Evaluation of dose rate and reactor core and nuclear properties for superconductive magnets in ITER

Abstract

Abstract Dose rate, nuclear heating and radiation damage during the operation of 1 MWa m−2 neutron first wall loading, and induced activity, decay heat and dose rate after shutdown of 1 MWa m−2 neutron first wall fluence operation were estimated in ITER. The maximum nuclear heating rate in a winding pack of the toroidal field coils (TFCs) is less than 1 mW cm−3 at positions around the exhaust and open horizontal ducts. A thickness of 20 and 40 cm, respectively, in each type of duct wall composed of 65% stainless steel and 35% water, is sufficient to protect the TFCs from radiation. The maximum displacement damage, 10.3 dpa, appears at the first wall on the mid-plane. The maximum helium production at the back plate is 0.2 appm at the inboard on the mid-plane for the first wall neutron fluence of 1 MW m−2. The activity in the inboard blanket 1 day after shutdown is 1.5 × 1011 Bq cm−3, and the average decay heating rate is 0.01 W cm −3. The dose rate outside the 120 cm-thick concrete biological shield is two orders higher than the design criterion of 10 μSv h−1. This indicates that the biological shield thickness should be increased by 50 cm more of concrete to give a total thickness of 170 cm to allow workers to enter the reactor room and to carry out maintenance tasks.