Monte carlo calculation of the neutron effective dose rate at the outer surface of the biological shield of HTR-10 reactor

Research on experimental reactors, such as HTR-10, provide useful data about potentialities of very high temperature gas-cooled reactors (VHTR). The latter is today rated as one of the six nuclear reactor types involved in the Generation-IV International Forum (GIF) Initiative. In this study, the MCNP5 code has been employed to evaluate the neutron radiation trend vs. the biological shield's thickness and to calculate the neutron effective dose rate at the outer surface. The reactor's geometry has been completely modeled by means of lattices and universes provided by MCNP, even though some approximations were required. Monte Carlo calculations have been performed by means of a simple PC and, as a consequence, in order to obtain acceptable run times, it was made an extensive recourse to variance reduction methods.

► We deal with HTR-10, that is a helium-cooled graphite-moderated pebble bed reactor.
► We carried out Monte Carlo simulation of the core by MCNP5.
► Extensive use of MCNP5 variance reduction methods has been done.
► We calculated the trend of neutron flux within the biological shield.
► We calculated neutron effective dose at the outer surface of biological shield.