21 Radioactive waste

Into Eternity, a documentary film that follows the construction of a high-level radioactive waste storage facility in Finland, was released in Japan in 2011. The film made us realize that the disposal of "radioactive waste" is a problem that needs to be resolved regardless of whether or not nuclear power plants are maintained or scrapped. In this edition of Earthrium we report on a Japanese underground research laboratory as we consider radioactive waste, which will be an ongoing problem for humankind for tens of thousands of years to come.

Text/photos: Soichi Ueda

last update 2014.5.28.

Will it still be safe in 100,000 years?

Let's start by looking at the globe for this edition of Earthrium. At present, nuclear power plants operate in 30 countries around the world, with more than ten planning to introduce them in the future. Despite this, only two countries, Finland and Sweden, have so far finalized plans for the construction of storage facilities for the high-level nuclear waste produced by nuclear power plants. Circumstances in the other countries remain difficult, with some having decided on locations only for the plans to founder, and others like Japan sending application information to municipalities only for none to volunteer to host facilities.

The only country where the construction of a disposal facility has begun is the one mentioned in Into Eternity: Finland. The time required before high-level radioactive waste no longer poses a risk to humans is a mindboggling 100,000 years. It is said that humankind as it exists today (i.e. homo sapiens) evolved around 70,000 years ago. There is every possibility that humankind will not be around 100,000 years from now. Even if we are still around, just as those of us alive today could not communicate with humans of 70,000 years ago, it is hard to imagine that the "language" of today will still be understood in 100,000 years. The problem of how to manage this negative legacy safely so that future generations don't interfere with it was one that was debated earnestly in the lead-up to the construction of the facility in Finland, and was one of the themes of the film.

Into Eternity

→Into Eternity: the Movie

But let us return to basics.

At most power plants, electricity is generated by causing vaned wheels called turbines to rotate at high speed. High-temperature, high-pressure steam is used to rotate these turbines. Power plants where this steam is produced using heat generated by burning fossil fuels such as oil or coal are called thermal power plants, while those where steam is produced using heat generated by the nuclear fission of uranium are called nuclear power plants.

Uranium as a raw material is not radioactive, but when it undergoes nuclear fission it produces material (fission product) that emits strong radiation. This material is so toxic that spending more than a dozen or so seconds in close proximity to it will result in death. Moreover, it takes an incredibly long time for this material to become safe. The half-life of plutonium 239, for example, is 24,100 years, while the half-life of plutonium 237 is 2,140,000 years.

What is geological disposal?

Well then, how are countries proposing to dispose of high-level radioactive waste, which remains highly toxic for tens of thousands of years?
There was a time when it was considered reasonable to dump radioactive waste in the ocean. In fact, many countries, including Japan, once practiced the ocean disposal of low-level radioactive waste. In 1993, however, an amendment to the London Convention (or, to use its official name, the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter) banning the dumping at sea of all radioactive waste was adopted, as a result of which such disposal no longer occurs.

Other methods of disposal, including dumping in space and burial under ice in the polar regions, have also been considered, although there is little probability of either of these being adopted in the future, since disposal in Antarctica is banned under the Antarctic Treaty and the consequences of an accident in space are too great. And so while a number of different ideas have been considered, the only relatively safe disposal method being considered at present is geological disposal.

But before we go on to talk more about geological disposal, let us first look at what needs to be done to high-level radioactive waste before it can be disposed of. Radioactive waste is produced by nuclear power plants both while they are in operation and when reactors are decommissioned. It ranges from low-level waste such as the concrete and other material generated during dismantling to high-level waste such as spent fuel that is produced even when a plant is operating. High-level waste is usually turned into what is known as "vitrified radioactive waste" by melting it together with glass, a material that remains stable for long periods, and pouring the resultant mixture into stainless steel containers.

But radioactive waste that has been vitrified cannot be disposed of underground immediately. Because it is still warm, it needs to be cooled for between 30 and 50 years. In Japan, this vitrified radioactive waste is stored at Tokai village in Tochigi prefecture and Rokkasho village in Aomori prefecture.

Schematic drawing of vitrified radioactive waste

Schematic drawing of vitrified radioactive waste (Produced based on materials provided by the Agency for Natural Resources and Energy)

According to the website of the Nuclear Waste Management Organization of Japan, as of the end of November 2013 the number of containers of vitrified radioactive waste in Japan stood at 2,035. And if all of the waste currently stored at all of Japan's nuclear power plants was reprocessed and vitrified it would amount to the equivalent of 24,800 containers. Furthermore, if Japan's nuclear power plants continue operating, it is predicted that the equivalent of around 1,900 containers of high-level radioactive waste will be produced annually.

It is for this reason that these nuclear power plants that continue to produce waste that remains toxic for so long despite a disposal site not even having been selected have been compared to "condominiums without toilets." What's more, Japan's reprocessing plan (a nuclear fuel cycle), the aim of which is to reduce nuclear waste, has been beset by one problem after another, as a result of which it is behind schedule and facing mounting costs.