An In-Situ Corrosion Small Punch Test for Developing Stress Corrosion Cracking in Stainless Steel

Background
Spent AGR (advanced gas-cooled reactor) fuel cladding may suffer from stress corrosion cracking (SCC) during the interim storage period in cooling ponds and compromise the structural integrity of fuel storage.

Objective
To better understand the effect of SCC, a new small punch test (SPT) setup was developed in this study that can use a small volume of sample to limit the safety concerns about irradiated materials.

Methods
The SPT setup accelerated SCC in a surrogate material 304 stainless steel by introducing a circulation of a heated corrosive solution. Preliminary tests were performed to find the loading and environmental conditions that can develop SCC in the surrogate material. A finite element model was used to estimate the mechanical behaviour of the material during the test.

Results
Several samples were tested under different conditions, and SCC and other forms of corrosion behaviours were observed on the samples. The effects of different corrosive environments were obtained by further characterisation including scanning electron microscopy (SEM) and optical profilometry.

Conclusions
The experiment demonstrated the new setup can develop SCC from a small volume of sample in a short period of time. Several improvements are listed including extra procedures to enable the experiments on the irradiated fuel materials.