Nuclear Accident Root Cause Analysis – NRC Expectations for RCAs

In 2021, a nuclear fuel element failure and release of radioactive fission products occurred at the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) research reactor during a post-refueling startup. “A root cause analysis was subsequently performed to identify the cause of the fuel failure and prescribe corrective actions to prevent recurrence,” which was subsequently evaluated by five independent consultants using TapRooT® RCA and National Safety Council investigation methods.

Read or Download .pdf: NRC.gov Report

Narrative

“On February 3, 2021, the NBSR reactor was conducting a normal start up after completing a refueling on January 4, 2021. Upon approach to full power, the plant experienced a sudden drop in power level and rapid increases on several radiation monitors, including fission products monitor (RM 3-2) and the stack monitor (RM 4-1). A major scram was automatically initiated when the stack monitor reached its setpoint of 50,000 counts per minute, and an immediate activation of the confinement isolation system sealed off confinement to prevent or limit release of radioactive material from the facility. NCNR and NIST staff took emergency actions…The emergency was terminated later that day and the staff began recovery actions.”

“One fuel element, that was thought to be secured, had lifted out of its secured position in the lower core grid plate and was skewed in an apparent unlatched condition. This resulted in a lack of cooling to the element and fuel failure as reactor power level was raised. The consequences of the accident included significant fuel damage and resultant release of radioactive fission products, violation of plant Technical Specifications, increased radioactive dose exposure to NCNR personnel, long-term loss of facility use, and considerable costs associated with cleanup and recovery.”

Independent Evaluation

NIST and NCNR conducted an RCA, and the US Nuclear Regulatory Commission (NRC) chartered five independent nuclear industry RCA expert consultants

“to assess the rigor, criticality, and overall quality of the event root cause [analysis], and to identify gaps in meeting associated inspection criteria.”

Their report…

“…found that NCNR and NIST staff have expended a considerable level of effort evaluating the accident and prescribing corrective actions to fix the identified root causes…The overall assessment conclusion is that, while the event root cause provides sufficient actions such that they can be reasonably expected to prevent another undetected latching event, there are significant structural evaluation issues indicating that the root cause conclusions are not at the appropriate depth to ensure underlying organizational or cultural drivers are identified and actions prescribed. The likely result is an adverse impact on the effectiveness of the [RCA] in the long-term prevention of recurrence of this event, and similar events, that can challenge sustained organizational improvement. This presents a vulnerability to NCNR from a rigor of evaluation, effectiveness, and inspection perspective.”

(underlined emphasis mine)

Areas for Improvement – No Systematic RCA Process or CAPAs

HUGE RCA effort, but the four Areas for Improvement (AFI) show there was little systematic process, including corrective actions.

AFI #1 – DIG DEEPER: …”Root cause conclusions are not at the appropriate depth to ensure underlying organizational or cultural drivers are identified and actions prescribed.”

AFI #2 – S.M.A.R.T.E.R. CAPAs: “Corrective Actions specified for each root cause were not, in all cases, specific enough to implement reliably, measurable to ensure the organization can determine when adequately completed, or relevant (i.e., tied logically with the stated root cause).”

AFI #3 – NEED RCA TRAINING: “NCNR staff need additional training to improve skills and knowledge related to conduct and oversight of root cause analysis for significant events.”

AFI #4 – S.M.A.R.T.E.R. CAPA (AGAIN): “There are significant gaps in closure documentation for the corrective actions prescribed by the event root cause due to not having a fully effective Closure Review Board and Closure Notebooks with complete closure documentation to support review.”

The report’s conclusions are unambiguous:

“AFIs #1 and #2 warrant a re-write/integration of the root cause reports and additional evaluation to analyze, in aggregate and using a more rigorous structure, the existing root causes to determine if they can be explained by more fundamental underlying factors. This should be completed as soon as practicable.”

“Additional actions are recommended in the report to provide training to root cause evaluators and oversight personnel in the standard and conduct for performing a root cause analysis (AFI #3) and to strengthen corrective action closure documentation and oversight for actions prescribed in the root cause analysis (AFI #4).”

Next Steps for NIST / NCNR

First, obvious, fix AFI #3 “NCNR staff need additional training to improve skills and knowledge related to conduct and oversight of root cause analysis for significant events.”

TapRooT®’s 5-Day Advanced RCA course provides extensive training and structure to correct all four areas for improvement.

AFI #1 – DIG DEEPER. Investigators learn for Human Performance and Equipment Difficulty investigations. Human Error is NOT a Root Cause; it is the starting point of a TapRooT® Root Cause Analysis.

AFI #2 and #4 – S.M.A.R.T.E.R. CAPAs. TapRooT® students perform many exercises, writing, coordinating, assigning, tracking, and closing out proper corrective actions. S.M.A.R.T.E.R. is the full acronym used by programs that don’t let weak CAPAs on the books, and that close out all CAPAs created.

• Specific
• Measurable
• Accountable
• Reasonable
• Timely
• Effective – check that we actually fixed the problem!
• Reviewed – for unintended consequences

Register for an in-person or online TapRooT® or Equifactor® certification course to start your TapRooT® Journey: https://store.taproot.com/courses

Contact your TapRooT® strategic advisor to develop your implementation plan and schedule a private on-site course at your facility.