Constellation Energy Generation LLC; Limerick Generating Station, Units 1 and 2; Exemption, 89052-89056 [2024-26075]

Agencies

• NUCLEAR REGULATORY COMMISSION

[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.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    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]
BILLING CODE 7590-01-P