[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