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Journal Articles

Improvement of atmospheric dispersion simulation using an advanced meteorological data assimilation method to reconstruct the spatiotemporal distribution of radioactive materials released during the Fukushima Daiichi Nuclear Power Station accident

Kadowaki, Masanao; Nagai, Haruyasu; Terada, Hiroaki; Katata, Genki*; Akari, Shusaku*

Energy Procedia, 131, p.208 - 215, 2017/12


 Times Cited Count:3 Percentile:88.07

When radioactive materials are released into the atmosphere due to nuclear accidents, numerical simulations that can reproduce temporal and spatial distribution of radioactive materials are useful to provide the information for emergency responses and radiological dose assessment. In this study, we attempt to improve the atmospheric dispersion simulation using an advanced meteorological data assimilation method and reconstruct the spatiotemporal distribution of radioactive materials released due to the Fukushima Daiichi Nuclear Power Station (FDNPS) accident. The atmospheric dispersion simulations were carried out by the Lagrangian particle dispersion model GEARN developed by Japan Atomic Energy Agency. To obtain meteorological fields for GEARN calculation, we used the Weather Research and Forecasting model WRF with meteorological data assimilation using four-dimensional variational method (4D-Var). GEARN calculations of the surface deposition and air concentration of radionuclides were compared with measurements. In the area close to FDNPS, the spatial distribution of the deposition of Cs-137 and I-131 simulated by GEARN agreed with the measured one. The accuracy of modeled deposition in northwest and south directions from FDNPS was particularly improved. This results were mainly attributed to the better reproducibility of wind field by using the meteorological data assimilation with 4D-Var. The improvement of the accuracy of modeled deposition distribution of Cs-137 in the East Japan area was also apparent under the meteorological fields modified by 4D-Var. The information of atmospheric dispersion processes reconstructed in this study is used for updating the existing assessment of radiological dose resulting from the FDNPS accident based on atmospheric simulations by our previous studies. It can also provide useful suggestions to make emergency response plans for nuclear facilities in Japan.

Journal Articles

User interface of atmospheric dispersion simulations for nuclear emergency countermeasures

Hamuza, E.-A.; Nagai, Haruyasu; Sagara, Hiroshi*

Energy Procedia, 131, p.279 - 284, 2017/12

 Times Cited Count:1 Percentile:62.96

In this study we would like to propose a method to use atmospheric dispersion simulations by WSPEEDI for consideration of crisis management on radionuclide dispersion from a nuclear power plant. WSPEEDI can simulate and output crucial information regarding environmental distribution of radionuclides and weather pattern for nuclear emergency countermeasures, thus this study will make use of its output to display the effective information for evacuation planning from a radionuclide dispersion. We will be assembling database of atmospheric dispersion outputs for one year by using WSPEEDI for a nuclear facility, then the database will be analysed to make the summary that has useful information for nuclear emergency managements. WSPEEDI outputs are converted into numeric information showing dispersion characteristics so that users can understand WSPEEDI predictions easily.

Journal Articles

New approach for monitoring of nuclear material in nitric acid solution using $$^{14}$$N(n,$$gamma$$)$$^{15}$$N reaction

Sekine, Megumi; Tomikawa, Hirofumi

Energy Procedia, 131, p.274 - 278, 2017/12

 Times Cited Count:0 Percentile:0.03

The IAEA has proposed in its long-term R&D plan, development of real-time measurement technology for monitoring and verifying nuclear material movement continuously. At a PULEX reprocessing facility, HNO$$_{3}$$ solution with dissolved spent fuel, such as FPs and nuclear materials, flows in pipes and stores in tanks. In order to detect and deter nuclear material being stolen from the process, measuring the 10.8 MeV $$gamma$$ rays emitted by $$^{14}$$N(n,$$gamma$$)$$^{15}$$N reaction activated by spontaneous neutrons might be useful for continuous monitoring of liquid flow. In general, since high dose $$gamma$$ rays emitted from FPs are dominant below 3 MeV, it is expected that the 10.8 MeV peak would not be affected by the FP peaks. As the first step, some kinds of detectors and measurement configuration were analyzed through MCNP based on 10.8 MeV $$gamma$$ rays activated by neutrons from a $$^{252}$$Cf source.

Journal Articles

A Simple method to create gamma-ray-source spectrum for passive gamma technique

Shiba, Tomooki; Maeda, Shigetaka; Sagara, Hiroshi*; Ishimi, Akihiro; Tomikawa, Hirofumi

Energy Procedia, 131, p.250 - 257, 2017/12

 Times Cited Count:0 Percentile:0.03

In the present paper, the $$gamma$$ ray source data was developed for the debris composition based on "best estimates", and the subsequent photon transportation calculation was performed to evaluate the leakage $$gamma$$ ray spectra according to the fuel debris. Since the creation of the line spectrum source requires a great deal, we have developed the relatively simple but accurate enough method to build up $$gamma$$ ray source, coupling of baseline spectra evaluated by ORIGEN2 code and several line spectra of interest. One of the advantages of the method is taking bremsstrahlung X rays into consideration by utilizing the bremsstrahlung libraries of ORIGEN2. The new $$gamma$$ ray source was used to calculate the detector response of HPGe detector and the results was compared as a benchmark with experimental measurement results of irradiated fuel pins. As the result, the simulated $$gamma$$ ray spectrum shape agreed well with the shape of $$gamma$$ ray spectrum obtained by the experiment.

Journal Articles

Adsorption of platinum-group metals and molybdenum onto aluminum ferrocyanide in spent fuel solution

Onishi, Takashi; Sekioka, Ken*; Suto, Mitsuo*; Tanaka, Kosuke; Koyama, Shinichi; Inaba, Yusuke*; Takahashi, Hideharu*; Harigai, Miki*; Takeshita, Kenji*

Energy Procedia, 131, p.151 - 156, 2017/12

 Times Cited Count:8 Percentile:98.02

no abstracts in English

Journal Articles

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Maeda, Makoto; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.

Energy Procedia, 131, p.258 - 263, 2017/12

 Times Cited Count:6 Percentile:94.83

Journal Articles

R&D status in thermochemical water-splitting hydrogen production iodine-sulfur process at JAEA

Noguchi, Hiroki; Takegami, Hiroaki; Kasahara, Seiji; Tanaka, Nobuyuki; Kamiji, Yu; Iwatsuki, Jin; Aita, Hideki; Kubo, Shinji

Energy Procedia, 131, p.113 - 118, 2017/12

 Times Cited Count:18 Percentile:99.79

The IS process is the most deeply investigated thermochemical water-splitting hydrogen production cycle. It is in a process engineering stage in JAEA to use industrial materials for components. Important engineering tasks are verification of integrity of the total process and stability of hydrogen production in harsh environment. A test facility using corrosion-resistant materials was constructed. The hydrogen production ability was 100 L/h. Operation tests of each section were conducted to confirm basic functions of reactors and separators, etc. Then, a trial operation for integration of the sections was successfully conducted to produce hydrogen of about 10 L/h for 8 hours.

Journal Articles

Oxidation characteristics of lead-alloy coolants in air ingress accident

Kondo, Masatoshi*; Okubo, Nariaki; Irisawa, Eriko; Komatsu, Atsushi; Ishikawa, Norito; Tanaka, Teruya*

Energy Procedia, 131, p.386 - 394, 2017/12

 Times Cited Count:5 Percentile:94.83

The chemical behaviors of lead (Pb) based coolants in the air ingress accident of fast reactors were investigated by means of the thermodynamic considerations and the static oxidation experiments for Pb alloys at various chemical compositions. The results of the static oxidation tests for lead-bismuth (Pb-Bi) alloys indicated that Pb was depleted from the alloy due to the preferential formation of PbO in air at 773K. Pb-Bi oxide and Bi$$_{2}$$O$$_{3}$$ were formed after the enrichment of Bi in the alloys due to the Pb depletion. The oxidation rates of the alloys were much larger than that of the steels, and became larger with higher Pb concentration in the alloys. The compatibility of Pb-Bi alloys with stainless steel was worse when the Pb concentration in the alloys became low, since the dissolution type corrosion was promoted by the Bi composition in the alloy. The Pb-Li alloys were oxidized as they formed Li$$_{2}$$PbO$$_{3}$$ and Li$$_{2}$$CO$$_{3}$$. Then, Li was depleted from the alloy.

Journal Articles

Electrochemical impedance analysis on solid electrolyte oxygen sensor with gas and liquid reference electrodes for liquid LBE

Adhi, P. M.*; Okubo, Nariaki; Komatsu, Atsushi; Kondo, Masatoshi*; Takahashi, Minoru*

Energy Procedia, 131, p.420 - 427, 2017/12

 Times Cited Count:0 Percentile:0.03

The ionic conductivity of solid electrolyte may insufficient, and the sensor output signal will deviate from the theoretical one in low temperature. The performance of oxygen sensor with Ag/air reference electrode (RE) and liquid Bi/Bi$$_{2}$$O$$_{3}$$ RE was tested in low-temperature LBE at 300$$sim$$450$$^{circ}$$C and the charge transfer reactions impedance at the electrode-electrolyte interface was analyzed by electrochemical impedance analysis (EIS). After steady state condition, both of the sensors performed well and can be used at 300$$sim$$450$$^{circ}$$C. Bi/Bi/Bi$$_{2}$$O$$_{3}$$ RE has lower impedance than Ag/air RE. Therefore, the response time of the oxygen sensor with Bi/Bi/Bi$$_{2}$$O$$_{3}$$ RE is faster than the oxygen sensor with Ag/air RE in the low-temperature region.

Oral presentation

Development of HTGR and its Heat Application in JAEA

Kunitomi, Kazuhiko; Nishihara, Tetsuo; Tachibana, Yukio; Sakaba, Nariaki; Yan, X.; Kubo, Shinji; Shibata, Taiju; Ohashi, Hirofumi

no journal, , 

Advantages of the HTGR system from the standpoint of GHG emission reductions together with its deployment scenario in Japan and the other countries is described. In addition, the status of HTGR technology and hydrogen technology developments focusing on key technologies advanced in the recent couple of years is presented.

Oral presentation

Absorbed dose estimation for minor actinides separation process as a function of linear energy transfer

Toigawa, Tomohiro; Tsubata, Yasuhiro; Kai, Takeshi; Kimura, Takahiro; Matsumura, Tatsuro

no journal, , 

To evaluate the feasibility of the solvent extraction process, absorbed dose of each quality of radiation for extraction solvents were estimated by using a Monte Carlo Particle and Heavy Ion Transport code System, PHITS. Our results suggest that low LET radiation will be dominant influence on absorbed dose. It was demonstrated the degradation yields of the extractants and the generation yields of the degradation products could be evaluated by reference to the experimentally obtained G-values.

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