Assessment of interferences in determining radon 222 in waters by scintillation and ionization methods

The interference was considered of 219Rn and 220Rn radioisotopes in determining 222Rn by ionization and scintillation methods. The theoretically calculated time pattern of the alpha activity of 219Rn and 220Rn and their products suggests that the interference at a 5% activity level of 222Rn and its transformation products would be, in case of growth measurements after 60 min. in an ionization or scintillation chamber, at a 220Rn relative activity 177 times higher compared with the 222Rn activity at the moment of transferring emanations in the chambers. Taking into account the 219Rn transformation half-life, the same interference would occur when the 222Rn activity exceeded the 220Rn activity by one order. Thus, as far as routine samples are concerned, the interference in the 222Rn determination caused by sample contamination with natural radon isotopes can be completely neglected. (author)