| Co-Investigator(Kenkyū-buntansha) |
MURAMATSU Toshiharu Japan Nuclear Cycle Development Institute, O-arai Engineering Center, Principal Investigator, 大洗工学センター・要素技術開発部, 主任研究員
SAWADA Tetsuo Tokyo Institute of Technology, Research Laboratory for Nuclear Reactor, Assistant, 原子炉工学研究所, 助手 (20235469)
ZIMIN Vchaeslav Japan Atojmic Energy Research Institute, Tokai Institute, Research Associate
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| Research Abstract |
The objective of this work is to clarify local instantaneous and/or microscopic behaviors of the transport phenomena and relate them to their macroscopic behaviors. The information is not available experimentally in most cases and is necessary to establish macroscopic modeling of the phenomena that include transient behaviors of local neutron flux, coolant and molten materials motion in nuclear reactors. First, a parallel computation version of the Monte Carlo code, MVP, was transplanted on a Unix OS, I.e., Linux platform and was used to perform neutron transport calculations. The MVP code is to provide the microscopic behaviors of neutrons and here the code is used to quantitatively evaluate the reactivity feedback from the molten fuel motion. This type of calculations had required a huge amount of computing resources but thanks to the parallel processing of the PC cluster, it was revealed that the calculation could be carried out with relatively low cost. Based on this Monte Carlo co
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de system, an accuracy of the neutron multiplication factor was evaluated for an intact core and then for a compaction of the molten core of a metal fuel fast reactor. The result was forwarded to improve a reactivity feedback model of an FBR transient analysis code with one point kinetics model that describes macroscopic behaviors of neutrons. Second, a space dependent neutron kinetics code was developed based on the modern nodal analysis method. A new model of the subassembly discontinuity factor was introduced to improve correlations between microscopic and macroscopic phenomena. Then the analysis of regional instability of a BWR core was performed and compared to the actual plant data to confirm validity of the modeling. Finally, for thermal hydraulics, a pseudo direct numerical simulation code for turbulent flows was developed and applied to flows in a duct and between parallel plates. Microscopic information obtained included the wall shear stress distributions on a heated wall and temperature distributions with the influences of the secondary flows originated from the an isotropic turbulence properties. The microscopic information was integrated into such macroscopic modeling as friction factor and heat transfer coefficients. Most phenomena pertaining to two-phase flows are a result of extremely complicated sum of microscopic motion of fluids and hardly calculated numerically. As an example, a macroscopic approach was proposed based on the principle of minimum entropy production to delineate two-phase flow redistribution inside multi-subchannel flow system. Less
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