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

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Koutsky et al. (1984, 1985, 1986) have researched the hydrogen embrittlement of CrMoV and CrNiMoV steels on smooth irradiated test specimens (2.6 - 4.9x 10 23 n/m 2 , E > 0.5 MeV, helium atmosphere, 130, 180 and 290°C), as shown on Tables 2 and 3. The hydrogen charging prior to the tensile test was done in 1 N H 2 SO 4 + 30 ppm As 2 O 3 solution (1 h) with different current densities. Figure 15 shows the elongation to fracture of CrMoV steel as a function of the hydrogen content of the steel and the cathodic current density. Regardless of whether it is irradiated or unirradiated, the CrMoV steel is susceptible to hydrogen embrittlement if the hydrogen content of steel exceeds 2.5 ppm. With hydrogen content of over 8-10 ppm, the irradiated steel becomes completely brittle. To determine the threshold stress of hydrogen embrittlement, statically loaded notched unirradiated test specimens were studied with hydrogen charging at different cathodic current densities. Figures 16-18 present the threshold values of the hydrogen embrittlement of the CrMoV and CrNiMoV steels: R HE of CrMoV steel is 210 MPa and that of CrNiMoV steel 410 MPa, respectively. The hydrogen contents of the CrMoV steel were between 3.5-6 ppm. In both steels, the controlling fracture mechanism was intergranular fracture. The higher resistance to the hydrogen embrittlement of the CrNiMoV steel in this study was attributed to the greater purity of the steel, which decreases the susceptibility to intergranular fracture. Koutsky and Splichal (1984, 1985, 1986) studied CrMoV steel and found its hydrogen content in an unirradiated state to be 0.4-0.6 ppm and in an irradiated state 1.2-2.0 ppm. Figures 19 and 20 present the hydrogen contents and elongations to fracture of the irradiated and unirradiated steels as a function of the charging time. A charging time of one hour was sufficient to bring the saturation hydrogen content. The hydrogen content of the irradiated specimen is greater than that of the unirradiated one so that the irradiation damage traps hydrogen more effectively than the microstructure of the unirradiated steel. Koutsky and Splichal (1986) assumed that 2 ppm of hydrogen is dissolved in steel evenly and the excess is bound to the hydrogen traps. Figure 21 presents a summary of the hydrogen content of different steels as a function of the cathodic current density of the hydrogen charging. The current density determines the hydrogen content of the steel. Even