scholarly journals ARIADNE – a program estimating covariances in detail for neutron experiments

2018 ◽  
Vol 4 ◽  
pp. 34 ◽  
Author(s):  
Denise Neudecker
Keyword(s):  
Experimental Data ◽  
Uncertainty Quantification ◽  
Nuclear Data ◽  
Fission Neutron ◽  
Efficient Manner ◽  
Plain Text ◽  
Uncertainty Sources ◽  
Evaluation Community ◽  
Prompt Fission ◽  
Prompt Fission Neutron

The python program ARIADNE is a tool developed for evaluators to estimate detailed uncertainties and covariances for experimental data in a consistent and efficient manner. Currently, it is designed to aid in the uncertainty quantification of prompt fission neutron spectra, and was employed to estimate experimental covariances for CIELO and ENDF/B-VIII.0 evaluations. It provides a streamlined way to estimate detailed covariances by (1) implementing uncertainty quantification algorithms specific to the observables, (2) defining input quantities for typically encountered uncertainty sources and correlation shapes, and (3) automatically generating plots of data, uncertainties and correlations, GND formatted XML and plain text output files. Covariances of the same and between different datasets can be estimated, and tools are provided to assemble a database of experimental data and covariances for an evaluation based on ARIADNE outputs. The underlying IPython notebook files can be easily stored, including all assumptions on uncertainties, leading to more reproducible inputs for nuclear data evaluations. Here, the key inputs and outputs are shown along with a representative example for the current version of ARIADNE to illustrate its usability and to open a discussion on how it could address further needs of the nuclear data evaluation community.

scholarly journals Observations of poorly-known features of the 239Pu and 235U prompt fission neutron spectra

2020 ◽  
Vol 239 ◽  
pp. 05010
Author(s):  
Keegan J. Kelly ◽  
Jaime A. Gomez ◽  
John M. O'Donnell ◽  
Matthew Devlin ◽  
Robert C. Haight ◽  
...  
Keyword(s):  
Experimental Data ◽  
Neutron Spectrum ◽  
Neutron Emission ◽  
National Laboratory ◽  
Nuclear Data ◽  
Fission Neutron ◽  
Fission Neutron Spectrum ◽  
Wide Range ◽  
Prompt Fission ◽  
Prompt Fission Neutron

Prompt fission neutron spectrum (PFNS) evaluations use provide nuclear data for the PFNS across a wide range of incident and outgoing neutron energies. However, experimental data underlying the evaluation are sparse, inconsistent, and incomplete with respect to the desired incident and outgoing energy coverage. As such, evaluations sometimes predict features of the PFNS, such those relating to multi-chance fission and pre-equilibrium pre-fission neutron emission, without any experimental validation. The Chi-Nu experiment at Los Alamos National Laboratory has recently obtained high-precision results for the 239Pu and 235U PFNS which, for the first time in both cases, have shed light on multi-chance fission and pre-equilibrium contributions to the observed fission neutron spectrum. In addition to providing the first experimental data on some of these fission properties, the angular coverage of the Chi-Nu experiment allows for the extraction of angular distributions of pre-equilibrium pre-fission neutrons. PFNS results of multi-chance fission and pre-equilibrium pre-fission neutron emission are discussed in this proceedings in terms of the observed neutron spectrum and the average PFNS energies.

Uncertainty Quantification of Prompt Fission Neutron Spectrum forn(0.5 MeV) +239Pu

2010 ◽  
Vol 166 (3) ◽  
pp. 254-266 ◽  
Author(s):  
P. Talou ◽  
T. Kawano ◽  
D. G. Madland ◽  
A. C. Kahler ◽  
D. K. Parsons ◽  
...  
Keyword(s):  
Uncertainty Quantification ◽  
Neutron Spectrum ◽  
Fission Neutron ◽  
Fission Neutron Spectrum ◽  
Prompt Fission Neutron Spectrum ◽  
Prompt Fission ◽  
Prompt Fission Neutron

scholarly journals Systematic Distortion Factor and Unrecognized Source of Uncertainties in Nuclear Data Measurements and Evaluations

Metrology ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 1-18
Author(s):  
Nikolay V. Kornilov ◽  
Vladimir G. Pronyaev ◽  
Steven M. Grimes
Keyword(s):  
Cross Sections ◽  
Nuclear Data ◽  
Fission Neutron ◽  
Model Case ◽  
Distortion Factor ◽  
True Value ◽  
New Information ◽  
Measurement Results ◽  
Prompt Fission ◽  
Prompt Fission Neutron

Each experiment provides new information about the value of some physical quantity. However, not only measured values but also the uncertainties assigned to them are an important part of the results. The metrological guides provide recommendations for the presentation of the uncertainties of the measurement results: statistics and systematic components of the uncertainties should be explained, estimated, and presented separately as the results of the measurements. The experimental set-ups, the models of experiments for the derivation of physical values from primary measured quantities, are the product of human activity, making it a rather subjective field. The Systematic Distortion Factor (SDF) may exist in any experiment. It leads to the bias of the measured value from an unknown “true” value. The SDF appears as a real physical effect if it is not removed with additional measurements or analysis. For a set of measured data with the best evaluated true value, their differences beyond their uncertainties can be explained by the presence of Unrecognized Source of Uncertainties (USU) in these data. We can link the presence of USU in the data with the presence of SDF in the results of measurements. The paper demonstrates the existence of SDF in Prompt Fission Neutron Spectra (PFNS) measurements, measurements of fission cross sections, and measurements of Maxwellian spectrum averaged neutron capture cross sections for astrophysical applications. The paper discusses introducing and accounting for the USU in the data evaluation in cases when SDF cannot be eliminated. As an example, the model case of 238U(n,f)/235U(n,f) cross section ratio evaluation is demonstrated.

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