Activation of water in the cooling system at the pulsed spallation neutron source, KENS

We measured the radioactivity of Be-7 and H-3 in the ambient-temperature water moderator cooling system at the pulsed spallation neutron source, KENS, The detected activity of H-3 in cooling water was in agreement with the production estimated from the neutron flux obtained from a neutronic calculation, however, the results of 7Be was only about 0.1% of the estimation. We tried to investigate the distribution of Be-7 trapped in the cooling system. We also measured the time constants of the trapping process, and the result suggests that a large amount of the produced 7Be is trapped in parts of the cooling system with a very short time constant. (C) 1999 Elsevier Science Ltd. All rights reserved.