Rapid determination of strontium-90 in environmental samples by single Cerenkov counting using two different colour quench curves

Abstract

Planta, 118020 Buirelonu, S p i n l h e validation of the Cerenkov radiation measurement of to determine the activity concentration of "Sr in environmental samples is described. Liquid-liquid extraction with di-2-ethyhexylphosphoric acid in toluene was used to separate 90Y from 90Sr. Optimum conditions for Cerenkov counting (low-level counting option, counting windows, mass of solution to be measured) were established. The need for a counting efficiency correction by using a colour quench curve is stated to be essential, otherwise a significant error may occur. Two different colour quench curves (counting efficiency versus the channel ratio or spectral index parameter) were used and the results were compared. The method was applied to 12 environmental matrices: sea-water, algae, carobs, milk, almonds, hake, honey, shellfish, lamb meat, sardine, pork meat and shore sand. No significant differences were observed on using either of the two colour quench curves for any of these environmental matrices. In order to validate the proposed method, a certified soil reference material (CRM IAEA-375) was used, together with participation in an interlaboratory exercise to determine 90Sr in a natural water sample. Again, efficiency correction was performed by using either of the two colour quench curves and in both instances the calculated 90Sr activity concentration was in good agreement with the known values.

Prediction of Radionuclide Aging in Soils from the Chernobyl and Mediterranean Areas

“…For the Spodosol 3 and Peat soils, results of 90 Sr aged for 6 yr under field conditions were available from the literature, and are also given in Fig. 1 (6Y samples) (Askbrant et al, 1996; Torres et al, 1996). In general, Sr yields varied more as a function of soil type than due to aging induced by the treatments, since the joint effect of the time and temperature did not result in a significant aging of Sr in most cases.…”

“…Figure 2 shows the Sr extraction yields obtained from those soil samples contaminated with soluble 85 Sr and submitted to DW cycles at various temperatures. For the Spodosol 3 and Peat soils, results for the 90 Sr sample aged for 6 yr under field conditions are also included (Askbrant et al, 1996; Torres et al, 1996).…”

“…Extraction yields of 12M samples of the Spodosol 3 and Peat soils were similar to the values obtained from field 6Y samples, thus suggesting that the maximum degree of aging had been reached in the laboratory experiments. (Askbrant et al, 1996;Torres et al, 1996).…”

Beta detection of strontium-90 and the potential for direct in situ beta detection for nuclear decommissioning applications

“…As such, the refractive index of the selected medium can be used to discriminate between different sources of radiation as the maximum energy of emitted energy from the radioisotope must greatly surpass the threshold energy, given the spectrum of energised beta-particles released [32]. The light produced by Cherenkov radiation can be measured with existing commercial liquid scintillators [33,34,35].…”

“…The primary quenching effect in Chernekov counting is colour quenching, simply a consequence of discolouration of the sample, which contributes to the absorption of light emitted during the Cherenkov process. However, this can be compensated by calibration with a colour quench correction curve[35,36].An alternative is to use the Triple to Double Coincidence Ratio (TDCR) technique. TDCR has recently become popular with many national metrology institutes as a method of determining primary activity standards.…”