Tài liệu miễn phí Năng lượng
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Covariance analysis for total neutron cross sections based on a microscopic optical model potential
The deterministic simple least square (LS) approach is employed in the covariance analysis of the total neutron cross section (n,tot) calculated by a microscopic optical potential, CTOM, which is based on a fundamental theory Dirac Brueckner Hartree Fock.
6/18/2020 5:45:03 AM +00:00
A study of the construction of the correlation matrix of 241Pu(nth,f) isobaric fission yields
Two blind analyses for 241Pu(nth,f) isobaric fission yields have been conducted, one analysis using a mix of a Monte-Carlo and an analytical method, the other one relying only on analytical calculations. The calculations have been derived from the same analysis path and experimental data, obtained on the LOHENGRIN mass spectrometer at the Institut Laue-Langevin.
6/18/2020 5:44:57 AM +00:00
From fission yield measurements to evaluation: status on statistical methodology for the covariance question
This study deals with the thermal neutron induced fission of 235U. The mix of data is non-unique and this topic will be discussed using the Shannon entropy criterion in the framework of the statistical methodology proposed.
6/18/2020 5:44:51 AM +00:00
Influence of nuclear structure data on fission observables
The aim of this work is to focus on nuclear structure data used at low energy where electromagnetic transitions can be measured. The RIPL3 database linked to the FIFRELIN Monte Carlo code contains such data and their influence on fission observables is reviewed.
6/18/2020 5:44:45 AM +00:00
Application of the EGPT methodology in the analysis of small-sample reactivity worth experiments
In the current paper, we investigate the application of the Equivalent Generalized Perturbation Theory (EGPT) to derive trends and associated covariances on the neutron capture cross section of one major fission product for both light water reactors and sodium-cooled fast reactors which is Rhodium-103.
6/18/2020 5:44:38 AM +00:00
Production and use of nuclear parameter covariance data: an overview of challenging cross cutting scientific issues
Most work has been done since then with spectacular achievements and enhanced understanding both of the uncertainty evaluation process and of the data utilization in V&V. This paper summarizes some key developments and still open challenges.
6/18/2020 5:44:32 AM +00:00
Resonance parameter covariance representation: file32 versus file33
Sensitivity and uncertainty analysis in error propagation studies are carried out based on nuclear data uncertainty information available in the basic nuclear data libraries such as ENDF, JEFF, JENDL and others.
6/18/2020 5:44:26 AM +00:00
Recent advances in beta decay measurements
The list of nuclei deserving new TAGS measurements has been updated recently in the frame of IAEA working groups. The issues listed above impact in the same way the predicted energy spectra of the antineutrinos from reactors computed with the summation method, the interest of which has been recently reinforced by the Daya Bay latest publication.
6/18/2020 5:44:20 AM +00:00
A stochastic method to propagate uncertainties along large cores deterministic calculations
Deterministic uncertainty propagation methods are certainly powerful and time-sparing but their access to uncertainties related to the power map remains difficult due to a lack of numerical convergence. On the contrary, stochastic methods do not face such an issue and they enable a more rigorous access to uncertainty related to the PFNS.
6/18/2020 5:44:13 AM +00:00
Estimating model bias over the complete nuclide chart with sparse Gaussian processes at the example of INCL/ABLA and double-differential neutron spectra
This paper shows how a sparse approximation to Gaussian processes can be used to estimate the model bias over the complete nuclide chart at the example of inclusive double-differential neutron spectra for incident protons above 100 MeV.
6/18/2020 5:44:07 AM +00:00
Choice of positive distribution law for nuclear data
In this paper, we will make explicit the error in the mean value and the standard deviation when using different types of distribution laws. We also employ the principle of maximum entropy as a criterion to choose among the truncated Gaussian, the fitted Gaussian and the lognormal distribution.
6/18/2020 5:44:01 AM +00:00
How to produce accurate inelastic cross sections from an indirect measurement method?
In this article, we will first discuss the issues of the prompt g-ray spectroscopy regarding the control of all the uncertainties involved in the (n,n0g) cross section estimation. Secondly, we will focus on the role of theoretical modeling which, in certain cases, is crucial to reach the objectives of a few percent uncertainty on the (n,n0) cross sections.
6/18/2020 5:43:55 AM +00:00
On the use of the BMC to resolve Bayesian inference with nuisance parameters
This paper gives an overview of the evaluation processes used for nuclear data at CEA. After giving Bayesian inference and associated methods used in the CONRAD code [P. Archier et al., Nucl. Data Sheets 118, 488 (2014)], a focus on systematic uncertainties will be given.
6/18/2020 5:43:49 AM +00:00
Template for estimating uncertainties of measured neutron-induced fission cross-sections
A template for estimating uncertainties (unc.) of measured neutron-induced fission, (n,f), cross-sections (cs) is presented. This preliminary template not only lists all expected unc. sources but also supplies ranges of unc., estimates for correlations between unc. of the same and different experiments which can be used if the information is nonexistent.
6/18/2020 5:43:43 AM +00:00
Cross-observables and cross-isotopes correlations in nuclear data from integral constraints
Most recent evaluated nuclear data files exhibit excellent integral performance, as shown by the very good agreement between experimental and calculated keff values over a wide range of benchmark integral experiments.
6/18/2020 5:43:37 AM +00:00
Potential sources of uncertainties in nuclear reaction modeling
It is also well known that the knowledge of nuclear reaction mechanisms is at best approximate, and that their modeling relies on many parameters which do not have a precise physical meaning outside of their specific implementations in nuclear model codes: they carry both specific physical information, and effective information that is related to the deficiencies of the model itself.
6/18/2020 5:43:31 AM +00:00
Bayesian optimization of generalized data
The prior PDF of generalized data is defined by prior expectation values and a prior covariance matrix of generalized data that naturally includes covariance between any two components of generalized data.
6/18/2020 5:43:25 AM +00:00
Checking, processing and verification of nuclear data covariances
The aim of this paper is to present the activities carried out by NEA Data Bank on checking, processing and verification of JEFF-3.3T4 covariances. A picture of the completeness and status of the JEFF- 3.3T4 covariances is addressed.
6/18/2020 5:43:19 AM +00:00
Nuclear data adjustment based on the interpretation of post-irradiation experiments with the DARWIN2.3 package
This paper presents a method to assimilate these integral trends for improving nuclear data. In this study, the method is applied to 137Cs/238U concentration ratio. Results suggest an increase of the JEFF-3.1.1 235U cumulated thermal fission yield in 137Cs by (+3.8 ± 2.1)%, from 6.221E-02 to 6.460E-02 ± 2.1%.
6/18/2020 5:43:12 AM +00:00
Development and validation of uncertainty neutron transport calculations at an industrial scale
In this study, COMAC nuclear data uncertainties have been propagated on the BEAVRS benchmark using a two-step APOLLO2/CRONOS2 scheme, where APOLLO2 is the lattice code used to resolve Boltzmann equation within assemblies using a high number of energy groups, and CRONOS2 is the code resolving the 3D full core diffusion equation using only four energy groups.
6/18/2020 5:43:06 AM +00:00
Uncertainties for Swiss LWR spent nuclear fuels due to nuclear data
This paper presents a study of the impact of the nuclear data (cross sections, neutron emission and spectra) on different quantities for spent nuclear fuels (SNF) from Swiss power plants: activities, decay heat, neutron and gamma sources and isotopic vectors.
6/18/2020 5:43:00 AM +00:00
A comparison of uncertainty propagation techniques using NDaST: full, half or zero Monte Carlo?
Instead of running hundreds or thousands of neutronics calculations, we therefore investigate the possibility to take those many cross-section file samples and perform ‘cheap’ sensitivity perturbation calculations. This is efficiently possible with the NEA Nuclear Data Sensitivity Tool (NDaST) and this process we name the half Monte Carlo method (HMM).
6/18/2020 5:42:53 AM +00:00
Generation of the 1H in H2O neutron thermal scattering law covariance matrix of the CAB model
This work presents an analytic methodology to produce such a covariance matrix-associated to the water model developed at the Atomic Center of Bariloche (Centro Atomico Bariloche, CAB, Argentina).
6/18/2020 5:42:47 AM +00:00
CADOR “Core with Adding DOppleR effect” concept application to sodium fast reactors
This study shows that, by applying this CADOR approach to a Generation-IV oxide-fuelled SFR, the resulting core can be made inherently resistant to reactivity insertion accidents, while also having increased resistance to loss-of-coolant accidents.
6/18/2020 5:42:41 AM +00:00
Sensitivity and uncertainty analysis of beff for MYRRHA using a Monte Carlo technique
This paper presents a nuclear data sensitivity and uncertainty analysis of the effective delayed neutron fraction beff for critical and subcritical cores of the MYRRHA reactor using the continuous-energy Monte Carlo N-Particle transport code MCNP.
6/18/2020 5:42:35 AM +00:00
Comments on the status of modern covariance data based on different fission and fusion reactor studies
Both the availability and the quality of covariance data improved over the last years and many recent cross-section evaluations, such as JENDL-4.0, ENDF/B-VII.1, JEFF-3.3, etc. include new covariance data compilations.
6/18/2020 5:42:29 AM +00:00
Uncertainty quantification works relevant to fission yields and decay data
In the present paper, firstly, we review our previous works on uncertainty quantification (UQ) of reactor physics parameters. This consists of (1) development of numerical tools based on the depletion perturbation theory (DPT), (2) linearity of reactor physics parameters to nuclear data, (3) UQ of decay heat and its reduction, and (4) correlation between decay heat and b-delayed neutrons emission.
6/18/2020 5:42:23 AM +00:00
Nuclear data correlation between different isotopes via integral information
This paper presents a Bayesian approach based on integral experiments to create correlations between different isotopes which do not appear with differential data. A simple Bayesian set of equations is presented with random nuclear data, similarly to the usual methods applied with differential data.
6/18/2020 5:42:16 AM +00:00
On the influence of the americium isotopic vector on the cooling time of minor actinides bearing blankets in fast reactors
In the heterogeneous minor actinides transmutation approach, the nuclei to be transmuted are loaded in dedicated targets often located at the core periphery, so that long-lived heavy nuclides are turned into shorter-lived fission products by fission.
6/18/2020 5:42:10 AM +00:00
A methodology for performing sensitivity analysis in dynamic fuel cycle simulation studies applied to a PWR fleet simulated with the CLASS tool
In this paper, a focus is made on the methodology based on GSA. This innovative methodology is presented and applied to a simple fleet simulation composed of a PWR-UOx fuel and a PWR-MOx fuel. Calculations are done with the fuel cycle simulator CLASS developed by the CNRS/IN2P3 in collaboration with IRSN.
6/18/2020 5:42:04 AM +00:00