Research and test reactor oversight probed by NRC IG after NIST fuel failure

October 11, 2023, 9:45AMNuclear News
A view of the NCNR guide hall, featuring the 30-meter Small Angle Neutron Scattering instrument. (Photo: NIST)

Following the February 2021 radiation release at the National Institute of Standards and Technology (NIST) resulting from a fuel failure in the 20-MWt NIST Center for Neutron Research (NCNR) research reactor, NIST investigated the root cause of the incident and developed corrective actions. The Nuclear Regulatory Commission’s probe of the incident found apparent violations and resulted in a confirmatory order issued in August 2022.

Now, the NRC’s Office of the Inspector General (OIG) has released its own report—Special Inquiry into the U.S. Nuclear Regulatory Commission’s Oversight of Research and Test Reactors—which turns attention to the effectiveness of the NRC’s oversight of research and test reactors (RTRs) such as the NCNR, and the potential for systemic issues in that oversight.

Thorough and far-reaching: “This report demonstrates that the same or similar causes that led to the NIST event have ramifications for other RTRs nationally,” said inspector general Robert J. Feitel in a recent news release. “The OIG’s investigative and technical staff must be commended for such a thorough and far-reaching report that demonstrates superb, independent oversight.”

Feitel added, “As our report shows, addressing opportunity areas in the NRC’s RTR program is vital to ensuring successful regulatory oversight of new projects, such as medical isotope facilities and prospective RTRs based on advanced reactor technology, since these programs are currently planned to be reviewed under RTR policy guidance.”

In a September 29 letter from Feitel to NRC chair Christopher Hanson, Feitel requested that the NRC notify the OIG “by January 29, 2024, what corrective actions, if any, the NRC will be taking based on the results of this special inquiry.”

The incident: The NIST research reactor has been operating since 1967, typically with a routine shutdown every five and a half weeks. On February 3, 2021, it was being restarted after a refueling outage. As the reactor approached full power, several radiation monitors, including the confinement exhaust stack radiation monitor, showed a sudden increase, indicating a release of fission products and a probable fuel cladding failure. The reactor automatically scrammed, and staff declared an alert. Investigations showed that one fuel element had not been properly latched in place and was not in normal grid position in the reactor core. This prevented adequate coolant flow to the fuel element, and a fuel cladding failure occurred in a matter of minutes. No reactor structures, apart from the single fuel element, were damaged, and the reactor was maintained in a stable shutdown condition.

The February 3 event caused a radioactive release to the environment and “was one of eight unscheduled incidents or events in fiscal year 2021 that the NRC determined to be significant to public health or safety,” according to the OIG report.

The scope of the investigation: While the focus of the Special Inquiry broadened from the 2021 NIST event to include consideration of the NRC’s oversight of other RTR facilities, the report “primarily discusses the NRC’s oversight of the NIST test reactor prior to the February 2021 event, because the event highlights areas in which the agency’s oversight could be improved as it relates to other smaller nuclear facilities.”

The OIG found that the agency’s RTR program “failed to identify and address problems with the NIST test reactor and other RTRs, specifically: (A) the NRC failed to identify problems with fuel movement, including precursors to later events; (B) the NRC’s inspection practices often lacked direct observation of activities important to safety; (C) RTRs other than the NIST reactor experienced significant fuel oversight issues; and, (D) the agency’s RTR program has not been substantively updated for at least two decades, and does not reflect the agency’s risk-informed and safety culture positions.”

Specifics: According to the report, the NRC didn’t follow up on NIST audit committee reports identifying deficiencies with safety culture and operator training and requalification. Additionally, “the NRC had not directly observed the fuel element latch checks following fuel movement at the NIST test reactor in the five years prior to the event.”

An NRC Safety Assessment Committee (SAC) carried out audits of the NCNR prior to the February 2021 incident and identified at least four safety culture and/or complacency issues, according to the OIG report, and some of these issues the NRC “did not capture in its inspection reports.” For example, “in 2019, the SAC noted that there was a complacency issue at NCNR and recommended a periodic Safety Conscious Work Environment (SCWE) survey be performed across the NCNR to assess the underlying safety culture and general attitude toward safety. The report stated, ‘NIST and the NCNR are fortunate and have not had a recent major safety incident. . .’.”

Expanding the scope: The OIG Special Inquiry includes the results of an investigation into the NRC’s oversight of the Aerotest research reactor in San Ramon, Calif., from about 2000 to 2010, and oversight of the University of Texas research reactor prior to a 2022 incident in which the incorrect fuel was used.

The OIG concluded that “the agency’s RTR inspection program policy and guidance are outdated because they do not implement risk-informed approaches and safety culture elements. The last major revision to the safety inspection program was in 2004.” The NRC is currently responsible for oversight of 30 operating RTRs and anticipates future oversight of advanced reactor prototype test reactors.


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