Application of Monte Carlo method to solve the neutron kinetics equation for a subcritical assembly

Iwanaga, Kohei*; Sekimoto, Hiroshi*; Mori, Takamasa

Journal of Nuclear Science and Technology, 45(11), p.1099 - 1107, 2008/11

https://doi.org/10.3327/jnst.45.1099

The Monte Carlo method is applied to solve the space-dependent kinetics equations of transient in source-driven subcritical systems whose change is much slower than the prompt neutron lifetime. In the present paper, the time derivative of neutron equation is set zero, though the time derivative of delayed neutron precursor equation is treated without any approximations. The neutron counts measured by small fission chambers at the subcritical kinetics experiment using JAEA FCA are compared with those calculated by the present method. The agreement is good, and the excellent performance of our method for space dependent neutron kinetics is shown.

Research and development programme on ADS in JAEA

Oigawa, Hiroyuki; Nishihara, Kenji; Sasa, Toshinobu; Tsujimoto, Kazufumi; Sugawara, Takanori; Iwanaga, Kohei; Kikuchi, Kenji; Kurata, Yuji; Takei, Hayanori; Saito, Shigeru; et al.

Proceedings of 5th International Workshop on the Utilisation and Reliability of High Power Proton Accelerators (HPPA-5), p.387 - 399, 2008/04

JAEA has been promoting the research and development on accelerator-driven subcritical system (ADS) as a dedicated system for the transmutation of long-lived radioactive nuclides. The ADS proposed by JAEA is a lead-bismuth eutectic cooled, tank-type subcritical reactor with the thermal power of 800 MWth driven by a 30 MW superconducting linac. As for the design study of the future ADS, reduction of the maximum temperature of fuel claddings and verification of the feasibility of the beam window are under way. As for the Transmutation Experimental Facility (TEF) of the J-PARC project, design study including experimental device to deal with minor actinide fuels is being conducted. To facilitate the research and development on ADS, a common road map is necessary to be shared by international communities. The TEF program can play an important role in such an international context as an experimental platform to conduct basic and flexible experiments.

Neutronics design for power flattening of accelerator-driven system

Iwanaga, Kohei; Nishihara, Kenji; Tsujimoto, Kazufumi; Kurata, Yuji; Oigawa, Hiroyuki

JAEA-Research 2007-025, 42 Pages, 2007/03

JAEA-Research-2007-025.pdf:3.37MB

Japan Atomic Energy Agency (JAEA) promotes research and development of Accelerator-Driven system (ADS) to reduce the burden for conditioning and disposal of the high level radioactive waste by transmuting minor actinide (MA). In the present neutronics design, we investigated several methods to reduce the power peak, and showed the reduction of the temperature of cladding tubes and influence to the beam current. These methods are adjustment of inert matrix content in fuel in each burn-up cycle, multi-region design in terms of plutonium enrichment, pin radius and inert matrix content, modification of the level of the beam window position and height of the central fuel assemblies. As the result, the maximum temperature at the surface of fuel cladding tubes can be reduced by 110 C by combining the adjustment of inert matrix content in each burn-up cycle and multi-regin design in terms of pin radius or inert matrix content.

Measurement of infinite multiplication factor in the mock-up core for reduced-moderation water reactor at FCA

Kojima, Kensuke; Okajima, Shigeaki; Yamane, Tsuyoshi; Ando, Masaki; Kataoka, Masaharu*; Iwanaga, Kohei

JAERI-Tech 2004-016, 38 Pages, 2004/03

JAERI-Tech-2004-016.pdf:1.46MB

To investigate the void coefficient in the Reduced-Moderation Water Reactor (RMWR), an infinite multiplication factor was measured in the FCA-XXII-1 (65V) core. Axial and radial fission rate distributions were measured by micro fission chambers with four different kinds of nuclides. The infinite multiplication factor was derived from the material buckling, which was obtained from both the axial and radial fission rate distributions, and the migration area calculated. The value of it in the test region of the FCA-XXII-1 (65V) core was 1.3440.034. It was compared with the calculation, the ratio of the calculation to the measurement was 1.0080.026. The improvement in measurement accuracy was also considered.

Determination of reactivity and source intensity based on the maximum likelihood method

Nishihara, Kenji; Iwanaga, Kohei; Yamane, Tsuyoshi; Okajima, Shigeaki

JAERI-Research 2002-030, 63 Pages, 2002/12

JAERI-Research-2002-030.pdf:3.81MB

During the experiments using the critical assembly such that reactivity is added to the stationary state and the core shifts to the other stationary state, the neutron flux transitionally changes after some change of the reactivity or source. Inverse kinetics method (IK method) can generally adopted as the technique of obtaining the reactivity and/or source by analyzing the neutron flux. However, the conventional analysis method was not able to obtain the solution with the maximum likelihood considering the error of the measured neutron flux and to estimate the error of the solution. In the present research, by adopting the maximum likelihood methodology to the problem, developed is the technique to obtain the reactivity and source intensity with maximum likelihood and the errors of them. Moreover, the technique is applied to the rod drops experiment in FCA, and the validity of a technique is checked.

Study of an epithermal neutron generator for BNCT using 400 MeV protons

Tahara, Yoshihisa*; Abe, Shinji*; Yonai, Shunsuke*; Baba, Mamoru*; Unno, Yasuhiro*; Sasa, Toshinobu; Iwanaga, Kohei; Yokobori, Hitoshi*; Tsutsui, Takehiko*; Kamei, Yoshihide*

no journal, , 

To realize the boron neutron capture therapy, the existence of the method using the 400 MeV proton beam, which is planned to supply the J-PARC transmutation experimental facility, are studied. As the preliminary examination, a method to obtain epithermal neutron using neutrons which generated by Ta target bonbarded by 400 MeV protons and moderated with iron and fluental moderators. To suppress the unexpected exposure, lead reflector is located around the target and moderators. By the preliminary analysis using MCNPX code and LA150 cross section library, the beam current about 5 micro ampere are enough for effective for brain-canther treatment.