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The effects of 288°C (550°F) irradiation to 1.0 × 1019 n/cm2, E > 1 MeV, on the Charpy V-notch ductilities of two USSR-produced forging materials were determined experimentally. The materials were provided by the Kurchatov Institute under the umbrella of a joint USA-USSR agreement and represent the Cr-Mo-V forgings employed in the construction of USSR light-water VVER-440 reactor pressure vessels (RPVs) before and after 1980, respectively. The primary difference between the two materials is phosphorus content (0.019% vs. 0.007% P) consistent with their respective USSR Steel Specifications 15Kh2MFA and 15Kh2MFA-A. Specimens for post-irradiation property determinations were irradiated in the Ford Nuclear Reactor in a controlled-temperature assembly at an average fluence rate of 5.6 × 1012 n/cm2-s, E > 1 MeV. The post-irradiation Charpy V-notch 41 J (30 ft-lb) transition temperature elevation for the material representing pre-1980 RPVs was 31°C (55°F). This elevation was accompanied by a 27% reduction in Charpy V-notch upper-shelf energy level. for the material representing the post-1980 RPVs, the transition temperature elevation was ≤ 8°C (15°F); the concomitant post-irradiation reduction of upper-shelf energy was not established.
The observed transition temperature elevations are considerably less than the elevations predicted by NRC Regulatory Guide 1.99, Rev. 2. The converse is true for the reduction in upper-shelf energy level found for the pre-1980 RPV construction material. A higher fluence test is required for full qualification of the radiation resistance capabilities of the materials.
Russian steels, irradiation, transition temperature, upper-shelf energy
Consultant, Oxon Hill, MD
Staff Member, Oak Ridge National Laboratory, Oak Ridge, TN
President, ATI Consulting, Pinehurst, NC