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

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Steel 1. The hydrogen contents of the pressure vessel steel after irradiation (inert helium atmosphere) (Brinkman and Beeston, 1970).

Approximate

Average hydrogen

Number of Standard

fluence

specimens

deviation

n/cm 2 , E > l MeV

content, ppm

analysed

Unirradiated

0 to 0.2

-

-

7 x 10' 8 2 x 10 20 4 x 10 20

0.9 1.7 2.1

7

0.3 0.8 1.3

26

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Koutsky and Splichal (1986) have reported that Russian VVER 440 CrMoV steel has in its initial state 0.4-0.6 ppm hydrogen; after irradiation (inert helium atmosphere, 2.6-4.9 x 10 23 n/m 2 , E > 0.5 MeV), the hydrogen content rises to 1.2-2.0 ppm. They also observed that the irradiation temperature played a major role; the hydrogen content grew one and half times due to the irradiation at a temperature of 290°C and three to four times due to the irradiation at a temperature of 130°C. When the stainless steel cladding material was irradiated in PWR water for a prolonged period, the hydrogen contents of the specimens turned out to be 3-4 ppm after the irradiation. If it is assumed that the hydrogen content of the cladding is at equilibrium with the base material below the cladding/base material boundary in long-term operation, the hydrogen content of the base material may reach values that are significant for the embrittlement of hydrogen at different stages of operation. Ruscak et al. (1991) have suggested that the heat-affected zone of the weldment of the CrMoV pressure vessel steel contains hydrogen levels of 1.9-2.3 ppm after welding and, correspondingly, the hydrogen content of the heat-affected zone of the CrNiMoV steel is 2.1-3.9 ppm of hydrogen after welding; the hydrogen contents of the base metal would thus reach hydrogen levels of 0.2-0.4 and 0.4-0.8 ppm. After the post-weld anneals, the hydrogen contents of the heat-affected zones are in the range of 0.6-1.6 ppm. The high hydrogen contents are due to the efficient hydrogen traps of the microstructures. It is presumable that even in the irradiated state the hydrogen contents of the heat-affected zones are highest of all. Mazel et al. (1978) measured 0.3-0.7 cm 3 H/100 g Fe in the post-weld