Radiation dose assessment of 7Be and activated corrosion products present in the hydrogen trap of IFMIF-DONES lithium system

The radiological impact that 7Be and activated corrosion products (ACP) dissolved in Li could have in normal
operation and maintenance in the surroundings of the hydrogen trap (HT) of future IFMIF-DONES facility has
been assessed. Ambient dose equivalent rates were calculated with radiation transport program MCNP at half
height of trap. Four different Y contents were considered in the trap: 1, 3, 5 and 8 kg. In normal operation dose
rates in the range 13.7–15.1 mSv/h have been found in contact with the trap and 0.28–0.31 mSv/h at 1 m of the
trap. 7Be has a very low contribution to dose (3–3.7 μSv/h). Dose simulations have shown that a concrete wall 30
cm thick can reduce dose rates to acceptable dose limits. In maintenance operation the trap is drained and Li film
remains attached to Y pebbles. Three possible Li film thickness have been considered: 10, 50 and 100 μm.
Estimated 7Be activity is below exemption limits during maintenance. Assessed dose rates are in the range
34–1420 μSv/h at contact with the trap and a maximum of 10.9 μSv/h at 1 m of the trap.