New approaches to provide feedback from nuclear and covariance data adjustment for effective improvement of evaluated nuclear data files

A critical examination of the role of uncertainty assessment, target accuracies, role of integral experiment for validation and, consequently, of data adjustments methods is underway since several years at OECD-NEA, the objective being to provide criteria and practical approaches to use effectively the results of sensitivity analyses and cross section adjustments for feedback to evaluators and experimentalists in order to improve without ambiguities the knowledge of neutron cross sections, uncertainties, and correlations to be used in a wide range of applications and to meet new requirements and constraints for innovative reactor and fuel cycle system design. An approach will be described that expands as much as possible the use in the adjustment procedure of selected integral experiments that provide information on “elementary” phenomena, on separated individual physics effects related to specific isotopes or on specific energy ranges. An application to a large experimental data base has been performed and the results are discussed in the perspective of new evaluation projects like the CIELO initiative

A Global Approach to the Physics Validation of Simulation Codes for Future Nuclear Systems

This paper presents a global approach to the validation of the parameters that enter into the neutronics simulation tools for advanced fast reactors with the objective to reduce the uncertainties associated to crucial design parameters. This global approach makes use of sensitivity/uncertainty methods; statistical data adjustments; integral experiment selection, analysis and “representativity” quantification with respect to a reference system; scientifically based cross section covariance data and appropriate methods for their use in multigroup calculations. This global approach has been applied to the uncertainty reduction on the criticality of the Advanced Burner Reactor, (both metal and oxide core versions) presently investigated in the frame of the GNEP initiative. The results obtained are very encouraging and allow to indicate some possible improvements of the ENDF/B-VII data file

New approaches to provide feedback from nuclear and covariance data adjustment for effective improvement of evaluated nuclear data files

A critical examination of the role of uncertainty assessment, target accuracies, role of integral experiment for validation and, consequently, of data adjustments methods is underway since several years at OECD-NEA, the objective being to provide criteria and practical approaches to use effectively the results of sensitivity analyses and cross section adjustments for feedback to evaluators and experimentalists in order to improve without ambiguities the knowledge of neutron cross sections, uncertainties, and correlations to be used in a wide range of applications and to meet new requirements and constraints for innovative reactor and fuel cycle system design. An approach will be described that expands as much as possible the use in the adjustment procedure of selected integral experiments that provide information on “elementary” phenomena, on separated individual physics effects related to specific isotopes or on specific energy ranges. An application to a large experimental data base has been performed and the results are discussed in the perspective of new evaluation projects like the CIELO initiative

Avancées dans le calcul neutronique des réacteurs à neutrons rapides au CEA

Ouverture européenne et relance des recherches de base sont les mots-clés du développement de la physique neutronique au CEA

CONTRIBUTION A UNE PROPOSITION D'UN DEVELOPPEMENT A LONG TERME REVOLUTIONNAIRE DE L'ENERGIE NUCLEAIRE

EVRY-BU (912282101) / SudocSudocFranceF

Method and approaches to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data files: Major findings of the NEA WPEC Subgroup 39

Nuclear data adjustments using integral experiments play since several decades a crucial role in providing reactor designers and fuel cycle analysts with nuclear data with reduced and validated uncertainties in order to allow design optimization while meeting safety and economics requirements. Adjustment methods, choice of integral experiments and covariance data assessment should be carefully defined in order to produce credible and physically acceptable adjustments, applicable to a wide range of systems. The OECD-NEA has established a series of Expert Groups since 2005 to investigate the key scientific issues and to provide recommendations for applications. The present paper discusses the major results of the most recent of these Expert Groups together with an indication of the path forward

Developments in Sensitivity Methodologies and the Validation of Reactor Physics Calculations

The sensitivity methodologies have been a remarkable story when adopted in the reactor physics field. Sensitivity coefficients can be used for different objectives like uncertainty estimates, design optimization, determination of target accuracy requirements, adjustment of input parameters, and evaluations of the representativity of an experiment with respect to a reference design configuration. A review of the methods used is provided, and several examples illustrate the success of the methodology in reactor physics. A new application as the improvement of nuclear basic parameters using integral experiments is also described

DETERMINATION DE SCHEMAS D'EMPOISONNEMENT POUR LE CONTROLE DE LA REACTIVITE DE COMBUSTIBLES INNOVANTS. APPLICATION AUX CERMET AU PLUTONIUM

UN DES PRINCIPAUX SOUCIS DANS LE CONTEXTE ACTUEL DU NUCLEAIRE EST CONSTITUE PAR L'ACCUMULATION DE STOCKS DE PLUTONIUM, PROVENANT D'UNE PART DU COMBUSTIBLE DECHARGE DES REACTEURS ACTUELS ET D'AUTRE PART DU DEMANTELEMENT DES ARMES NUCLEAIRE. CES STOCKS REPRESENTENT UN PROBLEME DU POINT DE VUE DE LA SECURITE DES INSTALLATIONS ET DE LA PROLIFERATION, AINSI QU'UNE SOURCE POTENTIELLE D'ENERGIE ET DIFFERENTES STRATEGIES SONT A L'ETUDE AFIN DE LES UTILISER. DANS UN SCENARIO A COURT TERME, ON PROJETTE D'UTILISER LE PLUTONIUM DANS LES REACTEURS A EAU. DANS CE CONTEXTE, LES COMBUSTIBLES A MATRICE INERTE (CONSTITUES PAR DES GRAINS DE MATIERE FISSILE DISPERSES DANS UNE MATRICE INERTE) REPRESENTENT UNE SOLUTION PROMETTEUSE. PLUSIEURS MATERIAUX INERTES SONT A L'ETUDE POUR ETRE UTILISES COMME MATRICE : ON A CHOISI D'ANALYSER LES COMBUSTIBLES A MATRICE METALLIQUE (CERMET), PUISQUE LA GRANDE CONDUCTIVITE THERMIQUE DES METAUX PERMETTRAIT DE REALISER UN COMBUSTIBLE A FAIBLE TEMPERATURE DE FONCTIONNEMENT. DU POINT DE VUE NEUTRONIQUE, L'ABSENCE DE L'URANIUM CONDUIT A DES PARAMETRES DE CONTROLE TRES PENALISANTS ET NOTAMMENT A UNE FORTE DEGRADATION DU COEFFICIENT DOPPLER, DE L'EFFET DE VIDE ET DE LA FRACTION EFFECTIVE DE NEUTRONS RETARDES, AINSI QU'A UNE PERTE D'EFFICACITE DES MOYENS DE CONTROLE TRADITIONNELS. L'OBJECTIF PRINCIPAL QUE L'ON SE FIXE EST DE MAITRISER CES PROBLEMES DE CONTROLE A TRAVERS L'ETUDE DE LA PHYSIQUE DE BASE DE CES COMBUSTIBLES. L'ANALYSE PHYSIQUE MONTRERA QU'IL EST NECESSAIRE : UTILISER UNE MATRICE A FAIBLE ABSORPTION NEUTRONIQUE, POUR OBTENIR UN EFFET DE VIDE ET UNE EFFICACITE DU BORE ACCEPTABLES ; UTILISER UN POISON CONSOMMABLE, POUR POUVOIR CONTROLER L'EXCES DE REACTIVITE INITIALE ; ADOPTER UN CHARGEMENT HETEROGENE DU CUR, POUR OBTENIR UN COEFFICIENT DOPPLER ET UNE FRACTION DES NEUTRONS RETARDES CONVENABLES.EVRY-BU (912282101) / SudocSudocFranceF