Measurement of the Ratios of Capture and Fission Neutron Cross Sections of ²³⁵U, ²³⁸U, and ²³⁹Pu at 130 to 1400 keV

Validating nuclear data uncertainties obtained from a statistical analysis of experimental data with the “Physical Uncertainty Bounds” method

“…The variables N 1 or N 1 /N 2 are often determined via α-counting measurements (α-count.) 1 [25,[29][30][31][32][33][37][38][39]43,45,46,49,50,53,60,61,63] independent from fission counting measurements as can be seen in Table 1. A 1% value is assumed as a conservative bound ∆(N 1 ) 1 across all measurements using α-counting to determine N 1 in 239 Pu samples following the literature of individual measurements and reference [24].…”

“…[33] and measurements relative to various other reactions [56,60] were used in only a few cases. The neutron flux was determined once by an activation measurements (ACTIV) [61]. The manganese baths were mostly used jointly with the associated particle technique.…”

“…A general, overarching, technique is named to determine ε for several measurements, namely, identification of particles through pulse-height discrimination (PHD) [ [33,56,61,66,68,74,75], extrapolated (extrap.) [36,38,43] or measured with a rotated detector (rotat.…”

EVALUATION OF $sup 238$U NEUTRON CROSS SECTIONS FOR THE ENDF/B VERSION II FILE.

“…Above 100 keV, the majority of accurate capture measurements are relative to 235u fission, such as Barry [21] and Poenitz [22,23], while the Menlove and Poenitz [24] data can be placed relative to ^^^U fission by use of the fission cross section of Poenitz [25] obtained by the same experimental techniques. These four sets of data were normalized to the ENDF/B [18,26] ^^^U fission cross section and are shown in Figure 1.…”

“…The discrepancy of up to 15% between Barry [21] and Poenitz [23] above 1.0 MeV is significant as it could extend beyond 1.5 MeV where the only reliable data is that of Barry. The discrepancy of 10 -15% between 0.12 and 0.16 MeV is particularly notable in that the lower limit of the data at these energies is required for consistent extrapolation to the capture data below 100 keV (Moxon [19]) measured relative to B(n,oi).…”