Emergency Response Protective Actions Day 10 – Lecture 3

Objective To present background and guidance on major protective actions, which may be needed in the event of an accident to control the radiation exposures to members of the public Lecture notes: In recent years a number of accidents involving radioactive material have occurred that had, or could have had, consequences for the health of the general public. These have ranged from the major nuclear accident at Chernobyl in 1986 to accidental dispersion of medical and industrial sources and the re-entry into the Earth’s atmosphere of satellites carrying radioactive material. Reponses to accidents differed between countries. Some protective actions that were taken may, in the most extreme cases, have detracted from rather than increased the well-being of the populations concerned and the quality of the environment. Over the past decade considerable progress has been made in developing internationally recognised principles for decisions on protective actions and in providing quantitative guidance for applying these principles, notably by the ICRP, the IAEA, the WHO … This lesson explains present international understanding regarding protective actions and numerical guidance related to the intervention.

Content Exposure pathways Protection strategy Protective actions Evacuation Sheltering Thyroid blocking Relocation and resettlement Agricultural countermeasures Operational Intervention Levels Lecture notes: After short introduction we will look at the exposure pathways by which members of the public could be exposed to radionuclides. Then we will show how protection strategy relates to exposure pathways. The body of the lecture will be devoted to major protective actions and their advantages and disadvantages. We will finish the lecture by discussing operational intervention levels and short lecture summary

Three Major Principles The protective actions should Prevent serious deterministic effects wherever possible Be justified – they should do more good than harm Be optimised – they should do the most good Lecture notes: With the regard to the deterministic and stochastic health effects associated with radiation exposure, three major principles for the protection of the health of members of the public have evolved, and they appear to have almost universal acceptance. In short, they provide that protective actions should prevent serious deterministic effects wherever possible be justified – that is, they should do more good than harm, and be optimised – that is, they should do the most good. This is elaborated upon in Lesson X.1.1.

Exposure Pathways and Protective Actions Exposure of individuals may be external or internal and may be incurred by various pathways The various routes by which individuals may be exposed will influence decisions which protective actions should be taken to prevent or reduce the exposure Lecture notes: In the event of an accident, protective actions may need to be taken to control the radiation exposures of members of the public. Exposure of individual members of the public may be external or internal and may be incurred by various pathways. The various routes by which individuals may be exposed will influence decisions that the competent authorities should take in order to prevent or reduce exposure. In planning for emergency response, each possible pathway should be identified.

Human Exposure Pathways Plume Shine from ground contamination (ground shine) Cloud shine Fresh produce Fresh milk Skin contamination Immediate ingestion Inhalation Lecture notes: In general, the radiation dose received by the public during the first days of a nuclear reactor accident comes mostly from five sources: external gamma radiation from the radioactive cloud or plume, here called cloud shine, external gamma radiation from radioactive material deposited on the ground, called ground shine, inhaling radioactive material in the plume, external beta and gamma radiation from radioactive material deposited on the skin, and eating contaminated food and milk. During a release the dose from cloud shine, ground shine, skin contamination and inhalation are the most important. After the plume has passed, the dose from ground shine and eating of contaminated food and milk become most important. Dose from external gamma, skin contamination and inhalation can be prevented or reduced by what are referred to as urgent protective measures. These are protective measures that must be implemented urgently or immediately and include sheltering, evacuation, and thyroid blocking. Dose from ingestion can be reduced by restricting immediate consumption of locally produced food. The effectiveness of these actions in response to a nuclear power plant accident will be discussed. In practice, the decision to implement a protective action must also be based on the practicality of the action.

Preventive vs. Protective Actions Protective actions in the UPZ taken to avoid consequences to health based on measurements or predictions Preventive, or risk reduction actions in the PAZ taken to avoid the risk of exposure based on plant conditions no time for detailed analysis applies where protective actions may not be adequate or fast enough Lecture notes: This introduces another concept: protective actions vs protective or risk reduction actions. Protective actions are taken based on a known appreciation of the hazard, gained for example through field measurements of dose rates or activity concentrations. They aim to reduce the exposure to radiation. Preventive actions such as a precautionary evacuation prior to a release, are considered risk-reducing because they remove people from the hazard area before the hazard is certain to exist. They aim to reduce the risk of exposure to radiation. For example, even if a nuclear reactor core is melting, there is no guarantee that a major release will occur - the containment might well not fail - but a precautionary evacuation would be wise, because it removes the risk of exposure. It is warranted when delay might leave it too late to evacuate were a release to actually have started.

Preventive Actions Should be initiated before or shortly after a major release from core damage accident You can predict core damage before a release You can not predict the time or size of release once you have core damage Therefore must act on the status of the core Should not wait for a release before taking action Lecture notes: These preventive actions (e.g., evacuation) must be taken before or shortly after a major release to be effective. As an example for a nuclear accident, we can predict damage to the reactor core but not the exact time of or even whether there will be a release. Effective preventive action can be best assured by acting when core damage is recognised. Core damage is a very rare event, with only a few cases occurring during the life of the entire nuclear industry. Therefore, events warranting taking preventive actions without waiting for a release of radioactive material will be very rare. We can not wait until the release is detected in the environment because doing so could result in preventable deaths (deterministic effects).

Emergency Assessment Given large uncertainties and need for timely decisions in order for protective actions to be effective As simple as possible, yet effective Based on best understanding of severe accidents and international guidance Focus on data important for decision-making Do not be side-tracked by data that do not influence the decision-making Considerable time is needed to implement decisions Only use data that will be available at the time Lecture notes: The ability to assess the available information at the time of an accident is important in being able to take fast, appropriate decisions to protect the health of the population and the environment. There is a tendency often found among scientists to want to assess everything about the accident, but not focus on the needs of the response personnel and decision-makers. It is very important to recognise that there will always be very large uncertainties early on in an accident (the Chernobyl source term was reassessed ten years after the accident and changed by a factor of three; it is only recently that it was understood that during the TMI accident there was a serious risk of a major release). Despite these large uncertainties, we have seen that it is crucial to act rapidly in order for protective or preventive actions to be effective. So emergency assessment should be as simple as it possibly can be, and as complex only as absolutely necessary. It needs to take into account analyses carried out in advance of an accident and international guidance. Assessment must focus on the the information needed for decision-making and not be diverted onto academic issues. Assessment also needs to build in enough lead time to allow for any decisions to be implemented effectively. Finally it is common to find theoreticians assuming certain data will be available when it will not, e.g. many assessments rely on the ‘source term’ - the amount of radioactive material released - this will not be available early on at the time decisions to take preventive actions must be made in order to be effective.

Strategy to Reduce Public Risk Before or shortly after release - based on plant conditions Evacuate or substantial shelter within 3 - 5 km Take thyroid blocking near the plant After a release Prompt monitoring to locate areas requiring further protective actions. Restrict consumption of locally grown food to 300 km Monitoring to locate where food restrictions and relocation are warranted Lecture notes: All of these objectives combined with practical considerations lead us to a strategy for nuclear power plant accidents involving core damage. In summary, in order to substantially reduce the health risk off-site from a severe reactor accident upon detection of actual or projected core damage: Evacuate or provide substantial shelter for the people near the plant (3-5 km) and Provide thyroid blocking near the plant provided it will not delay evacuation or sheltering. After a release starts: Promptly monitor the area within about 25-50 km to locate where the dose from the cloud or ground shine could result in deaths or injuries if the public is not evacuated or sheltered. The shelters should also be monitored to ensure they are providing adequate protection. The appropriate protective action would then be taken based on these results. Restrict potentially contaminated food, milk or water out to about 300 km or more. After most of the release is over, monitor to determine where deposition levels still warrant restriction on food or where people should be relocated.

Protective Actions Urgent protective actions Sheltering Evacuation Administration of stable iodine Longer term protective actions Temporary relocation Resettlement Agricultural countermeasures Lecture notes: Experience shows that among the protective actions that are available in the event of a nuclear or radiological accident, those that need to be applied promptly to be most effective are sheltering, evacuation and administration of stable iodine. Additional protective action that could be applied promptly may include: control of access and egress improvised respiratory protection showering or bathing and changing clothing use of personal protective clothing Although these secondary protective measures may increase protection, it will usually be inappropriate to recommend any intervention levels for them, as the secondary measures do not stand alone but will supplement the primary protective actions.

Sheltering Protects against external radiation from cloud and ground; some protection against inhalation Most effective when properly applied Effectiveness depends on type of dwelling Duration limited to about 2 days Must be prompt May lead to spontaneous evacuation Lecture notes: Sheltering involves keeping members of the population indoors, in suitable buildings, to reduce radiation exposure from airborne radioactive material and from the ‘ground shine’. Sheltering is not recommended for a period exceeding 48 hours. Substantial sheltering refers to the use of facilities with specially designed shielded walls or basement of large masonry buildings. Ventilation systems with activated charcoal filters to protect against radioactive iodine may also be used in some substantial shelters. The effectiveness of sheltering to protect against external radiation from the cloud and ‘ground shine’ depends on the type of dwelling used and on the ability of the population to properly implement the measure. For example, low roofed houses in hot climates tend not to provide a very good protection. In “real life”, it is also difficult to ask people to stay confined to their house for more than a couple of days. And as at the Three Mile Island accident, it is quite likely that, in regions where the average family has access to one or more cars, an order to shelter may lead to a spontaneous evacuation. This could cause more difficulties and even more radiological consequences, especially if the evacuation is chaotic and leads to traffic jams during cloud passage.

Types of Shelters and Effectiveness Lecture notes: The effectiveness of sheltering (listed in figure) varies greatly depending on the structure, duration of the release and the exposure pathway. Because of the great variability of building structures, three classes of sheltering can be used when developing protective action strategies. These classes are: Normal -Typical homes and their basements; Normal shelter does not provide adequate protection from an airborne plume close to the site. It is used if evacuation is impossible (e.g., very severe storm), when preparing to evacuate or in areas where evacuation is expected to be needed . Substantial - Inside halls of large multi-story building or large masonry structures away from walls or windows, with estimated protection factors of about 10 from external and inhalation dose. This class may provide adequate protection for short periods. It can be used until monitoring can be conducted. Special - Specially designed shelters providing a factor of more than 100 reduction from external and inhalation dose. This class provides adequate protection for the duration of the accident. Sheltering is easy to implement but in most cases can not be carried out for long periods. In addition sheltering can be used as a preparation for an evacuation. The people in an area of potential risk can be instructed to “go inside” and listen to their radios for further instruction while preparations for evacuation are being made. However, for very severe reactor accidents sheltering in a typical home may not be sufficient to prevent deterministic health effects close to the facility. Sheltering is not a long term protective measure. It is intended to be used until additional information can be obtained; therefore monitoring must be performed promptly anywhere sheltering is used, to locate and evacuate hot spots.

Evacuation Most effective action for areas close to a facility Must be initiated prior to a release to avoid inhalation from the plume Must be timely to avoid external radiation from the ground Difficult to manage Spontaneous evacuation possible Lecture notes: Evacuation is the urgent removal of the population from a potentially or actually affected area. It is generally the most effective protective action against major airborne releases of radioactive material, but it is not without problems. First, there must be sufficient means of transportation to remove the entire population affected. Then, the road infrastructure must be sufficient to support a mass evacuation without traffic jams. Sufficient police or similar resources must be available to control traffic. And finally, there is the problem of where to keep the evacuated people for several days. In general, it is not recommended that evacuation and accommodation in emergency centres be in effect for more than about seven days. Moreover an evacuation itself takes time to implement, and this time must be built into any decisions to activate.

Lecture notes: The decision on which protective action to take is also influenced by the expected effectiveness of that protective action. For example, in a recent letter, the US Nuclear Regulatory Commission approved the staff recommendation that, based on the study of severe accidents, evacuation should be used promptly as the preventive, or risk reduction measure when significant fuel damage has occurred or is anticipated. This is based on studies that show that prompt evacuation is the most effective protective action and that, for severe accidents, a release could be large and yet leave no time once the release has started to implement an effective protective action strategy to avoid deterministic effects. This figure shows the results of an analysis of various measures that could be taken to protect the public in response to the most severe type of reactor accident resulting in core melt and early containment failure. This accident results in a very large release. The numbers are the probability of a person receiving a dose to the whole body (bone marrow) in excess of the threshold for early deaths (actually > 2 Sv, here). This shows, for areas within 5km, that the risk of deaths can be reduced to almost zero by starting evacuation at walking speed one hour before the release and substantially reduced by sheltering in a large building. Even walking out in the plume is no worse than basement sheltering in a normal home. This analysis assumes that the evacuation is conducted at walking speed and all people in areas with significant levels of contamination are evacuated subsequently within 6 hours.

Thyroid Blocking KI pills Protect against inhalation and ingestion of radioiodine only Very effective if taken early, especially for children Complex distribution strategies Difficult to distribute during emergency Difficult to maintain if pre-distributed Transient populations? Limited shelf life Large stock piles required Must be part of overall strategy Lecture notes: When the fuel of a reactor overheats and the fuel cladding fails, large amounts of radioactive iodine can be released. This iodine can be inhaled or can be deposited on vegetables or concentrate in the milk of animals grazing on contaminated grass. Inhaled or ingested iodine will concentrate in the thyroid. High thyroid doses can destroy the thyroid and greatly increase the risk of thyroid cancer, especially in children. The ingestion of radioactive iodine can be prevented by not eating or drinking potentially contaminated food. The dose to the thyroid from inhalation can be reduced by taking stable (non-radioactive) iodine, called thyroid blocking (iodine prophylaxis). The stable iodine will saturate the thyroid and prevent or reduce its uptake of the radioactive iodine. The distribution of stable iodine is an effective way to protect against the inhalation of radioactive iodine, provided that it is taken before or early into the release. However, getting the stable iodine to the people is not easy. For example, if the iodine supplies are kept at a central location, as it is in some countries, one has to deal with the logistic difficulties of distributing the iodine to all affected people during an emergency, which is time consuming, people intensive, and may put the emergency workers in charge of the distribution at risk. Pre-distributing the stable iodine has the problems associated with periodic refreshment before end-of-shelf life, updating distribution for new arrivals, and keeping track of transient populations. Also, this protective action requires that large stocks of stable iodine be kept at all times. All this represents real costs in terms of money and people.

Relocation and Resettlement To keep population out of the affected areas Relocation: more than 7 days but not more than few months Resettlement: permanent Expensive Disruptive Lecture notes: The longer-term protective actions are inherently very expensive and complex. They require that alternative living arrangements and food supplies be found for a large population. The psychological cost associated with them is great. At Chernobyl, for example, the relocation of rural population to urban areas is believed to be responsible in part for a significant loss of life expectancy due to medical problems associated with the stress of the move. Agricultural countermeasures are especially hard on farmers and producers, who will suffer significant financial losses. Financial compensation is an issue in all cases involving longer-term protective actions. Temporary relocation and resettlement. Temporary relocation is used when there is a need to keep the population out of the affected area for a period exceeding approximately 7 days but not more than a few months. This measure requires that temporary, but substantial facilities be provided for the affected population. It is expected that the temporarily relocated population will be able to return to their homes in due course. Resettlement however is by definition permanent. It is adopted when the dose to the affected population over a lifetime would exceed a certain criterion.

Psychological Effects of Relocation Relocation is especially dubious Has negative impact on mental well being If aimed to reduce risk for stochastic effects: Consider only future avoidable dose Dose already achieved cannot be reduced Involuntarily relocated people suffer most Elderly people are especially likely to suffer Lecture notes: From the psycho-social point of view, relocation as a protective action is especially dubious because of the documented negative impact on mental well being. If relocation is considered in order to reduce the risk for stochastic effects, it is therefore important to remember that the dose to be avoided is only the projected, future dose, while the dose already received cannot be reduced and should not be taken into account when deciding on relocation. If the dose to be averted is low, relocation should not be performed only in order to relieve stress, because experience shows that it is likely to be counterproductive in this respect. Stress effects are not mitigated and may even be increased by resettlement. Fear of the dose already received is not relieved. Relocated people, especially if involuntarily relocated, suffer from home sickness, disruption of social and cultural surroundings, and even from hostility from former inhabitants in the new residence area. Elderly people are especially likely to suffer from relocation. It has been shown that illness and mortality are increased in the elderly by involuntary moves.

Agricultural Countermeasures Not to be considered urgent, though it should be timely Applied directly to plants or to soil Appropriate processing of food Expensive Great detriment to farmers: compensation costs Alternate food supplies required Loss of confidence in food supplies Lecture notes: Agricultural countermeasures. Protective actions related to food include: an immediate ban on the consumption of locally grown food in the affected area; the protection of local food and water supplies by, for example, covering open wells and sheltering animals and animal feed; and the long term sampling and control of locally grown food and feed. Control of milk is particularly important because it is a significant part of the diet of children, as well as concentrating important radionuclides, such as radioiodine. Intervention to control contamination of foodstuffs will in general not be considered urgent, though it should be timely. In planning appropriate food controls after an accident it is necessary to consider the options available for reducing contamination levels in food. Controls may be placed at different stages in the production and distribution of foods in order to reduce or prevent contamination. Treatments can be applied directly to plants and to soil that will substantially reduce the intake of radionuclides into crops and animal feed. Substituting clean animal feed as well as applying specific treatment to animals can reduce transfer of radionuclides into the subsequent products. The appropriate processing of many foods prior to sale can significantly reduce their level of contamination. Finally, foods can be completely withdrawn from sale.

Public Monitoring and Decontamination Skin contamination could contribute to deterministic effects Public should be monitored Should not delay evacuation Screening or monitoring a sample is only practical method Instruct people to shower and change clothes as soon as possible Lecture notes: A major reactor accident could result in significant skin contamination. Beta radiation from the skin contamination could be a major contributor to skin dose. Therefore, plans to monitor potentially contaminated people should be made. If significant contamination is detected, the people evacuating should be instructed to shower as soon as possible. Levels of skin contamination that could result in deterministic health effects (> 3 Gy in 2 days) produce gamma dose rates 5 to 10 times background within 30 cm of the surface (skin) contamination. Therefore, significant levels of skin contamination should be detectable if monitoring is conducted in a low background area. Serious health effects can be expected at levels 10 times these. Simply showering and changing or washing clothing should be sufficient to prevent future skin dose from resulting in deterministic health effects.

Not directly readable on instrument GILs and GALs Not directly readable on instrument Develop operational intervention levels (OIL) as part of planning OIL readable on instruments used OIL used during accident to make decisions IAEA has developed suggested default OILs Revise defaults during accident Lecture notes: The BSS criteria are not values measured by instruments in the field and must be calculated or determined in the laboratory. Since there will be no time during an accident to perform such calculations, BSS guidance cannot be used directly as a basis for taking protective actions early in the accident. Operational intervention levels (OILs) must be calculated prior to any accident that can be directly measured (e.g., dose rate) in the field by the instruments to be used. These OILs will be used during an accident to decide promptly if protective actions are warrented. For example, areas with dose rates greater than 1mSv/h indicates evacuation is warranted.

Gamma Dose Rate Measurements in Environment Most important environmental monitoring Easy to measure with simple instrument and little training Can use to decide where to: evacuate shelter give thyroid blocking relocate Lecture notes: Gamma dose rate measurements are the most important environmental measurements made early in an accident. Gamma dose rate is easy to measure with simple instruments by teams with only minimal training. Gamma dose rate measurements can answer the most important questions of indicating where deterministic health effects are possible and where urgent protective actions are warranted.

Default Gamma Dose Rate OILs 1.0 mSv/h ( 100 mR/h) - Evacuate 0.2 mSv/h (20 mR/h) - Relocate 0.1 mSv/h (10 mR/h) - Thyroid blocking 1.0 µSv/h (100µR/h) - Restrict local food 0.1 µSv/h (10µR/h) - Typical Background Lecture notes: OILs for gamma dose rates are provided in BSS guidance for determining when evacuation, sheltering, and taking thyroid blocking is warranted. Evacuation is warranted at 1 mSv/h (100 mR/h), thyroid blocking at 0.1 mSv/h (10 mR/h) and relocation at 0.2 mSv/h (20 mR/h). These levels can be easily detected using standard gamma survey instruments Immediate consumption of locally grown food or milk from grazing animals should be restricted in any area with gamma dose rates above background (e.g., 100-500 nSv/h) if reasonable (e.g., restriction will not result in food shortages). These restrictions should remain until the food or milk has been tested. Since background dose rates are variable the gamma dose rate OIL in the BSS guidance is set at 1 µSv/h (1000 nSv/h) to be clearly above background.

10 kBq/m2 - I-131 food 2 kBq/m2 - I-131 milk 2 kBq/m2 - Cs-137 food Deposition Marker Isotope OILs to Restrict Food Produced in Contaminated Area 10 kBq/m2 - I-131 food 2 kBq/m2 - I-131 milk 2 kBq/m2 - Cs-137 food 10 kBq/m2 - Cs-137 milk Lecture notes: IAEA provides default deposition OILs to identify areas where locally produced crops or milk could have concentrations exceeding the GALs. These OILs are deposition levels of the marker isotopes I-131 and Cs-137. These levels may need to be revised once the actual composition of the deposited material is known. Higher food OILs may be used if food is scarce.

Food Concentrations OILs 1 Bq/kg - I-131 in food 0.1 kBq/kg - I-131 in milk, water 0.2 kBq/kg - Cs-137 in food 0.3 kBq/kg - Cs-137 in milk, water Lecture notes: The food concentrations OILs have also been calculated. These OILs will be used to efficiently assess food samples. Since it will be impossible to conduct an analysis of all potentially contaminated food, food analysis will most likely be used to confirm or revise restrictions placed on food that were based on the other criteria such as marker isotope deposition levels discussed above .

Summary Part of conventional emergency management Objectives of response Practical considerations Favour evacuation close in over other actions for severe accidents Combination of sheltering and evacuation can be effective KI pills can enhance effectiveness of sheltering Operational intervention level Establish OILs and methods before the accident, not during ! Use IAEA support material Lecture notes: For further information contact: The Emergency Preparedness and Response Unit Department of Nuclear Safety International Atomic Energy Agency Wagramerstrasse 5 A-1400 Vienna, Austria

Where to Get More Information INTERNATIONAL ATOMIC ENERGY AGENCY Intervention Criteria in a Nuclear or Radiation Emergency Safety Series No. 109, Vienna (1994) and Generic procedures for monitoring in a nuclear or radiological emergency IAEA-TECDOC-1092 (1999)