Nuclear Data Preparation

Abstract

Today, new evaluated data are almost always prepared in the now universally accepted ENDF/B format. Between the originally evaluated data as coded in the ENDF/B format and our particle transport codes, which actually use the evaluated data, are the often overlooked data-processing codes. These data-processing codes translate and manipulate the data from the single universal ENDF/B format to a variety of formats used by our individual particle transport codes, that is, in contrast to our universally accepted evaluated data format, ENDF/B, as yet there is no universally accepted format used by all of our application codes. This chapter covers in detail the work done by our data-processing codes to prepare the evaluated data for use in our applications: this includes reconstructing energy-dependent cross sections from resonance parameters, Doppler broadening to a variety of temperatures encountered in real systems, defining data for use in both continuous energy Monte Carlo codes, as well as multigroup Monte Carlo and deterministic methods codes. In this chapter, both WHAT needs to be done by our data-processing codes and WHY have been defined; also, the overall perspective of a general plan, “The Big Picture,” for the historical and current development of the methods used over the last half century as well as today, has been given. The importance that processing code verification projects have played over the past decades as well as today has been stressed here. It should be remembered that computer codes have always been very complicated, and it is almost impossible to verify the results calculated by any one code without any comparison with one or more other independently developed codes. A classic mistake is to assume that checking the results will impede progress, whereas in fact experience has shown that taking the time to verify results can actually in the long run lead to savings in time and major improvements in the reliability of our codes.