Methods for the Assessment of Long-Lived Radionuclides in Humans Resulting from Nuclear Activities or Accidents - Fission track analysis of trace-amounts 239Pu and a copper hexacyanoferrate kit for monitoring radiocaesium

Sammanfattning: Fission track analysis (FTA) was developed to be applied to ultra-low levels of 239Pu in bioassay samples. An analytical protocol was established for the FTA processing. The detection limit was determined to 1.5 µBq and the calibration constant was 24 fission fragments per µBq 239Pu. Naturally occuring nuclides of thorium and uranium, present in biological and environmental samples, did not interfere in the determination of 239Pu. Self-absorption of fission fragments was shown to be insignificant. The study included the determination of 239Pu in urine samples from twenty Chernobyl clean-up workers. All urine samples contained activities below the detection limit for radioanlytical analysis using alpha spectrometry (0.5 mBq). Seven of the samples were further investigated using a thermal ionization mass spectrometer with a sensitivity of 1.000.000 atoms 239Pu. The content of 239Pu in the samples showed to be below 1µBq, with only one exception. It was not possible to draw any major conclusions from the 239Pu results, regarding the clean-up workers' exposure from radionuclides released by the Chernobyl accident. A kit was designed for selective adsorption of radiocaesium in urine samples to be used in situ by contaminated subjects. The kit consisted of copper hexacyanoferrate impregnated cotton filters held by filter holders for sample flow-through. After use, the adsorbed fraction of caesium was 90% in urine samples. The kit facilitates the screening of a population exposed to radiocaesium. Parameters influencing the adsorption efficiency, such as potassium, sodium and calcium concentration of the sample and the sample pH, were investigated and shown to be insignificant for urine samples.