REACTOR NOISE ANALYSIS FOR A GRAPHITE-MODERATED AND -REFLECTED CORE IN KUCA

EPJ Web of Conferences

Sakon Atsushi¹  Hohara Shin-ya¹  Hashimoto Kengo¹  Takahashi Kazuki²  Nakajima Kunihiro²  Sano Tadafumi³  Fukaya Yuji⁴ 

[1] Atomic Energy Research Institute, Kindai University;Graduate School of Science and Engineering, Kindai University;Institute for Integrated Radiation and Nuclear Science, Kyoto University;Japan Atomic Energy Institute;

关键词: graphite core;    reactor noise;    power spectrum method;    prompt-neutron decay constant;   

DOI  :  10.1051/epjconf/202124709009

来源: DOAJ

【 摘 要 】

In graphite-reflected thermal reactors, even a detector placed far from fuel region may detect a certain degree of the correlation amplitude. This is because mean free path of neutrons in graphite is longer than that in water or polyethylene. The objective of this study is experimentally to confirm a high flexibility of neutron detector placement in graphite reflector for reactor noise analysis. The present reactor noise analysis was carried out in a graphite-moderated and -reflected thermal core in Kyoto University Critical Assembly (KUCA). BF3 proportional neutron counters (1” dia.) were placed in graphite reflector region, where the counters were separated by about 35cm and 30cm -thick graphite from the core, respectively. At a critical state and subcritical states, time-sequence signal data from these counters were acquired and analyzed by a fast Fourier transform (FFT) analyzer, to obtain power spectral density in frequency domain. The auto-power spectral density obtained from the counters far from the core contained a significant degree of correlated component. A least-squares fit of a familiar formula to the auto-power spectral density data was made to determine the prompt-neutron decay constant. The decay constant was 63.3±14.5 [1/s] in critical state. The decay constant determined from the cross-power spectral density and coherence function data between the two counters also had a consistent value. It is confirmed that reactor noise analysis is possible using a detector placed at about 35cm far from the core, as we expected.

【 授权许可】

Unknown