[Federal Register Volume 76, Number 190 (Friday, September 30, 2011)]
[Notices]
[Pages 60939-60941]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-25242]
-----------------------------------------------------------------------
NUCLEAR REGULATORY COMMISSION
[NRC-2011-0229]
Metal Fatigue Analysis Performed by Computer Software
AGENCY: Nuclear Regulatory Commission.
ACTION: Regulatory issue summary; request for comment.
-----------------------------------------------------------------------
SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is proposing to
issue a regulatory issue summary (RIS) to remind its addressees of the
American Society of Mechanical Engineers (ASME) Boiler and Pressure
Vessel Code (ASME Code) requirements in accordance with Title 10 of the
Code of Federal Regulations (10 CFR) 50.55a, ``Codes and Standards,''
and of the quality assurance (QA) requirements for design control in
accordance with Appendix B, ``Quality Assurance Criteria for Nuclear
Power Plants and Fuel Reprocessing Plants,'' to 10 CFR Part 50.
Specifically, this RIS informs addressees of the NRC's findings from
license renewal and new reactor audits on applicants' analyses and
methodologies using the computer software package,
WESTEMSTM, to demonstrate compliance with Section III,
``Rules for Construction of Nuclear Facility Components,'' of the ASME
Code.
DATES: Submit comments by October 31, 2011. Comments received after
this date will be considered if it is practical to do so, but the NRC
is able to assure consideration only for comments received on or before
this date.
ADDRESSES: Please include Docket ID NRC-2011-0229 in the subject line
of your comments. For additional instructions on submitting comments
and instructions on accessing documents related to this action, see
``Submitting Comments and Accessing Information'' in the SUPPLEMENTARY
INFORMATION section of this document. You may submit comments by any
one of the following methods:
Federal Rulemaking Web site: Go to http://www.regulations.gov and search for documents filed under Docket ID NRC-
2011-0229. Address questions about NRC dockets to Carol Gallagher,
telephone: 301-492-3668; e-mail: [email protected].
Mail comments to: Cindy Bladey, Chief, Rules,
Announcements, and Directives Branch (RADB), Office of Administration,
Mail Stop: TWB-05-B01M, U.S. Nuclear Regulatory Commission, Washington,
DC 20555-0001.
Fax comments to: RADB at 301-492-3446.
SUPPLEMENTARY INFORMATION:
Submitting Comments and Accessing Information
Comments submitted in writing or in electronic form will be posted
on the NRC Web site and on the Federal rulemaking Web site, http://www.regulations.gov. Because your comments will not be edited to remove
any identifying or contact information, the NRC cautions you against
including any information in your submission that you do not want to be
publicly disclosed.
The NRC requests that any party soliciting or aggregating comments
received from other persons for submission to the NRC inform those
persons that the NRC will not edit their comments to remove any
identifying or contact information, and therefore, they should not
include any information in their comments that they do not want
publicly disclosed.
You can access publicly available documents related to this
document using the following methods:
NRC's Public Document Room (PDR): The public may examine
and have copied, for a fee, publicly available documents at the NRC's
PDR, Room O1-F21, One White Flint North, 11555 Rockville Pike,
Rockville, Maryland 20852.
NRC's Agencywide Documents Access and Management System
(ADAMS): Publicly available documents created or received at the NRC
are available online in the NRC Library at http://www.nrc.gov/reading-rm/adams.html. From this page, the public can gain entry into ADAMS,
which provides text and image files of the NRC's public documents. If
you do not have access to ADAMS or if there are problems in accessing
the documents located in ADAMS, contact the NRC's PDR reference staff
at 1-800-397-4209, 301-415-4737, or by e-mail to [email protected].
The draft RIS is available electronically under ADAMS Accession Number
ML11252A520.
Federal Rulemaking Web site: Public comments and
supporting materials related to this notice can be found at http://www.regulations.gov by
[[Page 60940]]
searching on Docket ID NRC-2011-0229.
FOR FURTHER INFORMATION CONTACT: On Yee, Office of Nuclear Reactor
Regulation, Division of License Renewal, U.S. Nuclear Regulatory
Commission, Washington, DC 20555-0001, telephone: 301-415-1905, e-mail:
[email protected].
Draft NRC Regulatory Issue Summary 2011-Xxxx; Metal Fatigue Analysis
Performed by Computer Software
Addressees
All holders of, and applicants for, a power reactor operating
license or construction permit under Title 10 of the Code of Federal
Regulations (10 CFR) Part 50, ``Domestic Licensing of Production and
Utilization Facilities,'' except those that have permanently ceased
operations and have certified that fuel has been permanently removed
from the reactor vessel.
All holders of, and applicants for, a power reactor early site
permit, combined license, standard design certification, standard
design approval, or manufacturing license under 10 CFR Part 52,
``Licenses, Certifications, and Approvals for Nuclear Power Plants.''
Intent
The U.S. Nuclear Regulatory Commission (NRC) is issuing this
regulatory issue summary (RIS) to remind addressees of the American
Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code
(ASME Code) requirements in accordance with 10 CFR 50.55a, ``Codes and
Standards,'' and of the quality assurance (QA) requirements for design
control in accordance with Appendix B, ``Quality Assurance Criteria for
Nuclear Power Plants and Fuel Reprocessing Plants,'' to 10 CFR part 50.
Specifically, this RIS informs addressees of the NRC's findings from
license renewal and new reactor audits on applicants' analyses and
methodologies using the computer software package, WESTEMS\TM\, to
demonstrate compliance with Section III, ``Rules for Construction of
Nuclear Facility Components,'' of the ASME Code. The NRC expects
addressees to review this RIS for applicability to their facilities and
to consider actions as appropriate. This RIS requires no action or
written response from addressees.
Background Information
Section 54.21 of 10 CFR, ``Contents of Application--Technical
Information,'' requires applicants for license renewal to perform an
evaluation of time-limited aging analyses relevant to structures,
systems, and components within the scope of license renewal. In most
cases, fatigue analyses of the reactor coolant pressure boundary
components involve time-limited assumptions. In addition, the staff has
provided guidance in NUREG-1800, ``Standard Review Plan for Review of
License Renewal Applications for Nuclear Power Plants,'' Revision 2,
issued December 2010, which recommends that the effects of the reactor
water environment on fatigue life be evaluated for a sample of
components to provide assurance that cracking due to fatigue will not
occur during the period of extended operation. Because the reactor
water environment has a significant impact on the fatigue life of
components, many license renewal applicants have performed supplemental
detailed analyses to demonstrate acceptable fatigue life for these
components.
Regulatory Guide 1.28, ``Quality Assurance Program Criteria (Design
and Construction),'' describes methods that the NRC considers
acceptable for complying with the requirements in Appendix B to 10 CFR
part 50 for establishing and implementing a QA program for the design
and construction of nuclear power plants and fuel reprocessing plants.
The regulations at 10 CFR 50.55a specify the ASME Code
requirements. In particular, 10 CFR 50.55a(c) requires, in part, that
components of the reactor coolant pressure boundary must meet the
requirements for Class 1 components in Section III of the ASME Code,
with limited exceptions specified in 10 CFR 50.55a(c)(2)(4). Some
operating facilities may have performed a supplemental detailed fatigue
analysis of components because of new operating conditions identified
after the plant began operation.
Summary of Issue
The staff has identified concerns about the computer software
package, WESTEMS\TM\, that is used to demonstrate the ability of
nuclear power plant components to withstand the cyclic loads associated
with plant transient operations. This particular computer software
package involves the use of computer code developed to calculate
fatigue usage during plant transient operations such as startups and
shutdowns, as discussed in ASME Code, Section III, Subsection NB,
Subarticles NB-3200, ``Design By Analysis,'' and NB-3600, ``Piping
Design.''
The staff identified these concerns with the computer software
package during the review of the AP1000 design certification
application, and they are described in the staff's safety evaluation
report (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML103430502) and its related audit report (ADAMS
Accession No. ML110250634). One such concern was that the methodology
used by this computer software package to determine the peak stress
intensity range time history in fatigue calculations uses the algebraic
summation of three orthogonal moment vectors. This algebraic summation
methodology is not consistent with ASME Code, Section III, Subsection
NB, Subarticle NB-3650, ``Analysis of Piping Products,'' which states
that resultant moments from different load sets shall not be used in
calculating the moment range (i.e., this algebraic summation
methodology is not an accurate representation of the moment range).
Therefore, the use of this practice could provide results that are not
accurate. The staff also identified a concern in which, under certain
circumstances, the use of this computer software package requires the
user to manually modify peak and valley times/stresses during
intermediate calculations in the software. Although this method of
analyst intervention could provide acceptable results in some cases,
reliance on the user's engineering judgment and ability to modify peak
and valley times/stresses, without control and documentation, could
produce results that are not predictable, repeatable, or conservative.
Because of these concerns, the applicant for the AP1000 design
certification elected to remove the use of this computer software
package from its design certification document, such that it is not
used in the design for the AP1000, as documented in ADAMS Accession No.
ML102770329.
License renewal applicants have attempted to use this computer
software package to demonstrate acceptable fatigue calculations for
plant operation during the period of extended operation. As a result of
the concerns described above, the staff asked a license renewal
applicant that has used this computer software package to perform an
evaluation to demonstrate that the package provides acceptable results
and to assess the impact of these identified concerns on the license
renewal applicant's fatigue calculations (ADAMS Accession No.
ML102810194). The staff conducted an audit to (1) review this
evaluation, (2) address the user's ability to manually modify peak and
valley times/stresses, and (3) address the aforementioned concern
[[Page 60941]]
with the algebraic summation of three orthogonal moment vectors.
At the conclusion of the audit, the staff determined, as described
in its audit report (ADAMS Accession No. ML110871243), that the license
renewal applicant's use of this computer software package demonstrated
(1) that it produced calculations of stresses and cumulative usage
factors that are consistent with the methodology in ASME Code, Section
III, Subsection NB, Subarticle NB-3200, (2) that the analyst's judgment
in manually modifying peak and valley times/stresses in these
calculations was reasonable and can be appropriately justified and
documented, though justification of any user intervention should be
documented, (3) that this applicant did not use this software to
perform fatigue calculations as described in ASME Code, Section III,
Subsection NB, Subarticle NB-3600, and (4) future use of this software
should be accompanied by an acceptable demonstration that it performs
fatigue calculations in accordance with ASME Code, Section III,
Subsection NB, Subarticle NB-3600.
This license renewal applicant performed evaluations on two of its
components: A pressurized water reactor (PWR) pressurizer surge nozzle
and a PWR safety injection boron injection tank nozzle. When
considering the effects of the reactor water environment on fatigue
life, these evaluations indicated a cumulative usage factor that was
less than the ASME Code design limit of 1.0, provided that there was
sufficient and clear records of justification for analyst intervention.
The staff acknowledges that addressees may have used, or will make
use of, other computer software packages in performing ASME Code
fatigue calculations. Thus, the NRC encourages addressees to review the
documents discussed above and to consider actions, as appropriate, to
ensure compliance with the requirements for ASME Code fatigue
calculations and QA programs, as described in 10 CFR 50.55a and
Appendix B to 10 CFR part 50, respectively.
Backfit Discussion
This RIS informs addressees of potential concerns with the use of
computer software packages to perform ASME Code fatigue calculations
and reminds them that they should perform these calculations in
accordance with ASME Code requirements. The regulations at 10 CFR
50.55a specify the ASME Code requirements. Regulatory Guide 1.28
describes methods for establishing and implementing a QA program for
the design and construction of nuclear power plants. For license
renewal, metal fatigue is evaluated as a time-limited aging analysis in
accordance with 10 CFR 54.21(c). Section 4.3, ``Metal Fatigue,'' of
NUREG-1800 provides the associated staff review guidance. This RIS does
not impose a new or different regulatory staff position. It requires no
action or written response and, therefore, is not a backfit under 10
CFR 50.109, ``Backfitting.'' Consequently, the NRC staff did not
perform a backfit analysis.
Federal Register Notification
To be done after the public comment period.
Congressional Review Act
The NRC has determined that this RIS is not a rule as designated by
the Congressional Review Act (5 U.S.C. 801-808) and, therefore, is not
subject to the Act.
Paperwork Reduction Act Statement
This RIS does not contain any information collections and,
therefore, is not subject to the requirements of the Paperwork
Reduction Act of 1995 (44 U.S.C. 3501 et seq.). Existing collection
requirements under 10 CFR Part 54 were approved by the Office of
Management and Budget, control number 3150-0155.
Public Protection Notification
The NRC may not conduct or sponsor, and a person is not required to
respond to, a request for information or an information collection
requirement unless the requesting document displays a currently valid
Office of Management and Budget control number.
Contact
Please direct any questions about this matter to the technical
contact listed below:
Timothy J. McGinty, Director, Division of Policy and Rulemaking, Office
of Nuclear Reactor Regulation.
Laura A. Dudes, Director, Division of Construction Inspection and
Operational Programs, Office of New Reactors.
Technical Contact: On Yee, NRR, 301-415-1905. E-mail:
[email protected].
Note: NRC generic communications may be found on the NRC public
Web site, http://www.nrc.gov, under NRC Library/Document
Collections.
END OF DRAFT REGULATORY ISSUE SUMMARY
Dated at Rockville, Maryland this 22nd day of September 2011.
For the Nuclear Regulatory Commission.
Melanie A. Galloway,
Acting Director, Division of License Renewal, Office of Nuclear Reactor
Regulation.
[FR Doc. 2011-25242 Filed 9-29-11; 8:45 am]
BILLING CODE 7590-01-P