Review of Molten Salt Reactor Physics Calculations [Disc 2]

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u
E
of these dips and elastic resonances to the second and third dips.
behavior in the lethargy range from 10.5 to 13 is caused by thorium
absorption.
41
to the four dips appearing in this range.
much more pronounced in the blanket calculation than in the cell calcula-
tion because the average densities of fluorine :and thorium are much greater
The
Thorium has four large resonances which correspond in lethargy
in the blanket than in the core.
The fluctuations are always
TBERMOS is a one-dimensional integral transport code which calculates
the scalar thermal neutron spectrum as a function of position. The basic
THERMOS data consists of a thirty group library tape. mese Pine groups
are then averaged over the spectrum and over the cell to obtain broad
group cross sections.
In the present calculations four broad group thermal
cross sections were generated with energy limits as follows:
0.005 ev to
0.06 ev, 0.06 ev to 0.18 ev, 0.18 ev to 0.77 ev and 0.77 ev to 1.86 ev.
The one-dimensional gemnetry of !C"OS
tion of the cell as a series of concentric annular rings.
makes necessary the descrip-
I
description for THERMOS was identical to that previously tlescribed for
- ANISN with one exception. Experience has shwn that to obtain proper
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fluxes in "EWW the unit cell should be enclosed in a region called a
heavy scatterer.
The core cell
This region consists of a heavy nuclide whose only
reaction is scattering. Theunit cell as shown in Fig. 5.2 and described
in Tables 5.1, 5.2, and 5.3 was enclosed in such a region for the THERMOS
calculation.
The temperature of a1 a16 in the cell and t blanket was
assumed to be 900'K.
The spatial variation
in.Fig. 5.4 (energies of 0.
variation is clearly quite
of the average flux
e flu in two of the fine groups is shown
03 ev and 0.07-0.08 ev). The spatial
. Fig. 5.5 shows'the energy distribution
nd blanket calculations.