Review of NORM occurrence and application of a tailored graded approach for the radiation protection in geothermal plants

In the present paper, the general methodological approach developed to manage legislative requirements for NORM involving industries was fitted to the geothermal industrial sector, which is in the indicative list of the European Directive 2013/59/Euratom (EU-BSS). A review of the state of the art about the radiological characterization of NORM in geothermal plants have been performed with the aim to identify matrices and exposure scenarios of radiological concern. From the analysis of collected data, it results that radiological content of NORM residues generally depends on the characteristics of the geothermal fluid as well as on the type of the plants. In several plants, residues (both scales and filtering materials) show generally high activity concentrations, especially for Ra-226 and Ra-228 decay segments, exceeding Exemption Levels of the EU-BSS. Several tables have been presented as tools to support the stakeholders in the application of the legislative requirements regarding radiation protection in the geothermal sector.