Environmental Science & Research - AnalyticalServices

By: Environmental Science & Research  06-Dec-2011
Keywords: General Information, Environmental Radioactivity

In this section:

General information

The NRL maintains a specialised environmental radiochemistry laboratory dedicated to low-level radioactivity measurements and capable of providing a wide range of analytical services to clients.  The laboratory has achieved accreditation for ISO 17025 for most of our testing services (please contact us for details).  Analytical services include the measurement of radionuclides in:

  • foodstuffs, consumer goods and manufactured goods
  • soil, sediment and non-biological solids
  • biological solids
  • drinking waters and other water samples
  • petrochemical and fertiliser industry samples (NORM and TENORM)
  • atmospheric particulate

Other services provided by the Environmental laboratory include:

  • certification of radioactivity levels in foodstuffs
  • provision of advice on matters concerning radioactivity in the environment
  • environmental radioactivity monitoring, radiation surveys and sampling
  • wipe testing for radioactive contamination

The Environmental laboratory maintains a fully equipped radiochemical laboratory essential for the analysis of radionuclides emitting alpha and beta radiations, such as thorium isotopes and some fission products, and for the processing of all samples for analysis.

  • alpha radiation detection (low-background, liquid scintillation detector)
  • alpha spectroscopy (six high-resolution detectors)
  • beta radiation detection (solid-state scintillation detectors and a low-background, liquid scintillation detector)
  • gamma ray spectroscopy (eight high-resolution detectors)
  • portable radiation detection equipment for use in surveys.

For further information contact the NRL's Environmental Laboratory.

Quality assurance is an essential feature of any measurement laboratory's operation.  To set its procedures in a verifiable context the environmental laboratory has strived for and achieved accreditation to the international standard ISO 17025.

ISO 17025 addresses the general requirements for the competence of testing and calibration laboratories. It is designed to assure accuracy of testing results and calibrations. During an audit a quality systems auditor and a technical expert verify, among other aspects, that staff is qualified, the accommodation of the laboratory is adequate for the purpose and that scientific methods are of international standard. Test reports endorsed with the logo of International Accreditation New Zealand give clients the confidence that test results are accurate.

Traceability: Full traceability to appropriate national or international standards is maintained.

Laboratory Intercomparisons are one way to verify that results are accurate. The Environmental laboratory has for many years participated in international analytical intercomparisons performed by agencies in other countries including the CTBTO, WHO, IAEA, and the EPA.

When reporting a result we are confident that it is an accurate estimate of the ‘true’ activity and the quoted uncertainty is a realistic estimate of the actual uncertainties inherent in the measurement.  We ensure that:

  • equipment is in good working order
  • nuclear data are valid
  • calibration standards are fit for the purpose and connected by an uninterrupted chain of comparisons to primary standards.

Unit of measurement: The SI unit for the measurement of radioactivity is the Becquerel (Bq).  This is equivalent to one nuclear transformation per second.  A concentration of a particular radionuclide is given in Becquerel per unit volume or mass (eg, Bq kg-1).

Concentration and Uncertainty: If the measured value is above background at a level of confidence of 95%, then the concentration of the radionuclide is reported.  The reported uncertainty is based on the combined standard uncertainty (uc) multiplied by a coverage factor (k) = 2 (providing a level of confidence of 95%) as described in the Guide to the expression of uncertainty in measurement, International Organization for Standardization, Geneva, 1995.

Minimum Detectable Concentration: Reporting of a ‘less than’ result means that the measured value was consistent with a background measurement.  The minimum detectable concentration with a level of confidence of 95% for errors both of the first and second kind is calculated as described in: Analytical chemistry 40(3):586-593, 1968.  (L A Currie.  Limits for qualitative detection and quantitative determination: application to radiochemistry.)

For further information contact the NRL's Environmental Laboratory.

Total Alpha and Beta Concentration is useful for inexpensive and rapid scanning of overall radioactivity levels in samples without ascertaining the actual radionuclide present.  However, when isotopes need to be identified and their concentrations established, gamma spectrometry or radiochemical analysis followed by alpha spectrometry or liquid scintillation counting may be required.

Listed below is the radioactivity detection equipment adapted particularly for low-level, environmental measurements.

Gamma Ray Spectrometry

: this high resolution (<3 keV Full Width Half Maximum) method can be used as a non-destructive technique with minimal sample preparation.  The technique often requires large volumes (>100 m

) because of low counting efficiencies (1 to 25%).

Alpha Spectrometry

: very low background levels with counting efficiencies of about 25%.  A pure and thin source must be prepared requiring labour intensive radiochemical isolation and purification procedures.  It is commonly used for the determination of polonium-210, plutonium-238, plutonium-239+240, radium-226, uranium and thorium radionuclides.

Solid Beta Scintillation Counting: low background levels with counting efficiencies of about 45%.  This instrument, built at the National Radiation Laboratory, is exclusively used for the determination of strontium-90 where maximum sensitivity is required.

Liquid Scintillation Counting

: low background levels with counting efficiencies ranging from 30 to 400%.  This instrument is used for




and for the determination of tritium, radium-226, radon-222 and strontium-90.

Field measurements: the NRL operates a range of field-operated instruments (based on GM counters and NaI spectrometers) to assess contaminated sites and to monitor naturally occurring gamma radiation.

For further information contact the NRL's Environmental Laboratory.

Soil, sediment and solids

This includes almost all non-biological solids such as soil, sediment, rock, solid effluent and gypsum.

The Laboratory has had a long history in measuring radionuclides in soil to ascertain rates of erosion, and in sediment for geochronology studies.  Materials such as gypsum and phosphate fertilisers have also been analysed to determine their naturally occurring radionuclide content.

Naturally occurring radionuclides such as radium-226 and lead-210, cosmogenically produced beryllium-7, and fallout caesium-137 are commonly measured in these matrices, but other gamma-active radionuclides can be measured on request.

The NRL offers a service to determine the radiological content of drinking water from New Zealand and around the world. Test results can be used to show compliance with radiological sections of regulatory requirements or standards.

Drinking-Water Standards for New Zealand 2005

Overseas regulations and standards

For further information contact the NRL's Environmental Laboratory.

There are a large variety of water samples that can be processed by the Laboratory such as drinking water, groundwater and effluent wastes.

Water sample commonly assessed range from potassium-40 in groundwater to Naturally Occurring Radionuclide Materials in tailing dam waters from the mining industry.

Samples such as those with high levels of suspended matter, dissolved organic and inorganic substances, or biological or chemical toxins may be analysed by an agreed protocol following consultation.

For further information contact the NRL's Environmental Laboratory.

A large range of foodstuffs and biological samples are routinely monitored for radioactivity content, including:

  • fresh and powdered milk
  • dairy products
  • fresh and dried meats, fish, shell fish
  • confectionery and beverages (see drinking water)
  • bone, plant material, wood, marine biota, etc.

Caesium-137 and caesium-134 are commonly measured in foodstuffs and biological samples.  Other radionuclides can be measured on request.

For foodstuffs, a rapid screening technique is offered that assures a minimum detectable concentration of less than 5 Bq kg-1 for caesium-137 for a minimum sample size of 0.50 kg.

For further information contact the NRL's Environmental Laboratory.

Wipe tests to check for possible radioactive contamination of surfaces are required by radiation protection legislation in certain circumstances, or are sometimes undertaken when contamination is suspected, such as when a radioactive source is inadvertently dropped.

The kit contains two differently shaped wipes (a pad and a sterile bud) to allow wiping on all kinds of surfaces even in restricted areas.  Impervious gloves are provided to ensure protection of the operator.  Once completed, the supplied data sheet and sample are sent to the NRL for analysis using the prepaid envelope provided.

The testing service is accredited to ISO 17025.

For further information contact the NRL's Environmental Laboratory.

Keywords: Environmental Radioactivity, General Information,

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