The X-10 Reactor at Oak Ridge was the first pilot-scale plutonium production reactor. Built in 1943 as part of the Manhattan project, it provided some of the first plutonium samples and influenced the design of the later Hanford reactors. Seven of the original fuel charges from the X-10 reactor were preserved and are currently held at Savannah River. The charges contain unique weapons-grade plutonium produced in an early production reactor. Assays were performed using two high-purity germanium (HPGe) detectors, one coaxial and the other planar. Neutron multiplicity counting was performed with an active well coincidence counter (AWCC) in the passive mode. Due to the high Cs-137 content and low plutonium content, assay times were approximately three days on each instrument. The samples were in lead and polycarbonate shielding to reduce dose to personnel. The burnup of each charge was characterized by its Cs-137 content. Eu-152 and Eu-154 were also both observed in the higher-irradiated samples. All but one of the samples showed a quadratic relationship between burnup and europium content, with the remaining sample showing a lower Eu-152 activity than expected. Pu-240 was quantified by neutron multiplicity at the milligram level, despite interferences with U-238. These results, along with any destructive analysis made in the future, can be used to benchmark burnup models of the reactor. The early reactor design is of significance when considering other reactors which may be built today by states seeking to begin nuclear weapons programs.
Year
2020
Abstract