ABSTRACT
The results are described of an upgrade of the low-background gamma-ray spectrometry laboratory at New York State Department of Health by acquiring sensitivity to low-energy gamma rays. Tuning of the spectrometer and its low-energy response characteristics are described. The spectrometer has been applied to monitor the environment by measuring aerosols and water in New York State contaminated by the 2011 Fukushima accident plume. In addition, the spectrometer has been used to monitor radioactivity in food by performing a study of cesium in Florida milk.
Subject(s)
Air Pollutants, Radioactive/analysis , Background Radiation , Food Analysis/instrumentation , Food Contamination, Radioactive/analysis , Radiation Monitoring/instrumentation , Radiation Protection/instrumentation , Spectrometry, Gamma/instrumentation , Equipment Design , Equipment Failure AnalysisABSTRACT
This paper describes the development of methods for the rapid screening of gross alpha (GA) and gross beta (GB) radioactivity in liquid foods, specifically, Tang drink mix, apple juice, and milk, as well as screening of GA, GB, and gamma radioactivity from surface deposition on apples. Detailed procedures were developed for spiking of matrices with (241)Am (alpha radioactivity), (90)Sr/(90)Y (beta radioactivity), and (60)Co, (137)Cs, and (241)Am (gamma radioactivity). Matrix stability studies were performed for 43 days after spiking. The method for liquid foods is based upon rapid digestion, evaporation, and flaming, followed by gas proportional (GP) counting. For the apple matrix, surface radioactivity was acid-leached, followed by GP counting and/or gamma spectrometry. The average leaching recoveries from four different apple brands were between 63% and 96%, and have been interpreted on the basis of ion transport through the apple cuticle. The minimum detectable concentrations (MDCs) were calculated from either the background or method-blank (MB) measurements. They were found to satisfy the required U.S. FDA's Derived Intervention Levels (DILs) in all but one case. The newly developed methods can perform radioactivity screening in foods within a few hours and have the potential to capacity with further automation. They are especially applicable to emergency response following accidental or intentional contamination of food with radioactivity.
Subject(s)
Alpha Particles , Analytic Sample Preparation Methods/methods , Food Contamination, Radioactive/analysis , Gamma Rays , Malus/chemistry , Radioisotopes/analysis , Radioisotopes/chemistry , Beverages/analysis , Calibration , Cesium Radioisotopes/analysis , Cobalt Radioisotopes/analysis , Digestion , Emergencies , Malus/radiation effects , Radioactivity , Spectrometry, Gamma/methods , Strontium Radioisotopes/analysis , Yttrium Radioisotopes/analysisABSTRACT
A new method for alpha spectroscopy of evaporated water residues was developed, consisting of evaporation of drinking water, flaming of the planchets, and alpha-spectroscopic measurements using a grid ionization chamber. The method can identify and quantify radioactivity concentrations > or =3 mBq L-1 in a matter of several hours, whereas determination of sub-mBq L-1 levels is achievable in 1 day. Detailed investigations of flaming of the planchets, the humidity effect, and alpha spectroscopy of thick sources are described. A three-dimensional calibration of the method was performed using standards containing 238U, 230Th, 239Pu, 241Am, and 244Cm radionuclides. In addition to its application to evaporated drinking water, this calibration is common for any environmental sample that can be prepared as a uniform layer, such as the residues from surface water, acidic washing or leaching from materials, as well as biological fluids such as urine. The developed method serves as a fast identifying or screening technique for emergency response involving alpha radioactivity.
Subject(s)
Alpha Particles , Radiometry/methods , Spectrum Analysis/methods , Water Supply/analysis , Calibration , Humidity , VolatilizationABSTRACT
Gross alpha counting of evaporated water residues offers a simple method for screening alpha radioactivity in water for both public health and emergency purposes. The evaporation process for water has been improved by using a combination of roughening of the surface of counting planchettes, two-stage evaporation, and temperature-controlled block heating. The efficiency of the gas-proportional detector for alpha-particle detection in water residues was studied as a function of sample mass-thickness in the range between 0.1 and 13 mg cm(-2). The effect of alpha energy on the efficiency, as well as moisture absorption on the samples, were studied using (230)Th, (238)U, (239)Pu, (241)Am, and (244)Cm radionuclides. Also, alpha-to-beta crosstalk was investigated as a function of sample mass for (230)Th, (238)U, (239)Pu, (241)Am, and (244)Cm. The improved method can also be applied for gross alpha detection in biological fluids.
