Determination of uranium and thorium isotopes in NORM materials in the ceramic industry by using alpha-particle spectrometry

A radiochemical procedure has been developed for the quantification of uranium and thorium isotopes in NORM samples from the ceramic industry, such as zirconium sands, zirconium flours, micronized zircon, pigments and personal aerosol filters. The method is based on a fusion pretreatment with borate salts, a separation with anion exchange resins and alpha-particle spectrometry measurement. This method is an alternative to gamma spectrometry when the amount of sample is extremely small (2–10 mg) as in the case of aerosol filters, or there is no secular equilibrium in the ²³⁸U and ²³²Th chains, as in the ceramic pigments. The method has been validated with different ceramic materials and the comparison of the results with gamma measurements. Its reproducibility was also checked with different sample masses.