Measurement of ¹³⁵I Yield Ratios and Fission-Product Cross Sections in the Advanced Reactivity Measurement Facilities

The yields of ¹³⁵I in the fission of ²³³U, ²³⁹Pu, and ²⁴¹pu relative to that of ²³⁵U have been measured by an integral method using the Advanced Reactivity Measurement Facilities (ARMF I and II). The xenon reactivity transient was measured following irradiation of the fissile isotope in the Materials Testing Reactor (MTR) for periods from to 2½ to 16 days. The use of the two ARMF reactors permits the calculation of the absorption cross sections of both simple absorbers and fissile atoms. The ¹³⁵I yield ratios, relative to ²³⁵U, were found to be 0.825 ± 0.072 for ²³³U, 1.006 ± 0.067 for ²³⁹Pu, and 1.221 ± 0.089 for ²⁴¹Pu. The uncertainties quoted are confidence intervals at the 90% confidence level.