The main purpose of the current programme is to monitor artificial radioactivity. However, the naturally occurring radioactive materials beryllium-7 and lead‑210 are also monitored for comparative and scientific purposes.
- Atmospheric testing stations at Kaitaia, Chatham Island and Rarotonga use a SENYA “Snow White” air sampler to draw air through 2025 cm2 filters (3M filter, polypropylene BMF) at a flow rate of approximately 900 m3/hour, with a daily sample volume of approximately 20,000 m3.
- High-resolution gamma spectrometry (Canberra high-purity n-type germanium BEGE5030 detector) analyses the samples for gamma-emitting artificial and natural radionuclides.
- Samples are also collected at Baring Head and analysed for the presence of carbon-14.
- Rainwater samples are collected weekly at Hokitika (small-area rain collector, 0.021 m2) and analysed for total beta content by liquid scintillation counting.
- A large-area collector (area 1m2) is equipped for on-site continuous ion-exchange operation to increase sensitivity for artificial radionuclides.
- Beryllium-7 measurements are used as a quality control for the performance of the sampling system.
- Rainwater samples are also collected at Kaitoke and analysed for the presence of hydrogen-3.
Milk powder testing
- Milk powder samples are analysed monthly using gamma spectrometry to measure Iodine-131, caesium-134 and caesium-137 concentrations.
- The samples are sourced from three regions: Waikato, Taranaki and Westland.
- Seawater samples are collected from the Canterbury coast and analysed using gamma spectrometry for Cs-134 and Cs-137. This commenced in 2015 and the testing program is expected to expand over coming years.
- There is a continuing trend of decreasing radioactivity in our environment. Full details are provided on the Environmental radioactivity annual reports page
- Concentrations of artificial radionuclides in the atmosphere are well below detection limits, which are in the range of 1 to 5 mBq/m3 for iodine-131, caesium-134 and caesium-137.
- Natural beryllium-7 continues to be the most significant radionuclide detected on the air filters.
- Beta-activity in rainwater is almost entirely due to naturally occurring radionuclides, such as potassium-40 and lead-210.
- There is a continuing trend of reducing radioactivity concentrations in milk powder, with caesium-137 being the only detectable artificial radionuclide.
- No evidence of radioactive contamination from the Fukushima Daiichi nuclear accident has been observed in the New Zealand environment. Further details on the Fukushima Daiichi accident is available on the next page