Radiological dose calculations for the particle beam fusion accelerator upgrade (PBFA-U)

Biological dose rate calculations are performed for different locations in the vicinity of the target chamber and diode of the particle beam fusion accelerator upgrade (PBFA-U) facility. The facility is to be used for research on light ion beam driven inertial confinement fusion. Depending on the diagnostic shots, Bremsstrahlung radiation as well as neutrons are produced. On interacting with the diode material, the Bremsstrahlung radiation results in the emission of photoneutrons. Results of the activation analysis show that photoneutron production has a negligible contribution to the dose rate at the outer casing of the diode following fusion shots. The dose rates are dominated by the contribution from fusion neutrons streaming into the diode. The dose rate in the vicinity of the diode following non-fusion shots is minimal, allowing it to be accessed immediately for hands-on maintenance. However, several shifts of maintenance personnel are required if the outer casing of the diode needs to be accessed following fusion shots to minimize individual exposure. The use of steel as structural material for the chamber and diode casing results in lower dose rates compared with the use of aluminum for up to several months following fusion shots. Using steel, chamber and diode can be accessed 1 day after shots for a maximum of 15 min per maintenance shift. Using the aluminum alloy would delay hands-on maintenance to several days following shots.