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Hash Hashemian: Visionary leadership
As Dr. Hashem M. “Hash” Hashemian prepares to step into his term as President of the American Nuclear Society, he is clear that he wants to make the most of this unique moment.
A groundswell in public approval of nuclear is finding a home in growing governmental support that is backed by a tailwind of technological innovation. “Now is a good time to be in nuclear,” Hashemian said, as he explained the criticality of this moment and what he hoped to accomplish as president.
J. T. Mihalczo, J. J. Lynn, J. R. Taylor
Nuclear Science and Engineering | Volume 130 | Number 1 | September 1998 | Pages 153-163
Technical Paper | doi.org/10.13182/NSE96-121
Articles are hosted by Taylor and Francis Online.
The reactivity worth of a central void region in the Oak Ridge National Laboratory (ORNL) unmoderated and unreflected uranium (93.20 wt% 235U) metal sphere was obtained by replacement measurements in a small (0.460-cm-diam) central spherical region in this 3.4420-in.-radius sphere. The measured central void region worth was 9.165 ± 0.023 ¢ using the delayed neutron parameters of Keepin, Wimett, and Zeigler to obtain the reactivity from the measured stable reactor periods. This value is slightly larger than measurements for GODIVA I with larger cylindrical samples of uranium (93.70 wt% 235U) in the center: 135.50 ± 0.12 ¢/mol for GODIVA I and 138.05 ± 0.34 ¢/mol for the ORNL sphere measurements. The difference could be due to sample size effect. The central worth was also calculated by neutron transport theory methods to be 6.02 ± 0.01 × 10-4 k. The measured and calculated values are related by the effective delayed neutron fraction. The value of the effective delayed neutron fraction obtained in this way from the ORNL sphere is 0.00657 ± 0.00002, which is in excellent agreement with that obtained from GODIVA I measurements, where the effective delayed neutron fraction was determined as the increment between delayed and prompt criticality and was 0.0066. From these ORNL measurements, using the delayed neutron parameters of ENDF-B/VI to obtain the reactivity from the stable reactor period measurements, the central void worth is 7.984 ± 0.021 ¢, and the inferred effective delayed neutron fraction is 0.00754. These values are 14.2% higher than those obtained from use of the Keepin, Wimett, and Zeigler delayed neutron data and produce a value of effective delayed neutron fraction in disagreement with GODIVA I measurements, thus questioning the usefulness of the six-group delayed neutron parameters (fast fission) of uranium from ENDF-B/VI for obtaining the reactivity from the measured reactor period using the Inhour equation.
