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2025 ANS Winter Conference & Expo
November 9–12, 2025
Washington, DC|Washington Hilton
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Researchers use one-of-a-kind expertise and capabilities to test fuels of tomorrow
At the Idaho National Laboratory Hot Fuel Examination Facility, containment box operator Jake Maupin moves a manipulator arm into position around a pencil-thin nuclear fuel rod. He is preparing for a procedure that he and his colleagues have practiced repeatedly in anticipation of this moment in the hot cell.
Christofer E. Whiting
Nuclear Technology | Volume 207 | Number 6 | June 2021 | Pages 782-789
Technical Paper | doi.org/10.1080/00295450.2020.1831874
Articles are hosted by Taylor and Francis Online.
Performance predictions for the first multi-mission radioisotope thermoelectric generator (MMRTG) flight unit and engineering unit were recently reported. Both units were produced and operated/tested within specifications [i.e., nominal thermal inventory = 2000 W(thermal)]. In an attempt to study the effect of a deep space cruise on an MMRTG that has been operational for 6.25 years (2.25 years storage + 4 years cruise), the qualification unit (QU) was placed on life test with a below-specification thermal inventory of 1904 W(thermal). Analysis indicates that loading an MMRTG with a lower thermal inventory may result in less power at the beginning-of-life but more power at the end-of-design-life (EODL). The lower thermal inventory in the QU produces a lower operating temperature, which appears to cause a significant reduction in the degradation rate of the thermoelectric couples. Preliminary calculations indicate that a thermal inventory of 1904 W(thermal) could result in a 9 W(electric) power boost at EODL [i.e., 84 W(electric)], which is a 12% improvement over the first MMRTG flight unit and engineering unit predictions. Preliminary degradation analysis suggests that a 1904 W(thermal) unit will begin to produce more power than a 2027 W(thermal) unit approximately 4 years after fueling. This suggests that missions with a primary power requirement more than 4 years after fueling would benefit from a lower thermal inventory. In addition, using a lower thermal inventory has significant benefits for 238Pu stockpile management and may allow for additional MMRTGs to be fueled from our current reserves. Conclusions and hypotheses presented here should be considered preliminary because the QU data set is very small and there are some uncertainties regarding how early-life QU data will translate into later-life performance. More QU testing at a thermal inventory of 1904 W(thermal) is needed to prove that the preliminary conclusions presented here are valid.