GAMMA-FIELDS AND DOSE-FIELDS AROUND THE PRIMARY CIRCUIT OF A HELIUM-COOLED FUSION POWER-PLANT

The Monte Carlo code MCNP-4 has been used to determine the photon flux spectra around two important regions of the primary circuit of the co nceptual SEAFP Plant Model 1 (PM-1) fusion power plant. These fluxes h ave been converted to absorbed dose rates in human tissue by using dos e rate conversion factors. Dose rates around a 'hot-leg' pipe were fou nd to be low and not significantly above naturally occurring backgroun d levels. The dose fields surrounding a steam generator were found to be higher than the 'hot-leg' pipe, but still well within acceptable li mits. Dose rates inside the steam generator shell are considerably hig her and would probably require remote and robotic method for inspectio n and maintenance tasks. The annual occupational radiation exposure to all plant workers was estimated to be approximately 170 man-mSv year( -1), which is similar to the levels experienced with modern PWRs, afte r decades of optimisation. (C) 1997 Elsevier Science S.A.