[Federal Register Volume 88, Number 43 (Monday, March 6, 2023)]
[Notices]
[Pages 13855-13859]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-04501]
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NUCLEAR REGULATORY COMMISSION
[NRC-2023-0036]
NRC Bulletin 2012-01: Design Vulnerability in Electric Power
System
AGENCY: Nuclear Regulatory Commission.
ACTION: Bulletin; closure.
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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is issuing this
notice to inform all holders of operating licenses and combined
licenses for nuclear power reactors of the closure of ``NRC Bulletin
2012-01: Design Vulnerability in Electric Power System'' (Bulletin).
NRC has completed evaluations and inspections of the responses and
other actions taken by the licensees of the nuclear power plants in
response to NRC Bulletin 2012-01. The staff has approved the actions to
be taken by the licensee for Vogtle Units 3 and 4 following
commencement of operations and will inspect these actions under the
Reactor Oversight Process. The NRC staff concludes that any potential
adverse impact on nuclear plant safety due to an open phase condition
(OPC) in the plant offsite power system has been adequately addressed
by the licensees.
DATES: NRC Bulletin 2012-01 is closed effective March 6, 2023.
ADDRESSES: Please refer to NRC-2023-0036 when contacting the NRC about
the availability of information regarding this document. You may obtain
publicly available information related to this document using any of
the following methods:
Federal Rulemaking Website: Go to https://www.regulations.gov and search for NRC-2023-0036. Address questions
about Docket IDs in Regulations.gov to Stacy Schumann; telephone: 301-
415-0624; email: [email protected]. For technical questions,
contact the individual listed in the For Further Information Contact
section of this document.
NRC's Agencywide Documents Access and Management System
(ADAMS): You may obtain publicly available documents online in the
ADAMS Public Documents collection at https://www.nrc.gov/reading-rm/adams.html. To begin the search, select ``Begin Web-based ADAMS
Search.'' For problems with ADAMS, please contact the NRC's Public
Document Room (PDR) reference staff at 1-800-397-4209, 301-415-4737, or
by email to [email protected]. For the convenience of the reader,
instructions about obtaining materials referenced in
[[Page 13856]]
this document are provided in the ``Availability of Documents''
section.
NRC's PDR: You may examine and purchase copies of public
documents, by appointment, at the NRC's PDR, Room P1 B35, One White
Flint North, 11555 Rockville Pike, Rockville, Maryland 20852. To make
an appointment to visit the PDR, please send an email to
[email protected] or call 1-800-397-4209 or 301-415-4737, between 8
a.m. and 4 p.m. eastern time (ET), Monday through Friday, except
Federal holidays.
FOR FURTHER INFORMATION CONTACT: Wendell Morton, Office of Nuclear
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001, telephone: 301-415-1658, email: [email protected].
SUPPLEMENTARY INFORMATION:
I. Introduction
The NRC is providing this technical summary in this Federal
Register notice (FRN) to explain the basis for closure of ``NRC
Bulletin 2012-01: Design Vulnerability in Electric Power System.'' This
FRN informs external stakeholders that the adverse impacts on nuclear
plant safe operation due to an OPC in the plant offsite power system
have been adequately addressed, and the Bulletin is closed.
II. Background
An OPC event occurred in the offsite power circuit at Bryon Unit 2
on January 30, 2012. The station auxiliary transformer (SAT) (offsite
power source) high-voltage side event caused unbalanced voltage
conditions on the low-voltage side of the SAT, which led to a reactor
trip and tripping of certain safety related loads. The existing
undervoltage degraded voltage protection scheme failed to detect the
unbalanced voltage and did not automatically separate the degraded
offsite power source from the onsite power source. Operator action was
required to bring the plant to a safe shutdown condition. The event is
further described in the ``Availability of Documents'' section.
In addition to the event previously described, two additional
events were discussed in NRC Information Notice 2012-03. In these
events, the OPC occurred on the offsite circuits that usually remain
energized without a load or with a light load during normal conditions.
At the related plants, the safety and non-safety-related loads are
normally fed from the main generator through unit auxiliary
transformers, therefore the offsite circuits that feed the safety-
related loads during plant startup or after unit trip usually remain on
no-load or are lightly loaded during normal plant conditions. The OPCs
at these plants were not detected for many days. If a design basis
event had occurred simultaneously, the unbalanced voltages at the
safety-related buses would have increased due to shifting of loads from
unit auxiliary transformers to offsite circuits due an OPC and could
impact the safety of plants. The degree of unbalanced voltage
conditions on the plant buses due to an OPC in the offsite power
circuit is dependent on the offsite circuit design parameters, plant
configuration, and plant loading conditions. The unbalanced voltage
condition can potentially lead to either degraded operation of the
safety-related loads if the voltage unbalance is small (about five
percent or less) or tripping of the safety-related loads if the voltage
unbalance is large, either of which is an unsafe condition. Therefore,
the timely mitigation of an OPC is necessary to ensure the safety of
the plant.
In light of the Byron and other events, on July 27, 2012, the NRC
issued Bulletin 2012-01: Design Vulnerability in Electric Power System.
The Bulletin required that all holders of operating licenses and
combined licenses for nuclear power reactors verify compliance with the
regulatory requirements of General Design Criterion (GDC) 17,
``Electric Power Systems,'' in Appendix A, ``General Design Criteria
for Nuclear Power Plants,'' to Part 50 of title 10 of the Code of
Federal Regulations (10 CFR) or the applicable principal design
criteria in the licensees' updated final safety analysis report; and
the design criteria for protection systems under 10 CFR 50.55a(h)(2) or
10 CFR 50.55a(h)(3). The licensees were requested to describe plant
design features that would allow the existing protective schemes to
detect and respond to an OPC.
Licensees provided responses to the Bulletin and the NRC staff
issued a summary report of the responses on February 26, 2013. In the
summary report, the staff determined that for the operating plants, one
or both trains of safety related electrical buses could be affected by
an OPC. The NRC staff became aware of the OPC during an event at Byron
Unit 2 that rendered both the offsite power system and the onsite power
system unable to perform their intended safety functions. The NRC
determined further regulatory action was required to ensure detection
and automatic system response to an OPC at nuclear power plants.
Further, the NRC determined that licensees should ensure that offsite
and onsite electric power systems would remain available to permit the
functioning of structures, systems, and components important to safety
in the event of anticipated operational occurrences and accidents.
III. Discussion
Two public meetings were held with industry on February 13, 2013,
and June 13, 2013, in which various industry representatives presented
possible solutions for the detection and protection from the new
challenge faced due to OPCs. The minutes from these meetings as well as
presentations by industry representatives are available in the
``Availability of Documents'' section.
In its letter dated October 9, 2013, Nuclear Energy Institute (NEI)
provided a voluntary industry initiative plan, which included a formal
commitment by the licensees to address plant vulnerabilities due to
potential OPCs. The initiative goal and definition included: an OPC
will not prevent functioning of important-to-safety structures,
systems, and components. An OPC is defined as an open phase, with or
without a ground, which is located on the high voltage side of a
transformer connecting a GDC 17 off-site power circuit to the
transmission system. The initiative was slated for completion by
December 31, 2017.
Bulletin 2012-01 stated that GDC 17 in 10 CFR part 50, Appendix A,
and 10 CFR 50.55a(h)(2) for operating plants or 10 CFR 50.55a(h)(3) for
any plants after May 13, 1999, are applicable.
In its letter dated March 21, 2014, NEI provided its perspective
that the protection system requirements described in 10 CFR
50.55a(h)(2), ``Protection systems,'' do not apply to the Open Phase
Isolation Systems (OPISs).
In the letter dated August 14, 2014, NEI provided the industry
position with respect to various regulatory issues related to OPC.
The NRC provided a November 25, 2014, response to NEI to address
the issues raised in the March 2014 and August 2014 letters, and
explained that to address OPCs, four functional requirements should be
met. The letter also stated that until each licensee has addressed OPCs
and informed the NRC that it is in full compliance with GDC 17, or the
principal design criteria specified in the updated final safety
analysis report for the specific plant regarding OPC, the staff would
be recommending an interim enforcement policy (IEP) to the Commission.
NEI provided Revision 1 of the voluntary industry initiative dated
March 16, 2015, with a schedule change for OPC modifications completion
from
[[Page 13857]]
December 31, 2017, to December 31, 2018.
In SECY-16-0068, dated May 31, 2016, the NRC staff proposed a
revision to the Enforcement Policy to permit the staff to exercise
enforcement discretion for certain noncompliance's with technical
specifications or GDC 17, and certain nonconformances with the
analogous principal design criteria specified in the updated final
safety analysis report, as well as noncompliance's with 10 CFR
50.55a(h)(2) or 10 CFR 50.55a(h)(3), and 10 CFR 50.36. The potential
violations could be those associated with inoperable electrical power
systems (offsite and onsite) caused by an OPC design vulnerability in
the offsite electric power system that would require a reactor shutdown
or prevent a reactor startup if a licensee could not come into
conformance within the technical specification required completion
times.
In SRM-SECY-16-0068 dated March 9, 2017, the Commission disapproved
the staff's request to establish an IEP. Instead, the Commission
directed the staff to (1) verify that licensees have appropriately
implemented the voluntary industry initiative; (2) update the Reactor
Oversight Process to provide periodic oversight of industry's
implementation of the OPC initiative; and (3) close the Bulletin once
satisfactory implementation of the technical resolution has been
verified for each licensee.
On October 31, 2017, the NRC staff issued Temporary Instruction
2515/194, to verify that licensees appropriately implemented the NEI
voluntary industry initiative. The NRC inspectors verified
implementation at plants where OPC modifications were substantially
complete.
NEI provided Revision 2 of the voluntary industry initiative, dated
September 20, 2018, with the completion schedule changed from December
31, 2018, to December 31, 2019. NEI stated that many plants had
completed installation of OPIS with other plants scheduled to complete
during 2018. However, the monitoring data to date had indicated that
installed OPISs would have experienced undesirable spurious actuations
if the automatic trip functions had been activated. NEI proposed
extended monitoring periods so that licensees could refine OPIS
setpoints to minimize spurious actuations.
Due to continuing spurious actuations of OPIS designs observed at
some plants, NEI provided Revision 3 dated June 6, 2019, of the
initiative. This revision included an option to perform a risk
evaluation under certain boundary conditions to support an alarm and
manual response to an OPC, instead of an automatic trip response. For
plants adopting the risk-informed option, the OPIS design would change
from ``alarm and automatically trip (isolate)'' to ``alarm (detect) and
manual actions'' to isolate the OPC. Written plant alarm response
procedures would allow operators to diagnose and take manual actions to
mitigate an OPC. NEI also separately provided NEI 19-02, ``Guidance for
Assessing Open Phase Condition Implementation Using Risk Insights,''
referenced in Revision 3 of the initiative.
To evaluate whether safety significance justified requiring
automatic OPIS actuation, the NRC staff performed a backfit screening
and documented the results in a memo dated May 21, 2020. The analysis
determined that automatic OPIS actuation would not result in a
substantial increase in the overall protection of the public health and
safety. Therefore, the risk-informed option in Revision 3 to the
voluntary industry initiative was acceptable.
On August 18, 2020, the NRC staff issued Revision 2 of the
Temporary Instruction 2515/194, to verify that licensees have
appropriately implemented the NEI voluntary industry initiative,
including licensees that adopted the risk-informed option. For
licensees where OPIS implementation was still in the monitoring mode
and spurious initiations continued to occur, many changed to the risk-
informed option of the voluntary industry initiative. Approximately 65
percent of operating power reactors have adopted the risk-informed
option. This change, and the COVID-19 pandemic, resulted in delays in
licensees' implementation of the voluntary industry initiative and the
subsequent inspections at many plants.
As required by SRM-SECY-16-0068, the Reactor Oversight Process
Inspection Procedures and the Inspection Manual Chapter were revised to
provide periodic oversight of industry's implementation of the OPC
voluntary industry initiative.
IV. Conclusion
The staff issued closure letters to each licensee other than
Southern Nuclear Company for Vogtle Units 3 and 4. ADAMS accession
numbers to these letters are in the ``Availability of Documents''
section. The closure letters provide further details concerning how
licensees addressed OPC at their facilities.
The staff has approved the actions to be taken by the licensee for
Vogtle Units 3 and 4 following commencement of operations, by letter
dated July 5, 2019, agreeing to the due dates and will inspect these
actions under the Reactor Oversight Process. By letter dated August 29,
2018, Southern Nuclear Company to NRC (Vogtle Units 3 and 4), provided
regulatory commitments and due dates regarding the OPC.
The licensees of the following plants received Bulletin 2012-01,
but subsequently permanently ceased operation prior to addressing the
Bulletin: Crystal River 3; Duane Arnold; Fort Calhoun; Indian Point 2;
Kewaunee; Oyster Creek; Palisades; Pilgrim 1; San Onofre 2; San Onofre
3; Three Mile Island 1; Vermont Yankee.
Based on the actions taken by the NRC and licensees in response to
the Bulletin, the NRC staff finds that all operating plants will
continue to operate safely or safely shut down in response to an OPC
event. Therefore, Bulletin 2012-01 is closed.
V. Availability of Documents
The documents identified in the following table are available to
interested persons through one or more of the following methods, as
indicated.
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Document description ADAMS accession No.
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Information Notice 2012-03: Design Vulnerability ML120480170.
in Electric Power System, dated March 1, 2012.
Presentation by Exelon Nuclear--Byron Station ML120810365.
Single Phase Failure, dated March 22, 2012.
Licensee Event Report 2012-001-01 ``Unit 2 Loss ML12272A358.
of Normal Offsite Power and Reactor Trip and
Unit 1 Loss of Normal Offsite Power Due to
Failure of System Auxiliary Transformer
Inverted Insulators,'' dated September 28, 2012.
Byron Unit 2--NRC Special Inspection Team (SIT) ML12087A213.
Report, dated March 27, 2012.
Bulletin 2012-01: Design Vulnerability in ML12074A115.
Electric Power System, dated July 27, 2012.
Summary report of licensee responses, dated ML13052A711.
February 26, 2013.
Public meeting summary.......................... ML13066A774 (package).
Public meeting summary.......................... ML13196A002 (package).
[[Page 13858]]
Nuclear Energy Institute (NEI) voluntary ML13333A147.
industry initiative plan, dated October 9, 2013.
NEI perspective letter on Open Phase Isolation ML14087A252 (package).
Systems (OPISs), dated March 21, 2014.
NEI letter that provided the industry position ML14226A804 (package).
with respect to various regulatory issues
related to OPC, dated August 14, 2014.
NRC's response to NEI to address the issues ML14120A203.
raised in the March 2014 and August 2014
letters, and explained that to address OPCs,
four functional requirements should be met,
dated November 25, 2014.
NEI Revision 1 of the voluntary industry ML15075A454 (package).
initiative plan, dated March 16, 2015.
SECY-16-0068, dated May 31, 2016................ ML15219A327, Enclosure
ML15219A330.
SRM-SECY-16-0068, dated March 9, 2017........... ML17068A297.
NRC staff issued Temporary Instruction 2515/194, ML17137A416.
dated October 31, 2017.
NEI Revision 2 of the voluntary industry ML18268A114.
initiative, dated September 20, 2018.
NEI Revision 3 of the voluntary industry ML19163A176.
initiative, dated June 6, 2019.
NEI 19-02, ``Guidance for Assessing Open Phase ML19172A086.
Condition Implementation Using Risk Insights,''
dated June 20, 2019.
NRC backfit screening memo, dated May 21, 2020.. ML19198A304.
NRC Revision 2 of the Temporary Instruction 2515/ ML20230A328.
194, dated August 18, 2020.
NRC Response to Supplemental Information for ML19182A206.
Bulletin 2012-01, Vogtle 3 and 4 (052-25 and 52-
026), dated July 5, 2019.
Vogtle, Units 3 and 4, Supplement to Response to ML18242A012.
NRC Bulletin 2012-01, Design Vulnerability in
Electric Power System, dated August 29, 2018.
Arkansas Nuclear 1 Closure Letter, dated March ML21049A307.
5, 2021.
Arkansas Nuclear 2 Closure Letter, dated March ML21049A307.
5, 2021.
Beaver Valley 1 Closure Letter, dated July 15, ML22189A184.
2022.
Beaver Valley 2 Closure Letter, dated July 15, ML22189A184.
2022.
Braidwood 1 Closure Letter, dated April 27, 2021 ML21102A182.
Braidwood 2 Closure Letter, dated April 27, 2021 ML21102A182.
Browns Ferry 1 Closure Letter, dated May 1, 2020 ML20104A192.
Browns Ferry 2 Closure Letter, dated May 1, 2020 ML20104A192.
Browns Ferry 3 Closure Letter, dated May 1, 2020 ML20104A192.
Brunswick 1 Closure Letter, dated October 12, ML21278A002.
2021.
Brunswick 2 Closure Letter, dated October 12, ML21278A002.
2021.
Byron 1 Closure Letter, dated April 27, 2021.... ML21102A182.
Byron 2 Closure Letter, dated April 27, 2021.... ML21102A182.
Callaway Closure Letter, dated July 27, 2021.... ML21201A105.
Calvert Cliffs 1 Closure Letter, dated September ML21225A432.
7, 2021.
Calvert Cliffs 2 Closure Letter, dated September ML21225A432.
7, 2021.
Catawba 1 Closure Letter, dated October 19, 2021 ML21272A183.
Catawba 2 Closure Letter, dated October 19, 2021 ML21272A183.
Clinton Closure Letter, dated July 8, 2022...... ML22186A150.
Columbia Closure Letter, dated June 29, 2021.... ML21165A344.
Comanche Peak 1 Closure Letter, dated July 26, ML23025A353.
2023.
Comanche Peak 2 Closure Letter, dated July 26, ML23025A353.
2023.
Cooper Closure Letter, dated November 22, 2021.. ML21323A074.
D.C. Cook 1 Closure Letter, dated May 26, 2021.. ML22146A113.
D.C. Cook 2 Closure Letter, dated May 26, 2021.. ML22146A113.
Davis-Besse Closure Letter, dated July 21, 2022. ML22195A223.
Diablo Canyon 1 Closure Letter, dated April 29, ML22108A286.
2022.
Diablo Canyon 2 Closure Letter, dated April 29, ML22108A286.
2022.
Dresden 2 Closure Letter, dated April 27, 2021.. ML21102A182.
Dresden 3 Closure Letter, dated April 27, 2021.. ML21102A182.
Farley 1 Closure Letter, dated August 23, 2021.. ML21216A316.
Farley 2 Closure Letter, dated August 23, 2021.. ML21216A316.
Fermi 2 Closure Letter, dated July 21, 2022..... ML22188A089.
FitzPatrick Closure Letter, November 16, 2021... ML21300A006.
Ginna Closure Letter, dated September 20, 2021.. ML21245A098.
Grand Gulf Closure Letter, dated March 5, 2021.. ML21049A307.
Harris 1 Closure Letter, dated September 29, ML21252A389.
2021.
Hatch 1 Closure Letter, dated September 20, 2021 ML21253A113.
Hatch 2 Closure Letter, dated September 20, 2021 ML21253A113.
Hope Creek 1 Closure Letter, dated March 11, ML22060A057.
2022.
Indian Point 3 Closure Letter, dated March 5, ML21049A307.
2021.
La Salle 1 Closure Letter, dated April 27, 2021. ML21102A182.
La Salle 2 Closure Letter, dated April 27, 2021. ML21102A182.
Limerick 1 Closure Letter, dated September 13, ML21245A084.
2021.
Limerick 2 Closure Letter, dated September 13, ML21245A084.
2021.
McGuire 1 Closure Letter, dated October 27, 2021 ML21293A026.
McGuire 2 Closure Letter, dated October 27, 2021 ML21293A026.
Millstone 2 Closure Letter, dated November 15, ML21295A412.
2021.
Millstone 3 Closure Letter, dated November 15, ML21295A412.
2021.
Monticello Closure Letter, dated July 29, 2022.. ML22189A019.
Nine Mile Point 1 Closure Letter, dated ML21239A052.
September 7, 2021.
Nine Mile Point 2 Closure Letter, dated ML21239A052.
September 7, 2021.
North Anna 1 Closure Letter, dated May 5, 2020.. ML20065L173.
[[Page 13859]]
North Anna 2 Closure Letter, dated May 5, 2020.. ML20065L173.
Oconee 1 Closure Letter, dated February 17, 2022 ML22045A024.
Oconee 2 Closure Letter, dated February 17, 2022 ML22045A024.
Oconee 3 Closure Letter, dated February 17, 2022 ML22045A024.
Palo Verde 1 Closure Letter, April 20, 2022..... ML22102A262.
Palo Verde 2 Closure Letter, April 20, 2022..... ML22102A262.
Palo Verde 3 Closure Letter, April 20, 2022..... ML22102A262.
Peach Bottom 2 Closure Letter, dated September ML21196A010.
7, 2021.
Peach Bottom 3 Closure Letter dated September 7, ML21196A010.
2021.
Perry 1 Closure Letter, dated July 13, 2022..... ML22189A177.
Point Beach 1 Closure Letter, dated July 13, ML21187A153.
2021.
Point Beach 2 Closure Letter, dated July 13, ML21187A153.
2021.
Prairie Island 1 Closure Letter, dated May 26, ML22145A020.
2022.
Prairie Island 2 Closure Letter, dated May 26, ML22145A020.
2022.
Quad Cities 1 Closure Letter, dated April 27, ML21102A182.
2021.
Quad Cities 2 Closure Letter, dated April 27, ML21102A182.
2021.
River Bend 1 Closure Letter, dated March 5, 2021 ML21049A307.
Robinson 2 Closure Letter, dated March 29, 2022. ML22083A003.
Saint Lucie 1 Closure Letter, dated October 28, ML21281A012.
2021.
Saint Lucie 2 Closure Letter, dated October 28, ML21281A012.
2021.
Salem 1 Closure Letter, dated November 19, 2021. ML21320A204.
Salem 2 Closure Letter, dated November 19, 2021. ML21320A204.
Seabrook 1 Closure Letter, dated March 24, 2020. ML20071C899.
Sequoyah 1 Closure Letter, dated May 1, 2020.... ML20104A192.
Sequoyah 2 Closure Letter, dated May 1, 2020.... ML20104A192.
South Texas 1 Closure Letter, dated August 5, ML20206L260.
2020.
South Texas 2 Closure Letter, dated August 5, ML20206L260.
2020.
Surry 1 Closure Letter, dated May 5, 2020....... ML20065L173.
Surry 2 Closure Letter, dated May 5, 2020....... ML20065L173.
Susquehanna 1 Closure Letter, dated December 6, ML21335A422.
2021.
Susquehanna 2 Closure Letter, dated December 6, ML21335A422.
2021.
Turkey Point 3 Closure Letter, dated July 19, ML22187A277.
2022.
Turkey Point 4 Closure Letter, dated July 19, ML22187A277.
2022.
VC Summer Closure Letter, dated September 14, ML21242A330.
2021.
Vogtle 1 Closure Letter, dated October 22, 2021. ML21279A167.
Vogtle 2 Closure Letter, dated October 22, 2021. ML21279A167.
Waterford 3 Closure Letter, dated June 22, 2020. ML20171A366.
Watts Bar 1 Closure Letter, dated May 1, 2020... ML20104A192.
Watts Bar 2 Closure Letter, dated May 1, 2020... ML20104A192.
Wolf Creek 1 Closure Letter, dated February 10, ML22040A158.
2022.
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Dated: March 1, 2023.
For the Nuclear Regulatory Commission.
Lisa M. Regner,
Chief, Generic Communication and Operating Experience Branch, Division
of Reactor Oversight, Office of Nuclear Reactor Regulation.
[FR Doc. 2023-04501 Filed 3-3-23; 8:45 am]
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