[Federal Register Volume 89, Number 218 (Tuesday, November 12, 2024)]
[Notices]
[Pages 89052-89056]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-26075]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-352; 50-353; NRC-2024-0194]
Constellation Energy Generation LLC; Limerick Generating Station,
Units 1 and 2; Exemption
AGENCY: Nuclear Regulatory Commission.
ACTION: Notice; issuance.
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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is issuing an
exemption in response to letter dated February 17, 2023, as
supplemented by letters dated July 21, 2023, July 31, 2023, August 16,
2023, and May 28, 2024. Constellation Energy Generation LLC
(Constellation, the licensee) has requested exemption from specific
requirements for reduction of risk from anticipated transients without
scram (ATWS) events for light-water-cooled nuclear power plants.
Constellation is the holder of the Renewed Facility Operating License
Nos. NPF-39 and NPF-85, which authorize the operation of Limerick
Generating Station, Units 1 and 2 (Limerick).
DATES: This document was published in the Federal Register on November
12, 2024.
ADDRESSES: Please refer to Docket ID NRC-2024-0194 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 Docket ID NRC-2024-0194. 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, at 301-415-4737,
or by email to [email protected]. The ADAMS accession number for
each document referenced (if it is available in ADAMS) is provided the
first time that it is mentioned in this document.
NRC's PDR: The PDR, where you may examine and order copies
of publicly available documents, is open by appointment. 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: Michael Marshall, Office of Nuclear
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001, telephone: 301-415-2871; email: [email protected].
SUPPLEMENTARY INFORMATION:
I. Background
Constellation is the holder of the Renewed Facility Operating
License Nos. NPF-39 and NPF-85, which authorize the operation of
Limerick Generating Station, Units 1 and 2. The facilities consist of
boiling water reactors (BWRs) located in Montgomery County,
Pennsylvania and is located next to the Schuylkill River.
By letter dated February 17, 2023, as supplemented by letters dated
July 21, 2023, July 31, 2023, August 16, 2023, and May 28, 2024,
Constellation has requested exemption from specific requirements of
section 50.62 of title 10 of the Code of Federal Regulations (10 CFR),
``Requirements for reduction of risk from anticipated transients
without scram (ATWS) events for light-water-cooled nuclear power
plants.'' A publicly available version of each letter is in ADAMS under
Accession Nos. ML23052A023, ML23202A219, ML23212B105, ML23228A094, and
ML24149A211, respectively. Constellation specifically requests an
exemption from the requirements of 10 CFR 50.62(c)(3) and the automatic
activation requirements of 10 CFR 50.62(c)(4) and (c)(5) for a period
of 30 days before the calendar year 2027 refueling outage for Unit 2
and for a period of 30 days before the calendar year 2026 refueling
outage for Unit 1. In conjunction with this exemption request the
licensee submitted an associated license amendment request (ADAMS
Accession No. ML23052A023) to add operational constraints to the
limiting conditions of operations in the technical specifications (TSs)
for each Limerick unit to be in effect during each respective exemption
period to ensure that there is no increase in the potential
[[Page 89053]]
consequences of an ATWS. In the license amendment request, the licensee
also described additional ATWS mitigation strategies (i.e.,
compensatory measures) they will implement in addition to the TS
changes. Specifically, in Attachment 7 of the license amendment
request, the licensee stated, ``With the additional compensatory
measures being taken, the same level ATWS mitigation protection will be
achieved during the 30-day RRCS demolition period when the automatic
systems designed to meet compliance with 10 CFR 50.62 ATWS requirements
are out of service.''
II. Request/Action
Pursuant to 10 CFR 50.62, the Commission's regulations establish
specific ATWS mitigation requirements for nuclear power plants, with
paragraphs (c)(3), (c)(4), and (c)(5) applicable to BWRs like Limerick
Units 1 and 2. The systems that are required are to be operational are
the alternate rod injection (ARI) system, the automatic activation of
the standby liquid control system (SLCS), and equipment to trip the
reactor coolant recirculation pumps automatically under conditions of
an ATWS. Constellation requested an exemption from all requirements for
ARI capability in 10 CFR 50.62(c)(3) and only from the automatic
response capability in 10 CFR 50.62(c)(4) for SLCS and in 10 CFR
50.62(c)(5) recirculation pumps trip (RPT) for a period of 30-days
prior to the calendar year 2027 refueling outage for Unit 2 and the
calendar year 2026 refueling outage for Unit 1. During each 30-day
period prior to the refueling outage, referred to by Constellation as
the 30-day redundant reactivity control system (RRCS) demolition
period, Constellation will begin upgrading the RRCS by demolishing the
existing analog system and replacing it with a new digital system which
will be completed during the refueling outage. To support RRCS
demolition period, Constellation submitted a license amendment request
to temporarily modify certain TS limiting conditions for operation to:
(1) not require operability of certain automatic initiation features of
ATWS equipment that are in the scope of work being performed, and (2)
establish operating condition that ensure that there would be no
increase in the consequences of an ATWS event should one occur during
the 30-day RRCS demolition period. In addition, they also requested
that certain surveillance requirements related to the ATWS features
within the scope of work not be required during the RRCS demolition
period. The limiting condition for operation changes temporarily limit
the maximum reactor thermal power during the 30-day RRCS demolition
period based on combination of operating parameters. Specifically, the
maximum power at which the plant is limited based on the number of out
of safety relief valves, the ability to manually initiate SLCS within
five minutes, a minimum suppression pool water level, and the
operability of the reactor water level 3 recirculation runback system.
The operational constraints identified by Constellation for each
identified maximum thermal power limit are listed in the following
table.
Exemption's Operational Constraints for a Period of 30-Days
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Maximum number of SRVs Manual initiation time Minimum suppression
Maximum reactor thermal power out of service for SLCS (minutes) pool water level (feet) Additional system credited
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90%....................................... 0 5 23 Level 3 Recirculation Runback.
87%....................................... 0 5 22 Level 3 Recirculation Runback.
84%....................................... 1 5 22 Level 3 Recirculation Runback.
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In addition, as stated in their license amendment request, as
evaluated by NRC staff in the safety evaluation (SE) to the license
amendment request (LAR) to reduce the risk from a potential ATWS event
during the 30-day period, the licensee will implement additional ATWS
mitigation strategies to provide an equivalent level of ATWS protection
to their normal automatic ATWS mitigation capability.
III. Discussion
Pursuant to 10 CFR 50.12, the Commission may, upon application by
any interested person or upon its own initiative, grant exemption from
the requirements of 10 CFR part 50 when: (1) the exemptions are
authorized by law, (2) will not present an undue risk to public health
or safety, (3) are consistent with the common defense and security; and
(4) when special circumstances are present, as defined in 10 CFR
50.12(a)(2). This exemption would allow Constellation to temporarily
disable the ARI, and the automatic activation of the SLCS and
recirculation pumps at Limerick so that digital upgrades can be made
leading up to the refueling outages of each unit.
A. The Exemption Is Authorized by Law
The Atomic Energy Act of 1954, as amended, does not require any
specific systems to reduce the risk from ATWS events. These systems are
required by NRC regulation. The intent of the regulations requires
systems to mitigate the ATWS conditions, should they occur. The NRC
staff has determined that granting the exemption will not result in a
violation of the Atomic Energy Act of 1954, as amended, NRC
regulations, or any other laws. Therefore, the requested exemption is
authorized by law.
B. The Exemption Presents no Undue Risk to Public Health and Safety
The NRC requires that an exemption demonstrate that it does not
present undue risk to public health and safety if it is granted.
Constellation provided an analysis that with the proposed systems
offline, the lower power limit, the manual activation of the SLCS and
the recirculation runback pumps, that the disabling of the ATWS
mitigation measures will not present undue risk to public health and
safety. The disabling of automatic ATWS mitigation systems for 30-days
potentially increases the severity of an ATWS event should it occur
within the window. An ATWS that is not successfully mitigated could
result in core damage due to excessive heat generation. ATWS events are
unlikely events that are expected to occur once or more during an
operating reactor's service life. The proposed changes to the reactor
systems do not change the likelihood of an ATWS event occurring. The
consequences of an ATWS can vary from a minor event that can be
addressed with the available protection systems, to more severe that
require more significant measures leading to a sudden shutting down of
a nuclear reactor, if necessary to protect the core from damage.
The proposed ATWS mitigation strategies and TS limits presented by
the licensee in the analysis in its LAR in
[[Page 89054]]
attachment 4 (propriety) and attachment 5 (non-proprietary) demonstrate
an effective strategy to mitigate the potential severity increase
caused by disabling some of the automatic functions of the reactor
protection system so that there is no net increase in the consequences
of an ATWS during the 30-day RRCS demolition period. The NRC staff
verified in the SE to the LAR that the analysis demonstrates that the
consequences of the ATWS are not increased with the associated
operational constraints included in the temporary modifications to the
limiting conditions for operation (LCOs) proposed in the associated LAR
to this exemption during the 30-day RRCS demolition period. Based on a
review of the licensee's analysis as documented in the SE to the
associated LAR to this exemption, the NRC staff has determined that the
requested temporary exemption, with the licensee's compliance with the
TS limiting conditions of operation requested by the licensee in the
LAR, presents no undue risk to public health and safety.
C. The Exemption Is Consistent With the Common Defense and Security
The requested exemption does not change safeguards and security
programs at Limerick. Constellation stated those programs will remain
in full effect during the 30-day RRCS demolition period exemption time
periods in calendar year 2027 for Unit 2 and in calendar year 2026 for
Unit 1. Therefore, the NRC staff finds that the action is consistent
with the common defense and security.
D. Special Circumstances
Pursuant to 10 CFR 50.12(a)(2)(ii), special circumstances are
present when 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 50.62 is that there are systems
available to operators to sufficiently mitigate the consequences of an
ATWS event, that are reliable, independent and diverse from the reactor
trip system. This is made clear in 49 FR 26040 as it states ``The
equipment required by this amendment (10 CFR 50.62(c)) is for the
purpose of reducing the probability of unacceptable consequences
following anticipated operational occurrences.'' The systems that are
required by 10 CFR 50.62 at BWRs are an alternative rod insertion
system, automatic SLCS, and automatic reactor coolant recirculation
pump trip system.
In 49 FR 26041, the Commission provided that some operating nuclear
power plants licensed to operate prior to August 22, 1969, may be
granted a permanent exemption from these requirements if they can
demonstrate that their risk from an ATWS is sufficiently low. The
Commission provided guidance for the factors that it determined to be
important to this such as, power level, unique design features that
could prevent or mitigate the consequences of an ATWS, or the remaining
plant lifetime. The Commission has granted these exemptions for plants
licensed to operate prior to 1969 based on the finding that the risk
from an ATWS is sufficiently low and therefore was not necessary to
achieve the underlying purpose of the rule for Haddam Neck (55 FR
10124) and Yankee Nuclear Power Station (53 FR 20704). While Limerick
Units 1 and 2 were licensed to operate after August 22, 1969, they are
seeking a temporary, not a permanent exemption from these requirements.
The NRC staff notes that this 30-day RRCS demolition period is
temporary in nature, one time per unit, and that the resulting RRCS
modifications to upgraded, digital systems will restore permanent, full
compliance with 10 CFR 50.62(c)(3)-(5) afterwards. This temporary
nature of the exemption aligns with the factor the Commission
considered to be important to grant a permanent exemption of ``the
remaining plant lifetime.'' In addition, the licensee has proposed in
the associated LAR to impose operational controls including
restrictions on the power level of the plant during the 30-day RRCS
demolition period, which in part is used by the licensee in its
analysis to demonstrate that there is no net increase in the severity
of an ATWS. This aligns with the factor of ``power level'' identified
by the Commission as an important factor in granting such an exemption
from the ATWS rules because the power level of Limerick Units 1 and 2
will be limited by the plant's TS during their respective 30-day RRCS
demolition period. Finally, while the licensee has not identified any
unique design features at Limerick Units 1 and 2, it has proposed
unique limiting conditions of operations such as reactor power less
than or equal to 90% RTP, all 14 SRVs operable, and suppression pool
water level greater than or equal to 23 feet. If suppression pool water
level is less than 23 feet, but greater than 22 feet, reactor power
must be reduced to less than 87%. If one SRV becomes out of service
reactor power must be further reduced to less than or equal to 84% RTP.
If two SRVs become inoperable or suppression pool water level drops
below 22 feet then LCO 3.3.4.1 would apply, and the licensee would have
one hour to restore at least one ATWS Recirculation Pump trip system to
operable status within one hour or place the plant in Startup Mode
within the next six hours as required by Limerick TS Action 3.3.4.1.e.
The licensee has demonstrated in its analysis that by implementing
these limiting conditions for operations, results in no net increase in
the severity of an ATWS event. Finally, while the rule requires
automatic systems, the licensee has demonstrated that the relevant
human factors can sufficiently mitigate an ATWS event in the analysis,
as documented by NRC staff in the SE to the associated LAR. The NRC
staff finds that the relevant human factors are appropriate for a
temporary exemption from the requirement for automatic systems because
the licensee has demonstrated that the temporary limiting conditions
for operation provide sufficient time margin in the event of an ATWS
for manual actuation of these systems to provide the same level of ATWS
mitigation as the automatic systems required by 10 CFR 50.62(c)(3)-(5),
as evaluated by NRC staff in the SE to the LAR associated with this
exemption. Therefore, the NRC staff finds that the risk of an ATWS is
sufficiently low in support of this temporary exemption request, using
the factors the Commission identified for certain nuclear power plants,
not including Limerick Units 1 and 2, to be granted permanent
exemptions from the ATWS requirements in 10 CFR 50.62(c).
Specific to the application of the rule to Limerick, NRC staff
notes that the Limerick updated final safety analysis report (UFSAR)
and Tech Spec Bases provides specific descriptions of each system. As
described in the UFSAR Section 4.6.1.2.5.4 for Limerick, the purpose of
the alternative rod insertion system as required by 10 CFR 50.62(c)(3)
is to provide independent solenoid valves to bleed air from the scram
valve pilot air header on low water level or high dome pressure in the
reactor pressure vessel when detected by the RRCS to increase the
reliability of control rod insertion. As described in the UFSAR Section
9.3.5 and TS 3/4.1.5 and associated TS basis for Limerick, the purpose
of the automatic SLCS as required by 10 CFR 50.62(c)(4) is to provide a
backup capability for bringing the reactor from full power to a cold,
Xenon-free shutdown, assuming that the withdrawn control rods remain
fixed in the rated power pattern. As described in
[[Page 89055]]
the UFSAR Section 7.1 and 7.6 and TS 3/4.3.4 and associated TS basis
for Limerick, the purpose of the automatic reactor coolant
recirculation pump trip system as required by 10 CFR 50.62(c)(5) is to
provide a means of limiting the consequences of the unlikely occurrence
of a failure to scram during an anticipated transient.
The NRC staff notes that for 10 CFR 50.62(c)(3), the specific
application of the rule over these temporary 30-day exemption periods
is not necessary to achieve the purpose as stated in Limerick's UFSAR
section 4.6.1.2.5.4 here because the compensatory actions to manually
start the SLCS will provide the required negative reactivity to
mitigate the ATWS. For 10 CFR 50.62(c)(4)-(5), the NRC staff notes that
the licensee has demonstrated that the reactor operator's manual
actuation of these systems will be able to provide the same level of
ATWS mitigation as the automatic systems during the 30-day RRCS
demolition period with the associated limiting conditions for
operation, as evaluated by NRC staff in Section 3.4 ``Walkthroughs'' in
its SE to the LAR associated with this exemption. Therefore, the
specific application for automatic actuation of the systems required by
the rule over these temporary 30-day exemption periods is not necessary
to achieve the purposes as stated in Limerick's UFSAR sections 9.3.5,
and TS 3/4.1.5 for 10 CFR 50.62(c)(4) and as stated in Limerick's UFSAR
Section 7.1, 7.6, and TS 3/4.3.4 for 10 CFR 50.62(c)(5).
Application of 10 CFR 50.62(c)(3)-(5) during 30-day RRCS demolition
period is not necessary to achieve the underlying purpose of the rule
as Constellation stated that since the provided analysis shows that
when the operational constraints of the lower power limit, a higher
number of operable safety relief valves, an additional non-credited
automatic action (recirculation pump runback), and manual activation of
the SLCS system within a 5-minute time frame, an ATWS condition can be
successfully mitigated using existing procedures. The NRC staff's
independent review of the analysis provided that the comparable level
of ATWS mitigation protection to the required systems in 10 CFR
50.62(c)(3)-(5) can be achieved with these proposed operational
constraints and that the mitigation measures provide sufficient time
margin for an operator to respond to an ATWS event in place of the
required automatic systems for the limited period of the 30-day RRCS
demolition period. Therefore, the underlying purpose of 10 CFR
50.62(c)(3)-(5), including the specific underlying purposes of each
system as described in the Limerick UFSAR and Tech Spec Bases, are
achieved by the licensee's implementation of additional ATWS mitigation
strategies identified in the LAR associated with this exemption and
compliance with the TS limiting conditions of operations proposed in
LAR while the licensee turns off the ACI, automatic SLCS, and automatic
RTP during the 30-day RRCS demolition period. Accordingly, compliance
with the specific requirements of 10 CFR 50.62 is not necessary during
the proposed 30-day RRCS demolition period to achieve the underlying
purpose of the rule. The NRC staff finds that special circumstances are
present pursuant to 10 CFR 50.12(a)(2)(ii).
Constellation also proposed that 10 CFR 50.12(a)(2)(iv) and 10 CFR
50.12(a)(2)(vi) as additional special circumstances that are applicable
to the exemption request. The NRC staff has considered their
applicability but found that the circumstances discussed above in 10
CFR 50.12(a)(2)(ii) were adequate to address the necessity of special
circumstances for the exemption request.
E. Environmental Considerations
The NRC's approval of the exemption to 10 CFR 50.62(c)(3), (c)(4),
and (c)(5) belongs to a category of actions that the NRC, by rule or
regulation, has declared to be a categorical exclusion, after first
finding that the category of actions does not individually or
cumulatively have a significant effect on the human environment.
Specifically, the exemption is categorically excluded from further
environmental analysis under 10 CFR 51.22(c)(9).
Under 10 CFR 51.22(c)(9), the issuance of an amendment to a license
for a reactor under part 50 or part 52 that changes a requirement or
issuance of an exemption from the requirement of any regulation of 10
CFR is a categorical exclusion provided that:
The proposed action involves the exemption from a
requirement for the use of a facility component located within the
restricted area, as defined in 10 CFR part 20;
The exemption involves no significant hazards
consideration. The basis for the NRC staff's determination is discussed
in the no significant hazards consideration published in the Federal
Register on October 27, 2023 (88 FR 73883);
There is no significant change in the types or significant
increase in the amounts of any effluents that may be released offsite.
There are no additional quantities nor changes in effluents proposed to
be released based on the proposed action;
There is no significant increase in individual or
cumulative public or occupational radiation exposure. All manual
actions are proposed to be conducted from the main control room and no
local actions are required based on information provided by
Constellation in its letter dated August 16, 2023 (ADAMS Accession No.
ML23228A094). The main control room is shielded and staffed 24 hours a
day under normal circumstances;
Therefore, NRC staff has determined that these exemptions are
categorically excluded from environmental review pursuant to 10 CFR
51.22(c)(9), and therefore no environmental assessment or environmental
impact statement needs to be prepared in connection with the proposed
exemption request.
IV. Conclusions
Accordingly, the NRC has determined that, pursuant to 10 CFR 50.12,
the exemption is authorized by law, will not present an undue risk to
public health and safety, and is consistent with the common defense and
security. Special circumstances are also present at Limerick to justify
the exemption. Therefore, the NRC hereby grants Constellation
exemptions from all requirements for ARI capability under section 10
CFR 50.62(c)(3) and only from the automatic response capability of 10
CFR 50.62(c)(4) for SLCS and 10 CFR 50.62(c)(5) for RPT for a period of
30-days prior to the 2027 refueling outage for Unit 2 and the 2026
refueling outage for Unit 1 (also referred to by Constellation as the
30-day RRCS demolition period) while operating each respective Unit in
accordance with the TS limiting conditions for operation and the
additional ATWS mitigation strategies requested in the associated LAR
to this exemption request dated February 17, 2023, as supplemented by
letters dated July 21, 2023, July 31, 2023, August 16, 2023, and May
28, 2024. 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 Constellation a one-time
exemption from 10 CFR part 50, section 50.62(c)(3) and only the
automatic response capability of sections 50.62(c)(4) and 50.62(c)(5)
during the 30-day RRCS demolition period to support the installation of
the digital upgrade at Limerick.
Dated: November 5, 2024.
[[Page 89056]]
For the Nuclear Regulatory Commission.
Bo Pham,
Director, Division of Operating Reactor Licensing, Office of Nuclear
Reactor Regulation.
[FR Doc. 2024-26075 Filed 11-8-24; 8:45 am]
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