Engineering topics

Kahler, Albert C.

Publications and source records attributed to Kahler, Albert C..

4 records

DOE OSTI2018

Evaluations of Energy Spectra of Neutrons Emitted Promptly in Neutron-induced Fission of 235 U and 239 Pu

The energy spectra of neutrons emitted promptly in the neutron-induced fission reactions of 235 U and 239 Pu were re-evaluated for ENDF/B-VIII.0. The evaluations presented here are based on a careful modeling of all relevant physics processes, an extensive analysis of experimental data and a detailed quantification of pertinent uncertainties. Energy spectra of neutrons emitted in up to fourth chance fission are considered and both compound and pre-equilibrium processes are included. Also, important nuclear model parameters, such as the average total kinetic energy of the fission fragments and the multiple chance fission probabilities, and their uncertainties are estimated based on experimental knowledge, model information and evaluated data. In addition to experimental information already available for ENDF/B-VII.1, these new evaluations make use of recently published experimental data either of high precision or spanning a broad incident energy range, information on legacy measurements explaining discrepancies and recently measured data of the average total kinetic energy as a function of incident neutron energy. The resulting evaluated data and covariances agree well with the experimental database used for the evaluation. However, the evaluated spectra are softer than the 235 U and 239 Pu ENDF/B-VII.1, JENDL-4.0 and JEFF-3.2 evaluations for incident neutron energies E inc ≤ 1.5 MeV and E inc ≤ 5 MeV, respectively. For E inc > 5 MeV, the evaluated spectra show structures due to the improved modeling which are not present in ENDF/B-VII.1 and JEFF-3.2 but can be observed in JENDL-4.0 evaluations. Part of these new evaluations were adopted for ENDF/B-VIII.0, while the ENDF/B-VII.1 239 Pu PFNS was retained for E inc ≤ 5 MeV awaiting more conclusive experimental evidence.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2016

Integral Experiment Request 209 (CED-2 Summary Report)

This report examines proposed Seven Percent Critical Experiment (7uPCX) experiments with fuel arrays larger than would be critical when fully reflected. In these experiments, the reactivity of the assembly will be controlled by varying the moderator/reflector level in the core tank. The analysis uses two configurations, each completely filling the 45x45 fuel rod array with fuel rods and water holes, as representative examples of the proposed experiments. The proposed configurations are compared to the experiments documented in LEU-COMP-THERM-078 [Reference 1] and to fully-reflected experiments with the same fully-loaded fuel arrays that are poisoned with boron in the moderator. The conclusion is drawn that the proposed experiments can be performed with acceptably low uncertainties given a calibrated moderator/reflector level measurement system.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2015

Impact of new prompt fission neutron spectrum evaluations and the associated cross-correlations on critical assemblies using MCNP6 - 14385

Two recent re-evaluations of the neutron-induced prompt fission neutron spectrum (PFNS) of uranium and plutonium actinides have included some cross-correlated uncertainties that have not been released in a new nuclear data library. The first re-evaluation included cross-isotope correlations of the PFNS within each of the uranium and plutonium suites of actinides below the second-chance fission threshold. The second, more recent re-evaluation includes incident energy-dependent correlations of the {sup 239}Pu(n,f) PFNS. Both of these new evaluations and their cross-correlations, given the importance of these actinide quantities and because the impact of the incident energy-dependent correlations has never been studied previously, could have an impact on a variety of criticality safety applications. For example, the ke uncertainty due to the uranium PFNS uncertainties in the Big Ten critical assembly is underpredicted by ∼10% when the cross-isotope correlations in the uranium PFNS are ignored. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2014

Applications of Integral Benchmark Data

The International Reactor Physics Experiment Evaluation Project (IRPhEP) and the International Criticality Safety Benchmark Evaluation Project (ICSBEP) provide evaluated integral benchmark data that may be used for validation of reactor physics / nuclear criticality safety analytical methods and data, nuclear data testing, advanced modeling and simulation, and safety analysis licensing activities. The handbooks produced by these programs are used in over 30 countries. Five example applications are presented in this paper: (1) Use of IRPhEP Data in Uncertainty Analyses and Cross Section Adjustment, (2) Uncertainty Evaluation Methods for Reactor Core Design at JAEA Using Reactor Physics Experimental Data, (3) Application of Benchmarking Data to a Broad Range of Criticality Safety Problems, (4) Cross Section Data Testing with ICSBEP Benchmarks, and (5) Use of the International Handbook of Evaluated Reactor Physics Benchmark Experiments to Support the Power Industry.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗