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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
June 15–18, 2025
Chicago, IL|Chicago Marriott Downtown
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The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
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Fusion Science and Technology
Latest News
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.
Anselmo Cisneros, Nicholas Zweibaum, Christian Di Sanzo, Jeremie Cohen, Ehud Greenspan, Per Peterson, Bernhard Ludwigt
Fusion Science and Technology | Volume 61 | Number 1 | January 2012 | Pages 431-435
Other Concepts and Assessments | Proceedings of the Fifteenth International Conference on Emerging Nuclear Energy Systems | doi.org/10.13182/FST12-A13458
Articles are hosted by Taylor and Francis Online.
The proliferation resistance of the nuclear fuel cycle would be increased if one could eliminate the need for both uranium enrichment and spent fuel reprocessing. Heavy-water and graphite moderated critical reactors can extract energy from natural uranium but offer a very low uranium utilization (low discharge burnup). The objective of the present study is to explore the feasibility of achieving high fuel utilization without resorting to enrichment and reprocessing using spallation neutron source driven subcritical reactors. Three different high burnup once through subcritical nuclear systems are investigated: a fluoride salt cooled high temperature reactor (FHR) with pebble fuel, a helium cooled core with sphere pack fuel based on General Atomics' EM2 reactor concept, and a sodium cooled fast reactor that is loaded with fuel discharged from a high burnup Breed-and-Burn (B&B) fast reactor that is fed with depleted uranium, after removing the gaseous fission products and inserting the voided fuel rods into a new clad (without removing the old one).The pebble fuel design and fuel cycle for the FHR concept was optimized for maximum electric power multiplication using natural thorium fuelled subcritical core. The maximum attainable power multiplication was not high enough to merit future studies.The optimal discharge burnup of the fuel in the EM2 type subcritical core was found to be approximately 30% FIMA and the corresponding power multiplication was found higher than in the FHR but still not high enough for practical applications.Significantly better performance was obtained from the sodium-cooled source-driven core that is fed with metallic U-TRU-Zr fuel discharged at 20% FIMA from a critical B&B fast reactor that underwent recladding. The maximum attainable power multiplication was found to be close to 10 while fissioning an additional 20% of the loaded heavy metal.
