[Federal Register Volume 77, Number 86 (Thursday, May 3, 2012)]
[Notices]
[Pages 26318-26321]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2012-10698]
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NUCLEAR REGULATORY COMMISSION
[Docket Nos. 50-269, 50-270, and 50-287; NRC-2012-0088]
Duke Energy Carolinas, LLC., Oconee Nuclear Station, Units 1, 2,
and 3 Exemption
1.0 Background
Duke Energy Carolinas, LLC (the licensee) is the holder of Renewed
Facility Operating Licenses DPR-38, DPR-47, and DPR-55, which authorize
operation of the Oconee Nuclear Station, Units 1, 2 and 3 (ONS, Units
1, 2, and 3). The licenses provide, among other things, that the
facilities are subject to all rules, regulations, and orders of the
U.S. Nuclear Regulatory Commission (NRC, the Commission) now or
hereafter in effect.
The facility consists of three pressurized water reactors located
in Oconee County in South Carolina.
2.0 Request/Action
Title 10 of the Code of Federal Regulations (10 CFR), Part 50,
Appendix G, ``Fracture Toughness Requirements,'' requires that fracture
toughness requirements for ferritic materials of pressure-retaining
components of the reactor coolant pressure boundary of light water
nuclear power reactors provide adequate margins of safety during any
condition of normal operation, including anticipated operational
occurrences and system hydrostatic tests, to which the pressure
boundary may be subjected over its service lifetime; and 10 CFR 50.61,
``Fracture Toughness Requirements for Protection Against Pressurized
Thermal Shock Events,'' provides fracture toughness requirements for
protection against pressurized thermal shock (PTS) events.
By letter dated August 3, 2011 (Agencywide Documents Access and
Management System (ADAMS) Accession No. ML11223A010), the licensee
requested exemptions from certain requirements of 10 CFR 50.61 and 10
CFR Part 50, Appendix G. The exemptions would allow use of alternate
initial RTNDT (reference nil ductility temperature), as
described in the NRC-approved topical reports (TRs), BAW-2308,
``Initial RTNDT of Linde 80 Weld Materials,'' Revisions 1-A
and 2-A, for determining the adjusted RTNDT of Linde 80 weld
materials present in the beltline region of the ONS, Units 1, 2, and 3
reactor vessels (RVs).
The licensee requested an exemption from Appendix G to 10 CFR Part
50 to replace the required use of the existing
[[Page 26319]]
Charpy V-notch (Cv) and drop weight-based methodology and
allow the use of an alternate methodology to incorporate the use of
fracture toughness test data for evaluating the integrity of the ONS,
Units 1, 2, and 3 reactor vessel (RV) beltline welds based on the use
of the 1997 and 2002 editions of American Society for Testing and
Materials (ASTM) Standard Test Method E 1921, ``Standard Test Method
for Determination of Reference Temperature T0, for Ferritic
Steels in the Transition Range,'' and American Society of Mechanical
Engineers (ASME), Boiler and Pressure Vessel Code (Code), Code Case N-
629, ``Use of Fracture Toughness Test Data to Establish Reference
Temperature for Pressure Retaining Materials of Section III, Division
1, Class 1.'' The exemption is required since Appendix G to 10 CFR Part
50, through reference to Appendix G to Section XI of the ASME Code
pursuant to 10 CFR 50.55a, requires the use of a methodology based on
Cv and drop weight data.
The licensee also requested an exemption from 10 CFR 50.61(a)(5) to
use an alternate methodology to allow the use of fracture toughness
test data for evaluating the integrity of the ONS, Units 1, 2, and 3
for RV beltline welds based on the use of the 1997 and 2002, editions
of ASTM E 1921, and ASME Code Case N-629. The exemption is required
since the methodology for evaluating RV material fracture toughness in
10 CFR 50.61 requires the use of the Cv and drop weight data
for establishing the PTS reference temperature (RTPTS).
3.0 Discussion
Pursuant to 10 CFR 50.12(a), the Commission may, upon application
by any interested person or upon its own initiative, grant exemptions
from the requirements of 10 CFR Part 50 when (1) the exemptions are
authorized by law, will not present an undue risk to public health or
safety, are consistent with the common defense and security; and (2)
when special circumstances are present. These circumstances include the
special circumstances that allow the licensee an exemption from the use
of the Cv and drop weight-based methodology required by 10
CFR Part 50, Appendix G and 10 CFR 50.61. This exemption only modifies
the methodology to be used by the licensee for demonstrating compliance
with the requirements of 10 CFR Part 50, Appendix G and 10 CFR 50.61,
and does not exempt the licensee from meeting any other requirement of
10 CFR Part 50, Appendix G and 10 CFR 50.61.
Authorized by Law
These exemptions would allow the licensee to use an alternate
methodology to make use of fracture toughness test data for evaluating
the integrity of the ONS, Units 1, 2, and 3 RV beltline welds, and
would not result in changes to operation of the plant. Section 50.60(b)
of 10 CFR Part 50 allows the use of alternatives to the described
requirements in 10 CFR Part 50, Appendix G, or portions thereof, when
an exemption is granted by the Commission under 10 CFR 50.12. In
addition, 10 CFR 50.60(b) of 10 CFR Part 50 permits different NRC
approved methods for use in determining the initial material
properties. As stated above, 10 CFR 50.12(a) allows the NRC to grant
exemptions from the requirements of 10 CFR Part 50, Appendix G and 10
CFR 50.61. The NRC staff has determined that granting of the licensee's
proposed exemptions will not result in a violation of the Atomic Energy
Act of 1954, as amended, or the Commission's regulations. Therefore,
the exemptions are authorized by law.
No Undue Risk to Public Health and Safety
The underlying purpose of Appendix G to 10 CFR Part 50 is to set
forth fracture toughness requirements for ferritic materials of
pressure-retaining components of the reactor coolant pressure boundary
of light water nuclear power reactors to provide adequate margins of
safety during any condition of normal operation, including anticipated
operational occurrences and system hydrostatic tests, to which the
pressure boundary may be subjected over its service lifetime. The
methodology underlying the requirements of Appendix G to 10 CFR Part 50
is based on the use of Cv and drop weight data. The licensee
proposes to replace the use of the existing Cv and drop
weight-based methodology by a fracture toughness-based methodology to
demonstrate compliance with Appendix G to 10 CFR Part 50. The NRC staff
has concluded that the exemptions are justified based on the licensee
utilizing the fracture toughness methodology specified in BAW-2308,
Revisions 1-A \1\ and 2-A, which include the conditions and limitations
delineated in the NRC staff's safety evaluations (SEs), dated August 4,
2005 (ADAMS Accession No. ML052070408), and March 24, 2008 (ADAMS
Accession No. ML080770349). The use of the methodology specified in the
NRC staff's SEs will ensure that pressure-temperature limits developed
for the ONS, Units 1, 2, and 3 RVs will continue to be based on an
adequately conservative estimate of RV material properties and ensure
that the pressure-retaining components of the reactor coolant pressure
boundary retain adequate margins of safety during any condition of
normal operation, including anticipated operational occurrences and
system hydrostatic tests. This exemption only modifies the methodology
to be used by the licensee for demonstrating compliance with the
requirements of Appendix G to 10 CFR Part 50, and does not exempt the
licensee from meeting any other requirement of Appendix G to 10 CFR
Part 50.
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\1\ Note, a revision number including a ``-A'' denotes an NRC-
staff approved version of the TR which includes the NRC staff's
final safety evaluation.
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The underlying purpose of 10 CFR 50.61 is to establish requirements
for evaluating the fracture toughness of RV materials to ensure that a
licensee's RV will be protected from failure during a PTS event. The
licensee seeks an exemption from 10 CFR 50.61 to use a methodology for
the determination of adjusted/indexing reference temperatures. The
licensee proposes to use ASME Code Case N-629 and the methodology
outlined in its submittal, which are based on the use of fracture
toughness data, as an alternative to the Cv and drop weight-
based methodology required by 10 CFR 50.61 for establishing the
initial, unirradiated properties when calculating RTPTS
values. The NRC staff has concluded that the exemption is justified
based on the licensee utilizing the methodology specified in TRs BAW-
2308, Revisions 1-A and 2-A. These TRs established an alternative
method for determining initial (unirradiated) material reference
temperatures for RV welds manufactured using Linde 80 weld flux (i.e.,
``Linde 80 welds'') and established weld wire heat-specific and Linde
80 weld generic values of this reference temperature. These weld wire
heat-specific and Linde 80 weld generic values may be used in lieu of
the RTNDT determined as specified by paragraph NB-2331 of
Section III of the ASME Code. Regulations associated with the
determination of RV material properties involving protection of the RV
from brittle failure or ductile rupture includes Appendix G to 10 CFR
Part 50 and 10 CFR 50.61, the PTS rule. These regulations require that
the initial (unirradiated) material reference temperature,
RTNDT, be determined in accordance with the provisions of
the ASME Code, and provide the process for
[[Page 26320]]
determination of RTPTS, the reference temperature
RTNDT, evaluated for the end of license fluence.
In TR BAW-2308, Revision 1, the Babcock and Wilcox Owners Group
(B&WOG) proposed to perform fracture toughness testing based on the
application of the Master Curve evaluation procedure, which permits
data obtained from sample sets tested at different temperatures to be
combined, as the basis for redefining the initial (unirradiated)
material properties of Linde 80 welds. NRC staff evaluated this
methodology for determining Linde 80 weld initial (unirradiated)
material properties and uncertainty in those properties, as well as the
overall method for combining unirradiated material property
measurements based on To values (i.e., IRTTo),
with property shifts from models in Regulatory Guide (RG) 1.99,
Revision 2, ``Radiation Embrittlement of Reactor Vessel Materials,''
which are based on Cv testing and a defined margin term to
account for uncertainties in the NRC staff SE. Table 3 in the NRC
staff's August 4, 2005 SE of BAW-2308, Revision 1, contains the NRC
staff-accepted IRTTO and initial margin (denoted as
[sigma]i) for specific Linde 80 weld wire heat numbers. In
accordance with the conditions and limitations outlined in the NRC
staff's August 4, 2005 SE of TR BAW-2308, Revision 1, for utilizing the
values in Table 3: the licensee's proposed methodology has (1) utilized
the appropriate NRC staff-accepted IRTTo and
[sigma]i values for Linde 80 weld wire heat numbers; (2)
applied chemistry factors greater than 167 [deg]F (the weld wire heat-
specific chemical composition, via the methodology of RG 1.99, Revision
2, indicated that higher chemistry factors are applicable); (3) applied
a value of 28 [deg]F for [sigma][Delta] in the margin term;
and (4) submitted values for [Delta]RTNDT and the margin
term for each Linde 80 weld in the RV through the end of the current
operating license. Additionally, the NRC's SE for TR BAW-2308, Revision
2 concludes that the revised IRTT0 and [sigma]i
values for Linde 80 weld materials are acceptable for referencing in
plant-specific licensing applications as delineated in TR BAW-2308,
Revision 2 and to the extent specified under Section 4.0, Limitations
and Conditions, of the SE., which states: ``Future plant-specific
applications for RPVs [reactor pressure vessels] containing weld heat
72105, and weld heat 299L44, of Linde 80 welds must use the revised
IRTTo and [sigma]i, values in TR BAW-2308,
Revision 2.'' The NRC staff notes that heat 299L44 is used in one ONS 1
RV beltline weld and one ONS 2 RV beltline weld and heat. The NRC staff
also notes heat 72105 is used in an ONS 3 beltline weld. The NRC staff
verified that the revised IRTT0 and [sigma]i
values from TR BAW-2308, Revision 2 were used for these three welds.
The licensee also used the revised IRTTo and
[sigma]i, values in TR BAW-2308, Revision 2 for the other
weld heats. Although the revised IRTTo values for the weld
heats other than 72105 and 299L44 are lower than the values given in
the NRC staff's SE of BAW-2308, Revision 1, these values are acceptable
because the NRC staff determined in its SE for BAW-2308, Revision 2,
that the modified methodology used to calculate these values is
acceptable, and more accurate than the methodology used to generate the
values given in the NRC staff's SE of BAW-2308, Revision 1. Therefore,
all conditions and limitations outlined in the NRC staff SEs for TRs
BAW-2308, Revisions 1 and 2, have been met for ONS, Units 1, 2, and 3.
The use of the methodology in TRs BAW-2308, Revisions 1-A and 2-A,
will ensure the PTS evaluation developed for the ONS, Units 1, 2, and 3
RVs will continue to be based on an adequately conservative estimate of
RV material properties, and ensure the RV will be protected from
failure during a PTS event. Also, when additional fracture toughness
data relevant to the evaluation of the ONS, Units 1, 2, and 3 RV welds
is acquired as part of the surveillance program, these data must be
incorporated into the evaluation of the ONS, Units 1, 2, and 3 RV
fracture toughness requirements.
Based on the above, no new accident precursors are created by
allowing an exemption to use an alternate methodology to comply with
the requirements of 10 CFR 50.61 in determining adjusted/indexing
reference temperatures, thus, the probability of postulated accidents
is not increased. Also, based on the above, the consequences of
postulated accidents are not increased. Therefore, there is no undue
risk to public health and safety. On February 3, 2010, a new rule, 10
CFR 50.61a, ``Alternate Fracture Toughness Requirements for Protection
Against [PTS] Events,'' became effective. The NRC staff reviewed this
new rule against the licensee's exemption request and determined that
there is no effect on the exemption request. The new rule does not
modify the requirements from which the licensee has sought an
exemption, and the alternative provided by the new rule does not
address the scope of issues associated with both 10 CFR 50.61 and 10
CFR Part 50, Appendix G that the requested exemption does.
Consistent With Common Defense and Security
The proposed exemption would allow the licensee to use an alternate
methodology to allow the use of fracture toughness test data for
evaluating the integrity of the ONS, Units 1, 2, and 3 RV beltline
welds. This change has no relation to security issues. Therefore, the
common defense and security is not impacted by these exemptions.
Special Circumstances
Special circumstances, in accordance with 10 CFR 50.12(a)(2)(ii),
are present whenever application of the regulation in the particular
circumstances is not necessary to achieve the underlying purpose of the
rule. The underlying purpose of 10 CFR Part 50, Appendix G and 10 CFR
50.61 is to protect the integrity of the reactor coolant pressure
boundary by ensuring that each reactor vessel material has adequate
fracture toughness. Therefore, since the underlying purpose of 10 CFR
Part 50, Appendix G and 10 CFR 50.61 is achieved by an alternative
methodology for evaluating RV material fracture toughness, the special
circumstances required by 10 CFR 50(a)(2)(ii) for the granting of an
exemption from portions of the requirements of 10 CFR Part 50, Appendix
G and 10 CFR 50.61 exist.
4.0 Conclusion
Accordingly, the Commission has determined that, pursuant to 10 CFR
50.12(a), the exemption is authorized by law, will not present an undue
risk to the public health and safety, and is consistent with the common
defense and security. Also, special circumstances are present.
Therefore, the Commission hereby grants Duke Energy Carolinas, LLC an
exemption from certain requirements of Appendix G to 10 CFR Part 50 and
10 CFR 50.61, to allow an alternative methodology to incorporate the
use of fracture toughness test data for evaluating the integrity of the
ONS, Units 1, 2, and 3 reactor vessel (RV) beltline welds that is based
on using fracture toughness test data to determine initial,
unirradiated properties.
Pursuant to 10 CFR 51.32, ``Finding of no significant impact,'' the
Commission has determined that the granting of this exemption will not
have a significant effect on the quality of the human environment 77 FR
21594.
This exemption is effective upon issuance.
Dated at Rockville, Maryland, this 25th day of April 2012.
[[Page 26321]]
For The Nuclear Regulatory Commission.
Michele G. Evans,
Director, Division of Operating Reactor Licensing, Office of Nuclear
Reactor Regulation.
[FR Doc. 2012-10698 Filed 5-2-12; 8:45 am]
BILLING CODE 7590-01-P