Calculation of decay gamma spectrum of the HTTR after shutdown

Ho, H. Q.   ; 濱本 真平  ; 藤本 望*; 長住 達; 後藤 実  ; 石塚 悦男   

Ho, H. Q.; Hamamoto, Shimpei; Fujimoto, Nozomu*; Nagasumi, Satoru; Goto, Minoru; Ishitsuka, Etsuo

Calculation of the decay gamma heat distribution in the graphite moderator of the HTTR is important because it affects the recriticality of the reactor during LOFC test. In another respect, the auxiliary Cf-252 neutron source of the HTTR must be replaced after a few years. So, a secondary neutron source, such as neutron emitted from (,n) reaction on beryllium target, is considered for replacement of the Cf-252 source. For the two problems above, it is necessary to calculate the decay gamma distribution in the reactor after reactor shutdown. In this study, the decay gamma spectrum in the HTTR block was calculated by using MCNP6 and ORIGEN. The gamma spectrum from ORIGEN will become a source term in further MCNP calculation to calculate the gamma distribution in the fuel block of the HTTR.