Engineering topics
Publications and source records attributed to Guber, Klaus.
In this presentation the 51 V evaluation in response to NCSP need is completed. Issues in connection to RR representation are addressed. Uncertainty and covariance information derived with the evaluation. Evaluation proposed and accepted for inclusion in ENDF/B-VIII.1 library.
A resolved resonance region evaluation of 140,142 Ce was conducted by Oak Ridge National Laboratory. Requested by the US Nuclear Criticality Safety Program, this evaluation is based on recent high-resolution transmission and capture high-resolution measurements of nat Ce and 142 Ce conducted at JRC-Geel at the Geel Linear Accelerator facility. It is also based on recently measured thermal constants available from the EX FOR database. Starting from the resonance parameters from the ENDF/B-VIII.0 library and following a preliminary R-matrix analysis, an updated set of resonance parameters and corresponding covariance in formation was derived by the fit of these experimental datasets using the Reich–Moore approximation of the R-matrix theory, as implemented in the SAMMY code system. The resolved resonance region upper energy limit for 140 Ce was kept at 200 keV, whereas the 142 Ce resonance region was extended from 13 to 26 keV. This new evaluation was found to be in good agreement not only with several integral quantities of interest to the reactor physics community, but also with the stellar Maxwellian-averaged cross section.
This lecture provides details on the status of ORNL TSL evaluations. Main sections include modeling of concrete, updates of polyethylene evaluation, and initial transmission measurements at Oak Ridge National Labatory (ORNL). The presentation Conclusions show that literature review and initial modeling of concrete components have been performed. INS and transmission measurements of concrete and hydrated cement have been also planned. Additionally, A new TSL library for Polyethylene was created and submitted to NNDC and development for a new transmission capability at ORNL is underway.
Nuclear criticality modeling and simulations rely on the quality of the existing evaluated nuclear data libraries such as Evaluated Nuclear Data File (ENDF)/B, the Joint Evaluated Fission and Fusion (JEFF) nuclear data library, or the Japanese Evaluated Nuclear Data Library (JENDL). In some cases, the cross-section evaluations of those libraries were found to be deficient in describing criticality benchmarks accurately. More than two decades ago, the US Nuclear Criticality Safety Program (NCSP) established a Nuclear Data (ND) task which encompassed experiments and evaluations. In response to this, the Oak Ridge National Laboratory (ORNL) formed a Nuclear Criticality and Data group which performed ND experiments, data analysis, and evaluations to produce ENDF files for the ND libraries as identified in the NCSP Five-Year Plan. Before being submitted to the ENDF library, files were processed and tested for performance by running benchmark calculations. This procedure was centralized in the ORNL group and is now often referred to as the ND pipeline. NCSP collaborates with the Joint Research Center (JRC) of the European Commission in Geel, Belgium, to perform high-resolution neutron-induced cross section measurements at the Geel Linear Accelerator (GELINA). The objective is to address emerging ND problems in criticality calculations. Difficulties with ND include insufficient neutron energy range, missing covariances, and previously unrecognized inaccuracies with experiments. New neutron total and capture cross sections of 90 Zr in the neutron energy range from 100 eV to several hundred keV were recently performed. These measured data will be used, together with existing high-resolution transmission data from a metallic 90 Zr sample, to improve representation of the cross sections.
This presentation covers key take-aways such as the first of 4 isotopes (90,91,92,94) to be measured. 91 Zr is currently being measured at GELINA. Once all measurements are done a join evaluation with SAMMY will be undertaken. Further, there will be production of new evaluated resonance parameters and covariances. New data will be used to improve evaluation information, benefitting transport calculations of reactors, waste storage, etc.
ORNL has completed new RRR evaluations for 140,142 Ce. A lack of integral measurements made validation difficult, but the difference from Kadonis values suggests that more investigation of capture cross section is warranted. The complete file (with updated File2 and File32) has been submitted to NNDC repository for inclusion in next release of ENDF. A sponsor report publication is in progress.
A resolved resonance region evaluation of 140,142 Ce has been carried out by Oak Ridge National Laboratory. Requested by the US Nuclear Criticality Safety Program, this evaluation is based on recent high-resolution transmission and capture high-resolution measurements of nat Ce and 142 Ce conducted at JRC-GEEL at the Geel Linear Accelerator facility, as well as recently measured thermal constants available from the EXFOR database. Starting from the resonance parameters from the ENDF/B-VIII.0 library and following a preliminary R-matrix analysis, an updated set of resonance parameters and corresponding covariance information was derived by the fit of these experimental datasets using the Reich-Moore approximation of the R-matrix theory as implemented in the SAMMY code system. The resolved resonance region upper energy limit for 140 Ce was kept at 200 keV while the 142 Ce resonance region was extended from 13 to 26 keV. This new evaluation was found to be in good agreement not only with several integral quantities of interest to the reactor physics community, but also with the stellar Maxwellian-averaged cross section.
Abstract not provided.
Luiz Leal's idea to integrate the experimental uncertainties, covariances, and sensitivities in this workflow and centralize the process at one location led to the creation of a cohesive tool for data testing. It has been practiced for more than two decades by the NCS and ND groups at ORNL. The development and use of the ORNL codes TSUNAMI and TSURFER within SCALE made it possible. Today, it has been extended to SAMINT which enables the coupling of differential and integral data evaluation in a continuous-energy framework.
The generalized form of the Bayes’ Theorem improves UQ for NCSP of differential and/or integral data evaluations and of applications. It is being implemented in an API for use by SCALE, SAMMY, etc. Extended R-matrix formalism improves evaluations of RRR including direct reactions, direct capture, and the Reich-Moore approx., doorway state reactions with applications to RPI data on lead isotopes. Extended R-Matrix formalism will be implemented into SAMMY post modernization.
ORNL has completed new resolved resonance region (RRR) evaluations for 140,142 Ce, which were carried out using Reich-Moore formalism instead of MLBW. Lack of integral measurements makes validation difficult, but difference from Kadonis values suggest more investigation of capture cross section are warranted. The complete file (with updated File2 & File32) was submitted to NNDC repository for inclusion in next release of ENDF. Sponsor report and journal publication are in progress.
Luiz Leal's idea to integrate the experimental uncertainties, covariances, and sensitivities in the ND workflow and to centralize the process at one location created a cohesive tool for data testing. It has been practiced for more than two decades by the NCS and ND groups at ORNL. The development and use of the ORNL codes TSUNAMI and TSURFER within SCALE made it possible. Today, it has been extended to SAMINT, which enables the coupling of differential and integral data evaluation in a continuous-energy framework.
Abstract not provided.
Topics for the meeting were as follows: Safety Minute, High-level Overview of NCRTS, Overview of NCRTS Groups (Radiation Transport, Nuclear Data, and Nuclear Criticality Safety), and Question and Answer.
Transmission measurements have been performed at the time-of-flight facility GELINA to provide data for a new evaluation of neutron resonance parameters for 142 Ce. The measurements were carried out at a 50 m transmission station using a Li-glass scintillator with the accelerator operating at 400 Hz. This report provides the experimental details required to deliver the data to the EXFOR data library, maintained by the International Network of Nuclear Reaction Data Centres (NRDC). The experimental conditions and data reduction procedures are described. In addition, the full covariance information based on the AGS concept is given such that resonance parameters together with their covariances can be derived in a least-squares adjustment to the data.
The presentation covers an overview of 140,142 Ce Isotopes, including new evaluations of 140,142 Ce that were requested by the Hanford Plutonium Finishing plant to the Nuclear Criticality Safety Program. It also discusses current ENDF/B-VIII.0 evaluation, which has an error in the 1-2 keV range. It was evaluated using multi-level Breit-Wigner and 142Ce has room for extending resolved resonance region current upper limit from 13 keV. The presentation also discusses new transmission and capture measurements of nat Ce and 142 Ce from Klaus Guber. It also states that no known integral experiments prominently feature Cerium.
Experiments for 142 Ce have been performed in 2019. The data are reduced to cross section and transmission, respectively. Report for 142 Ce experiments is in preparation. Data analysis is underway, and the evaluation should be finalized by the end of 2020. 90 Zr sample is produced, but experiments planned for 2020 are delayed due to COVID-19.
Abstract not provided.