Impact of an apparent radiation embrittlement rate on the life expectancy of PWR vessel supports
- Oak Ridge National Laboratory, TN (United States)
Recent data from the High Flux Isotope Reactor (HFIR) vessel surveillance program indicate a substantial radiation embrittlement rate effect at low irradiation temperatures ({approximately}50{degrees}C) for A213-B, A350-LF3, A105-II, and corresponding welds. Some pressurized-water-reactor (PWR) vessel supports are fabricated of similar materials and are subjected to the same low temperatures and fast neutron fluxes (10{sup 8} to 10{sup 9} neutrons cm{sup {minus}2}s{sup {minus}1}, E>1.0 MeV) as those in the HFIR vessel. Thus the embrittlement rate of these structures may be greater than that previously anticipated. A study sponsored by the Nuclear Regulatory Commission is under way at Oak Ridge National Laboratory to determine the impact of the rate effect on PWR vessel support life expectancy. The scope includes the interpretation and application of the HFIR data, a survey of all light-water-reactor vessel support designs, and a structural and fracture-mechanics analysis of the supports for two specific PWR plants of particular interest with regard to a potential for support failure as a result of propagation of flaws. Calculations performed for one of the plants indicate a best-estimate critical flaw size of approximately 10 mm corresponding to 32 effective full-power years. Apparently low-cycle fatigue is not a viable mechanism for the creation of flaws of this size. Thus, presumably, such flaws would have to exist at the time of fabrication. 21 refs., 8 figs., 3 tabs.
- OSTI ID:
- 226666
- Journal Information:
- Nuclear Safety, Vol. 32, Issue 1; Other Information: PBD: Jan-Mar 1991
- Country of Publication:
- United States
- Language:
- English
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