At the end of April 2015, FANC held another meeting in Brussels with the International Review Board (IRB), an international panel of experts in the effects of radiation on material properties. The experts investigated the results of the additional test campaigns conducted by Electrabel over the past year. These mechanical tests were carried out on specimens containing hydrogen flakes that had been previously irradiated in the BR2 research reactor at the SCK•CEN.
The objective of these tests was to find out the implications of long-term irradiation on the mechanical properties of this material.
During three days the international experts of the IRB reviewed and discussed the results of these tests. The IRB is now expected to issue an opinion on the methodology (e.g. calculation method) that must be used by the licensee Electrabel to write this specific chapter of its Safety Case.
Before being allowed to restart both Doel 3 and Tihange 2 reactors, Electrabel shall first submit a Safety Case to the FANC in which it convincingly demonstrates that the presence of hydrogen flakes in the walls of the reactor pressure vessel (RPV) does not compromise its structural integrity. This Safety Case must be structured around three major topics, corresponding each to a chapter of the action plan that Electrabel is due to implement:
1. The ultrasonic inspection technique of the RPVs: detection, measurement and location of hydrogen-induced flaw indications.
2. Material properties of specimens containing hydrogen flakes: radiation effects and transferability of the test results to the Doel 3 and Tihange 2 RPVs.
3. Structural integrity of a RPV containing hydrogen flakes.
The results of the actions related to theme 1 and theme 2 will provide the input for theme 3.
After completing every action related to themes 1, 2 and 3 and interpreting the results, the licensee Electrabel will submit its Safety Case to the FANC. The FANC and its technical subsidiary Bel V will thoroughly review this Safety Case using the specific expertise of the recognised inspection organisation AIB Vinçotte (for theme 1), the International Review Board (for theme 2) and an external research team (for theme 3). The FANC will collect opinions from all these parties and take them into account to decide whether Electrabel is allowed to restart the Doel 3 and Tihange 2 units. This process will take another few months.
This article is cited from the FANC website.