ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Thermal Hydraulics
The division provides a forum for focused technical dialogue on thermal hydraulic technology in the nuclear industry. Specifically, this will include heat transfer and fluid mechanics involved in the utilization of nuclear energy. It is intended to attract the highest quality of theoretical and experimental work to ANS, including research on basic phenomena and application to nuclear system design.
Meeting Spotlight
ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
Latest Magazine Issues
Apr 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
May 2025
Nuclear Technology
April 2025
Fusion Science and Technology
Latest News
General Kenneth Nichols and the Manhattan Project
Nichols
The Oak Ridger has published the latest in a series of articles about General Kenneth D. Nichols, the Manhattan Project, and the 1954 Atomic Energy Act. The series has been produced by Nichols’ grandniece Barbara Rogers Scollin and Oak Ridge (Tenn.) city historian David Ray Smith. Gen. Nichols (1907–2000) was the district engineer for the Manhattan Engineer District during the Manhattan Project.
As Smith and Scollin explain, Nichols “had supervision of the research and development connected with, and the design, construction, and operation of, all plants required to produce plutonium-239 and uranium-235, including the construction of the towns of Oak Ridge, Tennessee, and Richland, Washington. The responsibility of his position was massive as he oversaw a workforce of both military and civilian personnel of approximately 125,000; his Oak Ridge office became the center of the wartime atomic energy’s activities.”
Jean-Paul Deffain, Philippe Alexandre, Paul Thomet
Nuclear Technology | Volume 127 | Number 3 | September 1999 | Pages 267-286
Technical Paper | Fission Reactors | doi.org/10.13182/NT99-A3001
Articles are hosted by Taylor and Francis Online.
This feasibility study on core control using only the control rods is conducted with the TOPAZE algorithm - implemented in the CRONOS2 core calculation code - in its two versions: version 1 (minimization of the two-dimensional peak, imposed axial offset) and version 2 (minimization extended to three-dimensional, without imposed axial offset). The sensitivity analysis on the power peaks was carried out on the variations of the axial height of the burnable poisons and the type of grey or black control rod clusters. It is demonstrated that the reduction in the number of rod cluster controls allows a correct smoothing of the reactivity over the whole cycle, except for the end of cycle when control rods are moved upward.For load follow feasibility studies, several approaches, based on simulations performed with MISRITME have been evaluated: variation of the primary flow rate for axial offset control; use of a program, with temperature decreasing with the power; and finally, coupling of a temperature range, centered on a reference temperature with a negative gradient, to the French N4 reactor control mode Dispositif de Manoeuvrabilité Accrue: X (DMAX). It is shown that the return to equilibrium following a low threshold of 40% induces an additional penalty between 15 and 20% on the power peak. Solutions are suggested to globally reduce these peaks, which appear during all operating conditions.Two types of reactivity-induced accidents linked to clusters are studied: the removal of a rod cluster control assembly (RCCA) at full power (class III) and the ejection of a RCCA (class IV). It is also shown that ejection at zero power, with a released reactivity of 1.86 $, does not cause major damage to cladding and fuel. However, at full power, with the assumptions made, a partial melting of the pellet occurs without however creating fuel dispersion in the coolant.