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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

A Study on transmutation of LLFPs using various types of HTGRs

Kora, Kazuki*; Nakaya, Hiroyuki*; Matsuura, Hideaki*; Goto, Minoru; Nakagawa, Shigeaki; Shimakawa, Satoshi*

Nuclear Engineering and Design, 300, p.330 - 338, 2016/04

 Times Cited Count:5 Percentile:54.39(Nuclear Science & Technology)

In order to investigate the potential of high temperature gas-cooled reactors (HTGRs) for transmutation of long-lived fission products (LLFPs), numerical simulation of four types of HTGRs were carried out. In addition to the gas-turbine high temperature reactor system "GTHTR300", a small modular HTGR plant "HTR50S" and two types of plutonium burner HTGRs "Clean Burn with MA" and "Clean Burn without MA" were considered. The simulation results show that an early realization of LLFP transmutation using a compact HTGR may be possible since the HTR50S can transmute fair amount of LLFPs for its thermal output. The Clean Burn with MA can transmute a limited amount of LLFPs. However, an efficient LLFP transmutation using the Clean Burn without MA seems to be convincing as it is able to achieve very high burn-ups and produce LLFP transmutation more than GTHTR300. Based on these results, we propose utilization of variety of HTGRs for LLFP transmutation and storage.

Journal Articles

Transmutation of $$^{129}$$I using an accelerator-driven system

Nishihara, Kenji; Takano, Hideki

Nuclear Technology, 137(1), p.47 - 59, 2002/01

 Times Cited Count:2 Percentile:17.59(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Expansion of material balance analysis function on nuclear fuel cycle

Ohtaki, Akira; ; ; *; *;

JNC TN9410 2000-006, 74 Pages, 2000/04


To evaluate materials balance in nuclear fuel cycle quickly and quantitatively the fuel cycle requirement code "FAMILY" was improved. And an accumulated TRU&LLFP quantity analysis code was developed. The contents are as follows: (1)A calculation ability of minor actinide production and expenditure was added to the "FAMILY" code. (2)An output program for the "FAMILY" calculation results was developed. (3)A simple version of "FAMILY" code was developed. (4)An analysis code for accumulated TRU&LLFP quantity in nuclear fuel cycle was developed.

JAEA Reports

Investigation of equilibrium core by recycling MA and LLFP in fast reactor cycle (II) -lnvestigation of LLFP confined in eEquilibrium core with element separation-

Mizutani, Akihiko; ;

JNC TN9400 2000-013, 66 Pages, 2000/02


Feasibility study on a self-consistent fuel cycle system has been performed in the nuclear fuel recycle system with fast reactors. ln this system, the self-generated MAs (Minor Actinides) and LLFPs (Long-Lived Fission Products) are confined and incinerated in the fast reactor, which is called the "Equilibrium Core" concept. However, as the isotope separations for selected LLFPs have been assumed in this cycle system, it seems that this assumption is far from realistic one from the viewpoint of economy with respect to the fuel cycle system. ln this study, the possibility for realization of the "Equilibrium Core" concept is evaluated for three fuel types such as oxide, nitride and metallic fuels, provided that the isotopic separation of LLFPs is changed to the element one. This study provides, that is to say, how many LLFP elements can be confined in the "Equilibrium Core" with element separation. This report examines the nuclear properties of the "Equilibrium Core" for various combinations of LLFP incineration schemes from the viewpoints of the risk of geological disposal and the limit in confinable quantity of LLFPs. From the viewpoint of the risk of geological disposal estimated by the retardation factor, it is possible to confine with element separation for T$$_{c}$$, I and Se even in the oxide fueled core. From the standpoint of the limit of confinable amounts of LLFPs, on the other hand, T$$_{c}$$, I, S$$_{e}$$, S$$_{n}$$ and Cs can be confined with element separation in case that the nitride fuel is chosen.

JAEA Reports

Measurement of neutron capture cross sections of Tc-99


JNC TJ9400 99-001, 78 Pages, 1999/03


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.

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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