Thermoelectric pProperties of hHigh-pPerformance n-tType lLead tTelluride mMeasured iInsSitu in a nNuclear rReactor cCore

Thermoelectric generators are promising energy sources in remote or harsh environments such as the core of a nuclear reactor where they can power remote sensors and other in-core instrumentation. A high-performance n-type lead telluride material Pb_0.975Ga_0.025Te-0.25% ZnTe was inserted into the core of a nuclear reactor and thermoelectric material properties were continuously monitored while it was irradiated for 228 MW-days to a fast neutron (>1.0 MeV) fluence of 2.0 × ×10²⁰ n/cm⁻². The electrical conductivity increased within hours of the reactor starting with a peak increase to 343% of the non-irradiated electrical conductivity at the same temperatures. The electrical conductivity subsequently decreased but leveled off at 155-161% of the non-irradiated value near the end of the reactor cycle. The thermoelectric power factor and device power density peaked at 132% of the non-irradiated values within the first few days but fell to 90% of the non-irradiated values around day 9 due to a moderate drop in Seebeck coefficient to 57% of the non-irradiated value. Beyond day 9, the Seebeck coefficient steadily increased until leveling off at 81-85% of its non-irradiated value near the end of the cycle. After the initial transient changes in Seebeck coefficient and electrical conductivity, the power factor of the material in-core was approximately the same as the measured value before irradiation. However, due to a sudden increase in Seebeck coefficient and electrical conductivity during the last few days, the power factor at the end of the reactor cycle was 8-10% greater than the power factor of the non-irradiated material at the same temperatures. These results indicate that the PbTe based thermoelectric material studied in this work can serve as a solid-state power source for operation in the harsh environment of a nuclear reactor core.