Doel 3 & Tihange 2 - Some Peer-reviewed Scientific Papers & Reports

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In summary, American studies on the interactions of hydrogen and irradiation embrittlement are very limited and they have focused mostly on low-strength steels, which do not present major problems. In light of the results, it was concluded that hydrogen embrittlement and the increase of irradiation embrittlement under the influence of hydrogen are not a significant problem that would limit reactor safety. In addition, it was deemed that hydrogen contents of over 2 ppm are not generated in clad pressure vessels.

3.2 JAPANESE STUDIES

Takaku et al. (1978a, 1978b, 1982) have studied the hydrogen embrittlement of pure iron and ASTM A533B and A542 steels in both irradiated and unirradiated states. With pure iron, hydrogen charging (about 2.3 ppm H 2 ) increases the ductility of the irradiated specimen, as shown in Figure 7. In a hydrogen-charged irradiated specimen, the type of fracture changes into a quasi-cleavage/ductile fracture from an intergranular cracking caused by hydrogen in unirradiated iron. This is apparently due to the traping effect of the crystallographic defects induced by irradiation. However, hydrogen significantly reduces the elongation to fracture. Figures 8 and 9 illustrate the effect of hydrogen and irradiation on the tensile strength and the elongation to fracture of A533B and A542 steels. Steel behaves like pure iron, so that hydrogen and irradiation together cause no detrimental effects. In irradiated A533B and A542 steel (2.2 and 1.6 ppm H) there was no delayed fracture at 830 h, when the stress was 82% of the tensile strength (Figure 10). The fracture surface of the delayed fracture of the A533B steel was quasi-cleavage/ductile and the fracture surface of the higher strength A542 steel was of intergranular/quasi-cleavage type.