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, ²¹⁰Po and ²¹⁰Pb can be found in water for natural reasons (e.g. desorption from the soil and wash off 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 fertilizers production and use);
— Human-made radionuclides such as transuranium elements (americium, plutonium, neptunium and curium), ³H, ¹⁴C, ⁹⁰Sr, and some gamma emitting radionuclides can also be found in natural waters. Small quantities of these radionuclides may be 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 the 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^[¹^]. 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^[²^] and water bodies. Drinking waters are monitored for their radioactivity as recommended by the World Health Organization (WHO)^[³^] 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 waterbodies 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 requested by ISO/IEC Guide 98‑3 and ISO 5667‑20^[⁴^].

Depending of the exposure situation, there are different limits and guidance levels that would result in an action to reduce health risk.

NOTE 1 The guidance level is the activity concentration with an intake of 2 ld^-1 of drinking water for one year, that results in an effective dose of 0,1 mSva^-1 for members of the public. This is an effective dose that represents a very low level of risk that is not expected to give rise to any detectable adverse health effect^[³^].

In the event of a nuclear emergency, the WHO Codex Guideline Levels^[⁵^] indicates the activity concentrations corresponding to operational intervention levels.

NOTE 2 The Codex guidelines levels (GLs) apply to radionuclides contained in foods 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 foods, and are based on an intervention exemption level of 1 mSv in a year for members of the public (infant and adult)^[⁵^].

Thus, the test method can be adapted so that the characteristic limits, decision threshold and detection limit, and the uncertainties ensure that the radionuclide activity concentration test results can be verified to be below the guidance levels required by a national authority for either planned-existing situations or an emergency situation^[⁶^][⁷^].

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 being discharged 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 methods described in this document for emergency exposure situations may also be used during planned, existing exposure situations as well as for wastewaters and liquid effluents with specific modifications that could change the overall uncertainty, detection limit, and threshold.

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

This document has been developed to answer the need of test laboratories carrying out these measurements that may be required by national authorities during a nuclear or radiological emergency exposure situation.

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.

The ISO documents produced for radioactivity measurements in water are detailed methods. In most cases, these methods have been used in laboratory practice for a number of years and the analytical characteristics have been documented. However, these methods are generally time consuming and require well trained analysts to carry them out.

Over the last years, an increasing need was recognized for the addition of guidance on the use of so-called “rapid methods”. The nuclear accident at Fukushima in March 2011 accentuated the need for these rapid measurements. During the initial stages of such incidents, decision makers had to deal with taking protective measures for the population, such as sheltering, evacuation, and the distribution of iodine prophylaxis. It has been found that time is critical and limited for taking these protective measures.

BS EN ISO 22017:2020

Water quality. Guidance for rapid radioactivity measurements in nuclear or radiological emergency situation

Current

Published:

30 Sep 2020