Hydrogen Crac<i>k</i>s in Belgian Nuclear Reactor Pressure Vessels: Five Years after Their Discovery – an Update

Abstract More than three years after the first detection of thousands of “hydrogen flaws” in its Reactor Pressure Vessel (RPV), the Belgian nuclear power reactors Doel 3 and Tihange 2 were restarted at the end of 2015. However – now again almost two years later – the potential problem of (hydrogen-related) cracks in the RPV and the related longer-term aging problems of the reactor are still imminent, probably more than ever. This paper briefly elaborates on some reported findings and identifies possible mechanisms and risks for further growth of these defects in the reactor pressure vessel wall. The current study shows that – despite a number of counter-arguments – there are, for instance, significant potential risks or uncertainties about process-generated hydrogen problems (e.g. originating from corrosion, radiolysis, etc). These are sufficiently grave to raise concerns about the fitness-for-service of the affected reactors, and also about similar reactors world-wide. Just one example of the latter is the finding of similar “UST-indications” in the Swiss nuclear power plants Beznau 1 (and 2). From a life-management and safety point of view, it is recommended that meticulous inspection and continuous monitoring and surveillance programs be set up and implemented when keeping these aging reactors in operation.