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Development of a Methodology for Nuclear Data Assimilation in Reactor Physics employing the PROTEUS Experimental Data Base

English title Development of a Methodology for Nuclear Data Assimilation in Reactor Physics employing the PROTEUS Experimental Data Base
Applicant Pautz Andreas
Number 156080
Funding scheme Project funding (Div. I-III)
Research institution Unité de Prof. Pautz EPFL - SB - IPEP - UPPAUTZ
Institution of higher education EPF Lausanne - EPFL
Main discipline Other disciplines of Engineering Sciences
Start/End 01.10.2015 - 31.10.2018
Approved amount 177'463.00
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Keywords (4)

Nuclear Data Assimilation; Sensitivity/Uncertainty Analysis; Molten Salt Reactor; PROTEUS Experiments

Lay Summary (German)

Lead
Die Bewertung der Sicherheit nuklearer Anlagen stützt sich weitgehend auf Computersimulationen, mit denen der Kritikalitätszustand des Systems, die Effizienz von Abschirmungen gegen radioaktive Strahlung oder das dynamische Verhalten der Anlage unter Störfallbedingungen untersucht werden kann. Diese Rechenprogramme benötigen einerseits als wichtigen Input Nukleardaten in Form sog. Wirkungsquerschnitte, die in grossen, internationalen Datenbanken der Öffentlichkeit zur Verfügung stehen. Andererseits müssen die Computersimulationen anhand von Experimenten validiert werden, d.h. es muss gezeigt werden, dass die Rechenergebnisse die experimentellen Daten hinreichend genau reproduzieren. Schliesslich stellt sich die Frage, ob die verfügbaren Experimentaldaten repräsentativ für die geplante technische Anwendung sind, d.h. können z.B. Ergebnisse hinsichtlich des Kritikalitätszustandes eines (vergleichsweise kleinen) Forschungsreaktors auf eine grosstechnische Anlage übertragen werden.
Lay summary

Inhalt und Ziel des Forschungsprojekts

Die Validierung von Simulationsprogrammen für die Bewertung der Sicherheit von Nuklearanlagen ist eine der zentralen Aufgaben der Reaktorphysik. Hierfür stehen in erster Linie Experimentaldaten von sog. "kalten" kritischen Anordnungen, wie z.B. dem Forschungsreaktor PROTEUS am Paul-Scherrer-Institut (Villigen AG) zur Verfügung, während Messdaten von Kraftwerksanlagen kaum oder nicht in ausreichender Messgenauigkeit vorliegen. Insbesondere beim Design einer neuen Nuklearanlage, sei es nun ein Leistungsreaktor, eine Transmutationsanlage oder ein Lager für radioaktive Abfälle stellt sich stets die Frage: sind die zum Design verwendeten Computerprogramme hinreichend für die neue Anwendung validiert und können beobachtete systematische Abweichungen Messung/Rechnung zuverlässig von Experimenten auf die Zielanwendung extrapoliert werden. Darüber hinaus möchte man in der Lage sein, die Unsicherheiten in diesen systematischen Abweichungen zu quantifizieren. Nur so gelingt es, die Grenzen der nuklearen Auslegung auszuloten und entsprechende Sicherheitsmargen im Design zu berücksichtigen. In diesem Forschungsprojekt greifen wir die Fragestellung von zwei Seiten an, nämlich a) durch Verbesserung der experimentellen Datenbasis, und b) durch Entwicklung einer neuen Software zur Datenassimilation und Unsicherheits-/Sensitivitätsanalyse von nuklearen Daten. Insbesondere schaffen wir eine umfangreiche Experimentaldatenbank, um die Messdaten aus mehr als 40 Jahren PROTEUS-Betrieb zu kategorisieren und zu sichern.

Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts

Dieses Projekt leistet einen wichtigen Beitrag zum Verständnis des Einflusses von nuklearen Datenunsicherheiten auf die Sicherheitsanalyse von Nuklearanlagen, insbesondere in den Bereichen Kritikalität und Reaktorkernauslegung. Die zu entwickelnde Methodik soll auf existierende bzw. projektierte Kernanlagen ebenso anwendbar sein wie auf zukünftige fortgeschrittene oder innovative Reaktorkonzepte.

Direct link to Lay Summary Last update: 27.04.2015

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
On data assimilation with Monte-Carlo-calculated and statistically uncertain sensitivity coefficients
Siefman D., Hursin M., Aufiero M., Bidaud A., Pautz A. (2020), On data assimilation with Monte-Carlo-calculated and statistically uncertain sensitivity coefficients, in Annals of Nuclear Energy, 135, 106951-106951.
Data Assimilation with Post Irradiation Examination Experiments
Siefman Daniel, Hursin Mathieu, Pautz Andreas (2019), Data Assimilation with Post Irradiation Examination Experiments, in Nuclear Data 2019, Beijing, ChinaResearchGate, Beijing.
Stochastic vs. sensitivity-based integral parameter and nuclear data adjustments
Siefman D., Hursin M., Rochman D., Pelloni S., Pautz A. (2018), Stochastic vs. sensitivity-based integral parameter and nuclear data adjustments, in The European Physical Journal Plus, 133(10), 429-429.
REPRESENTATIVITY ANALYSIS OF THE LWR-PROTEUS PHASE II EXPERIMENTS USING SHARKX STOCHASTIC SAMPLING METHOD
Hursin Mathieu, Siefman Daniel, Perret Gregory, Pautz Andreas (2018), REPRESENTATIVITY ANALYSIS OF THE LWR-PROTEUS PHASE II EXPERIMENTS USING SHARKX STOCHASTIC SAMPLING METHOD, in ANS Best Estimate Plus Uncertainty International Conference (BEPU 2018), Lucca, ItalyResearchGate, Lucca, Italy.
Convergence Analysis and Criterion for Data Assimilation with Sensitivities from Monte Carlo Neutron Transport Codes
Siefman Daniel, Hursin Mathieu, Aufiero Manuele, Bidaud Adrien, Pautz Andreas (2018), Convergence Analysis and Criterion for Data Assimilation with Sensitivities from Monte Carlo Neutron Transport Codes, in PHYSOR 2018: Reactors Physics paving the way towards more efficient systems, Cancun, MexicoResearchGate, Cancun, Mexico.
DETERMINATION OF SOBOL SENSITIVITY INDICES FOR CORRELATED INPUTS WITH SHARK-X
Hursin Mathieu, Siefman Daniel, Perret Gregory, Rochman D, Vasiliev Alexander, Ferroukhi H (2018), DETERMINATION OF SOBOL SENSITIVITY INDICES FOR CORRELATED INPUTS WITH SHARK-X, in PHYSOR 2018: Reactors Physics paving the way towards more efficient systems, Cancun, MexicoResearchGate, Cancun, Mexico.
Analysis of reactivity worths of burnt PWR fuel samples measured in LWR-PROTEUS Phase II using a CASMO-5 reflected-assembly model
Grimm Peter, Hursin Mathieu, Perret Gregory, Siefman Daniel, Ferroukhi Hakim (2017), Analysis of reactivity worths of burnt PWR fuel samples measured in LWR-PROTEUS Phase II using a CASMO-5 reflected-assembly model, in Progress in Nuclear Energy, 101, 280-287.
Case Study of Data Assimilation Methods with the LWR-Proteus Phase II Experimental Campaign
Siefman Daniel, Hursin Mathieu, Grimm Peter, Pautz Andreas (2017), Case Study of Data Assimilation Methods with the LWR-Proteus Phase II Experimental Campaign, in M&C 2017 - International Conference on Mathematics & Computational Methods Applied to Nuclear Scienc, Jeju, KoreaResearchGate, Jeju, Korea.

Collaboration

Group / person Country
Types of collaboration
Paul Scherrer Institut Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Exchange of personnel
Oak Ridge National Laboratories United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE France (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
OECD Nuclear Energy Agency WPEC Subgroup 46 Meeting Talk given at a conference Adjusting GEF Model Parameters with Post Irradiation Examination Experiments 25.06.2019 Paris, France Hursin Mathieu; Siefman Daniel; Pautz Andreas;
OECD/NEA WPEC Subgroup 39 Expert meeting Talk given at a conference Comparing Data Assimilation using Sensitivity Coecients and Stochastic Sampling 21.04.2018 Paris, France Siefman Daniel;
7th InternationalSerpent Group Meeting Individual talk Investigating Effects of Sensitivity Uncertainties 06.11.2017 Gainesville, United States of America Siefman Daniel;


Associated projects

Number Title Start Funding scheme
152612 Small modular Molten Salt Fast Reactor design for closed fuel cycle 01.06.2014 Project funding (Div. I-III)

Abstract

The validation of computer codes for reactor physics design and safety assessment is based primarily on “cold” critical experiments, supplemented by measurements from operating power plants. Extending the validity range of these codes towards new power reactor applications, where little or no operating experience exists, is one of the most challenging tasks in reactor physics today. The central question is: can we reliably project computational biases from our experimental data to an “application” case (e.g. a new power plant design), even if the database contains primarily experiments that are not necessarily “similar” to this target application? Moreover, is it possible to quantify the uncertainties of these biases (that are arising from errors/uncertainties both in experiments and in the nuclear data), particularly when it comes to important safety parameters of challenging plant designs?We propose an approach that tackles these questions from several directions, namely a) the improvement of the experimental database with high-fidelity measurements performed at the Swiss research facility PROTEUS ; b) the development of advanced tools for Sensitivity/Uncertainty (S/U) analysis, combined with nuclear data assimilation methods for bias projection, and c) the demonstration of the methodology on a demanding application case, i.e. a Molten Salt Reactor (MSR) start-up fuel study. The work shall be performed by two PhD students and a Postdoctoral researcher at EPFL, in close cooperation with experienced staff members at Paul-Scherrer-Institute (PSI). The experimental data mentioned in step a) were generated in more than 40 years of PROTEUS operation and represent a huge asset that yet awaits its full exploitation. It must be noticed, however, that due to the recent shutdown of PROTEUS the possibility for future critical experiments in Switzerland has essentially ceased to exist, which goes hand in hand with a gradual loss of know-how. This makes the preservation and utilization of the existing PROTEUS data an even more pressing issue. In this project, we will merge these data with those available from other resources (e.g. from IRPhEP, the OECD’s International Reactor Physics Benchmark Experiments Project [ ]) and build a consolidated and unique database, readily accessible for data assimilation tools.In step b), we will take full benefit of the joint EPFL/PSI activities at the Laboratory for Reactor Physics and System Behavior (LRS) and integrate the PhD students into the ongoing development work on the nuclear uncertainty/sensitivity analysis tool SHARKX [ ]. We will extend this software by a module for data assimilation/adjustment, based on a Generalized-Least-Square-Method (GLSM) and integrate sensitivity analysis based on Monte Carlo codes, recently implemented in SERPENT2 and MCNP6. This will lift the current restriction of SHARKX to Light Water Reactors (LWR), and provide an appropriate platform for modeling various PROTEUS configurations, as well as innovative reactor core designs. In step c), the extended S/U-tool suite together with the improved experimental database will serve as a platform for the assessment of biases and uncertainties of an advanced reactor application: the Molten Salt Reactor (MSR). For the MSR, an uncertainty study of the start-up fuel composition in the Thorium-Uranium cycle is foreseen. One of the options, how to launch the Thorium-Uranium cycle, is utilization of the TRansUranic elements (TRUs), in particular Plutonium from spent Light Water Reactor (LWR) fuel. Since the solubility of Plutonium in the foreseen MSR carrier salt is limited, a feasibility of this option may strongly depend on the fuel composition. Since Thorium experimental data are scarce and nuclear cross sections of the key isotope Th-232 are not very well known, bias projection and understanding the major sources of uncertainties are of paramount importance for the MSR fuel cycle start-up; we expect that the unique PROTEUS data measured for Th-232 in Plutonium-fuelled environment will be of high relevance for the reduction of computational biases. The authors of this proposal are well aware of the fact that the thermal hydraulic conditions in the application system have the potential to influence the bias prediction, in particular if local parameters are addressed. However, detailed thermal-hydraulic calculations on the target systems are not within the scope of this proposal: while a “holistic” approach that addresses all sources of bias is clearly most desirable, this would require a significantly larger amount of resources for the application target modeling than is being requested here. However, we propose to perform studies on simplified models (e.g. simplified yet representative geometries of the reactor application under consideration, with varying thermal-hydraulic conditions), and perform parametric studies with SHARKX to assess the impact of temperature and density variations on bias prediction. In addition, another research proposal was launched by the principal investigator’s laboratory at PSI and recently approved by the SNF (application number 200021_152612/1: “Small modular Molten Salt Fast Reactor design for closed fuel cycle”); in this framework, more in-depth studies will be performed on the thermal-hydraulic modeling aspects of Molten Salt Reactors, that will eventually be merged with the efforts proposed in the research plan at hand.
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