Production and detection of fission-induced neutrons following fast neutron direct interrogation to various dry materials containing U

Sakoda, 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

https://doi.org/10.1080/00223131.2017.1417175

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.

Study of the neutron multiplication effect in an active neutron method

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

https://doi.org/10.1080/00223131.2017.1359118

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.

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

Nihon Genshiryoku Gakkai Wabun Rombunshi, 15(2), p.115 - 127, 2016/06

https://doi.org/10.3327/taesj.J15.011

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.

2013 training using JMTR and related facilities as advanced research infrastructures

Takemoto, Noriyuki; Kimura, Nobuaki; Hanakawa, Hiroki; Shibata, Akira; Matsui, Yoshinori; Nakamura, Jinichi; Ishitsuka, Etsuo; Nakatsuka, Toru; Ito, Haruhiko

JAEA-Review 2013-058, 42 Pages, 2014/02

JAEA-Review-2013-058.pdf:4.95MB

Practical training courses using the JMTR and related facilities as an advanced research infrastructures have been carried out in Japan Atomic Energy Agency since FY2010 from a viewpoint of the nuclear human resource development and the securing. In FY2013, "Training course for foreign young researchers and engineers" was carried out from July 8th to July 26th, and "Training course using JMTR and related facilities as advanced research infrastructures" for domestic young researchers and engineers was carried out from July 29th to August 9th. 18 young researchers and engineers were joined in each training course, and 36 trainees in total studied about basic nuclear research and technology through the lecture and training about the reactor operation management, safety management, irradiation test, etc. in the JMTR. The results of these courses are reported in this paper.

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) 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.

Research of flaw assessment method for beryllium reflector elements

Shibata, Akira; Ito, Masayasu; Takemoto, Noriyuki; Nakatsuka, Masafumi*; Ohara, Hiroshi*; Kodama, Mitsuhiro*; Tanimoto, Masataka; Tsuchiya, Kunihiko

JAEA-Technology 2011-034, 67 Pages, 2012/02

JAEA-Technology-2011-034.pdf:6.94MB

Reflector elements made from metal beryllium is widely used as neutron reflectors to increase neutron flux in test reactors. When beryllium reflector elements are irradiated by neutron, bending of reflector elements caused by swelling occurs, and beryllium reflector elements must be replaced in several years. In this report, investigation for non-destructive inspection method of metal Beryllium and experiments for Preliminary inspection to establish post irradiation examination method for research of characteristics of metal beryllium under neutron irradiation were reported.

Mutation induction in using ion beam irradiation

Kobayashi, Nobuo*; Kano, Sayaka*; Sasaki, Shinichiro*; Tasaki, Keisuke*; Nakatsuka, Akira*; Nozawa, Shigeki; Hase, Yoshihiro; Narumi, Issei

JAEA-Review 2009-041, JAEA Takasaki Annual Report 2008, P. 77, 2009/12

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2009-041.pdf

Mutation induction in azalea seedlings using ion beam irradiation

Kobayashi, Nobuo*; Tasaki, Keisuke*; Kano, Sayaka*; Sakamoto, Sakiko*; Nakatsuka, Akira*; Hase, Yoshihiro; Narumi, Issei

JAEA-Review 2008-055, JAEA Takasaki Annual Report 2007, P. 70, 2008/11

https://jopss.jaea.go.jp/pdfdata/JAEA-Review-2008-055.pdf

no abstracts in English

Effect of rod bowing on critical power based on tight-lattice 37-rod bundle experiments

Tamai, Hidesada; Kureta, Masatoshi; Liu, W.; Sato, Takashi; Nakatsuka, Toru; Onuki, Akira; Akimoto, Hajime

Journal of Nuclear Science and Technology, 45(6), p.567 - 574, 2008/06

https://doi.org/10.3327/jnst.45.567

The confirmation of thermal-hydraulic performance is one of the most important requirements for the design of the FLWR. A large-scale thermal-hydraulic experiment using a tight-lattice 37-rod bundle test section with a bowed rod was carried out with pressure ranging from 2-9 MPa and mass velocity at 200-1000 kg/(ms). It was confirmed that boiling transition (BT) occurs downstream of the rod contact point, and that the wall temperature trace during the BT follows the typical BT pattern of BWR. Critical power with a bowed rod is about 10 percent lower than that without rod bowing. The critical power increases monotonically with increase in mass velocity, with decrease in inlet water temperature, and with decrease in exit pressure, and these trends are similar to those of the basic bundle without rod bowing. Thus, there is negligible effect of rod bowing on the dependence of critical power on the mass velocity, the inlet temperature and the exit pressure.

EUV light source by high power laser

Izawa, Yasukazu*; Nishihara, Katsunobu*; Tanuma, Hajime*; Sasaki, Akira; Murakami, Masakatsu*; Sunahara, Atsushi*; Nishimura, Hiroaki*; Fujioka, Shinsuke*; Aota, Tatsuya*; Shimada, Yoshinori*; et al.

Journal of Physics; Conference Series, 112, p.042047_1 - 042047_4, 2008/00

https://doi.org/10.1088/1742-6596/112/4/042047

In the development of a high power EUV source used in the EUV lithography system, we have been constructed EUV database of laser-produced tin plasma by the theoretical and experimental studies. On the basis of our understanding, the optimum conditions of lasers and plasmas were clarified, and we proposed the guidelines of laser plasma to obtain clean, efficient and high power EUV source for the practical EUV lithography system. In parallel to such studies, novel targets and high power laser system to generate the optimized EUV source plasma have been developed.