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

Abstract

In this effort, an assessment of bulk ultrasonic (UT) and eddy current (ECT) methods and techniques is performed for inspecting the surfaces of dry cask storage systems (DCSSs) canisters. Some DCSS canisters (especially those located in coastal environments) will be exposed to environmental conditions, which can cause atmospheric stress corrosion cracking (SCC). Information collected from the field and from laboratory studies has not been able to rule out the possibility of atmospheric SCC in DCSS canisters, although no occurrences of atmospheric SCC in DCSS canisters have been detected. UT and ECT methods and techniques are already used to inspect nuclear power plant components and this experience, along with their relative maturity, makes these methods and techniques likely frontrunners for near-term application to examination of dry storage canister surfaces. In this report, the results of several performance reliability studies for UT and ECT are reviewed. The detection, depth-sizing, and lengthsizing results are documented and summarized to quantitatively estimate the adequacy of UT and ECT for inspecting dry storage canister surfaces. In addition, this effort focuses on the implementation of NDE methods and techniques in the Holtec HI-STORM 100 system and the Transnuclear NUHOMS horizontal storage modules and considers environmental compatibility, accessibility constraints, and NDE sensor deployment options for these systems.v

Effects of Relative Humidity on Crevice Corrosion Behavior of 304L Stainless-Steel Nuclear Material in a Chloride Environment

“…In the HI-STORM system, crevice conditions occur where the multipurpose canister bottom plate contacts the pedestal. In the NUHOMS system, crevice conditions occur where the dry shielded canister contacts the support rails [2].…”

Electromagnetic Acoustic Transducers for Robotic Nondestructive Inspection in Harsh Environments

“…There are many cases where nondestructive inspection (NDI) of structures, such as pipelines and containers, needs to occur in harsh environments, including elevated temperature and radioactivity in the nuclear power industry. An excellent example considered in this research is dry storage casks for spent nuclear fuel, shown in Figure 1 a [ 1 , 2 , 3 , 4 , 5 ]. The dry storage cask consists of a welded austenitic stainless steel cylindrical canister that confines spent nuclear fuel and a concrete/steel overpack that shields and protects the canister.…”

“…The canister is roughly 2 m in diameter and 5 m long [ 5 ]. Chloride-induced stress corrosion cracking (SCC) in the heat affected zone (HAZ) of full penetration welds in the canister is a potential aging mechanism of the canister [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ], which should be inspected for in order to ensure the continued health and performance of the dry storage cask. However, the environment in the plenum between the canister and the overpack has both elevated temperature and gamma radiation that both gradually decrease over time in storage.…”

“…However, the environment in the plenum between the canister and the overpack has both elevated temperature and gamma radiation that both gradually decrease over time in storage. Given the dynamic nature of the thermal and radiation fields predicted by numerical simulations, the robotic inspection system design criteria were conservatively selected to be 177 °C (350 °F) and 27 krad/h, respectively [ 1 , 5 ]. The harsh environment requires that the materials used in the sensors to detect SCC be carefully selected to maintain functionality throughout the inspections.…”

Remote detection of stress corrosion cracking: Surface composition and crack detection

“…Issues related to nondestructive evaluation of dry storage casks for spent nuclear fuel have been described elsewhere by the authors [1] and in numerous reports [e.g., [2][3][4][5]. Spent nuclear fuel goes to wet storage and then dry storage prior to disposal.…”