b'TWIST capsule and its associated commissioning tests was completed this year. In-reactor testing of the commissioning series is planned to start next year. Testing of high burnup fuels is expected to begin in the year thereafter. Also, the TWIST device is planned to be used for reactivity-initiated accident experiments for the High burnup Experiments for Reactivity initiated Accidents (HERA) project.Accomplishments:The completion of the final design for the TWIST device and associ-ated commissioning tests officially provides the US with a testing capa-bility for simulated LOCA events. It also provides needed new capability to test larger fuel segments than TREAT capsules used to date since restart. A commissioning LOCA test plan using fresh fuel has been care-fully developed to efficiently demon-strate and qualify the TWIST system. Key data objectives will be evaluation of in-situ instrumentation and the entire extensive experimental infra-structure required to execute TWIST tests. The final design package of the TWIST device includes completed full mechanical design and associated Figure 1. TWIST capsule rendering2022|AFC ACCOMPLISHMENTS 153'