PRA Newly Developed Methods (NDM) Repository Wiki
Overview of PRA-NDM.EPRI.COM Wiki
With the issuance of Regulatory Guide 1.200, Revision 3, the US NRC endorsed the concept of a “newly developed method (NDM)” for use in Probabilistic Risk Assessments (PRAs). RG 1.200, Rev 3 also defined terms and references associated with determining what is an NDM and what options can be used to seek NRC acceptance or consensus that an NDM is acceptable for use in PRA.
Figure 1 is a useful overview of the process for determining whether a change to the PRA is considered an “PRA upgrade” or “PRA maintenance.” This Wiki shares information from pervious evaluations within the industry specifically about the parts of this Figure highlighted in Yellow. These are the questions related to whether a PRA method is considered an NDM, and whether an NDM Peer review has been conducted to determine the technical adequacy of the method for inclusion in risk applications as necessary.
Purpose of PRA-NDM.EPRI.COM Wiki
Because EPRI members and other stakeholders will benefit from a repository of methods that have been considered previously be others in the context of whether they are an NDM, EPRI has created the PRA Newly Developed Methods Wiki at https://pra-ndm.epri.com to be a publicly available reference to meet this need. The repository is organized into broad categories and contains information provided to EPRI by stakeholder (utilities, vendors, NEI, others) about the following:
- Has the method been evaluated previously to determine whether it is an NDM?
- Is the method considered to be an NDM? A summary level justification for this YES/NO determination should be provided.
- If the method is determined to be an NDM, has a peer review of the NDM been conducted? IF YES, then the public summary of the scope and findings of the NDM should be provided.
Scope of PRA-NDM.EPRI.COM Wiki
It should be noted that the information provided in this Wiki is provided to EPRI by various stakeholders for inclusion in the repository. Inclusion of the method in this page does not imply that the method has been vetted or endorsed by EPRI, not that EPRI has evaluated and agreed with the decision that a method is or is not a new method, or with the conclusions of any NDM peer reviews. EPRI’s role is to organize the information provided by others into a publicly accessible repository of for the benefit of members, regulators, and other stakeholders around the world.
- For questions or additional information on the methods contained in the repository, contact the developer of the method directly.
- For questions about the determination that a method is or is not a newly developed method, contact the person listed as the contact person on the summary justification for that determination.
- For questions on the scope or conclusions of a newly developed method peer review, please contact the peer review lead listed in the public summary of the NDM peer review of interest.
The content of the Wiki is not intended to be all-inclusive. It does not intend to capture and document all accepted state-of-practice methods. Instead, the Wiki includes the information provided to EPRI by industry stakeholders about which methods PRA have been reviewed and considered as potential NDMs upon the release of RG 1.200, Rev 3.
EPRI Materials Referenced in PRA-NDM.EPRI.COM Wiki
Any EPRI results (reports, software products, etc.) included in the Wiki are fully documented as EPRI and accessible by EPRI members on www.epri.com. As a global, independent, scientific research organizations, EPRI supports the technical basis of all EPRI research which may be considered a PRA method. However, as a not-for-profit, EPRI does not engage directly in determining steps are required for regulatory acceptance of PRA methods in individual countries around the world. EPRI supports its members in understanding and applying the methods correctly and consistent with their technical bases. Thus, decisions on whether an EPRI method is an NDM are made by the users of the methods. Also, conduct of NDM peer reviews are organized by the users of the methods, though EPRI will support answering technical questions on the method, its development and basis as part of any conducted peer reviews on EPRI methods.
Definitions
Definition of a Newly Developed Method:
- Newly Developed Method A PRA method that has either been developed separately from a state-of practice method or is one that involves a fundamental change to a state-of practice method. An NDM is not a state-of practice or a consensus method.
Supporting Definitions: A number of definitions are needed to support the development of the NDM requirements and review process. Several important definitions used in determining whether something is a “newly developed method” are provided below:.
- PRA Upgrade: A change in the PRA that results in the applicability of one or more supporting requirements that were not previously included within the PRA (e.g., performing qualitative screening for Part 4 of ASME/ANS Level 1/LERF PRA standard when the related high-level requirement was previously not applicable, or adding a new hazard model), an implementation of a PRA method in a different context, or the incorporation of a PRA method not previously used.
- PRA Method: An analytical approach in the PRA used to satisfy a supporting requirement or collection thereof from a national consensus PRA standard. An analytical approach is generally a compilation of the analyses, tools, assumptions, and data used to develop a model.
- Model: A qualitative and/or quantitative representation that is constructed to portray the inherent characteristics and properties of what is being represented (e.g., a system, component or human performance, theory or phenomenon). A model may be in the form, for example, of a structure, schematic or equation. Method(s) are used to construct the model under consideration.
- PRA: An approach that (1) provides a quantitative assessment of the identified risk in terms of scenarios that result in undesired consequences (e.g., core damage or a large early release) and their frequencies and (2) comprises specific technical elements in performing the quantification.
- PRA Maintenance: A change in the PRA that does not meet the definition of PRA upgrade.
- State-of–Practice: Practices that are widely accepted by and implemented throughout the commercial nuclear power industry, have been shown to be technically acceptable in well-documented analyses or engineering assessments that are publicly available, and are accepted by the NRC.
- Consensus Method/Model In the context of risk-informed regulatory decisions, a method or model approach that the NRC has used or accepted for the specific risk-informed application for which it is proposed. A consensus method or model may also have a publicly available, published basis and may have been peer reviewed and widely adopted by an appropriate stakeholder group.
Guidance Documents
- RG 1.200, Rev 3
- NEI Docs
- PWROG Example Document
Disclaimer
- Not intended to be all-inclusive
- Started in 2021
- Things added based on industry information provided to EPRI (NOT EPRI products)
Contacts for questions
NEI