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Uncertainty Analysis of the Reaction Rates in Ringhals.

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Title: Uncertainty Analysis of the Reaction Rates in Ringhals.
Authors: Persson, Jacob1 (AUTHOR) jacob.persson@vattenfall.com
Source: Nuclear Science & Engineering. 2026 Suppl 1, Vol. 200, pS538-S545. 8p.
Subject Terms: *Pressurized water reactors, *Gaussian mixture models, *Statistical models, *Nuclear power plants, *Sensitivity analysis, *Data transformations (Statistics), *Probability density function, *Nuclear reactors
Abstract: The reaction rates in the Swedish pressurized water reactors Ringhals 3 and Ringhals 4 are measured with in-core detectors and calculated with a deterministic nodal code. The corresponding residuals (measured values minus calculated values) are used to determine the uncertainty of the maximum rod power, constituting a limiting parameter in-core design and a fundamental parameter in safety analysis. This study aims to make a statistical investigation of the axially averaged reaction rates. Multiple models of the distribution of the residuals are constructed under the assumption of normality by applying phenomenological deduction, kernel density estimations, Box-Cox transformations, multivariate normal distribution, and the Gaussian mixture model. The models are normality, two-sample, and autocorrelation tested with the Shapiro-Wilk test, Kolmogorov-Smirnov test, and Durbin-Watson test, respectively. Ultimately, predictions of the models are compared to new data. The models constructed with kernel density estimations and Box-Cox transformations appear to accurately describe statistical characteristics of the sampled data. However, the data are found to be clustered, position correlated, and autocorrelated, making these models invalid. The multivariate normal distribution applied to the position-specific residuals is, on the other hand, able to predict new data. Results from the Gaussian mixture model support the cycle-based clustering used in the multivariate normal distribution. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
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  Availability: 0
Header DbId: enr
DbLabel: Energy & Power Source
An: 192155918
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
PreciseRelevancyScore: 0
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  Data: The reaction rates in the Swedish pressurized water reactors Ringhals 3 and Ringhals 4 are measured with in-core detectors and calculated with a deterministic nodal code. The corresponding residuals (measured values minus calculated values) are used to determine the uncertainty of the maximum rod power, constituting a limiting parameter in-core design and a fundamental parameter in safety analysis. This study aims to make a statistical investigation of the axially averaged reaction rates. Multiple models of the distribution of the residuals are constructed under the assumption of normality by applying phenomenological deduction, kernel density estimations, Box-Cox transformations, multivariate normal distribution, and the Gaussian mixture model. The models are normality, two-sample, and autocorrelation tested with the Shapiro-Wilk test, Kolmogorov-Smirnov test, and Durbin-Watson test, respectively. Ultimately, predictions of the models are compared to new data. The models constructed with kernel density estimations and Box-Cox transformations appear to accurately describe statistical characteristics of the sampled data. However, the data are found to be clustered, position correlated, and autocorrelated, making these models invalid. The multivariate normal distribution applied to the position-specific residuals is, on the other hand, able to predict new data. Results from the Gaussian mixture model support the cycle-based clustering used in the multivariate normal distribution. [ABSTRACT FROM AUTHOR]
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=enr&AN=192155918
RecordInfo BibRecord:
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    Identifiers:
      – Type: doi
        Value: 10.1080/00295639.2025.2464452
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      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 8
        StartPage: S538
    Subjects:
      – SubjectFull: Pressurized water reactors
        Type: general
      – SubjectFull: Gaussian mixture models
        Type: general
      – SubjectFull: Statistical models
        Type: general
      – SubjectFull: Nuclear power plants
        Type: general
      – SubjectFull: Sensitivity analysis
        Type: general
      – SubjectFull: Data transformations (Statistics)
        Type: general
      – SubjectFull: Probability density function
        Type: general
      – SubjectFull: Nuclear reactors
        Type: general
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      – TitleFull: Uncertainty Analysis of the Reaction Rates in Ringhals.
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              Text: 2026 Suppl 1
              Type: published
              Y: 2026
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              Value: 200
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            – TitleFull: Nuclear Science & Engineering
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