[en] Background and Motivation Within the adjustment-expert community it has been generally known that, in applications for which the linearity assumption is valid, there is no point in re-adjusting the just adjusted parameters by the simultaneously adjusted responses. Starting from a given parameter library p and a given set of measured responses r, and adjusting the former by the latter, we achieve an adjusted library and the corresponding set of adjusted responses p.r.. If we then carefully apply the adjustment prescriptions to these adjusted quantities, we realize that the re-adjusted library p. is identical to , as indeed is p.r.. to r.. A formal demonstration of the above was presented at the latest Symposium on Reactor Dosimetry

[en] The two parameters one response model of the generalized linear least squares parameter adjustment methodology was used in order to analyze the procedure of improving cross sections agreement with integral experimental results. Two extreme adjustment cases were considered. One case is using extremely accurate measured integral responses, such as k_eff of Godiva or Jezebel for instance. The other one is modifying only one parameter, for instance the modification of ν-bar in ENDF/B-VII, in order to improve agreement of calculated responses with corresponding integral measurements results. In both cases new posterior parameters correlations are generated. The conclusion is that it is not advised to use integral measurements information in the evaluation process of a general purpose nuclear data file. (authors)

[en] The Generalized Linear Least-Squares Cross-Section Adjustment methodology, used in criticality safety problems can handle prior parameter correlations and prior response-parameter correlations. In this work the two parameters one response model of the generalized linear least squares parameter adjustment methodology was used in order to analyze the procedure of improving cross sections agreement with integral experimental results by tuning. The tuning procedure can be achieved by modifying only one parameter, for instance the modification of in ENDF/B-VII.0, in order to improve agreement of calculated responses with corresponding integral measurements results. The two parameters one response model formulas will be presented and reduced to a tuning simulation mode, analyzed and illustrated by a criticality numerical example

[en] The fission spectrum can be analytically represented in several different forms, such as a simple Maxwellian, the Watt fission spectrum, or the more modern and physically sound Madland-Nix representation. A quantitative estimate of the uncertainty matrix associated with the fission spectrum is needed in many nuclear data applications. Criticality safety, neutron cross section adjustment and reactor pressure vessel surveillance dosimetry are just a few examples

[en] The fission spectrum uncertainty (variance covariance) matrix is needed in many nuclear data applications. Unfortunately, most modern evaluated data files, with the exception of JENDL3.3, do not include information on the fission spectrum uncertainly. In this paper, the fission spectrum relative uncertainty matrix derivation for the Watt fission spectrum is followed by a more general derivation utilizing some characteristics of any fission spectrum. In the second derivation, the Watt spectrum is used only for the calculation of sensitivity coefficients. (authors)

[en] This paper documents the results obtained in an adjustment study of cross section parameters as well as k_eff responses of 19 spherical plutonium critical assemblies, utilizing the new TSURFER (Tool for Sensitivity/Uncertainty Analysis of Response Functionals Using Experimental Results) module. Special attention was devoted to the sensitivity of the results to the available variance-covariance data and supplements for the responses and parameters. (authors)