An assay on the effect of preliminary restoration tasks applied to a large TENORM wastes disposal in the south-west of Spain J.L. Mas a , E.G. San Miguel b , J.P. Bolívar b, ⁎ , F. Vaca b , J.P. Pérez-Moreno b a Dpto Física Aplicada I, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012-Sevilla, Spain b Dpto Física Aplicada, Universidad de Huelva, Facultad de Ciencias Experimentales, 21071-Huelva, Spain Received 28 July 2005; received in revised form 27 October 2005; accepted 3 November 2005 Available online 15 December 2005 Abstract A large industrial wastes disposal site, where two phosphate rock processing plants release their wastes, located close to Huelva town (SW of Spain), has been partially submitted to restoration as a preliminary step in a possible decomissioning process. Due to the high natural radioactivity contents of these wastes, this repository is considered as a radiological anomaly, being actually considered as TENORM (technically enhanced naturally occurring radioactive materials). The efficiency of this restoration from the radiological point of view according to the new European regulatory framework was evaluated in this work. The results allow to conclude that, as a consequence of the partial restoration works, the external dose rate has been drastically reduced above the repository system. Nevertheless, special attention must be paid on the occupational factor to be applied to workers on the unrestored system. The application of a dosimetric model allows the prediction of the negative effects of using certain industrial wastes as a cover system in this restoration/mitigation task. © 2005 Elsevier B.V. All rights reserved. Keywords: Phosphogypsum; Th-isotopes; U-isotopes; Ra-isotopes; Radiation protection; NORM; Phosphate rock processing plants 1. Introduction The situation of many industries and their associated wastes involved in the management of NORM (natu- rally occurring radioactive materials) has to be evaluated to guarantee the safety of the population (non-occupa- tionals) and workers (occupationals). NORM is defined as all naturally occurring radioactive materials where human activities have increased the potential risk for radiation exposure in comparison to the unaltered situation (Betti et al., 2004). This fact results especially clear after the introduction of the EURATOM'96/29 European Directive, which has been adapted to the Spanish law framework through the RD 783/2001 order. In this normative, the annual dose limit for population (non-occupationals) and workers (occupationals) are 1 mSv and 10 mSv, respectively. A well-known example of NORM-related processes is that of the facilities devoted to the production of phosphate fertilizers. These are manufactured from phosphate rock, which contains high concentrations of radionuclides from 238 U-series (Guimond and Hardin, 1989; Barisic et al., 1992; Rutherford et al., 1994). The 238 U concentration in phosphate rock is up to 100 times higher than in the average United Nations soil (UNSCEAR, 2000). Science of the Total Environment 364 (2006) 55 – 66 www.elsevier.com/locate/scitotenv ⁎ Corresponding author. Tel.: +34 959219793; fax: +34 959219777. E-mail address: bolivar@uhu.es (J.P. Bolívar). 0048-9697/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2005.11.006