The US Department of Commerce’s National Institute of Standards and Technology (NIST) said that it had submitted two reports and supplemental information on the February alert at the NIST Centre for Neutron Research (NCNR) to the Nuclear Regulatory Commission (NRC). On 3 February staff had responded to an alert of elevated radiation levels in the confinement building of the NCRC at Gaithersburg in Maryland.
The alarm occurred during restart of the research reactor there after a regularly scheduled maintenance period. In response to the alarm, staff followed established procedures and immediately initiated a shutdown of the reactor. Several trained radiation workers were exposed to the elevated radiation levels and underwent standard decontamination and evaluation.
The reports include a root cause analysis of the alert, NIST’s planned corrective actions, and a review of the NIST response to the incident. With the reports, NIST has submitted a request for permission to restart the reactor, contingent upon all necessary corrective actions and restart preparations being completed.
The following root causes are identified in the reports:
- The training and qualification programme for operators was not on par with programmatic needs;
- Written procedures did not capture necessary steps in assuring fuel elements were latched in place;
- Procedural compliance was not enforced;
- The equipment and tools used to determine whether fuel elements were securely latched in place were inadequate;
- Management oversight of refuelling staffing was inadequate;
- The NCNR’s change management programme was insufficient; and
- The reactor operations group had a culture of complacency.
“We take these findings very seriously, as they absolutely are not consistent with NIST’s dedication to safety and excellence,” said James Olthoff, who is performing the non-exclusive functions and duties of the under secretary of commerce for standards and technology and NIST director. “We have already begun implementing many corrective actions and I’m confident that these changes will strengthen our programme and ensure the safe operation of this important national resource for years to come.”
The initial root cause investigation was completed by a working group of NIST technical experts who identified five root causes. A subcommittee of NIST’s Safety Evaluation Committee, which included NIST staff members and an outside expert, performed a further review of the technical working group’s analysis and added an additional two root causes.
Both groups identified a total of 18 corrective actions that NIST will take to address the root causes and to ensure such an event does not happen again. The safety subcommittee also reviewed NIST’s response to the alert and determined that “safety systems functioned as intended, defined roles were fulfilled quickly and correctly, and defined processes and procedures were implemented.”
“While I am disappointed by the root causes, I am pleased that the safety systems and NCNR staff responded extremely well during the alert,” said Olthoff. Four external experts will now review the NIST analyses and planned corrective actions, as well as the organisational response to the event. NRC will complete a special inspection and issue its own report before fully reviewing the restart request.