ABSTRACT
Accurate measurement of naturally occurring radionuclides in blast furnace slag, a by-product of the steel industry, is required for compliance with building regulations where it is often used as an ingredient in cement. A matrix reference blast furnace slag material has been developed to support traceability in these measurements. Raw material provided by a commercial producer underwent stability and homogeneity testing, as well as characterisation of matrix constituents, to provide a final candidate reference material. The radionuclide content was then determined during a comparison exercise that included 23 laboratories from 14 countries. Participants determined the activity per unit mass for 226Ra, 232Th and 40K using a range of techniques. The consensus values obtained from the power-moderated mean of the reported participant results were used as indicative activity per unit mass values for the three radionuclides: A0(226Ra) = 106.3 (34) Bq·kg-1, A0(232Th) = 130.0 (48) Bq·kg-1 and A0(40K) = 161 (11) Bq·kg-1 (where the number in parentheses is the numerical value of the combined standard uncertainty referred to the corresponding last digits of the quoted result). This exercise helps to address the current shortage of NORM industry reference materials, putting in place infrastructure for production of further reference materials.
ABSTRACT
In northern Estonia, higher levels of Ra-226 and Ra-228 concentrations give rise to problems with water treatment plants (WTPs) using Cambrian-Vendian (Cm-V) aquifer. During water treatment processes, radionuclides accumulate in the filter material to a level where the material could be classified as a radioactive material. In order to understand the scope of the problem, a nation-wide survey was carried out among the Cm-V fed treatment plants. Filter material and water samples were collected from 18 Estonian WTPs to analyse the activity concentration of Ra-226 and Ra-228 in filter materials and also the radium treatment efficiency was determined. Sixteen WTPs exceeded the exemption levels of 1 kBq * kg-1 set by the EC directive 2013/59/Euratom. The quantity of filter material exceeding the exemption levels was approximately 300 tons, average concentrations values for Ra-226, Ra-228 and Th-228 were, accordingly, 7.6 kBq * kg-1, 8.0 kBq * kg-1 and 5.6 kBq * kg-1. That includes WTPs not designed for radium removal. The results suggest a need to investigate further NORM generation in WTPs, as uncontrollable disposal of NORM may occur.
