Abstract
The Fuel Cycle Research and Development program is investigating methods of burning minor actinides
in a transmutation fuel. One of the challenges of achieving this goal is to develop fuels capable of reaching
extreme burnup levels (e.g. 40%). To achieve such high burnup levels’ fast reactor core materials (cladding
and duct) must be able to withstand very high doses (>300 dpa design goal) while in contact with the
coolant and the fuel. Thus, these materials must withstand radiation effects that promote low temperature
embrittlement, radiation induced segregation, high temperature helium embrittlement, swelling,
accelerated creep, corrosion with the coolant, and chemical interaction with the fuel (FCCI).
To develop and qualify materials to a total fluence greater than 200 dpa requires development of
advanced alloys and irradiations in fast reactors to test these alloys. Test specimens of ferritic/martensitic
alloys (T91/HT-9) previously irradiated in the FFTF reactor up to 210 dpa at a temperature range of 350–
750 C are presently being tested. This includes analysis of a duct made of HT-9 after irradiation to a total
dose of 155 dpa at temperatures from 370 to 510 C. Compact tension, charpy and tensile specimens have
been machined from this duct and mechanical testing as well as SANS and Mossbauer spectroscopy are
currently being performed. Initial results from compression testing and Charpy testing reveal a strong
increase in yield stress (400 MPa) and a large increase in DBTT (up to 230 C) for specimens irradiated
at 383 C to a dose of 28 dpa. Less hardening and a smaller increase in DBTT was observed for specimens
irradiated at higher temperatures up to 500 C. Advanced radiation tolerant materials are also being
developed to enable the desired extreme fuel burnup levels. Specifically, coatings are being developed
to minimize FCCI, and research is underway to fabricate large heats of radiation tolerant oxide dispersion
steels with homogeneous oxide dispersions.
