AN INVESTIGATION OF THE ACTIVATION OF WATER BY D-T FUSION NEUTRONS AND SOME IMPLICATIONS FOR FUSION-REACTOR TECHNOLOGY

Several fundamental aspects of the activation of water by neutrons in D-T fusion systems have been investigated in this work. The basic phys ical principles involved and the status of pertinent nuclear cross-sec tion and radioactivity data were reviewed. The integral response of th e dominant O-16(n,p)N-16 reaction was calculated using several evaluat ed differential cross-section representations and characteristic D-T f usion neutron spectra. The impact of cross-section uncertainties was a lso assessed in this context. Two integral experiments were carried ou t at a D-T neutron generator facility to investigate the production an d transport of N-16 radioactivity in a D-T fusion neutron environment. Radioactivity yield data were acquired in one of these integral exper iments (IE-1) and the measured results were compared with values obtai ned from calculations which employed both analytical and Monte-Carlo t echniques. Measurements on the shielding of high-energy gamma rays fro m N-16 decay by stainless steel (SS-304) and copper were performed in an additional integral experiment (IE-2) and these data were interpret ed by a combination of analytical calculations and Monte-Carlo simulat ion. Some consequences of neutron-induced N-16 radioactivity in the co oling water of a fusion reactor were examined for two contemporary con ceptual designs of the International Thermonuclear Experimental Reacto r (ITER). This analysis benefitted from insight acquired through the p resent integral studies. It was found that this radioactivity generati ng process would lead to significant biological doses outside the reac tor containment vessel and could also deliver potentially damaging rad iation doses to superconducting magnet insulators unless care is taken to provide adequate shielding when designing a fusion reactor. (C) 19 97 Elsevier Science S.A.