ARPANSA - Australian Radiation Protection and Nuclear Safety Agency

Lucas Heights Background Radiation

The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) has an on-going interest in assessing radiation exposure in the environment and in the workplace. The Agency maintains radiation measurement systems for the determination of radioactivity in soil, water, air, food and other materials, as well as within the body. Presently the Agency is studying the variability of the natural radiation background across Australia and is determining the baseline background levels at selected locations, including the suburbs around Lucas Heights, in the immediate area around the ports that host visits by nuclear powered warships and in regions with high levels of natural radiation. In October 2002 ARPANSA field teams were involved in two types of measurements in the suburbs close to Lucas Heights.

Mapping of Background Gamma-ray Radiation

The Health Physics Section from ARPANSA used a vehicle mounted gamma-ray spectroscopy system to measure the natural radiation in the suburbs within a 5 km radius of Lucas Heights. The measurement system could identify and quantify levels of naturally occurring and artificial gamma-ray emitting radioactivity within a 100 metre radius of the vehicle. The data was analysed to produce maps showing the variation of background radiation dose rate and the concentration of selected naturally occurring radionuclides (such as uranium, thorium and potassium).

Gamma mapping with the vehicle mounted system was carried out on 15 October 2002 in the Sydney suburbs of Engadine and Woronora Heights. Three preliminary maps of the variation of the gamma dose rate from the background radiation were produced using Mapinfo thematic mapping of the recorded data.

Woronora Heights gridded dose rate map 15 Oct 2002
Engadine gridded dose rate map 15 Oct 2002
Engadine dose map 15 Oct 2002
Engadine Menai Barden Ridge gamma dose rate map 30 Oct 2002
Engadine gridded dose map 16 Oct 2002

The measured dose rates were in the range 30 nanogray (nGy) per hour to 60 nGy per hour, which compares with an average value for background radiation dose rate of about 50 nGy per hour. That is, the values measured to date range from close to the Australian average value to about one half. The lower values possibly reflect the predominance of sandstone rock in the area. Sandstone has lower levels of uranium and thorium than other rock types such as granites and produce lower levels of background gamma radiation.

Analysis of Environmental Samples - Preliminary Results

Water samples:

Water samples were collected by ARPANSA teams and analysed in the ARPANSA laboratories. The results of the tests are summarised in Radioactivity Analysis Report for water samples (PDF 86kb)

The Australian Drinking Water Guidelines recommends screening value of 0.5 Bq/L for gross alpha and 0.5 Bq/L for gross beta (after subtraction of the contribution from potassium-40). The guideline values for Radium-228 and Radium-226 are both 0.5 Bq/L. All results from the analysis of the river water samples were below the recommended drinking water guideline values.

The sample collected below the causeway on the Woronora River was in a location that has some tidal influence and therefore the water was saline. The high salt content limits the detection of alpha particles by the gross alpha screening procedure. The gross beta in this sample is high due to the high level of the naturally occurring beta emitter, potassium-40, in the salt.

The values for tritium were below the detection limit of 20 Bq/L.

Definitions: Bq/L becquerel per litre. Top of Page