The cask radiation profiling system (CRPS) is used to re-verify the presence of spent fuel in a dry storage cask following a break in the continuity of knowledge (i.e. a gap in surveillance and seals). The system uses a CdZnTe probe to perform a spectroscopic scan of the cask contents. The scan, better known as a radiation profile or fingerprint, is performed using a verification tube which runs inside the cask and parallel to the spent fuel contents. The fingerprint is acquired by raising the detector probe up the verification tube using a speed controlled motor to monitor the detector position. To re-verify the cask contents, the fingerprint is compared with a baseline fingerprint. Consistency between the fingerprints indicates that the spent fuel remains present and undisturbed. A database has been developed for storage and evaluation of fingerprints to secure and compare fingerprints while taking into account decay and differences in the measurement hardware configuration. The CRPS can be run with a pair of detectors to perform neutron (fission chamber) and γ profiling.

(Source: IAEA Safeguards Techniques and Equipment)