[Federal Register Volume 67, Number 67 (Monday, April 8, 2002)]
[Proposed Rules]
[Pages 16654-16656]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 02-8386]


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 Proposed Rules
                                                 Federal Register
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 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
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  Federal Register / Vol. 67, No. 67 / Monday, April 8, 2002 / Proposed 
Rules  

[[Page 16654]]



NUCLEAR REGULATORY COMMISSION

10 CFR Part 50

[Docket No. PRM-50-75]


Nuclear Energy Institute; Receipt of Petition for Rulemaking

AGENCY: Nuclear Regulatory Commission.

ACTION: Petition for rulemakings; Notice of receipt.

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SUMMARY: The Commission requests public comment on a petition for 
rulemaking filed February 6, 2002, by the Nuclear Energy Institute 
(NEI) (PRM-50-75). The petition requests amendment of the NRC's 
Emergency Core Cooling System (ECCS) regulations to allow the use of an 
alternative maximum pipe break size for the largest pipe in the reactor 
coolant system in ECCS evaluation models for Light-Water Nuclear Power 
Reactors. The regulations currently specify the use of a double-ended 
rupture of the largest pipe in the reactor coolant system in ECCS 
models. NEI states that the proposed change is necessary to improve 
consistency within the existing regulations and will provide increased 
plant safety through the use of more realistic technical specifications 
in surveillance testing. The petitioner estimates regulatory 
improvements could be expedited by up to two years.

DATES: Submit comments by June 24, 2002. 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.

ADDRESSES: Mail comments to: Secretary, U.S. Nuclear Regulatory 
Commission, Washington, DC 20555-0001, Attention: Rulemakings and 
Adjudications Staff.
    Deliver comments to: 11555 Rockville Pike, Rockville, Maryland, 
between 7:30 a.m. and 4:15 p.m. on Federal workdays.
    For a copy of the petition, write to Michael T. Lesar, Chief, Rules 
and Directives Branch, Division of Administrative Services, Office of 
Administration, U.S. Nuclear Regulatory Commission, Washington, DC, 
20555-0001.
    You may also provide comments via the NRC's interactive rulemaking 
Web site at http://ruleforum.llnl.gov. This site allows you to upload 
comments as files in any format, if your Web browser supports the 
function. For information about the interactive rulemaking Web site, 
contact Ms. Carol Gallagher, (301) 415-5905 (e-mail:[email protected]).
    Documents related to this petition, including comments received, 
may be examined, and/or copied for a fee, at the NRC's Public Document 
Room, located at One White Flint North, 11555 Rockville Pike (first 
floor), Rockville, Maryland. Publicly available records will be 
accessible electronically from the ADAMS Public Library component on 
the NRC Web site (the Electronic Reading Room), www.nrc.gov. If you do 
not have access to ADAMS or if there are problems in accessing the 
documents located in ADAMS, contact the NRC PDR Reference staff at 1-
800-397-4029, 301-415-4737 or by e-mail to [email protected].

FOR FURTHER INFORMATION CONTACT: Michael T. Lesar, Chief, Rules and 
Directives Branch, Division of Administrative services, Office of 
Administration, U. S. Nuclear Regulatory Commission, Washington, DC 
20555-0001 or e-mail: [email protected].

SUPPLEMENTARY INFORMATION:

The Petitioner

    The petitioner, the Nuclear Energy Institute (NEI), is an umbrella 
organization for the nuclear energy industry. The NEI is responsible 
for coordinating its members' efforts in matters involving generic 
policy issues and the regulatory aspects of generic operational and 
technical issues affecting the nuclear power industry. NEI members 
include all entities in the United States licensed by the NRC to 
construct or operate nuclear power plants, other nuclear industry 
organizations, as well as major architectural and engineering firms and 
nuclear steam supply system vendors.

Background

    The petitioner states that 10 CFR 50.46, Acceptance Criteria for 
Emergency Core Cooling Systems (ECCS) for Light-Water Nuclear Power 
Reactors, Appendix A to 10 CFR part 50, General Design Criteria (GDC) 
for Nuclear Power Plants, and Appendix K to 10 CFR part 50, ECCS 
Evaluation Models, currently require that assumption of a double-ended 
break of the largest pipe in the reactor coolant system be considered 
in the evaluation models for evaluation of the ECCS acceptance criteria 
and be used to determine ECCS performance requirements. NEI reports 
that Appendix K, promulgated in the early 1970s, specified the required 
and acceptable features of ECCS evaluation models. The petitioner 
believes these models were developed with conservative assumptions and 
notes that the models were required to address areas where data was 
lacking or uncertainties were large or unquantifiable.
    NEI further reports that in 1987, the Commission amended 10 CFR 
part 50, GDC 4 of Appendix A, Environmental and dynamic effects design 
bases to exclude the dynamic effects of postulated ruptures in the 
reactor coolant system primary piping and other high energy line piping 
by the use of leak-before-break (LBB) technology. This relaxation of 
methodology was justified, the petitioner claims, because the 
probability of a pipe break in the largest diameter pipe was extremely 
low for the conditions for which the piping was designed. The 
petitioner notes that this amendment also allowed for the removal of 
pipe whip restraints and jet impingement devices.
    According to the petitioner, the Commission acknowledged that the 
1987 GDC 4 amendment introduced an inconsistency into the design basis 
by retaining the large postulated pipe ruptures for containment design, 
emergency core cooling, and environmental qualification, but allowing 
an exclusion for the dynamic effects of large postulated pipe ruptures 
for piping less than or equal to the largest pipe in the reactor 
coolant system. NEI points out that the Commission stated at that time 
its intention to address these inconsistencies through a long-term 
evaluation.
    The petitioner contends that improvements in probabilistic fracture 
mechanics (PFM) have resulted in NRC approval of a more safety-focused

[[Page 16655]]

approach for implementing ASME Section XI In-service Inspection 
requirements, significantly improving worker and public safety. NEI 
proposes these improved methodologies as the basis for eliminating the 
inconsistencies introduced in the 1987 amendment. NEI believes insights 
from these new analyses will provide the basis for further regulatory 
improvements through the expanded use of PFM and LBB concepts to the 
large-break loss-of-coolant pipe-break size definition.
    The petitioner concludes that the proposed changes would focus 
design and operational procedures, resources, and practices on the more 
likely, safety-significant events. NEI argues that the suggested 
amendments would ultimately result in additional improvements in the 
protection of public health and safety and restore consistency to a 
central element of the regulatory system.

Proposed Action

    The petitioner proposes to amend 10 CFR 50.46 and Appendices A and 
K to 10 CFR part 50 to change the acceptance criteria for analysis of 
emergency core cooling systems for light-water nuclear power reactors. 
NEI wishes to add to the explanation and definition of a loss-of-
coolant accident (LOCA) that must be addressed in the evaluation model, 
an option to the current break size, now defined as ``a break 
equivalent in size to the double-ended rupture of the largest pipe in 
the reactor system.'' NEI proposes adding an optional break size that 
is ``up to and including an alternate maximum break size that is 
approved by the Director of the Office of Nuclear Reactor Regulation 
(NRR).'' The petitioner recommends that this option also be included in 
Appendix K detailing the features of ECCS Evaluation models, including 
consideration of the effects of longitudinal splits in the largest 
pipes, with the split area equal to the cross-sectional area of the 
largest pipe, or equal to an alternate maximum break area that is 
approved by the Director of NRR.

Rationale

    NEI offers the following rationale in support of its petition:
     The operating experience gained from 2500 reactor years of 
very high safety performance and increases in technical knowledge;
     The Commission's commitment to risk-informed regulation; 
and
     A range of expected benefits.

Operating Experience and Increased Technical Knowledge

    NEI explains that the petition provides a means for streamlining 
the regulatory process and improving licensee and NRC focus on matters 
that have greater safety significance. The petitioner claims that U.S. 
nuclear power plants have a very high safety performance record and 
that the insights from probabilistic risk assessments (PRAs) from more 
that 2500 reactor years of operating experience and from increased 
technical knowledge, have produced evidence that some systems and 
design bases events that originally were considered highly important to 
safety have significantly less importance than were originally thought, 
and that some systems or events that were not originally considered 
important to safety are now considered important.
    The petitioner states that the large break LOCA is a central 
element in the design and licensing bases for light water reactors, and 
that advances in analytic techniques (PFM , LBB, and PRA) demonstrate 
that a large break LOCA as currently defined is an extremely unlikely 
event, presenting negligible risk to public health and safety. NEI 
contends that the changes requested will provide added impetus and 
direction in the development and approval of the large break LOCA 
implementation applications, with resulting safety and resource 
benefits from risk-informing the large break LOCA criterion in the 
Commission's regulations.
    The petitioner states that substantial design, licensing, 
operational activities and resources are expended in addressing this 
one extremely unlikely event, the instantaneous double-ended break of 
the largest pipe. The petitioner believes that it is appropriate to 
provide an option for a licensee to revise its design and licensing 
bases to better focus on the more probable equipment failures and 
events that have greater safety significance.
    The petitioner asserts that this petition is a natural extension of 
current leak-before-break (LBB) methodologies, approved by the NRC in 
1987; NEI notes that the LBB acceptance criteria have remained very 
limiting, and retain conservative margins on leak rate, flaw size, and 
loads.

Risk-Informed Regulation

    The petitioner cites the 1995 NRC Policy Statement (60 FR 42622; 
August 16, 1995) formalizing the Commission's commitment to a risk-
informed approach to regulation through an expanded use of 
probabilistic risk assessment (PRA) to reduce regulatory conservatisms: 
``The use of PRA technology should be increased in all regulatory 
matters to the extent supported by the state of the art in PRA methods 
and data, and in a manner that complements the NRC's deterministic 
approach and supports the NRC's traditional defense-in-depth 
philosophy.''
    The petitioner also cites NRC Regulatory Guide 1.174, An Approach 
for Using Probabilistic Risk Assessment in Risk-informed Decisions on 
Plant-Specific Changes to the Current Licensing Basis to the extent 
that the guide provides metrics on what constitutes an acceptable 
change. NEI notes that the technical basis for the petition is the 
insights and information provided in the area of LBB, PFM, and licensee 
specific PRAs. NEI expects licensee and generic owners' groups' 
submittals on large break LOCA applications to be based on these 
technical insights and information as well as application-specific 
analyses.
    The petitioner assures that the industry, in concert with this 
petition, will continue to develop the technical work to support the 
use of alternate-maximum LOCA break size for safety analysis of reactor 
designs. The petitioner further states industry will start work on the 
development of specific applications that will be based on the new 
pipe-break sizes to form the basis of industry and regulatory 
implementation guidelines.
    NEI explains that, if approved, this petition will allow operator 
and support personnel to focus on safety-significant matters resulting 
in improved plant reliability, specifically: improved service life, 
since equipment will not be required to meet unnecessarily harsh 
testing conditions, such as rapid cold starts and loading sequences 
reliabilities; reduced wear and tear on safety-significant equipment; 
and improved training effectiveness, as operations and plant support 
staff will be focused on the more probable events and will no longer 
need to focus on compliance with technical specification limits based 
on margins required for large break LOCAs such as ultimate heat sink 
temperatures.

Expected Benefits

    The petitioner lists the following benefits attained through the 
approval and implementation of the petition:

 Increased plant safety from more realistic technical 
specification surveillance testing and related requirements, such as 
diesel generator (DG) start times and ultimate heat sink temperature 
limits,

[[Page 16656]]

 Consistency in analytical assumptions,
 Peaking factor increases,
 Power upratings, and
 Relaxation of post-LOCA sump boron requirements to maintain 
core subcriticality with all rods out, and requirements for the related 
potential for sump dilution that could lead to recriticality.

Scope

    The petitioner points out that the petition retains the LOCA as a 
design basis event, but redefines the maximum break-size that may be 
used in a design basis evaluation. If a licensee adopts the alternate 
break-size, the existing large break LOCA analysis will be retained as 
a historical document, and the plant-specific PRA will continue to 
include LOCAs of all sizes, including a rupture of the large primary 
system piping. Moreover, the petitioner continues, a licensee will 
still retain capability to mitigate the extremely unlikely break of the 
largest pipe in the reactor system, since most of the major equipment 
is also needed to mitigate other design basis events. NEI states that 
the major components of the current ECCS, such as the head pumps (high, 
intermediate, and low) will be retained.
    NEI warns, however, that the system capability and associated 
requirements and acceptance criteria of these components may be 
revised, based on the revised maximum LOCA break size, or other design 
basis accidents, whichever is more limiting. The petitioner states that 
if the NRC grants the proposed petition, licensees wishing to apply to 
use the alternative break-size criteria will amend the applicable 
safety analyses associated with licensee or owners' group applications. 
The amended analyses will be the basis for the application-specific 
LOCA-related safety analysis assumptions, including control rod 
insertion following a LOCA and associated post-LOCA sump boron 
requirements to maintain core subcriticality, containment sump debris 
generation, and the ultimate heat sink heat removal requirements.
    The petitioner explains that plants requesting approval for use of 
an alternate maximum break size model will determine the alternate 
maximum break size by estimating the appropriate initiating event 
frequencies for LOCA events and the contribution to overall risk of 
equivalent break sizes greater than or equal to the alternate maximum 
break size. The petitioner also states that evaluation of the alternate 
maximum break size will include consideration of defense-in-depth, 
safety margins, and performance monitoring. The petitioner states that 
the risk significance of the changes will be assessed, and such changes 
will be subject to the change control provisions of 10 CFR 50.59 and 
may result in a license amendment, if required, in accordance with 10 
CFR 50.90.
    Finally, the petitioner notes that the proposed amendment may 
result in changes to containment analyses, including the calculation of 
peak containment accident pressure, subcompartment pressure transients, 
containment support system requirements, or the environmental 
qualification temperature profile from a LOCA. NEI adds that 
environmental qualification temperature profiles shall continue to 
consider other design basis breaks in addition to the LOCAs. The 
petitioner assures that it is not the intent of this rulemaking 
petition to be the basis for changing containment structural integrity.

Conclusion

    The petitioner asserts the proposed request is consistent with and 
supports the NRC Strategic and Performance Goals, and the Commission's 
policy on PRA and risk-informed, performance-based regulation. NEI 
contends that approval of the petition will improve nuclear safety 
because a major regulation will be updated to reflect industry 
experience and improvements in PRAs and engineering knowledge. The 
petitioner concludes that this petition will result in plant design, 
operations, activities, and associated regulatory oversight that will 
be more focused on events that are more probable and of higher safety 
significance, while reducing unnecessary regulatory burden.

    Dated at Rockville, Maryland, this 2nd day of April, 2002.

    For the Nuclear Regulatory Commission.
Annette Vietti-Cook,
Secretary of the Commission.
[FR Doc. 02-8386 Filed 4-5-02; 8:45 am]
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