, which will allow rescue efforts to proceed in an orderly manner. The priority actions are to save life and to evacuate injured people, which may proceed under hazardous and high-risk conditions. The lead agency at this stage is likely to be the local fire service, which is best equipped and experienced to manage rescue operations, aided by other emergency services. However, other agencies, such as law enforcement, will also be present and need to be integrated into the management structure.

(56) The recovery phase is geared towards stabilising the scene and ensuring that all immediate hazards are removed or reduced to a low-risk level. During this phase, local and national officials will initiate the scene-of-crime examination and will seize all relevant material that may be required for evidential and forensic purposes. Also during this phase, the control of the scene may be shared between recovery personnel and law-enforcement officers. In this phase, first decisions might be made on relocation, and food and water controls.

(57) In the restoration phase, there is a gradual restoration of the site to normal operations, and the emergency management system, which managed the rescue and recovery phases, will hand control of the scene to the authorities responsible for determining the restoration objectives and the process used to remove remaining hazards to agreed levels.

2.7. Links 

(58) The relationship between exposure routes, protective actions, and response phases varies depending on the unique circumstances of the specific radiological attack. In Table 2.1, which is of a qualitative rather than quantitative nature, an attempt is made to identify some of the potential scenarios and links to be expected at various phases during the response. As can be seen, there will be an overlap between the different phases and the protective actions that may be taken.

Table 2.1. Emergency phases, exposure routes, and protective actions following a malicious attack (

)

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• 1 Activity is a quantity measured in units termed ‘becquerels’ (although, in the past, the unit ‘curie’ was – and still is – widely used). One becquerel represents an extremely small activity (conversely, 1 Ci represents a significant amount of activity as it equates to 37 thousand million becquerels).
• 2 Dose is the relevant quantity for expressing the amount of radiation exposure. The radiation dose received by any substance, including human tissues, is termed ‘absorbed dose’ and is assessed in units called ‘grays’ (in the past, the unit ‘rad’ was used). Different types of radiation have different effectiveness to induce damage, and different organs and tissues have different sensitivity to radiation exposure. Therefore, the absorbed dose has to be weighted to take account of these differences. The quantities resulting from the absorbed dose weighting for taking into account the effectiveness of various radiation types and the sensitivity to radiation of various organs and tissues are termed ‘equivalent dose’ and ‘effective dose’, respectively, and are both measured in a unit termed ‘sievert’ (in the past, the unit ‘rem’ was used). The equivalent dose, which is used to express tissue and organ doses, and the effective dose, which is used for assessing the whole body implications, can only be employed for ‘normal’ radiation protection purposes, i.e. for situations causing relatively low doses that may merely induce low-probability delayed health effects, and cannot be formally used to express high doses. As these radiation protection quantities are not directly measurable, instruments for assessing doses in people or in the ambience are usually calibrated against defined operational quantities (termed ‘personal dose equivalent’ and ‘ambient dose equivalent’) that correspond approximately to the radiation protection quantities and are formally used for verification of compliance. For reasons of simplification, the report only uses equivalent dose, effective dose and the unit termed ‘millisievert’ (mSv), which is a submultiple of the sievert equal to a thousandth of a sievert (one mSv equates to 100 thousandths of 1 rem or 100 millirem).
• 3 The duration of the exposure is an important consideration since protraction of the dose influences the threshold dose at which deterministic effects may appear. If the interventions are fully effective, the averted dose is numerically equal to the projected dose, but these are conceptually different quantities (vide infra). However, it may be appropriate to express the intervention level in terms of a projected dose for that pathway rather than an averted dose. Intervention may not be fully effective, either because the dose has already been received, or because the intervention itself may only partly reduce the total projected dose.
• 4 While each intervention is judged on its merits, the sum of residual doses from all pathways after implementation of protective actions should be kept under review because of the possibility of serious deterministic health effects.
• 5 The Commission defines activity as the average number of spontaneous nuclear transformations taking place per unit time in an amount of radioactive substance (ICRP, 1991a, Paragraph 37).