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Journal Articles

Disposal and recycling; Safer disposal and reassuring recycling

Nishihara, Kenji

ImPACT Fujita Puroguramu Kokai Seika Hokokukai "Kaku Henkan Niyoru Koreberu Hoshasei Haikibutsu No Ohaba Na Teigen, Shigenka" Seika Hokokusho, Shiryoshu, p.28 - 31, 2019/03

In this project, long-lived fission products (LLFP) contained in conventional high-level radioactive wastes are separated and their life is reduced, and elements that can be used as resources are separated. By shortening the life of LLFP, it has been shown that it may be possible to dispose in intermediate depth of several tens of meters, meeting safety requirements, instead of geological disposal. In addition, for reassuring recycling of usable elements, possible exposure pathways were evaluated to estimate the safe concentration level of radioactivity.

Journal Articles

Investigation of system for volume-reduction and recycling of HLW

Nishihara, Kenji

ImPACT Fujita Puroguramu Kokai Seika Hokokukai "Kaku Henkan Niyoru Koreberu Hoshasei Haikibutsu No Ohaba Na Teigen, Shigenka" Seika Hokokusho, Shiryoshu, p.130 - 133, 2019/03

High level radioactive waste contains elements with various characteristics. It is possible to reduce the load on the disposal site by separating them according to those characteristics and appropriately dealing with them. In this project, we are working to shorten the life span of long-lived fission products (LLFP). When this technology is realized, high-level radioactive wastes will become new radioactive wastes with low radioactivity. As a result of investigation of disposal concept of new radioactive waste, it turned out that intermediate-depth disposal currently considered for low level radioactive waste may be suitable. Intermediate-depth disposal is a method of small-scale disposal in shallow locations as compared to geological disposal for conventional high-level radioactive waste. We conducted a safety assessment when this disposal is applied to new radioactive wastes, and found that it is possible to safely dispose of for the four LLFPs addressed by this project.

Journal Articles

Disposal of radioactive waste and partitioning-transmutation; Consideration of waste disposal from view point of source term

Nishihara, Kenji

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 25(2), p.131 - 134, 2018/12

Impact of reduction of source term on design and safety assessment of disposal concept for high level radioactive waste is considered. Reduction of source term in partitioning and transmutation technology is shown with impact on disposal concept. Moreover, cost and technological readiness is outlined.

Journal Articles

Role of breakup processes in deuteron-induced spallation reactions at 100-200 MeV/nucleon

Nakayama, Shinsuke; Furutachi, Naoya; Iwamoto, Osamu; Watanabe, Yukinobu*

Physical Review C, 98(4), p.044606_1 - 044606_8, 2018/10

 Times Cited Count:6 Percentile:24.15(Physics, Nuclear)

Use of deuteron-induced spallation reactions at intermediate energies has recently been proposed for transmutation of several long-lived fission products (LLFPs). In the design study of a transmutation system using a deuteron primary beam, accurate cross section data of deuteron-induced reactions on the LLFPs are indispensable. In the present study, production cross sections of residual nuclei in the deuteron-induced reactions on $$^{93}$$Zr and $$^{107}$$Pd at $$100-200$$ MeV/nucleon are analyzed using DEURACS, in which the breakup processes are explicitly taken into account. The calculated values reproduced the experimental data quantitatively well. From a component-by-component analysis, it was found that the components of nucleon absorption make the significant contributions to residual nuclei production. This result strongly indicates that consideration of the breakup processes is essentially important to predict production of residual nuclei in deuteron-induced reactions.

Journal Articles

Method to reduce long-lived fission products by nuclear transmutations with fast spectrum reactors

Chiba, Satoshi*; Wakabayashi, Toshio*; Tachi, Yoshiaki; Takaki, Naoyuki*; Terashima, Atsunori*; Okumura, Shin*; Yoshida, Tadashi*

Scientific Reports (Internet), 7(1), p.13961_1 - 13961_10, 2017/10

 Times Cited Count:9 Percentile:12.6(Multidisciplinary Sciences)

Transmutation of long-lived fission products (LLFPs: $$^{79}$$Se, $$^{93}$$Zr, $$^{99}$$Tc, $$^{107}$$Pd, $$^{129}$$I, and $$^{135}$$Cs) into short-lived or non-radioactive nuclides by fast neutron spectrum reactors without isotope separation has been proposed as a solution to the problem of radioactive wastes disposal. Despite investigation of many methods, such transmutation remains technologically difficult. To establish an effective and efficient transmutation system, we propose a novel neutron moderator material, yttrium deuteride (YD$$_{2}$$), to soften the neutron spectrum leaking from the reactor core. Neutron energy spectra and effective half-lives of LLFPs, transmutation rates, and support ratios were evaluated with the continuous-energy Monte Carlo code MVP-II/MVP-BURN and the JENDL-4.0 cross section library. With the YD$$_{2}$$ moderator in the radial blanket and shield regions, effective half-lives drastically decreased from 10$$^{6}$$ to 10$$^{2}$$ years and the support ratios reached 1.0 for all six LLFPs. This successful development and implementation of a transmutation system for LLFPs without isotope separation contribute to developing a self-consuming cycle of LLFPs using fast spectrum reactors to reduce radioactive waste.

Journal Articles

Current activities and future plans for nuclear data measurements at J-PARC

Kimura, Atsushi; Harada, Hideo; Nakamura, Shoji; Iwamoto, Osamu; Toh, Yosuke; Koizumi, Mitsuo; Kitatani, Fumito; Furutaka, Kazuyoshi; Igashira, Masayuki*; Katabuchi, Tatsuya*; et al.

European Physical Journal A, 51(12), p.180_1 - 180_8, 2015/12

 Times Cited Count:1 Percentile:81.58(Physics, Nuclear)

JAEA Reports

Status and future plan of research and development on partitioning and transmutation technology for long-lived nuclides in JAERI

Oigawa, Hiroyuki; Nishihara, Kenji; Minato, Kazuo; Kimura, Takaumi; Arai, Yasuo; Morita, Yasuji; Nakayama, Shinichi; Katakura, Junichi

JAERI-Review 2005-043, 193 Pages, 2005/09

JAERI-Review-2005-043.pdf:16.13MB

JAERI has been conducting research and development on partitioning and transmutation (P&T) technology for long-lived nuclides to develop the double-strata fuel cycle concept, in accordance with the Atomic Energy Commission's "Research and Development of Technologies for Partitioning and Transmutation of Long-lived Nuclides - Status and Evaluation Report" issued in 2000. The double-strata fuel cycle concept consists of four major processes: partitioning, fuel fabrication, transmutation, and fuel processing. The five-year achievement and future perspectives for the technology on these processes are presented in this report. It also provides an analytical study on impacts of introducing P&T technology on waste management, and on deployment of P&T for the future nuclear energy system.

Journal Articles

Research and development on the nuclear fuels

Sawa, Kazuhiro; Yamashita, Toshiyuki; Minato, Kazuo; Arai, Yasuo; Konashi, Kenji*

Nippon Genshiryoku Gakkai-Shi, 44(9), p.657 - 662, 2002/09

no abstracts in English

JAEA Reports

Measurement of neutron capture cross sections of Tc-99

*

JNC-TJ9400 2000-008, 61 Pages, 2000/02

JNC-TJ9400-2000-008.pdf:2.5MB

For studies on nuclear transmutation of long-lived fission products (LLFPs) in a fast reactor, detailed characteristics of reactor core such as transmutation performance have to be investigated, so accurate neutron cross section data of LLFPs become necessary. Therefore, the keV-neutron capture cross sections of Tc-99, which is one of important LLFPs, were measured in the present study to obtain the accurate data. The measurement was relative to the standard capture cross sections of Au-197. A neutron time-of-flight method was adopted with a ns-pulsed neutron source by a Pelletron accelerator and a large anti-Compton NaI(TI) gamma-ray detector. As a result, the capture cross sections of Tc-99 were obtained with the error of about 5 % in the incident neutlon energy region of 10 to 600 keV. The present data were compared with other experimental data and the evaluated values of JENDL-3.2, and it was found that the evaluations of JENDL-3.2 were 15-20 % smaller than the present measurements.

JAEA Reports

Measurement of neutron capture cross sections of Tc-99

*

JNC-TJ9400 99-001, 78 Pages, 1999/03

JNC-TJ9400-99-001.pdf:2.07MB

For studies on incineration of long-lived fission products (LLFPs) in a fast reactor, detailed characteristics of reactor core such as incineration performance have to be investigated. Therefore, accurate neutron cross section data of LLFPs become necessary. In the present study, in order to perform the precise measurements of keV-neutron capture cross sections of Tc-99, which is one of most important LLFPs, the details of the Tc-99 sample and the measurements with our experimental facilities were investigated.

Journal Articles

Research and development on transmutation of high-level waste, 3.2; Transmutation with accelerator

*; Takizuka, Takakazu

Nippon Genshiryoku Gakkai-Shi, 37(3), p.167 - 171, 1995/00

no abstracts in English

Oral presentation

Current activities for nuclear data measurements at ANNRI

Kimura, Atsushi; Harada, Hideo; Nakamura, Shoji; Toh, Yosuke; Igashira, Masayuki*; Katabuchi, Tatsuya*; Mizumoto, Motoharu*; Hori, Junichi*; Kino, Koichi*

no journal, , 

Oral presentation

Study on new transmutation method of LLFP using heavy water reactor and cold neutron, 3; Moderation system for cold neutron

Tachi, Yoshiaki; Takaki, Naoyuki*; Iida, Takumi*; Wakabayashi, Toshio*

no journal, , 

no abstracts in English

Oral presentation

R&D for accuracy improvement of neutron nuclear data on minor actinides, 7; Measurements of neutron capture cross sections in fast neutron energy region with ANNRI at J-PARC

Katabuchi, Tatsuya*; Igashira, Masayuki*; Terada, Kazushi; Kimura, Atsushi; Nakamura, Shoji; Nakao, Taro; Iwamoto, Osamu; Harada, Hideo; Hori, Junichi*

no journal, , 

no abstracts in English

Oral presentation

Development of nuclear transmutation methods for converting LLFP into stable or short-lived nuclides, 15; Level densities of LLFPs and nuclei around LLFPs calculated based on the microscopic structure calculation

Furutachi, Naoya; Minato, Futoshi; Iwamoto, Osamu

no journal, , 

To establish a reasonable nuclear transmutation technology for long-lived fission products (LLFPs), it is important to improve precision of the nuclear data needed for the simulation of the nuclear transmutation. The level density is essential for the nuclear reaction calculation using the statistical model, and it has significant influence on the precision of the nuclear data evaluation. Although a phenomenological model such as Fermi Gas model is used in a usual nuclear data evaluation, it is considered that using a microscopic theory that has predictive power superior to a phenomenological model brings better precision for the nuclear data. In this study, to improve precision of the nuclear data of LLFPs and nuclei around LLFPs, the level densities needed for the nuclear data evaluation of those nuclei were derived based on the microscopic nuclear data calculation. In this derivation, we improved the calculation method to describe prcisely the effect of the deformation change with nuclear excitation. To analyze precision of the nuclear reaction calculation, we compared the cross sections of various reaction channel systematically with the experimental data of stable nuclei.

Oral presentation

Development of nuclear data evaluation method to improve precision of nuclear data for long-lived fission products

Furutachi, Naoya; Minato, Futoshi; Iwamoto, Osamu

no journal, , 

no abstracts in English

Oral presentation

Theoretical model analysis of deuteron-induced spallation reactions on long-lived fission products

Nakayama, Shinsuke; Furutachi, Naoya; Iwamoto, Osamu; Watanabe, Yukinobu*

no journal, , 

In the ImPACT project, deuteron is a first candidate of incident beam for nuclear transmutation of long-lived fission products (LLFPs) and accurate deuteron nuclear data on LLFPs are strongly required. Thus, we have performed theoretical model analysis of deuteron-induced spallation reactions on LLFP with DEURACS, which is the computational code dedicated for deuteron-induced reactions. Through comparison with measured data and other calculation method, the applicability of DEURACS to spallation reactions and the role of breakup processes in the reactions will be discussed.

Oral presentation

Reduction and resource recycling of high-level radioactive wastes through nuclear transmutation, 1-2; Investigation of system for volume-reduction and recycling of HLW

Nishihara, Kenji; Kawashima, Masatoshi*; Fujita, Reiko*

no journal, , 

In this project, research and development of elemental technologies has been promoted for separation and transmutation. In this research, we integrated HLW volume reduction and resource recycling system and evaluated the overall material balance. In addition, we examined the disposal method of generated waste and the possibility of recycled materials.

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