Feasibility of Detecting Gas Leakage by Monitoring the Outer Surface Temperatures of a Horizontal SNF Canister: Numerical Simulations
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Authors
Coello Poole, Lucia
Issue Date
2023
Type
Thesis
Language
Keywords
CFD Simulation , Heat transfer , Leakage , SNF Decay heat , Storage Conditions , Temperature Monitoring
Alternative Title
Abstract
Spent nuclear fuel (SNF) will likely continue to be stored in dry storage canisters for a longer time than initially planned. Degradation mechanisms such as chloride-induced stress corrosion cracking can cause defects and cracks in the canister walls leading to the loss of the inert environment, which may increase the likelihood of internal component corrosion. One of the simplest methods to detect a leak in an SNF canister is to monitor the temperature distribution on its outer surfaces. This method has been successfully demonstrated for vertical canisters. However, it has not been extensively applied to horizontal canisters. The objective of this paper is to use computational fluid dynamics (CFD) simulations to determine if leakage of the inert gas from the 61-BT canister (and replacement by air) can be practically detected by measuring temperatures on the canister’s external surfaces. CFD simulations that model conduction, radiation, and natural convection heat transfer in the 61-BT canister inserted in a horizontal storage module are conducted. Simulations for helium and air gas backfills, pressures, seasonal and daily ambient temperatures, and SNF decay heat are conducted. The results showed that the depressurization of the inner gas from the initial pressure to the ambient value does not significantly affect the temperature distribution on the canister's outer surfaces. However, the replacement of the helium gas by air can be effectively detected by measuring the temperature difference between the side and ends of the canister’s outer surfaces. This difference changes from 20° to 8°C for a storage period from 0 to 40 years, respectively. Therefore, this method can be used for more than 40 years of storage.