Partial defect verification of spent VVER fuel using the DCVD

Volume: 68, December 2026, pages 56 - 61

Authors:  Erik Branger ^a, Sophie Grape ^a, Vaibhav Mishra ^a
aUppsala University, Department of Physics and Astronomy, Division of Applied Nuclear Physics. Ångströmlaboratoriet, Lägerhyddsvägen 1, Box 516, 751 20 Uppsala.
 

Abstract: The Digital Cherenkov Viewing Device (DCVD) is a non-destructive assay instrument used by the International Atomic Energy Agency to verify spent nuclear fuel, capable of performing partial defect verification on the 50% removal level. It has extensively been used on boiling water reactor fuels and pressurized water reactor fuels, but so-far its performance for VVER fuels has not been investigated.
In this work, simulations of VVER-440 assemblies were run for three different partial defect cases where 50% of the rods were either removed or substituted with low, medium or high-density dummy rods. Each substitution was done for three different substitution patterns. The Cherenkov light production and transport to a detector location was simulated, taking into account a representative axial burnup profile and the top structure of the assemblies. The region of interest (ROI), representing the region in which the Cherenkov light intensity is evaluated, was updated to be hexagonal.
The simulation results indicate that detecting partial defects in a VVER assembly is more challenging than in BWR or PWR assemblies. This is due to a combination of the top structure that covers more of the assembly as compared to the PWR and BWR cases, and the hexagonal geometry of the fuel assembly, resulting in the Cherenkov in the ROI being less affected by substitutions near the periphery. Hence, the current partial defect detection methodology is not immediately applicable to VVER-440 fuels, and additional development is required before the DCVD can be used also to reliably verify these assemblies.
 

Keywords:
Nuclear fuel, partial defect verification, Cherenkov light, DCVD, NDA, VVER.

Reference guideline: Branger, E., Grape, S., Mishra, V., (2026). Partial defect verification of spent VVER fuel using the
DCVD, ESARDA Bulletin - The International Journal of Nuclear Safeguards and Non-proliferation, 68,
56-61. https://doi.org /10.3011/ESARDA.IJNSNP.2026.6