Nuclear Energy Research Initiative (NERI): Novel Concepts for Damage-Resistant Alloys in Next Generation Nuclear Power Systems - Technical Progress Report August 2000 - October 2000

OAK-B135 This ID belongs to an IWO and is being released out of the system. The Program manager Rebecca Richardson has confirmed that all reports have been received. The objective of the proposed research is to develop the scientific basis for a new class of radiation-resistant materials. Two approaches will be evaluated to develop damage resistant materials far superior to current stainless steels: (1) lattice perturbation to catalyze defect recombination within the early stages of cascade formation and defect migration and (2) controlled manipulation of the aggregate defect ensemble through the deliberate introduction of dynamic metastable microstructures. The intrinsic ability of the host matrix to resist displacement damage survival will be optimized in first concept. This approach (Task 1) explores baseline atomic displacement and recovery processes as affected by major and minor alloy constituents selected for the dual purpose of environmental cracking resistance as well as interactions with point defects. Inert oversized solutes known to improve corrosion behavior will be used to create vacancy/interstitial traps and promote defect recombination. Dynamic metastable microstructures tailored to resist damage accumulation will be investigated and optimized in the second concept (Task 2). Unique intermetallic second phases with inherent instabilities under irradiation will be used to create a dynamic microstructure resistant to radiation hardening, swelling and embrittlement. A key aspect of designing this dynamic microstructure will be to ensure the complex, radiation-induced changes do not promote environmental cracking. The underlying radiation materials science for these two approaches is being explored using charged particle irradiations. Radiation damage resistance will be established by isolating the effect of each approach on defect microstructure, grain boundary microchemistries and matrix hardening. The dose dependence of these radiation-induced material changes will be used to identify promising alloys and initial microstructure that effectively delay or eliminate detrimental microstructural and microchemical evolution. Environmental cracking response is being established on non-irradiated alloys with thermomechanical treatments to simulate radiation microstructures and by tests on proton-irradiated specimens. The ultimate goal for these alloys will be resistance to environmental cracking, swelling and embrittlement during the high radiation exposures (>150 dpa) planned for advanced reactors