Abstract
In 2020, the International Commission on Radiological Protection (ICRP) issued
1. INTRODUCTION
In 2020, the International Commission on Radiological Protection (ICRP) issued
2. GENERAL CONSIDERATIONS
2.1. Timeline for managing a nuclear accident
The 2007 Recommendations of ICRP (ICRP, 2007) introduced three types of exposure situation: existing, planned, and emergency. The situation-based approach is a basis of current radiological protection. To manage a large nuclear accident, it is convenient to distinguish between the early and intermediate phases, and the long-term phase. For implementation of the system of radiological protection, ICRP considers the early and intermediate phases as emergency exposure situations, and the long-term phase as an existing exposure situation. The transition from an emergency exposure situation to an existing exposure situation does not necessarily take place at the same time in all affected areas.
2.2. Consequences of a large nuclear accident
A large nuclear accident causes a breakdown in society, affecting all aspects of individual and community life. It has large and long-lasting societal, environmental, and economic consequences. Radiation-related consequences are radiation-induced health effects, such as tissue reactions, cancer, and heritable diseases. In the environment, there are consequences for fauna and flora. In addition to radiation-induced health effects, there may be other health impacts due to changes in lifestyle attributable to protective actions taken to avoid radiation exposure. A large nuclear accident has societal, economic, and psychological consequences. These consequences affect the disturbances to daily life and the well-being of people.
2.3. Principles for protection of people and the environment
The objectives of radiological protection are achieved using the fundamental principles of justification of decisions and optimisation of protection. The principle of justification ensures that decisions regarding the implementation of protective actions result in a benefit for the affected people and the environment. The principle of optimisation of protection applied with reference levels aims to limit inequity in the distribution of individual exposures, and to maintain or reduce all exposures to as low as reasonably achievable, taking into account societal, environmental, and economic factors. Justification and optimisation are applied in mitigating radiological consequences during all phases of an accident, and should take careful account of all non-radiological factors in order to preserve or restore the living and working conditions of all those affected, including decent lifestyles and livelihoods.
The application of dose limits is not appropriate in emergency and existing exposure situations following an accident. ICRP defines reference levels to be selected within generic bands of exposure considering the induced risk of radiation as well as the feasibility of controlling the situation.
2.4. Justification of protective decisions
Responsibility for making decisions on the justification of protection is usually the role of authorities and responsible organisations. The aim is to ensure an overall benefit, in the broadest sense, to society and not necessarily to each individual. There are many aspects of the justification of decisions that can be usefully informed by organisations or individuals outside the authorities. Therefore, ICRP recommends involving key stakeholders in public processes for the justification of decisions whenever possible. ICRP considers that the justification of decisions should be re-assessed regularly as the overall situation resulting from the accident evolves. Therefore, justification is not a ‘one-off’ consideration taken during planning or during the management of an accident. It should question whether the decisions already taken continue to do more good than harm in the broadest sense. The decision to allow people to stay in affected areas should only be taken when the necessary conditions are met, particularly protection against the potential health consequences, and the achievement of suitable living and working conditions, including sustainable lifestyles and livelihoods.
2.5. Optimisation of protective actions
Implementation of optimisation of protection is a process that requires good understanding of the exposure situation to choose the best protective actions given the particular circumstances. It should reflect the views and concerns of stakeholders, and the ethical values that govern radiological protection. Prudence, justice/equity, and dignity are universal core ethical values that underlie the system of radiological protection, particularly the optimisation principle. The optimisation process inevitably has to cope with conflicts of interest among stakeholders, and must seek to reconcile their different expectations and needs.
One of the characteristics of radiation exposure is the large distribution of exposures received by responders and people living and working in the affected areas. ICRP therefore pays particular attention to equity in the distribution of exposures within groups, and recommends that optimisation of protection should aim to reduce the exposure of the most exposed individuals as a priority.
2.6. Reference levels
Reference levels are used as guiding values to select protective actions. At the beginning, a fraction of the individual exposures may be above the reference level. A priority should be to identify the most exposed people in order to prevent or reduce their exposure. The protective actions should progressively reduce the number of people receiving exposures above the reference level. When conditions evolve and the dose distribution changes, it may be appropriate to re-evaluate the reference level.
For the protection of responders on-site during the long-term phase, the reference level should not exceed 20 mSv year1. For the protection of responders off-site, the reference level should be selected within the lower half of the recommended band of 1–20 mSv year−1. The Commission recommends that responsible organisations should adopt a lower reference level whenever possible. For the long-term phase, the reference level should be selected in the lower half of the recommended band of 1–20 mSv year−1 for existing exposure situations, taking into account the actual distribution of doses in the population and the societal, environmental, and economic factors influencing the exposure situation. The objective of optimisation of protection is a progressive reduction in exposure to levels towards the lower end of the band, or below if possible. ICRP reiterates that the process for selecting the reference level should result from a careful balance of many inter-related factors, including the sustainability of social life and economic activities, as well as the quality of the environment, and should appropriately reflect the views of all relevant stakeholders.
Depending on the accident scenario, this could take several years, or even decades, because exposure of people living and working in contaminated areas largely depends on their habits and living conditions, which cannot be strictly controlled. It is therefore not possible to guarantee that all individual doses will be kept below the reference level in the long term. Selection of the reference level to manage the long-term phase is a complex decision that should be informed by societal and ethical value judgements. Due to this complexity, ICRP recommends that stakeholders who will be confronted with the situation should be involved as much as possible when selecting the value of the reference level.
3. POST-ACCIDENT RECOVERY
3.1. Moving from the intermediate phase to the long-term phase
Protective actions implemented during the early and intermediate phases should be lifted, adapted, or complemented when authorities and stakeholders consider that these actions have achieved their expected effect, or when their continued application is no longer justified.
Decisions on allowing those who have been temporarily relocated to return to their homes involve an extensive dialogue with the affected people and the authorities and professionals in their communities. ICRP emphasises that individuals have a basic right to decide about their future. All individual decisions about whether to remain in or leave an affected area, or to return home or not, including those of voluntary evacuees, should be respected as a matter of dignity, and supported by the authorities.
The decision by the authorities to allow people to live permanently in an area should be taken in close consultation with representatives of the local communities and all other stakeholders when the following conditions are met. Characterisation of the radiological situation of the environment, foodstuffs, goods, and people in affected areas is sufficiently well achieved. Mechanisms are established for the involvement of local stakeholders in decision-making processes. A system for radiological monitoring of the environment and measurement of individual external and internal doses has been established, as well as a health surveillance system. Appropriate mechanisms (e.g. co-expertise process) have been put in place to involve affected people in improving their well-being and quality of life.
3.2. Long-term phase
The accidents at the nuclear power plants in Chernobyl and Fukushima demonstrated that management of the long-term phase based solely on radiological principles and criteria was not sufficient to respond to the challenges faced by individuals and communities in affected areas. While radiological principles and criteria are an essential input to the management of the long-term phase, they should be used appropriately and with due flexibility to accompany the rehabilitation of the living and working conditions of affected individuals and communities.
It is the government’s responsibility to provide relevant guidance to the population on how to protect themselves, and the conditions, means, and resources to implement this protection effectively.
3.3. Protection of responders during the long-term phase
The aim on-site is to dismantle the damaged installation, including management of the corresponding waste. The exposure situation is mainly characterised and the source is mostly under control, although some technical difficulties may remain, and unforeseen situations may occur at any time. Circumstances on-site may require planning for exposures above the reference level. In that case, ICRP recommends special arrangements limited in time, which should be prepared with the greatest care after deliberation between concerned parties. The exposure of these residents should be considered as public exposure, and should be managed using the same requisites as for the general population in affected areas.
When an occupationally exposed worker is involved as a responder, the exposure received during the response should be accounted for and recorded separately from exposures received during planned exposure situations. Arrangements for dose records of responders based on agreement between the responsible authorities, operators, employers, and workers should be made in advance as part of the plan for nuclear installation accidents at the preparedness stage. ICRP recommends that occupationally exposed workers who wish to return to their regular activities when the intermediate phase is over should not be prohibited from doing so. The decision should be taken by the authority responsible for the installation on a case-by-case basis.
3.4. Protection of the public and the environment
Management of the protection of people in affected areas in the intermediate and long-term phases is a complex process involving not only radiological factors, but also societal, environmental, and economic considerations. This process includes actions implemented by national and local authorities, and self-help protective actions taken by residents of the affected areas. ICRP recommends that the authorities, experts, and stakeholders should co-operate in the so-called ‘co-expertise process’ to share experience and information, promote involvement in local communities, and develop practical radiological protection.
3.5. Co-expertise process
This process of co-operation between experts, professionals, and local stakeholders aims to share local knowledge and scientific expertise for the purpose of assessing and better understanding the radiological situation, developing protective actions to protect people and the environment, and improving living and working conditions. The co-expertise process is effective in empowering individuals and communities affected by radiation to know how to protect themselves, and thus to develop a practical radiological protection culture needed to face the consequences of a nuclear accident. It enables people to restore their autonomy regarding decisions that affect them, which has been seriously impaired at the time of a nuclear accident. Furthermore, it contributes to reconnecting people, helps to develop their solidarity, and provides an opportunity for them to look to the future with more confidence.
4. CONCLUSIONS
Given the complexity of the situation created by a nuclear accident and the extent of its consequences, radiological protection only represents one dimension of the contributions that are likely to need to be mobilised to cope with the issues facing all affected individuals and organisations. They should be elaborated with the objective of putting radiological protection at the service of rehabilitating living and working conditions and the quality of life of affected communities. To achieve this objective, ICRP emphasises the crucial importance of involving stakeholders. Experts should adopt a prudent approach to manage exposures, seek to reduce inequities in exposures, take care of vulnerable groups, and respect the individual decisions of people while preserving their autonomy of choice.