VOID COEFFICIENT OF REACTIVITY ASSOCIATED WITH THE ISLAND REGION OF THE HFIR Page: 1 of 16
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ON4
- 0
*1'
N E RGOAK RIDGE NATIONAL LABORATORY
operated by
UNION CARBIDE CORPORATION
for theU.S. ATOMIC ENERGY COMMISSION
ORNL- TM-
COPY NO. -DATE -lovember 15, 1961
Void Coefficient of Reactivity Associated with the
Island Region of the HFIR
R. D. Cheverton
ABSTRACT
Changes in neutron multiplication caused by voids in the island
of the HFIR have been calculated and measured experimentally. The
results indicate that with only water initially in the island the
maximum change in neutron multiplication (6kmax) associated with
island voids is 0.032 with a corresponding void fraction of 70%. With
a simulated 300 g Pu target in the island 6kmax was 0.016, and the cor-
responding void fraction was 42%.
In view of these large changes in neutron multiplication, calcu-
lations were made to determine what additional materials could be used
in the island to reduce Lkmax and what the associated decrease in peak
thermal flux would be. The results indicated that of the materials
considered the use of beryllium in the water island resulted in the
smallest decrease in flux for a specified &max. To reduce &nkmax to
0.01 required 26% by volume of beryllium in the island; the corre-
sponding reduction in thermal flux, as compared to an all-water island,
was about 10%. In order to reduce Lmax to 0.01 with a 300 g Pu target
in the island, the aluminum-to-water ratio of the target had to be in-
creased from 0.54 to about 1.5 with an associated decrease in target-
averaged thermal flux, as compared to the original target, of 17%.
NOTICE
This document contains information of a preliminary nature and was prepared
primarily for internal use at the Oak Ridge National Laboratory. It is subject
to revision or correction and therefore does not represent a final report. The
information is not to be abstracted, reprinted or otherwise given public dis-
semination without the approval of the ORNL patent branch, Legal and Infor-
motion Control Department.UNION
CARBIDE
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Cheverton, R.D. VOID COEFFICIENT OF REACTIVITY ASSOCIATED WITH THE ISLAND REGION OF THE HFIR, report, November 15, 1961; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1059275/m1/1/: accessed April 26, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.