Risk-Informed Safety Margin Characterization (RISMC): Integrated Treatment of Aleatory and Epistemic Uncertainty in Safety Analysis Metadata

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  • Main Title Risk-Informed Safety Margin Characterization (RISMC): Integrated Treatment of Aleatory and Epistemic Uncertainty in Safety Analysis


  • Author: Youngblood, R. W.
    Creator Type: Personal


  • Sponsor: United States. Office of the Assistant Secretary for Nuclear Energy.
    Contributor Type: Organization
    Contributor Info: DOE - NE


  • Name: Idaho National Laboratory
    Place of Publication: Idaho
    Additional Info: INL


  • Creation: 2010-10-01


  • English


  • Content Description: The concept of “margin” has a long history in nuclear licensing and in the codification of good engineering practices. However, some traditional applications of “margin” have been carried out for surrogate scenarios (such as design basis scenarios), without regard to the actual frequencies of those scenarios, and have been carried out with in a systematically conservative fashion. This means that the effectiveness of the application of the margin concept is determined in part by the original choice of surrogates, and is limited in any case by the degree of conservatism imposed on the evaluation. In the RISMC project, which is part of the Department of Energy’s “Light Water Reactor Sustainability Program” (LWRSP), we are developing a risk-informed characterization of safety margin. Beginning with the traditional discussion of “margin” in terms of a “load” (a physical challenge to system or component function) and a “capacity” (the capability of that system or component to accommodate the challenge), we are developing the capability to characterize probabilistic load and capacity spectra, reflecting both aleatory and epistemic uncertainty in system response. For example, the probabilistic load spectrum will reflect the frequency of challenges of a particular severity. Such a characterization is required if decision-making is to be informed optimally. However, in order to enable the quantification of probabilistic load spectra, existing analysis capability needs to be extended. Accordingly, the INL is working on a next-generation safety analysis capability whose design will allow for much more efficient parameter uncertainty analysis, and will enable a much better integration of reliability-related and phenomenology-related aspects of margin.


  • Keyword: Decision Making
  • Keyword: Spectra
  • Keyword: Capacity
  • Keyword: Safety Margins
  • Keyword: Thermal Hydraulics
  • Keyword: Water Risk-Informed
  • Keyword: Safety Analysis
  • Keyword: Safety Margin
  • STI Subject Categories: 22 General Studies Of Nuclear Reactors
  • Keyword: Design
  • Keyword: Licensing
  • Keyword: Risk-Informed
  • Keyword: Evaluation
  • Keyword: Safety


  • Conference: The 8th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation, and Safety (NUTHOS-8,Shanghai, China,10/10/2010,10/14/2010


  • Name: Office of Scientific & Technical Information Technical Reports
    Code: OSTI


  • Name: UNT Libraries Government Documents Department
    Code: UNTGD

Resource Type

  • Article


  • Text


  • Report No.: INL/CON-10-17638
  • Grant Number: DE-AC07-05ID14517
  • Office of Scientific & Technical Information Report Number: 993184
  • Archival Resource Key: ark:/67531/metadc1014017