Non-destructive analysis of impurities in beryllium, affecting evaluation of the tritium breeding ratio

The non-destructive, pulsed neutron method was used as the most effective way of analyzing the integral effect of impurities in beryllium, relevant to the tritium breeding ratio evaluation. The integral effect was evaluated from time behavior observations of the neutron flux, following the injection of a burst of D–T neutrons into the beryllium assembly. The assembly was constructed from the structural beryllium grade S-200F (Brush Wellman Inc.). Experimental data were compared with the reference data and MCNP-4B calculations. Results show that the measured absorption cross section of thermal neutrons in beryllium blocks is approximately 30% larger than the calculated value, based on the data, specified by the manufacturing company. Impurities in beryllium, such as Li, B, Cd and others, affect the absorption cross section even if the content of impurities is less than 10 ppm.