In selecting the materials for the Canadian SCWR, it is important to consider the effects and extent of stress corrosion cracking under various operational conditions. Several methods of stressing a corroding material are available and each have their perceived benefits and drawbacks; for simplicity of the experimental set-up, at UNB a constant load C-ring assembly has been used with Inconel 718 Belleville washers acting as a spring to deliver a near-constant load to the sample. To predict the stress at the apex of the C-ring, a mechanistic model has been developed to determine the force applied by the spring due to the thermal expansion of each component constrained within a fixed length. In an attempt to validate the mechanistic model, trials to measure the force applied by the washers as they thermally expanded were performed using an Instron machine and an environmental chamber. Accounting for the thermal expansion of the pull rods, the force was measured as temperature was increased while maintaining a constant displacement between the platens holding the C-ring. Results showed the initial model to be insufficient, as it could not predict the force measured through this simple experiment. The revised model presented here considers the thermal expansion of the C-ring and all the components of the testing apparatus including the tree, backing washers and Belleville washers. Further validation using the finite element code ABAQUS is presented, as are preliminary results from the use of the apparatus to study the SCC of a zirconium-modified 310s SS exposed to supercritical water.