Irradiation creep data in support of LMFBR core design

Temperature and neutron flux gradients occurring spacially within the core of an LMFBR generate distortions through the phenomena of swelling and irradiation creep in contemporary core materials. These distortions lead to subassembly interactions both during operation of an LMFBR and during refueling, and thereby limit the life of certain components. Core design and performance analyses therefore require good descriptions of swelling and irradiation creep. Sufficient data to quantify swelling and irradiation creep are finally beginning to materialize. Stainless steel swelling data are available for neutron fluences up to 1023 n/cm2 (E>0.1 MeV). New testing techniques and analytical methods are being developed to determine the history dependence and stress-state dependence of irradiation creep at both low and high neutron fluence levels to systematically develop the rules required to describe irradiation creep under general multiaxial stress conditions. The initial high fluence results obtained from these new techniques are showing that the limited low neutron fluence, low temperature irradiation creep results available until now did not provide an adequate basis for development of equations which describe irradiation creep for the conditions existing in new experimental or commercial LMFBR systems. These new results are showing significantly more irradiation creep than predicted by extrapolation of the previously available low fluence and low temperature data