The reactor containment structures which house the nuclear reactors at Fukushima made by GE, Hitachi, and Toshiba, have so many holes in them that they are preventing workers from making any substantial progress on improving conditions inside of the destroyed reactors, and will ultimately delay the removal of melted fuel from the reactor buildings, the question is just how long?
Radiation levels around the site and inside of the reactor buildings are so high that workers main priority is to attempt to manage dose by conducting work from as far of a distance as possible, but TEPCO is working in a confined space, which is becoming ever more restrictive every day. The utility has been forced to construct temporary storage tanks for over 320,000 metric tons of contaminated water so far, with plans for another 75,000 metric tons to be added, but each tank is filled up every two and a half days at the current rate of contaminated water being generated.
Since no progress can be made in the most critical areas of the reactor buildings, TEPCO has been forced to put most efforts towards removing the 1,533 spent fuel assemblies from the Unit 4 spent fuel pool, but even that requires special construction, unique equipment, and will be a process that takes years to complete. The next question becomes where to put the spent fuel once it is removed from the spent fuel pool. There is a common fuel pool building which houses spent fuel from multiple reactors on-site, but it only has a capacity of 6,800 assemblies and already holds 6,300. TEPCO is hoping to remove some of the oldest spent fuel from the common fuel pool and put it into dry cask storage ahead of its pre-disaster schedule.
“It will take a considerable amount of time before this site will become history, what we need to do is isolate, remove and store the damaged and broken nuclear fuel safely,” said TEPCO plant manager Takeshi Takahashi. “This work will take 30 to 40 years to complete.”
In a best-case scenario, those holes would not be present, and workers would be able to fill up the reactor containments with enough water to provide sufficient cooling for melted fuel that is attacking the concrete liner, reduce radiation exposure, and allow operators to prepare for the investigation and removal of melted fuel debris. However, this is not the reality of the situation, and every day hundreds of metric tons of groundwater is seeping into the crippled reactor buildings, and mixing with water being pumped in through an ad hoc and wholly inadequate cooling system.
“We are developing remote technologies to do that, but in case there are too many holes and it is difficult to repair all of them, we have to take a different approach,” said TEPCO official Shunichi Suzuki, who is head of research and development at Fukushima Daiichi decommissioning. “One approach we are considering is putting grout, like cement,” he added. “In other words, filling it in. That would block all the holes.”
TEPCO is building tanks to hold the water and has capacity for 320,000 metric tons of water but wants to increase that to 400,000 metric tons by June. The utility is considering several measures to dispose of the water, including treating and releasing it into the sea, which the international public has shown itself firmly against. Many public figures and organizations have voiced their opposition to this plan, but TEPCO officials said they would go ahead with that plan if given the consent of authorities.