Design of low heating field in JMTR

Imaizumi, Tomomi; Takemoto, Noriyuki ; Nagao, Yoshiharu  

The renewed and upgraded JMTR will start from FY 2011. The JMTR will be use to irradiation test about lifetime extension of light water reactors (LWRs), progress of science and technology, and expansion of industry use. To lifetime extension of LWRs, it is demanded the irradiation test to confirm integrity of reactor structural materials such as stainless steel and concrete, etc. In irradiation tests of concrete sample, it is necessary to keep low irradiation temperature to prevent dehydration of cement hydrates or thermal stress. However, irradiation samples are heated by rays. On the other hand, neutron irradiation test in low heating field is effective as progress of science and technology such as materials basic research. Therefore, the neutron irradiation field of low heating rate was designed in JMTR. In this study, it was considered that the heating rate is below 0.07 W/g in the JMTR core so as not to become higher temperature as planned.