Fundamental technology to improve criticality safety of High Temperature Gas-cooled Reactor (HTGR) fuel fabrication is being developed. Fuel enrichment for commercial HTGR is 14wt% and the large part of process of the fuel fabrication is performed in an aqueous system. Therefore, it is necessary for highly enriched fuel of commercial HTGR fabrication to perform severe criticality safety measures. However, conventional criticality safety measures, geometry or mass control, require expansion of the fuel fabrication facility, and in some cases, the number of batches may increase. These also increase the capital cost of fuel fabrication. In order to suppress the increase in the cost, mixing Burnable Poison (BP) into fuel material in the first process is being considered. A previous study by our group has shown that optimizing the amount of BP added ensures criticality safety during fuel fabrication, and does not affect cycle length. Moreover, by using BP as a nitrate, there is a possibility that it can be fabricated by the sol-gel method as before.In this study, the feasibility of the BP mixed fuel fabrication by sol-gel method is examined from the fabrication process perspective. For BP, boron, gadolinium, erbium, and hafnium are candidates. Firstly, it is investigated whether or not a predetermined amount of the nitrate solution of BP is dissolved and gelled by the reaction with ammonia gas. Secondly, fabrication tests of a simulated fuel (CeO2) mixed with BP is performed. A prototype of fabricating equipment for the tests is currently under design. The simulated fuel produced by the sol-gel method is completed through a sintering process. As a result of preliminary analysis, it was found that BP exists stably as an oxide even in a high-temperature oxidizing or reducing atmosphere, and even if BP is mixed, it does not contribute to fuel failure during sintering. Therefore, when the design of the gelation reaction between the BP nitrate solution and the ammonia gas is decided, there is a high possibility that the BP mixed fuel can be fabricated by the conventional method.

Manufacturability Estimation on Burnable Poison Mixed Fuel For Improving Criticality Safety of HTGR Fuel Fabrication

Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE28/volume/85246

2021 28th International Conference on Nuclear Engineering (ICONE28)

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