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Journal Articles

Development of non-destructive assay system using fast neutron direct interrogation method for actual uranium waste drums

Ozu, Akira; Komeda, Masao; Kureta, Masatoshi; Zaima, Naoki; Nakatsuka, Yoshiaki; Nakashima, Shinichi

Nippon 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 ($$^{235}$$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 $$pm$$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.

Journal Articles

Analytical study on uranium measurement in uranium waste drums by the fast neutron direct interrogation method

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.

JAEA Reports

On performance experience and measurements with Ningyo Waste Assay System (NWAS), 3

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($$alpha$$,n) reaction or U-238 spontaneous fissions with polyethylene moderation and a Germanium solid state detector for $$gamma$$ 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.

Journal Articles

NWAS: Developments for passive uranium assay system, 2

Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi

Kaku Busshitsu Kanri Gakkai (INMM) Nippon 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 $$^{234}$$U($$alpha$$,n) reaction or $$^{238}$$U spontaneous fissions with polyethylene moderation and a Germanium solid state detector for $$gamma$$ 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.

Journal Articles

Practical study for uranium measurement in uranium bearing wastes with the fast neutron direct interrogation method

Komeda, Masao; Ozu, Akira; Zaima, Naoki; Nakatsuka, Yoshiaki; Nakashima, Shinichi; Takase, Misao; Haruyama, Mitsuo; Kureta, Masatoshi

Kaku Busshitsu Kanri Gakkai (INMM) Nippon Shibu Dai-34-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2013/10

no abstracts in English

JAEA Reports

Investigation on dose rate reduction at Fukushima University Junior High School and Kindergarten

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) ${it In-situ}$ 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.

Journal Articles

Trial plan for advanced NDA system of uranium wastes; Introduction of active neutron method applied to NDA system

Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi; Haruyama, Mitsuo; Takase, Misao; Ozu, Akira; Kureta, Masatoshi

Kaku Busshitsu Kanri Gakkai (INMM) Nippon 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 $$^{234}$$U($$alpha$$,n) reaction using $$^{3}$$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 $$^{3}$$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.

Journal Articles

Measurement system modification for advanced NDA system of uranium wastes; Performance evaluation of active neutron method applied to NDA system

Haruyama, Mitsuo; Takase, Misao; Ozu, Akira; Kureta, Masatoshi; Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi

Kaku Busshitsu Kanri Gakkai (INMM) Nippon Shibu Dai-33-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2012/10

no abstracts in English

JAEA Reports

On performance experience and measurements with Ningyo Waste Assay System (NWAS), 2

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 $$gamma$$ 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 ($$^{3}$$He) proportional counters for neutron detection. The neutron measurement methodology is consist of $$^{234}$$U ($$alpha$$,n)F reaction and spontaneous fission of $$^{238}$$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.

JAEA Reports

On performance experience and measurements with Ningyo Waste Assay System (NWAS)

Zaima, Naoki; Nakashima, Shinichi; Kaneda, Koji; Kado, Kazumi

JAEA-Technology 2010-046, 31 Pages, 2011/02

JAEA-Technology-2010-046.pdf:2.84MB
JAEA-Technology-2010-046(errata).pdf:0.05MB

The uranium mass assay systems for 200-litter wastes drums applied neutron and $$gamma$$ 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 $$gamma$$ 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 $$gamma$$ 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.

Journal Articles

Uranium refining and conversion plant decommissioning project

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

Oral presentation

Measurement technology of uranium quantity in radioactive waste, 3; Validation by numerical simulation and experiment

Zaima, Naoki; Sugitsue, Noritake; Takahashi, Nobuo; Yokoyama, Kaoru; Suzuki, Yasuo*; Muroi, Masayuki*

no journal, , 

no abstracts in English

Oral presentation

Measurement technology of uranium quantity in radioactive waste, 2; Development of mathematical scheme

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 ($$^{238}$$U) filled in waste drums using passive $$gamma$$ ray measurement. We proposed a new evaluation function which gives a unique relation between source positions and $$gamma$$ ray count rate.

Oral presentation

On performance experience and measurements with Ningyo Waste Assay System (NWAS)

Zaima, Naoki; Nakashima, Shinichi; Kaneda, Koji; Kado, Kazumi

no journal, , 

We developed uranium mass assay systems for 200-litter wastes drums applied neutron and $$gamma$$ 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 large sized NaI(Tl) scintillation detector for $$gamma$$-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 $$gamma$$-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 going to schedule 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 Los Alamos National Laboratory.

Oral presentation

Experiences of NWAS, 2

Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi

no journal, , 

We developed uranium mass assay systems for 200-litter wastes drums applied neutron and $$gamma$$ 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 $$gamma$$ 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 $$gamma$$ 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.

Oral presentation

Measurement technology of uranium quantity in radioactive waste, 2; 3D measurement technique for make density uniform

Yokoyama, Kaoru; Zaima, Naoki; Takahashi, Nobuo; Sugitsue, Noritake; Suzuki, Yasuo*; Muroi, Masayuki*

no journal, , 

For determining radioactivity ($$^{238}$$U) of waste drums using $$gamma$$ ray measurement, we derived the geometric mean of measurements at various positions on spherical surface surrounding the waste drum to create the approximately homogeneous waste density.

Oral presentation

Measurement technology of uranium quantity in radioactive waste, 1; Feasibility study for measurement method of uranium quantity in radioactive waste with complexity and high density

Sugitsue, Noritake; Yokoyama, Kaoru; Zaima, Naoki; Takahashi, Nobuo; Suzuki, Yasuo*; Muroi, Masayuki*

no journal, , 

A simple evaluation of the coverage of the computing model was done. The density of waste and the radiation source distribution were calculated as a parameter. As a result, It has been understood that the application of the computing model is difficult in the ingot of the metal including the uranium.

Oral presentation

NWAS; Developments for passive uranium assay system

Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi

no journal, , 

We developed uranium mass assay systems for 200-litter wastes drums applied neutron and $$gamma$$ 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 $$gamma$$ ray detection. The neutron measurement methodology is consist of U-234 ($$alpha$$,n) reaction and $$gamma$$ 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.

Oral presentation

Experiences of NWAS, 3

Zaima, Naoki; Nakashima, Shinichi; Nakatsuka, Yoshiaki; Kado, Kazumi

no journal, , 

We developed uranium mass assay systems for 200-litter wastes drums applied neutron and $$gamma$$ measurements by NDA method. The systems are composed of the 16 pieces of Helium-3 proportional counters for neutron detection with 100 mm thickeness polyethylene and a Ge-SSD for $$gamma$$ ray detection. The neutron measurement methodology is consist of $$^{234}$$U ($$alpha$$,n) reaction and $$gamma$$ measurement is applied by Ge-SSD. The extensive testing trials using the known amount of uranium with different enrichment and some kinds of matrices in drums were performed. By using this system we tried to determine uranium mass in drums for the purpose of reduction MUF in URCP.

Oral presentation

A Trial for the active assay of uranium bearing wastes

Zaima, Naoki; Nakatsuka, Yoshiaki; Nakashima, Shinichi; Kureta, Masatoshi; Ozu, Akira; Takase, Misao

no journal, , 

The passive assay system based on ($$alpha$$,n) neutron counting generated from alpha-ray for uranium bearing wastes drums had been developed. The passive neutron assay system is, therefore it has been inevitable its scarce neutron response and chemical form dependence. Therefore the improvements for detection response and less matrix dependence have also been started. The new measurements systems are equipped helium-3 counters, 14 MeV neutron generator and concrete shielding. The trials for accumulating data used uranium sources have also been started successfully.

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