Innovative burnable absorbers: Assessing PaO2 and NpO2 coatings for improved safety in (Th-233U-235U)O2 fuel assemblies

• Published in: Nuclear engineering and design Vol. 421; p. 113086
• Main Authors: Kabach, Ouadie, Mahjoub Chakir, El, Amsil, Hamid
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.05.2024
• Subjects: WABA; LWR; LRM; PWR; UC; ATF; FTC; BOC; BSG; EOC; UN; SMR; FA; MTC; IFBA; BA
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2024.113086

•Introducing PaO2 and NpO2 as novel burnable absorbers in (Th-233U-235U)O2 fuel assemblies for pressurized water reactors.•PaO2 and NpO2 showcased potential as novel burnable absorbers, reducing initial reactivity excess in (Th-233U−235U)O2 fuel assemblies.•Efficient transmutation of Pa-231 and Np-237 to fissile isotopes.•Introducing PaO2 and NpO2 positively enchance fuel and moderator temperature coefficients, enhancing overall safety. Various advanced fuels and burnable absorbers (BAs) have been proposed to improve the cycle burnup of a pressurized water reactor (PWR) fuel assembly (FA). This study looks into the impact of an innovative fuel known as (Th-233U-235U)O2 with a novel neutron absorber with double coatings of PaO2 and NpO2. The study focuses on adding the proposed two-layer absorbers in some (Th-233U-235U)O2 fuel in an AP1000 assembly. Neutronic parameters such as burnup behavior, discharge burnup, and cycle length are calculated. The evolution of fuel composition in terms of actinides and fission products, as well as the variation in radioactivity with burnup, is investigated and compared to all-UO2 assembly as well as a UO2 assembly with 28 IFBA fuel rods containing 2 wt% Gd2O3. Additionally, primary safety parameters such as the fuel temperature coefficient (FTC) and moderator temperature coefficient (MTC) are evaluated to determine the effectiveness of the proposed BAs in improving the drawbacks of (Th-233U-235U)O2 fuel, particularly MTC. The results are promising, with higher discharge burnups with increased Pa-231 and Np-237 transmutation for the most proposed designs compared to all-UO2 assembly. The recommended BAs also help to reduce reactivity swings. Furthermore, coatings with (Th-233U-235U)O2 PaO2 and NpO2 produce more negative values for FTC and MTC, implying better controllability.