[Federal Register Volume 75, Number 174 (Thursday, September 9, 2010)]
[Notices]
[Pages 54918-54920]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-22490]
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NUCLEAR REGULATORY COMMISSION
[NRC-2010-0288]
Draft Regulatory Guide, DG-1247, ``Design-Basis Hurricane and
Hurricane Missiles for Nuclear Power Plants'' and Supporting Technical
Basis Documents NUREG/CR 7004 and 7005
DG-1247 is a proposed new regulatory guide. Issuance and
Availability; Correction and Comment Period Extension:
AGENCY: Nuclear Regulatory Commission.
ACTION: Notice of issuance; correction and comment period extension.
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SUMMARY: On August 31, 2010 (75 FR 53352), the U.S. Nuclear Regulatory
Commission (NRC) published a notice of issuance and availability of
Draft Regulatory Guide (DG)--1247, ``Design-Basis Hurricane and
Hurricane Missiles for Nuclear Power Plants.'' This Federal Register
Notice did not provide all the information regarding the supporting
technical basis documents NUREG/CR 7004 and 7005. Due to this
correction the comment period has been extended to November 5, 2010.
FOR FURTHER INFORMATION CONTACT: Robert G. Carpenter, U.S. Nuclear
Regulatory Commission, Washington, DC 20555-0001, telephone (301) 251-
7483, or e-mail [email protected].
SUPPLEMENTARY INFORMATION:
I. Introduction
The U.S. Nuclear Regulatory Commission (NRC) is issuing for public
comment a draft guide in the agency's ``Regulatory Guide'' series and
the supporting technical basis documents, NUREG/CR 7004 and 7005. This
series was 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 (DG), entitled, ``Design-Basis Hurricane
and Hurricane Missiles for Nuclear Power Plants,'' is temporarily
identified by its task number, DG-1247, which should be mentioned in
all related correspondence. DG-1247 is a proposed new regulatory guide.
This guide describes a method 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, ``Early Site Permits; Standard Design Certifications; and Combined
Licenses for Nuclear Power Plants'' (Ref. 9); and combined licenses
under 10 CFR Part 52 that do not reference a standard design.
Specifically, this regulatory guide provides new guidance that the
staff of the NRC considers acceptable for use in selecting the design-
basis hurricane windspeeds and hurricane-generated missiles that a new
nuclear power plant should be designed to withstand to prevent undue
risk to the health and safety of the public. This guidance applies to
the contiguous United States but does not address the determination of
the design-basis hurricane and hurricane missiles for sites located
along the Pacific coast or in Alaska, Hawaii, or Puerto Rico; the NRC
will evaluate such determinations 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
hurricane or should be protected from hurricane-generated missiles and
remain functional. Nor does this guide address other externally
generated hazards, such as aviation crashes, nearby accidental
explosions resulting in blast overpressure levels and explosion-borne
debris and missiles, and turbine missiles. NUREG/CR 7004 is the
technical basis for regulatory guidance on design-basis hurricane-borne
missile speeds and NUREG/CR 7005 is the technical basis for regulatory
guidance on design-basis hurricane wind speeds for new nuclear power
plants.
[[Page 54919]]
II. Further Information
Nuclear power plants must be designed so that they remain in a safe
condition under extreme meteorological events, including those that
could result in the most extreme wind events (tornadoes and hurricanes)
that could reasonably be predicted to occur at the site. Initially, the
NRC solely considered such conditions for tornadoes in Regulatory Guide
(RG) 1.76, ``Design-Basis Tornado for Nuclear Power Plants,'' issued
April 1974. The design-basis tornado windspeeds were chosen so that the
probability that a tornado exceeding the design basis would occur was
on the order of 10-7 per year per nuclear power plant. In
March 2007, the NRC issued Revision 1 to RG 1.76, ``Design-Basis
Tornado and Tornado Missiles for Nuclear Power Plants.'' Revision 1 to
RG 1.76 relied on the Enhanced Fujita Scale which was implemented by
the National Weather Service in February 2007. The Enhanced Fujita
Scale is a revised assessment relating tornado damage to windspeed
which resulted in a decrease in design-basis tornado windspeed criteria
in Revision 1 to RG 1.76.
Since design-basis tornado windspeeds were decreased as a result of
the analysis performed to update RG 1.76, it was no longer clear that
the revised tornado design-basis windspeeds would bound design-basis
hurricane windspeeds in all areas of the United States. This prompted
an investigation into extreme wind gusts during hurricanes and their
relation to design-basis hurricane windspeeds. The NRC commissioned a
report, NUREG/CR 7005, that considers peak-gust windspeeds and
estimates maximum hurricane windspeeds for hurricanes that originate in
the Atlantic and make landfall along the Atlantic and Gulf coasts of
the contiguous United States. The NRC staff has determined that the
design-basis hurricane windspeeds should correspond to the exceedance
frequency of 10-7 per year, calculated as a best estimate.
This is the same exceedance frequency used to establish the design-
basis tornado parameters in Revision 1 to RG 1.76. This exceedance
frequency is also consistent with the Standard Review Plan (NUREG-0800)
Section 2.2.3 (Evaluation of Potential Accidents) criterion for
identifying design-basis events involving hazardous materials or
activities on site and in the vicinity of a proposed site.
To ensure the safety of new nuclear power plants in the event of a
hurricane strike, NRC regulations require that a nuclear power plant
design consider the impact of hurricane-generated missiles, in addition
to the direct action of the hurricane wind. Hurricanes are capable of
generating missiles from objects lying within the path of the hurricane
wind and from debris of nearby damaged structures. To evaluate the
resistance of barriers to penetration and gross failure, the hurricane
missile velocities must also be defined. The NRC commissioned a report,
NUREG/CR 7004, on design-basis hurricane-borne missile velocities. This
report describes the method used to calculate velocities associated
with several types of missiles considered for different hurricane
windspeeds. The selected design-basis hurricane missile spectrum for
nuclear power plants is the same as the design-basis tornado missile
spectrum presented in RG 1.76. This spectrum includes (1) a massive
high-kinetic-energy missile that deforms on impact (an automobile), (2)
a rigid missile that tests penetration resistance (a pipe), and (3) a
small rigid missile of a size sufficient to pass through any opening in
protective barriers (a solid steel sphere).
The hurricane missile analyses presented in NUREG/CR 7004 are based
on missile aerodynamic and initial condition assumptions that are
similar to those used for the analyses of tornado-borne missile
velocities adopted for Revision 1 to RG 1.76. However, the assumed
hurricane wind field differs from the assumed tornado wind field in
that the hurricane wind field does not change spatially during the
missile's flight time but does vary with height above the ground.
Because the size of the hurricane zone with the highest winds is large
relative to the size of the missile trajectory, the hurricane missile
is subjected to the highest windspeeds throughout its trajectory. In
contrast, the tornado wind field is smaller, so the tornado missile is
subject to the strongest winds only at the beginning of its flight.
This results in the same missile having a higher maximum velocity in a
hurricane wind field than in a tornado wind field with the same maximum
(3-second gust) windspeed. For example, the massive high-kinetic-energy
tornado missile (a 1810 kg (4000 lb) automobile) in RG 1.76 is assigned
a velocity of 41 m/s (92 mph) in tornado intensity Region I which has a
design-basis tornado windspeed of 103 m/s (230 mph). The same missile
is assigned a velocity of 68 m/s (152 mph) in a hurricane wind field
with the same design-basis windspeed of 103 m/s (230 mph). The 1810 kg
automobile missile will have a kinetic energy of 1.5x10 \6\ joules in
the tornado wind field versus 4.2x10 \6\ joules in the hurricane wind
field.
The NRC staff would like to point out that the missile speed
analyses for both the tornado and hurricane massive high-kinetic-energy
missile (the 1810 kg automobile) assume the missile starts its motion
with zero initial velocity from an elevation of 40 meters above ground.
Forces tending to increase the elevation of the hurricane missile with
respect to the ground level (e.g., updrafts) are assumed to be
negligible. However, rooftop mechanical (e.g., HVAC) equipment that is
kept in place only by gravity connections is a source of heavy
deformable debris when displaced during extreme-wind events. Buildings
not designed for the hurricane winds can also continue to break up
during the buildup of hurricane winds. Failures progress from the
exterior building elements inward to the structural members (e.g.,
trusses, masonry units, beams, and columns). According to Section 7.1.1
(Debris Potential at Safe Room Sites) of the Second Edition (August
2008) of FEMA 361 (Design and Construction Guidance for Community Safe
Rooms), the literature on hurricanes as well as tornadoes contains
numerous examples of large structural members that have been
transported by winds for significant distances by the wind field when a
portion of exterior sheathing remains connected and provides an
aerodynamic sail area on which the wind can act. An automobile
hurricane missile with an initial elevation of 40 meters above ground
could be considered a surrogate for such equipment and structures which
can be found throughout a nuclear power plant site.
Applications for new power plants will be expected to show that
their applicable structures can independently withstand both the total
design-basis tornado load and the total design-basis hurricane load as
extreme environmental conditions. The staff plans to eventually revise
the corresponding sections the Standard Review Plan to indicate that
the design-basis hurricane windspeeds and hurricane-generated missiles
specified in DG-1247 should be considered as loads to be sustained
during extreme environmental conditions.
The NRC staff is soliciting comments on DG-1247 and NUREG/CR 7004
and 7005. Comments may be accompanied by relevant information or
supporting data and should mention DG-1247 in the subject line.
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).
[[Page 54920]]
DATES: The comment period closes on November 5, 2010.
ADDRESSES: You may submit comments by any one of the following methods.
Please include Docket ID NRC-2010-0288 in the subject line of your
comments. Comments submitted in writing or in electronic form will be
posted on the NRC Web site and on the Federal rulemaking Web site
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.
Federal Rulemaking Web site: Go to http://www.regulations.gov and
search for documents filed under Docket ID NRC-2010-0288. Address
questions about NRC dockets to Carol Gallagher 301-492-3668; e-mail
[email protected].
Mail comments to: Cindy Bladey, Chief, Rules, Announcements and
Directives Branch (RAD), Office of Administration, Mail Stop: TWB-05-
B01M, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or
by fax to RAD at (301) 492-3446.
You can access publicly available documents related to this notice
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.
NRC's Agencywide Documents Access and Management System (ADAMS):
Publicly available documents created or received at the NRC are
available electronically at the NRC's Electronic Reading Room 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 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]. DG-1247 is available electronically under ADAMS
Accession Number ML100480890. In addition, electronic copies of DG-1247
are available through the NRC's public Web site under Draft Regulatory
Guides in the ``Regulatory Guides'' collection of the NRC's Electronic
Reading Room at http://www.nrc.gov/reading-rm/ doc-collections/. The
regulatory analysis may be found in ADAMS under Accession No.
ML102310249.
Regulatory guides are not copyrighted, and NRC approval is not
required to reproduce them.
Dated at Rockville, Maryland, this 1st day of September 2010.
For the Nuclear Regulatory Commission.
Harriet Karagiannis,
Acting Chief, Regulatory Guide Development Branch, Division of
Engineering, Office of Nuclear Regulatory Research.
[FR Doc. 2010-22490 Filed 9-8-10; 8:45 am]
BILLING CODE 7590-01-P