Editorial: Removal of nuclear fuel assemblies

Decommissioning of reactors finally underway

The day before yesterday the Tokyo Electric Power Company (TEPCO) began removing the nuclear fuel assemblies from a pool for spent fuel at the No. 4 reactor of the Fukushima No. 1 (Daiichi) nuclear power plant.

Two years and eight months have passed since the disaster. The government and TEPCO have entered the second stage of the three-stage decommissioning work.

This represents a milestone. But the work is a risky task that, as Shunichi Tanaka, chairman of the Nuclear Regulation Authority, said, is “even more worrisome than the contaminated water.” A system must be created under which the work can continue to be carried out safely and steadily over the long term.

The building housing the No. 4 reactor was heavily damaged by a hydrogen explosion at the time of the 2011 earthquake and tsunami. There was no fuel in the reactor core because it was undergoing a regular inspection, but a tremendous amount of debris fell into the fuel pool to which 1,533 fuel assemblies had been moved. TEPCO has been under pressure by people both within Japan and overseas to deal with the problem because of fears that a catastrophe may occur should the building collapse as the result of an aftershock.

Specially developed cranes are being used for the work. Each fuel assembly is removed and then placed in a shipping cask, which is loaded onto a trailer. The fuel assemblies will then be moved to a pool approximately 100 meters away, which will be used to store assemblies from other reactors as well.

The removal of nuclear fuel from a building that has been destroyed by an explosion is without precedent, and it will be a learning process.

In the worst case, if bits of debris get stuck to the fuel assemblies or they are otherwise damaged when being lifted, radioactive materials may be dispersed into the atmosphere. In this unforeseen situation, the possibility of a fuel assembly falling from the crane or of a shipping cask falling cannot be eliminated.

At present, the work is limited to moving unspent fuel, which is comparatively easy to handle. When it comes to moving spent fuel, which emits high levels of radiation, the task will be more difficult. TEPCO expects to complete the work at the No. 4 reactor by the end of next year, but they must exercise caution.

Not only will the atmosphere at the job site be extremely tense, the work also carries a risk of exposure to radiation. The health of the workers must not be neglected in an effort to stay on schedule.

Still, when you consider the entire decommissioning project, this is merely the prelude. The work is expected to take 30 to 40 years, and there will be many more difficulties.

Water used to cool the containment vessels in the buildings housing the No. 1, 2 and 3 reactors has leaked, and highly contaminated water is believed to have accumulated. The level of radiation in the vicinity is so high that people cannot work there.

A large amount of spent nuclear fuel had been stored in the pool, but no method for its removal had been determined. Another tricky problem is the melted fuel in the reactors. It is not clear exactly where the fuel is, and development of the technology needed to remove it is nowhere in sight.

While construction of nuclear power plants was promoted in Japan, the development of technology for their decommissioning was essentially put on the back burner. The International Research Institute for Nuclear Decommissioning, made up of power companies and other businesses, was finally created this year. We would like the institute to accelerate the research and development of technology for the removal of melted fuel. Every nuclear power plant will have to be decommissioned eventually.

Whether or not the essential manpower can be secured over the next few decades is another matter of concern. TEPCO’s contaminated water problem is believed to have resulted from a lack of both money and manpower and the fact that fewer and fewer workers are familiar with the work. A similar problem may occur with the decommissioning.

We are reminded of how dearly Japan has paid for the promotion of nuclear power. The current method, which places a heavy burden on flesh-and-blood human beings, has its limits. From a humanitarian standpoint, the effort to develop technology such as a robot that can collect melted fuel and eliminate the need for human workers as much as possible is a pressing task.

(Originally published on November 20, 2013)