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Nuclear Criticality Safety
NCSD provides communication among nuclear criticality safety professionals through the development of standards, the evolution of training methods and materials, the presentation of technical data and procedures, and the creation of specialty publications. In these ways, the division furthers the exchange of technical information on nuclear criticality safety with the ultimate goal of promoting the safe handling of fissionable materials outside reactors.
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2025 ANS Annual Conference
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Chicago, IL|Chicago Marriott Downtown
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Nuclear fuel cycle reimagined: Powering the next frontiers from nuclear waste
In the fall of 2023, a small Zeno Power team accomplished a major feat: they demonstrated the first strontium-90 heat source in decades—and the first-ever by a commercial company.
Zeno Power worked with Pacific Northwest National Laboratory to fabricate and validate this Z1 heat source design at the lab’s Radiochemical Processing Laboratory. The Z1 demonstration heralded renewed interest in developing radioisotope power system (RPS) technology. In early 2025, the heat source was disassembled, and the Sr-90 was returned to the U.S. Department of Energy for continued use.
C. M. Cooling, M. M. R. Williams, E. T. Nygaard, M. D. Eaton
Nuclear Science and Engineering | Volume 177 | Number 3 | July 2014 | Pages 233-259
Technical Paper | doi.org/10.13182/NSE13-55
Articles are hosted by Taylor and Francis Online.
Previously, a point kinetics model of the Medical Isotope Production Reactor has been presented, which included representations of instantaneous power, delayed neutron precursors, fuel solution temperature, radiolytic gas content, and coolant temperature. This model has been extended to include the effects of a vertically discretized temperature profile with a mixing of heat energy by eddies, boiling, and condensation and an extended model of bubble velocity and radius. It is found that the most striking change to the behavior of the system is caused by the effects of steam, which provides a strong negative feedback that tends to depress average powers in cases where the fuel solution temperature rises above the saturation temperature but can also lead to large, sharp power peaks through steam exiting the system (which can remove a large amount of negative reactivity in a short amount of time). The overall effect, however, does not lead to any unbounded power excursions. Possibilities for further extension of the model include the modeling of the composition of the plenum gas and the modeling of global pressure and its effects.