Confirmation of Wilks’ method applied to TRACE model of boiling water reactor spray cooling experiment

Travis Mui, Tomasz Kozlowski

Research output: Contribution to journalArticle

Abstract

Wilks’ formula has been frequently used to quantify the minimum amount of computational work required to meaningfully assess a model's uncertainty, due to its nonparametric statistical nature that does not require knowledge of the distribution of the qualifying parameters of interest. Additionally, this method allows for any number of input uncertain parameters in the simulation model. This is favorable due to considerable computational expense of typical nuclear safety simulations, providing a quantifiable number of code executions that can statistically verify a desired level of safety. However, there are various existing definitions and uses of Wilks’ theorem in such scenarios, which the present study aims to investigate and quantify for a real thermal-hydraulics experiment used for reactor safety licensing. In this work, the U.S. NRC TRACE thermal-hydraulics code was chosen to simulate the separate-effect spray cooling tests performed by ASEA-ATOM for licensing of BWR SVEA-64 fuel. The computational model was evaluated by performing forward uncertainty quantification (UQ) using Dakota as the analysis tool and code driver on 31 identified sensitive parameters. Using this validated model, the TRACE model was sampled 1000 times with four different input parameter probability distributions to produce four model data sets to assess the applicability of Wilks’ theorem within a realistic nuclear safety analysis scenario. The obtained results compared various Wilks-defined 'sample sizes’ according to one-sided confidence intervals for the 1st, 2nd and 3rd-order statistics, and with the two-sided confidence interval for the 1st-order statistics. The comparison demonstrated that Wilks’ method satisfies the reactor safety modeling requirements at the 95%/95% tolerance/confidence level as determined by the U.S. NRC.

Original languageEnglish (US)
Pages (from-to)53-59
Number of pages7
JournalAnnals of Nuclear Energy
Volume117
DOIs
StatePublished - Jul 2018

Fingerprint

Boiling water reactors
Cooling
Experiments
Hydraulics
Statistics
Probability distributions

Keywords

  • BWR spray cooling
  • TRACE
  • Uncertainty quantification
  • Wilks method

ASJC Scopus subject areas

  • Nuclear Energy and Engineering

Cite this

Confirmation of Wilks’ method applied to TRACE model of boiling water reactor spray cooling experiment. / Mui, Travis; Kozlowski, Tomasz.

In: Annals of Nuclear Energy, Vol. 117, 07.2018, p. 53-59.

Research output: Contribution to journalArticle

@article{5c508d3fb02c4125aa03638072b9fbea,
title = "Confirmation of Wilks’ method applied to TRACE model of boiling water reactor spray cooling experiment",
abstract = "Wilks’ formula has been frequently used to quantify the minimum amount of computational work required to meaningfully assess a model's uncertainty, due to its nonparametric statistical nature that does not require knowledge of the distribution of the qualifying parameters of interest. Additionally, this method allows for any number of input uncertain parameters in the simulation model. This is favorable due to considerable computational expense of typical nuclear safety simulations, providing a quantifiable number of code executions that can statistically verify a desired level of safety. However, there are various existing definitions and uses of Wilks’ theorem in such scenarios, which the present study aims to investigate and quantify for a real thermal-hydraulics experiment used for reactor safety licensing. In this work, the U.S. NRC TRACE thermal-hydraulics code was chosen to simulate the separate-effect spray cooling tests performed by ASEA-ATOM for licensing of BWR SVEA-64 fuel. The computational model was evaluated by performing forward uncertainty quantification (UQ) using Dakota as the analysis tool and code driver on 31 identified sensitive parameters. Using this validated model, the TRACE model was sampled 1000 times with four different input parameter probability distributions to produce four model data sets to assess the applicability of Wilks’ theorem within a realistic nuclear safety analysis scenario. The obtained results compared various Wilks-defined 'sample sizes’ according to one-sided confidence intervals for the 1st, 2nd and 3rd-order statistics, and with the two-sided confidence interval for the 1st-order statistics. The comparison demonstrated that Wilks’ method satisfies the reactor safety modeling requirements at the 95{\%}/95{\%} tolerance/confidence level as determined by the U.S. NRC.",
keywords = "BWR spray cooling, TRACE, Uncertainty quantification, Wilks method",
author = "Travis Mui and Tomasz Kozlowski",
year = "2018",
month = "7",
doi = "10.1016/j.anucene.2018.03.011",
language = "English (US)",
volume = "117",
pages = "53--59",
journal = "Annals of Nuclear Energy",
issn = "0306-4549",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Confirmation of Wilks’ method applied to TRACE model of boiling water reactor spray cooling experiment

AU - Mui, Travis

AU - Kozlowski, Tomasz

PY - 2018/7

Y1 - 2018/7

N2 - Wilks’ formula has been frequently used to quantify the minimum amount of computational work required to meaningfully assess a model's uncertainty, due to its nonparametric statistical nature that does not require knowledge of the distribution of the qualifying parameters of interest. Additionally, this method allows for any number of input uncertain parameters in the simulation model. This is favorable due to considerable computational expense of typical nuclear safety simulations, providing a quantifiable number of code executions that can statistically verify a desired level of safety. However, there are various existing definitions and uses of Wilks’ theorem in such scenarios, which the present study aims to investigate and quantify for a real thermal-hydraulics experiment used for reactor safety licensing. In this work, the U.S. NRC TRACE thermal-hydraulics code was chosen to simulate the separate-effect spray cooling tests performed by ASEA-ATOM for licensing of BWR SVEA-64 fuel. The computational model was evaluated by performing forward uncertainty quantification (UQ) using Dakota as the analysis tool and code driver on 31 identified sensitive parameters. Using this validated model, the TRACE model was sampled 1000 times with four different input parameter probability distributions to produce four model data sets to assess the applicability of Wilks’ theorem within a realistic nuclear safety analysis scenario. The obtained results compared various Wilks-defined 'sample sizes’ according to one-sided confidence intervals for the 1st, 2nd and 3rd-order statistics, and with the two-sided confidence interval for the 1st-order statistics. The comparison demonstrated that Wilks’ method satisfies the reactor safety modeling requirements at the 95%/95% tolerance/confidence level as determined by the U.S. NRC.

AB - Wilks’ formula has been frequently used to quantify the minimum amount of computational work required to meaningfully assess a model's uncertainty, due to its nonparametric statistical nature that does not require knowledge of the distribution of the qualifying parameters of interest. Additionally, this method allows for any number of input uncertain parameters in the simulation model. This is favorable due to considerable computational expense of typical nuclear safety simulations, providing a quantifiable number of code executions that can statistically verify a desired level of safety. However, there are various existing definitions and uses of Wilks’ theorem in such scenarios, which the present study aims to investigate and quantify for a real thermal-hydraulics experiment used for reactor safety licensing. In this work, the U.S. NRC TRACE thermal-hydraulics code was chosen to simulate the separate-effect spray cooling tests performed by ASEA-ATOM for licensing of BWR SVEA-64 fuel. The computational model was evaluated by performing forward uncertainty quantification (UQ) using Dakota as the analysis tool and code driver on 31 identified sensitive parameters. Using this validated model, the TRACE model was sampled 1000 times with four different input parameter probability distributions to produce four model data sets to assess the applicability of Wilks’ theorem within a realistic nuclear safety analysis scenario. The obtained results compared various Wilks-defined 'sample sizes’ according to one-sided confidence intervals for the 1st, 2nd and 3rd-order statistics, and with the two-sided confidence interval for the 1st-order statistics. The comparison demonstrated that Wilks’ method satisfies the reactor safety modeling requirements at the 95%/95% tolerance/confidence level as determined by the U.S. NRC.

KW - BWR spray cooling

KW - TRACE

KW - Uncertainty quantification

KW - Wilks method

UR - http://www.scopus.com/inward/record.url?scp=85043588076&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85043588076&partnerID=8YFLogxK

U2 - 10.1016/j.anucene.2018.03.011

DO - 10.1016/j.anucene.2018.03.011

M3 - Article

AN - SCOPUS:85043588076

VL - 117

SP - 53

EP - 59

JO - Annals of Nuclear Energy

JF - Annals of Nuclear Energy

SN - 0306-4549

ER -