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. 

Reactor refurbishment work that is now underway includes repairs to the vessel refueling plug (RP) and HVAC valves associated with reactor confinement.  After this work is done, the reactor will be reassembled and preparations to restart will be competed. The effectiveness of the cleaning will then 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 the activities planned for the next 8 months. This schedule is the result of a recent rebaselining which included a detailed analysis of all required activities and reflects full resource loading.