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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
Kurikami, Hiroshi; Yoshikawa, Hideki; Sasamoto, Hiroshi; Iijima, Kazuki; Zaima, Naoki; Munakata, Masahiro; Tokizawa, Takayuki; Nakayama, Shinichi
JAEA-Review 2012-045, 129 Pages, 2013/01
JAEA-Review-2012-045.pdf:15.94MB
This report shows the records of JAEA's investigation on dose rate reduction at the Fukushima University Junior High School and Kindergarten. The main outcomes are as follows. (1) 
experiments were performed to investigate intrusion depth of radiocesium in the soil. Based on the experiment, we proposed a countermeasure to reduce air dose rates. (2) The action we proposed allowed dose rate reduction to about one tenth to one twentieth at playgrounds. (3) Follow-up monitoring was performed after one year, and shows no obvious evidence of recontamination at the playgrounds. (4) Decontamination of a tree was tested. Radiocesium was accumulated around the root. By removing the soil, the air dose rate at about one-meter distance from the tree was decreased.
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.
Zaima, Naoki; Nakashima, Shinichi; Kaneda, Koji; Kado, Kazumi
JAEA-Technology 2010-046, 31 Pages, 2011/02
JAEA-Technology-2010-046.pdf:2.84MBJAEA-Technology-2010-046(errata).pdf:0.05MB
The uranium mass assay systems for 200-litter wastes drums applied neutron and measurements by NDA method had been developed. The measurement systems and trial data are described in this preliminary report. The systems are composed of the 16 pieces of helium-3 proportional counters for neutron detection and a large sized NaI(Tl) scintillation 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 scheduled to try 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; Morimoto, Yasuyuki; Sugitsue, Noritake; Kado, Kazumi
Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.311 - 320, 2010/10
Komeda, Masao; Ozu, Akira; Haruyama, Mitsuo; Takase, Misao; Kureta, Masatoshi; Nakatsuka, Yoshiaki; Zaima, Naoki; Nakashima, Shinichi
no journal, ,
no abstracts in English
Nakatsuka, Yoshiaki; Zaima, Naoki; Nakashima, Shinichi; Fujiki, Naoki*; Ozu, Akira; Haruyama, Mitsuo; Kureta, Masatoshi
no journal, ,
no abstracts in English
Suwaki, Takuro*; Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Fujiki, Naoki*; Kureta, Masatoshi; Ozu, Akira
no journal, ,
Japan Atomic Energy(JAEA) configurated the non-destructive assay (NDA) systems, which applied to the bulk state nuclear inventory and actual uranium bearing waste drums generated from Ningyo-Toge uranium plants. The methodology of newly active neutron assay systems (JAWAS-N) is based on the fast neutron direct interrogation (FNDI) method developed by NSEC. The systems are composed of neutron generator and He-3 proportional counters with concrete structures functioned as reflector or shielding. FNDI method is defined as followings. Neutron generator produces pulses of 14 MeV neutrons that are directed into drum to induce U-235 fissions in matrix. Secondary fission neutrons generated from U-235 with fast or epithermal neutron energy will be detected by He-3 proportional counters with the diffusion decay time on the order of hundreds micro-second. Neutron detectors which are designed to detect only fast and epithermal neutrons, will be extracted fission neutrons by mathematical analysis methods and be determined U-235 mass. The Systems will be contributed to the field of material accountancy in Ningyo-Toge uranium plants. The systems' verifications through the mockup tests and trials for actual waste drams measurement will be reported.
Nakatsuka, Yoshiaki; Zaima, Naoki; Nakashima, Shinichi; Fujiki, Naoki*; Suwaki, Takuro*; Kureta, Masatoshi; Ozu, Akira; Komeda, Masao
no journal, ,
The historical procedures and target of active neutron measurements devices will be reported beside requirements of SG/MA tools. Also introduced the principles of FNDI methods and its applicability.
Fujiki, Naoki*; Nakatsuka, Yoshiaki; Zaima, Naoki; Nakashima, Shinichi; Suwaki, Takuro*; Kureta, Masatoshi; Ozu, Akira; Komeda, Masao
no journal, ,
The performances of methodological characteristics, operation stability and radiation control of active neutron measurements devices will be reported.
Suwaki, Takuro*; Zaima, Naoki; Nakatsuka, Yoshiaki; Fujiki, Naoki*; Nakashima, Shinichi; Kureta, Masatoshi; Ozu, Akira; Komeda, Masao
no journal, ,
The mockup tests used standard uranium source and simulated matrices have been successfully performed. The well performances of this device are introduced.
Zaima, Naoki; Nakatsuka, Yoshiaki; Nakashima, Shinichi; Fujiki, Naoki*; Suwaki, Takuro*; Kureta, Masatoshi; Ozu, Akira; Komeda, Masao
no journal, ,
The trials for measuring actual waste drums have been performed, and validated good applicability active neutron measurements device on site.
Zaima, Naoki; Nakatsuka, Yoshiaki; Nakashima, Shinichi; Ozu, Akira; Komeda, Masao; Kureta, Masatoshi
no journal, ,
JAEA developed NDA systems which applied to the actual scrapped nuclear materials and uranium bearing waste drums heavily generated from URCP and NEP in Ningyo-site. In order to improve the methodology of determination uranium mass the active assay neutron NDA measurement system (JAEA Waste Assay System-Ningyo=JAWAS-N) used by the Fast Neutron Direct Interrogation (FNDI) method have been configurated. The validation tests have been achieved successfully, also the trials for measuring the actual nuclear materials or waste drums just started and accumulated over 550 data with quick and high accuracy measuring. The die-away time, which means neutron decay time in phenomenon, may be used for analyzing uranium mass, at the same time, the neutron behavior simulations over time spectrum have been carried out and verified our measurement system.
Yokoyama, Kaoru; Zaima, Naoki; Takahashi, Nobuo; Sugitsue, Noritake; Suzuki, Yasuo*; Muroi, Masayuki*
no journal, ,
We have developed a new analysis method on measuring radioactivity of uranium (U) filled in waste drums using passive ray measurement. We proposed a new evaluation function which gives a unique relation between source positions and ray count rate.
