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2 criterion. Hence, conclusions relative to system similarity based on these D coefficients agree with those of the preceding analysis using the ck values. 3 Traditional Trending Analysis In order to clearly show the relationship between the GLLSM techniques and the more traditional techniques for criticality safety validation, a traditional trending analysis using the same 102 benchmark experiments is presented. In Figure 9, keff is trended versus the energy of average lethargy causing fission (EALF).

The trend with enrichment is similar, but not enough data are present for the intermediate enrichments to confirm the trend. , the upper portion of the EALF, EALC trend plots and the lower portion of the H/X trend plot). Upon examination, it was observed for H/X = 0 systems that the predicted keff values less than unity were from the HEUMET set of criticals, while the systems with predicted eigenvalues greater than unity were from the Big-10 and ZPR sets. The combined effects of the high-versus-low enrichments and the processing of the SCALE 44-group library (collapsed using a thermal reactor spectrum) are believed to be responsible for this variation.

Not be included together unless that specific effect is being analyzed. For example, do not include three or four random systems with boron poisons in an analysis of nonpoisoned systems. As was seen in the comparison of the traditional-versus-advanced validation procedures in Table 12, the inclusion of widely varying benchmarks can cause cancellation of trends, resulting in an under prediction of the keff bias. Similar situations could also result in an over prediction of the keff bias. The advanced trending analyses, using the D and ck coefficients as trending parameters, are recommended under conditions that are similar but complimentary to the above recommendations for the traditional trending analyses.