New Test Method for Detection of Anthropogenic Alpha and Beta Radioactivity in Food by Liquid Scintillation and Gas-flow Proportional Counting
1. Scope
This method is versatile in detecting alpha and beta radioactivity in food, encompassing the following aspects:
1) Mineralization of food through either wet or dry ashing techniques
2) Adaptability to liquid scintillation counting (LSC) and gas-flow proportional counting (GPC)
3) Detection of multiple alpha- and beta-emitting radionuclides, including 241Am, 238Pu, 239Pu, 240Pu, 243Cm, 244Cm, and 90Sr
4) Applicability to various types of foods, such as grain, vegetable, meat, dairy, and complex meal
5) Simultaneous detection of alpha and beta radioactivity in a sample through a single measurement.
This method is intended for analyzing foods with matrix compositions like those tested in the method development and validation study. If the method is to be used for analyzing a sample that has not been tested before, it is advisable to demonstrate its applicability by using a representative sample with a similar matrix composition.
To obtain reliable analytical results, the analyte radionuclides in food needs to be soluble in nitric acid. If there is indication of refractory form radionuclides being present in the food, an alternative digestion procedure should be applied to completely solubilize the analyte.
This method can be used to detect either a single radionuclide or a group of radionuclides, depending on the radionuclides found in the sample. For the detection of sample beta activity, specifically 90Sr, it is crucial for both 90Sr and its progeny 90Y to be in radioactive equilibrium at the time of sample analysis. The sample alpha activity, however, is determined as the total activity if multiple alpha-emitting analyte radionuclides are known to present in the sample. The alpha-emitting radionuclides detectable by this method include 241Am, 238Pu, 239Pu, 240Pu, 243Cm, and 244Cm.
As the recovery of analyte radionuclides can't be determined for the sample being tested without using an in-situ yield monitor, it is necessary to apply typical analyte recovery in the calculation of sample alpha and beta activity, which highlights the importance of maintaining consistent analyte recovery for all the samples being analyzed.
Based on the analysis of various types of foods, it was observed that the method can provide results within ±30% of the known value. The minimum detection limits for beta and alpha activity are found to be ~0.9 Bq/kg and ~0.6 Bq/kg, respectively, when analyzing ~35 grams of food with 60-min sample count time.
Keywords
radiochemistry, radioanalysis, food
Rationale
There will be enormous demand for radiological food testing in the event of nuclear emergency. Rapid detection is vital to reassure the public about food safety in the early phase of an incident. High demand for food testing can last for many years. Many confirmatory methods for the analysis of alpha and beta emitting radionuclides in foods take days to produce a result. This method is intended for any organization that needs to rapidly screen/triage a large amount of potentially contaminated food products for certain alpha and beta emitting radionuclides following a nuclear event to determine which samples require further confirmatory analyses.
This method allows for the use of two different mineralization procedures to convert food samples into a solution for extracting analyte radionuclides. Wet ashing is a suitable option when time-sensitive and expedited analysis is required. Dry ashing, on the other hand, is used to support high throughput and sustainable food monitoring. To increase testing capacity, analytical samples are prepared for measuring alpha and beta radioactivity using either Liquid Scintillation Counting or Gas Proportional Counting.
WK93283 - New Test Method for Detection of Anthropogenic Alpha and Beta Radioactivity in Food by Liquid Scintillation and Gas-flow Proportional Counting | ASTM
