SIMULTANEOUS MEASUREMENTS OF THE NEUTRON FISSION AND CAPTURE CROSS SECTIONS FOR $sup 235$U FOR INCIDENT NEUTRON ENERGIES FROM 0.4 eV TO 3 keV.

Abstract

The neutron f i s s i o n and capture cross sections f o r 2 3 5~ have been measured simultaneously f o r incident neutron energies from 0.4 eV t o 3 keV. I n addition, t h e f i s s i o n cross section has been measured up t o a neutron energy of 20 keV.

Evaluation of the235U resonance parameters to fit the standard recommended values

“…00233 (ORNL/1986) [13] atom/barn, and T = 77 K Harvey 4.0-2250.0 L = 80 meters, n = 0. 03269 (ORNL/1986) [13] atom/barn, and T = 77 K Fission [22] T = 293.6 K TOF length is indicated by the letter L, thickness by n, and temperature by T. The Reich-Moore approach of the code SAMMY was used for fitting the data. A total of 3170 resonance levels were identified in the energy range 0-2250 eV to reproduce the experimental data.…”

Uncertainty Analyses of Neutron Cross Sections for235U in the Resonance Region

“…In principle, the measurements, which Leal et al 2) had used for the analysis of the resonance parameters, were employed in the present covariance evaluation. However, the data of de Saussure et al 12) and Perez et al 13) were disregarded finally, since the inclusion of both data led to too large 2 values which meant that these data deviated from other measurements given in Table 1. (3) Covariances of Capture Cross Sections Leal et al 2) used the data of de Saussure et al, 12) Perez et al 13) and Gwin et al 19) to estimate the resonance parameters of 235 U. Among these data, the data of Gwin et al 19) are not available in EXFOR.…”

“…Gwin et al 14) 1:59Â10 À3 -100 eV Statistical 2.0 Weston and Todd 15) 9.7 eV-200 keV Total 2.0 Schrack 16) 1:5Â10 À2 eV-1.4 keV Statistical 2.0 Wagemans et al 17) 2:02Â10 À3 -20.15 eV Total 0.5 Weston and Todd 18) 99.9 eV-2.0 keV Statistical 1.0 Capture de Saussure et al 12) 0.4-62.8 eV Statistical 3.0 Perez et al 13) 8-200 eV Statistical 5.0 Gwin et al 20) 0.01-200 eV Statistical 3.0 Corvi et al 21) 2-85 keV Total 4.0…”

SIOB: a FORTRAN code for least-squares shape fitting several neutron transmission measurements using the Breit--Wigner multilevel formula. [For IBM-360/91]

“…where Lis the flight-path length, 6L is the tota•l uncertainty in flightpath due to the finite thicknesses of the source and of the detector and• to the11 equivalent length 11 of the moderation spread;"dt is the •total uncertainty in timing and the .constar:it lJ = 72••~3. eV 1 I 2 ~/m~ The factors .…”