INDC(IND)-35G - IAEA Nuclear Data Services
INDC(IND)-35G - IAEA Nuclear Data Services
INDC(IND)-35G - IAEA Nuclear Data Services
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- 38 -<br />
Multigroup Constanta for Gallium for use in Analysing Fast<br />
Critical Assemblies<br />
(S.Ganesan and V.Gopalakrishnan)<br />
In many multigroup data sets like SETR for instance<br />
the multigroup data are not available for Gallium. The<br />
basic df»ia library ENDF/B-XV available with us does not<br />
include Gallium data. In such a situation, the usual practice<br />
had been to replace Gallium with Copper as an approximation<br />
for nautronic calculations for fast critical assemblies.<br />
This approach might be roughly valid in cases where the<br />
concentration of Gallium is not so significant* For instance,<br />
in SNEAK-9C2 assemblies POZ and C, the nuclides concentration<br />
was only 0.0001410^ nuclides/b-cm which was added to that of<br />
Cu in analysis. In critical assemblies like THOR , the<br />
element Ga is foundito be present in significant quantity.<br />
(Pure Plutonium metal has the unique characteristic of<br />
existing in six allotropic forms between room temperature<br />
and its melting point at 913K. The delta phase of Pu which<br />
occurs in the temperature range of 588 and 73OK can be<br />
stabilised by the addition of a nominal amount of Ga to the<br />
Pu metal. The alloying increases the delta phase stability<br />
range from 73OK veil befew room temperature). In THOR, the<br />
nuclide concentration is 0,00133 nuclides/b-cm in the core,<br />
and a replacement of the same with a different element in<br />
neutronic calculations will lead to uncertain intrepretation<br />
of calculated results. Therefore, the necessity of obtaining<br />
the multigroup data Ga was felt. The basic library ENBL-78<br />
which was identified to be the only library available with<br />
us containing basic data for Gallium was processed by the<br />
code RAMBHA . The multigroup constants thus generated in 25<br />
group structure are being used in the analysis of THOR<br />
assembly.