Study of an Optimum Design for Subcritical Neutron Multipliers Using Californium-252 Neutron Sources

Calculations are performed to determine the optimum design of a subcritical assembly for multiplying a ²⁵²Cf source. Subcritical experiments have been performed in a TRIGA research reactor to verify the calculational techniques. These experiments included measurements of

1. subcritical multiplication
2. fast adjoint and thermal fluxes
3. the thermal flux index (defined as the ratio of the thermal flux to the source strength).

Good agreement was generally found between the theoretical and experimental values. The study shows that a sufficiently intense thermal flux can be attained for neutron activation analysis using a relatively inexpensive, simple, and safe multiplying assembly and a ²⁵²Cf source. It is anticipated that the system could be installed in such service facilities as hospitals and laboratories for use in activation analysis, radioisotope production, and/or neutron radiography.