Takai, Shizuka; Hagino, Koichi*
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.3 - 11, 2015/00
One of the major problems of fuel cycle is the disposal of high-level radioactive waste which contains long-lived nuclides and high-decay heating nuclides. Transmuting such nuclides into short-lived or stable nuclides is one possible way to resolve this problem. Neutron capture reactions have been proposed for transmutations of such fission products. However, this transmutation method is not effective for nuclides with small neutron capture cross sections such as Cs. Recently, the photo-neutron (,n) reactions via giant dipole resonance with laser Compton scattering -rays has been suggested as an alternative method for nuclear transmutations. In this paper, we investigate in detail the effectiveness of the transmutation of Cs quantitatively. For the transmutation of Cs of 1g with photon flux /s, /s and /s for 24 hours, 10%, 70% and 99% reduction of the initial amount of Cs is theoretically possible.
Yamamoto, Kento; Okumura, Keisuke; Kojima, Kensuke; Okamoto, Tsutomu
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.233 - 249, 2015/00
To improve the prediction accuracy of concentrations of activation products (APs) in the field of nuclear back-end, it is important to investigate the elements and the nuclear reactions leading to generation of APs. To clarify quantitatively the source elements and the nuclear reactions dominating generation of APs, sensitivity analyses of initial compositions and cross sections were conducted using ORIGEN2.2 code and ORLIBJ40, which is a set of the 1-group cross section libraries based on JENDL-4.0. Activations of cladding tubes, end-plugs and spacers of fuel assemblies and channel boxes in BWR, whose materials are zirconium alloy, stainless steel, and nickel-chromium-based alloy, were analyzed. The results clarified quantitatively the source elements and the nuclear reactions dominating generation of APs. It was remarkable that the dominant generation pathways were clarified even for the nuclides generated through complicated pathways. In conclusion, the results of sensitivity analyses could be utilized to select the objective of elements for measurements of impurities in the materials and of nuclear data for improvement of accuracy.
Shimada, Asako; Ozawa, Mayumi; Kameo, Yutaka; Yasumatsu, Takuyo*; Nebashi, Koji*; Niiyama, Takuya; Seki, Shuhei; Kajio, Masatoshi; Takahashi, Kuniaki
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.311 - 317, 2015/00
no abstracts in English
Nishihara, Kenji; Tsujimoto, Kazufumi; Oigawa, Hiroyuki
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.207 - 231, 2015/00
With consideration of the phase-out option from NP utilization in Japan, an ADS for Pu transmutation is designed and scenario analysis is performed. The ADS is designed based on the existing ADS design for MA transmutation, and the 6-batch ADS is selected as a reference design for scenario analysis. In the scenario analysis, once-through scenario of LWR spent fuel is referred as a conventional scenario with a LWR-MOX utilization scenario. As the transmutation scenario, three cases of transmuters that are only-FR, only-ADS and both-FR+ADS are analyzed. The numbers of necessary transmuters are obtained as 15 to 32, and, the necessary period for transmutation as 180 to 240 years. Benefit on repository by reduction of Pu and MA is reduction of repository area by a factor of five and of decay time of toxicity by a magnitude of order. The FR+ADS scenario is considered to be a modest solution, though the ADS scenario is preferable if rapid transmutation is required.
Suyama, Kenya; Uchiyama, Gunzo; Fukaya, Hiroyuki; Umeda, Miki; Yamamoto, Toru*; Suzuki, Motomu*
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.47 - 56, 2015/00
In fission products in used nuclear fuel, there are several stable isotopes which have large neutron absorption effect. It is known that there are several hardly measurable elements in such important fission products. JAEA had been developed the method to assess the amount of fission products which are hardly measurable and have large neutron capture cross section, under the auspices of the JNES. In this development, the measurement method was developed combining a simple and effective chemical separation scheme of fission products from used nuclear fuel and ICP-MS with high-sensitivity and high-precision. This method was applied to the measurement program for used BWR 99 fuel assembly. This method is applicable to the required measurement for the countermeasure to the accident of the Fukushima Dai-ichi Nuclear Power Plants of Tokyo Electric Power Company. This presentation describes the measurement method developed in the study as well as the future measurement plan in JAEA.
Koizumi, Mitsuo; Kitatani, Fumito; Tsuchiya, Harufumi; Harada, Hideo; Takamine, Jun; Kureta, Masatoshi; Iimura, Hideki; Seya, Michio; Becker, B.*; Kopecky, S.*; et al.
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.13 - 20, 2015/00
Neutron Resonance Densitometry (NRD) has been proposed for quantification of nuclear materials in melted fuel. NRD is a combined TOF technique of Neutron Resonance Transmission Analysis (NRTA) and Neutron Resonance Capture Analysis (NRCA) or Prompt Gamma ray Analysis (PGA). To establish the method, development of detectors is in progress. Experiments were carried out at a TOF facility, GELINA, under the collaboration with EC-JRC-IRMM. The progress of the project is reported.
Tonoike, Kotaro; Sono, Hiroki; Umeda, Miki; Yamane, Yuichi; Kugo, Teruhiko; Suyama, Kenya
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.251 - 259, 2015/00
In the Three Mile Island Unit 2 reactor accident, a large amount of fuel debris was formed whose criticality condition is unknown except the possible highest U/U enrichment. The fuel debris had to be cooled and shielded by water in which the minimum critical mass is much smaller than the total mass of fuel debris. To overcome this uncertain situation, the coolant water was borated with sufficient concentration to secure the subcritical condition. The situation is more severe in the damaged reactors of Fukushima Daiichi Nuclear Power Station, where the coolant water flow is practically "once through". Boron must be endlessly added to the water to secure the subcritical condition of the fuel debris, which is not feasible. The water is not borated relying on the circumstantial evidence that the xenon gas monitoring in the containment vessels does not show a sign of criticality. The criticality condition of fuel debris may worsen due to the gradual drop of its temperature, or the change of its geometry by aftershocks or the retrieval work, that may lead the criticality. To avoid criticality and its severe consequences, a certain principle of criticality control must be established. There may be options, such as prevention of the criticality by coolant water boration or by neutronic monitoring, prevention of the severe consequences by intervention measures against criticality, etc. Every option has merits and demerits that must be adequately evaluated toward selection of the best principle.
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.73 - 79, 2015/00
To obtain the data required for ADS design, JAEA plans to build a Transmutation Experimental Facility (TEF) in the J-PARC project. TEF consists of an ADS target test facility (TEF-T), which will be installed high power Pb-Bi spallation target, and a Transmutation Physics Experimental Facility (TEF-P), which set up a fast critical/subcritical assembly driven by low power proton beam. TEF will be located at the end of J-PARC 400MeV LINAC and accepts 250 kW proton beam. As a major research and development items of TEF-T, irradiation test for candidate ADS materials, engineering tests for Pb-Bi target and experiments to determine the effective lifetime of proton beam window will be performed. When the target operates with full power beam, fast neutron spectrum field is formed around the target and it is possible to apply multi-purpose usage. In the presentation, roadmap to establish the ADS transmutor and design activities for TEF construction will be summarized.