Review of NDE Methods for Detection and Monitoring of Atmospheric SCC in Welded Canisters for the Storage of Used Nuclear Fuel

Abstract

Dry cask storage systems (DCSSs) for used nuclear fuel were originally envisioned for storage periods of short duration (approximately a few decades). However, uncertainty challenges the opening of a permanent repository for used nuclear fuel, implying that used nuclear fuel will need to remain in dry storage for much longer durations than originally envisioned. Thus, aging degradation of DCSSs becomes an issue that may not have been sufficiently considered in the design phase and that can challenge the efficacy of very long-term storage of used nuclear fuel.

NDE to Manage Atmospheric SCC in Canisters for Dry Storage of Spent Fuel: An Assessment

“…A recent report reviewed several NDE methods for application to DCSS canisters (Meyer et al 2013). The report considered methods based on their use in the nuclear power industry and perceived potential for inspecting and monitoring DCSS canisters.…”

“…Other groups engaged in research efforts to better understand the potential for atmospheric SCC in DCSS canisters and methods for detection include the Japanese Central Research Institute of the Electric Power Industry (CRIEPI) and the Electric Power Research Institute (EPRI) in the United States. Meyer et al (2013) noted that visual techniques may not reliably detect atmospheric SCC flaws because many flaws may feature a crack opening displacement (COD) that is below the reliable detection thresholds of standard cameras used to perform inspections in the nuclear power industry. This work is documented in NUREG/CR-6943 (Cumblidge et al 2007).…”

“…The cameras come in a variety of technologies including charge coupled device (CCD), complementary metal-oxide-semiconductor (CMOS), Chalnicon, and charge injection device (CID). A summary of environmental specifications for cameras from several commercial vendors of radiation hardened cameras is provided in Table 5.4 (Meyer et al 2013). Temperature ratings for cameras are fairly modest with the highest temperature rating at 70°C in water and 40°C-50°C being more typical for operation in air.…”

Characterizing stress corrosion cracking in stainless steel using nonlinear resonant ultrasound spectroscopy

“…Damage, specifically the development of cracking, on these casks may eventually lead to containment breaches, causing a public health hazard, therefore damage needs to be characterized. 1 One of the main types of damage possible in the steel used for nuclear storage casks is Stress Corrosion Cracking (SCC). SCC occurs when a stress is applied to a metal, including residual stresses that arise in welding, and the metal is in a corrosive environment (including airborne chlorides).…”

“…SCC occurs when a stress is applied to a metal, including residual stresses that arise in welding, and the metal is in a corrosive environment (including airborne chlorides). 1 On the microscopic scale the metal and the corrosive environment result in an electrochemical reaction. Over time, this reaction will crack the metal.…”