ISO DIS 20042

Description / Abstract: This international standard describes methods to determine the activity in becquerel (Bq) of gammaemitting radionuclides by gamma spectrometry in solid, liquid or gaseous test samples after proper preparation in a testing laboratory. Applications include:

— routine surveillance of radioactivity released from nuclear installations or from sites discharging enhanced levels of naturally occurring radioactive materials;

— contributing to determining the evolution of radioactivity in the environment;

— investigating accident and incident situations, in order to plan remedial actions and monitor their effectiveness;

— assessing potentially contaminated waste materials from decommissioning legacy nuclear sites;

— surveillance of radioactive contamination in media such as soils, foodstuffs, potable water, groundwaters, seawater or sewage sludge;

— measurements for estimating the intake (inhalation, ingestion or injection) of activity of gammaemitting radionuclides in the body.

It is assumed that the user of this standard has been given information on the composition of the test sample (or the site). In some cases, the radionuclides for analysis may also have been specified if characteristic limits are required. It is also assumed that the test sample has been homogenised and is representative of the material under test.

General guidance is included for preparing the samples for measurement. However, some types of sample are to be prepared following the requirements of specific standards referred to in this document. The generic recommendations can also be useful for the measurement of gamma emitters in situ.

This standard includes generic advice on equipment selection (a list of factors to be considered) (more detailed information is included in Annex A), detectors (more detailed information is included in Annex D), and commissioning of instrumentation and method validation. The informative Annex F summarises the influence of different measurement parameters on results for a typical gamma spectrometry system. Quality control and routine maintenance are also covered, but electrical testing of the detector and pulse processing electronics is excluded. It is assumed that any data collection and analysis software used has been written and tested in accordance with relevant software standards such as ISO/IEC 12207.

Calibration using reference materials and/or numerical methods is covered, including verification of the results. It also covers the procedure to estimate the activity content of the sample (Bq) from the spectrum. The procedure for the measurement of gamma emitting radionuclides in situ is covered in ISO 18589-7 and is outside the scope of this document.

The standard covers, but is not restricted to, gamma emitters which emit photons in the energy range of 5 keV to 3000 keV. However, the most measurements fall into the range 40 keV to 2 000 keV. The activity (Bq) ranges from the low levels (sub-Bq) found in environmental samples to activities found in accident conditions and high level radioactive wastes.