NIST NCNR Reactor Incident Review – T.E. Mason, Los Alamos National Laboratory

This report summarizes my assessment of the circumstances of the unplanned shutdown of the 

National Institute of Standards and Technology (NIST) reactor on Feb 3, 2021. It covers “the 

conditions that allowed the unplanned shutdown to occur, NIST Center for Neutron Research’s 

(NCNR) emergency response to the incident, NIST’s organizational response to the incident, and 

the efficacy and completeness of the proposed actions” as requested in the charge letter from 

James Olthoff. It is based on material shared with the consultants via a SharePoint site, online 

briefings held in December 2021 and January 2022, and an in person visit to NCNR on February 

1, 2022, which gave us an opportunity to interact with and ask questions of NCNR and NIST 

staff. This summary does not delve into all aspects of the charge but rather focuses on the 

issues I see as being most important and well aligned with my background and experience. The 

specifics of the mechanics of fuel element latching and steps to prevent reoccurrence appear to 

be well understood and undergoing rigorous technical review by both NCNR and NRC. As result 

I will focus more on institutional cultural, organizational, and emergency response concerns 

which have broader implications for the future of safe operations for both NCNR and NIST.

It is important to recognize that while this was a very serious incident, by far the most serious in 

the history of the NIST reactor and probably the most serious operational upset at a research 

reactor in decades, it did not result in any offsite impacts with the dose at the site boundary 

essentially at the limit of detection. Nor did it result in harm to the health and safety of the 

staff on the NIST campus as a whole and the NCNR reactor operations staff in the control room 

who did receive appreciable radiation doses are unlikely to experience any long-term health 

impacts, the maximum dose received was below the regulatory limit. More serious impacts 

were avoided due to the robust design of the reactor and its safety systems and the fact those 

systems were well maintained and operated as designed to shut down the reactor once the 

conditions for a scram were triggered and contain the release of fission products. The 

negligible offsite impact along with effective communications with external stakeholders has 

meant there has not been a loss of confidence in the surrounding communities which is 

important for the long-term future of NIST and the reactor. It suggests that prior efforts by 

NIST to cultivate a positive view of the institution in the community have been of benefit in the 

context of an operational upset. It is worth noting that events which were arguably less serious 

operationally but did result in very small but measurable offsite impacts at the HFBR at 

Brookhaven National Laboratory in New York and DR-3 at Risø National Laboratory in Denmark 

resulted in permanent closure of those reactors due to the resultant loss of confidence in the 

surrounding communities. The absence of offsite impact should not be taken as a reason for 

not responding aggressively to the issues surrounding this event and the assessment that 

follows is intended to provide impetus and support to further strengthen the operations of the 

reactor and NIST.

Resources, Procedures and Training

The proximate cause to the incident was the improper latching of a fuel element during fuel 

reloading leading to it dislodging during the reactor startup. The loss of cooling to the fuel 
element once it was unseated from the reactor base plate led to fuel melting, distribution of 

debris through the primary cooling system, and release of fission products. Proper installation 

of the fuel elements to ensure cooling is maintained is fundamental to the safety of operating 

any reactor. The factors leading to improper latching identified by the NCNR team include 

inadequacy of training and lack of detailed procedures for that aspect of refueling. These 

factors arose due to inadequate staffing, a loss of experienced operations staff over recent 

years, and complacency flowing from a sustained record of routine operations. While the 

reduction of experience amongst reactor operators certainly contributed to this event there 

were precursor events (at least two) where problems with fuel rod latching were observed that 

did not progress due to intervention prior to fuel damage that occurred over a period of 

decades at a time where the staff was more experienced. The failure to properly resolve the 

root causes of those prior events, leading to the Feb. 3 2021 incident, indicates deeper 

problems with nuclear safety culture at NCNR that are acknowledged by the management 

team.

The response to this incident by NCNR management has been comprehensive addressing both 

the specifics of the fuel latching and steps needed to prevent recurrence and the more 

challenging operational and cultural issues that have broader implications. The specific 

measures to prevent recurrence include rewriting, or in some cases writing, more detailed 

procedures not just for refueling but for many reactor operations that had not been described 

previously at that level of detail. In addition, and importantly there are plans to add a fifth shift 

to reactor operations so that the rotation will include an additional period of day shift without 

reactor operating responsibilities to continuously update training and qualifications. Both 

management and the reactor operations staff regard this fifth shift as essential to improving 

operational rigor. The reactor operations staff are skeptical that the needed resources 

(financial as well as the needed staff to fill funded positions) will be realized. This skepticism, in 

part, is derived from the fact that the current four shift operating schedule has been chronically 

understaffed for a long period of time. Due to staffing limitations, it has been a common 

occurrence to have shifts operating with the NRC minimum of two licensed operators while 

normal staffing level would be four. In some cases, there are four including unlicensed 

trainees, but the normal operating cadence has included recurring instances with only two 

operators on shift. This limited staffing has been exacerbated by the fact that as the user 

program has grown, additional tasks have fallen to the operators to assist users outside of 

normal operating hours (for example with crane operations). While there may be 

circumstances where illness or resignation might lead to a temporary inability to full staff a shift 

it is not acceptable for that to be a normal operating condition. The fact it is the minimum NRC 

permitted complement does not excuse this and settling for simple compliance is not the 

hallmark of an excellent safety culture. This represents an instance of normalization of 

deviation.

The chronic shortfall of reactor operations staff is due a combination of increased turnover of 

staff, the time taken for new staff to be qualified as licensed operators, and the challenges of 

recruiting and retention for a skill set very much in demand in the private sector with salaries 

that the federal system cannot compete with. Some use has been made of non-base
compensation tools to help compensate however NIST management should consider a review 

of where the reactor operator positions fit within the federal HR system. These roles, by virtue, 

of the training requirements, shift rotation, and the gravity of the responsibility are certainly

unique within NIST as well as the overall civilian federal system. The fact that loss of qualified 

operators to the Nuclear Regulatory Commission is one element of the retention challenge 

suggests that there may be options within the federal system that would help with this 

problem.

Skepticism about management’s ability to secure the necessary financial resources for a fifth 

shift can also be traced to staff observation of the difficulty in resolving long standing safety 

concerns of a non-nuclear nature (examples cited include ladders and stairwells). This reflects a 

NIST challenge of deferred maintenance and insufficient funding to address infrastructure 

deficiencies that is not limited to NCNR however the inadvertent message sent to staff that 

impacts the nuclear safety culture is that safety is not as important as the marquee scientific 

investments that do attract funding.

NCNR has prided itself on running a very lean operation that is very cost effective in comparison 

to other neutron facilities. It has been successful at upgrading its instrumentation and scientific 

infrastructure so that despite becoming operational in 1969 it remains state of the art in 2022. 

Reactor operations and the associated regulatory framework has not evolved at the same pace. 

The regulatory light touch and the associated lean operating staff levels, procedures, and 

training have been much more static and need enhancement to meet 21st century expectations. 

This will come with a cost and NIST will have to decide if it is willing to accept the cost of 

operating a high consequence nuclear facility on its campus. That cost is more than just the 

NCNR operating budget, there are institutional implications in areas as diverse as human 

resources, emergency management, environment safety and health that go beyond what is 

demanded of a non-nuclear scientific laboratory in terms of overhead and management focus.

 

Emergency Response

Before discussion aspects of the emergency response, it is probably useful to review a brief 

summary of the timeline (more detail is included in the attachment provided at the request of 

the consultants and attached below). At 0916 on Feb 3, 2022 the alert was declared and the 

building evacuated. The Senior Reactor Operator declared an emergency and became Incident 

Commander per the NRC approved Emergency Management Plan. At 1030 the NIST Emergency 

Operations Center (EOC) was activated to provide additional support as needed during the 

emergency. At 1532 the incident was downgraded to Notice of Unusual Event and the EOC

stood down. Four hours later at 1935 the emergency was terminated and the Senior Reactor 

Operator’s Incident Commander role ended. The following day, Feb 4, an attempt was made to 

re-enter the confinement area which had to be aborted due to elevated CO2 levels in the 

basement which resulted in an oxygen deficiency hazard that had not been recognized in the 

pre-entry planning. On February 5 NIST organized an Incident Response Team (IRT) which 

continues to the present to provide senior management oversight and assistance to the 

ongoing recovery effort. Within this timeline the aborted re-entry on Feb 4 is noteworthy 
because over the course of the whole incident it represents the gravest threat to life that 

occurred, it also took place at a time when the emergency was formally ended but the IRT not 

yet stood up.

The Emergency Response to any emergency at NIST falls under the NIST Emergency 

Management Plan (NIST O 2201.00) which in turn is governed by the Department of Homeland 

Security National Incident Management System (NIMS)/Incident Command System (ICS)

concepts. I am most familiar with Emergency Response planning at Department of Energy 

(DOE) facilities but as that also falls under the NIMS/ICS framework as required under DOE 

order 151.1D I believe my conclusions should also be applicable to NIST. There are aspects of 

the timeline outlined above that are surprising in comparison with operating policies at DOE 

facilities and may have contributed to the near miss upon re-entry to the confinement area.

At the DOE sites I am familiar with that operate nuclear facilities a nuclear emergency would 

certainly result in activating the EOC under the Emergency Director as occurred at NIST. What 

status it activated to (1 – full, 2 -minimum, or 3 -monitoring) would depend on the nature of the 

incident but it would remain activated until the Termination Criteria were met as determined

by a corresponding checklist but never before the local emergency was ended (as occurred in 

this case). The EOC would typically remain active at least until re-entry to the control room had 

been accomplished and that would be performed under the Re-entry and Recovery Procedure. 

There would also be development of a Preliminary Recovery Plan to be formally handed off to 

the recovery manager. The role of the EOC is, during the local emergency phase, to provide 

needed institutional support to the Incident Commander – manage external communications 

and tackle other matters to allows the IC to focus on the emergency event. Following 

termination of the local emergency response those roles continue at least until handoff for 

recovery is implemented. One would also expect a Hot Wash and after-action report from the 

EOC to inform future planning.

The re-entry to confinement did involve discussion amongst the re-entry team, the operations 

staff present when the incident occurred, reactor engineering, management etc so there does 

not appear to have been a lack of communication. However, most of the discussion focused on 

nuclear and radiological hazards and the Oxygen Deficiency hazard was overlooked. The 

subsequent re-entry did bring in the NIST Office of Safety, Health, and the Environment (OSHE) 

expertise and fire department who had the training and equipment needed to operate in that 

environment. While it is possible that even had the EOC been active the hazard might have 

been missed it is precisely the role of the EOC to muster those institutional resources who 

possess the needed expertise and equipment. Fortunately, in this instance the re-entry team 

was alert to unanticipated conditions and quickly evacuated when they noticed difficulty 

breathing. There is a very short window between difficulty breathing and unconsciousness, 

brain damage, and fatality.

The apparent disconnect between nuclear emergency response and NIST institutional 

emergency response that was a vulnerability when planning for confinement re-entry is 

probably at least in part due to the relative independence of NCNR as a separately regulated 
entity within NIST as discussed in the context of NIST Institutional Risk Management below. 

The emergent CO2 hazard is an example of the fact that nuclear safety cannot be clearly 

separated from industrial safety. It was a worker safety hazard within the purview of the NIST 

OSHE and the Fire Department but arose as a consequence of a response to a nuclear safety 

issue, the turning off of the ventilation system prior to evacuation while leaving the purge gas 

system active. There is clearly a need to better integrate emergency planning and there should 

be a thorough review (perhaps including peer review) to verify that integration and insure 

consistency with NIMS/ICS particularly with respect to re-entry, termination, and preliminary 

recovery planning. Validation of smooth integration should be an objective of periodic 

exercises which should include reactor relevant scenarios on a fairly regular basis.

In light of the fact that off normal operating conditions can lead to CO2 accumulation in the 

basement consideration should be given to the installation of Oxygen Deficiency monitors in 

the appropriate locations. It appears that the possibility of interlocking the purge gas system 

with the ventilation is also being examined which might also help avoid this situation in the 

future.

NIST Institutional Risk Management

NCNR is unique within NIST which otherwise does not have a nuclear operations footprint, 

while there are some radiological facilities, they have neither the hazards nor the regulatory 

framework of a nuclear reactor. NCNR holds the NRC license for the reactor not NIST. As a 

result, this has led to a structure where NCNR operates in many respects as a somewhat 

independent entity within NIST at least as regards nuclear safety. This arrangement makes 

sense for many reasons, one would not expect NIST to have significant nuclear operations 

expertise outside of NCNR and it doesn’t make sense to develop a parallel organization solely 

for that purpose. Given that situation it is important to recognize and mitigate the 

vulnerabilities that may result. NCNR does draw on expertise in OSHE related to industrial and 

laboratory safety as well as capabilities the fire department has. However, operating as a 

nuclear island within the organization means there are limited resources available to tackle 

matters in that arena and NCNR itself is not a large organization. This is perhaps a bit of a blind 

spot in the NIST Institutional Risk Management framework.

It was surprising to learn the NCNR had only been added to the NIST Risk Matrix shortly before 

the incident and only then in the context of an ageing reactor that might not meet beam 

delivery needs of the scientific community. The fact it represents the highest hazard operation 

across all of NIST seems not to have been formally recognized. While the NRC license and 

NCNR design are predicated on the absence of a possibility of offsite impact the potential 

adverse consequence of a serious accident in terms of NIST reputation and risk to staff should 

elevate the visibility and management attention. The primary independent oversight 

mechanism is the SAC but it only meets once a year and seems primarily to inform NCNR as 

opposed to NIST senior management. Consideration should be given to enhancing the role of 

the SAC perhaps by augmenting its annual meetings with targeted deep dives into topics of 

concern making use of the broader external peer community. In addition, there needs to a be a 
greater visibility on the part of NIST management into the unique hazards and challenges faced 

by operating a nuclear reactor in a relatively open campus located in a dense suburban 

environment. Note that it would not make sense to fold NCNR into NIST facilities operations, 

that would likely have adverse impacts on both reactor operations and balance of plant due to 

the significant differential in requirements for operational rigor and the associated cost 

differential. Other mechanisms to explore better integration should be explored. There also 

needs to be a recognition that non-nuclear safety needs can impact nuclear safety directly and 

indirectly, I expect NRC would take an interest in an accident involving a ladder needed to 

access nuclear systems for example. In the minds of some staff there seems to be some 

conflation of lack of action on industrial safety issues with lack of action to address reactor 

operations staffing shortfalls – both being taken as examples of lack of management 

commitment to safety.

Conclusions

The response to this event by NCNR management has been robust and comprehensive with 

demonstrated ownership of the issues identified by NCNR and NIST senior management. The 

root causes and corrective actions extend well beyond the specifics of the fuel latching problem 

that triggered the Feb 3 event to include not only procedural and training deficiencies but also 

cultural aspects that developed slowly and will take time to address. The 19 Corrective Action 

and Recovery Items teams are tackling a wide range of topics that together should allow safe 

resumption of reactor operations. This is a substantial body of work, and some aspects will 

extend beyond reactor restart date. With the reactor being shut down it can be the primary 

focus of the entire reactor operations team and NCNR management supplemented as needed 

under the auspices of the IRT from NIST resources. However, once the reactor restarts the 

focus will necessarily shift to reactor operations and may lead to difficulties sustaining the 

needed improvements post restart when reactor operations and the user program are 

resumed. Adding a fifth shift will help but it will take time to recruit and train the new staff. To

ensure needed improvements are sustained into the operating phase there may need to be 

tradeoffs in terms of resources and reactor operating cadence that will be difficult decisions to 

make. However, if focus dwindles post restart, history may repeat itself.

The main line of effort to improve the operational safety culture at NCNR is the development of 

more detailed procedures for operations that had previously not be well defined and the 

training the accompanies those more rigorous procedures. There are many areas of activity 

that need this increased rigor and the cost that goes with it. It is important to remember that 

the goal is to better optimize for a safer work environment, and it is possible to overcorrect –

going too far can actually degrade safety if overly complex, prescribed procedures result that 

are difficult to understand and follow. The Institute of Nuclear Power Operations (INPO) has 

studied this and documented in their cumulative impact report.

The restart itself is by no means straightforward. Exactly what will be needed is still uncertain 

as unexpected conditions may emerge as the cleanup progresses. The contamination of the 

primary cooling system and associated radiation levels make this a set of operations that must 
be carefully planned and executed in a disciplined way. Upsets during the cleanup could erode 

confidence that has already been shaken by the event. There may also be difficulties balancing 

the risk of cleaning up and the risks left in terms of ALARA and future operations as well as 

possible variability in the residual radiation. It will not be possible to return to totally pristine 

state (of course in some sense it hasn’t been pristine since first criticality). 

The NCNR is an important component of the nation’s scientific infrastructure. It is important to 

resume operations to allow the contributions made by NCNR to continue however that can only 

be done if the issues revealed by this incident are addressed. Furthermore, the facility is robust 

and has been well maintained but will not last forever. Given the long timeline for a 

replacement it is appropriate to be thinking about and planning for replacement even as NCNR 

is returned to service.
Overall timeline of fuel failure event

Date/time Reactor actions NIST actions

January 4

0800 refueling

1500 Latch checks

February 3

0816 Reactor startup begins

0909 Fission product release

0916 Alert declared; building evacuated

0929 NRC notified NIST management notified

~1030 Incident command center 

established (ESO)

~1300 Building reentry to complete 

shutdown activities

1532 Downgraded to Notice of Unusual 

Event (NOUE)

1713 Email announcement to 

NIST staff by Jim Olthoff 

1935 Terminated emergency

February 4

0800 Initial briefing on status, possible 

building reentry to assess radiation 

conditions

1430 Entry into confinement; CO2 issues 

forced evacuation

February 5

Incident Response Team 

formed

February 6

0920 Entry into confinement with SCBAs, 

escorted by NIST FD

0930-0940 Restarted normal ventilation

February 8

Began ~daily entries into 

confinement

IRT initial meeting

February 9

NRC Special Inspection begins

Briefing on event to 

Congressional staff and 

city reps

February 10

NIST town hall meeting

Briefing on event to House 

Science Committee Staff