Direct and precise determination of environmental radionuclides in solid materials using a modified Marinelli beaker and a HPGe detector

Bias in 238U decay chain members measured by γ-ray spectrometry due to 222Rn leakage

In this work we investigate and quantify how effectively the noble gas ²²²Rn is trapped inside measurement beakers used in high-resolution gamma-ray spectrometry. We test six types of different beakers commonly utilized in γ spectrometry, including one novel construction, the γBeaker. We assessed ²²²Rn leakage by injecting ²²²Rn rich air into the examined beakers and investigated the abnormal decrease in ²²²Rn daughters - ²¹⁴Pb and ²¹⁴Bi. The measured decay times were used to estimate the ²²²Rn leakage. In addition, we investigated the influence of an additional beaker sealed with tape. However, the additional beaker sealing only slightly reduced the ²²²Rn escape and was not reproducible. Almost every tested beaker exhibited heavy ²²²Rn leakage. This may lead to an underestimation and radioactivity over-dispersion of ²³⁸U decay chain members when they are measured via their ²²²Rn daughter products.

NATURAL RADIOACTIVITY STUDIES OF PHOSPHATE FERTILIZERS APPLIED ON GREEK FARM SOILS USED FOR WHEAT CULTIVATION

Naturally Occurring Radionuclide Materials (NORM) such as fertilizers, agricultural soils fertilized and wheat grain cultivated at those soils were studied regarding the radiation hazard to the public and workers. Activity of 238U, 226Ra, 232Th and 40K was measured hermitical sealing the marinelli beaker using the Stopaq FN 2100L material that prevent 222Rn escape from the baker. The phosphate fertilization of soil did not affect natural radioactivity in comparison with non-fertilized soils and also did not affect natural radioactivity of wheat grain cultivated since only 40K was measured. The high mean value of Dair 211 nGy h-1 for fertilizers compared to soils fertilized 53 nGy h-1 highlights the raising concern about radioprotection of workers occupied with tasks involving fertilizers. The maximum external dose rate 1.15 mSv y-1 calculated for truck drivers involved to transportation section is similar to annual external effective dose limit 1 mSv. Real concerns rise for workers in the fertilizers storage and supply department since the maximum dose rate estimated is 1.98 mSv y-1, while the mean value is 0.89 mSv y-1.