The requirement that the true value of an anctivity cannot be negative is used for transformation of raw observed values into expected activity values. The probability distribution of the activity values is a truncated normal distribution and the expected value and the variance of the activity value are derived from the observed value and its standard deviation. It has been shown that the standard deviation of the activity value is less than the standard deviation of the observed value and that the ratio of the standard deviation of the activity value and the expected value is less than one.
COBISS.SI-ID: 23900967
In gamma-ray spectra, acquired in the absence of the sample, peaks occor which belong to the spectrometer background. When samples are measured, which contain radionuclide that appear in the background also and have activities near the detection level, the background contributes substantially to the peak areas. The probabilities for false positives together with the decision thresholds are given for radionuclides appearing in the background spectra. For some radionuclides that do not appear in the background spectra, probabilities for false detection are given as well.
COBISS.SI-ID: 24131111
A method for measuring the low-activity concentration of 238U in water is described. Samples of 50 L were evaporated and the dry residue after evaporation was measured. Typically, 30 g of material was obtained for the samples processed in this way. The decision threshold resulting from gamma-ray spectrometric measurements was assessed to 1.5 Bq/m3. A total od 26 samples of ground awter were processed and activity concentrations up to 20 Bq/m3 were measured. However, most of the results were in the range arround 5 Bq/m3.
COBISS.SI-ID: 24321319
The background due to radon daughters originates from various sources, characterized by the location of radon daughters in the spectrometer. The spectrometer background due to radon daughters originates in the presence of 226Ra in the detector and the shielding, the presence of radon daughters in the air filling the shield's cavity and in the incomplete attenuation of gamma-rays from the environment where the shield is situated. It was found that in some detectors background induced by radon daughters is constant in time whereas in others it exhibits correlation with outside temperature.
COBISS.SI-ID: 24430631
Concentrations of tritium, gamma-ray emitters in the uranium and thorium decay chains (U-238, Th-234, Pb-210, Ra-228, Ra-226 and Th-228) and potassium were measured in samples of ground water in Slovenia. Correlations among Ra-226, Ra-228 and Th-228 were observed in samples from intergranular and fractured aquifers. It was also found that the variability of tritium activity in intergranular aquifers is the largerestand in fractured ones the smallest.
COBISS.SI-ID: 24327207