Study on improvement of reactor physics analysis method for FBRs with various core concept

*; Kitada, Takanori*; Tagawa, Akihiro; *; Takeda, Toshikazu*

JNC TJ9400 2000-006, 272 Pages, 2000/02

JNC-TJ9400-2000-006.pdf:9.69MB

Investigation was made on the follwing three themes as a part of the improvement of reactor physics analysis method for FBR with various core concept. Part 1: Investigation of Error Estimation of Neutron Spectra in FBR and Suggestions to Improve the Accuracy. In order to improve the spectrum unfolding method used in fast experimental reactor JOYO, a trial was made to evaluate the error in the estimated neutron spectrum, cause by cause. And the evaluated errors were summed up to obtain the most probable and reasonable error as possible. The summed up error was found relatively small compared to the error caused by the uncertainty of cross section data: most of the error in the spectrum unfolding method can be attributed to the error in cross sections. It was also found that the error due to the fission spectrum causes a considerable error in the high energy neutron spectrum which is over several MeV. Part 2: Study on Reactor Physics Analysis Method for Gas-Cooled FBR. In gas-cooled FBR, the portion of coolant channels in core volume is larger than sodium-cooled FBR. This leads to strong neutron streaming effects. For sodium-cooled FBR, several methods were proposed to evaluate the neutron streaming effect, however, these methods can not be used directly to gas-cooled reactor because the direction dependent diffusion coefficient becomes infinitive along the direction pararel to the coolant chammel. In this study, a new method is proposed to evaluate the neutron streaming effect, based on the method taking the axial buckling into consideration, which method was originally proposed by Khler. Part 3: Study on Reactor Physics Analysis Method for Water-Cooled FBR An investigation was made on low-moderated water-cooled FBR, on the point that the ordinary used analysis method for FBR may give considerable difference in results in such core. In light water reactors, it is well known that the space dependence of self-shielding effect of heavy nuclides are considerably ...

Mapping project in Fukushima and related researches, 7; Dose estimation of artificial / natural radioisotopes by an analysis of photon energy spectrum

Tsuda, Shuichi; Tanigaki, Minoru*; Saito, Kimiaki

no journal, , 

A GPS-aided radiation monitoring system KURAMA and the KURAMA-II developed by Kyoto University has been utilized after the Fukushima Dai-ichi Nuclear Power Plant accident in a mapping project of radionuclides deposited in the environment and monitoring of dose rates in air. KURAMA-II has a function of precisely evaluating dose rates in air based on measured pulse-height spectra from the incorporated CsI(Tl) scintillation detector. In this study, to evaluate dose contribution of the radionuclides in the environment, photon energy spectra was estimated by an unfolding method, using the measured pulse-height spectra and the dataset of the calculated response functions of the CsI(Tl) scintillation detector in a simulative environment. The results of dose contributions of artificial and natural radionuclides based on the estimation method will be reported in the session, "Mapping project in Fukushima and related researches".