ORNL-TM-7207 - the Molten Salt Energy Technologies Web Site

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The code calculates nuclide concentrations, total inventories, reactivity,
and breeding ratio as a function of time.
Treating the lengthy transplutonium and fission-product chains in
QUAB was not practical; multigroup data were not available far many of
the required nuclides and were of dubious reliability for others. In-
stead, the BRIGEN code15 was used with a library of cross sections" es-
pecially devised for its uses The BRIGEN results were then "patched into"
the QUAB calculation directly.
The burnup calculation allowed the cross sections of thorium and 2 38~
to vary continuously during the calculation; this was accomplished by in-
terpolation.
3.1 e 3.2 Evaluation
As desired, the method provided relatively rapid response9 detailed
treatment of resonances, and a mulitigr~up spectrum and cell treatment.
All details of the denatured fuel cycle were treated. The expedient of
treating a range of thorium and 2 3 8 ~ densities remevest the necessity of
imbedding the expensive and tedious resenamce treatment inside the Loop
for varying densities. Deciding on the applicable range was not difficult
after a few initial tries.
A system ~oupling the spatial calculation and depletion could be
used. Kany such systems are available, although all would require exten-
sive modification for MSR use. What of the cell calculation? Table 7
shows the cell factors from our reference case which have been condensed
to three energy groups. This is clearly a heterogeneous core. Further,
the actinide densities are continually changing, resulting in time-
dependent cell factors. Studies beyond these would be required t~ prove
that a coupled system could be worthwhile without directly co~pled cell.
cal cul a t io n s .
The requirement to "umix" the revised nuclear densities after hav-
ing them lumped together during a depletion step represents a complica-
tion that would thwart most existing codes. However, this complication
must be coupled with logic to provide interpolation between cross-section
sets representing various self-shielding situations. With or without an