Designs and Experiments for Studies of Fast Neutron Fields at the RB Reactor

The RB reactor is a heavy water critical assembly that has been in operation since 1958 using, at different times, natural metal uranium, 2% enriched metal uranium, and 80% enriched aluminium dioxide fuel of Soviet origin. A feasibility study of the RB reactor as a fast neutron source began in 1976, and four versions of fast neutron fields around or in the reactor were designed through 1990: an external neutron converter (ENC) in 1976; an experimental fuel channel (EPC) in 1982, an internal neutron converter (lNC) in 1983, and a coupled fast-thermal core (HERBE) in 1990. This paper presents an overview of the characteristics and experimental applications of each particular fast neutron field mentioned above, including available irradiation space, neutron spectra, and equivalent neutron and gamma dose rates. Control and safety-related implications of these modifications are emphasized. The computer codes and nuclear data libraries used in calculations are described briefly. (author)