[Federal Register Volume 87, Number 209 (Monday, October 31, 2022)]
[Notices]
[Pages 65618-65622]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-23569]
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NUCLEAR REGULATORY COMMISSION
[Docket No. 50-483; NRC-2022-0139]
Union Electric Company, dba Ameren Missouri, Callaway Plant; Unit
No. 1
AGENCY: Nuclear Regulatory Commission.
ACTION: Exemption; issuance.
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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is granting
exemptions from certain portions of the acceptance criteria for
emergency core cooling, and the general design criteria for emergency
core cooling, containment heat removal, and atmosphere cleanup to allow
the use of a risk-informed analysis to evaluate the effects of debris
in containment following a loss-of-coolant accident for the Callaway
Plant, Unit No. 1 (Callaway) located in Callaway County, Missouri. The
exemptions are in response to a request dated March 31, 2021, from
Union Electric Company, doing business as Ameren Missouri (the
licensee) related to the licensee's proposed approach to resolve a
generic safety concern for pressurized water reactors associated with
potential clogging of emergency core cooling and containment spray
system strainers during certain design basis events.
DATES: The exemptions were issued on October 21, 2022.
ADDRESSES: Please refer to Docket ID NRC-2022-0139 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-2022-0139. 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]. The request for the exemptions was
submitted by letter dated March 31, 2021, as supplemented by letters
dated May 27, 2021, July 22, 2021, August 23, 2021, October 7, 2021,
January 27, 2022, March 8, 2022, May 26, 2022, and September 8, 2022.
For the convenience of the reader, instructions about obtaining
materials referenced in 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,
[[Page 65619]]
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 8:00 a.m. and 4:00 p.m. Eastern
Time (ET), Monday through Friday, except Federal holidays.
FOR FURTHER INFORMATION CONTACT: Mahesh Chawla, Office of Nuclear
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001, telephone: 301-415-8371, email: [email protected].
I. 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 ADAMS accession No.
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Ameren Missouri, letter to U.S. Nuclear Regulatory ML21090A184 (Package).
Commission, ``Callaway Plant, Unit 1, Request for License
Amendment and Regulatory Exemptions for a Risk-Informed
Approach to Address GSI-191 and Respond to GL 2004-02
(LDCN 19-0014),'' dated March 31, 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory ML21147A222.
Commission, ``Callaway Plant, Unit 1, Supplement to
Request for Licence Amendment and Regulatory Exemptions
for a Risk-Informed Approach to Address GSI-191 and
Respond to GL 2004-02 (LDCN 19-0014),'' dated May 27, 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory ML21203A192 (Package).
Commission, ``Callaway Plant, Unit 1, Supplement to
Request for License Amendment and Regulatory Exemptions
for a Risk-Informed Approach to Address GSI-191 and
Respond to GL-2004-02 (LDCN 19-0014),'' dated July 22,
2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory ML21237A135 (Package).
Commission, ``Callaway Plant, Unit 1, Transmittal of
Documents Identified from NRC Audit of License Amendment
Request Regarding Risk-Informed approach to Closure of
Generic Safety Issue 191 (EPID L-2021-LLA-0059),'' dated
August 23, 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory ML21280A378 (Package).
Commission, ``Callaway Plant, Unit 1, Third Supplement to
Request for License Amendment and Regulatory Exemptions
for a Risk-Informed Approach to Address GSI-191 and
Respond to GL-2004-02 (LDCN 19-0014) (EPID L-2021-LLA-0059
and EPID L-2021-LLE-0021),'' dated October 7, 2021.
Ameren Missouri, letter to U.S. Nuclear Regulatory ML22027A804 (Package).
Commission, ``Callaway Plant, Unit 1, Fourth Supplement to
Request for License Amendment and Regulatory Exemptions
for a Risk-Informed Approach to Address GSI-191 and
Respond to GL-2004-02 (LDCN 19-0014) (EPID L-2021-LLA-0059
and EPID L-2021-LLE-0021),'' dated January 27, 2022.
Ameren Missouri, letter to U.S. Nuclear Regulatory ML22068A027 (Package).
Commission, ``Callaway Plant, Unit 1, Fifth (Post-Audit)
Supplement to Request for License Amendment and Regulatory
Exemptions for a Risk-Informed Approach to Address GSI-191
and Respond to GL 2004-02 (LDCN 19-0014) (EPID L-2021-LLA-
0059 and EPID L-2021-LLE-0021),'' dated March 8, 2022.
Ameren Missouri, letter to U.S. Nuclear Regulatory ML22146A337 (Package).
Commission, ``Callaway Plant, Unit 1, Response to Request
for Additional Information Regarding Request for License
Amendment and Regulatory Exemptions for Risk-Informed
Approach to Address GSI-191 and Respond to Generic Letter
2004-02 (LDCN 19-0014) (EPID L-2021-LLA-0059 and EPID L-
2021-LLE-0021),'' dated May 26, 2022.
Ameren Missouri, letter to U.S. Nuclear Regulatory ML22251A343.
Commission, ``Callaway Plant, Unit 1, Correction of Text
Contained in Enclosures Provided with Supplements to
Request for License Amendment and Regulatory Exemptions
for a Risk-Informed Approach to Address GSI-191 and
Respond to Generic Letter 2004-02 (LDCN 19-0014) (EPID L-
2021-LLA-0059 and EPID L-2021-LLE-0021),'' dated September
8, 2022.
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SUPPLEMENTARY INFORMATION: The text of the exemption is attached.
Dated: October 25, 2022.
For the Nuclear Regulatory Commission.
Mahesh L. Chawla,
Project Manager, Plant Licensing Branch IV, Division of Operating
Reactor Licensing, Office of Nuclear Reactor Regulation.
Attachment--Exemption
Nuclear Regulatory Commission
Docket No. 50-483
Union Electric Company, Callaway Plant, Unit No. 1, Exemptions
I. Background
Union Electric Company, doing business as (dba) as Ameren
Missouri (the licensee), is the holder of Renewed Facility Operating
License No. NPF-30, which authorizes operation of the Callaway
Plant, Unit No. 1 (Callaway). The license provides, among other
things, that the facility is subject to all rules, regulations, and
orders of the U.S. Nuclear Regulatory Commission (NRC) now or
hereafter in effect. The facility consists of a pressurized-water
reactor (PWR) located in Callaway County, Missouri.
In 1996, the NRC identified Generic Safety Issue (GSI)-191,
``Assessment of Debris Accumulation on PWR Sump Performance,''
associated with the effects of debris accumulation on PWR sump
performance during design-basis accidents. As part of the actions to
resolve GSI-191, the NRC issued Generic Letter (GL) 2004-02,
``Potential Impact of Debris Blockage on Emergency Recirculation
during Design Basis Accidents at Pressurized-Water Reactors,'' dated
September 13, 2004 (ML042360586), to holders of operating licenses
for PWRs. In GL 2004-02, the NRC staff requested that licensees
perform an evaluation of their emergency core cooling systems (ECCS)
and containment spray system (CSS) recirculation functions
considering the potential for debris-laden coolant to be circulated
by the ECCS and the CSS after a loss-of-coolant accident (LOCA) or
high energy line break inside containment and, if appropriate, take
additional actions to ensure system function. GL 2004-02 required
that licensees provide a written response to the NRC, pursuant to
Title 10 of the Code of Federal Regulations (10 CFR) Section
50.54(f), describing the results of their evaluation and any
modifications made, or planned, to ensure the ECCS and CSS remain
functional.
II. Request/Action
By application dated March 31, 2021, (Agencywide Documents
Access and Management System (ADAMS) Accession No. ML21090A184), as
supplemented by letters dated May 27, 2021, July 22, 2021, August
23, 2021, October 7, 2021, January 27, 2022, March 8, 2022, May 26,
2022, and September 8, 2022 (ML21147A222, ML21203A192, ML21237A135,
ML21280A378, ML22027A804, ML22068A027, ML22146A337, and ML22251A343,
respectively), the licensee, pursuant to 10 CFR 50.12, ``Specific
exemptions,'' requested exemptions from certain requirements of 10
CFR 50.46, ``Acceptance criteria for emergency core cooling systems
for light-water nuclear power reactors,'' and 10 CFR part 50,
Appendix A, General Design Criterion (GDC) 35, ``Emergency core
cooling''; GDC 38, ``Containment heat removal''; and GDC 41,
``Containment atmosphere cleanup,'' to allow use of a risk-informed
methodology instead of the traditional deterministic methodology,
[[Page 65620]]
to resolve the concerns associated with GSI-191, and respond to GL
2004-02 for Callaway.
Specifically, the licensee requested exemptions from 10 CFR
50.46(a)(1)(i), which, in part, requires the ECCS cooling
performance to be calculated in accordance with an acceptable
evaluation model as described in 10 CFR 50.46(a)(1), and for
postulated LOCAs of different sizes, locations and other properties
sufficient to provide assurance that the most severe LOCAs are
evaluated. The NRC staff interprets the Section 50.46(a)(1)
requirement to calculate ECCS performance for ``other properties''
as requiring licensees to consider the impacts of debris generation
and transport in containment. The most significant form of debris in
nuclear power reactor containments is piping and component
insulation that can become debris during LOCAs, transport and
accumulate in the sumps, and clog the sumps strainers, thus creating
resistance to coolant flow. Fibrous debris from this insulation can
also enter the reactor core and directly impede heat transfer from
the fuel to the coolant.
The approval of a risk-informed methodology would require
exemptions from 10 CFR 50.46(a)(1)(i) and GDCs 35, 38, and 41
because the NRC has interpreted these regulations as requiring a
deterministic approach and bounding calculation to show compliance
with ECCS and CSS performance criteria in 10 CFR 50.46(b) and GDCs
35, 38, and 41. Issuance of exemptions is an appropriate means to
grant relief from the use of a deterministic approach to show
compliance with these requirements.
The licensee's 10 CFR 50.46 deterministic analysis considered
the debris in containment and demonstrated that the debris loading
could prevent acceptable ECCS and CSS operation and core cooling for
certain pipe ruptures. Based on its analysis, the licensee concluded
that the amount of debris in the Callaway containment would need to
be reduced to demonstrate compliance with 10 CFR 50.46 criteria
using a deterministic analysis for certain large-break LOCA sizes
because, for those breaks, the plant-specific testing threshold for
generation and transport of debris was exceeded.
Additionally, the licensee's deterministic in-vessel analysis
was limited to breaks that could generate and transport to the
strainers fibrous debris amounts in excess of the plant-specific
tested debris limit for the strainers. This value was chosen because
it also represents the deterministic limit for strainer failure for
pipe breaks. Therefore, any break that generates and transports more
than the amount of fibrous debris bounded by plant testing is
already assumed to cause strainer failure and increase core damage
frequency. Because these large breaks are already assumed to
contribute to plant risk because of strainer failure, there is no
need to evaluate them for risk contribution due to in-vessel
failure. Other debris types were bounded by the strainer evaluation
and are not critical to the in-vessel analysis. Therefore, all cases
where core damage might occur due to debris arriving at the core are
already covered by scenarios that cause strainer failure and do not
need to be counted as additional increases in risk.
The licensee requested exemptions from the requirement to use a
deterministic analysis for specific scenarios of LOCA breaks
producing and transporting debris in excess of the plant-specific
tested debris limits. Since it determined that the probability of
consequences from debris effects is very low, the licensee requested
exemptions to allow the use of a risk-informed analysis to show
adequate assurance of ECCS and CSS functionality, in accordance with
the criteria in Regulatory Guide (RG) 1.174, Revision 3, ``An
Approach for Using Probabilistic Risk Assessment in Risk-Informed
Decisions on Plant-Specific Changes to the Licensing Basis,'' dated
January 2018 (ML17317A256). RG 1.174 was developed in consideration
of the Commission's Policy Statements on safety goals \1\ and the
use of probabilistic risk assessment methods in nuclear regulatory
activities.\2\ Therefore, RG 1.174 provides an acceptable method for
licensees and NRC staff to use in assessing the impact of licensing
basis changes when the licensee chooses to use risk information.
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\1\ Commission's Safety Goal Policy Statement, ``Safety Goals
for the Operations of Nuclear Power Plants; Policy Statement,''
published in the Federal Register on August 4, 1986 (51 FR 28044),
as corrected, and republished, on August 21, 1986 (51 FR 30028).
\2\ Use of Probabilistic Risk Assessment Methods in Nuclear
Activities; Final Policy Statement,'' August 16, 1995 (60 FR 42622).
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The requirements in GDC 35 require, in part, that the ECCS
safety system functions adequately to transfer heat from the reactor
core following a LOCA and in the presence of a worst single failure,
at a rate such that (a) fuel and clad damage that could interfere
with continued effective core cooling is prevented and (b) clad
metal-water reactor is limited to negligible amounts. The licensee
stated in its application dated March 31, 2021, that the function of
the ECCS emergency sump is assumed to fail for scenarios where
debris exceeds the amount determined in acceptable plant-specific
testing. Failure of the sump and strainers results in loss of
cooling to the core. The licensee requested exemptions from the
requirements of GDC 35, which requires the use of a deterministic
approach, for those LOCA breaks that exceed the plant-specific
testing debris threshold. The licensee requested exemptions from the
deterministic requirements of GDC 35, to allow the use of a risk-
informed analysis, in accordance with the criteria in RG 1.174, to
show that the risk from debris effects is very low.
The requirements in GDC 38 require containment heat removal,
rapid reduction of containment pressure and temperature, and
maintenance of pressure and temperature at an acceptably low level
following a LOCA, and in the presence of a single failure, to
preserve containment function. The licensee proposed that exemptions
be granted from the requirements in GDC 38 that specify the use of a
deterministic approach. The request applies only to those LOCA
breaks that exceed the plant-specific testing debris threshold.
Current Callaway design basis calculations are based on the
containment cooling system (containment fan coolers) functioning in
conjunction with the CSS and ECCS, both of which can be affected by
debris. Using deterministic assumptions, the licensee's analysis and
testing does not assure that the emergency sump strainers will be
available to support the CSS and ECCS function considering the
effects of debris produced by those breaks that can generate and
transport debris amounts greater than the plant-specific testing
threshold. The licensee requested exemptions from the deterministic
requirements of GDC 38 to allow the use of a risk-informed analysis,
in accordance with the criteria in RG 1.174, to show that the risk
from debris effects is very low.
The requirements in GDC 41, require, in part, containment
atmosphere cleanup to control substances that may be released into
the reactor containment, to reduce the concentration and quality of
fission products released to the environment following postulated
accidents, and to control the concentration of hydrogen or oxygen
and other substances in the containment atmosphere following
postulated accidents, assuming a single failure. The licensee stated
that using deterministic assumptions, its analysis and testing
cannot demonstrate that the emergency sump strainers will be
available to support the CSS function considering the effects of
debris produced and transported by breaks not bounded by acceptable
plant-specific testing. The licensee requested exemptions from the
deterministic requirements of GDC 41 to allow the use of a risk-
informed analysis, in accordance with the criteria in RG 1.174, to
show that the risk from debris effects is very low.
III. Discussion
Pursuant to 10 CFR 50.12, 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, and are consistent with the common defense
and security; and (2) when special circumstances are present. Under
10 CFR 50.12(a)(2)(ii), special circumstances are present when
``[a]pplication of the regulation in the particular circumstances
would not serve the underlying purpose of the rule or is not
necessary to achieve the underlying purpose of the rule.''
The licensee proposed to use a risk-informed methodology instead
of a deterministic approach to account for the effects of debris in
containment for portions of the LOCA analysis applicable to breaks
that exceed the Callaway plant-specific debris testing threshold.
The licensee's methodology, termed Risk over Deterministic, or
RoverD, divides the loss of core cooling design-basis analysis into
two portions: the ``deterministic analysis'' and the ``risk-informed
analysis.'' The risk-informed analysis is used by the licensee for
breaks that generate and transport debris exceeding the plant-
specific testing threshold. These breaks result in fibrous
[[Page 65621]]
debris estimated to arrive in the ECCS sump post-LOCA in amounts
that are equal to or greater than the amount of fiber used in
acceptable strainer testing. The acceptable limit was determined
using testing methods intended to determine the maximum ECCS
strainer head loss for the tested condition.
Also, the licensee evaluated the in-core aspects of fibrous
debris to prevent adequate fuel cooling. The licensee found that for
in-vessel effects, all breaks that generate and transport fibrous
debris amounts less than the strainer acceptance criterion can be
evaluated deterministically and shown to have acceptable outcomes.
Therefore, the in-vessel effects do not contribute to changes in
core damage frequency. For ECCS and CSS analyses other than the
postulated large-break LOCAs that generate less than the strainer
acceptance limit, the licensee applied a deterministic methodology.
If the exemptions were granted for these postulated breaks, the
requirement to use a deterministic methodology for all other
postulated LOCA breaks would continue to apply.
A. The Exemptions Are Authorized by Law
The exemptions would allow the use of a risk-informed
methodology to show compliance with 10 CFR 50.46(a)(1)(i), and GDCs
35, 38, and 41 of Appendix A to 10 CFR part 50, when considering
debris in containment generated and transported by those breaks that
exceed the plant-specific testing threshold. These regulations were
promulgated under and are consistent with the Commission's authority
under Section 161 of the Atomic Energy Act of 1954, as amended.
Because the application of a risk-informed methodology to show
compliance with 10 CFR 50.46, and GDC 35, 38, and 41 of Appendix A
to 10 CFR part 50, would not violate the Atomic Energy Act of 1954,
as amended, or the Commission's regulations, the exemptions are
authorized by law provided all requisite findings are made.
B. The Exemptions Present No Undue Risk to Public Health and Safety
The provisions of 10 CFR 50.46 and GDCs 35, 38, and 41 of
Appendix A to 10 CFR part 50 establish criteria for the emergency
core cooling, containment cooling, and containment atmosphere
cleanup system performance. As part of the amendment request, the
licensee submitted exemption requests to change its design-basis
analysis specified in the Updated Final Safety Analysis Report
(UFSAR) to allow use of risk-informed and deterministic
methodologies to specifically account for the impacts of debris in
containment. The licensee justified its use of the risk-informed
approach by stating that the proposed risk-informed approach meets
the key principles in RG 1.174, Revision 3, in that it is consistent
with defense-in-depth philosophy, maintains sufficient safety
margins, results in a small increase in risk, and is monitored by
the licensee using performance measurement strategies.
Additionally, the licensee stated that the proposed exemptions,
to allow use of the risk-informed method, are consistent with Key
Principle 1 in RG 1.174 that requires a proposed change to the
licensing basis (or amendment) to meet current regulations unless
the change is explicitly related to requested exemptions. The
probabilistic risk analysis results provided by the licensee and
evaluated by the NRC staff in its safety evaluation, showed that the
increase in risk associated with debris generation and transport on
ECCS and CSS function following postulated LOCAs is very small, in
accordance with the criteria in RG 1.174.
The NRC staff concluded that the risk is consistent with the
guidance in RG 1.174 and with the Commission policy statements on
safety goals and the use of probabilistic risk assessment methods in
nuclear regulatory activities; therefore, the requested exemptions
present no undue risk to public health and safety.
C. The Exemptions Are Consistent With the Common Defense and
Security
The requested exemptions would allow the licensee to use a risk-
informed methodology to resolve a generic safety concern for PWRs
associated with potential clogging of the ECCS and CSS strainers
during certain design-basis events. The change is adequately
controlled by safety acceptance criteria and technical specification
requirements and is not related to security issues. Because the
common defense and security is not impacted by the exemptions, the
exemptions are consistent with the common defense and security.
D. Special Circumstances
Under the regulations in 10 CFR 50.12, the Commission may grant
exemptions from the requirements of 10 CFR part 50 provided certain
findings are made; namely, that special circumstances are present,
the exemptions present no undue risk to public health and safety,
the exemptions are consistent with the common defense and security,
and the exemptions are authorized by law. The exemptions would allow
the use of a risk-informed methodology to show compliance with 10
CFR 50.46(a)(1)(i), and GDCs 35, 38, and 41 of Appendix A to 10 CFR
part 50, specifically for the analyses of debris in containment
impacting emergency cooling function during postulated large-break
LOCAs that exceed the plant-specific testing threshold.
The licensee requested exemptions citing the special
circumstances criteria of 10 CFR 50.12(a)(2)(ii), because compliance
in the particular circumstances would not serve the underlying
purpose of the rule or is not necessary to achieve the underlying
purpose of the rule. The licensee cited these special circumstances
for all of the requested exemptions.
The licensee stated that an objective of each of the regulations
for which exemptions are proposed is to maintain low risk to the
public health and safety through the adequate functioning of the
ECCS and CSS safety systems. These systems must be supported by
adequate functioning of the containment sumps. The regulations in 10
CFR 50.46(a)(1)(i) and GDCs 35, 38, and 41 of Appendix A to 10 CFR
part 50 are met when the licensee can demonstrate, using a bounding
calculation or other deterministic method that the ECCS and CSS are
capable of functioning during design basis events. The licensee
stated that its risk-informed analysis to show adequate functioning
of ECCS and CSS, considering the impacts of debris during certain
LOCA events, demonstrates that the ECCS and CSS systems will operate
with a high degree of reliability. The licensee stated that special
circumstances exist because the underlying intent of the
regulations, to ensure adequate protection of public health and
safety is met when applying a risk-informed approach to address GSI-
191 and responding to GL 2004-02. Further, it states that the risk-
informed approach is consistent with RG 1.174 and supports operation
of those functions with a high degree of reliability. Thus, the
licensee concludes that the underlying intent of each regulation is
met, and the special circumstances described in 10 CFR
50.12(a)(2)(ii) apply to each of the exemptions proposed by the
licensee.
The NRC staff evaluated the licensee's application, as
supplemented and discussed the details of its evaluation of the
risk-informed approach in an NRC safety evaluation available under
ADAMS Accession No. ML22220A132. Although 10 CFR 50.46(a)(1)
requires a deterministic approach, the GDCs do not specify that a
risk-informed methodology may not be used to show compliance;
however, because the NRC has interpreted each of these regulations
as requiring a deterministic approach, exemptions are an appropriate
means to grant the licensee relief to use an alternative approach.
The underlying purpose of each regulation is to protect public
health and safety in the event of a LOCA by establishing criteria
for emergency core cooling, containment cooling and containment
atmosphere cleanup system performance. In its safety evaluation, the
NRC staff concluded, in part, that the licensee adequately
demonstrated that the change in risk attributable to debris that
exceed the plant specific threshold is very small and meets the risk
acceptance guidelines in RG 1.174. The NRC staff also concluded that
the analysis is consistent with defense-in-depth philosophy,
maintains sufficient safety margins, results in a small increase in
risk, and is monitored by the licensee using performance measurement
strategies. Therefore, the licensee's use of the risk-informed
analysis meets the underlying requirements of 10 CFR 50.46 and GDCs
35, 38, and 41 of Appendix A to 10 CFR part 50, to ensure that a
licensee demonstrates that the ECCS and CSS will provide adequate
cooling for the reactor core and containment and provide containment
atmosphere cleanup during design-basis accidents considering the
impacts of debris, since it meets the guidelines in RG 1.174.
Based on the above, the NRC staff concludes that special
circumstances under 10 CFR 50.12(a)(2)(ii) exist because compliance
with the deterministic requirements of 10 CFR 50.46(a)(1)(i), and
GDCs 35, 38, and 41 of Appendix A to 10 CFR part 50 is not necessary
to achieve the underlying purpose of each rule.
E. Supplemental Information
For more technical details, refer to the SE associated with
these exemptions under
[[Page 65622]]
ADAMS Accession No. ML22220A130 (enclosure 2).
F. Environmental Considerations
Pursuant to 10 CFR 51.21, ``Criteria for and identification of
licensing and regulatory actions requiring environmental
assessments,'' the NRC has prepared an environmental assessment (EA)
and finding of no significant impact (FONSI) summarizing the
findings of its review of the environmental impacts of the proposed
action under the National Environmental Policy Act (NEPA). The NRC
staff determined that special circumstances under 10 CFR 51.21 exist
to warrant preparation of an EA and FONSI because Callaway is
proposing a risk-informed approach to resolve GSI-191 as recognized
in Staff Requirement Memorandum SECY-12-0093, ``Closure Options for
Generic Safety Issue--191, Assessment of Debris Accumulation on
Pressurized-Water Reactor Sump Performance,'' dated December 14,
2012 (ML12349A378). Because this action uses risk information to
justify exemptions from deterministic regulations, the NRC staff
considered preparations of an EA and FONSI to be a prudent course of
action that would further the purposes of NEPA. Based on its review,
the NRC concluded that an environmental impact statement is not
required and that the proposed action will have no significant
impact on the environment.
The NRC published a final EA and FONSI on the proposed action in
the Federal Register on August 29, 2022 (87 FR 52816).
IV. Conclusions
Accordingly, the Commission has determined that, pursuant to 10
CFR 50.12, exemptions are authorized by law, will not present an
undue risk to the public health and safety, are consistent with the
common defense and security, and special circumstances are present
pursuant to 10 CFR 50.12(a)(2)(ii). Therefore, the NRC hereby grants
Union Electric Company, dba Ameren Missouri, one-time exemptions
from 10 CFR 50.46(a)(1), and 10 CFR part 50, Appendix A, GDCs 35,
38, and 41 to allow the use of a risk-informed methodology in lieu
of a deterministic methodology to show conformance with the ECCS and
CSS performance criteria accounting for debris in containment for
those breaks that exceed the plant-specific Callaway testing
threshold.
Dated at Rockville, Maryland, this 21st day of October 2022.
For the Nuclear Regulatory Commission.
Gregory F. Suber,
Deputy Director, Division of Operating Reactor Licensing, Office of
Nuclear Reactor Regulation.
[FR Doc. 2022-23569 Filed 10-28-22; 8:45 am]
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