Remediation of Occupied Commercial Property Subject to Widespread Radium-226 Contamination: Update from WM2012 Paper - 16652

Amec Foster Wheeler was contacted by a company that managed commercial office space. High Rn-222 measurements had been observed throughout the facility and the landlord had been advised to commission a radiological survey of the site. The site had been purchased by the client in the 1990's. Initial desk studies found that the building had operated for around 50 years as a compass factory. Non-intrusive investigation identified widespread Ra-226 contamination. Ra-226 was found in the fabric of the building, in attic spaces, buried under floor boards and underlying car parks. Intrusive investigation was undertaken to estimate volume(s) of waste, waste categories, activity concentrations and the total inventory of radioactive materials on site. This work identified the presence of 180 GBq of Ra-226 on site. A programme of work is currently underway to remediate the site tackling areas posing the greatest risk to site occupants as a priority. We have worked closely with Regulators, our client, and tenants, to decontaminate the fabric of the building whilst areas of the building remain occupied. Early decontamination works identified that radon levels within the building were stubbornly high despite the removal of radium contamination. An independent radon source was suspected. A contaminated drain was discovered leading to a blocked-off river race running under the old mill building. A significant quantity of radium contaminated sludge was identified within the river race. This was believed to be the source of the excessive radon concentrations within the building. The paper will present work undertaken to investigate and remediate the inventory of sludge from beneath the building. It will describe the operational difficulties of working within a dynamic environment impacted by high dose rates, high radon concentrations, water ingress and waste retrieval challenges. The paper will present the radiological and environmental impacts of the work and detail the achieved end points. This was a challenging project working in confined spaces impacted by physical and radiological constraints. The remedial action undertaken significantly reduced radon concentrations in the building metres above the river race. It also significantly reduced the likelihood of radium contamination being mobilised into the river and the wider environment. The achieved end point permitted the building to return to uncontrolled commercial use. The end point achieved within the river race will ensure a safe working environment for future regular structural survey work. (authors)