Comparison of Discharges of the Nuclear Accidents in Japan 2011 and Chernobyl 1986

Transcription

1 Comparison of Discharges of the Nuclear Accidents in Japan 2011 and Chernobyl 1986 ABSTRACT Helena Janžekovič, Milko J. Križman Slovenian Nuclear Safety Administration P.O. Box 5759, Železna cesta 16 SI1001, Ljubljana, Slovenia A first attempt of comparisons of discharges of the Chernobyl and the Fukushima accident based on updated data shows several important differences. While the Chernobyl accident occurred in hours the discharges from the site took place for about ten days, the Fukushima accident escalated slower, but with a much longer time of discharges. While for the Chernobyl accident the time scale of discharges of particular radioisotopes is not known well, the development of the escalation of the Fukushima accident and related releases was predicted based on the characteristics of the nuclear site. During the Fukushima accident discharges were released into the atmosphere as well as into the sea, partly also unintentionally. During the Chernobyl accident, no discharges were reported into the aquatic system. Regarding the discharges into the air some similarities can be found. In both cases 131 I was the major radionuclide posing the immediate threat. The activity of the release of this radionuclide during the Fukushima accident is about 10 times lower than its activity released during the Chernobyl accident. The maximum total release rates per hour are of the same order of magnitude. In both cases caesium radioisotopes and partly strontium in case of the Chernobyl accident are going to pose threat for decades. While plutonium radioisotopes and 241 Am will pose a significant threat in the vicinity of the Chernobyl accident for hundreds or thousand of years, it seems at least at present this is not the case for the Fukushima site. Although some plutonium radioisotopes, 241 Am and curium radioisotopes in the soil have been reported. 1 INTRODUCTION The nuclear accident in Japan after the earthquake and tsunami on March 11, 2011 was after the Chernobyl accident in 1986 in Ukraine, the major nuclear accident in the last decades. Both accidents revealed the need for reevaluation of safety standards used in all phases of a nuclear power plant (NPP), i.e. during its siting, construction, maintenance and operation including emergency preparedness as well as during its decommissioning. Regarding the experiences after the Chernobyl accident the analysis of impacts on the environment as well as of lessons learnt from the nuclear crisis in Japan will take years. The reasons regarding both accidents are very different. Namely, the Chernobyl accident was not related to natural disaster, as it is in the case of the Fukushima nuclear accident. Both nuclear accidents are categorised at the highest level, i.e. level 7, on the IAEA INES scale. This level requires major release of radioactive material with widespread health and environmental effects requiring implementation of planned and extended countermeasures as given in [1]

2 107.2 The release of material from a nuclear site is one of the main parameters when the nuclear accident is studied. In the last 25 years, the Chernobyl accident was extensively studied from different perspectives. For example, the impacts on health of liquidators and the population living close to the site are published in [2, 3, 4]. In addition, the radiological impacts and impacts on nuclear safety of the OECD countries given in [5, 6] were analysed. In addition, the substantial influence of the accident on the management of emergency preparedness as well as on the other fields of nuclear safety was evident very soon after the accident as given for example in the publication from 1991 [7]. The OECD also focused on stakeholders involvement during and after the nuclear accident [8]. As a result, huge amounts of analysed data regarding the Chernobyl accident are available. This is not the case when the Fukushima accident in 2011 is studied. First analyses of the accident are available [9, 10]. Not only a lack of time distance is present in order to analyse data, but also it is evident that during and after the accident the operator and regulatory authorities were not able to obtain all data needed for the evaluation of the scope of the accident. Japan rated the accident as level 7 on the INES scale on April 11, 2011 not due to the escalation of the accident, which already started on March 11, 2011 but because the analysis of released radioactive material was available. Taking into account the fact that the release of radioactive material is one of the driving forces of emergency countermeasures, the releases should be known as soon as possible in order to optimise the countermeasures. 2 DISCHARGES DURING A NUCLEAR ACCIDENT Although a list of accidents causing either contamination of the environment or exposure of people or both is large, a list of nuclear accident categorised at INES level 4 or more are rare. As a result limited knowledge was gained by such accidents which also happened in very different nuclear facilities and under very different circumstances. For example, the Kyshtym accident in 1957 was caused by an explosion of high activity waste tank resulting in significant release of radioactive material to the environment while Three Mile Island accident in 1979 resulted in severe damage to the reactor core happened during normal operation. As a rule numerous causes contributed to accidents and many lessons learned can be gained from each specific accident. The characteristics of discharges to the environment, e.g. radioactive source term, during the nuclear accident depend on many factors. Some of them have a major role. One of the main factors is the accident itself and the other is the type of a NPP or facility. Till today six types of reactors have emerged as the designs used for a production of commercial electricity namely, PWR, BWR, CANDU, RMBK, AGN and Magnox, among them the PWR type is the most widely used. In addition to reactor types mentioned socalled fast neutron reactors have been developed to full scale demonstration stage as reported in [11]. For all accident scenarios and consequently emergency preparedness a radioactive source term for a specific NPP must be well known in advance. Source terms are related to all systems with radioisotopes in an NPP, e.g. reactor core as well as spent fuel pit. Fission product and activation inventory of a reactor depends on a type of reactor as well as on other parameters. For example if releases occur during the operation a set of released radioisotopes can be significantly different from releases one day after a shutdown, e.g. shortlived fission products as Br radioisotopes will not be present in systems one day after a reactor shutdown. Generic inventory of radionuclides are available as for example in [12] where inventory of reactor coolant as well as a core of a PWR and BWR is given. Table 1 shows predicted radioisotopes of source terms for light water reactors and RMBK based on data given in [12, 13, 14] where also details regarding specific radioisotope are given. Radioisotopes of an element have very

3 107.3 different halflife, e.g. 85 Kr has a half life of 10.8 years while 90 Kr only 32 s. Associated risk given in the table is related only to radioisotopes whose releases require countermeasures. In addition, radioisotopes with halflives more than one year are mentioned in the column 4 of the table. The radionuclides are listed according to the order of appearance in a typical nuclear accident. Namely, as a rule noble gasses escape first while transuranic elements in a form of particulates will escape at last. Only the most important radionuclides are considered. The elements, which are very volatile, can pose a threat in a distance of a few hundreds of kilometres while transuranic elements pose a significant threat in a distance of a few tens of kilometres. Table 1: Generally expected releases of the most important radioisotopes in a nuclear accident associated with a nuclear reactor and associated risk, which requires countermeasures. The radionuclides are listed according to the order of the appearance in a nuclear accident. Volatility Radioisotopes Associated Risk Radionuclides Posing Long Term Associated Risk (halflife of radioisotopes more than 1 year) Gaseous Highly Volatile Fission Products Moderate Volatile Fission Products Refractory Elements including Fuel Particles Noble gasses Xe, Kr Iodine Caesium Bromine Tellurium Strontium Barium Ruthenium Cerium Transuranic elements Slight health hazard associated with external exposure High health hazard associated with internal exposure to thyroid gland and to external exposure 137 Cs poses internal exposure hazard to the whole body as well as external exposure hazard, while 134 Cs poses only external exposure hazard External exposure hazard causing moderate health risk External exposure hazard and health hazard associated with 132 I daughter of 132 Te 89 Sr, and 90 Sr pose internal exposure hazard to bone and lung. 140 Ba poses internal exposure hazard to bone and lung. 106 Ru poses internal exposure hazard to kidney and gastro intestinal tract. 144 Ce poses internal exposure hazard to bone and lung. External and internal contamination can pose a threat. High radiotoxicity is associated with transuranic 137 Cs (halflife a), 134 Cs (halflife 2.06 a ) 90 Sr (halflife a) Some radioisotopes have halflives of several thousands years.

4 107.4 elements. Actual releases strongly depend on the socalled scenario map, e.g. plant, core and confinement states. For a particular NPP scenario the maps are studied in details. The study is based on the scenario map and an accident initiator, e.g. station blackout. The discharges of a particulate radioisotope in a specific chemical form from a specific system of the NPP or other nuclear facility can be predicted using a specific scenario, e.g. temperature of the core and a time interval during which a predefined percentage of a core is not covered determine the release of a specific radioisotope. Such estimations are well known in the literature and are a part of emergency preparedness of NPPs as given for example in [15]. Four stages of core releases are identified, namely gap releases, meltdown releases, vaporisation and oxidation releases [16]. As mentioned above as a rule, noble gaseous radioisotopes are the first radioisotopes, which will be released. They are followed by iodine radioisotopes. The escalation of the accident results in releases of caesium and rubidium, and later in releases of tellurium and strontium radioisotopes followed by plutonium and other radioisotopes. The details of studies of nuclear accidents when the core of the reactor is involved are given elsewhere [12]. The number of units at a site involved in the accident is important. For example in 1957 in the Windscale accident as well as in the Chernobyl accident in 1986, one reactor was involved. In the Fukushima accident multiple BWR reactors with their systems were involved But in addition to predicted discharges the realistic discharges also strongly depend on conditions of an NPP or nuclear facility before the accident, including conditions of all systems and not only the condition of the reactor itself, e.g. condition of the spent fuel pit, radioactive waste facility, ventilation systems. The Chernobyl accident involved the reactor in operation while tsunami hit the Fukushima NPPs, which were shut down, some of them for maintenance. Today after the Fukushima accident reevaluation of safety conditions at NPPs is taking place. Many operators of NPPs focus on the condition of spent fuel pit at a NPP site, the characteristics and behaviour of the fuel in it and the systems connected to a pit. They study the behaviour mentioned under extreme conditions posed by an accident or a combination of accidents. The discharges can be further influenced by actions of the operator in the course of an accident or after it. For example, in 1979 during the Three Miles Island accident the operators did not realise that a loss of cooling water was present for about 2.5 hours. As a result, the first major nuclear accident followed. In case of the Chernobyl accident, literature e.g. INSAG publication given in [17]. reports on many actions conducted by the operators or liquidators during the accident that limited the releases and the further escalation of the accident. Some of these actions threatened lives of the actors. Nevertheless, it should be pointed out that the amounts of the released materials as well as their characteristics are only one factor influencing the radiological and environmental impact of the accident. The influence of discharges during and after the nuclear accident strongly depends on the weather conditions and on geography in general, e.g. the same releases from the crippled nuclear submarine far away from the populated areas can have much less impact on the health and the environment as the releases from an NPP sited close to a town. While the Fukushima accident as well as the Windscale accident occurred at the coast of an ocean, the Chernobyl accident occurred in the middle of a continent. Other factors can be divided into three groups. Namely, factor, related to preaccidental conditions not controlled by the operator, emergency countermeasures and postaccidental conditions not controlled by the operator. Preaccidental conditions are for example a lack of stable iodine in a daily diet or age groups of the population affected living in the vicinity of an accident. Radiological and environmental impacts also strongly depend on countermeasures, e.g. timely

5 107.5 evacuation or ingestion prohibition of milk contaminated with 131 I. Postaccidental factors can be also taken into account, e.g. transfer of radionuclides from soil to foodproduction system, fires of contaminated forests, contamination of aquatic systems etc. It should be mentioned that as a rule discharges during the nuclear accident are not measured while this is not the case during the normal operation of a nuclear facility. 3 DISCHARGES FROM THE CHERNOBYL AND FUKUSHIMA ACCIDENT Comparisons of the discharges from the Chernobyl and the Fukushima accidents are based on data available from open literature. Although 25 years passed from the Chernobyl accident, even in 2011 the scientific literature, i.e. UNSCEAR Report 2008 [4], mentions that only current best estimates of radionuclide releases are given. As expected the Fukushima accident data are still not final [18], i.e. only trial estimations are given and it can take years to gain the data of the radionuclide source term. Nevertheless, the available data on discharges as well as their comparison can give deeper insight to understanding of radiological and environmental consequences of the accident. Some very important differences between both discharges should be taken into account. a. Namely, as published for example in [4] during the Chernobyl accident a mixture of radionuclides into the atmosphere was released over a period of about 10 days, i.e. during an intense graphite fire which started on 26 April, On the contrary, the releases into the atmosphere from the Fukushima site started on March 11, 2011 and releases existed over a prolonged period of time, e.g. several weeks. b. During the Chernobyl accident materials in a form of hot gases, condensed particles and fuel particles were released into the atmosphere. The releases of the Fukushima accident do not include only releases into the atmosphere, but also releases into the sea due to the outflows as given in the Report of the Japanese Government to the IAEA Ministerial Conference on Nuclear Safety [10]. Furthermore, the operator also intentionally discharged radioactive water into the sea in order to empty a storage and pits with radioactive water, which was the result of the accident. The operator needed empty storage and pits in order to store highly radioactive water, which was a result of the accident. c. While the releases during the Chernobyl accident are related only to unintentional releases into the atmosphere, the operator of the Fukushima NPPs, i.e. TEPCO, used discharges of radioactive water from Units 5 and 6 into the sea as remediation actions during the course of the accident as well as from Central Radioactive Waste Disposal Facility. The estimated amount is 1.5 E+11Bq and the total volume is tons. d. On a long term, i.e. hundreds to thousands of years the only discharged radionuclides of interest from the Chernobyl accident will be the plutonium isotopes and 241 Am [4], i.e. radioisotopes of plutonium from nuclear fuel itself and 241 Am originating from a fuel itself but mainly produced by the decay of 241 Pu. Over the next few decades, the most important radioisotopes will be 137 Cs and partly also 90 Sr in a nearby zone. On the contrary, the reports from Japan do not confirm that nuclear fuel from the Fukushima NPPs was released from the nuclear site in a large amount during the course of the accident. As a result, it seems at least at present that all radioisotopes posing a significant threat from the Fukushima accident will substantially decay in the environment relatively soon i.e. in a next decades. The 241 Am from the Chernobyl accident

6 107.6 is increasing with time and will reach the highest activity of all remaining radionuclides after 320 years [4]. 3.1 Discharges into the Atmosphere Table A1 in UNSCEAR Report 2008 from 2011 [4] gives the best estimates of the total releases of principal radionuclides during the Chernobyl accident including 25 radioisotopes altogether. Taking data from a preliminary investigation of the Fukushima accident [10, 16] a comparison of reported releases into the atmosphere of both accidents is given in Table 2. Groups of radionuclides given in the table are based on a grouping system given in the Table A1 already mentioned. Regarding the data related to the Fukushima accident, some data for the specific radionuclides are missing in the reports. The data are not given in [10], not because such radionuclides were not discharged, but the data are not available yet in open literature. For example during the Fukushima accident noble gases were released, but their amount is still not reported in official Japanese report, although a preliminary assessment is for example given by the IRSN and the total assessed activity is around 2000 PBq [19]. Regarding 131 I the release of this radionuclide during the Fukushima accident, i.e. in the interval 130 to 160 PBq, was one order of magnitude lower than the release during the Chernobyl accident were about 1760 PBq was released. The reported value for 137 Cs discharge from the Fukushima accident is in the interval from 6.1 to 15 PBq while the value for the Chernobyl accident is about 85 PBq. Table 2: Comparison of reported releases into the atmosphere in the course of the Fukushima and the Chernobyl accident [4, 10, 16]. Radioisotope Fukushima Accident Releases [PBq] Chernobyl Accident Releases [PBq] Ratio Chernobyl/ Fukushima Release Noble Gases Volatile Elements Elements with Intermediate Volatility Refractory Elements (including fuel particles) a 85 Kr NR 33 NA 133 Xe NR NA 132 Te Detected ~ NA 131 I ~ I NR 910 NA 134 Cs NR ~ 47 NA 136 Cs NR 36 NA 137 Cs ~ Others NR 1186 NA 89 Sr Small amount ~ 115 NA 90 Sr detected ~ 10 NA outside of a plant 103 Ru NR > 168 NA 106 Ru NR >73 NA 140 Ba NR 240 NA 98 Zr, 99 Mo, Small amount of ~ 693 c NA 141 Ce, 144 Ce, plutonium 239 Np, 238 Pu, radioisotopes 239 Pu, 240 Pu, detected outside of 241 Pu, 242 Pu, a plant b 242 Cm

7 107.7 a The released amount of 241 Am was estimated to be negligible, but after 320 years it will have the highest activity of all radioisotopes originated from the Chernobyl accident in the environment due to the decay of 241 Pu. b Reports of the TEPCO from June 2011 confirmed releases of 241 Am, and 242 Cm, 243 Cm and 244 Cm. The ratio of 241 Am, 242 Cm, 243 Cm and 244 Cm to 238 Pu in samples is almost the same as average nuclide density ratio of fuel of Units 1 and 3 [20]. c 400 PBq is the activity of 239 Np and 84 PBq is the activity of 95 Zr and 141 Ce each. Abbreviation NR is used for not reported data and NA for not available. Until today, i.e. September 2011, intensive research is going on in order to estimate a total release during the Fukushima accident and to assess the impact of the accident on the environment and the general population [18, 21, 22]. For example, in a discussion paper given in [21], 133 Xe and 137 Cs were estimated showing that the total release of 133 Xe was about 16.7 E03 PBq, i.e. a factor of 2.5 of the Chernobyl release and consistent with the IRSN report, while the total release of 137 Cs was estimated to be around 36 PBq. The Central Institute for Meteorology and Geodynamics (ZAMG) from Austria also published estimations of atmospheric releases based on the CTBTO station measurements [22]. For example, the reported estimated value of emission during the first week of the accident is for 131 I in the interval from 10 PBq to 700 PBq and from 1 to 70 PBq for 137 Cs. The final results related to atmospheric releases are not available yet and it can take years to estimate them with the sufficient accuracy. Figure 1 taken from the official Japanese report [10] shows releases rate of 131 I and 137 Cs into the atmosphere from the Fukushima site from March 12, till April 6, The maximum values of release rates for 131 I are up to 10 PBq/h and up to one PBq/h for 137 Cs. Taking into account the reported data related to Chernobyl accident from [4] the total initial release in the course of the Chernobyl accident was the highest one on the April , namely PBq. The average release rate in that day was 3035 PBq/h. This value can be compared with maximum values of release rates for Fukushima accident mentioned before. It can be concluded that the maximum release rates of both accidents are of the same order of magnitude. Figure 1: Release rates of 131 I and 137 Cs into the atmosphere from the Fukushima site from March 12 till April 6, 2011 [10]. Atmospheric releases resulted in a contaminated of ground and countermeasures, e.g. evacuation of people and control of food and feedingstuffs, were put in place. Atmospheric releases also spread over the sea and a partial fallout followed. Such deposition can not be analysed in the same way as a deposition on a ground that can stayed unchanged for years. The stimulation of the deposition on the sea from the atmospheric releases can be estimates as

8 107.8 a function of time dependant releases and weather conditions, but in the vicinity of the plant the deposition mentioned can be of the same order of magnitude as the deposition of radionuclides at the ground. In addition, a part of radionuclides from the atmospheric releases, which contaminated the soil and rivers, also reached the sea after the rainout. 3.2 Discharges into the Aquatic System Regarding the reported data during the Chernobyl accident no direct discharges into the aquatic system occurred although due to the aquatic system near the nuclear site, i.e. Dnepr river basin, the contamination of water was and is still a substantial threat, which also required major countermeasures. As already pointed out during the Fukushima accident two types of discharges into the see occurred. Namely, two unintentional outflows occurred and controlled, i.e. intentional, discharges of contaminated radioactive water took place. One of the outflows mentioned occurred due to the crippled Unit 2 in April 2011 and the other due to the crippled Unit 3 in May As reported in [10] 131 I, 134 Cs and 137 Cs were measured but due to the lack of data only the estimation of the total activities are given, namely 4.7 PBq regarding the first outflow and 20 TBq related to the second one. While during the first outflow all radioisotopes discharged had the activity of the same order of magnitude, i.e. PBq, during the later outflow the total activity of 131 I discharged was an order of magnitude lower than the activity for each caesium radionuclides. Controlled discharges were a part of countermeasures since a huge amount of highly radioactive water was present during the accident. In order to store and later process this water the operator released less contaminated water from the Central Radioactive Waste Disposal Facility and subdrain pits of the Units 5 and 6 into the water. Table 3 shows available data [10] related to discharges into the sea during the Fukushima accident. Table 3: Reported discharges into the sea during the Fukushima accident Source Estimated Total Volume of the Release [m 3 ] Estimated Total Activity [Bq] Unintentional Outflow 1 from the Unit E+15 Discharge Outflow 2 from the Unit E+13 Intentional Discharge Central Radioactive Waste Disposal Facility E+11 Subdrain pits of Units 5 and The detailed data regarding a set of all radionuclides discharged in the sea is not available at the time of writing the article. As mentioned above the direct discharges to the sea are not the only pathway radionuclides from the Fukushima Daiichi NPP reaching the sea. The IRSN report [23] gives the measurement results of contamination of the sea based on the sampling of the sea water. As reported a list of radionuclides was found e.g. 131 I, 137 Cs, 129m Te, 140 Ba, 105 Ru, 99 Mo and 58 Co. Details containing also concentrations of radionuclides found are given in [23]. Contamination of sea water caused restriction related to fishing and other activities close to the crippled NPP. In addition, the control of contamination of fishes and marine products from the FAO Major Fishing Areas 61, 67, 71 and 77 was established.

9 CONCLUSIONS Although the Fukushima and the Chernobyl accidents are both characterised on the level 7 of the INES scale, the important differences can be identified, based on the preliminary data of the Fukushima accident. While the Chernobyl accident occurred in hours the discharges from the site took place for about ten days, the Fukushima accident escalated slower, but with a much longer time of discharges. While for the Chernobyl accident the time scale of discharges of particular radioisotopes is not known well, the development of the escalation of the Fukushima accident and related releases was predicted based on the characteristics of the nuclear site. The countermeasures taken in order to reduce discharges were very different in both cases. Namely, during the Chernobyl accident the protective actions on the site of the nuclear facility took place without any delay while countermeasures for the general public delayed for a few days. The first evacuation around the Fukushima Daiichi NPP was initiated on a day of the tsunami. During the Fukushima accident discharges were released into the atmosphere as well as into the sea, partly also intentionally. During the Chernobyl accident no discharges were reported into the aquatic system. Regarding the discharges into the air some similarities can be noted. In both cases 131 I was the major radionuclide posing the immediate threat. The activity of the atmospheric release of this radionuclide during the Fukushima accident is about 10 times lower than its activity released during the Chernobyl accident. The maximum total release rates per hour are of the same order of magnitude. In both cases caesium radioisotopes and partly strontium in case of the Chernobyl accident are going to pose threat for decades. While plutonium radioisotopes and 241 Am will pose a significant threat in the vicinity of the Chernobyl accident for hundreds or thousand of years, it seems at least at present that such threat is not present at or around the Fukushima site, although some plutonium radioisotopes, 241 Am and curium radioisotopes in the soil have been reported. REFERENCES [1] IAEA, INES: The International Nuclear and Radiological Event Scale User's Manual, 2008 Edition, IAEA, Vienna, 2009, available at [2] M. Balonov et al., Update of Impacts of the Chernobyl Accident: Assessment of the Chernobyl Forum ( ) and UNSCEAR ( ), Proc. Int. Conf. Third European IRPA Congress, Helsinki, Finland, June 1318, Nordic Society for Radiation Protection, 2010, available at P10.pdf. [3] United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Effects of Ionising Radiation, UNSCEAR 2000, Vol. I and II, Annex J, UN, New York, [4] United Nations Scientific Committee on the Effects of Atomic Radiation, Sources and Effects of Ionising Radiation, UNSCEAR 2008, Vol. II, Annex D, UN, New York, [5] OECD, NEA, The Radiological Impact of the Chernobyl Accident in OECD Countries, OECD, Paris, [6] OECD, NEA, Chernobyl and the Safety of Nuclear Reactors in OECD Countries, OECD, Paris, 1987.

10 [7] French Nuclear Society (SFEN), Soviet Nuclear Society, Proc. Int. Conf. Nuclear Accidents and the Future of Energy, Lessons Learned from Chernobyl, Paris, France, April 1517, ENS, [8] NEA, OECD, Stakeholders and Radiological Protection: Lessons from Chernobyl 20 Years After, CRPPH Report, NEA No. 6170, 2006, OECD. [9] IAEA International Fact Finding Expert Mission Of the Fukushima DaiIchi NPP Accident following the Great East Japan Earthquake and Tsunami, May 24 June 2, 2011, IAEA, available at pub.iaea.org/mtcd/meetings/pdfplus/2011/cn200/documentation/cn200_final FukushimaMission_Report.pdf. [10] 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 [11] Institution of Engineering and Technology, Nuclear Reactor Types, IET, 2008, available at [12] IAEA, Generic Assessment Procedures for Determining Protective Actions During a Reactor Accident, IAEATECDOC955, Vienna, IAEA,1997. [13] Lituanian International Nuclear Centre, Ignalina Handbook, Kaunas Lithuanian Energy Institute, 1997, available at [14] M. Rahgeb, Fukushima Earthquake and Tsunami Station Blackout, and reference therein available at ower%20engineering/fukushima%20earthquake%20and%20tsunami%20station%20bl ackout%20accident.pdf. [15] NRC, Regulatory Guide Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors, NRC, 2000 available at [16] P. F. Caracappa,»Fukushima Accident: Radioactive Releases and Potential Dose Consequences«, ANS Annual Meeting, June 2630, Hollywood, USA, 2011, available at [17] IAEA, Safety Series No. 75, INSAG7, The Chernobyl Accident: Updating of INSAG1, 1992, Vienna, IAEA, available at [18] CTBTO, Book of Abstracts. Science and Technology 2011, Session on the 11 March 2011 Japanese Event and its Aftermath, CTBTO, 2011, available at [19] IRSN, IRSN Report, Assessment of Radioactivity Released by the Fukushima Daiichi Nuclear Power Plant (Fukushima I) through 22 March 2011, March 22, 2011, IRSN,

11 available at [20] TEPCO, Attachment 3, Fukushima Daiichi Nuclear Power Station: Am and Cm Analysis Result in the Soil, July , TEPCO, available at [21] A. Stohl, P. Seibert, G. Wotawa, D. Arnold, J. F. Burkhart, S. Eckhardt,, C. Tapia, A. Vargas,, T. J. Yasunari, Xenon133 and Caesium137 Releases into the Atmosphere from the Fukushima DaiIchi Nuclear Power Plant: Determination of the Source Term Atmospheric Dispersion, and Deposition, ACDP, 11, 2011, , available at [22] ZAMG, Accident in the Japanese NPP Fukushima: Spread of Radioactivity / Weather today not favourable/ by comparison with CTBTO radioactivity data, ZAMG estimates high emissions of Iodine and Caesium during the first accident week / Measurements show Hemisphericscale spread of radioactivity (Update: 1. April :00), 16. Apil 2011, ZAMG, available at 01_1400_E1.pdf [23] IRSN Report, Impact on Marine Environment of Radioactive Releases, April 4, 2011, IRSN, available at Accident_ImpactonmarineenvironmentEN_ pdf