Nuclear Power Dossier: Decommissioning

Decommissioning has a ring of finality to it. But don't be fooled. A nuclear reactor will be standing for another 150 years before it is finally razed to the ground

As with permanently disposing of radioactive waste, the UK nuclear industry has never fully disposed of a commercial nuclear reactor. The major problem is that the reactor contains highly radioactive high-level waste that is less easily managed than spent fuel.

It takes three years alone to remove the 60,000 fuel rods that were in the reactor core when it powered its last watt. The sheer volume of the job causes delays, as this ‘high-level’ waste has to cool for at least six months before it can enter interim storage, before being prepared for final disposal.

Simultaneously, work gets underway on removing other high-level waste, known as CRUD – corrosions, residuals and unidentified deposits, or ‘primary hazardous materials’ – from the cooling systems. Again, this is high-level waste that has to be casked and sent for permanent disposal.

Decontamination of the facility follows, where residual radioactive and chemical waste is removed from the fabric of the buildings and equipment by washing, heating, chemical or electrochemical action, and mechanical cleaning. This creates a cocktail of chemical and radioactive particles that will evaporate into the atmosphere or leak out into the ground. Some auxiliary buildings on the ‘non-radioactive’ side of the site will be removed or recycled ‘for possible re-use’, and the reactor’s biological shielding may be dismantled.

The reactor itself is sealed. This is known as the ‘care and maintenance’ phase and can last up to 100 years depending on the policy of the installation state. During this time the site is policed and monitored.

If it can be demonstrated that radiation levels are below the national regulatory requirements, the operating licence is terminated and parts of the site outside the reactor can be made available for ‘appropriate’ re-use. In the UK it will be designated a ‘brownfield’ site, perhaps suitable for ‘appropriate’ industrial purposes.

After this time, demolition and site clearance takes place. The reactor core is unsealed and starts to be taken apart. At this point it still contains dangerous radioactive waste. The core reactor contains parts that are known as ‘activation products’, such as steel  components that have been exposed to neutron irradiation during the reactor’s generation life. The atoms of these components are changed into different isotopes, such as iron-55, cobalt-60, nickel-63 and carbon-14. The first two emit gamma rays, but with a short half-life, so that after 50 years from closedown their hazard is much diminished, but not to a level where it is safe. It is classified as intermediate waste, which means the core reactor has to be dismantled and cut into small pieces to be packed in containers for final disposal.

Finally the containment buildings are demolished. The rubble could either be removed or buried on site: both options are being considered. Only now can the site be termed decommissioned and the land made available for ‘alternative use’. Monitoring of the site ceases at this time.

While this process has never been fully achieved, the UK Atomic Energy Authority  (AEA) is presently directing the decommissioning of the experimental Windscale Advanced Gas-Cooled Reactor (WAGR) at Sellafield. This reactor opened in 1963 and operated until 1981, when decommissioning started. While the land at the facility is due to be returned to brownfield status by 2030, it could be another century before the core is opened up and prepared for long-term disposal. It is estimated decommissioning WAGR will cost between £80-100m. This is being paid for by the Department of Trade and Industry, which sees it as a ‘demonstration project’ for marketing expertise and skills to other nuclear countries.

In America, industry and government estimates for the cost of decommissioning have risen from an initial $120m in 1991 to a staggering $450m.

Such overruns have led the industry to consider another option: entombment – a ‘does what it says on the tin’ cost-cutting measure. Rather than expend time and energy on the ‘care and maintenance’ phase, entombment requires the reactor core to be encased in concrete. This is how Chernobyl was contained, but 20 years on its concrete overcoat is cracking and radiation is leaking out – a fitting reminder of the folly of nuclear power.

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This article first appeared in the Ecologist June 2006

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