[Federal Register Volume 71, Number 159 (Thursday, August 17, 2006)]
[Notices]
[Pages 47548-47549]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-13560]
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NUCLEAR REGULATORY COMMISSION
Draft Regulatory Guide: Issuance, Availability
The U.S. Nuclear Regulatory Commission (NRC) has issued for public
comment a draft of a new guide in the agency's Regulatory Guide Series.
This series has been developed to describe and make available to the
public such information as methods that are acceptable to the NRC staff
for implementing specific parts of the NRC's regulations, techniques
that the staff uses in evaluating specific problems or postulated
accidents, and data that the staff needs in its review of applications
for permits and licenses.
The draft regulatory guide, entitled ``Guidelines for Evaluating
Fatigue Analyses Incorporating the Life Reduction of Metal Components
Due to the Effects of the Light-Water Reactor Environment for New
Reactors,'' is temporarily identified by its task number, DG-1144,
which should be mentioned in all related correspondence. This proposed
regulatory guide describes a method that the NRC staff considers
acceptable for use in complying with the agency's regulations in Title
10, part 50, of the Code of Federal Regulations (10 CFR Part 50),
``Domestic Licensing of Production and Utilization Facilities.''
Specifically, in Appendix A to10 CFR part 50, General Design Criterion
(GDC) 1, ``Quality Standards and Records,'' requires, in part, that
structures, systems, and components that are important to safety must
be designed, fabricated, erected, and tested to quality standards
commensurate with the importance of the safety function performed. In
addition, GDC 30, ``Quality of Reactor Coolant Pressure Boundary,''
requires, in part, that components that are part of the reactor coolant
pressure boundary must be designed, fabricated, erected, and tested to
the highest practical quality standards.
Augmenting those design criteria, 10 CFR 50.55a, ``Codes and
Standards,'' endorses the American Society of Mechanical Engineers
(ASME) Boiler and Pressure Vessel Code for design of safety-related
systems and components. In particular, Section 50.55a(c), ``Reactor
Coolant Pressure Boundary,'' requires, in part, that components of the
reactor coolant pressure boundary must be meet the requirements for
Class 1 components in Section III, ``Rules for Construction of Nuclear
Power Plant Components,'' of the ASME Boiler and Pressure Vessel Code.
Specifically, those Class 1 requirements contain provisions, including
fatigue design curves, for determining a component's suitability for
cyclic service. These fatigue design curves are based on strain-
controlled tests performed on small polished specimens, at room
temperature, in air environments. Thus, these curves do not address the
impact of the reactor coolant system environment.
This draft regulatory guide provides guidance for use in
determining the acceptable fatigue life of ASME pressure boundary
components, with consideration of the light-water reactor (LWR)
environment. In so doing, this guide describes a methodology that the
NRC staff considers acceptable to support reviews of applications that
the agency expects to receive for new nuclear reactor construction
permits or operating licenses under 10 CFR part 50, design
certifications under 10 CFR part 52, and combined licenses under 10 CFR
part 52 that do not reference a standard design. Because of significant
conservatism in quantifying other plant-related variables (such as
cyclic behavior, including stress and loading rates) involved in
cumulative fatigue life calculations, the design of the current fleet
of reactors is satisfactory, and the plants are safe to operate.
The ASME Section III design curves, developed in the late 1960s and
early 1970s, are based on tests conducted in laboratory air
environments at ambient temperatures. The original code developers
applied margins of 2 on strain and 20 on cyclic life to account for
variations in materials, surface finish, data scatter, and
environmental effects (including temperature differences between
specimen test conditions and reactor operating experience). However,
the developers lacked sufficient data to explicitly evaluate and
account for the degradation attributable to exposure to aqueous
coolants. More recent fatigue test data from the United States, Japan,
and elsewhere show that the LWR environment can have a significant
impact on the fatigue life of carbon and low-alloy steels, as well as
austenitic stainless steel.
Two distinct methods can be used to incorporate LWR environmental
effects into the fatigue analysis of ASME Class 1 components. The first
method involves developing new fatigue curves that are applicable to
LWR environments. Given that the fatigue life of ASME Class 1
components in LWR environments is a function of several parameters,
this method would necessitate developing several fatigue curves to
address potential parameter variations. An alternative would be to
develop a single bounding fatigue curve, which may be overly
conservative for most applications. The second method involves using an
environmental correction factor (Fen) to account for LWR
environments by correcting the fatigue usage calculated with the ASME
``air'' curves. This method affords the
[[Page 47549]]
designer greater flexibility to calculate the appropriate impacts for
specific environmental parameters. In addition, applicants have already
used this method in their license renewal applications.
The NRC staff has selected the Fen method, as described
in NUREG/CR-6909, ``Effect of LWR Coolant Environments on the Fatigue
Life of Reactor Materials.'' In particular, Appendix A to that report,
``Incorporating Environmental Effects into Fatigue Evaluations,''
describes a methodology that the staff considers acceptable to
incorporate the effects of reactor coolant environments on fatigue
usage factor evaluations of metal components. In addition, NUREG/CR-
6909 provides a comprehensive review of, and technical basis for, the
methodology proposed in this draft regulatory guide, including analysis
of each parameter affecting the fatigue evaluations.
The NRC staff is soliciting comments on both Draft Regulatory Guide
DG-1144 and NUREG/CR-6909. Comments may be accompanied by relevant
information or supporting data. Please mention DG-1144 and/or NUREG/CR-
6909 in the subject line of your comments. Comments submitted in
writing or in electronic form will be made available to the public in
their entirety through the NRC's Agencywide Documents Access and
Management System (ADAMS). Personal information will not be removed
from your comments. You may submit comments by any of the following
methods.
Mail comments to: Rules and Directives Branch, Office of
Administration, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001.
E-mail comments to: [email protected]. You may also submit comments
via the NRC's rulemaking Web site at http://ruleforum.llnl.gov. Address
questions about our rulemaking Web site to Carol A. Gallagher (301)
415-5905; e-mail [email protected].
Hand-deliver comments to: Rules and Directives Branch, Office of
Administration, U.S. Nuclear Regulatory Commission, 11555 Rockville
Pike, Rockville, Maryland 20852, between 7:30 a.m. and 4:15 p.m. on
Federal workdays.
Fax comments to: Rules and Directives Branch, Office of
Administration, U.S. Nuclear Regulatory Commission at (301) 415-5144.
Requests for technical information about Draft Regulatory Guide DG-
1144 may be directed to Hipolito J. Gonzalez at (301) 415-0068 or by e-
mail to [email protected].
Comments would be most helpful if received by September 25, 2006.
Comments received after that date will be considered if it is practical
to do so, but the NRC is able to ensure consideration only for comments
received on or before this date. Although a time limit is given,
comments and suggestions in connection with items for inclusion in
guides currently being developed or improvements in all published
guides are encouraged at any time.
Electronic copies of the draft regulatory guide are available
through the NRC's public Web site under Draft Regulatory Guides in the
Regulatory Guides document collection of the NRC's Electronic Reading
Room at http://www.nrc.gov/reading-rm/doc-collections/. Electronic
copies are also available in ADAMS (http://www.nrc.gov/reading-rm/adams.html), under Accession ML060970173.
Electronic copies of NUREG/CR-6909 are available through the NRC's
public Web site at http://www.nrc.gov/reading-rm/doc-collections/nuregs/ docs4comment.html. NUREG/CR-6909 is also available through
ADAMS (http://www.nrc.gov/reading-rm/adams.html, under Accession No.
ML061650347.
In addition, regulatory guides and NUREG-series reports are
available for inspection at the NRC's Public Document Room (PDR), which
is located at 11555 Rockville Pike, Rockville, Maryland; the PDR's
mailing address is USNRC PDR, Washington, DC 20555-0001. The PDR can
also be reached by telephone at (301) 415-4737 or (800) 397-4205, by
fax at (301) 415-3548, and by e-mail to [email protected]. Requests for
single copies of draft or final guides (which may be reproduced) or for
placement on an automatic distribution list for single copies of future
draft guides in specific divisions should be made in writing to the
U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001,
Attention: Reproduction and Distribution Services Section; by e-mail to
[email protected]; or by fax to (301) 415-2289. Telephone requests
cannot be accommodated.
Regulatory guides are not copyrighted, and Commission approval is
not required to reproduce them.
(5 U.S.C. 552(a))
Dated at Rockville, Maryland, this 17th day of July, 2006.
For the U.S. Nuclear Regulatory Commission.
Mark A. Cunningham,
Director, Division of Fuel, Engineering & Radiological Research, Office
of Nuclear Regulatory Research.
[FR Doc. E6-13560 Filed 8-16-06; 8:45 am]
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