Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Komeda, Masao; Ozu, Akira; Mori, Takamasa; Nakatsuka, Yoshiaki; Maeda, Makoto; Kureta, Masatoshi; Toh, Yosuke
Journal of Nuclear Science and Technology, 55(8), P. 962, 2018/08
Times Cited Count：0 Percentile：1.39(Nuclear Science & Technology)We correct the derivation of equations in the derivation of equations in the paper of "Study of the neutron multiplication effect in an active neutron methods [J Nucl Sci Technol. 2017;54(11):1233-1239]". Although the derivations are not correct, the obtained equations are correct. Therefore, the results and discussions of the paper remain the same.
USakoda, Akihiro; Nakatsuka, Yoshiaki; Ishimori, Yuu; Nakashima, Shinichi; Komeda, Masao; Ozu, Akira; Toh, Yosuke
Journal of Nuclear Science and Technology, 55(6), p.605 - 613, 2018/06
Times Cited Count：1 Percentile：11.49(Nuclear Science & Technology)For better nuclear material accountancy, we had developed a non-destructive assay system dedicated to uranium waste drums (JAWAS-N: JAEA Waste Assay System at Ningyo-toge). The system is based on a fast neutron direct interrogation (FNDI) method. To clarify the characteristics of the FNDI method and the performance of JAWAS-N, experimental and computational mock-up tests were carried out using various dry materials that contained known amounts of natural uranium. As a result, linearity between the die-away time (
) and the counts of fast neutrons attributed to U fission was confirmed experimentally and analytically. Moreover, the MCNP simulation was performed to discuss the radial and axial dependences of U fission probability, neutron detection efficiency, and sensitivity on uranium distributions in the drum. The simulation results agreed with the empirical results reported in a previous paper, providing valuable information on the practice of FNDI-based uranium determination. Furthermore, the nominal detection limits of natural uranium in JAWAS-N were estimated to be 15, 4, and 2 g for = 0.2, 0.3, and 0.4 msec, respectively. The findings obtained here will contribute to the implementation of the FNDI method to assess the quantities of U in actual uranium waste drums.
Ozu, Akira; Komeda, Masao; Kureta, Masatoshi; Nakatsuka, Yoshiaki; Nakashima, Shinichi
Nihon Genshiryoku Gakkai-Shi ATOMO
, 59(12), p.700 - 704, 2017/12
no abstracts in English
Komeda, Masao; Ozu, Akira; Mori, Takamasa; Nakatsuka, Yoshiaki; Maeda, Makoto; Kureta, Masatoshi; Toh, Yosuke
Journal of Nuclear Science and Technology, 54(11), p.1233 - 1239, 2017/11
Times Cited Count：8 Percentile：61.27(Nuclear Science & Technology)The previous active neutron method cannot remove the influence of the multiplication effect of neutrons produced by second- and subsequent fission reactions, and it might overestimate the amount of nuclear material if an item contains large amounts. In this paper, we discussed the correction method for the neutron multiplication effect on the measured data in the fast neutron direct interrogation (FNDI) method, one of the active neutron methods, supposing that the neutron multiplication effect is caused mainly by third-generation neutrons from the second-fission reactions under the condition that the forth-generation neutrons are much fewer. This paper proposed a correction method for the neutron multiplication effect in the measured data. Moreover we have shown a possibility that this correction method gives rough estimates of the effective neutron multiplication factor and the subcriticality.
decay of unbound neutron-hole states in 
SnVaquero, V.*; Jungclaus, A.*; Doornenbal, P.*; Wimmer, K.*; Gargano, A.*; Tostevin, J. A.*; Chen, S.*; N
cher, E.*; Sahin, E.*; Shiga, Yoshiaki*; et al.
Physical Review Letters, 118(20), p.202502_1 - 202502_5, 2017/05
Times Cited Count：21 Percentile：77.24(Physics, Multidisciplinary)Ozu, Akira; Komeda, Masao; Kureta, Masatoshi; Zaima, Naoki; Nakatsuka, Yoshiaki; Nakashima, Shinichi
Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(2), p.115 - 127, 2016/06
A non-destructive assay system using the fast neutron direct interrogation method has been developed to put its method into practical use for the determination of uranium (U) mass contained in actual uranium-contaminated waste drums. The method is capable of measuring the fissile mass in a drum by counting the number of fission neutrons resulting from nuclear fission reactions between the fissile materials contained in a drum and thermal neutrons generated by 14 MeV fast neutrons irradiated from outside the drum. The performance test employing simulated metal waste drums demonstrated that a natural uranium mass of as low as 10 g could be detected within an error of 
20% regardless of the distribution of uranium samples in the drum. A demonstration test employing actual waste drums could determine the uranium mass by using a newly developed correction method for deriving the fissile mass in a drum. It has been proved by the experimental validation tests that the assay system equipped with the correction method is very useful for the accountancy of the waste drums.
Uesaka, Mitsuru*; Kobayashi, Hitoshi*; Kureta, Masatoshi; Nakatsuka, Shigehiro*; Nishimura, Kazuya*; Igashira, Masayuki*; Hori, Junichi*; Kiyanagi, Yoshiaki*; Tagi, Kazuhiro*; Seki, Toshichika*; et al.
Reviews of Accelerator Science and Technology, 8, p.181 - 207, 2015/00
We choose nuclear data and nuclear material inspection for energy application and nondestructive testing of explosive and hidden nuclear materials for security application. 90 keV electrostatic accelerators of deuterium are commercially available for nondestructive testing. For nuclear data measurement, electrostatic ion accelerators and L-band and S-band electron linear accelerators (linac) are used for the neutron source. Compact or mobile X-band electron linac neutron sources are under development. Compact proton linac neutron source is used for nondestructive testing especially water in solids. Several efforts for more neutron intensity using proton and deuteron accelerators are also introduced.
Komeda, Masao; Ozu, Akira; Haruyama, Mitsuo; Takase, Misao*; Kureta, Masatoshi; Nakatsuka, Yoshiaki; Zaima, Naoki; Nakashima, Shinichi; Otsuka, Yoshimasa
Proceedings of INMM 55th Annual Meeting (Internet), 9 Pages, 2014/07
We have researched and developed the FNDI method for a long time through experiments in NUCEF in JAEA Tokai. Referred from the pilot machine, we designed a demonstrator, called as JAWAS-N, for applying to non-destructive assay tools for uranium waste drums in JAEA Ningyo. In this paper, we present the modeling and the simulations concerning JAWAS-N's characteristics, and discuss for practical use compared analytical results with obtained some experimental data.
Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Fujiki, Naoki*; Kado, Kazumi
JAEA-Technology 2013-050, 39 Pages, 2014/03
JAEA-Technology-2013-050.pdf:3.56MB
A uranium mass assay system NWAS, for 200-litter wastes drums applied by NDA method was developed and accumulated the data of the actual uranium bearing wastes drums. The system consists of the 16 pieces of Helium-3 proportional counters for neutron detection generated from U-234(
,n) reaction or U-238 spontaneous fissions with polyethylene moderation and a Germanium solid state detector for ray detection as to determine uranium enrichment. The satisfactory works had been continued and the uranium determination data of 850 drums had been accumulated approximately. On the other hand several considerable problems on the system or methodology had been revealed technically or analytically through the measurements experiences. Furthermore as the next improvement plans, the active neutrons assay for uranium bearing wastes drums are now progressing. The results of complications will lead us to the progressive next steps.
Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi
Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-34-Kai Nenji Taikai Rombunshu (Internet), 10 Pages, 2013/10
A uranium mass assay system for 200-litter wastes drums applied by NDA method was developed and accumulated the data of the actual uranium bearing wastes drums. The system consists of the 16 pieces of Helium-3 proportional counters for neutron detection generated from 
U(,n) reaction or 
U spontaneous fissions with polyethylene moderation and a Germanium solid state detector for ray detection as to determine uranium enrichment. In previous report, some measurement experiences had been introduced briefly. After that satisfactory works had been continued and the uranium determination data of 850 drums had been accumulated approximately. On the other hand considerable problems on the system had been revealed technically or analytically. Such experiences are to be described precisely, in addition newly gained knowledge will be marshaled. Furthermore the next improvement plans are now prepared that will be capable of active neutrons assay for uranium bearing wastes drums.
Komeda, Masao; Ozu, Akira; Zaima, Naoki; Nakatsuka, Yoshiaki; Nakashima, Shinichi; Takase, Misao; Haruyama, Mitsuo; Kureta, Masatoshi
Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-34-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2013/10
no abstracts in English
Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi; Haruyama, Mitsuo; Takase, Misao; Ozu, Akira; Kureta, Masatoshi
Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-33-Kai Nenji Taikai Rombunshu (Internet), 8 Pages, 2012/10
We developed uranium mass assay systems for 200-litter wastes drums applied passive neutron measurements by NDA method and applied for the actual wastes drums stored in URCP. The neutron measurement methodology of U(,n) reaction using 
He proportional counters delivered superior performance, however also included some problems that the neutron penetration rates are depend upon matrices or density of wastes drums, so it was difficult to determine uranium mass against "unknown objects". For the purpose of solving problems active neutron measurements appears promising, we are now challenging to improve our equipments, which are composed of neutron generator, polyethylene moderators and He proportional counters. The uranium mass are determined by counting secondary neutrons generated from nuclear fissions. Our preliminary simulations suggest good performances with higher sensitivities and accuracies. It is extremely expected to contribute in the fields of safeguards works.
Haruyama, Mitsuo; Takase, Misao; Ozu, Akira; Kureta, Masatoshi; Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi
Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-33-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2012/10
no abstracts in English
Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi
JAEA-Technology 2012-023, 36 Pages, 2012/08
JAEA-Technology-2012-023.pdf:1.54MB
We developed uranium mass assay systems for 200-litter wastes drums applied neutron and measurements by NDA method. In this report we will describe measurement experiences followed by the previous report. The systems are composed of the 16 pieces of helium-3 (He) proportional counters for neutron detection. The neutron measurement methodology is consist of U (,n)F reaction and spontaneous fission of U. The extensive test trials using the known amount of uranium with different enrichment and some kinds of matrices in drums were performed. By using this NWAS we tried to determine uranium mass in the actual uranium wastes drums stored in the URCP at Ningyo-toge. The actual uranium wastes drums are of great variety, in the point of matrix, bulk density, packing condition and total uranium mass. Therefore we have tried some challenging methods which eliminate problems, and established the applicability to almost all kinds of wastes drums.
treatment condition and uranium decontamination resultEma, Akira; Yokoyama, Kaoru; Nakatsuka, Yoshiaki; Shimaike, Masamitsu; Sugitsue, Noritake
JAEA-Technology 2008-037, 50 Pages, 2008/06
JAEA-Technology-2008-037.pdf:3.15MB
In the centrifugation method uranium enrichment plant, the UF
gas was supplied for a long term. The main uranium compounds are estimated to the middle fluorides UFx(4
x=5). This middle fluoride is changed to UF and IF
gas again by the reaction with IF. Using this reaction, the uranium compound in the plant was decontaminated. The IF treatment tests were executed to the plant in four treatment conditions. It is necessary to clarify the relation between IF treatment condition and decontamination results for the best treatment condition setting. Therefore, the decontamination development is evaluated using the result of the weight measurement of recovery UF and IF gas, the -ray measurement, and the ICP-MS analysis at the IF treatment tests. Then the technical knowledge to clarify the decontamination characteristic features is accumulated for analyzing the treatment trend, the treatment time, decontamination level and variation of the decontamination level.
Nakatsuka, Toru; Oka, Yoshiaki*; Koshizuka, Seiichi*
Nuclear Technology, 134(3), p.221 - 230, 2001/06
Times Cited Count：17 Percentile：74.85(Nuclear Science & Technology)no abstracts in English
Nakatsuka, Toru; Oka, Yoshiaki*; Koshizuka, Seiichi*
Proceedings of 8th International Conference on Nuclear Engineering (ICONE-8) (CD-ROM), p.9 - 0, 2000/00
no abstracts in English
Kawatsuma, Shinji; Nakatsuka, Yoshiaki; Tokizawa, Takayuki
no journal, ,
According to nation's Policy, JAEA is now considering recycle metal after decontamination and clearance and reuse uranium after uranium recovery, as strategy. It is estimated more than 1000 ton of metal scrap, more than ten thousand of metal scrap and around 1000 ton of sludge which will be generated by dismantling of Uranium Conversion Plant, centrifugal Enrichment Pilot Plant, and Uranium Enrichment Demonstration Plant at Ningyotoge. Concrete, undecontainable metal residue after uranium recovery from sludge, etc are considered to be disposed in trench at near surface. Hydrochloric acid precipitation method is nominated for the method of uranium recovery after survey on feature and amount of sludge and uranium recovery method.
Nakatsuka, Toru; Oka, Yoshiaki*; Ishiwatari, Yuki*; Okumura, Keisuke; Nagasaki, Shinya*; Tezuka, Kenichi*; Mori, Hideo*; Ezato, Koichiro; Akasaka, Naoaki; Nakazono, Yoshihisa*; et al.
no journal, ,
Pressure-vessel-type supercritical water cooled reactors (SCWRs) have been developed at the University of Tokyo (UT) since 1989 and are studied in Japan, Europe and other countries. UT's concepts of the reactor are termed "Super LWR" for thermal neutron spectrum and "Super Fast Reactor (FR)" for fast spectrum respectively. With the scope of developing an economical fast reactor system, a Japanese research project of the "Super FR" had been conducted since December 2005 to March 2010. UT, Kyushu University, Japan Atomic Energy Agency and Tokyo Electric Power Company have participated in the project. It consisted of three subjects: (1) development of the Super FR concept, (2) thermal-hydraulic experiments and (3) materials developments. All items have successfully finished. The present paper will summarize the results of the project.
