Intervention Levels for Air, Drinking Water and Food after Fukushima Nuclear Accident in Japan 2011

Transcription

1 ABSTRACT Intervention Levels for Air, Drinking Water and Food after Fukushima Nuclear Accident in Japan 2011 Helena Janžekovič, Milko J. Križman Slovenian Nuclear Safety Administration P.O. Box 5759, Železna cesta 16, SI-1001, Ljubljana, Slovenia On March 11, 2011 a nuclear accident in Fukushima in Japan caused by an earthquake and tsunami started. It was finally categorised at level 7 on the International Nuclear and Radiological Event Scale (INES scale). On the same day, the evacuation of people in the vicinity of the Fukushima Daiichi NPP was initiated and a day later, the evacuation of inhabitants around the Fukushima Daini NPP started. Later other countermeasures related to the general public were applied including control and restriction of food and drinking water, where iodine and caesium radioisotopes were identified. The analysis of countermeasures related to the general public shows partial flexibility of the emergency preparedness system in Japan, which was based on the very new approaches, but in some parts also nearly a decade old approaches were used. The evacuation as well as all other countermeasures in any nuclear emergency should be based on pre-defined and well-established procedures within the NPP and outside the nuclear site. Pre-established procedures should be based on the emergency action levels and on operational intervention levels. The levels are basic tools in order to act in time in the course of an accident. They can be used by operators as well as by regulatory authorities. The evacuation of around people was based on the anticipated scenario founded on the data obtained from the NPP site including the data from radiation monitoring instruments and systems. Measurements of radiation parameters during and after nuclear accidents of such scale are a demanding task. As a rule, one of the first parameter is the external dose rate related to gamma radiation. However during and after major nuclear accidents not only elevated dose rate due to radioactive deposition and clouds are present, but also contamination of air, drinking water and food on the territories which are settled by the general public. Contamination strongly hits the quality of life of affected people. While the trigger for some protective actions in Japan related to evacuation was established a decade ago, the operational levels for food and drinking water were in general consistent with the levels established by the European Union after the Chernobyl accident. Nevertheless, it should be pointed out that not only applicable action levels or intervention level as appropriate should be in place, but also the implementation of protective actions plays a fundamental role to assure a successful remediation process. One of the main actions is the establishment of a contamination control programme. Its establishment is an extremely difficult task in case of such a big nuclear accident accompanied by a natural disaster. 1 INTRODUCTION On March 11, 2011 the regulatory authority in Japan issued instructions for the evacuation of people around the Fukushima Daiichi NPP, which was heavily influenced by 105.1

2 105.2 the earthquake and tsunami that day. The instructions for evacuation of people around the Fukushima Daini NPP were issued a day later. Evacuation was based on the anticipated scenarios founded on the data obtained from the NPP sites including the data from radiation monitoring instruments and network systems. Measurements of radiation parameters during and after nuclear accidents of a such big scale are a demanding task. As a rule, one of the first parameter measured is the external dose rate related to gamma radiation. However, during and after major nuclear accidents not only elevated dose rates due to radioactive deposition and clouds are present, but also contamination of air, drinking water and food on the territories, which are occupied by general public. This contamination strongly depends on weather conditions during and after releases as well as among others on physical and chemical characteristics of discharges from nuclear installations. Half-lives of radioisotopes released span from a few hours as for 135 Xe to more than ten thousands years for 239 Pu with a half-lives of years. In addition, earth surface characteristics e.g. mountains can very much influence the contamination levels. Contamination can strongly affect health of the general population and their quality of life. In order to take protective actions in a due time during the progress of a nuclear accident, triggers should be developed as part of a protection strategy [1] initiating actions. As pointed out in [1] as a rule besides triggers related to dose consideration and to the contamination of the environment other triggers can be used, for example a failure of a specific system in a plant can be the trigger for a specific protection action. Nevertheless, protective actions in an emergency strategy are as a rule firstly related to the dose consideration. In order to assess real doses, the characteristics of exposure or possible pathways of exposure of people and of contamination of the environment should be known in due time. The intervention levels used as a trigger used widely in the last decades are not recommended [1, 2] due to the fact that very often optimisation of protection was not considered below the intervention levels. In addition, intervention levels were used not as a part of the overall protection strategy and, as a rule, overall exposure was easily neglected. If only external exposure is taken into account and internal contamination is neglected, the overall strategy is not correct. Nevertheless, intervention levels can be still useful as inputs to develop an overall strategy. Today many countries including Slovenia [3] are going through a transition period in developing their protection strategy, namely intervention levels are still used in their protection strategies. However, the countries are fully aware that reference levels in case of an emergency exposure situation are recommended by the ICRP [2]. After the nuclear accident in Chernobyl in 1986 it also became evident that protective actions and consequently intervention levels or reference levels as appropriate must be harmonised on the international level. The majority of international recommendations or guidelines are based on generic criteria or operational intervention levels (OIL) as for example given in [4, 5, 6] taking into account recommendations of the ICRP already mentioned. The early phase of the accident in Japan required major protective actions applicable for that phase of the nuclear accident, i.e. sheltering, evacuation, iodine thyroid blocking, individual decontamination and medical intervention as well as preventive agriculture actions in order to reduce or prevent exposure from ingestion. In spite of a huge amount of data related to Fukushima accident already published, only preliminary analyses of facts are taking place [7]. As a result the data regarding the decision-making process on the implementation of the protection strategy in Japan in the last moths are still very scarce.

3 NUCLEAR ACCIDENT IN JAPAN AND THE IMPLEMENTATION OF PROTECTIVE ACTIONS FOR THE GENERAL PUBLIC In the early phase of the nuclear accident in 2011 Japan implemented protective actions due to the conditions of two nuclear power sites, namely due to the situation at the Fukushima Daiichi NPP and the Fukushima Daini NPP. The countermeasures were related to the occupational exposure as well as to the protection of the general public. The first countermeasure related to the general public was the evacuation of residents living within 3 km from the Fukushima NPP on the March 11, 2011 that was later replaced by a set of instructions regarding countermeasures. Table 1 shows the implementation of the selected early and intermediate phase countermeasures related to the public exposure as well as some consequences. Economic consequences of the countermeasures are not estimated. Data on countermeasures are based on available reports, particularly on the data published in [7, 8]. Due to relatively complex emergency response organization for a nuclear accident in Japan, e.g. some institutions issued advice while others restriction, as well as due to the involvement of many institutions, the data were sometimes simplified and should be taken with caution. Table 1 also describes time dimension of the protective actions taken by the Japanese government showing also the changes of these protective actions. The changes were necessary in order to adjust the countermeasures to the development of the accident as well as to the new or detailed data regarding the characteristics of the accident. Additional radiation monitoring systems in areas affected by crippled NPPs were established. Furthermore, mobile cars and airplanes with radiation monitoring systems provided detailed data. Extra analyses of contamination of soil with caesium and analyses of contamination of food and drinking or underground water were used. In addition to the countermeasures presented in Table 1 many other protective measures applied to persons, who were not involved in recovery work and emergency preparedness. Such persons belonged to groups of people, who would be in a normal situation a part of the general public. Such groups include workers of fishery industry, teachers in Fukushima prefecture, who were due to the accident obliged to use pocket dosimeters, port authorities, who were obliged to monitor dose rate of the atmosphere and seawater, and customs officers at the harbour and ship operators, who were obliged to control contamination of containers and ships. Some additional protective measures were also applied for screening and decontamination of persons from the general public and of specific items. Also specific protective measures were related to hospitalised patients whose evacuation was delayed. Furthermore, additional protective actions were applied also when persons temporary returned home in the evacuation area.

4 105.4 Table 1: Implementation of main countermeasures in the early and intermediate phase of the nuclear accident in Japan, which followed an earthquake and tsunami occurred on the coast of Japan on March 11, 2011 Evacuation and Sheltering Date Scope of Countermeasures Consequences March 12 Evacuation 20 km around the Fukushima Around people were Daiichi NPPs evacuated. Evacuation 10 km around the Fukushima Daini NPPs March 15 Sheltering of the population living between 20 to 30 km from the Fukushima NPPs The exact number of evacuees is not published because many April 21, 22 Evacuation of north-west area of the plant beyond 30 km from the Fukushima NPPs a within 30 days. The area of irregular shape extends to nearly 50 km from the NPP. The Deliberate Evacuation Area was defined as well as the Evacuation Prepared Area defined as the area where people should be constantly prepared for evacuation. It contained most of the area within the perimeter of 30 km around the Fukushima NPPs. The radius of the evacuation area around the Fukushima Daini NPPs changed, i.e. from 10 to 8 km. Iodine Prophylaxis people decided to leave the area. - Evacuation in the Deliberate Evacuation Area took place and a preparation for evacuation took place at Evacuation Prepared Area. As a result many people decided to evacuate temporarily. Date Scope of Countermeasures Consequences March 16 Iodine tablets were distributed to evacuation units were distributed centres around the Fukushima NPPs. Ingestion Restriction Date Scope of Countermeasures Consequences March 16 Advice not to use contaminated food - March 21 March 22 April 4 Shipment restriction of raw milk and some vegetables in four prefectures Ingestion restriction of some food in four prefectures Provisional values for contamination of food applied later used in the regulations. b Ingestion and Shipment Restriction Date Scope of Countermeasures Consequences Ingestion and shipment restriction of some food in four prefectures and three towns - - The basic inspection policy including restriction policy of items was published. Agriculture Countermeasure Date Scope of the Countermeasures Consequences April 7 Basic policy on rice cropping was published. The prohibition of cropping is based on measurements of caesium concentration in soil. April 22 Rice cropping prohibition for 2011 in some areas, among others all areas within 20 km zone around the Fukushima NPPs -

5 105.5 a The provisions are based on the ICRP reference levels for an emergency exposure situation [2] and on the calculation showing that people living in that area would receive over 20 msv over the next years. b The value for seafood of 2000 Bq/kg of iodine radioisotope was established on April 5, OPERATIONAL INTERVENTION LEVELS IN JAPAN The triggers for a specific protection action can be operational intervention levels, emergency action levels (EALs) or other indicators of conditions on the scene as given in [6]. Protection of the public is not internationally harmonised, sometimes even not among the neighbouring countries. In addition, due to the unpredictability of a scenario of a nuclear accident, a certain degree of flexibility must be incorporated in emergency strategy planning. Nevertheless, general guidance for actions is published by different organisations e.g. WHO, IAEA. The IAEA published in [4] generic optimised intervention levels based on the avertable dose for three urgent actions, namely evacuation, sheltering and iodine prophylaxis as well as the generic action levels for foodstuff expressed in activity concentration in kbq/kg. In addition, the IAEA published re-evaluated default OILs [6] in 2011 based on field measurements giving also elaborate explanation of the limitation when using the proposed OILs. It also published EALs for light water reactors. Altogether six OILs and a comprehensive system related to all appropriate protection actions are applied. Three OILs are based on one or more quantities, namely: - gamma dose rate in air - direct beta surface contamination measurements - direct alpha surface contamination measurements. Two OILs are related to the measurements of contamination of food, milk and water, one to the screening using gross beta and gross alpha activity concentration in Bq/kg and another using activity concentration for specific radionuclides. The European Union (EU) also started emergency preparedness activities after the Chernobyl accident in order to assure a harmonised approach in case of a radiological or nuclear emergency. Nevertheless, only partly harmonisation has been achieved till today. Among others, harmonisation is assured by publishing the so-called future accident legislation which is related to the contamination of food and feedingstuffs [8]. As a result, when comparing triggers which were used in Japan in the course of the accident with predefined triggers from literature, it should be taken into account that the accident is still in progress and emergency teams are still inspecting and controlling the situation. 3.1 Operational Intervention Levels for Air Contamination According to reported data [7] the Japanese authorities focused on observable criteria, i.e. on the condition of the NPPs and later in the course of the accident also on the dose rate monitoring results in air when considering evacuation and sheltering. Gamma dose rates and the contamination of air were also measured by different monitoring systems e.g. some of them were installed on airplanes. As pointed out in [6] it is difficult if not impossible to perform measurements of activity concentration in air in a due time and to analyse the result during the release. In addition, when the release is going on the variation of activity concentration strongly depends on time and on local conditions. The highest dose rates were measured in the Fukushima prefecture and in north-west regions of the plant. In some of the mentioned regions the measured result at a distance of km from the plant was higher than 2.25 µsv/h.

6 105.6 Table 2 shows pre-established triggers in the emergency preparedness guidelines of the Ministry of Education, Culture, Sport, Science and Technology (MEXT) for evacuation, the avertable doses given in the IAEA publication [4] and used by the Nuclear Safety Commission (NSC), OIL2 IAEA values from 2011 [6] and ICRP criteria [2], i.e. reference levels for an emergency exposure situation. As emphasised by the authors of the report given in [7] the Japanese authorities later in the course of the event used a triggering level of 20 msv/year as a proper standard for protection measures. As a result the areas where accumulate dose can reach 20 msv/year were designated as Deliberate Evacuation Area on April 22, People from these areas were evacuated for at least a month after the instruction had been issued. Table 2: Selected pre-established triggers related to evacuation, temporary relocation and sheltering Criteria Quantity Trigger value Countermeasure MEXT [7] air dose rate 100 µsv/h sheltering IAEA [4] avertable dose within 2 day 10 msv sheltering IAEA [4] avertable dose in a period of 50 msv evacuation no more than one week IAEA [6] OIL2 (for gamma dose rate) 100 µsv/h temporary relocation ICRP [2] reference level for emergency exposure situation msv/y all countermeasures combined Monitoring of radioisotopes in air due to the accident in Japan was performed intensively also outside Japan and as reported by the Comprehensive Nuclear-Test-Ban Treaty (CTBTO) the radioisotopes were detected practically all over the northern hemisphere. It should be stressed that the concentration of particular radionuclides or their combination in the air in the affected areas can be estimated even after the end of the accident and also without measurements during the accident. Such assessment is based on the information of a deposition pattern of dust or in soil, measurements outside the affected site, on time - dependant meteorological data, information about the source term and its time dependence. The assessment can be further used when estimating exposure of people and the risk associated with the nuclear accident. As a result, such assessment can be a useful input for lessons learnt connected to the factors which actually triggered the protective actions. 3.2 Operational Intervention Levels for Food and Drinking Water The restriction on food and water was put in place in Japan on March 17, 2011 by using provisional OILs for food and drinking water regarding the three groups of the radioisotopes related to its radiotoxicity, namely: - sum of specific activities of isotopes of iodine - sum of specific activities of alpha-emitting isotopes of plutonium and transplutonium elements - sum of specific activities of other radionuclides with half-life greater than 10 years, except 14 C and 3 H. Taking also into account different types of food, e.g. liquid foodstuff as well as radiosensitivity of children, the specific levels are established for infants and young children. A part of the Japanese OILs is presented in Table 3, where levels for iodine and caesium isotopes are given. For a comparison the values of European legislation that are already prepared for future accidents and were also immediately, i.e. on March 25, 2011, applied for contaminated food originating from Japan, are also given. The levels used in the EU, namely in the Council Regulation (Euratom) No 3954/87, were based on the Codex Alimentarius. In a

7 105.7 course of the Fukushima accident some levels were later, i.e. on April 11, 2011, replaced by the Japanese levels. Namely, those OILs from the Japanese legislation were used which were available. As shown in all cases OILs from Japan are lower than pre-defined levels in EU legislation, i.e. levels before the accident in Japan. The details regarding OILs used in Japan and EU levels are given in legislation available in [8]. Table 3 also presents the FDA USA values for triggering protective actions, showing the so-called Derived Intervention Levels (DILs) for a particular radionuclide group [9]. No details are given for different types of food in the USA. Table 3: The Japanese OILs for food and drinking water for iodine and caesium radioisotopes. The EU values are taken from the Council Regulation (Euratom) No 3954/87 and USA values, namely Derived Intervention Levels (DILs) are also added. Data are taken from [8, 9] Radioisotopes Iodine Caesium Country Food for infants and young children [Bq/kg] Milk [Bq/kg] Other foodstuffs, except liquid foodstuff [Bq/kg] Liquid foodstuff [Bq/kg] Japan EU USA 170 Japan EU USA 1200 In addition to establishing the OILs for food and drinking water regulatory authorities in Japan also put in place a comprehensive inspection system for controlling food and drinking water. Although a thorough analysis of data related to contaminated food and drinking water due to the accident has not been published yet, as a rule iodine and caesium radioisotopes are found. Generally contamination is identified in prefectures, where contamination is expected. Some data are given in [10]. The contamination of food originating from Japan can be a challenging issue in the following decades. In Japan specific agriculture countermeasures are taking place, e.g. control of soil before planting, control of feedingstuffs. It should be also pointed out that not only the EU countries but also some other countries put in place extensive food monitoring programme for screening all or some food imported from Japan, e.g. the USA [9] and Brazil etc. As a rule countries geographically closer to the accident than Europe also implemented appropriate screening programmes of some food originating from their countries in order to avoid any contamination from the fallout due to the Fukushima accident [9]. The radionuclides from the accident released into the ocean pose a specific issue [11, 12]. In the EU a specific control is given to fish, fishery products and other marine products caught in FAO Major Fishing Areas 61, 67, 71 and 77 and feed and food processed or contained items mentioned and as put in the EC note (possibly) originating in/caught in the Pacific region [11]. 4 CONCLUSIONS The regulatory authorities in Japan faced a nuclear accident at Fukushima Daiichi and Fukushima Daini NPPs which have been lasting for months and have required among others evacuation of people. The scenario of the accident has been never analysed or predicted before. In addition to evacuation and sheltering other countermeasures (e.g. control of food and drinking water) were taken. The regulatory authorities were not faced only with a

8 105.8 nuclear accident but at the same time they were faced with damages caused by earthquake and tsunami. The countermeasures affected quality of life of people living in the prefectures around the NPPs mentioned. The first analysis of the reference levels and OILs, used for the triggering of protection actions shows that, as in other fields related to nuclear safety, improvements are beneficial. Such improvements include the upgrading of procedures which were based on a partly obsolete strategy and simplification of the decision-making process. The analyses of OILs used in Japan related to drinking water and food are in line with the OILs prepared by the EU after the Chernobyl accident. Nevertheless, it should be emphasised that not only appropriate action levels should be in place, but also the implementation of actions including establishment of the appropriate monitoring programme of contamination plays a fundamental role in assuring a successful remediation process. As pointed out in [12] some tasks including the establishment of the programme already mentioned can be extremely difficult in case of such a big nuclear accident accompanied by a natural disaster. REFERENCES [1] International Commission on Radiological Protection, Annals of the ICRP, Application of the Commission s Recommendations for the Protection of People in Emergency Exposure Situation, ICRP Publication 109, ICRP, Elsevier, 2009, pp. 53. [2] International Commission on Radiological Protection, Annals of the ICRP, The 2007 Recommendations of the International Commission on Radiological Protection, ICRP Publication 103, ICRP, Elsevier, [3] Republic of Slovenia,»Decree On Dose Limits, Radioactive Contamination and Intervention Levels, Official Gazette of the Republic of Slovenia«, No. 49/2004, Republic of Slovenia, Ljubljana, [4] International Atomic Energy Agency, Preparedness and Response for a Nuclear or Radiological Emergency, Requirements, No. GS-R-2, IAEA, Vienna, [5] International Atomic Energy Agency, Arrangements for Preparedness for a Nuclear or Radiological Emergency for Protecting People and the Environment, Safety Guide, No. GS-G-2.1, IAEA, Vienna, [6] International Atomic Energy Agency, Criteria for Use in Preparedness and Response for a Nuclear or Radiological, Emergency Protecting People and the Environment, General Safety Guide, No. GSG-2, IAEA, Vienna, [7] Japanese Government, Report of Japanese Government to IAEA Ministerial Conference on Nuclear Safety - Accident at TEPCO's Fukushima Nuclear Power Stations, Transmitted by Permanent Mission of Japan to IAEA, June 7, 2011, available at [8] European Commission (EC), Energy, official web site, available at [9] Food and Drug Administration, USA, official web site, available at

9 105.9 [10] International Atomic Energy Agency, Fukushima Nuclear Accident - Radiological Monitoring and Consequences, IAEA official web site, available at Japan food. [11] World Health Organization (WHO), Food and Agriculture Organization of the United Nations (FAO), Impact on Seafood Safety of the Nuclear Accident in Japan, available at [12] Y. Yonekura, Exposures form the Events at the NPPs in Fukushima following the Great east Japan earthquake and Tsunami, 58 th session of the UNSCEAR, May 23, 2011, available at