[Federal Register Volume 71, Number 22 (Thursday, February 2, 2006)]
[Notices]
[Pages 5695-5697]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-1386]
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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 revision to an existing 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.
Draft Revision 1 of Regulatory Guide 1.76, entitled ``Design-Basis
Tornado and Tornado Missiles for Nuclear Power Plants,'' is temporarily
identified by its task number, DG-1143, which should be mentioned in
all related correspondence. This proposed revision provides licensees
and applicants with new guidance that the NRC staff considers
acceptable for use in selecting the design-basis tornado and design-
basis tornado-generated missiles that a nuclear power plant should be
designed to withstand in each of the three regions within the
contiguous United States to prevent undue risk to the health and safety
of the public.
By contrast, the predecessor to this revision, entitled ``Design-
Basis Tornadoes for Nuclear Power Plants,'' did not include guidance on
the selection of design-basis tornado-generated missiles. Such missiles
were previously addressed in Section 3.5.1.4, ``Missiles Generated by
Natural Phenomena,'' of NUREG-0800, ``Standard Review Plan for the
Review of Safety Analysis Reports for Nuclear Power Plants'' (SRP).
With this draft Revision 1 of Regulatory Guide 1.76, the staff added
related guidance for licensees and applicants because the Standard
Review Plan (SRP) is intended to provide guidance to NRC reviewers,
rather than licensees and applicants.
In particular, General Design Criterion (GDC) 2, ``Design Bases for
Protection Against Natural Phenomena,'' of Appendix A, ``General Design
Criteria for Nuclear Power Plants,'' to Title 10, Part 50, of the Code
of Federal Regulations (10 CFR part 50), requires that structures,
systems, and components that are important to safety must be designed
to withstand the effects of natural phenomena such as tornadoes without
loss of capability to perform their safety functions. GDC 2 also
requires that the design bases for these structures, systems, and
components shall reflect (1) appropriate consideration of the most
severe of the natural phenomena that have been historically reported
for the site and surrounding area, with sufficient margin for the
limited accuracy, quantity, and period of time in which the historical
data have been accumulated, (2) appropriate combinations of the effects
of normal and accident conditions with the effects of the natural
phenomena, and (3) the importance of the safety functions to be
performed.
Additionally, GDC 4, ``Environmental and Dynamic Effects Design
Bases,'' of Appendix A to 10 CFR part 50 requires, in part, that
structures, systems, and components that are important to safety must
be protected against the effects of missiles from events and conditions
outside the plant.
In addition, for stationary power reactor site applications
submitted before January 10, 1997, Paragraph 100.10c(2) of 10 CFR part
100, ``Reactor Site Criteria,'' states that meteorological conditions
at the site and in the surrounding area should be considered in
determining the acceptability of a site for a power reactor.
By contrast, for stationary power reactor site applications
submitted on or after January 10, 1997, Paragraph 100.20c(2) of 10 CFR
part 100 requires that meteorological characteristics of the site that
are necessary for safety analysis or may have an impact upon plant
design (such as maximum probable wind speed) must be considered in
determining the acceptability of a site for a nuclear power plant. In
addition, Paragraph 100.21(d) of 10 CFR part 100
[[Page 5696]]
requires that the physical characteristics of the site, including
meteorology, must be evaluated and site parameters established such
that potential threats from such physical characteristics will pose no
undue risk to the type of facility proposed to be located at the site.
The essence of these requirements is that nuclear power plants must
be designed so that the plants remain in a safe condition in the event
of the most severe tornado that can reasonably be predicted to occur at
a site as a result of severe meteorological conditions. The original
version of Regulatory Guide 1.76, published in April 1974, was based on
WASH-1300, ``Technical Basis for Interim Regional Tornado Criteria,''
which the NRC (then the Atomic Energy Commission) published in May
1974. WASH-1300 chose the design-basis tornado wind speeds so that the
probability of occurrence of a tornado that exceeded the design-basis
was on the order of 10-7 per year per nuclear power plant.
WASH-1300 used 2 years of observed tornado intensity data (1971 and
1972) to derive design-basis tornado characteristics for three regions
within the continental United States.
By contrast, the design-basis tornado wind speeds presented in this
draft regulatory guide are based on Revision 1 to NUREG/CR-4461,
``Tornado Climatology of the Contiguous United States,'' which the NRC
published in April 2005. The tornado database used in the revised
NUREG/CR-4461 includes information recorded for more than 46,800
tornado segments occurring from January 1, 1950, through August 31,
2003. More than 39,600 of those segments had sufficient information on
location, intensity, length, and width to be used in the analysis of
tornado strike probabilities and maximum wind speeds. The methods used
in this analysis are similar to those used in the analysis of the
initial tornado climatology leading to initial publication of NUREG/CR-
4461 in 1986, with the addition of a term to account for finite
dimensions of structures (sometimes called the ``lifeline'' term), as
well as consideration of the variation of wind speeds along and across
the tornado footprint. The basic idea is that, for finite structures, a
tornado striking any point on the structure can cause damage. (The
original NUREG/CR-4461 used a point model, where the nuclear power
plant was assumed to be a point structure. Therefore, including the
finite dimensions of structures increases the tornado strike
probability.)
Draft Regulatory Guide DG-1143 does not address the determination
of the design-basis tornado and tornado missiles for sites located in
Alaska, Hawaii, or Puerto Rico; such determinations will be evaluated
on a case-by-case basis. This guide also does not identify the specific
structures, systems, and components that should be designed to
withstand the effects of the design-basis tornado or should be
protected from tornado-generated missiles and remain functional. In
addition, this guide does not address the missiles attributable to
extreme winds, such as hurricanes, which the NRC staff will consider on
a case-by-case basis when identified.
To accompany Draft Regulatory Guide DG-1143, the NRC is issuing
updates to proposed Revision 3 of Section 2.3.1, ``Regional
Climatology,'' and Section 3.5.1.4, ``Missiles Generated by Tornadoes
and Extreme Winds,'' of the SRP, which the staff previously issued for
public comment in April 1996. These sections of the SRP relate to Draft
Regulatory Guide DG-1143, in that all three documents concern the
compliance of nuclear power plant designs with GDCs 2 and 4 for severe
weather phenomena. However, Draft Regulatory Guide DG-1143 provides
practices and principles for the benefit of licensees and applicants,
while SRP Sections 2.3.1 and 3.5.1.4 provide guidance to NRC reviewers.
The latest updates to SRP Section 2.3.1 (1) modify the scope of the
severe weather phenomena that should be addressed by applicants for
construction permits, operating licenses, early site permits, and
combined licenses; (2) include new data sources that should be used in
reviewing the information provided by the license applicants; and (3)
clarify the review guidance. By contrast, the changes to SRP Section
3.5.1.4 include deleting the specifications for design-basis tornado
missiles, since that information is now provided in Draft Regulatory
Guide DG-1143.
The NRC staff is soliciting comments on Draft Regulatory Guide DG-
1143, as well as SRP Sections 2.3.1 and 3.5.1.4. Please mention the
relevant document identifiers (DG-1143, SRP 2.3.1, and/or SRP 3.5.1.4)
in the subject line of your comments; comments may be accompanied by
relevant information or supporting data. 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://www.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-
1143 and/or SRP Sections 2.3.1 and 3.5.1.4 may be directed to Dr.
Arthur J. Buslik at (301) 415-6184 or by e-mail to [email protected], or Jin-
Sien Guo at (301) 415-1816 or by e-mail to [email protected].
Comments would be most helpful if received by March 27, 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 Draft Regulatory Guide DG-1143 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/. Similarly,
electronic copies of SRP Sections 2.3.1 and 3.5.1.4 are available at
http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0800/#c2
and http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr0800/#c3, respectively. In addition, electronic copies of the three draft
documents are available in the NRC's Agencywide Documents Access and
Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html,
under Accession ML053140225 (DG-1143), ML053570372
(SRP Section 2.3.1), and ML053570376 (SRP Section 3.5.1.4).
Regulatory guides are also 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
[[Page 5697]]
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 January, 2006.
For the U.S. Nuclear Regulatory Commission.
Richard J. Barrett,
Deputy Director, Division of Risk Analysis and Applications, Office of
Nuclear Regulatory Research.
[FR Doc. E6-1386 Filed 2-1-06; 8:45 am]
BILLING CODE 7590-01-P