Clean & Run

During a routine startup of the NIST reactor in early 2021, a fuel element was damaged resulting in contamination of the reactor's primary cooling loop. Following an extensive cleanup effort involving debris removal and filtering of the primary cooling water, NIST received regulatory approval to restart the reactor in March 2023.  While the reactor can be operated safely and well within regulatory requirements, low-power testing revealed that a small quantity of fuel debris remained in the reactor vessel.  To minimize any operational impacts, additional cleaning was performed in January and February that was successful in removing additional debris from the vessel.  Work is now underway to refurbish parts of the reactor that were removed to clean and then to reassemble the reactor.   

NCNR is also undertaking additional remediations to reduce the operational impacts of any remaining debris. These activities include reducing gas leaks from the reactor vessel (now included as part of reactor reassembly) and the installation of a filtered drain for the primary system (Flange Remediation, Spring 2025).  In addition, some valves in the HVAC system that establish confinement are being refurbished.  While this work is progressing, neutron guides, NG5, NG6, and NG7 are being upgraded.  After reassembly and additional preparations to restart are complete, the effectiveness of the cleaning will be assessed through an extended reactor testing period in the fall of 2025. Once new operating conditions have been established, the NCNR will resume scientific operations, planned for early 2026. As soon as the plan for scientific operations is finalized, the NCNR will issue a new call for proposals.

We present below a high-level schedule depicting the activities planned for the next year. This schedule is the result of a recent careful rebaselining of the project which included a detailed analysis of all required activities and reflects full resource loading.  Note that while rebaseling did change the activities on the critical path, the start of scientific operations is scheduled for early 2026, the same as in the original project plan.