SPENT FUEL INSPECTION DEVICE

摘要

PROBLEM TO BE SOLVED: To raise detection sensitivity of gamma ray emitted by radioactive gas such as Kr-85 and improve quantification accuracy by suppressing the incidence into a detector, of background gamma ray such as scattered gamma ray to be a disturbance of measurement. SOLUTION: A spent fuel storage vessel 1 storing spent fuel, an inspection shield body 2 covering the spent fuel storage vessel and a gamma ray detector are provided. The gamma ray radiated out of the radioactive gas to a measurement space set near the fuel in the spent fuel storage vessel is measured with the gamma ray detector through a collimator built in the shield body. In a position in the measurement space 8 excluding the region that the collimator 10 views, a gamma ray shield member 14 is provided. Nearby the wall of the spent fuel storage vessel in the region the collimator 10 views, magnetic field devices 16 and 17 for a positron reflection are placed so that the magnetic field is arranged vertical to the collimator direction.