ARPANSA scientists independently verified radiation levels at the Australian Nuclear Science and Technology Organisation's (ANSTO) Lucas Heights site in October 2021. Scientists collected freshwater, bore water, and soil samples in the nearby environment including sites at Little Forest and Woronora River.
Findings
ARPANSA’s results are generally consistent with ANSTO’s Monitoring Results.
ARPANSA also analysed duplicate environmental samples collected by ANSTO, in this case, groundwater samples from Little Forest. The radioactivity concentrations measured by ANSTO and ARPANSA were identical within natural experimental uncertainty.
The survey conducted by the ARPANSA team shows no indication of an abnormal release or significant change to the levels measured at the outset of the monitoring program, which began in 2019.
OPAL Reactor
The radioisotopes below are produced by ANSTO's OPAL Reactor. If measurements indicated that radiation was detected above investigation levels, ARPANSA would investigate and take relevant regulatory actions. These levels are very low compared to levels that would exceed dose limits. The gamma radiation detection equipment used by ARPANSA can accurately measure radioactivity at or above the minimum detectable activity (MDA) values. Values at or below the MDA indicates they are indistinguishable from background radiation. All measurements show levels below the MDA.
Table 1: ARPANSA gamma radiation measurement results compared to investigation level and minimum detectable activity.
| Radioisotope | Investigation level | Minimum detectable activity (MDA) | Results |
|---|---|---|---|
| (Bq/g) | (Bq/g) | ||
| Co-60 | 6.06E+01 | 6.74E+00 | <MDA |
| Mo-99 | 6.81E+02 | 5.45E+01 | <MDA |
| Tc-99m | 3.19E+04 | 5.59E+01 | <MDA |
| I-123 | 8.19E+03 | 5.19E+01 | <MDA |
| I-131 | 8.19E+01 | 2.38E+01 | <MDA |
| I-132 | 6.45E+03 | 1.39E+01 | <MDA |
| I-133 | 4.04E+02 | 1.71E+01 | <MDA |
| Cs-137 | 1.32E+02 | 1.61E+01 | <MDA |
Freshwater samples
ARPANSA scientists collected water samples from the Woronora River and a nearby creek to test for radioisotopes. The concentration of radioisotopes detected in the water are below the drinking water guideline values for any of the alpha or beta emitters of interest at the ANSTO site. The source of the radioactivity in the water samples is likely to be naturally occurring potassium (K40) that is migrating into the creek from rainfall and sediment movement.
Table 2: ARPANSA water sample measurement results compared with 2019 baseline value and drinking water guidelines.
| Sample | Drinking water guidelines | ARPANSA result (Bq/L) | ARPANSA baseline value 2019 |
|---|---|---|---|
| Downstream water sample | 1.0 Bq/L Alpha 0.50 Bq/L Beta |
0.02 Alpha 0.250 Beta |
0.026 Alpha 0.226 Beta |
| Midstream water sample | 1.0 Bq/L Alpha 0.50 Bq/L Beta |
0.02 Alpha 0.461 Beta |
N/A |
| Upstream water sample | 1.0 Bq/L Alpha 0.50 Bq/L Beta |
0.02 Alpha 0.205 Beta |
N/A |
Bore water samples
To confirm the accuracy of the Laboratory analysis, ANSTO provided duplicate water samples from two groundwater bores that were then analysed by ARPANSA. Both ANSTO and ARPANSA’s results show the levels are below the 10,000 becquerels per litre World Health Organization's (WHO) drinking water guideline values for Tritium in drinking water.
Table 3: ARPANSA sample analysis results compared with reference values and ANSTO results.
| Sample (groundwater bore) | Reference value | ANSTO result (Bq/L) | ARPANSA result (Bq/L) |
|---|---|---|---|
| Randomly selected bore water site 1 | 10,000 Bq/L | 3,040 +/- 24 | 3,060 +/- 120 |
| Randomly selected bore water site 2 | 10,000 Bq/L | 407 +/- 10 | 385 +/- 17 |
Conclusion
Overall, results showed no detectable gamma radiation from radioisotopes of interest and all water and soil measurements were below the drinking water guidelines values or investigation levels, respectively. The level of environmental exposure to radioisotopes produced by ANSTO's OPAL Reactor were found to be at background radiation levels, which means that the public's exposure to radiation at Lucas Heights is no more than at any other location where only background radiation is present.
These results indicate that ANSTO’s environmental controls are operating as expected at Lucas Heights. ARPANSA will continue to monitor and verify ANSTO’s environmental management as part of our ongoing regulatory oversight.
