Zhang, T.*; Funakoshi, Kanji*; Liu, X.*; Liu, W.*; Morita, Koji*; Kamiyama, Kenji
Annals of Nuclear Energy, 150, p.107856_1 - 107856_10, 2021/01
Hosoda, Masahiro*; Nugraha, E. D.*; Akata, Naofumi*; Yamada, Ryohei; Tamakuma, Yuki*; Sasaki, Michiya*; Kelleher, K.*; Yoshinaga, Shinji*; Suzuki, Takahito*; Rattanapongs, C. P.*; et al.
Science of the Total Environment, 750, p.142346_1 - 142346_11, 2021/01
The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h and 1109 nGy h. Indoor radon concentrations ranged from 124 Bq m to 1015 Bq m. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.
Matsuda, Hiroki; Iwamoto, Hiroki; Meigo, Shinichiro; Takeshita, Hayato*; Maekawa, Fujio
Nuclear Instruments and Methods in Physics Research B, 483, p.33 - 40, 2020/11
A thick target neutron yield for a mercury target at an angle of 180 from the incident beam direction is measured with the time-of-flight method using a 3-GeV proton beam at the Japan Proton Accelerator Research Complex (J-PARC). Comparing the experimental result with a Monte Carlo particle transport simulation by the Particle and Heavy Ion Transport code System (PHITS) shows that there are apparent discrepancies. We find that this trend is consistent with an experimental result of neutron-induced re- action rates obtained using indium and niobium activation foils. Comparing proton-induced neutron-production double-differential cross-sections for a lead target at backward directions between the PHITS calculation and experimental data suggests that the dis- crepancies for our experiments would be linked to the neutron production calculation around 3 GeV by the PHITS spallation model and/or the calculation of nonelastic cross-sections around 3 GeV in the particle transport simulation.
Kubo, Kotaro; Zheng, X.; Tanaka, Yoichi; Tamaki, Hitoshi; Sugiyama, Tomoyuki; Jang, S.*; Takata, Takashi*; Yamaguchi, Akira*
Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.308 - 315, 2020/10
Dynamic probabilistic risk assessment (PRA) is a method for improving the realism and completeness of conventional PRA. However, enormous calculation costs are incurred by these improvements. One solution is to select an appropriate sampling method. In this paper, we applied the Monte Carlo, Latin hypercube, grid-point, and quasi-Monte Carlo sampling methods to the dynamic PRA of a simplified accident sequence and compared the results for each method. Quasi-Monte Carlo sampling was found to be the most effective method in this case.
Ono, Masato; Hanawa, Yoshio; Sonobe, Hiroshi; Nishimura, Arashi; Sugaya, Naoto; Iigaki, Kazuhiko
JAEA-Technology 2020-010, 14 Pages, 2020/09
In response to new standard for regulating research and test reactor which is enforced December 18, 2013, it was carried out assessment of the probability of aircraft crashing for HTTR. According to assessment method provided in the Assessment Criteria of the Probability of Aircraft Crashing on Commercial Power Reactor Facilities, assessment was conducted targeting reactor building, spent fuel storage building and cooling tower. As a result, it was confirmed that the probability was 5.9810, which is lower than the assessment criteria 10.
Togawa, Orihiko; Hayakawa, Tsuyoshi; Tanaka, Tadao; Yamamoto, Kazuya; Okuno, Hiroshi
JAEA-Review 2020-017, 36 Pages, 2020/09
In 2010, the government of Japan joined the Response and Assistance Network (RANET) of the International Atomic Energy Agency (IAEA), in order to contribute to offering international assistance in the case of a nuclear accident or radiological emergency. At that occasion, the Japan Atomic Energy Agency (JAEA) was registered as the National Assistance Capability (NAC) having resources capable of the External Based Support (EBS) in the following seven areas: (1) aerial survey, (2) radiation monitoring, (3) environmental measurements, (4) assessment and advice, (5) internal dose assessment, (6) bioassay and (7) dose reconstruction. After the registration, three inquiries were directed to the JAEA about a possibility of its support. However, the JAEA's assistance has not eventually been realized. On the other hand, the JAEA participated almost every year in the international Convention Exercise (ConvEx) carried out by the IAEA in connection with RANET. This report describes an outline of the RANET and related activities of the JAEA for RANET registration and participation in the ConvEx.
Bahtiyar, H.*; Can, K. U.*; Erkol, G.*; Gubler, P.; Oka, Makoto; Takahashi, Toru*
Physical Review D, 102(5), p.054513_1 - 054513_18, 2020/09
Spectrum of the ground state and excited states of charmed baryons was evaluated in the lattice QCD, the first principle of hadronic interaction. We deliver the spectrum of the positive and negative parity baryons with one, two or three charmed quarks. A variational approach was employed by the use of multiple operators with different Dirac matrix configurations and the smearings.
Ishitsuka, Etsuo; Nakashima, Koki*; Nakagawa, Naoki*; Ho, H. Q.; Ishii, Toshiaki; Hamamoto, Shimpei; Takamatsu, Kuniyoshi; Kenzhina, I.*; Chikhray, Y.*; Matsuura, Hideaki*; et al.
JAEA-Technology 2020-008, 16 Pages, 2020/08
As a summer holiday practical training 2019, the feasibility study for nuclear design of a nuclear battery using HTTR core was carried out, and the U enrichment and burnable poison of the fuel, which enables continuous operation for 30 years with thermal power of 5 MW, were studied by the MVP-BURN. As a result, it is clear that a fuel with U enrichment of 12%, radius of burnable poison and natural boron concentration of 1.5 cm and 2wt% are required. As a next step, the downsizing of core will be studied.
Udagawa, Yutaka; Fuketa, Toyoshi*
Comprehensive Nuclear Materials, 2nd Edition, Vol.2, p.322 - 338, 2020/08
JAEA-Data/Code 2020-005, 48 Pages, 2020/07
In order to discuss the technological development and human resource development necessary for the future nuclear fuel cycle, various quantitative analyzes were conducted assuming a wide range of future nuclear power generation scenarios. In the evaluation of quantities, the future power generation of LWR and fast reactor, the amount of spent fuel reprocessing, etc. were assumed, and the amount of uranium demand, the accumulation of spent fuel, plutonium, vitrified waste etc. were estimated.
Terada, Hiroaki; Nagai, Haruyasu; Tanaka, Atsunori*; Tsuzuki, Katsunori; Kadowaki, Masanao
Journal of Nuclear Science and Technology, 57(6), p.745 - 754, 2020/06
We have estimated source term and analyzed processes of atmospheric dispersion of radioactive materials released during the Fukushima Daiichi Nuclear Power Station (FDNPS) accident by the Worldwide version of System for Environmental Emergency Dose Information. On the basis of this experience, we developed an dispersion calculation method that can respond to various needs in a nuclear emergency and provide useful information for emergency-response planning. By this method, if a release point is known, it is possible to immediately obtain the prediction results by applying provided source term to the database of dispersion-calculation results prepared in advance. With this function, it is easy to compare results by applying various source term with monitoring data, and to find out the optimum source term, which was applied for the source term estimation of the FDNPS accident. By performing this calculation with past meteorological-analysis data, it is possible to immediately get dispersion-calculation results for various source term and meteorological conditions. This database can be used for pre-accident planning, such as optimization of a monitoring plan and understanding of events to be supposed in considering emergency countermeasures.
Miwa, Shuhei; Nakajima, Kunihisa; Miyahara, Naoya; Nishioka, Shunichiro; Suzuki, Eriko; Horiguchi, Naoki; Liu, J.; Miradji, F.; Imoto, Jumpei; Mohamad, B. A.; et al.
Mechanical Engineering Journal (Internet), 7(3), p.19-00537_1 - 19-00537_11, 2020/06
We constructed the fission product (FP) chemistry database named ECUME for LWR severe accident. This version of ECUME is equipped with dataset of the chemical reactions and their kinetics constants for the reactions of cesium(Cs)-iodine(I)-boron(B)-molybdenum(Mo)-oxygen(O)-hydrogen(H) system in gas phase, the elemental model for the high temperature chemical reaction of Cs with stainless steel applied as the structural material in a reactor, and thermodynamic data for CsBO vapor species and solids of CsSiO and CsFeSiO for these chemical reactions. The ECUME will provide estimation of Cs distribution due to the evaluation of effects of interaction with BWR control material B and stainless steel on Cs behavior in the Fukushima Daiichi Nuclear Power Station.
Lu, K.; Katsuyama, Jinya; Li, Y.; Miyamoto, Yuhei*; Hirota, Takatoshi*; Itabashi, Yu*; Nagai, Masaki*; Suzuki, Masahide*; Kanto, Yasuhiro*
Mechanical Engineering Journal (Internet), 7(3), p.19-00573_1 - 19-00573_14, 2020/06
Lu, K.; Katsuyama, Jinya; Li, Y.
Journal of Pressure Vessel Technology, 142(2), p.021208_1 - 021208_11, 2020/04
Katsuyama, Jinya; Osakabe, Kazuya*; Uno, Shumpei*; Li, Y.; Yoshimura, Shinobu*
Journal of Pressure Vessel Technology, 142(2), p.021205_1 - 021205_10, 2020/04
no abstracts in English
Sugiura, Yuki; Suyama, Tadahiro*; Tachi, Yukio
JAEA-Data/Code 2019-022, 40 Pages, 2020/03
Sorption behavior of radionuclides (RNs) in buffer materials, rocks and cementitious materials is one of the key processes in a safe geological disposal. This report focuses on updating of JAEA sorption database (JAEA-SDB) as a basis of integrated approach for the performance assessment (PA)-related distribution coefficient (K) setting and development of mechanistic sorption models. K data and their quality assurance (QA) results were updated by focusing on the following systems as potential needs extracted from our recent activities on the K setting and development of mechanistic models, i.e., clay minerals, sedimentary rocks and cementitious materials. As a result, 6,702 K data from 60 references were added and the total number of K values in JAEA-SDB reached 69,679. The QA/classified K data reached about 72% for all K data in JAEA-SDB.
Development Group for LWR Advanced Technology
JAEA-Data/Code 2019-017, 59 Pages, 2020/03
ECUME (ffective hemistry database of fission products nder ultiphase raction) is the database for the analyses of FP chemistry which strongly affects all the FP behaviors in a severe accident (SA) of nuclear facility like LWR. ECUME consists of three kinds of datasets: CRK (dataset for hemical eaction inetics), EM (lemental odel set) and TD (hermoynamic dataset). The present version of ECUME is prepared especially for the more accurate evaluation of cesium and iodine distribution in a reactor and release amount into an environment which should be of crucial importance towards the decommissioning of Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Holdings (1F) and the enhancement of LWR safety after the 1F SA.
Enerugi Rebyu, 40(4), p.19 - 20, 2020/03
The probabilistic Risk Assessment has been recognized to have important role for the safety enhancement of nuclear facilities in Japan. Efforts of developing methodologies and basic data for risk assessment are undertaken actively for NFFs (Nuclear Fuel Facilities) in Japan. The standard for risk assessment for NFFs is consist of simplified assessment detailed one based on the concept of Graded Approach depending on the risk levels of their facilities. Risk-informed application is useful for activities of enhancing safety measures by the licensee rather than in regulatory decision making because of lower risk level of NFFs. The risk assessment has been also required in the periodic safety self-review by the licensees. The correct understanding of significance of risk assessment for safety management of facilities is essential for the risk-informed application. It is key event to apply the risk assessment in the safety self-review and new regulatory inspection system.
Terada, Hiroaki; Nagai, Haruyasu; Tsuzuki, Katsunori; Furuno, Akiko; Kadowaki, Masanao; Kakefuda, Toyokazu*
Journal of Environmental Radioactivity, 213, p.106104_1 - 106104_13, 2020/03
In order to assess the radiological dose to the public resulting from the Fukushima Daiichi Nuclear Power Station accident in Japan, the spatial and temporal distribution of radioactive materials in the environment is necessary to be reconstructed by computer simulations with the atmospheric transport, dispersion and deposition model (ATDM) and source term of radioactive materials discharged into the atmosphere is essential. In this study, we carried out refinement of the source term and improvement of ATDM simulation by using an optimization method based on Bayesian inference with various measurements (air concentration, surface deposition, and fallout). We also constructed the spatiotemporal distribution of some major radionuclides in the air and on the surface (optimized dispersion database) by using the optimized release rates and ATDM simulations which is used for the comprehensive dose assessment by coupling with the behavioral pattern of evacuees from the accident.
Oba, Takashi*; Ishikawa, Tetsuo*; Nagai, Haruyasu; Tokonami, Shinji*; Hasegawa, Arifumi*; Suzuki, Gen*
Scientific Reports (Internet), 10(1), p.3639_1 - 3639_11, 2020/02
Internal doses of residents after the Fukushima Daiichi Nuclear Power Station accident have been reconstructed. In total 896 behaviour records in the Fukushima Health Management Survey were analysed to estimate thyroid doses via inhalation, using a spatiotemporal radionuclides concentration database constructed by atmospheric dispersion simulations. After a decontamination factor for sheltering and a modifying factor for the dose coefficient were applied, estimated thyroid doses were close to those estimated on the basis of direct thyroid measurement. The median and 95th percentile of thyroid doses of 1-year-old children ranged from 1.2 to 15 mSv and from 7.5 to 30 mSv, respectively.