NRC: SECY-07-0042 - Status of the Plan for the Implementation of the Commission's Phased Approach to Probabilistic Risk Assessment Quality
POLICY ISSUE
INFORMATION
SECY-07-0042
March 7, 2007
| For: | The Commissioners |
| From: | Luis A. Reyes, Executive Director for Operations |
| Subject: | STATUS OF THE PLAN FOR THE IMPLEMENTATION OF THE COMMISSION'S PHASED APPROACH TO PROBABILISTIC RISK ASSESSMENT QUALITY |
To inform the Commission of the status of the plan for the implementation of the Commission's phased approach to probabilistic risk assessment (PRA) quality. The paper does not address any new commitments or resource implications.
On December 18, 2003, the Commission issued Staff Requirements Memorandum (SRM)
COMNJD-03-0002, "Stabilizing the PRA Quality Expectations and Requirements" (Agencywide
Document Access and Management System (ADAMS) Accession No. ML033520457). In the
SRM, the Commission approved implementation of a phased approach to achieving an
appropriate level of quality for PRAs associated with U.S. Nuclear Regulatory Commission
(NRC) risk-informed regulatory decisionmaking. An enclosure 
to the SRM described the phased approach and directed the staff to develop an action plan that would define a practical
strategy for its implementation. The staff submitted the plan to the Commission in
SECY-04-0118, "Plan for the Implementation of the Commission's Phased Approach to
Probabilistic Risk Assessment Quality," on July 13, 2004 (ADAMS Accession No.
ML041470505), and received approval in an SRM dated October 6, 2004 (ADAMS Accession
No. ML042800369).
Central to the plan is the development and staff endorsement of national consensus Level 1 (core damage frequency (CDF)) and limited Level 2 (large early release frequency (LERF)) PRA standards and associated industry guidance documents, such as peer review guidance.
The PRA scope addressed in these guidance documents includes internal initiating events (including internal flooding), internal fires, and external initiating events, for full power and for low-power and shutdown operations.
The staff based its schedule for the implementation of the plan on the best information available at the time regarding the projected completion dates for the various national consensus PRA standards and industry guidance documents. An important milestone is the completion of Task 1.7, the development guidance for Phase 3 of the phased approach, by December 31, 2008. The Phase 3 guidance will be an umbrella document that, for each current and anticipated application, identifies the corresponding guidance documents and supporting documents. In particular, it will include guidance related to assessing the quality of the PRAs addressing the scope identified above, i.e., Level 1 and limited Level 2 PRAs for internal initiating events (including internal flooding), internal fires, and external initiating events, for full power and for low-power and shutdown operations, and thus will rely heavily on the published PRA standards and their endorsement in Revision to Regulatory Guide (RG) 1.200, "An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities," which is discussed more fully in the next section.
While, as discussed below, significant progress has been made towards the development of
national consensus PRA standards, it has taken longer than expected. The additional time has
resulted in part because of the complex technical nature of the subject matter, and also
because the preparation of national consensus standards relies to a large extent on volunteers
to serve as members of writing committees, draft documents, and attend meetings. It should
be noted that the NRC sponsored contractors to help develop these standards. Table 1 in the
enclosure provides an updated schedule for the completion of the remaining standards and
related guidance based on a letter from the American Society of Mechanical Engineers (ASME)
and the American Nuclear Society (ANS) dated November 7, 2006 (ADAMS Accession No.
ML070100082), and on a January 18, 2007, discussion with the ANS Risk Informed Standards
Committee Chairman.
The NRC issued RG 1.200 for trial use in February 2004. This version endorsed Addendum A of the ASME Standard for Probabilistic Risk Assessment for Nuclear Power Plant Operations, which addresses internal initiating events at full power for Level 1 and limited Level 2 PRAs, and the NEI Probabilistic Risk Assessment Peer Review Process Guidance. The NRC issued Revision 1 of RG 1.200 (ADAMS Accession No. ML070240001) in January 2007, which endorses the Level 1/LERF Addendum B to the ASME full power internal initiating events PRA standard (ASME RA-Sb-2005, ADDENDA to ASME RA-S-2002 Standard for Probabilistic Risk Assessment for Nuclear Power Plant Applications, December 30, 2005) and Revision 1 of the NEI peer review process (ADAMS Accession Nos. ML063390589 and ML063480076). Revision 1 of RG 1.200 also incorporates revisions resulting from the lessons learned during the pilot applications of RG 1.200 (ADAMS Accession No. ML051590519).
Based on the latest information received from the ASME and ANS standards committees
(ADAMS Accession No. ML070100082), the committees intend to have the PRA quality
standards addressing the remaining risk contributors (i.e., internal fires, external initiating
events, and low-power and shutdown modes of operation) available for staff endorsement by
December 2007. This schedule would support a December 2008 date for staff endorsement (in
Revision 2 of RG 1.200) and the completion of the Phase 3 guidance. However, the plan for
the phased approach to PRA quality envisioned that both the NRC-endorsed guidance and its
use by licensees would be in place by December, 2008. The action plan attached to
SECY-04-118 states that, "For a licensee to achieve Phase 3, the PRA must have been
developed and a peer review performed using those quality standards as a basis." As
discussed below, the implementation of the action plan will likely not be completed by most
licensees until December 2009 in the areas of external events, internal fires and low power and
shutdown modes of operation. This therefore represents a delay in the schedule included in the
July 13, 2004, plan for the phased approach to PRA quality. The implications of this delay are
discussed below. The enclosure summarizes the status of the remaining tasks identified in the
plan.
The phased approach to PRA quality allows licensees up to 1 year following NRC endorsement to implement the NRC-endorsed PRA standards for the various elements of the PRA (i.e., internal initiating events, internal fires, external initiating events, and low-power and shutdown modes of operation). In establishing the implementation period, the NRC recognized that additional licensee time and effort would be necessary after the NRC endorsed a particular PRA standard in order to develop and/or revise the licensee's PRA, perform a peer review, and address any significant findings related to compliance with the requirements of the applicable standard. During the implementation period for a newly endorsed standard, the staff would review a risk-informed license amendment submittal consistent with past practice with respect to the elements of the PRA associated with the license amendment application. Following the 1-year implementation period, the NRC will expect all risk-informed license amendment submittals to be supported by a PRA that implements the appropriate revision of RG 1.200 for all aspects of the PRA that could impact the outcome of the licensing decision.
The NRC issued RG 1.200 for trial use in February 2004. The staff originally intended that the implementation period for applying Revision 1 of RG 1.200 would commence with the completion of the pilot applications of RG 1.200. However, as a result of the lessons learned from a pilot application of the ASME standard to an industry peer review of a licensee PRA in June 2003, and the staff objections documented in RG 1.200, ASME decided to develop Addendum B to the standard. This development took place at the same time as the RG 1.200 pilot reviews. The NRC staff has endorsed Addendum B in Revision 1 of RG 1.200, issued January 2007. Based on these developments, and the experience with updating their PRAs to address PRA quality issues related to the implementation of the Mitigating Systems Performance Index (MSPI) program, many licensees have recognized that they need considerably more resources than originally planned to be able to upgrade their PRAs to meet the guidelines for PRA quality established in RG 1.200. Therefore, the staff will use its current practices to review routine, limited-scope risk-informed licensing applications (such as a request for an extension of the outage time allowed by a technical specification), that are submitted during 2007, for those licensees that have not verified that their PRAs conform to the standard. However, for broad-scope applications, such as the implementation of Title 10, Section 50.69, "Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors," of the Code of Federal Regulations (10 CFR 50.69) or Technical Specification Initiative 4b, "Risk Managed Technical Specifications," submitted during this 1-year phasing-in period, the staff expects that the submittal will include an assessment of the technical adequacy of the PRA using Revision 1 of RG 1.200. This approach is consistent with the industry guidance documents supporting these applications. To support all applications received after December 2007, the staff will expect a licensee to demonstrate the technical adequacy of its PRA using Revision 1 of RG 1.200.
The development and endorsement by the staff of a fire PRA standard is critical to the staff's ability to process industry submittals to implement 10 CFR 50.48(c), National Fire Protection Association (NFPA) Standard 805. The industry anticipates completing the PRA standard for internal fires, and the associated peer review guidance in October 2007, which would support NRC review and endorsement in Revision 2 of RG 1.200 in December 2008. Therefore, allowing for a phasing-in period of 1 year, the staff would apply Revision 2 of RG 1.200 to assess the technical adequacy of the fire PRAs in support of NFPA 805 after December 2009, although earlier licensee implementation of RG 1.200 will expedite staff review. The staff intends to assess the impact of this delay in implementation on the 3-year moratorium period for enforcement actions allowed for those licensees electing to submit NFPA 805 applications.
ANS expects to publish Revision 1 of its external events PRA standard in March 2007 and its low-power and shutdown PRA standard in December 2007. These will also be endorsed in Revision 2 to RG 1.200. Therefore, the staff currently expects that after December 2009 licensees will use Revision 2 of RG 1.200 to address PRA quality for considering the risk from external events or low-power and shutdown modes of operation.
During a September 28, 2006, public meeting, NEI and several industry representatives stated that they were currently focusing their resources predominantly on the development of fire PRAs and on updating the internal events PRAs to bring them into conformance with the RG 1.200 guidance. They further indicated that they considered the development of external initiating event and low-power and shutdown PRAs to be a lower priority. Therefore, the staff anticipates that, although the Phase 3 guidance will be in place by December 31, 2008, many licensees will delay their implementation of the external events and low power and shutdown PRA standard beyond December of 2009. Consequently, these licensees may need to restrict the scope of implementation of risk-informed initiatives to that supported by the internal initiating events and internal fire PRAs.
For new reactor applications, the delay in the Phase 3 implementation date will have only a minimal effect. While the staff expects significant benefits in terms of PRA quality, resource savings, review timeliness, safety focus, and regulatory stability for those areas where NRC-endorsed PRA standards are used, we have long understood that the first round of Combined License applications and the next few Design Certification applications would be received before the original December 2008 completion date for the final elements of Phase 3. The delay in the Phase 3 completion date will therefore not significantly alter the staff's review plans for near-term application. In addition, the anticipated delay should have no affect on PRA use and PRA up-dates during plant operation for new reactors (e.g., for Maintenance Rule implementation, Performance Indicators, the Reactor Oversight, Significance Determination Process, and Risk-Informed License Amendments) since they will occur long after the completion of Phase 3.
Overall, significant progress has been made towards achieving the goal of establishing the framework to support Phase 3 of the Commission's phased approach to PRA quality by December 31, 2008. While it is expected that the Phase 3 guidance will be completed by December 31, 2008, because of delays in the development of the national consensus PRA standards for individual scope items, full implementation by the industry of both Revision 1 and Revision 2 of RG 1.200 is delayed from the dates proposed in the July 13, 2004, plan. In the interim, the staff will continue using its current practices to review those aspects of the base PRA needed to support an application.
The Office of the General Counsel has no legal objections to this paper.
/RA/ Luis A. Reyes |
| Enclosure: | Status of Tasks in the Plan for the Implementation of the Commission's Phased Approach to Probabilistic Risk Assessment Quality |
| CONTACTS: | Gareth W. Parry, NRR/DRA Mary T. Drouin, RES/DRASP |
