Nuclear Science User Facilities 112 Availability of well-characterized, highly irradiated 304 stainless steel for NSUF-supported studies Frank Garner – Radiation Effects Consulting – Paula Freyer – Westinghouse – Stainless steels serve as the major structural components in both fast reactors and thermal power reactors, not only in the U.S., but in Russia, China, Japan, most European countries and other nations.There- fore, intense international interest is growing in the response of these steels to increasing radiation exposure, especially in the light-water reactor (LWR) power-generation community, where government-granted operation licenses for 30 years (Russia, Japan) or 40 years (U.S.) are approaching or exceeding these lifetime limits. Requests in the U.S. for life extension to 60 years are now being considered and, in many cases, granted, gener- ating new interest in research on radiation response of these steels. In the U.S.,Western Europe and Asia, the major construction steel employed in reactor construction was AISI 304, produced 45–60 years ago, but with then-current technology, which produced steels with less stringent specifications than currently required, especially with respect to minor deleterious elements such as sulphur and phosphorous—important in corrosion and welding—or with respect to gases such as oxygen and nitrogen, which are important initia- tors of void swelling. Studies to support plant life exten- sion require sufficient material of the 60-year-old vintage, subjected to well-characterized neutron irra- diation at high enough exposures to enter material-degradation regimes involving transmutation, segregation, precipitation, helium generation, void swelling, irradiation creep, embrittle- ment, etc. Most currently available specimens in the NSUF Nuclear Fuels and Materials Library (NFML) are rela- tively small in size with the exception of a few specimens produced from AISI 304. Project Description For activities such as training of students, development of new micro- structural and microchemical inter- rogation techniques, or exploration of various degradation mechanisms on LWR-relevant material, the NSUF NFML contains rather large single- heat volumes of AISI 304 stainless steel of the appropriate vintage and technology.These cover a wide, well- characterized range of temperature, dose, dose rate and helium levels. Specimens range from forearm-sized blocks and fist-sized chunks, inch- thick plates, cm-size cubes, mm-thick plates to smaller sizes such as 3 mm-diameter microscopy disks. Most importantly, a number of published studies have been conducted on these materials so that, in new studies, the researchers will know in advance the microstructural and microchemical characteristics of their specimens, as well as their exposure doses, tempera- tures, helium content, radioactivity levels and radioisotope content. It was successfully demonstrated that ultrasonic measurements were in full agreement with density- change and microscopy measurements.