Analysis and Results of a Hydrogen-Moderated Isotope Production Assembly in the Fast Flux Test Facility

A cobalt test assembly containing yttrium hydride pins for neutron moderation was irradiated in the Fast Flux Test Facility (FFTF) during cycle 9A for 137.7 equivalent full-power days at a power level of 291 MW. The 36 test pins consisted of a batch of 32 pins containing cobalt metal used to produce ⁶⁰Co and a set of four pins with europium oxide to produce ¹⁵³Gd, a radioisotope used in detection of the bone disease osteoporosis. Postirradiation examination of the cobalt pins determined the ⁶⁰Co production to be predictable to an accuracy of ∼5 %. The measured ⁶⁰Co spatially distributed concentrations were within 20% of the calculated concentrations. The assembly average ⁶⁰Co measured activity was 4% less than the calculated value. The europium oxide pins were gamma scanned for the europium isotopes ¹⁵²Eu and ¹⁵⁴Eu to an absolute accuracy of -10%. The measured europium radioisotope and ^I53Gd concentrations were within 20% of calculated values. The hydride assembly performed well and is an excellent vehicle for many FFTF isotope production applications. The results also demonstrate the accuracy of the calculational methods developed by the Westinghouse Hanford Company for predicting isotope production rates in this type of assembly.