Critical Reflections about Doel3 & Tihange2

Integrity reactor vessels Doel 3 and Tihange 2

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Figure 2: Components of the Doel 3 reactor pressure vessel and vessel head [ 14 ] p20.

2. The absence of a consolidated theory for material with a high density of cracks. The fracture mechanics theory mainly deals with the behaviour of a single crack under stress with- out interaction of neighbouring cracks. In recent research, the interaction between two cracks have been published in several articles, and multiple crack situations are still in the research phase. There are no precedent cases published wherein such high crack densities in construc- tions occur. Electrabel has proposed grouping rules which led to the ASME BPVC nuclear code case N-848. In this code case, flaws in close proximity to each other are grouped in rectangu- lar boxes. The circle or ellipse with the largest dimension fitting in this box is then treated as a single ”equivalent flaw”, which then will be evaluated according to the ASME BPVC criteria. No proof has been found if the ”equivalent flaw” is the worst case flaw in all possible flaw combinations in the vessel wall. It makes the nuclear reactor vessels of Doel3 and Tihange2 an experimental case for a non–consolidated fracture mechanics theory. This is discussed in more detail in section 6.

R.Boonen & J.Peirs

May 18, 2017