20.09.2010 14:34

Marking the disposal site would be a major challenge

When discussing final disposal of spent fuel, the question of marking it for the benefit of future generations is often raised. Should the final disposal site be marked? If so, how? There is also an ongoing discussion on whether future generations will be interested in today’s disposal project and spent fuel to an extent that would warrant an intrusion of the disposal facilities.

Juhani Vira, Vice President for Research at Posiva, will the disposal site Juhani Virain Olkiluoto be marked for future generations?

This is a matter for the Finnish State to decide; in practice, the decision will be taken by the Radiation and Nuclear Safety Authority. When all spent fuel has been finally disposed of in an acceptable manner, the responsibility for it is passed to the State. That is not to say, though, that the matter is not of interest to us at Posiva, too.

It is unlikely that the disposal would be marked in the immediate future. Any drilling of deep holes, for example, is prohibited in the area. However, the survival of any marks or markings cannot be guaranteed over a long time span. One can also speculate whether the markings would be correctly interpreted. If misinterpreted, the ‘memorials’ or ‘markers’ could, on the contrary, tempt people to intrude the disposal facilities.


What kind of markings could be used to convey information to distant future?

“Information can be transferred by way of archived records. The records can be maintained in the archives as long as people have a continuous cultural link between them. When that link is severed, it is uncertain whether the archives will survive this either, and even if they did, would the markings be understood. In any event, any markers left in nature are unlikely to survive the next ice age.”


Has this issue of markings been a subject of international discussion?

“The issue was brought up a lot in late 1980s and early 90s. There was much international discussion on the use of markers and ways of preventing any inadvertent entry to the disposal facilities. No ironclad way to prevent inadvertent entry was found, but when the waste is disposed of outside any ore deposits, deep inside ordinary bedrock, the probability of such an incident is made very small. Very few new ideas have been presented regarding this over the last 10 to 15 years. It is true, though, that the Nuclear Energy Agency of OECD decided to carry out a fresh analysis on the matter.”


What would happen if the intruders came across a canister?

If the canister was intact, nothing much would happen. However, its radiation level would be higher than that of the natural background radiation, and any prolonged stay near the canister would during the next few centuries cause a health risk.


What if the intruders opened the canisters?

Opening a canister at any time during the next few centuries would cause a severe radiation exposure over a few hours. After one thousand years, the radiation level will have decreased considerably, but even then, an opened canister will still provide a significant radiation dose if people spend too long near it.


Are there really any things that can be feasibly predicted far into the future?

We can, for example, estimate the quantities of radioactive materials that could potentially leak into the bedrock from a canister and further on to living nature. But people’s behaviour after tens of thousands of years is something we are not in a position to predict. We cannot control the behaviour of future generations either, nor have we any moral right to do so. The important thing is to collect any information currently available on disposal and act accordingly.

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