Cerenkov glow observations from spent fuel

The observation of Cerenkov glow from a fuel assembly is an attractive method of detecting the presence of radioactive material. The simple, hand-held instrumentation is very easy to use and does not require penetration of the water in the spent fuel pool. An obstacle to routine use of the instrument arises in that the standard night vision devices have a broad band wavelength response which required the pool area to be darkened. Various techniques used to limit the bandwidth of the devices for use in viewing the Cerenkov glow in the presence of facility illumination have furthered implementation. A properly specified, commercially available instrument has been used to make narrow band observations at two power reactors without interference from the facility illumination. Problems of interpretation of the observations persist. The technique has no useful role to play in the verification of an assembly at the rod level. As an item, the assembly can be verified as containing radioactive material in many instances; however some ambiguous situations were encountered