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Conference Spotlight
2025 ANS Winter Conference & Expo
November 8–12, 2025
Washington, DC|Washington Hilton
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Energy Secretary to speak at the 2025 ANS Winter Conference & Expo
In less than two weeks, the American Nuclear Society’s second annual conference of the year, the 2025 ANS Winter Conference & Expo, will come to Washington, D.C.
Today, ANS is announcing that Energy Secretary Chris Wright will be joining the list of nuclear leaders slated to speak at the conference.
Click here to register for the meeting, which will take place November 9–12 in Washington, D.C., at the Washington Hilton. Be sure to do so before November 7 to take advantage of priority pricing.
W. R. Waltz, J. F. Walter
Nuclear Technology | Volume 10 | Number 2 | February 1971 | Pages 160-167
Technical Paper and Note | Reactor | doi.org/10.13182/NT71-A30923
Articles are hosted by Taylor and Francis Online.
Comparisons of calculation and experiment have been performed to test the adequacy of fewgroup subcritical diffusion theory in predicting neutron detector response induced from material changes in a subcritical water-moderated reactor. In many operations involving material changes in a subcritical reactor, it is desired to monitor changes in the multiplication factor (Keff) of the system to ensure the safety of an operation by avoiding an accidental close approach to criticality. This monitoring procedure is accomplished by the introduction of artificial neutron sources to the system and by the proper interpretation of changes in neutron detector readings in terms of Keff. Because of the rather complicated involvement of the source-core-detector system, proper interpretation of detector response observed during these operations can only be achieved by the availability to predict detector response obtained from an accurate calculational model. Comparisons of calculation to experiment show that diffusion theory may be used successfully for these purposes; however, certain limitations of the model must be recognized and avoided. The breakdown of the calculational model in certain cases can be related ultimately to the inability of few-group diffusion theory to predict the absolute magnitude of detector flux for large distances through a water (or metal-water) shield. This inability can result in inaccuracies in predicted count rate response when applied to a specific source-core-detector arrangement with the characteristic that a given material change results in gross changes in the axial flux distribution. These effects can be overcome by the suitable positioning of the neutron source and detector relative to the subcritical assembly.
