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Space–time convergence analysis on BWR stability using TRACE/PARCS
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
Univ Illinois, USA.
2013 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 51, 295-306 p.Article in journal (Refereed) Published
Abstract [en]

Unstable behavior of Boiling Water Reactors (BWRs) is known to occur during operation at certain power and flow conditions. Even though BWR instability is not a severe safety concern, it could cause reactor scram and significantly decrease the economic performance of the plant. This paper aims to (a) quantify TRACE/PARCS space–time discretization error for simulation of BWR stability, (b) establish space (nodalization) and time discretization necessary for space–time converged model and (c) show that the space–time converged model gives more reliable results for both stable and unstable reactor. The space–time converged model is obtained when further refinement of numerical discretization parameters (nodalization and time step) has negligible effect on the solution. The study is significant because performing a space–time convergence analysis is a necessary step of qualification of the TRACE/PARCS model, and use of the space–time converged model increases confidence in the prediction of BWR stability.

Place, publisher, year, edition, pages
2013. Vol. 51, 295-306 p.
Keyword [en]
BWR stability, Coupled TRACE/PARCS analysis, Space–time convergence
National Category
Other Physics Topics
Identifiers
URN: urn:nbn:se:kth:diva-106209DOI: 10.1016/j.anucene.2012.08.018ISI: 000311660700035Scopus ID: 2-s2.0-84868371547OAI: oai:DiVA.org:kth-106209DiVA: diva2:573034
Note

QC 20121129

Available from: 2012-11-29 Created: 2012-11-29 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Sensitivity and Uncertainty Analysis of Boiling Water Reactor Stability Simulations
Open this publication in new window or tab >>Sensitivity and Uncertainty Analysis of Boiling Water Reactor Stability Simulations
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The best estimate codes are used for licensing of Nuclear Power Plants (NPP), but with conservative assumptions. It is claimed that the uncertainties are covered by the conservatism of the calculation. Nowadays, it is possible to estimate certain parameters using non-conservative data with the complement of uncertainty evaluation, and these calculations can also be used for licensing. As NPPs are applying for power up-rates and life extension, new licensing calculations need to be performed. In this case, evaluation of the uncertainties could help improve the performance, while staying below the limit of the safety margins.

Given the problem of unstable behavior of Boiling Water Reactors (BWR), which is known to occur at certain power and flow conditions, it could cause SCRAM and decrease the economic performance of the plant. Performing an uncertainty analysis for BWR stability would give better understating of the phenomenon and it would help to verify and validate (V&V) the codes used to predict the NPP behavior.

This thesis, reports a sensitivity/uncertainty study of numerical, neutronics, and thermal-hydraulics parameters on the prediction of the BWR stability within the framework of OECD Ringhals-1 (R1 stable reactor) and OECD Oskarshamn-2 (O2 unstable reactor) stability benchmarks. The time domain code TRACE/PARCS was used in the analyses. This thesis is divided in three parts: space-time convergence; uncertainty; sensitivity.

A space-time convergence study was done for the numerical parameters (nodalization and time step). This was done by refining nodalization of all components and time step until obtaining space-time converged solution, i.e. further refinement doesn’t change the solution. When the space-time converged solutions were compared to the initial models, much better solution accuracy has been obtained for the stability measures (decay ratio and frequency), for both stable (R1) and unstable (O2) reactors with the space-time converged models.

Further on, important neutronics and thermal-hydraulics parameters were identified and an uncertainty calculation was performed using the Propagation of Input Errors (PIE) methodology. This methodology, also known as the GRS method, has been used because it has been extensively tested and verified by the industry, and because it allows identifying the most influential parameters using the spearman rank correlation method.

Using the uncertainty method’s results, an attempt has been done to identify the most influential parameters affecting the stability. A methodology using the spearman rank correlation coefficient has been implemented, which helps to identify the most influential parameters on the stability (decay ratio and frequency). Additional sensitivity calculations have been performed for better understanding of BWR stability and parameters that affect it.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xiv, 94 p.
Series
Trita-FYS, ISSN 0280-316X ; 2012:84
Keyword
BWR Stability, Sensitivity, Uncertainty
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
SRA - Energy
Identifiers
urn:nbn:se:kth:diva-105866 (URN)978-91-7501-565-1 (ISBN)
Public defence
2012-12-17, FA32, Alba Nova University Center, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
EU, FP7, Seventh Framework ProgrammeStandUp
Note

This work has been preformed thanks to the support of the Swedish Radiation Safety Authority (SSM) and EU project NURISP. QC 20121129

Available from: 2012-11-29 Created: 2012-11-28 Last updated: 2013-04-18Bibliographically approved

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