The Nuclear Decommissioning Authority

 

Work to reduce a major asbestos hazard at the Chapelcross site is ahead of schedule, while an innovative approach to analysing the material could save up to £49 million.

Once electricity generation stopped in 2004 and the site's 16 heat exchangers cooled down, the asbestos cladding began to absorb water, becoming heavy. When chunks were dislodged, it became essential to strip the cladding off entirely.

The project, launched 18 months ago, is believed to be the largest asbestos removal in Europe. Asbestos lagging is also being removed from the turbine hall, in all around 3,300 tonnes.

Based on known site conditions, it was calculated that most of the asbestos would be contaminated with low levels of radioactivity, requiring treatment and disposal at the UK's Low Level Waste Repository near Drigg in Cumbria. Waste disposal costs were initially estimated to be around £50 million.

The first step was to put in place some protection from the weather, creating a safe working environment for the team, and to analyse the asbestos. The weather-proof structure required 1,600 tonnes of scaffolding and is designed to withstand strong winds.

In consultation with Sellafield Site and the Low Level Waste Repository, the team came up with the option of safely storing all the asbestos waste at Chapelcross until it was feasible to undertake a single 'supercompaction' campaign at Sellafield before transferral for final disposal at the LLW Repository.

The NDA's Site Programme Manager at Chapelcross, Keith Riding, said: "I applaud the team's constant drive for improvement, which has produced enormous benefit in terms of hazard reduction, and I welcome the cost savings."

Following completion of the protective weather-proof structure six weeks ahead of schedule, teams at Chapelcross saw an opportunity to carry out a further radiological characterisation exercise, challenging conventional practice.

This assessment confirmed that a significant amount of the asbestos was far less contaminated than originally calculated, which could be 'free-released' and disposed of as special waste in licensed landfill sites.

Three heat exchangers are now completely free of asbestos and the work is one month ahead of schedule.

This innovative approach has resulted in a significant hazard reduction and minimisation of the amount of waste sent to the LLWR, whilst waste disposal costs could be reduced to around £1 million as the project continues for the remaining four years.