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, 54918-54920 [2010-22490]
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Federal Register / Vol. 75, No. 174 / Thursday, September 9, 2010 / Notices
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Event Scale Report to the International
Atomic Energy Agency (per NRC
Management Directive 5.12), and there
are unique or unusual aspects of the
licensee’s performance that warrant
additional NRC oversight (e.g., a
significant event, which requires an
incident investigation team (IIT) or
augmented inspection team (AIT)); or
(3) Performance Trend—Licensee has
multiple and/or repetitive significant
program issues identified over more
than one inspection, or inspection
period, and the issues are supported by
severity level I, II, or III violation, as
described in the NRC Enforcement
Policy (including equivalent violations
dispositioned by Alternative Dispute
Resolution). And, there are unique or
unusual aspects of the licensee’s
performance that warrant additional
NRC oversight (e.g., oversight panel
formed for order implementation).
Proposed Criteria for Determining
Materials Licensees for the AARM
The NRC is proposing the following
revision to the existing criteria for
determining materials licensees with
significant performance issues: (1)
Strategic Plan—Licensee has an event
that results in the failure to meet a
strategic outcome for safety and security
in the NRC Strategic Plan (NUREG–
1614); (2) Significant Issue or Event—
Licensee has an issue or event that
results in an abnormal occurrence report
to Congress (per NRC Management
Directive 8.1), or a severity level I or II
violation, as described in the NRC
Enforcement Policy (including
equivalent violations dispositioned by
Alternative Dispute Resolution), or a
level 3 or higher International Nuclear
Event Scale Report to the International
Atomic Energy Agency (per NRC
Management Directive 5.12), and there
are unique or unusual aspects of the
licensee’s performance that warrant
additional NRC oversight (e.g., a
significant event, which requires an IIT
or AIT); or (3) Performance Trend—
Licensee has multiple and/or repetitive
significant program issues identified
over more than one inspection, or
inspection period, and the issues are
supported by severity level I, II, or III
violation, as described in the NRC
Enforcement Policy (including
equivalent violations dispositioned by
Alternative Dispute Resolution). And,
there are unique or unusual aspects of
the licensee’s performance that warrant
additional NRC oversight (e.g., oversight
panel formed for order implementation);
or (4) Identified for Discussion at
Previous AARM—Licensee corrective
actions did not address or were
ineffective in correcting the underlying
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issues that were previously discussed at
the AARM.
You can find NRC’s strategic plan
(NUREG–1614) and the referenced
management directives and enforcement
policy on NRC’s public document
collections Web page at https://
www.nrc.gov/reading-rm/doccollections/.
Dated at Rockville, Maryland, this 25th day
of August 2010.
For the Nuclear Regulatory Commission.
Cynthia A. Carpenter,
Deputy Director, Office of Federal and State
Materials and Environmental Management
Programs.
[FR Doc. 2010–22481 Filed 9–8–10; 8:45 am]
BILLING CODE 7590–01–P
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.
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, ‘‘DesignBasis 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
Robert.Carpenter@nrc.gov.
SUMMARY:
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
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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 caseby-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.
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Federal Register / Vol. 75, No. 174 / Thursday, September 9, 2010 / Notices
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, ‘‘DesignBasis Tornado for Nuclear Power
Plants,’’ issued April 1974. The designbasis 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 designbasis 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,
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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 designbasis 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 highkinetic-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 1.5×10 6 joules in the tornado
wind field versus 4.2×10 6 joules in the
hurricane wind field.
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54919
The NRC staff would like to point out
that the missile speed analyses for both
the tornado and hurricane massive highkinetic-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 designbasis 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).
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Federal Register / Vol. 75, No. 174 / Thursday, September 9, 2010 / Notices
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
https://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
Carol.Gallagher@nrc.gov.
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 https://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
pdr.resource@nrc.gov. DG–1247 is
available electronically under ADAMS
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DATES:
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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
https://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
NUCLEAR REGULATORY
COMMISSION
[Docket Nos. 50–275–LR and 50–323–LR;
ASLBP No. 10–890–01–LR–BD01]
In the Matter of Pacific Gas & Electric
Company (Diablo Canyon Nuclear
Power Plant, Units 1 and 2); Notice of
Hearing (Application for License
Renewal)
September 1, 2010.
Atomic Safety and Licensing Board
Before Administrative Judges: Alex S.
Karlin, Chairman, Nicholas G.
Trikouros, Dr. Paul B. Abramson.
This proceeding concerns the
November 23, 2009, application of
Pacific Gas & Electric Company (PG&E)
to renew Operating License Nos. DPR–
80 and DPR–82 for the Diablo Canyon
Nuclear Power Plant, Units 1 and 2,
near San Luis Obispo, California. PG&E
seeks to extend these licenses for an
additional twenty years beyond the
current expiration dates of November 2,
2024 and August 26, 2025.
On January 21, 2010, the Nuclear
Regulatory Commission (NRC)
published a notice of opportunity to
request a hearing concerning the PG&E
license renewal application. 75 FR 3493
(Jan. 21, 2010). On March 22, 2010, the
San Luis Obispo Mothers for Peace
(SLOMFP), a local public interest group,
filed a request for hearing and asserted
five contentions challenging various
aspects of PG&E’s application. On April
8, 2010, this Atomic Safety and
Licensing Board was established to
conduct this adjudication. See 75 FR
20,010 (Apr. 16, 2010). On May 26,
2010, the Board heard oral argument
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from SLOMFP, PG&E, and the NRC Staff
in San Luis Obispo, California, relating
to the admissibility of the proposed
contentions. On August 4, 2010, the
Board issued a memorandum and order
granting SLOMFP’s request for a hearing
and admitting four of its contentions.
LBP–10–15, 72 NRC l (slip op.) (Aug.
4, 2010).
Pursuant to 10 CFR 2.105(e)(2), please
take notice that the Atomic Safety and
Licensing Board will conduct an
evidentiary hearing on SLOMFP’s
challenge to PG&E’s application to
renew its licenses. The matters of fact
and law to be considered at the hearing
are the contentions that have been duly
admitted. As of this time, the four
admitted contentions are as follows:
Contention EC–1: PG&E’s Severe Accident
Mitigation Alternatives (‘‘SAMA’’) analysis
fails to satisfy 40 CFR 1502.22 because it fails
to consider information regarding the
Shoreline fault that is necessary for an
understanding of seismic risks to the Diablo
Canyon nuclear power plant. Further, that
omission is not justified by PG&E because it
has failed to demonstrate that the
information is too costly to obtain. As a result
of the foregoing failures, PG&E’s SAMA
analysis does not satisfy the requirements of
the National Environmental Policy Act
(‘‘NEPA’’) for consideration of alternatives or
NRC implementing regulation 10 CFR
51.53(c)(3)(ii)(L).
Contention EC–2: PG&E’s Environmental
Report is inadequate to satisfy NEPA because
it does not address the airborne
environmental impacts of a spent fuel pool
accident caused by an earthquake adversely
affecting DCNPP.1
Contention EC–4: The Environmental
Report fails to satisfy the National
Environmental Policy Act (NEPA) because it
does not discuss the cost-effectiveness of
measures to mitigate the environmental
impacts of an attack on the Diablo Canyon
reactor during the license renewal term.2
Contention TC–1: The applicant, Pacific
Gas & Electric Company (PG&E), has failed to
satisfy 10 CFR 54.29’s requirement to
demonstrate a reasonable assurance that it
can and will ‘‘manage the effects of aging’’ in
accordance with the current licensing basis.
PG&E has failed to show how it will address
and rectify an ongoing adverse trend with
respect to recognition, understanding, and
management of the Diablo Canyon Nuclear
Power Plant’s design/licensing basis which
undermines PG&E’s ability to demonstrate
that it will adequately manage aging in
accordance with this same licensing basis as
required by 10 CFR 54.29.
1 Although the Board has determined that
Contention EC–2 otherwise meets the admissibility
criteria of 10 CFR 2.309(f)(1), no evidentiary hearing
will be held on this contention unless the
Commission rules that SLOMFP’s request for
waiver of certain key regulations is warranted under
10 CFR 2.335. That waiver request is now pending
before the Commission.
2 Pursuant to 10 CFR 2.323(f)(1) the Board
referred Contention EC–4 to the Commission.
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]]>Agencies
[Federal Register Volume 75, Number 174 (Thursday, September 9, 2010)]
[Notices]
[Pages 54918-54920]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-22490]
-----------------------------------------------------------------------
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.
-----------------------------------------------------------------------
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 Robert.Carpenter@nrc.gov.
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 https://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
Carol.Gallagher@nrc.gov.
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 https://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
pdr.resource@nrc.gov. 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 https://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
