Evaluation and Potential Remediation of the Industrial Norm Legacy in Liverpool

Sefton, on the north side of Liverpool, holds a radioactive legacy from its industrial past. This legacy is in the form of Tin slag buried in sub-surface seams. Located near the docks and adjacent to the rich Lancashire coal seams, Sefton became one of the main production centres of Tin plate in Britain. A consequence of this industrial process is the production of mildly radioactive waste slag. Tin rich ores are heated under reducing conditions to produce a molten metal stream This is then separated into the component metal streams. Solid wastes produced by this process are known as slag and were usually stored on site in spoil heaps. Because this slag is a very hard, glassy material it has been historically used as aggregate in underlying roads and rail way sleepers. Many of these sites pre-date the introduction of the regulation of radioactive substances in the UK and have never been under legislative control under the Radioactive Substances Act, RSA93. There is a risk that the existence may not be known of some of these sites. U-238 and Th-232 and their associated decay chains, are the major contributors to the radionuclide inventory of the slags, levels of these radionuclides being in the range 1–10Bq/g. A series of alpha and beta decays for both chains leads eventually to the generation of a stable isotope of lead. Radiologically, the main area of concern is with the potential inhalation or ingestion of contaminated dusts. There is also a potential for Ra-226 to leach out into groundwater. AMEC has worked for Sefton Metropolitan Council and various developers, to carry out specialist, non intrusive gamma radiation surveys of numerous sites in Sefton. This is the first stage in carrying out a radiological risk review of a given site. What often then follows is an intrusive, geo-technical survey, with trial pitting and radiological sampling for later sensitive lab based radiochemical analysis. Radiological supervision is also required at this time to ensure that the radiological exposure of the Contractors carrying the survey is restricted and ensure that plant dose not become contaminated with radionuclides. These surveys are the preliminary stage for redevelopment works with new housing replacing antiquated commercial premises. By bringing together expertise in sensitive gamma surveying, radiochemical analysis and a detailed understanding of the regulatory framework, AMEC is able to support the borough of Sefton in its re-development programme ensuring safe compliant development of an area with an historic radiological legacy.