MEASUREMENT OF ABSOLUTE FISSION RATE OF NATURAL, DEPLETED URANIUM AND THORIUM, AND MICROSCOPIC CROSS SECTION RATIOS IN THE RADIAL BEAM OF THE RA3
Argentine National Atomic Commission
Avda. Libertador, 8250, Buenos Aires, Argentina
The capability to measure absolute fission rates per nuclei has been established to a precision level of around ± 2%. Thin deposits of ThO2 and U3O8 were prepared by molecular plating and the isotopic masses determined by two techniques. A miniature fission chamber and SSNTD fission fragment detection techniques were used in the radial neutron beam of the RA3. Fission fragments selfabsorption in the deposits are corrected. The results of this investigation are: 1. Optical efficiency of SSNTD detectors. 2. The microscopic integral fission cross section ratio of Th232 to U238 by two independent techniques. 3. Experimental ratios of natural, depleted uranium and thorium fission rate per μg to Mn56 (Mn thermal flux monitor) disintegration rate per μg. The agreement with calculated results is excellent.
KEYWORDS: fission fragments detection, integral cross section, fission tracks, neutron spectra, neutron beam, Th232, U238, In115