[Federal Register Volume 65, Number 69 (Monday, April 10, 2000)]
[Notices]
[Pages 19030-19034]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-8740]


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NUCLEAR REGULATORY COMMISSION


Proposed New Appendix to Standard Review Plan (NUREG-0800), 
Chapter 19, ``Use of Probabilistic Risk Assessment in Plant-Specific, 
Risk-Informed Decisionmaking: General Guidance''

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of opportunity for public comment.

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SUMMARY: The Nuclear Regulatory Commission (NRC) has issued for public 
comment a proposed new appendix to Chapter 19 of its Standard Review 
Plan (NUREG-0800). This chapter of the Standard Review Plan (SRP) 
identifies the roles and responsibilities of organizations in the NRC 
that participate in risk-informed reviews of licensees' proposals for 
changes to the licensing basis, identifies the types of information 
that may be used in fulfilling an organization's review 
responsibilities, and provides general guidance on how the information 
from a probabilistic risk assessment (PRA) can be combined with other 
pertinent information in the process of making a regulatory decision.
    The proposed appendix is titled ``Appendix D--Use of Risk 
Information in Review of Non-Risk Informed License Amendment 
Requests.'' The appendix is being developed to provide guidance to the 
NRC staff on the use of risk information in those rare instances where 
license amendment requests appear to meet regulatory requirements but 
raise significant risk concerns due to some special circumstances 
associated with the request. The appendix is based on the guidance 
contained in SECY-99-246, and approved by the Commission for interim 
use (Staff Requirements Memorandum dated January 5, 2000.)

DATES: The comment period expires May 31, 2000. Comments received after 
this date will be considered if it is practical to do so, but the 
Commission is able to assure consideration only for comments received 
on or before this date. The NRC is also planning to hold a public 
meeting in Rockville, Maryland, to discuss the proposed appendix before 
the close of the comment period. The time and location of the meeting 
will be announced at a later date.

ADDRESSES: Written comments may be submitted to David L. Meyer, Chief, 
Rules and Directives Branch, Division of Administrative Services, 
Office of Administration, Nuclear Regulatory Commission, Washington, DC 
20555-0001. Copies of comments received may be examined at the NRC 
Public Document Room, 2120 L Street NW. (Lower Level), Washington, DC. 
You may also provide comments via the NRC's website at http://www.nrc.gov by using the e-mail link entitled ``NRCREP.''

FOR FURTHER INFORMATION CONTACT: Mr. Robert Palla, Office of Nuclear 
Reactor Regulation, Mail Stop O10H4, Washington, DC, 20555-0001; 
telephone (301) 415-1095; e-mail: [email protected].

SUPPLEMENTARY INFORMATION: The guidance in the new appendix will be 
used by the NRC staff in its reviews of license amendment requests. The 
appendix is based on proposed guidance documented in SECY-99-246, 
``Proposed Guidelines for Applying Risk-Informed Decisionmaking in 
License Amendment Reviews.'' The Commission approved the use of this

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guidance on an interim basis, and directed the staff to finalize the 
guidance and modify relevant guidance documents ensuring that 
stakeholders are engaged in this process (Staff Requirements Memorandum 
dated January 5, 2000.) The purpose of this notice is to inform the 
public of the proposed new appendix, and the opportunity to comment on 
the guidance. A final version will be issued upon resolution of public 
comments and review by the Director, Office of Nuclear Reactor 
Regulation, the NRC's Committee to Review Generic Requirements (CRGR), 
the Advisory Committee on Reactor Safeguards (ACRS), and the 
Commission. In a planned future revision to Regulatory Guide 1.174, 
``An Approach for Using Probabilistic Risk Assessment in Risk-Informed 
Decisions on Plant-Specific Changes to the Licensing Basis,'' the NRC 
plans to incorporate compatible guidance that conforms to the new SRP 
Appendix D.
    The proposed new appendix to NUREG-0800, Chapter 19 follows:

Appendix D--Use of Risk Information in Review of Non-Risk-Informed 
License Amendment Requests

Areas of Review

    When a license amendment request complies with the regulations 
and other license requirements, there is a presumption by the 
Commission of adequate protection of public health and safety (Maine 
Yankee, ALAB-161, 6 AEC 1003 (1973)). However, circumstances may 
arise in which new information reveals an unforeseen hazard or a 
substantially greater potential for a known hazard to occur, such as 
identification of an issue that substantially increases risk. In 
such situations, the NRC has the statutory authority to require 
licensee action above and beyond existing regulations to maintain 
the level of protection necessary to avoid undue risk to public 
health and safety. Section 182.a of the Atomic Energy Act of 1954, 
as amended, and as implemented by 10 CFR 2.102, gives the NRC the 
authority to require the submittal of information in connection with 
a license amendment request if NRC has reason to question adequate 
protection of public health and safety. The licensee may decline to 
submit such information, but it would risk having the amendment 
request denied if NRC cannot find that the requested amendment 
provides adequate protection of public health and safety.
    Under unusual circumstances which could introduce significant 
and unanticipated risks, the NRC staff reviewers would assume the 
burden of demonstrating that the presumption of adequate protection 
is not supported by the bases for the existing staff positions 
despite the fact that currently specified regulatory requirements 
are met. Instances in which the reviewers would question licensees 
regarding risk are expected to be rare. The process used for 
identifying those situations in which risk implications are 
appropriate to consider and for deciding if undue risk exists is 
depicted in Figure 1. This process can be used in the review of both 
licensee-initiated risk-informed license amendment requests, as well 
as license amendment requests in which the licensee chooses to not 
submit risk information (i.e., non-risk informed requests.)
    License amendment requests will be screened for potential risk 
implications as part of the license amendment review process. 
Office-level license amendment review procedures provide guidance on 
which license amendment requests should be examined at the level of 
the integrated risk model due to the potential for significant 
impacts on plant risk \1\. In accordance with the guidance, the risk 
implications of a non-risk-informed submittal would be discussed 
with a risk analyst if the submittal:
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    \1\ Following approval of the subject SRP changes, the staff 
will update the license amendment review procedures to include 
supplemental information on ``special circumstances'' and other 
conforming changes.
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     Significantly changes the allowed outage time (e.g., 
outside the range previously approved at similar plants), 
probability of initiating event, probability of successful 
mitigative action, functional recovery time, or operator action 
requirement;
     Significantly changes functional requirements or 
redundancy;
     Significantly changes operations that affect the 
likelihood of undiscovered failures;
     Significantly affects the basis for successful safety 
function; or
     Could create ``special circumstances'' under which 
compliance with existing regulations may not produce the intended or 
expected level of safety, and plant operation may pose an undue risk 
to public health and safety.
    Non-risk-informed license amendment requests judged to have the 
potential to significantly impact risk would be referred for a more 
detailed risk evaluation as part of the license amendment review.

Review Guidance and Procedures

    For license amendment requests referred for a risk review, the 
reviewers should assess the requested changes, and the need for and 
effectiveness of any compensatory measures that might be warranted 
because of risk considerations, by evaluating the changes relative 
to the safety principles and integrated decisionmaking process 
defined in Regulatory Guide (RG) 1.174. The risk acceptance 
guidelines (Sections 2.2.4 and 2.2.5 of RG 1.174) describe 
acceptable levels of risk increase as a function of total core 
damage frequency (CDF) and large early release frequency (LERF) and 
the manner in which the acceptance guidelines should be applied in 
the review and decisionmaking process. Reviewers should note that 
the guidelines serve as a point of reference for gauging risk impact 
but are not legally binding requirements.
    For non-risk informed license amendment requests, the 
preliminary assessment would be qualitative with a decision based on 
engineering judgment since quantitative risk information would not 
generally be presented in submittals that are not risk informed. If 
``special circumstances'' are believed to exist, the reviewers will 
explore in more detail the underlying engineering issues 
contributing to the risk concern, and the potential risk 
significance of the license amendment request.
    ``Special circumstances'' represent conditions or situations 
that would raise questions about whether there is adequate 
protection, and that could rebut the normal presumption of adequate 
protection from compliance with existing requirements. In such 
situations, undue risk may exist even when all regulatory 
requirements are satisfied. In general, these situations would not 
have been identified or specifically addressed in the development of 
the current set of regulations, and would be important enough to 
warrant the promulgation of a new regulation (e.g., a risk-informed 
regulation) if such situations were encountered on a widespread 
basis. ``Special circumstances'' may include but not be limited to 
license amendment requests which, if approved, could:
     Substantially increase the likelihood or consequences 
of accidents that are risk-significant but beyond the design and 
licensing basis of the plant, for example: Proposed changes to steam 
generator (SG) allowable leak rates that meet Part 100 limits based 
on the design basis source term, but result in a large early release 
given a severe accident source term; or use of new materials for SG 
repairs that provide acceptable performance under normal and design 
basis accident conditions, but a reduced capability to maintain SG 
tube integrity in high temperature severe accident scenarios.
     Degrade multiple levels of defense, or cornerstones in 
the reactor oversight process, through plant operations or 
situations not explicitly considered in the development of the 
regulations, e.g., advanced applications of digital instrumentation 
and controls without due consideration of defense-in-depth.
     Significantly reduce the availability/reliability of 
SSCs that are risk-significant but not required by regulations, 
e.g., turbine driven AFW pumps provided in response to NUREG-0737, 
II.E.1.1, or hardened vents in Mark I containments that protect 
against containment over-pressure failures in accidents beyond the 
design basis.
     Involve changes for which the synergistic or cumulative 
effects could significantly impact risk, e.g., large power uprate 
requests.
    If upon further consideration it is believed that approval of 
the request would compromise the safety principles described in RG 
1.174 and substantially increase risk relative to the risk 
acceptance guidelines contained in the RG, the reviewers should 
inform NRC management of the risk concerns, and the need to further 
evaluate the risk associated with the request. The general criteria 
that should be met are that: (1) The reviewer has knowledge that 
indicates that the risk impact associated with the requested change 
is not reflected by the licensing basis analysis, and (2) the 
reviewer has reason to believe that the magnitude of the risk 
increase may be sufficient to warrant denial of the request or to 
warrant attaching

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conditions to its approval of the request, if the request were 
evaluated in the context of the existing guidance for approval of 
risk-informed applications.
    In such instances, the reviewers with management concurrence 
should ask the licensee to address the safety principles and the 
numerical guidelines for acceptable risk increases contained in RG 
1.174 in their submittal. The reviewers may alternatively ask the 
licensee to submit the information needed for the NRC staff to make 
an independent risk assessment. If a licensee does not choose to 
address risk, the reviewers should not issue the requested amendment 
until they have assessed the risk implications sufficiently to 
determine that there is reasonable assurance that the public health 
and safety will be adequately protected if the amendment request is 
approved. A licensee's decision not to submit requested information 
could impede the staff's review and could also prevent the reviewers 
from reaching a finding that there is reasonable assurance of 
adequate protection. A licensee's failure to submit requested 
information could also be a basis for rejection pursuant to 10 CFR 
2.108.

Evaluation Findings

    The numerical guidance for CDF and LERF provided in RG 1.174 is 
intended to provide a basis for finding that there is reasonable 
assurance of adequate protection. Therefore, situations that exceed 
these values or violate the other principles would constitute a 
trigger point at which questions are raised as to whether the 
proposed change provides reasonable assurance of adequate 
protection. A more in-depth assessment of the special circumstances, 
the safety principles, and the issues identified for management 
attention in Section 2.2.6 of RG 1.174 should then be made in order 
to reach a conclusion regarding the level of safety associated with 
the requested change.
    In making this assessment, the reviewers should be mindful to 
clearly differentiate the concept of adequate protection from the 
numerical risk acceptance guidelines. The guidelines in themselves 
do not constitute a definition of adequate protection, but provide 
an appropriate set of criteria to be used in the process for 
evaluating adequate protection.
    It is not the NRC's policy or within the NRC's technical 
capabilities to allow risk to increase to a point where protection 
is almost, but not quite, inadequate. As discussed in RG 1.174, the 
uncertainty in the analyses must be considered in any finding that 
adequate protection is achieved. The final acceptability of the 
proposed change should be based on a consideration of current 
regulatory requirements, as well as on adherence to the safety 
principles, and not solely on the basis of a comparison of 
quantitative PRA results with numerical acceptance guidelines. The 
authority provided by the Atomic Energy Act and current regulations 
requires rejection of a license amendment request if the NRC is 
unable to find that adequate protection is provided.
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    Dated at Rockville, Maryland, this 3rd day of April 2000.

    For the Nuclear Regulatory Commission.
Timothy E. Collins,
Deputy Director, Division of Systems Safety and Analysis, Office of 
Nuclear Reactor Regulation.

[FR Doc. 00-8740 Filed 4-7-00; 8:45 am]
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