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Radioactive terminal storage is being corroded away

Published Oct 08, 2009

Researchers at KTH have discovered that the copper capsules which Swedish radioactive waste will be placed in, can corrode far too quickly. Instead of the estimated service life of 100,000 years, the capsules may collapse within 1,000 years.

Peter Szakalos
Peter Szakalos, corrosion researcher at KTH

“What is needed is much thicker copper capsules than the 5 cm which is being used today. Five centimetres is not enough,” states Peter Szakalos, corrosion researcher at KTH.

The research that he and his research colleagues have carried out is based on studies of copper coins which ended up at the bottom of the sea when the ship of the line ‘Wasa’ sunk, and which remained there for 333 years. The reason is simple, the environment for terminal storage and the bottom of the sea where Wasa lay are very similar to each other.

“The two environments are so similar that Svensk Kärnbränslehantering believes that this type of study should be used to find out what happens when this type of corrosion occurs. In is an extremely relevant environment,” says Peter Szakalos.

He adds, it may be necessary to have up to 1 m of copper metal in order for it to last 100,000 years. In addition, there is another disturbing factor. The copper capsules are heated up by the radioactive waste inside them, and warm copper corrodes even faster.

“This means that the capsules, in a worst-case scenario, may last less than 1,000 years,” says Peter Szakalos.

He adds that Svensk Kärnbränslehantering, from the beginning, said that the copper capsules needed to be 20 cm thick, but even then, researchers from KTH were sceptical.

The reason why recommendations as to the size of the copper capsules has changed is due to several factors. The main reason is that the manufacture of thick capsules involves a difficult manufacturing process, but the price of copper also plays a role to some extent.

A previous report from KTH’s researchers about the corrosion of copper has been refuted completely. Criticism has been directed towards the fact that the copper coins in Wasa must have been of different thicknesses due to an erratic manufacturing process. But this has been rejected by Peter Szakalos.

“The copper coins are extremely even and fine, because at the time the Wasa went down, we had learned how to use the milling process for the manufacture of coins. The coins are of equal thickness,” says Peter Szakalos.

For more information, contact Peter Szakalos at szakalos@kth.se or 0707 - 53 79 46.

Peter Larsson

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Last changed: Oct 08, 2009