Post-accidental Situation Research Articles

Comparative study of nuclear post-accident management doctrines in Europe and North America

The French Nuclear Safety Authority (ASN) issued in 2012 a first version of a doctrine establishing the principles of management of a post-accidental situation following a major nuclear accident. Since this publication, the feedback of the Fukushima-Daiichi accident continued and numerous evolutions occurred, both in French and European regulations and in international recommendations from IAEA and ICRP. This had led to further developments in the French doctrine for management of a post-accidental situation. This will result in the publication of a new version of the French doctrine next year. This evolution also prompted questioning about the existence of such doctrines in other countries, especially in neighboring countries. It appeared also interesting to evaluate the agreement of these doctrines, including the French one, with international recommendations, especially the recently published general safety requirements (GSR), part 11, from IAEA. A benchmark study comparing the different post-accidental management doctrines available was then conducted and is presented here.

Sharp Interface Capturing in Compressible Multi-Material Flows with a Diffuse Interface Method

Compressible multi-materialflows are encountered in a wide range of natural phenomena and industrial applications, such as supernova explosions in space, high speed flows in jet and rocket propulsion, underwater explosions, and vapor explosions in post accidental situations in nuclear reactors. In the numerical simulations of these flows, interfaces play a crucial role. A poor numerical resolution of the interfaces could make it difficult to account for the physics, such as material separation, location of the shocks and contact discontinuities, and transfer of the mass, momentum and heat between different materials/phases. Owing to such importance, sharp interface capturing remains an active area of research in the field of computational physics. To address this problem in this paper we focus on the Interface Capturing (IC) strategy, and thus we make use of a newly developed Diffuse Interface Method (DIM) called Multidimensional Limiting Process-Upper Bound (MLP-UB). Our analysis shows that this method is easy to implement, can deal with any number of material interfaces, and produces sharp, shape-preserving interfaces, along with their accurate interaction with the shocks. Numerical experiments show good results even with the use of coarse meshes.

Mobile apps for environmental and health monitoring after a nuclear accident: Towards a better resilience with involvement of citizen science and general public

Background/Aim: One of the lessons learned from nuclear accidents is the need to increase stakeholder engagement in accident preparedness and response, including data collection by citizens (and citizen scientists). In particular, the use of personal dosimeters, including sensors connected to mobile phones, was widely used after the Fukushima accident, leading to the collection and sharing of many ambient radioactivity measurements, dedicated web-platforms for exchanging questions and advice, as well as attempts to initiate participative epidemiological studies. Methods: The SHAMISEN-SINGS European project combined 3 approaches: 1) review and testing of existing mobile apps for dose measurements; 2) review of relevant mobile apps on health & welfare that could be used after a nuclear accident, and 3) on-line anonymous survey & group discussions on awareness, experiences and willingness to use mobile apps for dose and health monitoring.Results: A Tool-kit for using apps for dose measurements has been developed, summarised in infographics for the general public, and described together with recommendations on developing and use of mobile apps for health monitoring in a booklet. A brief cost-benefit analysis based on data collected by citizens was performed to complement those existing from official sources. A data management plan was proposed, in which data from the apps can be used with benefits at the individual and societal level. Ethical issues related to apps development, data collection and sharing were explored. Conclusions: The Recommendations and Tool-kits for use and development of mobile apps for dose and health monitoring after a nuclear accident, as developed by the SHAMISEN SINGS project, are directed toward the general public, apps developers and relevant professional stakeholders. If implemented in collaboration with stakeholders and citizen scientists, they should provide individual and societal benefits, and may contribute to national and regional monitoring networks for radiation and health surveillance programs in post-accidental situations.

Co-exposure to internal and external radiation alters cesium biokinetics and retention in mice

Exposures in post-accidental situations are complex and include both external exposure and internal contamination with several radionuclides. However, in vivo and in vitro studies generally use simplified exposures, while a recent study suggested that combined external irradiation and internal contamination may induce more severe biological effects compared to single exposures. In an attempt to test the hypothesis of potential non-additive effects of multiple radiological exposures, we used a mouse model of combined external x-ray irradiation at 1 and 5 Gy and internal contamination with injection of 20 KBq 137Cs. The results showed differential kinetics of 137Cs elimination in irradiated animals compared to sham-irradiated, 137Cs injected animals. Moreover, changes in plasma potassium and in relative testis weight were observed 38 days after irradiation and injection in co-exposed animals compared to 137Cs injection alone. These results demonstrate that an external exposure combined with an internal contamination may lead to unexpected changes in biokinetics of radionuclides and biological effects compared to single exposures.

Internal exposure in post-accidental situations: a multi-pollution to take into account?

Major nuclear accidents (Chernobyl, Fukushima) induced the contamination of large areas with a mix of radionuclides (RNs), inducing both external and internal exposure at low dose and low dose rate. Numerous studies were conducted on the health effects in post accidental situations. However, in most cases, the exposure is ill-defined. Thus the health effects on exposed populations living in a contaminated territory remain a matter of controversy. Experimental results in rodents are somewhat in contradiction with results from the study of human populations. This might be due in obvious differences between rodent models and human physiology, but also could be due to simplified schemes of exposure used in the experimental settings. A hypothesis to explain these discrepancies is the differences in exposure schemes. Moreover, the exposure in real life is more complex than the simple exposure to ionizing radiation. In fact, the chemical pollution should also be taken into account. The hypothesis of a generalized model of interactions between chemical pollutants and radiological pollutants is reinforced by the recent descriptions of non-additive (either supra- or infra-) biological effects of mixtures of chemical pollutants. Since there is no available study on the health effects of mixed radiological exposures, it is not possible to exclude the hypothesis that a mixture of RNs may induce non-linear effects as compared to the effect of individual RNs. Thus it appears that futures studies on the health effects of radionuclides at low concentrations or external exposure at low dose rate should be done taking into account more realistic schemes of exposure, including mixtures of RNs, external exposure and chemical pollutants.

The consumption of locally-produced foodstuff: an important parameter of the radiological exposure for population living in the vicinity of French nuclear facilities

Either in normal or post-accidental situations, the ingestion of locally-produced foodstuffs, potentially contaminated, is one of the main exposures to the population living in the vicinity of nuclear facilities. For this reason, the French Institute for Radioprotection and Nuclear Safety has developed a specific methodology and has carried out surveys on dietary habits of some populations concerned. This study presents the methodology used for local food surveys, the amount consumed and how much food is produced locally. The results from the 6 surveys already done show that food surveys even if conducted with a specific aim as impact assessments provide further in-depth understanding of the food habits of local residents. There are still local specific population groups that have a high level of “home-consumption” for products more sensitive to contamination. For leafy vegetables and milk (products highly sensitive to contamination), home-consumption rates vary widely from one region to another from 76 to more than 90% and from 1 to 17% respectively. Specifically for the Andra survey carried out in a rural area in the North-East of France, self-sufficiency had reached 100% for a few products (game meat for example).

Overview of the PREPARE WP3: management of contaminated goods in post-accidental situation – Synthesis of European stakeholders' panels

Recommendations and requirements for the management of foodstuffs including drinking water and feedstuffs (but not other commodities) contaminated after a nuclear accident or a radiological event have been developed by international bodies such as Codex Alimentarius Commission or European Union as well as by individual countries. However, the experience from severe nuclear accidents (Chernobyl, Fukushima) and less serious radiological events, shows that the implementation of such systems (based on criteria expressed in activity concentration) seems to be not fully suitable to prevent several difficulties such as, for instance, stigmatization and even rejection attitudes from consumers or retailers (anticipating the fears of consumers). To further investigate the possible strategies and stakeholder expectations to deal with this sensitive issue, a study has been launched within the European research project PREPARE-WP3. The overall objective of this work, coordinated is to contribute to the development of strategies, guidance and tools for the management of the contaminated products, taking into account the views of producers, processing and retail industries and consumers. For this purpose, 10 stakeholder panels from different European countries have been set up. In addition, feedback experience from the management of contaminated goods following the Fukushima accident has been provided by Japanese stakeholders. This paper highlights the key topics tackled by the different European stakeholders’ panels.

Protection of French workers operating in Japan, AREVA’s experience

In the framework of assistance for Japan, the ACTIFLORAD project for liquid waste decontamination mobilized over 200 AREVA collaborators and 47 people who led their mission in the damaged site. Led between May 18th and July 6th, 2011, the French mission aimed at supervising the ACTIFLORAD process building and assisting Japanese teams in performing it. The post-accidental situation and emergency led to setting up a radiation protection organization in agreement with French regulation as well as integrated into the Japanese organization. This text establishes a testimony of the everyday life of the mission and its preliminary preparation.

Experience feedback from the IRSN's involvement in the FARMING post-accidental program

This paper is intended to present the experience feedback of the IRSN's involvement in the reflection on the management of a nuclear crisis. It sums up some results of the French FARMING working group, corresponding to the mobilization of a wide range of Agricultural Technical Institutes and to the appraisal of a compendium of agricultural countermeasures for the rehabilitation of rural contaminated territories in post accidental situations. Indeed, in France, since a few years, this problem has been almost exclusively considered by radiation protection experts, with no involvement of the other concerned actors. But according to the weight of the agro industrial sector in this country and to the problems related to the management of contaminated food in post accidental situations, the cooperation between radiation protection experts and agro industrial stakeholders appeared more and more necessary. Indeed, above all, farmers and other local actors would take a significant part to the rehabilitation actions from the short term to long term of a nuclear crisis period and then share the responsibilities of the crisis management. The working group has therefore opened new debates at the national level and valuable results have been obtained from the meetings at technical and strategic levels.

Management of the post-accidental situation applied to Nogent-sur-Seine nuclear power plant environment. First results of the “decontamination of soil and food chain" working group

From the beginning of 2002, Troyes prefecture has initiated a study about the management of a nuclear crisis caused by an accident at the Nogent-sur-Seine nuclear power plant. Several working groups were created, notably the `Decontamination of soil and food chain' group. The first results of this group, which involves the District Agricultural and Forestry Department, the Farming Chamber, the Institute for Radiological Protection and Nuclear Safety and the Veterinary Division are presented here. The scenario that had been developed for the accident considers the release of 3 radionuclides (131 I, 134 Cs and 137 Cs) in the environment. The scale of the crisis didn't require the evacuation and the sheltering of the population during the emergency phase. The consequences on the local agricultural products (cereal, sugar beet, vine, milk, cow meat ...) have been assessed up to 50 km and different strategies of agricultural countermeasures have been studied regarding to the local constraints (soil types, surfaces and quantities concerned) and to the consequences of their implementation (waste types and quantities, costs). Then, decision-making diagrams summed up the technical results and allowed to deepen the global thought.

ASTRAL V2.2: A new version to better assess post-accidental situations

Should an important release of radionuclides occur in the environment, one would quickly have to assess radionuclide concentration in media and foodstuff, deduce the potential exposition of concerned populations to the radiations, predict the evolution of the situation and propose different scenarios of managing the contaminated zones. To achieve this, the ASTRAL code was created, which can be used by a relatively large group of people composing crisis centres or making predictive impact studies. The starting point of the assessments is the ground deposit of radionuclides: the atmospheric dispersion phase and the cloud exposure are not taken into account here. The calculations achieved concern time evolution of radionuclide concentration in compartments of the agricultural and forest food chain as well as assessment of doses due to external and internal exposure. These values are compared to regulation limits and/or intervention levels. Different simulations of contaminated zones management can be led by applying counter-measures, dispositions meant to reduce the accident's impact on environment and populations. The seventy radionuclides taken into account in the present version are some of those met in case of accidents or during the exploitation of a Pressurized Water Reactor (PWR). They relate to 37 elements: Ag, Am, Ba, Br, Cd, Ce, Cl, Cm, Co, Cr, Cs, Eu, Fe, I, Ir, La, Mn, Mo, Nb, Nd, Ni, Np, Pm, Pr, Pu, Rb, Rh, Ru, Sb, Sm, Sn, Sr, Tc, Te, Y, Zn, Zr. On a temporal point of view, the predictions extend to 3 years after the deposition. The internet technology chosen for this version offers important advantages: the spreading and maintenance of the tool are very easy, the code may be installed on a portable computer, the access to results is much quicker, the interface is very user friendly, so that no training is needed to perform calculations. As for any radioecological tool, a large number of parameters intervene in the calculations. All parameters can be modified, even though different user profiles grant different rights in handling them.

137Cs and 90Sr root uptake prediction under close-to-real controlled conditions

Radionuclide soil-to-crop transfer was analysed in large undisturbed soil monoliths installed in lysimeters under controlled climatic conditions. The soils were representative of large agricultural areas in the European Union: Loamy-sand Orthic Podzol from Belgium, Loamysand Fluvisol from France, Loamy Calcic Luvisol from Spain, Silty-loam Orthic Luvisol from Germany, and Sandy-loam Eutric Fluvisol from the UK. On the lysimeters, winter barley was sown for two consecutive years on artificially contaminated soils simulating a post-accidental situation, 1 and 2 years after radionuclide deposition. The amount (Bq m -2) of 137Cs and 90Sr that accumulated in the crop was higher in the loamy-sand soils, regardless of the total radionuclides (MBq m -2) or available fraction content in the soil. The Orthic Podzol produced the highest 137Cs crop accumulation, and the Loamy-sand Fluvisol the highest 90Sr accumulation. Concentration ratios (CR) showed similar results, but with higher 90Sr transfer for the Podzol than for the Loamy-sand Fluvisol. The activity concentration of radionuclides in the plants was negatively correlated with crop yield, indicating that high crop productivity produced a general dilution effect in radionuclide concentration activity in plants. The relative radionuclide crop accumulation expressed in Bq m -2 was predicted from the soil availability parameters, that is the available 137Cs fraction divided by the distribution coefficient ( K D ) and by the K concentration in soil solution, and the available 90Sr divided by the cationic exchange capacity (CEC). These predictions could not be obtained when using the CR, as this does not fully account for the crop growing conditions which influence radionuclide uptake by the crop.

Agricultural countermeasures in the management of a post-accidental situation

Following a nuclear accident, it is important to reduce, as much as possible, population exposure radioactive aerosols that have settled on the ground and hard surfaces. Management of the crisis-situation is dependent on how much time has elapsed since the accident. Firstly, the emergency arrangements are designed to protect the rural population and their livelihoods. Secondly, there is the question of maintaining agricultural activity on the contaminated areas (possibly by modifying farming practices), and lastly the reduction of the overall impact of the accident. Agricultural countermeasures are protective provisions applicable to the farming system and to farm-produce. Their intrinsic and accumulative effectiveness and conditions and advantages of their implementation are now better understood, notably by their application, on a large scale, following the Chernobyl accident. Based on a wide reference study, this document supplies figures on the agricultural countermeasures classified in various phases of post-accidental situations.