Tag Archives: nuclear

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Indian Point Fire and Oil Leak

By Sarah Wrenn

At 5:50 PM on May 9, 2015, a fire ignited in one of two main transformers for the Unit 3 Reactor at Indian Point Energy Center. These transformers carry electricity from the main generator to the electrical grid. While the transformer is part of an electrical system external to the nuclear system, the reactor is designed to automatically shut down following a transformer failure. This system functioned as designed and the reactor remains shut down with the ongoing investigation. Concurrently, oil (dielectric fluid) spilled from the damaged transformer into the plant’s discharge canal and some amount was also released into the Hudson River. On May 19, Fred Dacimo, vice president for license renewal at Indian Point and Bill Mohl, president of Entergy Wholesale Commodities, stated the transformer holds more than 24,000 gallons of dielectric fluid. Inspections after the fire revealed 8,300 gallons have been collected or were combusted during the fire. As a result, investigators are working to identify the remaining 16,000 gallons of oil. Based on estimates from the Coast Guard supported by NOAA, up to approximately 3,000 gallons may have gone into the Hudson River.

The graphic located here provides details regarding the event, facility layout and response.

Step 1. Define the Problem

There are a few problems in this event. Certainly, the transformer failure and fire are major problems. The transformer is an integral component to transfer electricity from the power plant to the grid. Without the transformer, production has been halted. In addition, there is an inherent risk of injury with the fire response. The site’s fire brigade was dispatched to respond to the fire and while there were no injuries, there was a potential for injury. In addition, the release of dielectric fluid and fire-retardant foam into the Hudson River is a problem. A moat around the transformer is designed to contain these fluids if released, but evidence shows that some amounts reached the Hudson River.

As shown in the timeline and noted on our problem outline, the transformer failure and fire occurred at 5:50 PM and was officially declared out 2.25 hours later.

As far as anything out of the ordinary or unusual when this event occurred, Unit 3 had just returned to operations after a shutdown on May 7 to repair a leak of clean steam from a pipe on the non-nuclear side of the plant. Also, it was noted that this is the 3rd transformer failure in the past 8 years. This frequency of transformer failures is considered unusual. The Wall Street Journal reported that the transformer that failed earlier this month replaced another transformer that malfunctioned and caught fire in 2007. Another transformer failed in 2010, which had been in operation for four years.

Multiple organizational goals were negatively impacted by this event. As mentioned above, there was a risk of injury related to the fire response. There was also a negative impact to the environment due to the release of dielectric fluid and fire-retardant foam. The negative publicity from the event impacts the organization’s customer service goal. A notification to the NRC of an Unusual Event (the lowest of 4 NRC emergency classifications) is a regulatory impact. For production/schedule, Unit 3 was shutdown May 9 and remains shutdown during the investigation. There was a loss of the transformer which needs to be replaced. Finally, there is labor/time required to address and contain the release, repair the transformer, and investigate the incident.

Step 2. Identify the Causes (Analysis)

Now that we’ve defined the problem in relation to how the organization’s goals were negatively impacted, we want to understand why.

The Safety Goal was impacted due to the potential for injury. The risk of injury exists because of the transformer fire.

 

 

The Regulatory Goal was impacted due to the notification to the NRC. This was because of the Unit 3 shutdown, which also impacts the Production/Schedule Goal. Unit 3 shutdown as this is the designed response to the emergency. This is the designed response because of the loss of the electrical transformer, which also impacts the Property/Equipment Goal. Why was the electrical transformer lost? Because of the transformer fire.

For the other goals impacted, Customer Service was because of the negative publicity which was caused by the containment, repair, investigation time and effort. This time and effort impacts the organization’s Labor/Time Goal. This time and effort was required because of the dielectric fluid and fire-retardant foam release. Why was there a release? Because the fluid and foam were able to access the river.

Why did the fluid and foam access the river?

The fire-retardant foam was introduced because the sprinkler system was ineffective. The transformer is located outside in the transformer yard which is equipped with a sprinkler system. Reports indicate that the fire was originally extinguished by the sprinklers, but then relit. Fire responders introduced fire-retardant foam and water to more aggressively address the fire. Some questions we would ask here include why was the sprinkler system ineffective at completely controlling the fire? Alternatively, is the sprinkler system designed to begin controlling the fire as an immediate response such that the fire brigade has time to respond? If this is the case, then did the sprinkler perform as expected and designed?

The transformer moat is designed to catch fluids and was unable to contain the fluid and the foam. When a containment is unable to hold the amount of fluid that is introduced, this means that either there is a leak in the containment or the amount of fluid introduced is greater than the capacity of the containment. We want to investigate the integrity of the containment and if there are any leak paths that would have allowed fluids to escape the moat. We also want to understand the volume of fluid that was introduced. The moat is capable of holding up to 89,000 gallons of fluid. A transformer contains approximately 24,000 gallons of dielectric fluid. What we don’t know is how much fire-retardant foam was introduced. If this value plus the amount of transformer fluid is greater than the capacity of the moat, then the fluid will overflow and can access the river. If this is the case, we also would want to understand if the moat capacity is sufficient, should it be larger? Also, is the moat designed such that an overflow will result in accessing the discharge canal and is this desired?

Finally, dielectric fluid accessed the river because the fluid was released from the transformer. Questions we would ask here are: Why was the fluid released and why does a transformer contain dielectric fluid? Dielectric fluid is used to cool the transformers. Other cooling methods, such as fans are also in place. The causes of the fluid release and transformer failure is still being investigated, but in addition to determining these causes, we would also ask how are the transformers monitored and maintained? The Wall Street Journal provided a statement from Jerry Nappi, a spokesman for Entergy. Nappi said both of unit 3’s transformers passed extensive electrical inspections in March. Transformers at Indian Point get these intensive inspections every two years. Aspects of the devices also are inspected daily.

Finally, we want to understand why was there a transformer fire. The transformer fire occurred because there was some heat source (ignition source), fuel, and oxygen. We want to investigate what was the heat source – was there a spark, a short in the wiring, a static electricity build up? Also, where did the fuel come from and is it expected to be there? The dielectric fluid is flammable, but are there other fuel sources that exist?

Step 3. Select the Best Solutions (Reduce the Risk)

What can be done? With the investigation ongoing, a lot of facts still need to be gathered to complete the analysis. Once that information is gathered, we want to consider what is possible to reduce the risk of having this type of event occur in the future. We would want to evaluate what can be done to address the transformer, implementing solutions to better maintain, monitor, and/or operate it. Focusing on solutions that will minimize the risk of failure and fire. However, if a failure does occur, we want to consider solutions so that the failure and fire does not result in a release. Further, we can consider the immediate response; do these steps adequately contain the release? Identifying specific solutions to the causes identified will provide reductions to the risk of future similar events.

Resources:

This Cause Map was built using publicly available information from the following resources.

De Avila, Joseph “New York State Calls for Tougher Inspections at Indian Point” http://www.wsj.com/articles/nuclear-regulatory-commission-opens-probe-at-indian-point-1432054561 Published 5/20/2015. Accessed 5/20/2015

“Entergy’s Response to the Transformer Failure at Indian Point Energy Center” http://www.safesecurevital.com/transformer_update/ Accessed 5/19/2015

“Entergy Plans Maintenance Shutdown of Indian Point Unit 3” http://www.safesecurevital.com/entergy-plans-maintenance-shutdown-of-indian-point-unit-3/ Published 5/7/2015. Accessed 5/19/2015

“Indian Point Unit 3 Safely Shutdown Following Failure of Transformer” http://www.safesecurevital.com/indian-point-unit-3-safely-shutdown-following-failure-of-transformer/ Published 5/9/2015. Accessed 5/19/2015

“Entergy Leading Response to Monitor and Mitigate Potential Impacts to Hudson River Following Transformer Failure at Indian Point Energy Center” http://www.safesecurevital.com/entergy-leading-response-to-monitor-and-mitigate-potential-impacts-to-hudson-river-following-transformer-failure-at-indian-point-energy-center/ Published 5/13/2015. Accessed 5/19/2015

“Entergy Continues Investigation of Failed Transformer, Spilled Dielectric Fluid at Indian Point Energy Center” http://www.safesecurevital.com/entergy-continues-investigation-of-failed-transformer-spilled-dielectric-fluid-at-indian-point-energy-center/ Published 5/15/2015. Accessed 5/19/2015

McGeehan, Patrick “Fire Prompts Renewed Calls to Close the Indian Point Nuclear Plant” http://www.nytimes.com/2015/05/13/nyregion/fire-prompts-renewed-calls-to-close-the-indian-point-nuclear-plant.html?_r=0 Published 5/12/2015. Accessed 5/19/2015

Screnci, Diane. “Indian Point Transformer Fire” http://public-blog.nrc-gateway.gov/2015/05/12/indian-point-transformer-fire/comment-page-2/#comment-1568543 Accessed 5/19/2015

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Working Conditions Raise Concerns at Fukushima Daiichi

By ThinkReliability Staff

The nearly 7,000 workers toiling to decommission the reactors at Fukushima Daiichi after they were destroyed by the earthquake and tsunami on March 11, 2011 face a daunting task (described in our previous blog). Recent events have led to questions about the working conditions and safety of these workers.

On January 16, 2015, the local labor bureau instructed the utility that owns the plants to reduce industrial accidents. (The site experienced 23 accidents in fiscal year 2013 and 55 so far this fiscal year.) Three days later, on January 19, a worker fell into a water storage tank and was taken to the hospital. He died the next day, as did a worker at Fukushima Daini when his head got caught in machinery. (Fukushima Daini is nearby and was less impacted by the 2011 event. It is now being used as a staging site for the decommissioning work at Fukushima Daiichi.)

Although looking at all industrial accidents will provide the most effective solutions, often digging into just one in greater detail will provide a starting point for site improvements. In this case, we will look at the January 19 fall at Fukushima Daiichi to identify some of the challenges facing the site that may be leading to worker injuries and fatalities.

A Cause Map, or visual form of root cause analysis, is begun by determining the organizational impacts as a result of an incident. In this case the worker fall impacted the safety goal due to the death of the worker. The environmental goal was not impacted. (Although the radiation levels at the site still require extensive personal protective equipment, the incident was not radiation-related.) Workers on site have noted difficult working conditions, which are thought to be at least partially responsible for the rise in incidents, as are the huge number of workers at the site (itself an impact to the labor/time goal). Lastly, local organizations have raised regulatory concerns due to the high number of incidents at the site.

An analysis of the issues begins with one impacted goal. In this case, the worker death resulted from a fall into a ten-meter empty tank. The worker was apparently not found immediately (though specific timeline details and whether or not that impacted the worker’s outcome have not been released) because it appears he was working alone, likely due to the massive manpower needs at the site. Additionally, the face masks worn by all workers (due to the high radiation levels still present) limit visibility.

The worker was checking for leaks at the top of the tank, which is being used to store water used to cool the reactors at the site. There is a general concern about lack of knowledge of workers (many of whom have been hired recently with little or no experience doing the types of tasks they are now performing), though again, it’s unclear whether this was applicable in this case. Of more concern is the ineffective safety equipment – apparently the worker did not securely fasten his safety harness.

The reasons for this, and the worker falling in the first place, are likely due to worker fatigue or lack of concentration. Workers at the site face difficult conditions doing difficult work all day (or night) long, and have to travel far afterwards, as the surrounding area is still evacuated. Reports of mental health issues and fatigue in these workers has led to the opening of a new site providing meals and rest for these workers.

These factors are likely contributing to the increase in accidents, as is the number of workers at the site, which doubled from December 2013 to December 2014. Local organizations are still calling for action to reduce these actions. “It’s not just the number of accidents that has been on the rise. It’s the serious cases, including deaths and serious injuries that have risen, so we asked Tokyo Electric to improve the situation,” says Katsuyoshi Ito, a local labor standards inspector.

In addition to improving working conditions, the site is implementing improved worker training – and looking at discharging wastewater instead of storing it, which would reduce the pieces of equipment required to be monitored and maintained. Improvements must be made, because decades of work remains before work at the site will be completed.

Click here to sign up for our FREE webinar “Root Cause Analysis Case Study: Fukushima Daiichi” at 2:00 pm EDT on March 12 to learn more about how the earthquake and tsunami on March 11, 2011 impacted the plant.

Root Cause Analysis - Incident Investigation

Kitty Litter Cause of Radiological Leak?

By ThinkReliability Staff

The rupture of a container filled with nuclear waste from Department of Energy (DOE) sites that resulted in the  radiological contamination of 21 workers appears to have resulted from a heat-producing reaction, possibly between the nuclear waste and the kitty litter used to stabilize the waste.

DOE photo of damaged container

Yes, you read that correctly. The same stuff you use for Fluffy’s “business” is also used to stabilize nuclear waste.  However, the kitty litter typically used is clay.  One of the sites that provides waste to the Waste Isolation Pilot Plant, where the release occurred, changed from clay kitty litter to organic kitty litter, which is made of plant material.  Although the reaction that resulted in the container’s rupture has not yet been determined, it is possible that it was due to the change in litter.

We can look at this incident in a Cause Map, or visual root cause analysis, to lay out both the effects and causes.  In this case, the effects were significant.  Twenty-one workers were found to have internal radiological contamination, impacting the safety goal.  A radiological release off-site impacted the environmental goal.  The waste repository has been shut down and is not accepting shipments, impacting both the customer service and production goals.  The release requires the investigation of a formal Accident Investigation Board, impacting the regulatory and labor goal.  Lastly, the damage to the container is an impact to the property goal.

The release was caused by the rupture of a container that stored radiological waste, including americium and plutonium.  The release was able to leave the underground storage facility due to a leak path in the ventilation system, which was by design because the ventilation system was not designed for containment because the safety analysis assumed that a release within the storage facility would result from a roof panel fall and was adequately prevented.

The rupture appears to have resulted from a heat-producing reaction. The constituents of that reaction have not yet been determined, but the change from clay to organic kitty litter has been identified as a possible cause.  (A possible cause indicates a cause for which evidence is not yet available.)  More research is being done to determine the actual reaction.  This will also allow a determination of which other waste containers may be at risk for rupture.

A solution that has already been implemented is to seal the leaks in the ventilation system with foam to reduce the risk of leak-by.  Other solutions that have been suggested are to add an additional heavy-duty containment around the affected casks, reclassify the ventilation system as containment, and perform an independent review of the safety analysis of the site.  Once appropriate solutions are determined and implemented, it’s hope the site will be able to reopen.

To view the Outline and Cause Map, please click “Download PDF” above.

Root Cause Analysis - Incident Investigation

Cleaning up Fukushima Daiichi

By ThinkReliability Staff

The nuclear power plants at Fukushima Daiichi were damaged beyond repair during the earthquake and subsequent tsunami on March 11, 2011.  (Read more about the issues that resulted in the damage in our previous blog.)  Release of radioactivity as a result of these issues is ongoing and will end only after the plants have been decommissioned.  Decommissioning the nuclear power plants at Fukushima Daiichi will be a difficult and time consuming process.  Not only the process but the equipment being used are essentially being developed on the fly for this particular purpose.

Past nuclear incidents offer no help.  The reactor at Chernobyl which exploded was entombed in concrete, not dismantled as is the plan for the reactors at Fukushima Daiichi.  The reactor at Three Mile Island which overheated was defueled, but the pressure vessel and buildings in that case were not damaged, meaning the cleanup was of an entirely different magnitude.  Lake Barrett, the site director during the decommissioning process at Three Mile Island and a consultant on the Fukushima Daiichi cleanup, says that nothing like Fukushima has ever happened before.

An additional challenge?  Though the reactors have been shut down since March 2011, the radiation levels remain too high for human access (and will be for some time).  All access, including for inspection, has to be done by robot.

The decommissioning process involves 5 basic steps (though the completion of them will take decades).

First, an inspection of the site must be completed using robots.  These inspection robots aren’t your run-of-the-mill Roombas.  Because of the steel and concrete structures involved with nuclear power, wireless communication is difficult.  One type of robot used to survey got stuck in reactor 2 after its cable was entangled and damaged.   The next generation of survey robots unspools cable, takes up slack when it changes direction and plugs itself in for a recharge.  This last one is particularly important: not only can humans not access the reactor building, they can’t handle the robots after they’ve been in there.  The new robots should be able to perform about 100 missions before component failure, pretty impressive for access in a site where the hourly radiation dose can be the same as a cleanup worker’s annual limit (54 millisieverts an hour).

Second, internal surfaces will be decontaminated.  This requires even more robots, with different specialties.  One type of robot will clear a path for another type, which will be outfitted with water and dry ice, to be blasted at surfaces in order to remove the outer level, and the radiation with it.  The robots will them vacuum up and remove the radioactive sludge from the building.  The resulting sludge will have to be stored, though the plan for the storage is not yet clear.

Third, spent fuel rods will be removed, further reducing the radiation within the buildings.  A shielded cask is lowered with a crane-like machine, which then packs the fuel assemblies into the cask.  The cask is then removed and transported to a common pool for storage.  (The fuel assemblies must remain in water due to the decay heat still being produced.)

Fourth, radioactive water must be contained.  An ongoing issue with the Fukushima Daiichi reactors is the flow of groundwater through contaminated buildings.  (Read more about the issues with water contamination in a previous blog.)  First, the flow of groundwater must be stopped.  The current plan is to freeze soil to create a wall of ice and put in a series of pumps to reroute the water.    Then, the leaks in the pressure vessels must be found and fixed.  If the leaks can’t be fixed, the entire system may be blocked off with concrete.

Another challenge is what to do with the radioactive water being collected.  So far, over 1,000 tanks have been installed.  But these tanks have had problems with leaks.    Public sentiment is against releasing the water into the ocean, though the contamination is low and of a form that poses a “negligible threat”.  The alternative would be using evaporation to dispose of the water over years, as was done after Three Mile Island.

Finally, the remaining damaged nuclear material must be removed.  More mapping is required, to determine the location of the melted fuel.  This fuel must then be broken up using long drills capable of withstanding the radiation that will still be present.  The debris will then be taken into more shielded casks to a storage facility, the location of which is yet to be determined.  The operator of the plant estimates this process will take at least 20 years.

To view the Process Map laid out visually, please click “Download PDF” above.  Or click here to read more.

Root Cause Analysis - Incident Investigation

Contaminated Water Issues Remain at Fukushima

by ThinkReliability Staff

High levels of contaminated water leaving the highly damaged reactors at the Fukushima Daiichi nuclear power plant in Japan are creating issues for the personnel on site, who are working frantically to keep the reactor safe and working towards decommissioning and closing down the site.  Additionally, there is continued concern for the ongoing safety of the site, as the high volume of water could potentially threaten the safety of the reactors.

We can look at these issues in a Cause Map, or visual root cause analysis.  With a Cause Map, the first step is to determine how the issue impacts the organization’s goals.  In this case, we can consider the goals from the perspective of the utility company that owns the power plant.  There is an impact to the safety goal because of the potential risk for another accident, according to the Chairman of the Nuclear Regulatory Authority.  The leakage of contaminated water is an impact to the environmental goal.  There is concern about the lack of a comprehensive plan by the utility, which can be considered an impact to the customer service goal.  The massive construction efforts required to install tanks to store the water are an impact to the property goal and the efforts by the workers to control the flow are an impact to the labor goal.

Once the impacts to the goals have been determined, the next step is asking “Why” questions to determine the cause-and-effect relationships that led to the incident.  In this case, the issues resulting in the high rate of contaminated water needing to be stored are that high rates of water are entering the reactor, becoming contaminated due to the damage inside the buildings from the earthquake and tsunami on March 11, 2011, and the water has to be removed from the building.

The water is entering the buildings because the plant is in the groundwater flow path from the mountains to the ocean and there is insufficient protection to prevent the water accessing the plant.   Severe cracking in the reactor buildings from the earthquake/tsunami are unable to be repaired due to the high residual levels of radioactivity.  The utility rejected plans to build a wall to protect the reactor.  It is believed this is because the utility had planned to dump the water into the ocean.   Additionally, according to the Japan Atomic Energy Commission, the issues from the water weren’t something that were thought of, as the focus was on the nuclear issues.  All involved in the cleanup, including the utility, have had their hands full, so it’s likely something as benign-seeming as water just wasn’t on the list of immediate concerns.

The contaminated water must be pumped out of the building to avoid swamping the cooling systems, which are still needed to remove decay heat that continues to be produced even after the reactors are shut down.  It appears that the original plan was to filter the water and dump it into the ocean, but even after filtering, a high level (about one hundred times the level released from a healthy plant) of tritium would remain.  Public outcry has ended the possibility of being able to dispose of the water that way.  Wastewater pits originally built for this purpose were found last month to be leaking, necessitating the installation of hundreds of tanks for water storage.

For now, the utility workers continue to install tanks to hold the radioactive water.  The task is so overwhelming, it’s not clear if there are any other plans to try and slow the tide of contaminated water.  However, outside experts are attempting to provide assistance.  The International Atomic Energy Agency completed its initial review of the decommissioning plans last month.  The final team report is expected later this month.

To view the Outline and Cause Map, please click “Download PDF” above.  Or click here to read more.

Root Cause Analysis - Incident Investigation

SL-1 Explosion-The Only Fatal Reactor Accident in the US

By ThinkReliability Staff

The only fatal reactor accident in the United States occurred on January 3, 1961, when an Army prototype known as SL-1 (for stationary, low power reactor, unit 1) exploded, killing the 3 operators who were present.  We’ll use the SL-1 tragedy as an example of how the Cause Mapping process can be applied to a specific incident.  A thorough root cause analysis built as a Cause Map can capture all of the causes in a simple, intuitive format that fits on one page.

The SL-1 tragedy killed the three operators present, which is an impact to the safety goal.  Another goal is that there be no damage to the vessel. In the case of SL-1, the  vessel sustained extensive damage.

The loss of life and vessel damage were both caused by the reactor exploding.  The reactor exploded because it went prompt critical (an uncontrollable, exponentially increasing fission reaction).  The reactor went prompt critical because withdrawal of the central rod can cause prompt criticality and because the rod was rapidly, manually lifted 26.4″ out of the core.

Withdrawal of the central rod can cause prompt criticality due to a lack of shutdown margin in the core, and inadequate safety criteria.

Because most of the evidence was so effectively destroyed, nobody really knows why the control rod was lifted out of the core.  There are two theories (disregarding the bizarre and improbable murder/suicide theory): 1) the control rod got stuck while being lifted to be attached to the drive mechanism, and, as the operator was exerting greater force on it, suddenly came free, resulting in a lift far greater than intended, or that an rod drop testing/exercising was performed improperly.

The control rod may have become stuck and came free while being attached because it was required to be lifted 4″ out of the core and because control rods had been sticking.  The control rods had been sticking for one or more of the following reasons: 1) reduced clearances due to radiation damage (which can cause structural material to swell), 2) the passage was blocked due to loss of poison strips in the channel, caused by poor design and inadequate testing, or 3) lifting equipment not working properly due to inadequate lifting capacity of the lifting equipment.

It’s also possible that an exercising/testing was potentially improperly performed.  This could have occurred because the operators chose to exercise/test the rods, attempting to ensure that they would perform properly, and because they didn’t realize what would happen. This is because of inadequate training and inadequate work instructions.  The testing was also potentially done improperly due to inadequate work instructions.

On a positive note, the SL-1 incident did initiate some positive changes in the nuclear industry.  Most notably, reactor design has improved and incorporated a “one-rod stuck” criteria which specifies that a reactor can NOT go critical by the removal of any one control rod.  Additionally, procedures and training have gotten more intense and more formal, and planning for emergencies has increased.

Root Cause Analysis - Incident Investigation

Several Incidents at CA Nuclear Plant Raise Concerns

By Kim Smiley

Within a week, three separate incidents occurred at the San Onofre Nuclear Generating Station, located near heavily populated areas, raising new concerns about the safety of the nuclear power plant.

This issue can be investigated by building a Cause Map, an intuitive, visual root cause analysis.  The first step in building a Cause Map is to determine what goals are impacted by the issue being considered.  In this case, the main goal being considered is safety.  If the Cause Map was being built from the perspective of the power plant company, then the production and schedule impacts would also need to be considered, but in this example we will focus on the safety impacts.

The safety goal is impacted because some people are concerned about the safety of the power plant because it is near heavily populated areas and three separate incidents occurred within days of each other.  The three incidents in question were the release of a small amount of radiation, discovery of unexpected amounts of wear on steam generator tubes, and the potential contamination of a worker.

A small amount of radiation was released because a steam generator tube, which carries radioactive water, was leaking.  Luckily, the leak was small and the plant was quickly shut down after the leak was discovered so no significant amounts of radiation were released.  A second reactor unit is currently shut down for maintenance and inspection of the steam generator tubes found significantly more wear than expected on some of the tubes.  The wear was unexpected because the tubes have only been in service for 22 months and two tubes had 30% wall thinning, 69 tubes had 20% wall thinning and 800 had 10% wall thinning.  The situation is being investigated, but neither the cause of the wear nor the best course of action has not yet been determined.  The final incident was the potential contamination of a worker because he fell into a reactor pool.  According to media reports, the worker was trying to retrieve a flash light and lost his footing.

To view a high level Cause Map of this incident, click “Download PDF” above.  The Cause Map can be expanded as more information comes available so that it can document and illustrate as much detail as needed to evaluate the issues.

As it stands, both the reactor units with the steam generator tubes are shut down.  The unit that experienced the leak is shutdown pending investigation and any necessary repairs.  The second unit that had the unexpected wall thinning in the steam generator tubes is in a planned shutdown of several months while it is refueled and upgraded.  The plants will be brought back online once it’s determined safe to do so.

Root Cause Analysis - Incident Investigation

Radioactive Release in the 1960s due to Inadvertent Dropping of Nuclear Weapons

By ThinkReliability Staff

In the history of nuclear weapons in the U.S., two accidents (or inadvertent drops) of nuclear weapons have resulted in widespread dispersal of nuclear materials.  These two incidents occurred two years apart, within a week.  The incidents had many similarities: in both cases, a B-52 bomber carrying nuclear weapons was damaged in air during an airborne alert mission and released nuclear weapons, which released radioactive material over a large area.  In both cases, there were significant impacts to the safety, environmental, customer service, property and labor goals.

Palomares: On January 17, 1966, a B-52 and KC-135 crashed during refueling above Palomares, Spain.  The KC 135 exploded, killing the entire crew of four.   The B-52 broke up mid-air, killing three crew members (four more were able to eject) and releasing four nuclear weapons.  Two of the weapons’ parachutes failed, and the weapons were destroyed, releasing radioactive material causing extensive cleanup of the 1,400 contaminated tons of soil and debris.  (Additionally, one of the intact bombs fell into the ocean and was not recovered for three months.) This was the third refuel of the mission and it’s unclear what exactly went wrong, though due to the close proximity required, mid-air refueling is extremely risky.

Thule: A fire began in a B-52 when flammable cushions were stuffed under a seat, covering the heat duct.  Hot air from the engine manifold was redirected into the cabin in an attempt to warm it up, which ignited the cushions.  The crew of the B-52 was unable to extinguish the fire and the pilot lost instrument visibility.  The generators failed (for reasons that aren’t clear), cutting all engine power.  The crew bailed, the plane crashed, and the two weapons were destroyed along with the plane, again releasing radioactive material that led to a four-month cleanup mission.

The causes of these two incidents have one thing in common – both resulted from planes carrying nuclear weapons as part of an airborne alert mission.  Although many safeguards were taken due to the high risk of the missions, extremely serious impacts still resulted.  Thus the decision was made to cancel airborne alert missions.  When the risk is too high, sometimes the only solution is to end the situation resulting in the risk.

We can look at these two incidents together in a Cause Map, or visual root cause analysis.  To view the Outlines,  Timeline and Cause Maps in a three-page downloadable PDF, please click “Download PDF” above.  Or click here to read more.

Root Cause Analysis - Incident Investigation

Explosion at Nuclear Waste Site Kills One

By Kim Smiley

An explosion at a nuclear waste processing site in France killed one and injured four workers on September 12, 2011.  The investigation is still ongoing, but it is still possible to create a Cause Map, a visual root cause analysis, that contains all known information on the incident.  As more information becomes available, the Cause Map can easily be expanded to incorporate all relevant details.  One advantage of Cause Mapping is that it can be used to document all information at each step of the investigation process in an intuitive way, in a single location.

When the word “nuclear” is involved emotions and fears can run high, especially following the recent events at the Fukushima nuclear plant in Japan.  This incident is a good example where providing clear information can help calm the situation.  The explosion in France happened when a furnace used to burn nuclear waste failed.  The cause of the explosion itself isn’t known at this time, but there is some relevant background information available that helps explains the potential ramifications of the explosion.

The key to understanding the impact of this incident is the type of nuclear waste that was being burned.  According to statements by the French government, the furnace involved was only used to burn waste with very low level contamination.  It burned things such as gloves and overalls as well as metal waste like tools and pumps.  No objects that were part of a reactor were treated in the furnace.  There are also no reactors at the site that could be potentially damaged by explosion.

There was no radiation leakage detected and the potential for large amounts of released radiation wasn’t there based on the type of material being processed.  It was a horrible accident that resulted in a death and severe injuries, but there was no risk to public health.

How France views nuclear power is also a bit of background worth knowing.  France is the world’s most nuclear power dependent country.  Fifty-eight reactors generate nearly three fourths of France’s power.  France is also a major exporter of nuclear technology.  The public relations issues associated with a nuclear disaster in France would be very complicated.

Once the investigation into this incident is complete, solutions can complete be determined and implemented to help prevent any future occurrences.

Root Cause Analysis - Incident Investigation

Nuclear Waste Stalemate in US

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By Kim Smiley

America’s 104 commercial nuclear reactors produce about 2,000 metric tons of spent nuclear fuel each year.  The United States currently has no long term solution in place to deal with spent nuclear fuel.  The end result of this stalemate is that that there is more than 75,000 tons of spent nuclear fuel at 122 temporary sites in 39 states with nowhere to go.

Much of the nation’s spent fuel is currently stored in pools near operating nuclear reactors or near sites where reactors once were. Recent events at the Fukushima nuclear plant in Japan have sparked discussion about the potential safety risk of having so much fuel stored near operating reactors creating a situation where one single event can trigger a larger release of radiation.  To make things more complicated, storage pools at US plants are more heavily loaded than the ones at the Fukushima reactors.  Additionally, the pools will reach capacity at some point in the not so distant future and the fuel will have to be moved if the US plans to continue operating nuclear reactors.

How did we get in this situation?  The problem of no long term solution for spent nuclear fuel can be analyzed by building a Cause Map.  A Cause Map is a visual root cause analysis that lays out the causes that contribute to a problem in an intuitive, easy to understand format. Click on “Download PDF” above to view a high level Cause Map of this issue.

Looking at the Cause Map, it’s apparent one of the causes of this problem is that the plan for the Yucca Mountain Nuclear Waste Repository was canceled without an alternative plan being created.  Yucca Mountain Repository was planned to be a deep geological repository where nuclear waste would be stored indefinitely, shielded and packaged to prevent any release of radiation.  The Yucca Mountain Repository was canceled in 2009 for a number of reasons, some technological and some political.  Environmentalists and residents near the planned site were very vocal about their opposition to the selection of Yucca Mountain site for the nation’s repository.

A Blue Ribbon Commission of experts appointed by President Obama recently presented their recommendations of how to approach this problem.  Their proposal was to develop one or more sites where spent reactor fuel could be stored in above ground steel and concrete structures.  These structures could contain fuel for decades, allowing time for a more permanent solution to be developed.  These structures would not require any cooling beyond simple circulation of air and they could be stored at locations deemed safe, with the lowest risk of earthquakes and other disasters.  Hopefully the recommendations by the commission are the first step to solving this problem and developing a safe long term storage solution to the nation’s nuclear waste.