SELF-ABSORPTION AND SUMMATION CORRECTIONS FOR THE RADIONUCLIDES CS-137, CS-134 AND K-40 IN THE EVALUATION OF THE RESULTS OF THE RING ANALYSIS OF GRASS POWDER IN THE YEAR 1993

A previous evaluation of the interlaboratory test carried out in 1993 did not distinguish between those results corrected for self-absorptio n and summation effects and those not corrected. However, a quarter of the participants applied such corrections. Therefore, the data collec tive lacked the homogeneity needed for a correct statistical evaluatio n. We have now applied details provided by the participants on the geo metry of the detector and sample source in a method recently developed by us to eliminate self-absorption and summation effects from the res ults of 40 laboratories. A further 15 laboratories applied their own c orrection methods, some of which, however, considered only one of the two effects. In these cases, we calculated the uncorrected effect by o ur new method. After applying these corrections, the means of the labo ratories means corresponded more closely to the reference values for t he radionuclide activities. The corrections for self-absorption are ab out 5% on average with extreme values up to 17%, while the corrections for summation effects average about 9%, with extreme values of up to 26%.