No abstract available

No abstract available

[en] Of considerable importance in the safety analysis of nuclear power plants are methods to estimate the probability of failure-on-demand, p, of a plant component that normally is inactive and that may fail when activated or stressed. Properties of five methods for estimating from failure-on-demand data the parameters of the beta prior distribution in a compound beta-binomial probability model are examined. Simulated failure data generated from a known beta-binomial marginal distribution are used to estimate values of the beta parameters by (1) matching moments of the prior distribution to those of the data, (2) the maximum likelihood method based on the prior distribution, (3) a weighted marginal matching moments method, (4) an unweighted marginal matching moments method, and (5) the maximum likelihood method based on the marginal distribution. For small sample sizes (N = or < 10) with data typical of low failure probability components, it was found that the simple prior matching moments method is often superior (e.g. smallest bias and mean squared error) while for larger sample sizes the marginal maximum likelihood estimators appear to be best

[en] This book presents discussions of the transport description of radiation penetration, material and structural conditions in shield design, appendices and index. This book explains well the shielding against ionizing radiation, principally neutrons and photons

[en] Neutron depth profiling (NDP) is a nondestructive technique for determining the concentration of special isotopes within several microns of a sample's surface. Previous NDP analyses, however, have been restricted to samples with plane surfaces. Here samples with curved surfaces are considered. In particular, a method for estimating the energy spectrum of ions emitted from curved surfaces is presented. Also, a robust method for inverting the NDP ion energy spectra is presented that yields accurate concentration profiles for both under- and overdetermined NDP spectra

[en] A benchmark gamma-ray skyshine experiment is descibed in which ⁶⁰Co sources were either collimated into an upward 150-deg conical beam or shielded vertically by two different thicknesses of concrete. A NaI(Tl) spectrometer and a high pressure ion chamber were used to measure, respectively, the energy spectrum and the 4π-exposure rate of the air-reflected gamma photons up to 700 m from the source. Analyses of the data and comparison to DOT discrete ordinates calculations are presented

[en] Paper No. F78 702-3

[en] This user's manual presents a detailed description of two FORTRAN computer codes for analyzing component failure data. The first code SAFE-R is used to analyze data giving the number of observed failures in specified component operation times, while the second code SAFE-D is to be applied to failure data giving the number of failures observed in specified numbers of component demands. The theory behind the many analyses performed by these codes is summarized in a companion report NUREG/CR-2374 'Use of Non-Conjugate Prior Distributions in Compound Failure Models.' A description of the overall program structure and detailed use of the many program commands is presented here. A sample input is given along with the resulting output

No abstract available

[en] It is shown that for transport problems involving fine-energy-group structure or light element scattering, the elastic scattering transfer cross sections can be approximated by trapezoid-shaped distributions. In particular, for group structures of equal lethargy widths, the trapezoidal distribution reduces to a triangular shape. These approximate transfer cross sections are readily incorporated into a discrete ordinates code and often produce results superior to those obtained with conventional Legendre expansion techniques