Risk assessment of the mercury leak at Materials & Life Science Experimental Facility of J-PARC

Kasugai, Yoshimi  ; Kai, Tetsuya   

Evaluations of radiation dose at the site boundary for the Materials and Life Science Experimental Facility (MLF) at J-PARC were carried out supposing that the mercury used as the neutron target happened to leak from the mercury circulation system during 1 MW operation. As a result of the evaluation, the dose of external exposure at the site boundary was estimated to be 30Sv, which was almost given by the radioactive noble gas produced via spallation reactions. The inner exposure of radioactive mercury and tritium was estimated to be 0.1Sv in total. Since the estimated dose was enough low in comparison with a personal annual dose from natural radioactivity, even though the event scenario was made conservatively, it was shown that MLF has high safety margin for the leak of radioactivity.