The second of the arrays modeled was listed as the 4 x 3.09 x 1 array with the 0.5 inches
(1.27 cm) water gap. (The 3.09 indicates that only two of the possible twenty two fuel plates
were present in four of the fuel assemblies present in the array.) The effective multiplication
factor was calculated to be keff ± 1s = 1.0055 ± 0.0031.
As shown by the results listed in these two examples both critical systems were shown to
be critical in the KENO V.a models. These results along with the BORAX V Superheater results
lead to the conclusion that no bias compensation is needed in this evaluation.
The configuration of the critical systems modeled for the purposes of validation and
applicability were similar to the modeled configurations used in this evaluation. The actual critical
configurations consisted of arrays of full and partial BORAX-V and SPERT-D fuel elements, as
previously described. The models in the evaluation consisted of arrays of BORAX-V fuel
elements as described in the text of this report. Also, the SPERT-D fuel elements consisted of a
uranium stainless steel fuel matrix similar to the BORAX-V elements.
In addition to the described critical experiments, various other critical experiments9,10,11
were modeled in an attempt to validate the applicability bounds of the previously described code
and cross section package. The critical experiments consisted of various uranium forms (metal,
oxide, and liquid), moderator ratios, reflector materials, and single units and various array sizes.
Concrete reflection existed in some of the critical examples which, although are not exact
comparisons, can be used to validate the applicability of the code and cross section package for
reflected systems as modeled in this evaluation.