FAST NEUTRON FLUX IN A MOCKUP OF SM-1A CORE AND VESSEL

Flux measurements were made in a cold (68 deg F) mockup of the SM-1A reactor core, thermal shields, and pressure vessel. Neutron flux distributions were mapped in radial and axial directions by means of detector foils to cover thermal, resonance, and fast neutron energy ranges. Multigroup calculations were also made for this cold mockup, using the P1MG-2 and PDQ (rz)/-2 codes. These results were correlated with hot (430-440 deg C) measurements and calculations of the fast flux above 1 Mev in the SM-1A reactor, in order to assist in prediction of radiation damage effects on the pressure vessel. The experimental results were up to 30% higher than calculated flux value. The best estimate of the fast flux above 1 Mev at the pressure-vessel surface was 4.1 x 10/sup 3/ n/cm/sup 2/- sec-w for the cold mockup (68 deg F) and 9.4 x 10/sup 3/ n/cm/sup 2/sec-w, for operating conditions (440 deg F). (auth