Change search
ReferencesLink to record
Permanent link

Direct link
Predicting actual reactor conditions: Why timedomain simulation is necessary for BWR stability
University of Illinois, Urbana, IL, United States.
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
KTH, School of Engineering Sciences (SCI), Physics, Nuclear Power Safety.
Show others and affiliations
2013 (English)In: International Journal of Nuclear Energy Science and Technology, ISSN 1741-6361, Vol. 7, no 4, 319-342 p.Article in journal (Refereed) Published
Abstract [en]

Despite two decades of development and successful use of coupled thermal-hydraulics/neutron-kinetics (TH/NK) codes for the analysis of design basis accidents, the application of coupled codes to BWR stability transients remains a formidable challenge. While the issues in physical models and numerical methods can be identified, quantified and managed through special developments and separate-effect tests, other aspects (e.g. coupling, modelling assumptions) can only be addressed through benchmarking on full plant stability tests. However, often incomplete information causes uncertainties, whose significance on the modelling and simulation must be evaluated. The objective of this paper is to define validation data needs that allow prediction of the transient behaviour should an unstable condition occur. It is shown that the confidence in exploiting advantageous features of the coupled TH/NK system codes in dealing with core-plant interaction, transient effects and local perturbations can only be evaluated with well-characterised, well-documented plant stability tests and stability events.

Place, publisher, year, edition, pages
2013. Vol. 7, no 4, 319-342 p.
Keyword [en]
BWR stability, Coupled codes, Reactor simulation, RELAP5/PARCS, TH/NK, Time domain, Validation
National Category
Energy Engineering
URN: urn:nbn:se:kth:diva-92646DOI: 10.1504/IJNEST.2013.054369ScopusID: 2-s2.0-84879066810OAI: diva2:514171

QC 20131120. Updated from manuscript to article in journal.

Available from: 2012-04-05 Created: 2012-04-05 Last updated: 2015-04-27Bibliographically 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.
Trita-FYS, ISSN 0280-316X ; 2012:84
BWR Stability, Sensitivity, Uncertainty
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
SRA - Energy
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)
EU, FP7, Seventh Framework ProgrammeStandUp

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

Open Access in DiVA

No full text

Other links

Publisher's full textScopus

Search in DiVA

By author/editor
Kozlowski, TomaszPeltonen, JoannaGajev, IvanPhung, Viet-AnhRoshan, Sean
By organisation
Nuclear Power Safety
Energy Engineering

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 116 hits
ReferencesLink to record
Permanent link

Direct link