ML22292A035

Issuance of Amendment No. 246 Secondary Containment and the Fuel Building Railroad Airlock (EPID L-2022- LLA-0055)

ML22292A035
Person / Time
Site:	Clinton
Issue date:	11/10/2022
From:	Joel Wiebe NRC/NRR/DORL/LPL3
To:	Rhoades D Constellation Energy Generation
Wiebe J, NRR/DORL/LPL3
References
EPID L-2022-LLA-0055
Download: ML22292A035 (1)

Text

November 10, 2022 Mr. David P. Rhoades Senior Vice President Constellation Energy Generation, LLC President and Chief Nuclear Officer Constellation Nuclear 4300 Winfield Road Warrenville, IL 60555-4012

SUBJECT:

CLINTON POWER STATION, UNIT NO. 1 - ISSUANCE OF AMENDMENT NO. 246 RE: SECONDARY CONTAINMENT AND THE FUEL BUILDING RAILROAD AIRLOCK (EPID L-2022-LLA-0055)

Dear Mr. Rhoades:

The U.S. Nuclear Regulatory Commission has issued the enclosed Amendment No. 246 to Facility Operating License No. NPF-62 for the Clinton Power Station, Unit No. 1 (CPS). The amendment is in response to your application dated April 7, 2022, as supplemented by letter dated July 25, 2022.

The amendment revises the CPS secondary containment design basis to include the Fuel Building Railroad Airlock (FBRA) and FBRA outer door.

A copy of the Safety Evaluation is also enclosed. A Notice of Issuance will be included in the Commissions next monthly Federal Register notice.

Sincerely,

/RA/

Joel S. Wiebe, Senior Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-461

Enclosures:

1. Amendment No. 246 to NPF-62

2. Safety Evaluation cc: Listserv

CONSTELLATION ENERGY GENERATION, LLC DOCKET NO. 50-461 CLINTON POWER STATION, UNIT NO. 1 AMENDMENT TO FACILITY OPERATING LICENSE Amendment No. 246 License No. NPF-62

1. The U.S. Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment by Constellation Energy Generation, LLC (the licensee), dated April 7, 2022, as supplemented by letter dated July 25, 2022, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance: (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D. The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.

Enclosure 1

2. Accordingly, the license is amended to revise the Clinton Power Station, Unit No. 1, secondary containment design basis to include the Fuel Building Railroad Airlock (FBRA) and FBRA outer door.

3. This license amendment is effective as of its date of issuance and shall be implemented within 60 days of the date of issuance. Implementation of the amendment shall also include revision of the Updated Safety Analysis Report as described in the licensees letter dated April 7, 2022, as supplemented by letter dated July 25, 2022.

FOR THE NUCLEAR REGULATORY COMMISSION Digitally signed by Scott Scott P. Wall P.Date:

Wall 2022.11.10 14:34:19 -05'00' Nancy L. Salgado, Chief Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Facility Operating License and Technical Specifications Date of Issuance: November 10, 2022

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 246 TO FACILITY OPERATING LICENSE NO. NPF-62 CONSTELLATION ENERGY GENERATION, LLC CLINTON POWER STATION, UNIT NO. 1 DOCKET NO. 50-461

1.0 INTRODUCTION

By letter to the U.S. Nuclear Regulatory Commission (NRC, the Commission) dated April 7, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22097A208), as supplemented by letter dated July 25, 2022 (ML22206A191),

Constellation Energy Generation, LLC, the licensee, submitted a license amendment request (LAR) to change the Clinton Power Station (CPS), Unit 1, design basis. Specifically, the licensee requested approval for a change to the Updated Safety Analysis Report (USAR) to support a revision of the CPS secondary containment design basis to include the fuel building railroad airlock (FBRA) and FBRA outer door.

The supplemental letter dated July 25, 2022, provided additional information that clarified the application, did not expand the scope of the application as originally noticed, and did not change the NRC staffs original proposed no significant hazards consideration determination as published in the Federal Register on May 17, 2022 (87 FR 29886).

2.0 REGULATORY EVALUATION

2.1 Secondary Containment Description As described in section 3.2 of the LAR, the secondary containment is a structure that completely encloses the primary containment, except for the upper personnel hatch, and consists of the containment gas control boundary (CGCB), the CGCB extension (i.e., siding within the auxiliary building), the fuel building (not including the railroad airlock), the emergency core cooling system (ECCS) residual heat removal heat exchanger rooms, the ECCS pump rooms, the reactor water cleanup pump room, and the main steam pipe tunnel.

Enclosure 2

The function of the secondary containment is to contain, dilute, and hold up fission products that may leak from primary containment following a design basis accident. The secondary containment boundary is described in CPS USAR, sections 6.2.3.1, 6.2.3.2, 6.2.3.3, and figure 6.2-132 (ML22216A210).

The licensee further explains in its LAR that the only accident that credits the secondary containment is the design basis loss-of-coolant accident (LOCA) described in USAR, section 15.6.5 (ML22216A204). The secondary containment, in conjunction with the operation of the standby gas treatment (SGT) system is designed to limit the total effective dose equivalent (TEDE) within the guidelines of Title 10 of the Code of Federal Regulations (10 CFR) 50.67, Accident Source Term, at the site boundary and low population zone. Also, the design limits the TEDE dose for the control room within the guidelines of 10 CFR 50, appendix A, General Design Criterion (GDC) 19, Control Room.

The licensee also states that the performance objective of the secondary containment is to provide a volume surrounding the primary containment which can capture fission products that might otherwise leak to the environment following a design basis accident. Following the postulated design basis accident, the SGT system functions to achieve and maintain the secondary containment volume at or below a negative pressure of 0.25-inch water gauge.

The licensee states in its LAR that in addition to its function to reduce fission product releases following a design basis LOCA, the secondary containment structure also provides protection for equipment within the fuel building and auxiliary building from the effects of tornado missiles.

Specifically, the secondary containment structure, including the CGCB, is seismic Category I design. All civil structures classified as seismic Category I are designed for the effects of CPS natural phenomena such as tornado, wind loads, external missiles, floods, etc., except for the CGCB. Seismic Category I structures are designed to withstand postulated external missiles, thereby, protecting the systems and components located within. USAR, section 3.5.1.4 (ML22111A196), states that tornadoes are the only natural phenomenon occurring in the vicinity of CPS that can generate missiles, and USAR, section 3.5.1.5, states that based on a review of the nearby industrial, transportation, and military facilities, it can be concluded that there are no potential missiles resulting from accidental explosions in the vicinity of the site.

The licensee states in its LAR that the secondary containment design basis currently does not include the FBRA structure as part of the secondary containment boundary. Rather, the FBRA inner door (i.e., the door that serves as the interface between the fuel building and the FBRA) currently forms part of the secondary containment boundary. The FBRA is a limited leakage structure constructed of structural steel and steel siding that includes the inner door and outer door. The inner door is seismic Category I and is designed to withstand tornado winds and missiles. The FBRA and outer door are capable of maintaining, in conjunction with the SGT system, a negative pressure at or below 0.25-inch water gauge in the secondary containment.

The FBRA and outer door are qualified for seismic Category I loads except for tornado winds and missiles.

2.2 Proposed Change of Licensing Basis Section 2.0 of attachment 1 to the LAR states that during the plant in operation Mode 1, 2, or 3, each time the FBRA inner door is opened to move equipment in and out of the fuel building, the secondary containment is declared inoperable, and Technical Specifications (TS) 3.6.4.1, Secondary Containment, Condition A is entered. Required Action A.1 requires the secondary containment to be restored to operable status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

During the movement of a spent fuel cask, if the fuel cask should be stalled in the FBRA preventing the closure of inner door more than 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, CPS, Unit 1, would be required to commence an orderly shutdown. In the LAR, the licensee proposed a change to allow more flexibility for plant operation to avoid such shutdown.

The proposed change revises the definition of the secondary containment boundary to include the FBRA and maintains secondary containment functional capability including tornado protection function when required. This change adds the FBRA and outer door (i.e., the door between the FBRA and the outside environment) as part of the secondary containment boundary, when the inner door is open and no adverse weather conditions exist.

2.3 Regulatory Requirements and Guidance General Design Condition (GDC) 2 Regulation 10 CFR 50, appendix A, General Design Criteria for Nuclear Power Plants, Criterion 2, Design Bases for Protection Against Natural Phenomena, requires, in part, that structures, systems, and components important to safety be designed to withstand the effects of natural phenomena such as tornadoes without loss of capability to perform their safety functions. Regulatory Guide (RG) 1.117 Tornado Design Classification, Revision 1, dated April 1978 (ML003739346), discusses GDC 2 with respect to tornados and tornado missiles.

RG 1.117 states that equipment used to provide long-term core cooling following a LOCA should be protected to maintain the reactor in a safe shutdown condition.

Regulation 10 CFR 50.67 The alternative source term methodology described in 10 CFR 50.67 has been adopted at CPS using the methodology of RG 1.183, Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors, dated July 2000 (ML003716792). The secondary containment, in conjunction with the operation of the SGT system, is designed to limit the TEDE within the guidelines of 10 CFR 50.67 at the site boundary and low population zone.

3.0 TECHNICAL EVALUATION

The current secondary containment includes the functional capability of (1) reducing fission product releases to limit dose consequences following a LOCA to meet the requirement of 10 CFR 50.67, and (2) designing the structures to withstand the effects of natural phenomena such as tornadoes without loss of capability to perform their safety functions to meet GDC 2.

The proposed licensing basis revises the secondary containment boundary to include FBRA by opening the inner door between the secondary containment and the FBRA. The proposed change presents an impact to the drawdown time testing and maintaining a negative pressure of 0.25-inch water gauge for the revised larger secondary containment volume. In addition, it presents an impact to the tornado missile protection because the FBRA and outer door do not have sufficient capability for tornado wind and missile protection.

Section 3.3 of attachment 1 to the LAR has addressed the safety impact resulting from the proposed change including (1) the periodic drawdown testing, and (2) manual action for FBRA inner door.

3.1 Periodic Drawdown Testing Section 3.3 of attachment 1 to the LAR states that the licensee performed SGT system drawdown testing to ensure the functional capability of the secondary containment being maintained with the inner door open and outer door closed. Periodic drawdown testing of secondary containment is performed in accordance with Surveillance Requirement (SR) 3.6.4.1.4 and SR 3.6.4.1.5.

Specifically, SR 3.6.4.1.4 requires verification that the secondary containment can be drawn down to greater than or equal to 0.25 inch of vacuum water gauge within the time required using one SGT subsystem. The TS Bases state that the required drawdown time is 19 minutes following a LOCA. In addition, SR 3.6.4.1.5 requires verification that the secondary containment can be maintained greater than or equal to 0.25 inch of vacuum water gauge for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> using one SGT subsystem at a flow rate of less than or equal to 4400 cubic feet per minute (cfm). No changes to SRs 3.6.4.1.4 and 3.6.4.1.5 are being made as part of the proposed change to revise the secondary containment design basis to include the volume of the FBRA.

The post LOCA drawdown time of 19 minutes for secondary containment was found acceptable in Amendment No. 210 to Facility Operating License No. NPF-62 for CPS by letter dated August 17, 2016 (ML16217A332), Clinton Power Station, Unit No. 1 - Issuance of Amendment Concerning Incorporation of Revised Alternative Source Term. This drawdown time of 19 minutes (changed from 12 minutes) included the increased secondary containment volume associated with expansion of the secondary containment boundary to include the FBRA. Since the SRs ensure drawdown remain within the required limits approved by Amendment No. 210 the proposed change does not impact the radiological consequence analyses previously performed for CPS, and the requirements of 10 CFR 50.67 continue to be met.

Based on above, the NRC staff finds the proposed change of the secondary containment boundary acceptable relative to the functional capability of reducing fission product releases to limit dose consequences following a LOCA, because SRs 3.6.4.1.4 on drawdown time and 3.6.4.1.5 on maintaining vacuum for secondary containment, and 10 CFR 50.67 on radiological consequence continue to be met.

3.2 Manual Action for FBRA Inner Door The FBRA includes the inner door and outer door. The inner door is seismic Category I, being designed to withstand tornado missiles, and is included in the current licensing basis as a part of the secondary containment. The FBRA and FBRA outer door, which are included in the revised licensing basis as a part of the secondary containment, are qualified for seismic Category I loads, but are not designed to withstand tornado missiles.

Section 3.3 of attachment 1 to the LAR indicates that when the FBRA inner door is open, dedicated personnel would manually close the inner door in the event of a severe weather or radioactive release occurrence from a LOCA, because the FBRA and FBRA outer door are not designed to withstand tornado missiles. The purpose of the manual action to close the inner door is to protect equipment inside the fuel building from the effects of tornado missile. As discussed in RG 1.117, Revision 1, the equipment used to provide long-term core cooling following a LOCA should be protected.

Section 3.3 of attachment 1 to the LAR describes the manual actions including:

1. Prior to opening the FBRA inner door, verify none of the following are in effect or are projected to be in effect for the period the FBRA inner door will be open:

a) Tornado watch or warning by the National Weather Service.

b) Severe thunderstorm watch or warning by the National Weather Service.

c) High winds warning based on CPS Meteorological (Met) tower data. Current station procedures define this as winds 40 mph [miles per hour] (at 10 meters) for greater than one hour, or any winds 58 mph (at 10 meters).

d) Indication of a LOCA or the possibility of a radioactive release from a LOCA occurring.

2. Verify FBRA area temperature and humidity allow for the ability to close the FBRA inner door without personnel heat stress concerns.

3. Once the FBRA inner door is open, monitor and assess the conditions described in item (1) above. Upon notification of any of the above conditions, dedicated personnel will immediately close the FBRA inner door and close the latching mechanism.

The licensee plans to include the above actions in applicable site procedures and training programs upon implementation of the proposed change.

In addition, to ensure the dedicated operator will not be over-exposed to radiation, a mission dose analysis has been performed by the licensee to determine dose rates and occupancy time for the operator action to close the FBRA inner door. The licensee has determined that there is adequate amount of time for the dedicated operator to close the FBRA inner door. The licensee has evaluated potential errors in performing the manual actions and determined that errors are recoverable prior to the potential severe weather impacting the FBRA.

Further, in the supplement to the LAR, dated July 25, 2022, the licensee states that in the event that the FBRA inner door is prevented from being closed concurrent with the conditions specified in the license amendment request (i.e., with a tornado watch or warning, severe thunderstorm watch or warning, high winds warning, or indication of a LOCA in effect),

TS 3.8.1 Condition E would be entered due to having two required diesel generators (DGs) inoperable. The Required Action would be to restore one required DG to operable status within 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. If one required DG could not be restored to operable status, a unit shutdown would be required within the following 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The Required Actions and associated Completion Times of TS 3.8.1 would be more restrictive than that for TS 3.6.4.1. Therefore, the applicable TS Conditions and the associated Required Actions and Completion Times would limit the amount of time the inner door may be open concurrent with the conditions specified in the license amendment request.

The NRC staff reviewed the proposed manual actions, amount of time for operator action without being over-exposed, and more restrictive TS shutdown requirement for the failure action and finds the proposed manual action acceptable because GDC 2 requirements are met.

For a successful manual action to close the inner door, the secondary containment boundary is restored to the current licensing basis. Based on above, the NRC staff finds that the proposed change of the secondary containment boundary and the proposed manual action acceptable with respect to withstanding the effects of tornado wind and missiles without loss of capability to perform their safety functions to meet GDC 2 requirements for tornado missiles.

3.3 USAR Changes to the LAR provides the markup of the proposed USAR. The NRC staff found that all the proposed USAR changes are consistent with the secondary containment boundary change evaluated in sections 3.1 and 3.2 above and, therefore, are acceptable.

3.4 Risk Insights The NRC staff considered risk insights associated with the proposed change to the secondary containment design basis as part of its review as permitted by guidance in LIC-206, Integrated Risk-Informed Decision-Making for Licensing Reviews Revision 1, dated June 26, 2020 (ML19263A645). As the proposed change was found acceptable relative to the functional capability of reducing fission product releases to limit dose consequences following a LOCA in a previous license amendment mentioned above, the staff focused on risk insights related to the FBRA inner door failing to close and provide tornado missile protection for the equipment inside the fuel building used to provide long-term core cooling following a LOCA.

The NRC staff used the risk triplet (what can go wrong; how likely is it; and what are the consequences) to determine qualitative risk insights as defined and described in LIC-206.

Based on information provided in the LAR, the staff considered an accident scenario that involves events and conditions leading to core damage without mitigation. The events and conditions considered include: (1) a LOCA is in effect, (2) the FBRA inner door is prevented from being closed, (3) a tornado event with accompanying missiles occurred at the CPS site, and (4) equipment inside the fuel building required to provide long-term core cooling is damaged by tornado missiles.

The NRC staff used conservative assumptions for the combined occurrence of a LOCA, tornado, the FBRA inner door failing to close, and the assumption that the equipment in the fuel building used to provide long-term cooling would fail (probability of 1.0) if struck by a tornado missile. The staff also included in its consideration of risk insights, the statement in the LAR that dedicated personnel would be available to close the FBRA inner door, thereby providing a risk management action. With these assumptions, the staff did not identify risk insights or a risk significant issue that would challenge the staffs findings based on deterministic considerations.

4.0 CONCLUSION

The NRC staff finds the proposed change to revise the definition of the secondary containment boundary acceptable based on the staff evaluation of (1) the functional capability of reducing fission product releases to limit dose consequences following a LOCA to meet 10 CFR 50.67 on radiological consequence, and (2) the capability of withstanding the effects of tornado wind and missiles. when necessary, without loss of capability to perform their safety functions to meet GDC 2 requirement.

5.0 STATE CONSULTATION

In accordance with the Commissions regulations, the Illinois State official was notified of the proposed issuance of the amendment on October 18, 2022. The State official had no comments.

6.0 ENVIRONMENTAL CONSIDERATION

The amendment changes requirements with respect to installation or use of a facilitys components located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (87 FR 29886). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.

7.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) there is reasonable assurance that such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributors: L. Chang S. Park Date of Issuance: November 10, 2022

ML22292A035 OFFICE NRR/DORL/LPL3/PM NRR/DORL/LPL3/LA NRR/DSS/SCPB/BC NRR/DRA/APLC NAME JWiebe SRohrer BWittick SVasavada DATE 10/20/2022 10/19/2022 9/21/2022 10/18/2022 OFFICE OGC NRR/DORL/LPL3/BC NRR/DORL/LPL3/PM NAME KDowling NSalgado (SWall for) JWiebe DATE 11/7/2022 11/10/2022 11/10/2022