A study on the effect of flaw detection probability assumptions on risk reduction achieved by non-destructive inspection

Otso Cronvall (Corresponding Author), Kaisa Simola, Ilkka Männistö, J. Gunnars, L. Alverlind, P. Dillström, L. Gandossi

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)

Abstract

Leakages and ruptures of piping components lead to reduction or loss of the pressure retaining capability of the system, and thus contribute to the overall risk associated with nuclear power plants. In-service inspection (ISI) aims at verifying that defects are not present in components of the pressure boundary or, if defects are present, ensuring that these are detected before they affect the safe operation of the plant. Reliability estimates of piping are needed e.g., in probabilistic safety assessment (PSA) studies, risk-informed ISI (RI-ISI) applications, and other structural reliability assessments. Probabilistic fracture mechanics models can account for ISI reliability, but a quantitative estimate for the latter is needed. This is normally expressed in terms of probability of detection (POD) curves, which correlate the probability of detecting a flaw with flaw size. A detailed POD curve is often difficult (or practically impossible) to obtain. If sufficient risk reduction can be shown by using simplified (but reasonably conservative) POD estimates, more complex PODs are not needed. This paper summarises the results of a study on the effect of piping inspection reliability assumptions on failure probability using structural reliability models. The main interest was to investigate whether it is justifiable to use a simplified POD curve. Further, the study compared various structural reliability calculation approaches for a set of analysis cases. The results indicate that the use of a simplified POD could be justifiable in RI-ISI applications.
Original languageEnglish
Pages (from-to)90-96
Number of pages7
JournalReliability Engineering and System Safety
Volume105
DOIs
Publication statusPublished - 2012
MoE publication typeA1 Journal article-refereed
EventEuropean Safety and Reliability Conference, ESREL 2010 - Rhodes, Greece
Duration: 5 Sep 20109 Sep 2010

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Inspection
Defects
Fracture mechanics
Risk assessment
Nuclear power plants

Keywords

  • Inspection reliability
  • probabilistic fracture mechanics (PFM)
  • probability of detection curves (POD)
  • risk-informed in-service inspection

Cite this

Cronvall, Otso ; Simola, Kaisa ; Männistö, Ilkka ; Gunnars, J. ; Alverlind, L. ; Dillström, P. ; Gandossi, L. / A study on the effect of flaw detection probability assumptions on risk reduction achieved by non-destructive inspection. In: Reliability Engineering and System Safety. 2012 ; Vol. 105. pp. 90-96.
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A study on the effect of flaw detection probability assumptions on risk reduction achieved by non-destructive inspection. / Cronvall, Otso (Corresponding Author); Simola, Kaisa; Männistö, Ilkka; Gunnars, J.; Alverlind, L.; Dillström, P.; Gandossi, L.

In: Reliability Engineering and System Safety, Vol. 105, 2012, p. 90-96.

Research output: Contribution to journalArticleScientificpeer-review

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AU - Cronvall, Otso

AU - Simola, Kaisa

AU - Männistö, Ilkka

AU - Gunnars, J.

AU - Alverlind, L.

AU - Dillström, P.

AU - Gandossi, L.

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AB - Leakages and ruptures of piping components lead to reduction or loss of the pressure retaining capability of the system, and thus contribute to the overall risk associated with nuclear power plants. In-service inspection (ISI) aims at verifying that defects are not present in components of the pressure boundary or, if defects are present, ensuring that these are detected before they affect the safe operation of the plant. Reliability estimates of piping are needed e.g., in probabilistic safety assessment (PSA) studies, risk-informed ISI (RI-ISI) applications, and other structural reliability assessments. Probabilistic fracture mechanics models can account for ISI reliability, but a quantitative estimate for the latter is needed. This is normally expressed in terms of probability of detection (POD) curves, which correlate the probability of detecting a flaw with flaw size. A detailed POD curve is often difficult (or practically impossible) to obtain. If sufficient risk reduction can be shown by using simplified (but reasonably conservative) POD estimates, more complex PODs are not needed. This paper summarises the results of a study on the effect of piping inspection reliability assumptions on failure probability using structural reliability models. The main interest was to investigate whether it is justifiable to use a simplified POD curve. Further, the study compared various structural reliability calculation approaches for a set of analysis cases. The results indicate that the use of a simplified POD could be justifiable in RI-ISI applications.

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