Rapid determination of⁹⁰Sr by Compton suppression gamma-ray spectrometry

Abstract

This work presents a low-level background gamma spectrometry system capable of achieving rapid determination of⁹⁰Sr without chemical separation, in a soil sample when the⁹⁰Sr to γ-ray emitting nuclide concentration ratio exceeds 10. The system consists of a highly efficient HPGe central detector operated in coincidence or anticoincidence with a NaI(Tl) guard detector and a NaI(Tl) backscatter detector. Experimental results indicate that the bremstrahlung radiation from a pure β-emitter can be distinguished with respect to the differences in normal and coincidence spectra. The⁹⁰Sr activity can be directly detemined in the sample in less than 1 hour with a minimum detectable concentration (MDC) estimated at 0.002 Bq·g⁻¹ for a sample containing no appreciable γ-ray nuclides or other high energy, β-emitting nuclides. In actual measurement, a 0.06 Bq·g⁻¹ MDC for contaminated soils is achieved.