Abstract
The HT9 ferritic/martensitic steel with a nominal chemistry of Fe(bal.)12%Cr1%MoVW has been used as a primary core material for fast fission reactors such as FFTF because of its high resistance to radiation-induced swelling and embrittlement. Both static and dynamic fracture test results have shown that the HT9 steel can become brittle when it is exposed to high dose irradiation at a relatively low temperature (<430°C). This article aims at a comprehensive discussion on the thermal annealing recovery of fracture toughness in the HT9 steel after irradiation up to 3148dpa at 378504°C. A specimen reuse technique has been established and applied to this study: the fracture specimens were tested Charpy specimens or broken halves of Charpy bars (13×3×4mm). The post-anneal fracture test results indicated that much of the radiation-induced damage can be recovered by a simple thermal annealing schedule: the fracture toughness was incompletely recovered by 550°C annealing, while nearly complete or complete recovery occurred after 650°C annealing. This indicates that thermal annealing is a feasible damage mitigation technique for the reactor components made of HT9 steel. The partial recovery is probably due to the non-removable microstructural damages such as void or gas bubble formation, elemental segregation and precipitation.
Published Version
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