Remediation of Sites Contaminated With Depleted Uranium in South Africa

Abstract

Like many other countries, South Africa embarked on a project involving the development of depleted uranium armour piercing ammunition during the 1980’s. Several weapon systems were tested on two proof ranges in the Northern Cape region of South Africa. These tests were conducted up to 1989 when a decision was taken to terminate the project. NECSA was contracted for the radiological clean up of these sites contaminated with depleted uranium (DU), which became a priority since 1997. The project, which was completed in 2002, was a first of its kind in South Africa and, even internationally, a unique operation. A phased approach was followed for the preparatory and clean-up activities. The first part of the presentation covers the development and planning phases of the project with particular reference to: • Introduction and typical radiological characteristics of depleted uranium weapons proof ranges. • Problem definition – extent of site contamination and site characteristics. • Development of the clean-up strategy for the sites. The second part of the presentation covers the various phases implemented for the clean up of the respective sites with specific reference to the on-site operations and methodology, radiation protection control measures, problems encountered and findings during various phases of the operation. The respective clean-up phases were the following: • Removal of surface contamination. This meant collection of objects from the surfaces of the strata identified in the radiological surveys performed on the respective sites. • Extended surface clean-up operation. This operation became eminent after a report, modelling trajectory paths, indicated that DU fragments could be expected outside the areas covered by the original site surveys. An area of ± 6 million m2 was covered by the extended clean up operation. • Contaminated metal clean-up operation. Metal target plates contaminated with entrapped uranium penetrators or layers of surface contamination had to be processed and removed from the sites. • Volume reduction by performing the following steps: * Collection of contaminated soil from the identified strata. A total of ± 35000-m3 soil was collected and stockpiled during this operation on the respective sites. * Mechanical screening of the collected soil to fractionate the DU penetrator remains into different size fractions. * Radiological screening of the soil containing the various size fractions to remove the uranium metal particles. • Radioactive waste management. The contaminated material and DU had to be removed from the sites and disposed of. Various routes were employed to execute this phase. • Materials and site clearance. Throughout each phase of the total clean-up operation radiation protection control measures were implemented based on prospective hazard assessments. The measures were further applied in such a way as to minimize exposures. At no stage did the actual exposures exceed the exposures estimated for each phase. The project was finally completed and cleared by the National Nuclear Regulator in July 2002.