With the backing of Japan's government, Tokyo Electric Power Company Holdings (TEPCO) has decided to revise its plan to remove highly radioactive spent fuel from the damaged Fukushima nuclear power plant. It's the fourth re-think made by the utility since the plant suffered a meltdown following the 2011 earthquake and tsunami -- and yet another delay to a plan that's expected to take anywhere from 30 to 40 years.
Storage tanks for contaminated water are seen through a window of a building during a media tour to the tsunami-damaged Fukushima nuclear power plant. (Image: AP)
TEPCO, the company responsible for cleaning up the beleaguered Fukushima plant, has sketched out a revised roadmap for the decommissioning process, which was approved by Japan's government yesterday, reports The Japan Times. The new plan calls for the extraction of the highly radioactive spent fuel from the cooling pools of reactors one and two starting in 2023 instead of 2020. Work on reactor three will go ahead as planned next year, having already been delayed earlier this year. All three reactors experienced core meltdowns following the 2011 earthquake and tsunami.
The decision to delay the decommissioning process was informed by recent robotic surveys and the identification of new technical and safety issues. In February of this year, soaring radiation levels fried a robot that was sent in to inspect and clean reactor two. Then in July, an aquatic robot managed to send back photos of what appeared to be melted nuclear fuel at the bottom of reactor three. The precise location of the melted fuel still needs to be confirmed, however, and more work needs to be done to create robots that can withstand the intense levels of radiation near the core. The new delays announced by TEPCO today were prompted by these realities, along with the discovery of previously unknown damage in the storage pool areas and the need for further radioactive decontamination.
Naohiro Masuda, head of TEPCO's decommissioning efforts, said the three to four decade plan "may not sound convincing because of all the unknowns and [because] we haven't found most of the melted fuel" within the reactor cores. But what's needed, he said, is a target for developing the technologies required to accomplish this goal.
Under the revised plan, the cleanup process will require the removal of the fuel rod assemblies from the spent fuel pools before any of the melted fuel debris can be removed. An extraction plan for the removal of the radioactive debris won't even be considered until 2019. At this point, the best case scenario sees the extraction of the melted nuclear fuel starting in 2021.
But TEPCO has also delayed choosing the specific method for the debris extraction, which is considered the most challenging phase of the decommissioning process. The favoured method at this point would involve removing the debris from the sides of the reactors after partially filling them up with water. That said, TEPCO still needs to produce an estimate showing how long it will take to remove the melted fuel, and a plan showing how and where the radioactive waste will be stored. It also has to decide what to do with the Fukushima plant itself.
If all this isn't enough, there's all that contaminated water to consider as well. TEPCO's updated roadmap establishes new goals to reduce the amount of underground water at the plant. Currently, clean water underneath the plant is getting mixed together with water that's being used to cool the damaged reactors, which subsequently becomes contaminated with radiation. TEPCO has made some progress in this regard, but it would now like to cut the amount of water used to 150 tonnes per day from the current 200 tonnes.
As this unfortunate episode makes painfully clear, when nuclear power goes wrong, it really goes wrong. Should all go according to plan, the plant won't be fully decommissioned until the mid 2050s, and possibly even later given the many technical challenges that await.