A series of shutdown dose rate (SDDR) calculations has been performed for the 1.125-MW high-power beam dump following deuteron beam operations in the linear International Fusion Materials Irradiation Facility prototype accelerator (LIPAc). The SDDRs were calculated based on the activation of the beam dump materials caused by nuclear reactions with deuterons and secondary neutrons, which are generated through deuteron interaction in the beam dump.

This study evaluated the SDDR using the actual chemical composition for 5-MeV and 9-MeV deuteron beam operations. The necessity of assessing the SDDR with consideration of the contributions from both deuterons and secondary neutrons has been clarified, as these contributions vary depending on location, deuteron energy, operation time, and cooling times.

The SDDR resulting from Cu(d,x) reactions during 5-MeV deuteron operation decreased relatively quickly with longer cooling times compared to the 9-MeV operation. As the operation time increased, the SDDR tended to decay more slowly due to the increased contribution of long-lived radionuclides. Therefore, the operation scenario must be determined based on the SDDR around the beam dump to ensure safe hands-on maintenance.

Preliminary use of the 5-MeV deuteron beam is considered a preferable method to test the LIPAc’s high-duty–cycle or high-beam–current operation before conducting the 9-MeV deuteron beam operation in order to reduce the SDDR around the beam dump during copper cone hands-on maintenance.