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THE EFFECT OF HYDROGEN ON DUCTILE PROPERTIES OF IRRADIATED PRESSURE VESSEL STEELS
... Particularly reactor pressure vessels (RPV) of the WWER-440/230 project were manufactured without stainless cladding that is were in contact with primary circuit water and accessible for hydrogen as a product of RPV wall corrosion. Analysis of the combined radiation-hydrogenation embrittlement of the 48TS type vessel steel was performed in [3] where at the mention of the American [4] and own data question concerning unknown source of hydrogen in metal that was irradiated in nuclear reactor in hermetic ampoules (was named as "irradiation-produced hydrogen" (IPH) was raised. Table 1 lists chemical composition of the RPV steel used (48TS type). ...
... Results of the IPH concentration in steel analysis carried out in the USA are shown in Table 2 [4]. One can see that the greater the fast neutron fluence (FNF) the greater the hydrogen content. ...
In traditional power engineering hydrogen may be one of the first primary sources of equipment damage. This problem has high actuality for both nuclear and thermonuclear power engineering. Study of radiation-hydrogen embrittlement of the steel raises the question concerning the unknown source of hydrogen in reactors. Later unexpectedly high hydrogen concentrations were detected in irradiated graphite. It is necessary to look for this source of hydrogen especially because hydrogen flakes were detected in reactor vessels of Belgian NPPs. As a possible initial hypothesis about the enigmatical source of hydrogen one can propose protons generation during beta-decay of free neutrons поскольку inasmuch as protons detected by researches at nuclear reactors as witness of beta-decay of free neutrons.
... Particularly reactor pressure vessels (RPV) of the WWER-440/230 project were manufactured without stainless cladding that is were in contact with primary circuit water and accessible for hydrogen as a product of RPV wall corrosion. Analysis of the combined radiationhydrogenation embrittlement of the 48TS type vessel steel was performed in [3] where at the mention of the American [4] and own data question concerning unknown source of hydrogen in metal that was irradiated in nuclear reactor in hermetic ampoules (was named as " irradiation-produced hydrogen " (IPH) was raised. Table 1lists chemical composition of the RPV steel used (48TS type). ...
... Determination of the hydrogen content in the irradiated steel fulfilled in the USA went to unexpected result: hydrogen content noticeably exceeded the quantity rated at (n,p) transmutation reaction: less than 0,1 ppm. Results of the IPH concentration in steel analysis carried out in the USA are shown in Table 2[4]. One can see that the greater the fast neutron fluence (FNF) the greater the hydrogen content. ...
In traditional power engineering hydrogen may be one of the first primary source of equipment damage. This problem has high actuality for both nuclear and thermonuclear power engineering. Study of radiation-hydrogen embrittlement of the steel raises the question concerning the unknown source of hydrogen in reactors. Later unexpectedly high hydrogen concentrations were detected in irradiated graphite.
It is necessary to look for this source of hydrogen especially because hydrogen flakes were detected in reactor vessels of Belgian NPPs.
As a possible initial hypothesis about the enigmatical source of hydrogen one can propose protons generation during beta-decay of free neutrons поскольку inasmuch as protons detected by researches at nuclear reactors as witness of beta-decay of free neutrons.
... Earlier investigations have shown that a H-content larger than 2.5 -4 ppm effects a clear decrease in toughness and above all causes total embrittlement for high strength steels (R m ≥ 1200 MPa) [1]. After several years of exposure in the pressurized water of the reactor near the core, these critical concentrations are not reached [2]. ...
... • 10XhMFT. 1 ...
The influence of hydrogen on the mechanical behaviour of different reactor pressure vessel (RPV) steels was investigated by tensile tests in correlation to the chemical composition, the neutron fluence, the hydrogen charging condition, the strain rate, and the temperature. Small-angle neutron scattering (SANS) experiments, hydrogen analyses and thermal desorption investigations were performed to prove the evidence of hydrogen trapping at irradiation defects. An increasing susceptibility to hydrogen embrittlement indicated by reduction of area was observed at room temperature with in situ hydrogen-charged specimens when loaded by low strain rates or with specimens which had been irradiated at low temperature. Generally, the susceptibility increases with increasing strength of the steels. At 250 °C hydrogen embrittlement was not evident. The results do neither prove that irradiation defects are favoured traps for hydrogen nor give evidence that hydrogen affects the RPV integrity under normal operating conditions.
... Pre-irradiated RPV steel samples (8.4×10 18 n/cm 2 ) exposed to HTW in a loop in the NRI test reactor at 288 °C for 332 h, showed total hydrogen concentrations Literature review 30 of 1 to 2.9 wppm (compared to 0.4 to 1 wppm in the initial condition) [68]. Un-irradiated Eastern RVP steel samples exposed to simulated PWR at 325 °C, showed a hydrogen uptake from 0.5 to 1.5 wppm (with local peaks up to 6 wppm) [69]. Irradiated RPV steels usually revealed a higher hydrogen pick-up under identical electrochemical charging conditions, due to higher trap density of dispersed defects. ...
A study of the combined effects of radiation, water and temperature on sustained load crack growth behavior of reactor pressure vessel steel A533B-1 is reported. To complete this study wedge opening loading (WOL) T-type fracture toughness specimens were prepared from a sample of A533B-1 steel which had a copper content of 0.13%. The crack length change was measured after 939 hr of irradiation in a water environment. An electrical potential method was successfully used to measure the crack length of rusted radioactive specimens. Sustained load crack growth occurred at initial stress intensity factor KIi as low as . The value of stress corrosion cracking threshold factor KIscc after neutron irradiation in a water environment appears to be in the range of . The results of neutron irradiation in a water environment are to apparently increase the susceptibility of A533B-1 steel to stress corrosion cracking and hydrogen embrittlement.
Hydrogen embrittlement of low-alloy steels has been investigated in relation to its dependence on hydrogen trapping and release, on the electrolytic hydrogen charging parameters, and on irradiation. The interaction of hydrogen with the structure of irradiated and unirradiated steels at higher charging current densities causes structural defects which can lead to a loss of ductility of the steel even after hydrogen release. The presence and the character of grain boundaries, secondary phases and other defects in the steel structure are of great importance from the viewpoint of the hydrogen embrittlement effect.
Current methods of predicting the inservice fracture toughness of nuclear reactor pressure vessels subject to irradiation embrittlement are briefly reviewed, and a new and integrated approach is proposed. This approach is based on the use of a wide variety of information, including the rapidly emerging understanding of the fundamental mechanisms of fracture in the ductile to brittle transition region as well as the microstructurally-mediated processes leading to embrittlement. However, the focus is on advanced, nonintrusive characterization methods for measuring composition, coarse and fine scale microstructure, and mechanical properties using small sample biopsies from operating vessels.
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