Document: NRC Regulatory Guide
Document ID: aa450282-f5b0-4dd2-b41a-917a7491deb2
Document Type: regulatory_guide
Title: Preparing Probabilistic Fracture Mechanics (Rev. 0)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2133/ML21334A158.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.245
CFR Part: 
CFR Title: 

Content:
e model approximation and include as additional uncertainty in the estimation of the QoI. RG 1.245 Revision 0, Page 19 2.8. Convergence To assess the convergence of the QoI estimate, the applicant’s documentation should demonstrate the convergence for any discretization used in the analysis (e.g., time step, spatial discretization), as well as statistical convergence based on the sample size and sampling method used in the probabilistic analysis. The primary goal should be to show that the conclusions of the analysis would not change significantly if the applicant used a reasonably, more refined discretization or a larger sample size. To demonstrate and document discretization convergence, the applicant should do the following: • For PFM codes in category QV-1A, the applicant need not document discretization convergence, but analysts should nonetheless verify that discretization convergence is achieved. • For cases where the use of a QV-1 code exercised outside of the validated range, i.e., QV-1B, may directly impact discretization convergence, verification should be documented. • For new or modified codes (categories QV-1C, QV-2, and QV-3), the applicant should document the approach used for assessing discretization convergence and demonstrate and document that a more refined discretization does not significantly affect the outcome of the analysis. To demonstrate and document statistical convergence, the applicant should follow the graded approach described in Table C-7. Figure C-2 illustrates the decision tree for the statistical convergence categories. Figure C-2: Decision tree for statistical convergence categories. RG 1.245 Revision 0, Page 20 Table C-7: Submittal Guidelines for Statistical Convergence Category Description Submittal Guidelines SC-1 a [Acceptance criteria met with at least one order of magnitude margin] AND [no importance sampling AND no surrogate models used] • No sampling uncertainty characterization recommended as long as the