Review of Molten Salt Reactor Physics Calculations [Disc 2]

10
2. The average '1 of 235U was 1.9n compared with 1.958 in the
previous calculations. We believe that the new cross sections are
likely to be better for this nuclide. The result was an increase in
breeding ratio of 0,001.
3. We used a lower cross section for 234U in accordance with the
.recammendations of the latest edition of 3ML-325, As (1 consequence,
more of the 234U
was removed with the excess uranium, and there were
'fewer absorptions in 235U, 236U, and 237Np. The net result kppears
to have been an increase.in breeding ratio of less than 0.001.
4. We did not include any 23% production in our calculation
since it did not seem appropriate. Any other trans-uranium isotdpes
beyond 237Ng
should not lead to a net loss since they could probably
be separated and sold if there were any tendency for them to accumulate.
An increase in breeding ratio of 0.001 resulted.
5. Parasitic absorptions in carrier salt (other than 6 W) were
lower because of the Increased fissile loading In our calculation. An
increase of 0.003 in breeding ratio occured.
6. Parasitic absorptions in graphite were lower for the same reason.
An increase of 0.004 occured.
7. The previous calculations osnittqd the INOR tubes in the lower
blanket. Although there is a possibility of reducing the ef'fect by
redesign, the current design gave a breeding ratio loss of 0.005 to
absorptions in the INOR.
8. Our calculations gave an increase in breeding ratio of 0.003
from lower fission product absorption. About one-half of this difference
came from nuclides which were allowed to recycle in the cPTIMERc calcula-
tion althorn belonging to chemical groups which are actually thought .%o
be removed in reprocessing. It may be that the prevholis calculations
were Justified in introducing a measure of conservatism at this point.
The remainder of the difference is associated with the higher fissile
inventory in our calculations.
. 9. The previous calculations used a 7 I,% content in the makeup of
99.997$ together with a cost of $120 per kg. In reviewing the basis for
this choice we find that the publtshed AEC price schedule is for 99.996
t