Development of a methodology for assessing radiological dose due to use of NORM sludge as fertilizer.

In Europe, the general obligation to recycle drives for increased reuse of residues containing Naturally Occurring Radioactive Material (NORM). In agriculture, this has led to the reuse of sludge produced by groundwater filtration facilities as a means of fertilization. In the frame of the RadoNorm project, a methodology was developed for dose assessment of agricultural workers and other members of the public living near agricultural fields in which NORM-containing sludge is applied. Appropriate exposure scenarios were identified and modelled for each relevant NORM decay segment of both U-238 and Th-232 series, as well as for K-40. Dose assessments were performed using the software RESRAD-ONSITE with dose coefficients for external and internal exposure taken from the latest publications from the International Commission on Radiological Protection (ICRP). The objective was to develop a generic methodology to quantify exposure and to obtain screening values - so-called Operational Levels (OLs). These OLs pertain to the activity concentration of natural radionuclides (in terms of kBq kg-1) present in sludge that is reused in agriculture, for which dose criterion of 1 mSv year-1 is complied with. OLs can be used as screening tools by an authority/operator, even non-experts in the field of radiation protection. Results showed that the most critical decay segments are Ra-226+ and Ra-228+, for which OLs of the order of 1 kBq kg-1 were estimated. For all the other radionuclides, the calculated OLs are much higher than the activity concentrations typically found in sludge from water treatment facilities, and the radiological impact expected is well-below 1 mSv year-1. The methodology and results of this study could contribute to the update of the Clearance Levels and discharge levels reported in the European guidelines RP 122 Part II and RP 135, respectively.

Tools for harmonized data collection at exposure situations with naturally occurring radioactive materials (NORM).

Naturally occurring radioactive materials (NORM) contribute to the dose arising from radiation exposure for workers, public and non-human biota in different working and environmental conditions. Within the EURATOM Horizon 2020 RadoNorm project, work is ongoing to identify NORM exposure situations and scenarios in European countries and to collect qualitative and quantitative data of relevance for radiation protection. The data obtained will contribute to improved understanding of the extent of activities involving NORM, radionuclide behaviours and the associated radiation exposure, and will provide an insight into related scientific, practical and regulatory challenges. The development of a tiered methodology for identification of NORM exposure situations and complementary tools to support uniform data collection were the first activities in the mentioned project NORM work. While NORM identification methodology is given in Michalik et al., 2023, in this paper, the main details of tools for NORM data collection are presented and they are made publicly available. The tools are a series of NORM registers in Microsoft Excel form, that have been comprehensively designed to help (a) identify the main NORM issues of radiation protection concern at given exposure situations, (b) gain an overview of materials involved (i.e., raw materials, products, by-products, residues, effluents), c) collect qualitative and quantitative data on NORM, and (d) characterise multiple hazards exposure scenarios and make further steps towards development of an integrated risk and exposure dose assessment for workers, public and non-human biota. Furthermore, the NORM registers ensure standardised and unified characterisation of NORM situations in a manner that supports and complements the effective management and regulatory control of NORM processes, products and wastes, and related exposures to natural radiation worldwide.

A methodology for the systematic identification of naturally occurring radioactive materials (NORM).

Naturally occurring radioactive materials (NORM) are present worldwide and under certain circumstances (e.g., human activities) may give radiation exposure to workers, local public or occasional visitors and non-human biota (NHB) of the surrounding ecosystems. This may occur during planned or existing exposure situations which, under current radiation protection standards, require identification, management, and regulatory control as for other practices associated with man-made radionuclides that may result in the exposure of people and NHB. However, knowledge gaps exist with respect to the extent of global and European NORM exposure situations and their exposure scenario characteristics, including information on the presence of other physical hazards, such as chemical and biological ones. One of the main reasons for this is the wide variety of industries, practices and situations that may utilise NORM. Additionally, the lack of a comprehensive methodology for identification of NORM exposure situations and the absence of tools to support a systematic characterisation and data collection at identified sites may also lead to a gap in knowledge. Within the EURATOM Horizon 2020 RadoNorm project, a methodology for systematic NORM exposure identification has been developed. The methodology, containing consecutive tiers, comprehensively covers situations where NORM may occur (i.e., minerals and raw materials deposits, industrial activities, industrial products and residues and their applications, waste, legacies), and thus, allows detailed investigation and complete identification of situations where NORM may present a radiation protection concern in a country. Details of the tiered methodology, with practical examples on harmonised data collection using a variety of existing sources of information to establish NORM inventories, are presented in this paper. This methodology is flexible and thus applicable to a diversity of situations. It is intended to be used to make NORM inventory starting from the scratch, however it can be used also to systematise and complete existing data.