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2025 ANS Winter Conference & Expo
November 8–12, 2025
Washington, DC|Washington Hilton
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Ho Nieh, TVA board members, and nuclear fuel recycling bill head to Senate floor
Nieh
Ho Nieh, the Trump administration’s nominee to be a member of the Nuclear Regulatory Commission, and four new board members of the Tennessee Valley Authority were approved in a vote today by the Senate Environment and Public Works Committee and head to the Senate floor for a final vote.
The committee also voted to advance to the Senate floor the Nuclear REFUEL Act of 2025 (S. 2082), which would smooth the regulatory pathway for recycling used nuclear fuel.
President Donald nominated Nieh on July 30 to serve as NRC commissioner for the remainder of a term set to expire June 30, 2029, which was held by former NRC commissioner Chris Hanson, who Trump fired in June.
John M. Jamieson, Geoffrey G. Eichholz
Nuclear Technology | Volume 39 | Number 1 | June 1978 | Pages 95-100
Nuclear Safety Analysis | Energy Modeling and Forecasting / Analysis | doi.org/10.13182/NT78-A17011
Articles are hosted by Taylor and Francis Online.
A method for analyzing nuclear material for different fissile nuclides by cyclic activation has been developed and tested experimentally with samples of 235U and 239Pu, singly and in combination. The method of analysis is based on the differences in the abundances and half-lives of delayed neutron groups between the various fissile nuclides. The steady-state delayed neutron response to periodic activation is independent of activation cycle period at short periods, decreases exponentially with period at long periods, and has a break point, or knee, where the response changes from constant to exponential, or from one exponential to another, with greater slope for each characteristic emitter present. The activation cycle periods at which these break points occur, the slopes of the exponential fall-off or response with cycle period between break points, and the absolute magnitude of the response at any cycle period are all functions of the effective half-lives and abundances of the delayed neutron precursors activated, so, consequently, the characteristic delayed neutron response as a function of activation cycle period is different for the various fissile species. In the experiment, cyclic activation was accomplished by moving the samples containing fissile material cyclically through a thermal-neutron beam from the Georgia Tech Research Reactor, out of the beam and through a delayed neutron detector, and back through the beam, etc. The delayed neutron response was recorded at activation cycle periods ranging from 0.1 to 100 s for samples containing varying amounts of 235U and 239Pu. Deviations in the responses of the samples containing both 235U and 239Pu from the response of standards containing only 235U or 239Pu were determined to infer the 235U- to-239Pu ratio. After the ratio of the two fissile nuclides present was obtained, the delayed neutron response at short cycle periods was used to estimate the mass of each fissile nuclide present in the sample. For samples containing about a gram of fissile material, accuracies on the order of 2% for 235U and 4% for 239Pu could be obtained for 1.5-h experiment run times when the fissile nuclides were present in about equal portions. Accuracies were dependent on the 235U-to-239Pu ratio and on the total mass of fissile materials present.
