Cerenkov Light Images of Irradiated Fuel and Non-fuel Assemblies from the WWER Reactor in Loviisa, Finland

Tests were performed at a water-water energy reactor (WWER) in Loviisa, Finland to study the Cerenkov images of spent fuel assemblies, irradiated non-fuel assemblies and an unirradiated skeleton assembly. The spent fuel examined ranged in burnup from 20 000 to 35 000 MWd/t U and had cooling times from 0.5 to 7 years. The tests were documented photographically using a camera attached to a Cerenkov Viewing Device (CVD). In addition to using the standard ultraviolet transmitting 105-mm lens, a longer 350-mm lens was used on the CVD to determine whether any additional information could be obtained. The photographic results of these tests are given and the observation and interpretation of the fuel and non-fuel assemblies are discussed.