Modelling of Cherenkov light emission from BWR nuclear fuel with missing or substituted rods

Computer simulations of Cherenkov glow from spent nuclear fuel were carried out. Spent nuclear fuel in storage ponds are verified with the help of the Cherenkov viewing device (CVD) and the Digital Cherenkov viewing device (DCVD). The instruments image the Cherenkov glow generated by gamma ray emissions from spent fuel into the water. An attempt to build a realistic digital model of the DCVD image containing partial-length, missing, and substituted rods was made to see if the effects of the deviations from normal can be predicted. It was concluded that partial-length or missing rods in the model was in good agreement with measured data, but replaced rods in the model showed a weaker attenuation of the Cherenkov glow than the observed DCVD images. (author)