Introduction

Radioactivity from several naturally-occurring and anthropogenic sources is present throughout the environment. Thus, water bodies (e.g. surface waters, ground waters, sea waters) can contain radionuclides of natural, human-made, or both origins.

— Natural radionuclides, including ⁴⁰K, ³H, ¹⁴C, and those originating from the thorium and uranium decay series, in particular ²²⁶Ra, ²²⁸Ra, ²³⁴U, ²³⁸U, and ²¹⁰Pb, can be found in water for natural reasons (e.g. desorption from the soil and washoff by rain water) or can be released from technological processes involving naturally occurring radioactive materials (e.g. the mining and processing of mineral sands or phosphate fertilizer production and use).
— Human-made radionuclides, such as transuranium elements (americium, plutonium, neptunium, curium), ³H, ¹⁴C, ⁹⁰Sr, and gamma emitting radionuclides can also be found in natural waters. Small quantities of these radionuclides are discharged from nuclear fuel cycle facilities into the environment as the result of authorized routine releases. Some of these radionuclides used for medical and industrial applications are also released into the environment after use. Anthropogenic radionuclides are also found in waters as a result of past fallout contaminations resulting from the explosion in the atmosphere of nuclear devices and accidents such as those that occurred in Chernobyl and Fukushima.

Radionuclide activity concentration in water bodies can vary according to local geological characteristics and climatic conditions and can be locally and temporally enhanced by releases from nuclear installation during planned, existing and emergency exposure situations^[⁷^]. Drinking water may thus contain radionuclides at activity concentrations which could present a risk to human health.

The radionuclides present in liquid effluents are usually controlled before being discharged into the environment^[⁸^]. Water bodies and drinking waters are monitored for their radioactivity content as recommended by the World Health Organization (WHO)^[⁹^] so that proper actions can be taken to ensure that there is no adverse health effect to the public. Following these international recommendations, national regulations usually specify radionuclide authorized concentration limits for liquid effluent discharged to the environment and radionuclide guidance levels for water bodies and drinking waters for planned, existing and emergency exposure situations. Compliance with these limits can be assessed using measurement results with their associated uncertainties as specified by ISO/IEC Guide 98‑3 and ISO 5667‑20.

Depending on the exposure situation, there are different limits and guidance levels that would result in an action to reduce health risk. As an example, during a planned or existing situation, the WHO guidelines for guidance level in drinking water is 10 Bq·l⁻¹ for ^134/137Cs and ¹³¹I activity concentration, 1 Bq·l⁻¹ for ²⁴¹Am and 0,1 Bq·l⁻¹ for ²¹⁰Pb.

NOTE 1 The guidance level is the activity concentration with an intake of 2 l/d of drinking water for one year that results in an effective dose of 0,1 mSv/a for members of the public. This is an effective dose that represents a very low level of risk and which is not expected to give rise to any detectable adverse health effects^[⁹^].

In the event of a nuclear emergency, the WHO Codex guideline levels^[¹⁰^] mentioned that the activity concentration for infant food might not be greater than 1 000 Bq·kg⁻¹ for ^134/137Cs, 100 Bq·kg⁻¹ for ¹³¹I and 1 Bq·kg⁻¹ for ²⁴¹Am. For food other than infant food, the activity concentration might not be greater than 1 000 Bq·kg⁻¹ for ^134/137Cs, 100 Bq·kg⁻¹ for ¹³¹I and 10 Bq·kg⁻¹ for ²⁴¹Am.

NOTE 2 The Codex guidelines levels (GLs) apply to radionuclides contained in food destined for human consumption and traded internationally, which have been contaminated following a nuclear or radiological emergency. These GLs apply to food after reconstitution or as prepared for consumption, i.e. not to dried or concentrated food, and are based on an intervention exemption level of 1 mSv in a year for members of the public (infant and adult)^[¹⁰^].

Thus, the test method can be adapted so that the characteristic limits, decision threshold, detection limit and uncertainties ensure that the radionuclide activity concentrations test results can be verified to be below the guidance levels required by a national authority for either planned/existing situations or for an emergency situation^[¹¹^][¹²^].

Usually, the test methods can be adjusted to measure the activity concentration of the radionuclide(s) in either wastewaters before storage or in liquid effluents before discharge to the environment. The test results will enable the plant/installation operator to verify that, before their discharge, wastewaters/liquid effluent radioactive activity concentrations do not exceed authorized limits.

The test method described in this document may be used during planned, existing and emergency exposure situations as well as for wastewaters and liquid effluents with specific modifications that could increase the overall uncertainty, detection limit, and threshold.

The test method may be used for water samples after proper sampling, sample handling, and test sample preparation (see the relevant part of the ISO 5667 series).

This document has been developed to answer the need of test laboratories carrying out these measurements, that are sometimes required by national authorities, as they may have to obtain a specific accreditation for radionuclide measurement in drinking water samples.

This document is one of a set of International Standards on test methods dealing with the measurement of the activity concentration of radionuclides in water samples.

BS EN ISO 10703:2021

Water quality. Gamma-ray emitting radionuclides. Test method using high resolution gamma-ray spectrometry

Current

Published:

31 Jul 2021