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Exploding myths
12:37 05 Mar 2003
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If there is one thing a demolition company needs to be when it
comes to the decommissioning of a nuclear plant, it is controlled.
So it comes as no surprise that the demolition contractor working closely with British Nuclear Fuels Ltd (BNFL) is none other than the Yorkshire-based Controlled Demolition Group.
Nor is the association between the two companies something new.
"The relationship has evolved over a period of six to seven years," says CDG managing director Darren Palin. "In 1995 BNFL invited us to undertake the dismantling of reactor buildings at Berkeley near Bristol and we haven't looked back since."
CDG was the first demolition contractor to undertake the dismantling of reactor buildings at a UK nuclear power station and, since then, the company has maintained its preferred contractor status through a series of contracts within the nuclear power station industry at plants such as Dounreay, Hunterston and Aldermaston.
At the moment it is the Trawsfynydd nuclear power plant in north Wales that is supplying the team with the most decommissioning work and, according to Palin, it is thanks to the demolition industry's preoccupation with safety that the company was able to help the nuclear power station improve its poor safety record.
"Although demolition was by virtue of the name a dirty word when we first started, we helped Trawsfynydd climb up the BNFL safety league table," recalls Palin. "When we arrived, it was bottom of the league."
Stringent risk assessment
Accustomed to working to strict safety requirements, CDG used its extensive knowledge of stringent risk assessment to good effect. "The nuclear inspectorate polices the sites heavily. If you drop a spanner and that is not included in the method statement, it is classed as an accident," says Palin. "For BNFL, safety is life and death in real terms."
Fortunately the contractor has confidence in the client's commitment to safety. "It practices what it preaches," he adds.
By taking on an ex-BNFL engineer who had worked on the Trawsfynydd site for 25 years, CDG was able to refine its method statements and risk assessments. "The engineer worked in tandem with our project manager and stayed with us for two years before retiring," recalls Palin.
In March 2001, the demolition contractor also established a research working party with BNFL to look at ways of improving methods of deplanting nuclear reactor works and, in particular, the development of machinery capable of tackling reactor ponds and pools.
Despite the need for such stringent safety measures, CDG has not been slow to recognise that decommissioning work in the nuclear power plant industry will provide rich pickings for the demolition contractor.
"There will be 15 nuclear power stations coming off line," observes Palin, before commenting that each project presents a different challenge.
"We are trying different ways of dismantling power stations so that they can be reused as brownfield sites - mostly for industrial purposes."
The initial contract at Trawfynydd involved a 40-week deplanting project. This comprised the removal of steam and ancillary pipework, steam vessels and other equipment from the reactor's boiler house.
Along with demolishing the boiler head, CDG has dealt with the dismantling of the incinerator building, boron dust building and turbines.
The latest contract for BNFL has been the decommissioning of the main turbine hall at Trawsfynydd in a project worth £1.7m to the demolition contractor.
Built in 1961, the bombproof turbine hall is described as being of colossal proportions - a mainly steel-framed building with both precast concrete and pressed metal deck cladding, it is 110m long, 72m wide and 34m high at its tallest point.
Although CDG is probably best known for its explosive work, traditional demolition techniques were used when work started in September last year.
As the contents of the turbine hall was contaminated by both oil and radioactive particles, the demolition team used hot cutting techniques to dismantle equipment piece by piece while maintaining stringent safety precautions .
"Once the components have been tested for radiation levels, everything is recycled," explains Palin. "The 18,500t of rubble from the demolition will be crushed for use as backfill and 10,000t of steel will be recycled on site."
The contract also included a complex four-week operation where asbestos contaminated concrete panels had to be dismantled.
About 100 risk assessments were carried out in the turbine hall alone, but apparently that was only the beginning, since careful monitoring continues throughout the project.
One of the largest boxes in the world
According to Palin, this has left the site with what he describes as one the "largest boxes in the world" with 5m to 6m-thick reinforced concrete bases.
"We had to hand demolish the contents piece by piece as the gable end was connected to an adjoining single-floor office block attached to the back wall of the turbine hall."
Added to which, the turbine hall is less than 100m from the now redundant reactor hall.
After a short break in which BNFL was able to reroute mains services away from the hall, the CDG team has now returned with a state-of-the-art Komatsu PC750 ultra-high-reach machine with a 40m-high operating capability to begin demolition of the main structure and its 45cm thick fireproof walls.
The project also includes the dismantling of three concrete water tanks in the hall roof plus 12 transformer loading bays leading from the main building. "We expected the project to take 54 weeks to complete, but using our ultra-high-reach and high-reach excavators, we anticipate completion within 46 weeks," says Palin.
When asked why there is such a sense of urgency to decommission so many nuclear power stations, Palin says: "A lot of them are 30 to 40 years old," explains Palin. "They were only designed for 25 years. However, when the North Sea oil reserves are depleted, what alternative is there? At best, the green alternative can only supply 20% of the national requirement."
With so much nuclear power station decommissioning work in the offing, CDG is re-considering its programme. "We are now reviewing our strategy for the future," says Palin. "As a company, we have expanded and we are still expanding. Instead of one division, we will operate from four divisions. These are: traditional demolition; decommissioning; explosives; and asbestos."
As well as decommissioning nuclear power plants, CDG is also looking at the oil industry where 200 major oil platforms have exceeded their economic life.
"They are being brought to land for dismantling and our skills could be translated into that sector," says Palin. n
So it comes as no surprise that the demolition contractor working closely with British Nuclear Fuels Ltd (BNFL) is none other than the Yorkshire-based Controlled Demolition Group.
Nor is the association between the two companies something new.
"The relationship has evolved over a period of six to seven years," says CDG managing director Darren Palin. "In 1995 BNFL invited us to undertake the dismantling of reactor buildings at Berkeley near Bristol and we haven't looked back since."
CDG was the first demolition contractor to undertake the dismantling of reactor buildings at a UK nuclear power station and, since then, the company has maintained its preferred contractor status through a series of contracts within the nuclear power station industry at plants such as Dounreay, Hunterston and Aldermaston.
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At the moment it is the Trawsfynydd nuclear power plant in north Wales that is supplying the team with the most decommissioning work and, according to Palin, it is thanks to the demolition industry's preoccupation with safety that the company was able to help the nuclear power station improve its poor safety record.
"Although demolition was by virtue of the name a dirty word when we first started, we helped Trawsfynydd climb up the BNFL safety league table," recalls Palin. "When we arrived, it was bottom of the league."
Stringent risk assessment
Accustomed to working to strict safety requirements, CDG used its extensive knowledge of stringent risk assessment to good effect. "The nuclear inspectorate polices the sites heavily. If you drop a spanner and that is not included in the method statement, it is classed as an accident," says Palin. "For BNFL, safety is life and death in real terms."
Fortunately the contractor has confidence in the client's commitment to safety. "It practices what it preaches," he adds.
By taking on an ex-BNFL engineer who had worked on the Trawsfynydd site for 25 years, CDG was able to refine its method statements and risk assessments. "The engineer worked in tandem with our project manager and stayed with us for two years before retiring," recalls Palin.
In March 2001, the demolition contractor also established a research working party with BNFL to look at ways of improving methods of deplanting nuclear reactor works and, in particular, the development of machinery capable of tackling reactor ponds and pools.
Despite the need for such stringent safety measures, CDG has not been slow to recognise that decommissioning work in the nuclear power plant industry will provide rich pickings for the demolition contractor.
"There will be 15 nuclear power stations coming off line," observes Palin, before commenting that each project presents a different challenge.
"We are trying different ways of dismantling power stations so that they can be reused as brownfield sites - mostly for industrial purposes."
The initial contract at Trawfynydd involved a 40-week deplanting project. This comprised the removal of steam and ancillary pipework, steam vessels and other equipment from the reactor's boiler house.
Along with demolishing the boiler head, CDG has dealt with the dismantling of the incinerator building, boron dust building and turbines.
The latest contract for BNFL has been the decommissioning of the main turbine hall at Trawsfynydd in a project worth £1.7m to the demolition contractor.
Built in 1961, the bombproof turbine hall is described as being of colossal proportions - a mainly steel-framed building with both precast concrete and pressed metal deck cladding, it is 110m long, 72m wide and 34m high at its tallest point.
Although CDG is probably best known for its explosive work, traditional demolition techniques were used when work started in September last year.
As the contents of the turbine hall was contaminated by both oil and radioactive particles, the demolition team used hot cutting techniques to dismantle equipment piece by piece while maintaining stringent safety precautions .
"Once the components have been tested for radiation levels, everything is recycled," explains Palin. "The 18,500t of rubble from the demolition will be crushed for use as backfill and 10,000t of steel will be recycled on site."
The contract also included a complex four-week operation where asbestos contaminated concrete panels had to be dismantled.
About 100 risk assessments were carried out in the turbine hall alone, but apparently that was only the beginning, since careful monitoring continues throughout the project.
One of the largest boxes in the world
According to Palin, this has left the site with what he describes as one the "largest boxes in the world" with 5m to 6m-thick reinforced concrete bases.
"We had to hand demolish the contents piece by piece as the gable end was connected to an adjoining single-floor office block attached to the back wall of the turbine hall."
Added to which, the turbine hall is less than 100m from the now redundant reactor hall.
After a short break in which BNFL was able to reroute mains services away from the hall, the CDG team has now returned with a state-of-the-art Komatsu PC750 ultra-high-reach machine with a 40m-high operating capability to begin demolition of the main structure and its 45cm thick fireproof walls.
The project also includes the dismantling of three concrete water tanks in the hall roof plus 12 transformer loading bays leading from the main building. "We expected the project to take 54 weeks to complete, but using our ultra-high-reach and high-reach excavators, we anticipate completion within 46 weeks," says Palin.
When asked why there is such a sense of urgency to decommission so many nuclear power stations, Palin says: "A lot of them are 30 to 40 years old," explains Palin. "They were only designed for 25 years. However, when the North Sea oil reserves are depleted, what alternative is there? At best, the green alternative can only supply 20% of the national requirement."
With so much nuclear power station decommissioning work in the offing, CDG is re-considering its programme. "We are now reviewing our strategy for the future," says Palin. "As a company, we have expanded and we are still expanding. Instead of one division, we will operate from four divisions. These are: traditional demolition; decommissioning; explosives; and asbestos."
As well as decommissioning nuclear power plants, CDG is also looking at the oil industry where 200 major oil platforms have exceeded their economic life.
"They are being brought to land for dismantling and our skills could be translated into that sector," says Palin. n
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