An assessment of Boraflex performance in spent-nuclear-fuel storage racks: Final report

Data from utility surveillance programs, test reactor irradiations and the open literature have been collected and evaluated to assess the effect of service environment in spent nuclear storage racks on the neutron absorber material, Boraflex. Radiation induced changes in the properties of Boraflex have been identified. The observed formation of gaps in the full length panels of Boraflex in some spent fuel racks has been attributed to one such change, shrinkage, in combination with mechanical restraint. Mechanisms of gap formation and growth are also discussed. Factors which may influence the ultimate service life of Boraflex in spent fuel storage racks have been identified. Continuation of coupon surveillance programs to verify the serviceability of Boraflex in the spent fuel pool environment is recommended. Guidelines for coupon surveillance programs have been developed. 65 refs., 30 figs., 8 tabs