Evaluation of anisotropy effects in pressure vessel fluence calculations using the BUGLE-93 library

Pressure vessel fluence calculations are usually performed using multi-group discrete ordinates (S{sub N}) theory codes (e.g., DORT code{sup 3}), three-dimensional synthesis, and a broad-group library [typically {approximately}50 energy groups, P{sub 3} anisotropy e.g., SAILOR, BUGLE-80, and ELXSIR]. Regulations (as well as good engineering practices) require assessing calculational uncertainties due to various assumptions, approximations, and/or uncertainties in the methodology and input data. Broad-group cross-section libraries generated for shielding applications in the 1980s were limited to P{sub 3} Legendre expansion to represent the anisotropy in the scattering cross sections and based on the ENDF/B-IV and ENDF/B-V evaluations. Recently, a new library, BUGLE-93, was generated with higher order Legendre expansion (P{sub 7} for Z < 30 elements and P{sub 5} and Z {ge} 30 elements) based on the latest ENDF/B-VI evaluations. This paper examines the effect of the Legendre expansion order (up to P{sub 7}) for pressure vessel fluence calculations; furthermore, the paper contributes to the validation of the BUGLE-93 library.