Dose Rate Analyses for the High Energy Beam Transport Section of IFMIF

This work presents neutronic analyses to support the layout of the high energy beam transport (HEBT) section of the IFMIF neutron source in the framework of the Broader Approach (BA) EVEDA activities. In the HEBT section, neutron back streaming from the lithium target can cause significant damage to accelerator components and result in their activation. In order to estimate the resulting radiation doses, detailed neutron and photon flux distributions inside the Target Interface Room (TIR) and the Radiation Isolation Room (RIR) during operation are evaluated by using the Monte Carlo code McDeLicious, which is an enhancement to MCNP5. The obtained results show that the major contribution to the TIR dose during operation will come from neutrons streaming from the target through the beam ducts and from secondary photons produced in these parts. It seems to be impossible to use any semiconductor devices inside TIR, while for mechanical devices there should be no problem. The dose after shutdown due to decay gammas was preliminarily estimated for the beam duct at the most activated place in TIR. In order to reduce the shutdown dose rate, the use of a low-Mn-content aluminium alloy is proposed.