2018 | AFC ACCOMPLISHMENTS 150 The Nuclear Technology Research and Development (R&D) program is investigating options to transmute minor actinides. To achieve this goal, new fuels and cladding materials must be developed and tested to high burnup levels (e.g. >20%) requiring cladding to withstand very high doses (greater than 200 dpa) while in contact with the coolant and the fuel. Project Description: To develop and qualify materials to a total fluence greater than 200 dpa requires development and testing of advanced alloys and irradiations in fast reactors. Specimens of previously irradiated HT9 specimens are being irradiated in a fast reactor to high doses (>200 dpa). In addition, improvements in the radiation tolerance of HT-9 are being made through minor changes in the composition. Advanced radiation tolerant materials with fine oxide dispersion strengthening are also being developed to enable the desired extreme fuel burnup levels. This fine microstructure provides an alloy with high strength at high temperatures and excellent radiation tolerance (e.g. reduced void swelling and ductility retention at low temperatures) but also increases the difficulty of producing engineering Fast Reactor Cladding Material Development Principal Investigator: Stuart Maloy Collaborators: Eda Aydogan (LANL), Ben Eftink (LANL), Dave Hoelzer (ORNL), G. Robert Odette (UCSB), John Lewandowski (CWRU), J. DeCarlan (CEA), D. Sornin (CEA) parts (e.g. thin walled tubes) from these advanced materials.Thus, in this project, research is underway to produce tubes using techniques such as high temperature hydrostatic extrusion, intermediate temperature plug drawing and low temperature pilger processing. Accomplishments: Progress has been made at understanding the effects of small levels of nitrogen on the properties of ferritic/martensitic steels. Heats of Fe12Cr0.2C alloys were produced with low (10 wppm) and high (500 wppm) levels of nitrogen. Ion irradiations were performed on heats with and without nitrogen to doses of 0.5 and 1.0 dpa at 300C using the Ion Beam Materials Laboratory at Los Alamos National Laboratory (LANL).The results showed a much higher uniform density of loops in the high nitrogen alloy (Figure 1) where it is postulated that the nitrogen is nucleating loops under irradiation. Higher dose irradiations were performed using iron ions to a maximum dose of 23 dpa showing that hardening saturates after 2-3 dpa. Research continues on a large heat (50 kg) of a nanostructured ferritic alloy (14YWT) that was produced through a collaborative This research is critical to the application of advanced Oxide Dispersion Strengthened (ODS) steels to engineering applications as it addresses one of the most difficult tasks which is to produce tubing from these radiation tolerant, high strength steels and the stability of these steels at very high doses.