Investigation of a fast partial defect detection method for safeguarding PWR spent fuel assemblies

Abstract

As the number of countries with their spent fuel inventory in storage increases, spent fuel verification for nuclear safeguards becomes important. In particular, detection of partial defect, which is the result of local diversion of fuel rods, deserves special attention. This is because accumulation of small scale fuel rod diversions could lead to undesirable consequences. While the necessary detection technologies are available, the cost and detection time associated make it difficult for the partial defect detection technologies to be applied to all spent fuel assemblies. This research investigated the feasibility of developing an efficient and cost-effective method for detecting partial defects of spent fuel assemblies. The approach is based on using the gamma radiation emitted from spent fuel and converting its energy to electric energy. Such approach was incorporated into a new detector concept called, “scintillator based partial defect detector (SPDD)”. SPDD detects the intensity of passive gamma by converting gamma radiation into photons using a CdWO4 scintillator and then into electric current by using amorphous silicon photodiode. Along with the use of detector measurements, a parallel approach of estimating generated electric current by using computation models using the declared spent fuel information is implemented. Detection of partial defects is based on comparing the differences in the electric current between measurements and the expected results. The proposed method was tested using the scenario of detecting 1 SQ (significant quantity) of Pu missing among spent fuel assemblies loaded for a shipment in a typical transportation cask. Results from selected test cases indicated the feasibility of as well as limitations in detecting partial defects by using the proposed method for screening purposes. The irradiation damage to the CdWO4 scintillator of SPDD was also examined for the periods of in-reactor application. In addition, the cost associated with SPDD was estimated in comparison to that of existing partial defect technologies. Purpose of the researchTo design a cost-effective partial defect detector with fast screening capability. To demonstrate the feasibility of applying the detector in high radiation environment. To setup partial defect detection criterion. To examine the feasibility of applying the developed detector to partial defect detection. ApproachesDesign a scintillator – photodiode based gamma detector. Develop a method for detecting partial defects. Setup detection criterion for partial defect detection. Analyze radiation damage issue and cost – effectiveness of the proposed detection method. Demonstrate the feasibility of partial defect detection base on examining test case assemblies.