The Effects of the Evaluator Assigned Nitrogen Nuclear Cross Section Uncertainties Upon the Transport of Neutrons in Air.
Abstract
The sensitivity of the transport of 14-MeV neutrons in sea level air to uncertainties in the ENDF/B-III values of the various Nitrogen cross sections has been calculated using the correlated sampling Monte Carlo neutron transport code SAMCEP. The source consisted of a 14.0 to 15.0-MeV band of isotropic neutrons and the fluences (0.5-15.0-MeV) were calculated at radii from 50 to 1500 meters. Various perturbations were assigned to the ENDF/B-III or base cross section set. They were: (1) a 5% increase to the elastic cross section with a corresponding decrease in the inelastic cross section, (2) a 3% decrease in the elastic cross section with an equivalent increase in the inelastic cross section, (3) the smoothing of the valley in the elastic cross section around 11 MeV with compensating changes taken in adjustments among the other partial cross sections, (4) a 10% increase in the elastic cross section with 2% of the compensating change being taken in the total cross section and the remainder absorbed in the inelastic cross section, (5) a 10% increase in the elastic cross section with the compensating change taken totally in the inelastic cross section, (6) an increase of 20% in the first Legendre coefficient and an increase of 10% in the second coefficient of the elastic scattering angular distribution and (7) a decrease of 10% in both the first and second Legendre coefficients of the elastic scattering. Transport calculations were carried out using various physically realistic sets of perturbed cross sections, bounded by evaluator-assigned uncertainties, as well as the base set.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1975
- Accession Number
- ADA016883
Entities
People
- Andrus Niiler
- Norman E. Banks
- William B. Beverly
Organizations
- Ballistic Research Laboratory