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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.
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.
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.
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, Yoshiaki; Kawatsuma, Shinji; Tokizawa, Takayuki
no journal, ,
Japan Atomic Energy Agency (JAEA) will apply clearance on uranium bearing waste and reuse metal waste as much as possible, according to national policy which plan effective and rational treatment or disposal of radioactive waste and reuse of uranium. Sludge (conversion neutralized sludge, sodium fluoride or fluid media and so on) are considered cement mixing solidification directly for low concentration, uranium recovery and reuse and cement mixing solidification of residue directly for high concentration. As uranium recovery, dissolve in hydrochloric acid and precipitation is promising method.
Ohashi, Yusuke; Nakatsuka, Yoshiaki; Kawatsuma, Shinji; Hata, Haruhi; Tsunashima, Yasumichi; Murata, Masato; Tokizawa, Takayuki; Sugitsue, Noritake
no journal, ,
Sludge waste derived from research and discussion for uranium refining and conversion exclude much uranium. We must recover uranium from them from the point of view of use of resource and we dispose of residue generated by the process. We recovered uranium from real waste by water or hydrochloric acid. The dissolution rates of uranium from sludge from neutralization and NaF, filter medium, alumina, MgF wastes were more than 99% by 2 hour 1N HCl treatment. The dissolution rate of uranium from bed material waste was more than 99% by 24h 1N HCl treatment and addition of hydrogen peroxide. The dissolution rates of NaF, filter medium waste by water treatment were 99% and 88%. From the results, we confirmed dissolution characteristics of real waste as basic data to study recovery process of uranium.
Tsunashima, Yasumichi; Nakatsuka, Yoshiaki; Kawatsuma, Shinji; Ohashi, Yusuke; Murata, Masato; Tokizawa, Takayuki; Sugitsue, Noritake; Hata, Haruhi
no journal, ,
The operation waste generated from the uranium handling facilities of the uranium conversion and uranium enrichment, etc. is called a sludge. They are assumed to be execution of the uranium collection if necessary, cement solidification, and disposal. Therefore, the examination that confirmed the range where cement solidifies was executed. The cement kind, the water cement ratio, and the sludge mixture rate were assumed to be a parameter and the solidification test was executed. The range of solidification was confirmed by the bleeding water after 24 hours had passed. The uniaxial compression was measured with cement in the solidification condition. A possibility miscible from 40wt% to about 60wt% was able to be confirmed from these examination results in the absorbent (NaF pellet and active alumina), the bed materials (no active alumina), Neutralizing precipitation.
Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi
no journal, ,
We developed uranium mass assay systems for 200-litter wastes drums applied neutron and measurements by NDA method. In this intermediate report we will describe measurement systems and trial data. The systems are composed of the 16 pieces of helium-3 proportional counters for neutron detection and a Germanium solid state detector for ray detection. The extensive testing trials using the calibrated uranium sources with different enrichment and some kinds of matrices in drums were performed. Through the one year testing the useful experiences of this system concerning neutron and ray measurements for uranium mass were obtained. Almost all instruments and software were so good performance as is designed. As the next step we are now trying the measurements for actual wastes that are stored in the Uranium Refining and Conversion Plant at Ningyo-toge, and put practical uses near future. Our research was accomplished with the support of LANL.
Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi
no journal, ,
We developed uranium mass assay systems for 200-litter wastes drums applied neutron and measurements by NDA method. The systems are composed of the 16 pieces of helium-3 proportional counters for neutron detection with 100 mm thicken polyethylene and a Ge-SSD for ray detection. The neutron measurement methodology is consist of U-234 (,n) reaction and measurement is applied by Ge-SSD. The extensive testing trials using the calibrated uranium sources with different enrichment and some kinds of matrices in drums were performed. By using this systems we tried to determine uranium mass in drums for the purpose of reduction MUF in URCP.
