An International Double-Blind, Peer-Review Journal by NSTRI

Document Type : Research paper

Authors

Nuclear Science and Technology Research Institute (NSTRI), Reactor and Nuclear Safety School

Abstract

Spent fuel assay is vitally important for spent nuclear fuel management. Spent fuels with high radiation dose levels also require an appropriate dosimeter. A wide spread detector used for nuclear radiation dosimetry, is Geiger-Muller detector. Pulses from this detector are of the same amplitude and no information about particle energy is provided. Dead time is a distorting effect as nonlinear response is observed at high counting rates which requires application of correction methods to avoid the nonlinearity. The especial measuring tool must be consistent with the structures and constrains of the spent nuclear fuels, the spent fuel storage, and its construction design in TRR. Spent nuclear fuel assemblies are kept in 10-meter water in depth in the open reactor pool for a specific cooling period of time before transportation to the spent fuel storage pool. The high dose rate measurement requires its specific measuring equipment. In this work, a spent fuel active dosimeter is developed for spent fuel assay in TRR. Due to high radiation exposure, parts of the equipment are specially designed to be resistive against gamma radiation. To eliminate pulse pile-up effect as well as noise cancellation, a band pass filter is employed. Time interval distribution (TID) method is also devised as an advanced technique by incorporating its related digital electronics circuitry. By utilizing a Co-60 standard gamma source in Karaj Secondary Standard Dosimetry Laboratory (SSDL), the tests and calibration of the detector are also accomplished. Validation of the system is performed with a commercial measuring tool

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