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Information and Q&A on the Feb. 2021 NCNR Alert

The following questions include those asked during a Feb. 10, 2021, community meeting or submitted via email. Some of the answers were updated as new information became available. The most recent updates were made March 7, 2023.

Please submit additional questions to NISTG_CommunityAffairs [at] (NISTG_CommunityAffairs[at]nist[dot]gov), and we will add them to this page.  

For more information, read the remarks delivered by NIST’s Jim Olthoff during the Feb. 10, 2021, community meeting and these related news releases:

NCNR — NIST Center for Neutron Research
NRC — Nuclear Regulatory Commission

Community Health

A. On Feb. 3, passive gamma radiation monitors at the NIST fence line did not measure any elevated levels of radiation. Air samples measured a concentration of cesium-138 at the boundary that was 1.4% of the regulatory limit, or 1 x 10-9 µCi/ml (microcuries/milliliter).

The value measured at the fence line was present only during the initial event, further indicating that the dose to the public was very small. Measurements taken at the ventilation stack indicate that on Feb. 3, the concentrations of xenon-133 and xenon-135 at the boundary were less than 10% of the regulatory limit, or 5.8 x 10-9 µCi/ml and 5.4 x 10-6 µCi/ml.

A. The dose rate at the NIST fence line is continuously measured with detectors and is typically about 0.01 to 0.02 millirem/hour due to background radiation. These levels can fluctuate slightly based on environmental conditions, for example, low air pressure from a storm can cause naturally occurring radon in the soil to flow more quickly into the atmosphere. No significant change was seen on these detectors as a result of the event. Based on radiation measurements made at the reactor stack, the maximum total dose a member of the public could receive was less than 0.5 millirem, or 1/200th of the regulatory limit and still at normal levels.

A. Radioactive iodine was not detected offsite.

A. No. The facility is designed to ensure that the public remains safe at all times, and all systems worked as designed on Feb. 3, 2021. The updated information, found by performing due diligence in reviewing all of our calculations, confirms that the public was safe and that dose limits at the fence line remained well below regulatory health and safety limits at all times. The concentrations of three isotopes measured at the fence line were higher than originally calculated, but still well below safety limits. These new calculations do not affect the dose limit we had previously reported, which was based on real-time measurements in the confinement building’s ventilation stack.

A. Yes. NIST performs routine water sampling at three locations on the NIST property and four sites off the campus on a regular basis, as required under our license with the Nuclear Regulatory Commission. The Long Draught Branch Stream is one of these routine sites and was included in the sampling done on Friday, Feb. 26, 2021. All tests show the environment and community are safe.

A. Wastewater refers to the water that is released down the drains within the NCNR facility, such as through a bathroom sink or, in this case, a shower. Water from the facility is carefully tested to ensure it is safe to release into the wastewater system, which is separate from drinking water supplies.

A. No. No water was released into the drinking supply or the environment as a result of this event. Wastewater from showers used to decontaminate our staff was sent into the wastewater system (which is separate from the drinking supply) at levels less than 1/1,000th the sanitary sewer release limits.

A. Radiation levels remained at normal levels at all times.

A. We have radiation monitoring around the NIST fence line that allows us to do detailed measurements of radiological conditions around our facility. The levels remained well below regulatory limits at all times.

A. The regulatory limits are designed so that there are no health impacts. For a member of the public, the regulatory radiation dose is 100 millirem per year. A radiation worker’s annual occupational radiation dose is 5,000 millirem.

The average, naturally occurring background radiation that everyone on Earth receives is about 300 millirem per year. Adding in medical exposures (from X-rays or CT scans, for example) and other human-made sources, the average American receives about 620 millirem per year. On a round-trip cross-country flight, you would receive a dose of about 5 millirem. The dose at our fence line was less than 0.5 millirem.

Learn more about sources of radiation on the NRC website.

A. Yes, the limit for the public covers everyone.

A. Radiation doses are commonly measured in units called rem, or millirem (1 rem equals 1,000 millirem). The allowable dose for a member of the public set by federal regulation is 0.1 rem or 100 millirem per year.

A. As noted in our 14-day report to the NRC, radiation dose monitors at the NIST fence line indicate that the dose remained at normal levels during this event. An analysis of all air samples taken show the dose at the 400-meter boundary as a result of this event was less than 0.5 millirem. The NCNR’s filtration system performed as designed, so the public was safe at all times.

A. The very low concentration of radiation released stayed well below regulatory health and safety limits at all times. These limits are designed to keep the public safe and free of any health effects. The small concentrations of radiation that left the stack were further diluted by the air outside the building, and our fence line measurements show that the dose levels there stayed well below regulatory limits and the public was safe. Our staff who were within the confinement building at the time of the event received doses that were well below anything that might cause a health effect, and therefore anyone outside the building, where dose levels were even lower, would remain safe.

A. Concentrations of radiation in air released by the confinement building’s ventilation system remained below regulatory health and safety limits at all times. Measurements at the fence line indicate the dose rate remained at normal levels at all times, far below regulatory limits.

A. Yes, we have monitors positioned to cover every direction.

A. As part of our normal radiological surveillance plan, we regularly take soil samples around the site. Our measurements show nothing above background levels, and the environment has remained safe.

A. Our facility and its safety systems are designed to keep the public safe at all times. Through our NRC licensing process, it has been determined that even in the worst-case scenario, the NIST campus and nearby community would remain safe because any release of radioactivity would remain well below regulatory health and safety limits. Therefore, iodine pills are not necessary.

A. As part of its licensing process, the NRC has determined the community is safe when the NCNR research reactor is operating. Both the NRC and an independent group of experts will review NIST’s assessment of the Feb. 3 event and corrective actions. [Update: The reports from the outside experts retained by NIST were made available on the NIST website in August 2021. Findings from the NRC are available on the NRC website.]

A. Our sensors indicate that radiation dose levels remained well below regulatory health and safety limits at our fence line, which tells us the areas beyond the fence line also remained safe at all times. Our work will be checked by the NRC and an independent group of experts. [Update: Reports from the outside experts retained by NIST were made available on the NIST website in August 2021. Findings from the NRC’s special inspection are available on the NRC website.]

Reactor Safety

A. This was the first such event in the NCNR’s more than 50 years of operations that caused the confinement building to be evacuated due to increased levels of radiation. Our staff practice safe evacuation during regularly scheduled emergency drills.

A. No. When the reactor is shut down, there is no nuclear reaction, or fission, happening. The fuel is kept cool by the reactor safety systems.

A. No, there have been no other events similar to what we experienced on Feb. 3, 2021, in the NCNR’s more than 50 years of operation.

A. A detailed analysis of such a worst-case scenario is an essential part of the NIST Safety Analysis Report that has been reviewed and approved by the NRC. The scenario — involving a failure within the reactor core — considers conservative assumptions expected to lead to the most severe consequences. The most severe consequence for the NIST research reactor would be a limited release of radioactivity below regulatory health and safety limits, and the public would remain safe.

A. Yes. Even in the worst-case scenario of a reactor failure, it has been designed so the public remains safe.

A. NIST takes emergency planning and response very seriously. We conduct annual drills for our staff and NIST’s emergency response professionals, including the NIST fire department, as well as tabletop exercises. Before each reactor startup, we test every component of our operation and safety systems to ensure they are working properly. Those systems performed as designed in this event.

A. Small amounts of radioactive materials from decontamination can be released safely into the wastewater system according to federal regulation, and all water from the NCNR is carefully tested to ensure it is safe to release into the wastewater system. As an additional step going forward, water from the decontamination of personnel will go into special holding tanks to allow any elevated radiation levels to decrease and be analyzed before the water is safely disposed of as wastewater or through an authorized disposal company.

A. There was no leak associated with the reactor. In 2017, in a laboratory building separate from the NCNR, a radiation source used for equipment calibration was damaged in its storage container and caused a limited amount of contamination in that building.

NRC response: That material in that case was authorized under a separate NRC license. There was an inspection performed related to that event as well. The contamination was limited to a small area in another building. The NRC inspection report was released in June 2018.

A. Air leaving the confinement building is filtered by a special ventilation system to ensure any release remains below regulatory limits during normal operations and in the event of a situation such as the one that occurred on Feb. 3. Water from the facility is carefully tested to ensure it is safe to release into the wastewater system, which is separate from drinking water supplies. Water in this area does not come from local groundwater but is supplied by the Washington Suburban Sanitary Commission’s Potomac Water Filtration Plant.

A. The current NRC license allows the NCNR to operate through 2029. The research reactor goes through routine maintenance and upgrades to ensure it can operate safely. We have not considered relocating the facility because it is considered extremely safe where it is.

A. It is the responsibility of the U.S. government to protect its assets from an attack of an enemy of the state.

A. There is no need for external alarms because the facility and its safety systems are designed so that external radiation levels never exceed regulatory limits. There is an alarm within the building to alert staff when elevated radiation is detected.

A. No assistance was needed from off-site emergency response. However, we have been communicating with local officials and have updated our procedures so that they will be promptly notified should a similar event occur in the future.

The Event Itself

A. After the reactor was shut down on Feb. 3, the control room was evacuated to ensure the safety of staff. A second control location outside the confinement building but within the NCNR facility allowed for 24/7 remote monitoring and control of ventilation systems while the control room was decontaminated.

A. Sensors within the confinement building registered increased levels of radiation within the building. The precise cause won’t be determined until we can decontaminate, go in and assess conditions inside the reactor. [Update: It has been determined that the failure was caused by a fuel element that was not properly latched into the core and received insufficient cooling, resulting in damage. Reports detailing the failure event and root cause can be found on the NRC website.]

A. All event reports to the NRC are posted publicly in its ADAMS system, including NIST’s 14-day report on the Feb. 3 event. [Update: Additional NIST reports to the NRC can be found here.]

A. No. The IT system for the reactor is completely isolated from other systems to provide high levels of security.

A. There was no in-core maintenance done prior to the startup, only routine refueling of the reactor.

A. We acknowledge that we took too long to let the community know it was safe. We determined early on that the event posed no health risk to the public and focused our efforts on gathering information to provide an accurate and full picture of what had happened. We recognize now we should have interacted sooner with a simple message and have updated our procedures to do so if necessary in the future. The email list for receiving updates from NIST is new and will be used to keep the community up to date on our progress. The community is welcome to submit questions at any time via the email address NISTG_CommunityAffairs [at] (NISTG_CommunityAffairs[at]nist[dot]gov).

A. As noted in our 14-day report to the NRC, very small concentrations of cesium-138, xenon-138 and krypton-87 were measured in the confinement building ventilation stack. On Feb. 3, a very small concentration of cesium-138 was measured at the boundary, and on Feb. 4, very minute concentrations of xenon-133 and xenon-135 were measured there. All were well below regulatory health and safety limits. The half-lives of these products range from 14 minutes (xenon-138) to five days (xenon-133).

A. No toxic chemicals were released. The NCNR does not use or create any toxic chemicals.

A. We won’t know exactly what caused the failure until we can use specialized camera equipment to look into the reactor. The elevated levels of radiation indicated the potential for a fuel cladding failure, but at this point we do not have enough information to confirm the exact cause of the event. [Update: It has been determined that the failure was caused by a fuel element that was not properly latched into the core and received insufficient cooling, resulting in damage. Reports detailing the failure event and root cause can be found on the NRC website.]

A. No. Our staffing of reactor operations and our radiation safety personnel have not been impacted by COVID-19 precautions. We do have COVID protocols in place, such as mask wearing within the building and social distancing, but these protocols have had no impact on the safe operation of the reactor.

A. No. Xenon is created as part of the nuclear fission reaction in the reactor. There is no plasma involved in fission.

Post-Event and Decontamination

A. Yes.

A. The NIST research reactor has a total of 30 fuel elements in its core. An initial review of the interior of the reactor indicates damage to a portion of one of those elements. The fuel element will need to be removed and fully studied before we can determine the full extent of the damage. NIST will continue to update the community as we have more information to share. [Update: The damaged fuel element was removed, and NIST has provided regular updates to the community, which can be found on the NIST website.]

A. NIST issued a news release on March 2 announcing that a fuel element was damaged.

A. We won’t know for certain until we can determine what went wrong and develop a plan for corrective actions. We will post public updates on our progress. [Update: Corrective actions can be found on the NRC website.] 

A. Radioactive particles have been captured in ventilation filters and have settled on surfaces within the confinement building. Our trained radiation workers must now wipe down every surface. Filters, cleaning materials and personal protective equipment (PPE) are collected and stored in temporary radioactive waste storage areas. An approved commercial vendor then disposes of this material according to federal regulations.

A. We do not know how long decontamination will take. We will take regular surveys of the confinement building throughout the decontamination process to determine when decontamination is complete. [Update: Decontamination of the building was completed in 2022.]

A. Our staff are trained and experienced in decontamination. There are no additional risks to the staff performing the work.

A. The reactor is shut down and in a safe state. Trained radiation workers have been assessing the radiological conditions within the confinement building and have begun the decontamination effort. The next step is to insert a special camera into the reactor so we can begin to assess what happened. We expect that effort to take some time.

A. We have our radiation specialists looking at that as part of our analysis of what may have failed.


A. Our facility and its safety systems are designed to keep the public safe at all times. Through our NRC licensing process, it has been determined that even in the worst-case scenario, the NIST campus and nearby community would remain safe because any release of radioactivity would remain well below regulatory health and safety limits. Therefore, an alarm is not necessary. NIST has updated its emergency communications procedures to more quickly notify neighbors of activities on its campus, including emergency response. Community members may sign up for email updates from NIST and follow us on Twitter or Facebook.

A. The NCNR was built during the 1960s, and the research reactor has been operating since 1969. The reactor is a purpose-built resource for the U.S. scientific community, built and operated to assure that the health and safety of the public and staff are always protected. The reactor and confinement building were part of an integrated design and built together.

A. Unfortunately, science at the NCNR stops when the reactor is shut down. With nearly half of all neutron research in the U.S. conducted at the NCNR, this shut down will have a major impact on the U.S. research community. We are working with our colleagues at the Oak Ridge National Laboratory and overseas to see if some experiments can be supported elsewhere.

A. NIST does not do dosimetry at the NCNR. NIST dosimetry is provided by the Naval Dosimetry Center in Bethesda, Maryland.

A. We regularly monitor the environment around the facility for increased levels of radiation, and the levels have always remained well below regulatory limits. Our trained radiation workers in the NCNR wear dosimeters so that we can ensure their dose levels remain below the limits for radiation workers. The confinement building is designed to keep radiation levels outside of it below regulatory limits; therefore people or animals on or near our campus remain safe. These regulatory limits are created to protect both people and the environment, including animals.

A. Every experiment at NIST undergoes a hazard review process in advance to minimize risk to staff. With those safety protocols in place to minimize risk to the staff working on the experiment, the possibility of an event occurring that would put other staff or the public at risk is extraordinarily low. We have engineering controls as well as operation controls that work to keep people safe.

A. We do not currently have plans, but if we have additional information to provide and the community would like a meeting, we will schedule one. [Update: A public meeting was requested by the Quince Orchard Homeowners Association and held in August 2021. The NRC has held multiple public meetings.]

A. No one was injured in this event. The trained radiation workers who were exposed were decontaminated promptly and cleared to go home the same day. Testing has shown the doses they received were well below the limits for radiation workers.

A. NIST is a federal laboratory that conducts research into a wide variety of sciences. We have a small nuclear research reactor that is used to support science — not produce power. The research reactor, which is much smaller and simpler than a nuclear power reactor and has been in safe operation since 1969, allows us to peer into materials and observe processes that are impenetrable to other methods.

A. The operations schedule of the reactor is always accessible on the NIST public website.

A. There are sensors located on the ventilation stack and various distances from the NCNR, including at our fence line. Additionally, our staff conduct regular environmental sampling as part of our regulatory requirements.

Questions for Which the NRC Provided Answers

A. We just started the inspection. Knowing that it will take NIST a while to figure out the cause of the event, our inspection won’t be complete until after NIST has completed its evaluation and determined root cause and corrective actions. That will likely take a number of months. We typically issue a report within 30 days after finishing an inspection. We are considering issuing an interim inspection report that would also be made public. [Update: The NRC interim inspection report and final inspection report can be found on the NRC website.]

A. Typically within the NRC when we think of severity we think about level of violation. In this case, we’re just now starting the inspection to determine if there were any violations during this event. From a response standpoint, NIST did declare an alert. It is one of three levels of emergency response: response, alert, and site area emergency (SAE). Although NIST’s emergency plan includes SAE, it is unlikely to have an event that would result in consequences like that. With the maximum event, the consequences are below the dose limit for a member of the public. So even a worst-case event would still not exceed dose limits for members of the public, which would not drive any protective actions or measures for any of the public off-site. [Update: In its August 2022 Confirmatory Order, the NRC did not impose a civil penalty or issue a cited notice of violation to NIST.]

A. We do licensing and oversight as well as enforcement, if necessary. Organizations with a reactor have to obtain a license from the NRC. They have to demonstrate they can comply with our regulations and submit a license application for review and approval.

A. I’m not aware of specific regulations governing that. The NRC set up the license in such a way that the research reactor operations wouldn’t affect the community beyond the fence line of NIST. Any houses that would have been built after that would have been outside of the fence line.

A. The reactor site is 1,300 feet, contained completely within the NIST site, and that is where doses are calculated, at that 400-meter boundary. Because the impacts at that boundary are well below the public dose limit, there is no need to reevaluate the neighborhood outside that range. [For NRC emergency planning purposes, a 10-20MW research reactor “site” includes a 1,300-foot (400-meter) zone around the reactor.]

A. No. The exposures that are estimated for a worst-case accident, which this was not, are only 10% of the annual dose limit of 100 millirem.

A. Natural phenomena, such as earthquakes, are considered in the safety review required for licensing and in the design of the facility. The NCNR is designed for a worst-case seismic event for this area and also takes into account hurricanes, tornadoes, high winds, etc. In addition to the earthquake, the Fukushima plant was also hit by a tsunami, which should not be a problem for this area. Also, the NIST research reactor is much, much smaller than a nuclear power reactor.

A. We do not look at that. Pets can get treated with radiation, like people.

A. No, that is not a problem. [The annual safe exposure limits take this into account and assume someone could be exposed over their entire lifetime.]

A. In addition to a facility design that includes reactor cooling, special ventilation and a confinement building to limit radiation release to below regulatory limits, several different systems are monitoring what’s going on in the reactor at all times. In this case, the monitors that caused the reactor to shut down were on the ventilation stack and primary cooling system. Other types of monitors look at other characteristics of the reactor. There are multiple systems that can tell a reactor to shut down and put things in a safe state.

In addition to this type of monitoring and automatic actions, there are highly trained operators on duty 24/7 to monitor the reactor. Operators must be licensed by the NRC, and to receive and maintain a license, one must go through a rigorous training program, written exam and operating proficiency exams.

Questions may have been edited for clarity or to ensure factual accuracy.

Created April 14, 2020, Updated March 10, 2023