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.  Subsequent testing revealed that a small quantity of fuel debris remained in the reactor vessel.  While the reactor could have been operated safely and well within regulatory limits, NIST chose to further clean the vessel to minimize any operational impacts.  This work, which was completed earlier this year, was successful in removing additional debris. 

Additional reactor refurbishments, including repairs to the vessel refueling plug (RP) and HVAC valves associated with reactor confinement have also been completed.  The reactor is now reassembled, and preparations for restart are underway.  The effectiveness of the cleaning will be assessed through a reactor testing period that will begin in the fall of 2025.  The NCNR will resume scientific operations and issue a call for proposals in early 2026.

To take advantage of the reactor downtime, neutron guides NG5, NG6, and NG7 are being replaced with modern guides.  Guide upgrade work in the confinement building is now complete, and installation in the guide hall is progressing.

We present below a high-level schedule depicting recently completed activities as well as those planned through early 2026. This schedule is based on a detailed analysis of all required activities and reflects full resource loading.