MASS SPECTROMETRIC STUDY OF NATURAL AND NEUTRON-IRRADIATED CHLORINE

Abstract

Using a Nier-type mass spectrometer, the isotopic composition of chlorine gas obtained from natural potassium chloride has been measured to be 75.529 ± 0.016 atom per cent Cl³⁵and 24.471 ± 0.016 atom per cent Cl³⁷, corresponding to a Cl³⁵/Cl³⁷atom ratio of 3.0865 ± 0.0027. By comparison of this result with that for chlorine gas from potassium chloride irradiated for 14 months in a high flux position of the NRX reactor, the neutron capture cross-section of Cl³⁶has been determined to be 90 ± 25 barns. This value has been calculated on the assumption that only (n, γ) reactions were significant in changing the isotopic composition of the chlorine.