The Doppler coefficient in thorium dispersed in graphite was measured in a reactor spectrum developed in the HTGR critical assembly, using a reactivity technique that compares the reactivity of a single cold element and a single hot element heated to 700 deg K. The considerable correction due to the small perturbation in neutron temperature resulting from the heating has been experimentally determined by auxiliary measurements. An activation technique has been used to check the results. In this activation technique, the thermal-base effect has also been experimentally subtracted by measuring the 1/v component of the captures at each temperature in vanadium. …
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General Atomic Div., General Dynamics Corp., San Diego, Calif.
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San Diego, California
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The Doppler coefficient in thorium dispersed in graphite was measured in a reactor spectrum developed in the HTGR critical assembly, using a reactivity technique that compares the reactivity of a single cold element and a single hot element heated to 700 deg K. The considerable correction due to the small perturbation in neutron temperature resulting from the heating has been experimentally determined by auxiliary measurements. An activation technique has been used to check the results. In this activation technique, the thermal-base effect has also been experimentally subtracted by measuring the 1/v component of the captures at each temperature in vanadium. Measurements of the Doppler coefficient obtained by these two different techniques agree to within 10%. This agreement, demonstrated by applying both techniques for the first time in the same laboratory, shows that the previously reported spread of results and apparent disagreement between results of these two techniques are avoidable. The average Doppler coefficient for the temperature interval from 300 to 700 deg K, for a carbon-to-thorium ratio of about 50 in the thorium-bearing region, was measured to be 3.6 x 10/sup -4// deg C to within about 10% uncertainty. The measured results are in satisfactory agreement with calculated values. (auth)
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Brown, J. R. & Sampson, J. B.Measured Doppler Coefficient of Thorium Dispersed in Graphite,
report,
February 1, 1963;
San Diego, California.
(https://digital.library.unt.edu/ark:/67531/metadc1033205/:
accessed June 9, 2023),
University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu;
crediting UNT Libraries Government Documents Department.
