Real-time monitoring of copper corrosion at the Äspö HRL

• In Sweden the principal strategy for high-level radioactive waste disposal is to enclose the spent nuclear fuel in tightly sealed copper canisters that are embedded in bentonite clay about 500 m down in the Swedish bed-rock. Initially, a limited amount of air will be left in a repository after emplacement. The entrapped oxygen will be consumed through reactions with minerals in the rock and the bentonite and also through microbial activity. After the oxygen has been consumed in the repository, after a few hundred years at the very most, corrosion will be controlled completely by the supply of dissolved sulphide to the canister. The present work concerns the oxic period after emplacement. The main hypothesis is that the average corrosion rate of the canister under oxic conditions will be less than 7 μm/year, and that pitting will only be possible under these conditions. The Äspö Hard Rock Laboratory offers a realistic environment for different experiments and tests under the conditions that will prevail in a deep repository. Real-time monitoring of copper corrosion is presently performed with polarization resistance, harmonic distortion analysis and electrochemical noise techniques. The first two techniques are used to derive information regarding the general corrosion rate and the third to derive information regarding localized corrosion. In order to support these measurements at Äspö, laboratory work is also performed at the Royal Institute of Technology in Stockholm using the very same corrosion monitoring equipment and also other equipment and techniques. Copper coupons are also exposed at Äspö. Results from the work at Äspö and in Stockholm are presented with an emphasis on the gained information concerning localized corrosion. The recorded corrosion rates at Äspö are well below the value given above, and the recorded localization factors are interpreted as indicating only a slight tendency to local attack.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik -- Korrosionsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering -- Corrosion Engineering (hsv//eng)

Nyckelord

Copper

General corrosion

Groundwater

Localized corrosion

Real-time corrosion monitoring

Bentonite clay

Copper canisters

Copper coupon

Corrosion monitoring

Electrochemical noise technique

General corrosion rate

Hard rocks

Harmonic distortion analysis

High level radioactive waste disposal

Information concerning

Laboratory work

Local attack

Localization factor

Microbial activities

Oxic conditions

Polarization resistances

Real time corrosion monitoring

Real time monitoring

Realistic environments

Royal Institute of Technology

Spent nuclear fuels

Stockholm

Aluminum corrosion

Bentonite

Copper corrosion

Dissolved oxygen

Electrochemical corrosion

Oxygen supply

Radioactive waste disposal

Radioactive wastes

Corrosion rate

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