Tag Archives: safety

Root Cause Analysis - Incident Investigation

10,000 Pound Buoy Falls on Workers

By Kim Smiley

On December 10, 2014, a buoy that weighs close to 10,000 pounds fell onto workers at an inactive ship maintenance facility in Pearl Harbor. Two workers were killed and two others sustained injuries. While an object this large is an extreme example of the dangers of dropped objects, worker injuries and deaths from falling objects of all sizes is a significant safety concern. A US census report of fatal occupation injuries states that 245 workers were killed after being struck by falling objects in 2013 alone.

The case of the dropped buoy can be built into a Cause Map, a visual root cause analysis, to better understand what happened. Understanding the details of an accident is necessary to ensure that a wide range of solutions is considered and that any solutions implemented will be effective at preventing future incidents.

The investigation into the falling buoy is still underway so some information is not yet available, but it can easily be incorporated into the Cause Map once it is known. Any causes that need more information or evidence can be noted with a question mark to show that there is still an open question.

Exactly what caused the buoy to drop hasn’t been released yet, but it is known that the safety lines attached to the buoy failed. Both of these issues need to be investigated to ensure that solutions can be implemented to prevent further tragedies.

Additionally, there are open questions about why people were working under the path of the lift. The workers were wearing hard hats, but this is obviously inadequate protection against a 10,000 buoy. The contractors were working to strengthen mooring lines at the time of the accident, but no one should be where they could be crushed if such a large object was dropped, as it was in this case. As stated by Jeff Romeo, the Occupational Safety and Health Administration (OSHA) Honolulu area director, “We’re still looking at the facts to try to determine the exact locations of where these employees were located. If in fact, they were working directly underneath the load, then that would be an alarming situation.”

The OSHA investigation is currently underway and is expected to take four to six months. Additionally, the Navy is launching a Safety Investigation Board to review the accident with findings expected to be released by February. Once the investigation is complete, work processes will need to be reviewed to see what changes need to be made to prevent any future injuries from falling objects.

To view an initial Cause Map of this incident, click on “Download PDF” above.

Root Cause Analysis - Incident Investigation

Chemical Release Kills Four Workers at Texas Pesticide Plant

By ThinkReliability Staff

In the early morning hours of November 15, 2014, a release of methyl mercaptan resulted in the deaths of four employees at a plant in Texas that manufactures pesticides. The investigation into the source of the leak is still ongoing, though persistent maintenance problems had been reported in the plant, which was shut down five days prior to the incident.

Even though the investigation has not been completed, there are some lessons learned that can be applied to this facility, and other facilities that handle chemicals, immediately.

Even “safer” chemicals are dangerous when not treated properly. The chemical released – methyl mercaptan – is stored as a safer alternative to methyl isocyanate (which was the chemical released in the Bhopal disaster). Although it’s “safer” than its alternatives, it is still lethal at concentrations above 150 parts per million. The company has stated that 23,000 pounds were released – in a room where complaints were made about insufficient ventilation. The workers were unable to escape – likely because they were quickly incapacitated by the levels of methyl mercaptan and did not have the necessary equipment to get out. (Only two air masks and oxygen tanks were found in the area where the employees were.)

A fast response is necessary for employee safety. Records show that 911 was not called for an hour after the employees were trapped. (One of the victims called his wife an hour prior to indicate there was an issue and he was attempting rescue.) The emergency industrial response group, which is trained to provide response in these sort of situations, was never called by the plant. Medical personnel could not access the employees because they were not trained in protective gear. Firefighters who responded did not have enough air to travel through the entire facility and did not have enough information on the layout to know where to go. It’s unclear whether a quicker response could have saved lives.

Providing timely, accurate information is necessary for public safety. The best way to determine the impact on the public is to measure the concentration of released chemicals at the fenceline (known as fenceline monitoring). Air monitoring was not performed for more than four hours after the release. Companies are not required to provide fenceline monitoring, although an Environmental Protection Agency (EPA) rule requiring monitoring systems for refineries is under review. (This rule would not have impacted this plant as it produced pesticides.) Until that monitoring, the only information available to the public was information provided by the company (which did not release until days later the amount of chemical released.) In Texas, companies are required to disclose the presence of chemicals, but not the amount. A reverse 911 system was used to inform residents that an odor would be present, but did not discuss the risks.

What can you do? Ensure that all chemicals at your facility are known and stored carefully. Develop a response plan that ensures that your employees can get out safely, that responders can get in safely (and are apprised of risks they may face), and that the public has the necessary information to keep them safe. Make sure these plans are trained on and posted readily. Depending on the risk of public impact from your business, involving emergency responders and the public in your drills may be desired.

To see a high level Cause Map of this incident, click on “Download PDF” above.

Root Cause Analysis - Incident Investigation

Software Error Causes 911 Outage

By Kim Smiley

On April 9, 2014, more than 6,000 calls to 911 went unanswered.  The problem was spread across seven states and went on for hours.  Calling 911 is one of those things that every child is taught and every person hopes they will never need to do –  and having emergency calls go unanswered has the potential to turn into a nightmare.

The Federal Communications Commission (FCC) investigated this 911 outage and has released a study detailing what went wrong on that day in April.  The short answer is that a software error led to the unanswered calls, but there is nearly always more to the story than a single “root cause”.  A Cause Map, an intuitive format for performing a root cause analysis, can be used to better understand this issue by visually laying out the causes (plural) that led to the outage.

There are three steps in the Cause Mapping process. The first is to define an issue by completing an Outline that documents the basic background information and how the problem impacts the overall goals.  Most incidents impact more than one goal and this issue is no exception, but for simplicity let’s focus on the safety goal.  The safety goal was impacted because there was the potential for deaths and injuries.  Once the Outline is completed (including the impacts to the goals), the Cause Map is built by asking “why” questions.

The second step of the Cause Mapping process is to analyze the problem by building the Cause Map.  Starting with the impacted safety goal – “why” was there the potential for deaths and injuries?  This occurred because more than 6,000 911 calls were not answered.   An automated system was designed to answer the calls and it wouldn’t accept new calls for hours.  There was a bug in the automated system’s software AND the issue wasn’t identified for a significant period of time.  The error occurred because the software used a counter with a pre-set limit to assign calls a tracking number.  The counter hit the limit and couldn’t assign a tracking number so it quit accepting new calls.

The delay in identification of the problem is also important to identify in the investigation because the problem would have been much less severe if it had been found and corrected more quickly.  Any 911 outage is a problem, but one that lasts 30 minutes is less alarming than one that plays out over 8hours.  In this example, the system identified the issue and issued alerts, but categorized them as “low level” so they were never flagged for human review.

The final step in the Cause Mapping process is to develop and implement solutions to reduce the risk of the problem recurring.  In order to fix the issues with the software, the pre-set limit on the timer has been increased and will periodically be checked to ensure that the max isn’t hit again.  Additionally, to help improve how quickly a problem is identified, an alert has been added to notify operators when the number of successful calls falls below a certain percentage.

New issues will likely continue to crop up as emergency systems move toward internet-powered infrastructure, but hopefully the systems will become more robust as lessons are learned and solutions are implemented.  I imagine there aren’t many experiences more frightening than frantically calling 911 for help and having no one answer.

To view a high level Cause Map of this issue, including a completed Outline, click on “Download PDF” above.

Root Cause Analysis - Incident Investigation

Two Firefighters Killed by Rogue Welding

By ThinkReliability  Staff

On March 26, 2014, two firefighters were killed when trapped in a basement by a quickly spreading, very dangerous fire in Boston, Massachusetts. These firefighters appear to have been the first to succumb to injuries directly caused by fire while on the job in 2014. The company that was found responsible for starting the fire has been fined by OSHA for failure to follow safety procedures. Says Brenda Gordon, Occupational Safety and Health Administration (OSHA)’s director for Boston and southeastern Massachusetts, “This company’s failure to implement these required, common-sense safeguards put its own employees at risk and resulted in a needless, tragic fire.”

Every incident that results in a fatality should be carefully investigated. Investigations are used not only for liability and regulatory reasons, but also to develop solutions to reduce the risk of similar fatalities happening in the future. Investigating an incident such as this in a Cause Map, or visual root cause analysis, allows for better solutions by determining all the cause-and-effect relationships that led to the issue.

First it’s important to define how goals were impacted in order to define the scope of the problem. In this case, two firefighters were killed, which impacts the safety goal. In addition, the spread of the fire, damage of nearby buildings and associated civil lawsuits are also impacts to the goals. The OSHA fine of $58,000 for 10 violations of workplace safety regulations is an impact to the regulatory goal. The response to the fire, as well as the multiple investigations, are impacts to the labor/time goal.

Beginning with an impacted goal and asking “Why” questions develops cause-and-effect relationships that explain how the incident occurred. In this case, the firefighters perished when they were trapped by fire. The firefighters were in the basement of a residential building to rescue occupants from a fire, and the fire was so hot and dangerous that the firefighters could not exit, and other firefighters were unable to come to their rescue. Extremely windy conditions spread the fire caused by a welding spark that struck a nearby wood shed.   OSHA investigators note that the company performing the welding did not follow safety precautions (including having a fire watcher and moving welding away from flammable objects) that would have reduced the risk for fire. They cited the lack of an effective fire prevention/ protection program and a lack of training in workplace and fire safety. View the Cause Map by clicking “Download PDF” above.

Ideally the fine levied by OSHA will encourage the company involved to increase its methods of fire protection, not only to protect its own workers, but also to protect the public. In addition, the Boston Fire Department is conducting an internal review to improve firefighter safety. Says Steve MacDonald, spokesman, “What they’re doing is looking at policies and procedures. They’re reviewing everything, reviewing weather, radio communications, anything and everything having to do with the fire.”

On July 5th, another firefighter died after being trapped in a building while looking for occupants during a fire in Brooklyn, New York. On July 9th, a firefighter in Houston, Texas was killed of smoke inhalation inside a burning building. A firefighter died in a building collapse due to fire in New Carlisle, Indiana on August 5, 2014, making a total of 5 firefighters who have died as a direct result of smoke/fire injuries while on the call of duty so far in 2014. In 2013, a total of 30 firefighters were killed on the job, most as the result of the Yarnell Hill fire in Arizona.

Root Cause Analysis - Incident Investigation

Can Airline Seats Get Even Smaller?

By Kim Smiley

Was the experience the last time you flew wonderful?  Did you enjoy all the luxurious amenities like ample elbow room, stretching out your legs, and turning around in the bathroom?  Me neither.  Comfort certainly hasn’t been the top priority as airlines have shrunk seats to cram more passengers onboard, but a new patent application by Airbus really takes things to a whole new level.

They say that a picture is worth a thousand words and I think that is particularly true in this case.  This is a diagram of a patent application for a proposed seat design –

 

I’m not sure about the rest of you, but my backside is sore just thinking about an airplane seat that bears such a strong resemble to a bicycle.

I attempted to build a Cause Map, a visual root cause analysis, in order to better understand how such a design could be proposed because I frankly find it mind-boggling.  The basic idea is that airlines would like to maximize profits and that putting more people on each flight allows more tickets to be sold resulting in more money made.  The average airline seat width has already decreased to about 17 inches from the 18 inches typical for a long-haul airplane seat in the 1970s and 1980s.  Compounding the impact on passengers is the fact that the average passenger has increased during that same time frame.  In general larger bodies are being put in smaller seats, not a recipe for a comfort.

I’m still having a hard time understanding how the correct answer to increasing airline profits is making seats even smaller.  I have to believe that passengers will balk at some point.  At some level of discomfort, a cheap ticket just won’t be cheap enough for me to be willing to endure a truly awful flight.  Even with electronic distractions and snacks, there has to be a point where people would just say no.

There also has to be a number of safety concerns that arise when the size of airplane seats is dramatically decreased.  Survivability in a crash is greatly influenced by seat design because airplane seats are designed to absorb energy and provide head injury protection during an accident.

Just to be clear, there is no plan to actually use this seat design anytime in the near future.  This is just a patent application.  As Airbus spokeswoman, Mary Anne Greczyn said, “Many, if not most, of these concepts will never be developed, but in case the future of commercial aviation makes one of our patents relevant, our work is protected. Right now these patent filings are simply conceptual.” But somebody somewhere still thought this was a good enough idea that it should be patented…just in case.

Root Cause Analysis - Incident Investigation

Children Served Bleach from Reused Milk Jug

By ThinkReliability Staff

For morning snack on September 11, 2014, a substitute teacher’s aide was getting ready to pour water for snack on her first day on the job. Unfortunately, what she poured from a reused plastic milk container was actually a beach solution used for cleaning. The mistake was realized quickly, but not before 28 children and 2 adults ingested some of the bleach. Luckily the concentration was low enough that there were no injuries, although all who ingested the solution were seen at a local hospital.

The substitute teacher’s aide was fired and the school reopened the next day, though the New Jersey Department of Children and Families will be investigating. Clearly serving cleaning solution to children under your care is undesirable. However, firing the person most directly involved without fixing any of the issues that contributed to the mistake may leave an unacceptable risk for the issue to happen again. Although this appeared to be the first time anything like this happened on such a scale in a day care facility, the misuse of cleaning fluid due to confusing containers has happened before. Just this July a woman was given an epidural of cleaning fluid after containers were accidentally switched. (See our blog to learn more.)

Identifying the impacted goals and all the causes that led to those impacted goals allows for more solutions than just firing the person found to be most immediately responsible. The use of a Cause Map, a visual form of root cause analysis, diagrams all the cause-and-effect relationships in order to develop as many solutions as possible so the most effective among them can be implemented.

First the impacts to the goals are identified. The safety goal is impacted because of the potential for injury to the 28 children and 2 adults who drank the bleach solution. The bleach solution was stored in a food container, which can be considered an impact to the environmental goal. The customer service goal is impacted because the children and adults were served bleach solution. The day care worker being fired, and the ongoing investigation by the licensing agency, can both be considered impacts to the regulatory goal. Additionally, the treatment of all 30 who ingested the solution impacts the labor goal.

Beginning with one impacted goal, we ask “why” questions to determine cause-and-effect relationships. In this case, the safety goal impact of potential injury is due to the children and teachers drinking the bleach solution they were served. The bleach solution was served by the fired employee who was apparently unaware that the milk jug actually stored bleach solution. The executive director indicated that the jug was labeled, so this is apparently not an uncommon practice at the site. The question this raises is, why was an old milk jug used to store cleaning solution?

The American Association of Poison Control Centers (AAPCC) says: “DO NOT use food containers such as cups or bottles to store household and chemical products” and “Store food and household chemical products in separate areas. Mistaking one for the other could cause a serious poisoning.” Although the reused container was apparently labeled (though not clearly enough to avoid the mistake), it should never have been reused in the first place. As indicated by the AAPCC, reusing containers between food and cleaning supplies is just too big of a risk. It’s also worth noting that reusing a bottle that contained household chemicals for a different household chemical is another no-no: “Never mix household chemical products together. Mixing chemicals could cause a poisonous gas.” Don’t run the risk at your workplace or home. Don’t reuse food containers for cleaning products or mix cleaning products.   Fortunately the children at this day care center got off without lasting damage in this case.

Root Cause Analysis - Incident Investigation

Ice Bucket Challenge Ends in Serious Injuries

By Kim Smiley

In a terrible reminder that awful things can happen at any time, two firefighters were seriously injured helping the Campbellsville University’s marching band raise money for amyotrophic lateral sclerosis (ALS) research by participating in the trendy ice bucket challenge.  If you ever log onto Facebook, you are probably already familiar with the concept behind the ice bucket challenge, but in case you are not a social media fan, the idea behind the ice bucket challenge is that friends tag each other to either donate $100 to an ALS-related charity  or dump a bucket of ice water over their head.  If you choose the ice bucket, you are supposed to take a video or photo as evidence and post it online.

Trying to create an entertaining video of the ice bucket dumping is part of the fun for many of the participants.  In order to make a memorable video to post on social media, the firefighters that were injured used a fire truck ladder to dump ice water on the band from above.  While on the ladder, the firefighters were near high voltage power lines (although they never actually touched the lines) and electricity arced out, injuring four firefighters.  Two firefighters were treated and released, but two were still hospitalized days later.  One was listed as stable, but the other was in critical condition.

This accident clearly illustrates that high voltage can be extremely dangerous even if you don’t touch the equipment. An arc flash can occur when a flashover of electric current leaves its intended path and travels through the air from one conductor to another or to the ground.  The closer a person is when an arc happens, the more dangerous it is.  Arcs are exceptionally hot and can cause very serious injuries and even death from several feet away when high voltage is in use.

The Public Service Commission stated that they will investigate the location to ensure that the power line had the correct clearance from the ground, trees and structures, but initial reports do not indicate any problems with the power poles.  Possible solutions that could be used to reduce the risk of a similar problem in the future are increased education on the risks of high voltage and ensuring that adequate warning signs are in place.

These have been the most dramatic injuries associated with the ice bucket challenge, but there are a slew of videos featuring buckets dropped on heads, slips and a variety of other unintended outcomes that look painful.  If you are considering doing the ice bucket challenge, please remember that a gallon of water weighs over 8 pounds.  A five gallon bucket filled with water is pretty heavy.  Think the plan through carefully before you ask somebody to dump water on you off a balcony because it may end badly.

Root Cause Analysis - Incident Investigation

Fingertips Amputated After Slip on Ice

By ThinkReliability Staff

Information on a slip that caused severe damage to an electrical contractor in Newcastle in August 2013 was recently released by Great Britain’s Health and Safety Executive (HSE). Though this incident didn’t make the front pages of the newspaper, it is representative of many of the injury investigations which we facilitate using the Cause Mapping method.

The first step in the Cause Mapping method of root cause analysis is to capture the what, when and where of the incident and the impacts to the organizational goals. In this case, the what (contractor slip and hand injury), when (August 30, 2013) and where (a moving conveyor at a baguette manufacturer in Leeds) are captured, as well as any differences and the task being performed at the time of the incident. There were two notable differences during the incident as compared to an “average” day that should also be noted: the safety guard had been removed from the conveyor and ice had accumulated on the floor. These differences may or may not be causally related to the incident. Additionally, the task being performed (cleaning up after contract electrical work) is captured as it, too, may be causally related to the incident.

The impacts to the goals are analogous to what stood in the way of a perfect day. A serious injury involving the partial amputation of two fingers and the injury of a third is an impact to the safety goal in this example. The £8,500 fine levied by the HSE is an impact to the regulatory goal. The worker had four weeks off work due to the injury, which is an impact to the labor goal. It is unclear if any other goals were impacted by this incident.

Once at least one impact to the goals has been determined, asking “why” questions helps us complete the second step, or analysis. In the analysis, we capture cause-and-effect relationships that map out the issues that led to the incident. In this case, the injury was caused by the contractor’s hand striking an unprotected drive chain on a moving conveyor. This occurred because the hand struck the area, the drive chain was unprotected, and the conveyor was moving. All three of these causes had to occur for the resulting injury.

The contractor’s hand struck the area because of a slip on an icy floor. Ice from an open freezer door (which appeared to be malfunctioning) had built up and had not been removed.   The drive chain was unprotected because the safety guard had been removed from the conveyor, which was moving likely due to normal operations.

According to Shuna Rank, the HSE inspector, “This worker’s injuries should not and need not have happened. This incident was easily preventable had Country Style Foods Ltd ensured safety guards were in place on the machinery. The company should also have taken steps to prevent the accumulation of ice on the freezer floor. Guards and safety systems are there for a reason, and companies have a legal duty of care to ensure they are properly fitted and working effectively at all times. Slips and trips are the biggest cause of major injuries in the food and drink industry with 37% of all major accidents in the industry being as a result of slips.”

The inspector’s quote clearly identifies the areas for improvement that could reduce the risk of similar incidents occurring. Namely, the manufacturer must ensure that damage resulting in ice buildup is fixed as soon as possible and that in the meantime, ice is regularly cleared away and the area is marked as a slip hazard. If a safety guard is removed for any reason, the conveyor should not be operating until it has been replaced properly. Ensuring that equipment is in proper working order is essential to reduce the risk to workers such as the injuries demonstrated in this case.

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

Root Cause Analysis - Incident Investigation

Chicago O’Hare Commuter Train Derailment Injures 33

By Sarah Wrenn

At 2:49 AM on March 24, 2014, a Blue Line Commuter train entered the Chicago-O’Hare International Airport Station, collided with the track bumper post, and proceeded to derail landing on an escalator and stairway.  Thirty-two passengers and the train operator were injured and transported to nearby hospitals.  Images showing the lead rail car perched on the escalator look like the train was involved in filming an action movie.

So what caused a Chicago Transit Authority (CTA) train, part of the nation’s second largest public transportation system, to derail?  We can use the Cause Mapping process to analyze this specific incident with the following three steps: 1) Define the problem, 2) Conduct the analysis and 3) Identify the best solutions.

We start by defining the problem.  In the problem outline, you’ll notice we’ve asked four questions: What is the problem? When did it happen? Where did it happen? And how did it impact the goals?

Next we’ll analyze the incident.  We start with the impacted goals and begin asking “why” questions while documenting the answers to visually lay out all the causes that contributed to the incident.  The cause and effect relationships lay out from left to right.  As can be seen in the problem outline, this incident resulted in multiple goals being impacted.

In this incident, 33 people were injured when the train they were riding derailed in the O’Hare station thereby affecting our safety goal of zero injuries.  The injuries were caused by the train derailing, so let’s dig in to why the train derailed.  Let’s first ask why the train operator was unable to stop the train.  Operator statements are crucial to understanding exactly what happened.  Here, it is important to avoid blame by asking questions about the process followed by the operator.  Interestingly, 45 seconds before the crash, the operator manually reduced the train speed.  However, at some point, the train operator dozed off.  The train operator’s schedule (working nearly 60 hours the previous week), length of shift, and time off are all possible causes of the lack of rest.  Evidence that the operator was coming off of an 18 hour break allows us to eliminate insufficient time off between shifts as a cause.  In addition, the train operator was relatively new (qualified train operator in January 2014), but also she was an “extra-board” employee meaning she substituted for other train operators who were out sick or on vacation.

Next, let’s ask why the train was unable to stop.  An automatic breaking system is installed at this station and the system activated when the train crossed the fixed trip stop.  The train was unable to stop, because there was an insufficient stopping distance for the train’s speed.  At the location of the trip stop, the train speed limit was 25 mph and the train was traveling 26 mph.  While the emergency braking system functioned correctly, the limited distance and the speed of the train did not allow the train to stop.

The train derailing impacted multiple organizational goals, but also the personal goal of the train operator who was fired.  During the investigation, we learn that the train operator failed to appear at a disciplinary hearing and had a previous safety violation in which she dozed off and overshot a station.  These details reveal themselves on the cause map by asking why questions.

The final step of the investigation is to use the cause map to identify and select the best solutions that will reduce the risk of the incident recurring.  On April 4, 2014, the CTA announced proposed changes to the train operator scheduling policy.  In addition, the CTA changed the speed limit when entering a station and moved the trip stops to increase the stopping distance.   Each of these identified solutions reduce the risk of a future incident by addressing many of the causes identified during the investigation.

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.