In the three years since the start of the Fukushima Daiichi nuclear disaster there has been a plethora of drastic changes made to the landscape of the Fukushima Daiichi nuclear power plant including; new processing facilities for radioactive water, a farm of storage tanks for contaminated water, new cooling systems, a new carpet of thick steel sheets for most of the grounds around the crippled reactor buildings, new coverings and support structures for the damaged reactor buildings, and a new decommissioning facility, but little progress made in the decommissioning operation.
Over 430,000 tons of highly radioactive water is estimated to be stored at the Fukushima Daiichi site, in some 1,000 storage tanks. TEPCO is working to increase its storage capacity to 8000,000 tons, but the problem is that storing the contaminated water in above-ground tanks risks leaving them vulnerable to other threats, like earthquakes and accelerated wear.
Contaminated water continues to pile up every day at the Fukushima Daiichi site. Over 1,000 metric tons of groundwater flow down the mountain side of the Fukushima Daiichi site, through the grounds of the facility, and into the Pacific Ocean. An estimated 400 tons pass through the crippled reactor buildings themselves, coming in contact with the melted nuclear fuel and becoming contaminated, before continuing their journey into the ocean. Approximately 100 tons of this radioactive water is captured each day and held in storage tanks, but room for storage on-site is quickly running out and there have been repeated problems with leaks.
Some of the leaks have released enough radioactive materials into the environment to be classified as a level three incident on the International Nuclear Event Scale (INES), which measures incidents on a scale of 0 to 7. As the volume of contaminated water increases, so do the problems with processing and storage, which draws concern among experts who fear that the problems stemming from managing the radioactive water at the tank farm will only increase in the future.
While Tokyo Electric, the utility which owns and operates the Fukushima Daiichi plant, has started removing fuel assemblies from the Unit 4 reactor, they still face an uphill battle with the day to day management of the facilities. Repeated leaks of radioactive materials and almost daily accidents have undermined much of the faith and support in TEPCO’s ability to see the decommissioning project through to completion.
Tokyo Electric’s roadmap for decommissioning, which was created by the central government and TEPCO, outlines three phases. The first phase includes all spent fuel removal operations at all Units 1-4. The second phase is by far the most difficult as it includes all work to remove the molten nuclear fuel from Units 1-3. The third phase signals the completion of fuel removal operations and includes work to dismantle the crippled reactor buildings.
One of the most important variables in whether decommissioning will progress on schedule or not is whether TEPCO can supply enough technical staff and workers, before they exceed their permitted radiation exposures or pursue work at other nuclear facilities. Repeated incidents at the site have been caused by human error, and these incidents will only increase as the experience and proficiency of workers on-site decreases.
Currently, TEPCO is working on removing the spent fuel rods from the Unit 4 spent fuel pool. At the time of the earthquake and tsunami there were 1,331 spent fuel assemblies and 202 new fuel assemblies stored in the spent fuel pool. As of March 3rd, TEPCO has removed over one quarter (418) of the 1,533 total assemblies, 396 spent fuel assemblies and 22 new fuel assemblies. The utility plans to have the Unit 4 spent fuel pool emptied by the end of the 2014. TEPCO estimates it will start removing the 1,573 total spent fuel rods from the Unit 1-3 spent fuel pools in 2015 for Unit 3 and 2017 for Unit 1 and Unit 2.
Some readers may not realize why the second phase will be so difficult. Aside from the fact that no current technologies will assist in removing the extremely radioactive melted fuel rods due to the high levels of radiation, that workers cannot enter critical areas of the reactor buildings due to the same high levels of radiation, and the fact that no one knows where the melted reactor fuel is currently located or what condition it is in – in all three of the reactors, there is also a problem of the sheer volume of melted materials which must be removed from Units 1-3. While there were 1,533 spent fuel rods in the Unit 4 spent fuel pool, there were also 1,496 fuel rods believed to be in the reactors of Units 1-3. The majority, if not all, of these fuel rods are believed to have melted. In order to remove melted fuel from the containment vessels, workers must fill them with water to reduce radiation levels, but this will require an enormous amount of work restoring the containments to make them capable of holding the water.
If TEPCO is capable of keeping up with the decommissioning roadmap, it still will not start removing the melted fuel from the Unit 1 and Unit 2 reactor buildings until 2020, and the Unit 3 reactor building in 2021. However, seeing as Tokyo is hosting the Summer Olympics in 2020, it is hard to believe that TEPCO will attempt much, if any, fuel extraction operations before the Olympic Games.
Tokyo Electric also decided to decommission the Unit 5 and Unit 6 reactors on January 31st, 2014. These units were not damaged in the earthquake and tsunami, but it is thought that decommissioning these reactors will help train workers and aid TEPCO in planning to decommission the damaged reactors.