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Sato, Hiroyuki; Nishida, Akemi; Furuya, Osamu*; Muramatsu, Ken*; Itoi, Tatsuya*; Takada, Tsuyoshi*; Tanabe, Masayuki*; Yamamoto, Tsuyoshi*
no journal, ,
The proposed research aims to establish a probabilistic risk assessment method for high temperature gas-cooled reactors fully utilizing their design and safety characteristics. The method will be developed for the incorporation of a graded approach as well as a component failure evaluation model using the operation and maintenance experience in the high temperature engineering test reactor into an accident frequency analysis. In addition, a source term evaluation method considering failures in core graphite components will be developed.
Nagai, Haruyasu
no journal, ,
no abstracts in English
Osaka, Masahiko; Miwa, Shuhei; Nakajima, Kunihisa; Di Lemma, F. G.; Suzuki, Chikashi; Nagase, Fumihisa
no journal, ,
Chemical behavior of fission product (FP) are of crucial importance for the improvement of FP release and transport behavior under the severe accident. Fundamental research on FP sorption behavior and evaluation of FP chemical composition in the reactor are introduced.
Nagaishi, Ryuji; Motooka, Takafumi; Yamagishi, Isao; Inoue, Masao; Matsumura, Taichi
no journal, ,
no abstracts in English
Satou, Yukihiko*; Sueki, Keisuke*; Sasa, Kimikazu*; Minowa, Haruka*; Yoshikawa, Hideki; Fujiwara, Kenso; Nakama, Shigeo
no journal, ,
We separated radioactive particles from soil and dust sample obtained around Fukushima Dai-ichi Nuclear Power Plant. Separated all particles can categorize unit-1 and unit-2 origin. And 
Sb was detected from unit-1 origin samples. Moreover, radioactive particle was made up 80 weight percent silica.
Hirouchi, Jun; Takahara, Shogo; Watanabe, Masatoshi; Munakata, Masahiro
no journal, ,
no abstracts in English
Watanabe, Masatoshi; Takahara, Shogo; Hirouchi, Jun; Munakata, Masahiro
no journal, ,
no abstracts in English
Suzuki, Masashi; Yoshida, Eiichi; Imamura, Hiroaki; Amano, Katsunori; Shimoyama, Kazuhito
no journal, ,
no abstracts in English
Yamane, Yuichi
no journal, ,
For criticality accidents due to instantaneous insertion of reactivity to the system with non-linear temperature reactivity feedback, an equation has been derived based on one-point kinetics, by which equation the total fission energy is expressed as a function of initial excess reactivity and other kinetics parameters. The results obtained by using the equation and one-point kinetics code, AGNES, were compared to each other to show that the difference between them decreased with increase of excess reactivity from several ten % to 4%.
Furuta, Takuya; Takahashi, Fumiaki
no journal, ,
Precise radiation dose assessment for residents is desired for radiation protection under contaminated environment due to the accident at Fukushima Daiichi Nuclear Power Station. Evaluation of dose rates inside houses is important for this assessment as well as those outside houses by monitoring because people stays inside houses for a large part of a day. We have studied radiation dose reduction inside buildings standing on isolated flat field as the typical data. However, radiation dose reduction for houses in urban area may be different from that for isolated houses because of influence of neighboring buildings. We therefore simulated a situation of infinitely aligned houses virtually by using reflection walls placed at the boundary of geometry containing a house. The radiation dose rate inside this house was computed by transporting radiations using PHITS. We found that dose rates per unit radiation concentration inside the house was lowered as the distance between houses was reduced because of shielding effect by neighboring houses and reduction of radiation source contributed to the dose rate.
Koura, Hiroyuki; Chiba, Satoshi*
no journal, ,
no abstracts in English
Akaoka, Katsuaki; Oba, Masaki; Miyabe, Masabumi; Wakaida, Ikuo
no journal, ,
For quantitative analysis of the fuel debris using Laser Induced Breakdown Spectroscopy (LIBS), great deal of analysis and identification of spectra are necessary. Therefore, we tried "the analysis of the LIBS spectrum by the least-squares method" as quantitative analysis without identification and analysis of the spectra. As a result, the calibration curves for quantitative analysis could be got without them.
Iguchi, Yukihiro; Yanagihara, Satoshi*; Tezuka, Masashi; Koda, Yuya; Kato, Yasuaki
no journal, ,
Fugen Decommissioning Engineering Center is promoting Knowledge Management (KM) for the decommissioning in order to transfer knowledge and technology of the employees. One of the approaches is a KM support system by using VR and AR technology based on the 3D-CAD data.
Tsuda, Shuichi; Ogawa, Tatsuhiko; Sato, Tatsuhiko
no journal, ,
While PHITS can perform the transport calculation in the macroscopic geometries larger than 10-6 m, the information of the deposit energy distribution in smaller region is required in the evaluation of the biological effects. Although the deposit energy calculation function based on the track structure simulation in a smaller region has been in progress, the tally is only applied to the calculation in water at present. Therefore, the authors calculated the deposit energy distributions in a tissue equivalent in a micrometer scale including the contribution of the secondary particles produced through nuclear reaction, and compared with the reported experimental data. It is found that the parameters of the productions of the delta rays and the light particles should be appropriately set. These information will be used for the improvement of the microscopic deposit energy calculation function in PHITS.
Sato, Satoshi; Kwon, Saerom; Ota, Masayuki; Ochiai, Kentaro; Konno, Chikara
no journal, ,
In order to validate the nuclear data library of tungsten, integral experiments on tungsten with the DT neutron source at JAEA/FNS were performed over 20 years ago. Some calculated reaction rates underestimated the measured ones in the previous study. Background neutrons scattered in the concrete wall of the experimental room are considered to cause these underestimations. In order to reduce background neutrons, we propose a new experimental assembly and perform a new integral experiment on tungsten with the DT neutron source at JAEA/FNS in this study. A rectangular tungsten assembly of 355 mm in height, 355 mm in width and 507 mm in thickness is covered with Li
O blocks to exclude background neutrons which might affect the measured data. Using activation foils and micro fission chambers, we measure the reaction rates of the 
Nb(n,2n)
Nb, 
Al(n,
)
Na, 
In(n,n')
In, 
Au(n,
)
Au, 
W(n,)
W, 
U(n,f) and 
U(n,f) reactions. We analyze the experiment by using MCNP5-1.40 with the recent nuclear data libraries, ENDF/B-VII.1, JEFF-3.2 and JENDL-4. All the calculation results generally show good agreement with the measured ones in this experiment. It is concluded that the nuclear data of tungsten have no problem.
Kadowaki, Masanao; Terada, Hiroaki; Katata, Genki; Furuno, Akiko; Nagai, Haruyasu
no journal, ,
In case of a nuclear accident or radiological emergency, a simulation with numerical models is a powerful means in order to predict distributions of the polluted air. Although a particle model that WSPEEDI has introduced shows advantage in the synoptic scale, it costs computationally because of the large amount of airborne particles. Moreover, the model has problems with uncertainties in the calculations on long range, due to exponentially increasing errors. For the reason, in this study the atmospheric transport modeling with a finite difference method: GEARN-FDM is proposed in order to improve WSPEEDI. The advection and diffusion in the atmosphere were calculated by using a mass conservative and monotonic manner scheme (Walcek, 2000) and Crank-Nicolson method, respectively. The distributions of tracer were good agreement with the first ETEX measurements. In this session the validation and comparison will be discussed.
Kwon, Saerom; Ota, Masayuki; Sato, Satoshi; Ochiai, Kentaro; Konno, Chikara
no journal, ,
In the last annual meeting of AESJ, we had presented that the calculated results related to low energy neutrons drastically underestimated the measured ones in the new benchmark experiment on copper. In order to find out reasons of the underestimation, the copper data in the latest nuclear data libraries, ENDF/B-VII.1, JEFF-3.2 and JENDL-4.0 were examined, which showed that the cross section data of the elastic scattering and capture reaction in the resonance regions were different among the nuclear data libraries. Then we analyzed the experiment with a nuclear data library modified for the cross section data of the elastic scattering and capture reaction. As a result, we found out that the cross section data of the elastic scattering and capture reaction should be reassessed in the resonance region in order to improve the drastic underestimation.
Ota, Masayuki; Kwon, Saerom; Ochiai, Kentaro; Sato, Satoshi; Konno, Chikara
no journal, ,
In our integral experiment on molybdenum with DT neutrons at JAEA/FNS, the ratios of the calculated dosimetry reaction rates and fission rates to the experimental ones generally decreased with the increasing distance from the front surface of the molybdenum assembly. In order to specify reasons of the underestimation we carried out detailed analyses of this experiment. As a result, it is concluded that the (n,2n) cross section data for the Mo stable isotopes in JEFF-3.2 are more appropriate than those in JENDL-4.0 and the (n,) cross section data of the Mo stable isotopes except for 
Mo in JENDL-4.0 are larger.
Taniguchi, Yoshinori; Udagawa, Yutaka; Amaya, Masaki
no journal, ,
no abstracts in English
Ishimi, Akihiro; Katsuyama, Kozo; Akasaka, Naoaki; Misawa, Susumu*
no journal, ,
no abstracts in English