Neutron measurement studies at the NIST Center for Neutron Research (NCNR) are on hold for an investigation of a different sort. On February 9, less than a week after elevated radiation levels were detected as the NCNR research reactor was powered up following a scheduled maintenance outage, the Nuclear Regulatory Commission began an inspection at the facility. According to NIST, the reactor will remain shut down until the cause of the release is corrected.
“The first step will be to develop a plan for safely assessing the condition of the reactor so that the root cause of the elevated radiation levels can be investigated,” NIST announced on February 5. “Once that root cause is determined, NIST will identify and then implement all necessary corrective actions.”
NCNR background: The National Institute of Standards and Technology (NIST) is a facility of the Department of Commerce located in Gaithersburg, Md. The NCNR has operated for more than 50 years and it provides neutron measurement capabilities to more than 2,500 U.S. researchers each year to investigate a wide variety of materials and phenomena. The 20-MWt NCNR research reactor provides both cold and thermal neutrons to researchers that can reveal the secrets of structures on a nanoparticle scale. Research carried out at NCNR has been used to improve pharmaceuticals (including vaccines), high-tech alloys, data storage, and more.
Timeline: The alert occurred at about 9:15 a.m. EST on February 3, and staff initiated a shutdown of the reactor. Six workers were initially contaminated during the event, and four additional workers were mildly contaminated while responding later in the day, according to the NRC. All the workers were decontaminated and cleared to return home the same day. On February 4, the affected staff members received additional screening to help determine the precise doses they received. All doses have been confirmed to be below the limits established for radiation workers.
On February 5, NIST announced that, “The elevated levels of radiation within the NCNR’s confinement building have dropped significantly, as expected. Radiation levels outside the confinement building have always been significantly below regulatory health and safety limits and have returned to their normal level of hundreds of times below those limits.”
The NRC reported February 8 that while “a small amount of radioactive material reached the environment, available information continues to show the public near the NIST facility remains safe, as the release was under regulatory limits.”
NRC investigation: The NRC sent two inspectors, to be supplemented by additional inspectors as needed, to begin a special inspection on February 9 to evaluate the cause of the radiation release and worker contamination. According to the NRC, the inspectors will evaluate the adequacy of NIST’s response to the situation, NIST’s determination of the root cause of the event, and NIST’s corrective actions. The inspectors will also review radiation monitoring data and determine if there are generic implications for similar facilities. The NRC inspectors will prepare and release a report about 30 days after the conclusion of their inspection.