Decommissioning opportunity

Surface preparation and finishing specialist Wheelabrator Group has been awarded a contract to supply equipment for decontaminating materials at one of Europe’s nuclear facilities.

The company will supply a £350,000 abrasive blasting unit on behalf of customer RWE NUKEM to the European Commission’s Joint Research Centre (JRC) in Ispra, Italy.

A Wheelabrator R3d (V) Euro Tumblast machine, traditionally used in heavy duty metal foundries, will be used to decontaminate metal components and concrete blocks as part of JRC-Ispra’s extensive decommissioning programme.

Slightly contaminated material is produced when active nuclear facilities are decommissioned at the end of their useful life. Demolition of buildings creates large amounts of components, such as bricks, stone, steel and other structural material, considered to contain low levels of radioactivity within the surface layer.

Phil Smith, senior project manager at nuclear engineering specialist RWE NUKEM, said: “JRC Ispra has initiated a programme to reduce costs and minimise radioactive waste quantities, a major component of which is the decontamination of materials to clearance levels suitable for unconditional release in line with EU directives.”

Custom built at Wheelabrator Group’s manufacturing facility in Ossett, near Wakefield, design modifications were required to the R3d (V) machine to fit the low headroom at its new home and enhance its safety features. A team of seven people from Wheelabrator Group worked in conjunction with engineers from Warrington-based RWE and JRC Ispra to tailor the machine.

Located in Area 40 at the Ispra site, the unit will replace the old and obsolete chemical baths. A secondary containment wall and airlock will be added to the room to reduce noise levels and aid contamination control.

With a 700 litre capacity, material to be processed in the machine will be sealed in 220 litre drums and transferred to the machine via a hydraulic loader. Operators will key in commands via a touch screen console located safely outside the secondary containment wall.

The main chamber is equipped with two Ezefit blast wheels, each with six blades and driven by a direct couple motor, which propels the sharp steel grit onto the contaminated components, removing the surface layer including any contamination. A heavy duty steel slatted mill creates a continuous tumbling action to ensure complete coverage of the components in one cycle.

Typically 30 minutes will remove contamination from metal components to below required clearance levels whilst 10 minutes will be sufficient for concrete.

Cleaned off contaminants will be fed to collection bins and the dust created bagged in secure waste drums. These can then be disposed of in accordance with the relevant legislation.

The steel grit will be recycled within the machine via an airwash separator with a second magnetic particle separator and cleaned air returned to the room after passing through primary filters and an additional TROX air conditioner.

Lawson Pryke, technical director at Wheelabrator Group, said: “This abrasive blasting decontamination technique can be used to effectively reduce the amount of radioactive waste apparent with larger quantities of contaminated materials. The process produces fully decontaminated materials suitable for release, leaving a small amount of contaminated material in the form of dust, fines and paint residue, with reduced requirements for treatment and disposal.”

In 1996 the Wheelabrator Group demonstrated the effectiveness of using abrasive blasting as a decontamination technique at Belgoprocess in Belgium. Alternative waste and material management routes such as supercompaction and disposal are typically three times more expensive than dry abrasive blasting.

Mr Pryke said: “Abrasive blasting machines offer huge economic benefits and have added environmental advantages by effectively reducing slightly contaminated material to a state which allows disposal with no negative side effects. A large amount of material can also be released for recycling.”

JRC-Ispra opened in the early 1960s as part of a network of research centres located in different member states set up to provide customer-driven scientific and technical support for European Union policies, linking industry, universities and institutions as well as carrying out studies and experiments.

Contributing to the establishment and growth of nuclear power related industries, the Ispra site undertook research into reactor development and the fuel cycle. As the research progressed, a variety of additional experimental facilities, including reactors, hot cells, radiochemical plants and waste management stores were built.

Since the early 1980s, the European Commission has progressively reduced its focus on nuclear research and development at Ispra, instead expanding activity into food safety, genetically modified organisms, chemicals and the environment.

Mr Smith said: “With the global move away from nuclear facilities, the industry is faced with a large stock of potentially contaminated buildings and equipment. The need to comply with legislation governing decommissioning has driven the nuclear industry to review wider applications in the search for a solution.”