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How robust is HALEU from a nonproliferation perspective?
Shikha Prasad
High-assay low-enriched uranium (HALEU) has emerged as a popular fuel choice for advanced small modular reactors due to its long power production periods before refueling. It is currently being pursued by TerraPower, X-energy, BWX Technologies, Kairos, Oklo, and other reactor companies. HALEU has a uranium-235 enrichment ranging from 5 percent to 20 percent, whereas traditional LWRs use low-enriched uranium fuel enriched up to 5 percent.
HALEU will provide power for longer durations, compared with traditional LWRs. But could it also provide an opportunity for more rapid proliferation, as is speculated in a 2023 National Academy of Sciences report on advanced nuclear reactors (nap.nationalacademies.org/catalog/26630/)?
If a nuclear proliferator conspires to divert fresh nuclear fuel for weapons production when it has not been used in a reactor, the effort required in separative work units (SWUs) to enrich U-235 from 5 percent to 90 percent and that required to enrich from 20 percent to 90 percent are both very small, compared with the effort required to enrich U-235 from its natural abundance to the initial 5 percent.
Ethwart Pollmann, Joachim Schulze, Dieter Kreuter
Nuclear Technology | Volume 108 | Number 3 | December 1994 | Pages 350-360
Technical Paper | Nuclear Reactor Safety | doi.org/10.13182/NT94-A35017
Articles are hosted by Taylor and Francis Online.
In a boiling water reactor, nuclear-thermal-hydraulic instabilities can occur if extreme operating conditions prevail. In various nuclear reactors, stability measurements have been carried out during which the location and the shape of the stability threshold was measured at a certain exposure point during the cycle. Earlier sensitivity studies have already shown that fuel assembly parameters have only a small influence on stability compared with plant parameters. The influence of plant parameters has been verified by measurements that were carried out in the German boiling water reactor Würgassen every 4 to 6 weeks during cycle 14. The results of the measurements showed for the single-loop operation point (least stable point in the core map) a strong variation of the stability threshold power during the cycle. From the beginning of cycle to the middle of cycle, the stability threshold power decreases by ∼16% (relative). After the minimum was reached, the stability threshold power increased again. Smaller variations of the stability threshold power in the core map at natural circulation indicate that not only the stability threshold varies during the cycle, but also the shape of the stability threshold is changed. Analyses with the code system STAIF have shown that the stability behavior during the cycle can clearly be correlated with the variation of the axial and radial power density profile due to control rod maneuvering and fuel burnup. Furthermore, it could be shown that for the estimation of the neutronic feedback not only the density coefficient must be taken into account but also the void variation caused by a power perturbation.