Irradiation-induced embrittlement of a 2.25Cr1Mo steel (original) (raw)
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Assessment of irradiation embrittlement of the Eurofer97 steel after 590MeV proton irradiation
Journal of Nuclear Materials, 2009
The irradiation hardening of the Eurofer97 steel following 590 MeV proton irradiations was determined at three different irradiation temperatures, 50°C, 250°C and 350°C, and various doses up to about 1.3 displacement per atom. The dose and temperature dependence of the irradiation hardening was characterized by a linear relationship between the irradiation hardening and the square root of the dose as: Dr 0.2 = k(T) dpa 1/2. Mini pre-cracked bend bar (1 Â 1 Â 16 mm 3) were also tested in the lower ductile to brittle transition region before and after irradiation at 300°C and 0.5 dpa. The effective fracture toughness-temperature curves, K e (T), were indexed on an absolute temperature scale at T 0 for K e = 100 MPa m 1/2 for both the unirradiated and irradiated condition. The irradiation-induced temperature shift DT 0 of the K e (T) curves yielded a coefficient C 0 , defined as C 0 = DT 0 /Dr 0.2 , of about 0.53. For these low doses, helium effects could not be identified on the fracture properties.
Embrittlement of CrMo steels after low fluence irradiation in HFIR
Journal of Nuclear Materials, 1995
Subsize Charpy impact specimens of 9Cr-IMoVNb (modified 9Cr-lMo) and 12Cr-lMoVW (Sandvik HT9) steels and 12Cr-MoVW with 2% Ni (12Cr-IMoVW-2Ni) were irradiated in the High Flux Isotope Reactor (HFIR) at 300 and 400°C to damage levels up to 2.5 dpa. The objective was to study the effect of the simultaneous formation of displacement damage and transmutation helium on impact toughness. Displacement damage was produced by fast neutrons, and helium was formed by the reaction of 58Ni with thermal neutrons in the mixed-neutron spectrum of HFIR. Despite the low fluence relative to previous irradiations of these steels, significant increases in the ductile-brittle transition temperature (DBTT) occurred. The 12Cr-IMoVW-2Ni steel irradiated at 400°C had the largest increase in DBTF and displayed indications of intergranular fracture. A mechanism is proposed to explain how helium can affect the fracture behavior of this latter steel in the present tests, and how it affected all three steels in previous experiments, where the steels were irradiated to higher fluences.
Irradiation Embrittlement of WWER RPV Steels Irradiated at High Fluences
Journal of Nuclear Technology in Applied Science
A statistical analysis of data obtained during impact testing of surveillance specimen of 15 WWER-440 RPVs operating in Russia, Ukraine, Armenia, Hungary, the Czech Republic and Slovakia was performed. The raw data used were selected from the IAEA Interanational Database. As a result of the analysis, the influence of P and Cu to T k increase was observed at a fluence up to 5 x 10 20 cm-2 (E > 0.5 MeV), more than double design end of life WWER-440 fluence value. A proposal to increase the application range of normative detpendences ΔT k (F) on reactor pressure vessel from 3 x 10 20 cm-2 to 5 x 10 20 cm-2 has been prepared to amend the regulatory and technical documents regarding the adjustment of the residual life of WWER-440 RPVs. It will allow the WWER-440 RPV to be operated for 60-80 years without annealing the base metal and in some cases without annealing the irradiated welds.
A New Approach for Evaluating Radiation Embrittlement of Reactor Pressure Vessel Steels
A new approach is developed to predict the radiation embrittlement of reactor pressure vessel steels. The Charpy transition temperature shift data contained in the Power Reactor Embrittlement Database is used in this study. The results indicate that this new embrittlement predictor achieved about 67.3% and 52.4% reductions respectively, in the uncertainties for General Electric (GE) Boiling Water Reactor plate and weld data compared to Regulatory Guide 1.99, Rev. 2 (RG1.99/R2). The implications of irradiation temperature effects for the development of radiation embrittlement models are then discussed. A new approach for the Charpy trend curve is also developed, which incorporates the chemical compositions into the governing fitting equation. This approach reduces the uncertainty of Charpy data fitting and provides an expedient scheme to link and project the surveillance test results to those for reactor pressure vessel steels.
Tensile properties of 9Cr-1MoVNb and 12Cr-1MoVW steels irradiated to 23 dpa at 390 to 550 ° C
Journal of Nuclear Materials, 1991
Normalized-and-tempered 9Cr-1MoVNb and 12Cr-1MoVW steels were irradiated in the Experimental Breeder Reactor II (EBR-II) at 390,450,500, and 550°C to displacement damage levels of up to 23 to 25 dpa. Tensile tests were conducted at the irradiation temperatures on three types of specimens: irradiated specimens, normalized-and-tempered specimens, and specimens thermally aged 5000 h at the irradiation temperatures. Observations from these tests were compared with results on these same materials irradiated in EBR-II at the same temperatures to 9 to 13 dpa.
Journal of Nuclear Materials, 2000
Miniature tensile and Charpy specimens of four ferritic/martensitic steels were irradiated at 300°C and 400°C in the high¯ux isotope reactor (HFIR) to a maximum dose of %12 dpa. The steels were standard F82H (F82H-Std), a modi®ed F82H (F82H-Mod), ORNL 9Cr±2WVTa, and 9Cr±2WVTa±2Ni, the 9Cr±2WVTa containing 2% Ni to produce helium by (n,a) reactions with thermal neutrons. More helium was produced in the F82H-Std than the F82H-Mod because of the presence of boron. Irradiation embrittlement in the form of an increase in the ductile±brittle transition temperature (DDBTT) and a decrease in the upper-shelf energy (USE) occurred for all the steels. The two F82H steels had similar DDBTTs after irradiation at 300°C, but after irradiation at 400°C, the DDBTT for F82H-Std was less than for F82H-Mod. Under these irradiation conditions, little eect of the extra helium in the F82H-Std could be discerned. Less embrittlement was observed for 9Cr±2WVTa steel irradiated at 400°C than for the two F82H steels. The 9Cr±2WVTa±2Ni steel with %115 appm He had a larger DDBTT than the 9Cr±2WVTa with %5 appm He, indicating a possible helium eect.
An evaluation of low temperature radiation embrittlement mechanisms in ferritic alloys
Journal of Nuclear Materials, 1994
Investigations underway at Oak Ridge National Laboratory (ORNL) into reasons for the accelerated embrittlement of surveillance specimens of ferritic steels irradiated at 50°C at the High Flux Isotope Reactor (HFIR) pressure vessel are described. Originally, the major suspects for the precocious embrittlement were a highly thermahzed neutron spectrum, a low displacement rate, and the impurities boron and copper. Each of these possibilities has been eliminated. A dosimetry experiment made at one of the major surveillance sites shows that the spectrum at that site is not thermalized. A new model of matrix hardening due to point defect clusters indicates little effect of displacement rate at low irradiation temperature. Boron levels are measured at 1 wppm or less, which is inadequate for embrittlement. Copper and nickel impurities are shown to promote radiation strengthening at high doses but not at the low doses pertinent to the surveillance data. It is shown that a copper embrittlement scenario has other drawbacks, and it is argued that copper impurity is not responsible for the accelerated embrittlement of the HFIR surveillance specimens. The dosimetry experiment revealed unexpectedly high levels of reaction products in some of the fast flux monitors, which are found to be caused by an exceptionally high ratio of gamma ray flux to fast neutron flux at the pressure vessel. Gamma rays can also induce atomic displacements, leading to the suggestion that the accelerated embrittlement may be provoked by gamma irradiation.
Irradiation-Induced Embrittlement in Stainless Steel at Elevated Temperature
1968
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Journal of Nuclear Materials, 2000
The objective of this work is to examine the susceptibility to hardening and embrittlement of Fe7.5/11CrWTaV reduced-activation (RA) and conventional 9/12Cr±Mo martensitic steels as a function of¯uence up to 10 dpa and irradiation temperature in the range of 250±450°C. For this purpose, materials were irradiated in the Osiris Reactor (Saclay) at 325°C for various doses ranging from 0.8 dpa to a maximum dose of 8±9 dpa. Available data concern the evolution of tensile properties for doses from 0.8 to 3.4 dpa. On the other hand, RA-steels were irradiated as Charpy V and tensile specimens in the high¯ux reactor (HFR) at Petten at temperatures ranging from 250°C to 450°C with a dose of about 2.4 dpa. Ó