The irradiation induced stress relaxation of peened surfaces in 304 stainless steel was simulated using 3.2 MeV protons. The specimens employed were annealed 304 bars that had been shot-peened to produce a compressive layer on the surface. Irradiation proceeded at 288ºC to four dose levels in the range 0.1-2.0 dpa, which almost covers the range experienced by a BWR shroud over a 40 year lifetime. One set of specimens was as-peened and a second set were pre-injected with 25 appm He to assess the potential of bubble-induced acceleration of irradiation creep. Another set of specimens were thermally annealed only. Both surface and depth-dependent measurements of the internal stress were conducted using an X-ray stress analyzer. Electron microscopy was then used to study the microstructural evolution as a function of depth. The results indicated that the compressive stress state was progressively relaxed during irradiation. However, the compressive stress was maintained over the 2 dpa lifetime with no indication of a possible reversal of stress state at the surface. Helium addition did not significantly affect the relaxation and no significant bubble formation was observed.
Revised: November 10, 2005 |
Published: August 1, 2004
Citation
Yuya H., Y. Isobe, G.S. Was, and F.A. Garner. 2004.Proton-induced Relaxation of Surface Stresses Resulting from Peening of Welds in Annealed 304 Stainless Steels. In 11th International Conference on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors, 121. La Grange Park, Illinois:American Nuclear Society. PNWD-SA-6042.