Tag Archives: Fukushima Daiichi

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.

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.