ML14184B342
| ML14184B342 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 06/27/2014 |
| From: | Korsnick M Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML14184B342 (10) | |
Text
Maria Korsnick Senior Vice President. Northeast Operations 1Chief ExeLon Generation. Nuclear Officer, CENG 100 Constellation Way Suite500P Constellation Energy Nuclear Group, LLC Baltimore, MD 21202 410-470-5133 Office 443-213-6739 Fax www.exeloncorp com maria.korsnick(q~exeloncorp.com June 27, 2014 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 Docket No. 50-410
Subject:
Request for Exemption from 10 CFR 50, Appendix A, GDC-56
References:
(1) NRC Order Number EA-13-109, Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions, dated June 6, 2013 (ML13143A321)
(2) Letter from M. G. Korsnick (CENG) to Document Control Desk (NRC),
Nine Mile Point Nuclear Station, Unit 2, Response per Order EA-13-109 Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions, dated December 12, 2013 On June 6, 2013, the Nuclear Regulatory Commission (NRC) issued Order EA-13-109 (Reference 1) to all licensees that operate boiling-water reactors (BWRs) with Mark I and Mark II containment to take certain actions to ensure the functionality of reliable hardened containment vent systems (HCVS) to remove decay heat and maintain control of containment pressure following events that result in loss of active containment heat removal capability or Extended Loss of AC Power (ELAP), and ensure that containment venting functions are also available during severe accident conditions.
In order to meet the requirements of Reference (1) regarding implementation of a HCVS, Exelon Generation Company, LLC (EGC) determined that an exemption from the requirements of 10 CFR 50, Appendix A, General Design Criterion (GDC) 56, Primary Containment Isolation, is needed to permit an alternative containment isolation valve configuration for Nine Mile Point Unit 2 (NMP2) Penetrations Z-48 and Z-51.
EGC is providing this NMP2 exemption request pursuant to 10 CFR 50.12, Specific Exemptions, to comply with the regulatory commitment made in Reference (2). EGC requests NRC approval of the exemption by June 30, 2015 to allow NMP2 to meet the design requirements and implementation schedule required by NRC Order EA-13-109. EGC will implement the modifications to NMP2 Penetrations Z-48 and Z-51 in accordance with the schedule established
Document Control Desk June 27, 2014 Page 2 to comply with the applicable NRC Order regarding the HCVS. This schedule will be established in the applicable communications with the NRC regarding the applicable NRC Order. Prior to approval of the exemption request by the NRC and implementation of the modifications to NMP2 Penetrations Z-48 and Z-51, the Penetrations will continue to comply with 10 CFR 50, Appendix A, GDC 56.
This letter does not contain any regulatory commitments.
If there are any questions regarding this submittal, please contact Bruce Montgomery, Acting Manager - Licensing, at 443-532-6533.
I declare under penalty of perjury that the foregoing is true and correct. This statement executed on June 27, 2014.
Sincerely, Mary G. Korsnick MGK/STD
Attachment:
(1) Request for Exemption from 10 CFR 50, Appendix A, GDC-56 cc: Regional Administrator, Region I, USNRC Resident Inspector, USNRC Project Manager, USNRC S. Gray, DNR
ATTACHMENT (1)
NINE MILE POINT UNIT 2 REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX A, GDC-56 Nine Mile Point Nuclear Station, LLC June 27, 2014
ATTACHMENT (1)
REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX A, GDC-56
1.0 INTRODUCTION
On June 6, 2013, the Nuclear Regulatory Commission (NRC) issued Order EA-13-109 (Reference 1) to all licensees that operate boiling-water reactors (BWRs) with Mark I and Mark II containment to take certain actions to ensure the functionality of reliable hardened containment vent systems (HCVS) to remove decay heat and maintain control of containment pressure following events that result in loss of active containment heat removal capability or Extended Loss of AC Power (ELAP), and ensure that containment venting functions are also available during severe accident conditions.
In order to meet the requirements of Reference (1) regarding implementation of a HCVS, Exelon Generation Company, LLC (EGC) determined that an exemption from the requirements of 10 CFR 50, Appendix A, General Design Criterion (GDC) 56, Primary Containment Isolation, is needed to permit an alternative containment isolation valve configuration for Nine Mile Point Unit 2 (NMP2) Penetrations Z-48 and Z-51.
Exelon Generation Company, LLC (EGC) is providing this NMP2 exemption request pursuant to 10 CFR 50.12, Specific Exemptions, to comply with the regulatory commitment made in Reference (b). EGC requests NRC approval of the exemption by June 30, 2015 to allow NMP2 to meet the design requirements and implementation schedule required by NRC Order EA-13-109. Approval of the exemption request will allow NMP2 to meet the design requirements and implementation schedule required by the NRC Order EA-1 3-109.
2.0 PROPOSED EXEMPTION 2.1 10 CFR 50, Appendix A, General Design Criterion 56 - Primary Containment Isolation GDC-56 states:
"Each line that connects directly to the containment atmosphere and penetrates primary reactor containment shall be provided with containment isolation valves as follows, unless it can be demonstrated that the containment isolation provisions for a specific class of lines, such as instrument lines, are acceptable on some other defined basis:
(1) One locked closed isolation valve inside and one locked closed isolation valve outside containment; or (2) One automatic isolation valve inside and one locked closed isolation valve outside containment; or (3) One locked closed isolation valve inside and one automatic isolation valve outside containment. A simple check valve may not be used as the automatic isolation valve outside containment; or (4) One automatic isolation valve inside and one automatic isolation valve outside containment. A simple check valve may not be used as the automatic isolation valve outside containment.
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ATTACHMENT (1)
REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX A, GDC-56 Isolation valves outside containment shall be located as close to the containment as practical and upon loss of actuating power, automatic isolation valves shall be designed to take the position that provides greater safety."
2.2 Requested Exemption EGC is requesting an exemption from 10 CFR 50, Appendix A, GDC-56 to allow the implementation of a CIV configuration different than that described in GDC-56 for Penetrations Z-48 and Z-51. Specifically, the exemption will modify containment isolation requirements to eliminate the need to maintain an inboard CIV and adding a second outboard CIV to provide the redundancy needed to prevent inadvertent releases of radioactive material to the environment.
In addition to the Wetwell penetration (Penetration Z-51), the exemption request addresses the penetration associated with the Drywell (i.e., Penetration Z-48) to allow this modification to be utilized in the event that this strategy is utilized to satisfy Phase 2 of the NRC Order EA-1 3-109.
Please note that the potential exists to utilize an alternate strategy.
EGC will implement the modifications to NMP2 Penetrations Z-48 and Z-51 in accordance with the schedule established to comply with the applicable NRC Order regarding the HCVS. This schedule will be established in the applicable communications with the NRC regarding the applicable NRC Order. Prior to NRC approval of the exemption request and implementation of the modifications to NMP2 Penetrations Z-48 and Z-51, the Penetrations will continue to comply with 10 CFR 50, Appendix A, GDC 56.
3.0 BACKGROUND
NMP2 Updated Safety Analysis Report (USAR) Section 6.2.4.3.2 states:
"The drywell and suppression chamber purge lines have isolation capabilities commensurate with the importance to safety of isolating these lines. Each line has two normally closed/fail closed valves - one located inside (nitrogen operated) and one located outside (air operated) the primary containment ... The isolation valves are interlocked to preclude opening of the valves while a primary containment isolation signal exists (Table 6.2-56). The radiological consequences of a LOCA occurring during containment purge system (CPS) operation (isolation valves wide open) with the SGTS in the pressure control mode are discussed in Section 15.6.5."
NMP2 USAR Section 6.2.5.2.4 defines that all Containment Purge System primary CIVs are automatically closed after 15 seconds when a high radiation level is detected in the exhaust flow. This time delay of 15 seconds prevents automatic closure of the Containment Purge System primary CIVs due to spurious power transients.
NMP2 USAR Table 6.2-56 defines the penetrations and the CIVs. Penetrations Z-48 and Z-51 are the Containment Purge System exhaust pathways from the Drywell and the Suppression Chamber (i.e., the Wetwell), respectively. This table defines that the penetrations comply with 10 CFR 50, Appendix A, GDC 56, Primary Containment Isolation. Figure 1 provides an illustration of the existing configuration.
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ATTACHMENT (1)
REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX A, GDC-56 GTS Train
'A' GTS Train
'B' Figure 1 - Illustration of Existing Configuration In order to meet the requirements of Reference 1 regarding implementation of a HCVS, EGC determined that an exemption from the requirements of 10 CFR 50, Appendix A, GDC 56 is required to permit an alternative CIV configuration for Penetrations Z-48 and Z-51.
4.0 TECHNICAL ANALYSIS
The design of the HCVS flow paths is currently in the conceptual design stage. The Wetwell vent path will be implemented as Phase 1 of the NRC Order EA-13-109. Phase 2 of the HCVS Order requires either the installation of a Drywell vent path or a vent strategy that makes the use of a Drywell vent path unlikely. Industry guidance has not been developed for the Phase 2 options and the guidance will have an impact on which of the Phase 2 options are implemented at Nine Mile Point Unit 2. Regardless of the final design, the CIVs that will be part of the HCVS pathway will be required to be available post-accident. The following information provides the current conceptual design information regarding the proposed HCVS.
4.1 Need for Alternate Containment Isolation Valve Configuration The HCVS will be one element of the core damage prevention strategies that will permit venting the containment to remove decay heat and limit containment pressurization. This function supports core cooling strategies during an ELAP.
The HCVS flow paths from the containment (via the Suppression Chamber (i.e., the Wetwell) and the Drywell) to an elevated release point above the Reactor Building roof are shown in the simplified piping and instrumentation diagram (P&ID) in Figure 2.
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ATTACHMENT (1)
REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX A, GDC-56 POS POSEXISTING PIPING NCFC NOFC WLMING S
'WAL GTS Train
'B' Figure 2 - Illustration of Proposed HCVS The HCVS at NMP2 is fully independent of the HCVS from Nine Mile Point Unit 1 (NMP1). The piping flow path is shared with the Containment Purge System up to a Normally Closed, Fail-Closed (NCFC), air-operated isolation valve. The flow path is then dedicated out to the release point. No ductwork is used in the system. This ensures that all the HCVS flow out of the containment is discharged to the outside atmosphere above the NMP2 Reactor Building.
The HCVS flow path downstream of the CIVs will have a normally closed, air-operated Pressure Control Valve (PCV). The PCV will be used to manually control upstream pressure. Similar to the CIVs, the PCV will utilize a Direct Current (DC) powered Solenoid-Operated Valve (SOV) to control the pneumatic supply and will be controlled from the Main Control Room (MCR). A manual, remote - pneumatic mode of operation for the PCV will be available from a remote panel located outside of the Reactor Building as a backup in compliance with HCVS Order requirements.
The HCVS vent path will share a flow path with the Containment Purge System. It also shares piping with the potential vent pathway that may be utilized as the Phase 2 option, i.e., the Drywell vent path downstream of the Drywell outboard CIV. The control logic for the CIVs is not altered. The HCVS design will not preclude the CIVs from performing their design basis function.
The HCVS vent path piping and supports up to and including the second CIV will be designed in accordance with existing design basis, with one exception. The inboard CIV will no longer be inside containment. Both HCVS ClVs will be located outside containment. This arrangement will not meet GDC-56. The existing inboard isolation valve will no longer function as a valve, but as a pipe in Figure 2.
Associated actuators, position indication, and power supplies are also designed consistent with the requirements to meet the design basis for containment isolation.
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ATTACHMENT (1)
REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX A, GDC-56 4.2 Justification for Alternate Containment Isolation Valve Configuration The design of the Containment Purge System and HCVS CIVs will be consistent with the plant's CIV design basis. The valves will be air-operated, spring-to-close, valves (normally closed, fail closed) with DC powered SOVs and will be operated from the MCR.
Since these CIVs are shared by the HCVS and the Containment Purge System, both CIVs in the Suppression Chamber and Drywell penetration will have an automatic closure signal for containment isolation. Inadvertent operation will be addressed by controlling the associated SOVs with key-locked switches and by locking the manual valves that may be used for backup operation. Periodic CIV testing will be performed in accordance with the Surveillance Test Program. The CIVs will utilize the existing automatic containment isolation signals.
The existing inboard CIV will either be locked open or removed. This decision will be made during the detailed design phase for the HCVS.
The re-location of the second CIV on Penetrations Z-48 and Z-51 to an outboard location for the Containment Purge System and HCVS lines will improve system reliability, due to the use of new dedicated nitrogen supplies in lieu of relying upon existing manifolds, increased accessibility in case of failure, and less severe environmental conditions for the SOVs and instrumentation.
4.3 Precedents Limerick, LaSalle, Susquehanna and Columbia have designs that possess both CIVs outside of containment for the Containment Purge System penetrations. Following NRC approval of this exemption request and implementation by NMP2, all of the BWR Mark II containments will have a similar configuration regarding the location of both CIVs outside of containment for the Containment Purge System penetrations.
5.0 EXEMPTION JUSTIFICATION AND SPECIAL CIRCUMSTANCES 10 CFR 50.12, Specific exemptions, states that the Nuclear Regulatory Commission may grant exemptions from the requirements of the regulations of this part provided three conditions are met. The three conditions are: 1) the exemption is authorized by law, 2) the exemption will not present an undue risk to the health and safety of the public, 3) the exemption is consistent with the common defense and security. In addition, the Commission will not consider granting an exemption unless special circumstances are present.
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ATTACHMENT (1)
REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX A, GDC-56 5.1 This exemption is authorized by law Granting of the proposed exemption will not result in a violation of the Atomic Energy Act of 1954, as amended, or the Commission's regulations. As required by 10 CFR 50.12(a) (1), this requested exemption is "authorized by law." No statute exists that precludes the activities covered by this exemption request. The NRC has the authority under the Atomic Energy Act and 10 CFR 50.12 to grant exemptions from the requirements of Part 50 upon showing proper justification. The provisions of 10 CFR 50, Appendix A, General Design Criteria for Nuclear Power Plants, were adopted at the discretion of the Commission consistent with its statutory authority. Therefore, the NRC may determine that alternative means are adequate to provide reasonable assurance of safety and security.
The technical analysis presented above provides sufficient justification to support the proposed implementation of the alternate CIV configuration to permit installation of hardened containment vents to address the NRC Order.
5.2 This exemption will not present an undue risk to public health and safety The technical evaluation for this exemption request adequately justifies that use of implementation of the alternate CIV configuration to permit installation of hardened containment vents to address the NRC Order is consistent with the overall design function of the primary containment and the underlying purpose of the regulation.
Since the CIVs will remain capable of performing their containment isolation function in the event of an accident or transient requiring containment isolation, the consequences of a postulated accident or transient is not increased. In addition, the exemption will permit NMP2 to establish a HCVS to provide a controlled and safe approach to assure compliance with NRC Order EA-1 3-109, Reliable Hardened Containment Vents.
5.3 This exemption is consistent with common defense and security The request change does not affect any aspect of the security program and, as a result, is consistent with the common defense and security.
5.4 Special circumstances support the issuance of an exemption 10 CFR 50.12(a)(2) states that the NRC will not consider granting an exemption to the regulations unless special circumstances are present. The requested exemption meets the special circumstances of 10 CFR 50.12(a)(2)(ii) which states that, "Application 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."
In this particular circumstance, a literal application of the subject regulation is not necessary to achieve the underlying purpose of the regulation. The proposed alternative CIV configuration meets the assurance objective and general performance requirements of 10 CFR 50, Appendix A, GDC-56 associated with the need to provide reliable containment isolation. The overall level of system performance, as modified by the requested exemption, will not result in a reduction in containment isolation capabilities for the protection of an inadvertent release of radioactive material to the environment from those exemptions and alternatives previously approved for other BWRs with Mark II containments.
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ATTACHMENT (1)
REQUEST FOR EXEMPTION FROM 10 CFR 50, APPENDIX A, GDC-56
6.0 CONCLUSION
EGC considers this exemption request to be in accordance with the criteria of 10 CFR 50.12(a).
Maintaining containment isolation requirements at NMP2 commensurate with an operating reactor facility is necessary to achieve the underlying purpose of 10 CFR 50, Appendix A, GDC-56.
As required by 10 CFR 50.12, the requested exemption is authorized by law, presents no undue risk to public health and safety, and is consistent, with common defense and security.
Therefore, granting approval of this exemption request does not violate the underlying purpose of the rule and special circumstances exist to justify the approval of an exemption from the subject requirements.
EGC will implement the modifications to NMP2 Penetrations Z-48 (if chosen as the strategy to meet Phase 2 of NRC Order EA-13-109) and Z-51 in accordance with the schedule established to comply with NRC Order EA-1 3-109 regarding the HCVS. This schedule will be established in the applicable communications with the NRC regarding the applicable NRC Order. Prior to NRC approval of the exemption request and implementation of the modifications to NMP2 Penetrations Z-48 and Z-51, the Penetrations will continue to comply with 10 CFR 50, Appendix A, GDC 56.
7.0 REFERENCES
1 NRC Order Number EA-13-109, Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions, dated June 6, 2013 (ML13143A321).
- 2. Letter from M. G. Korsnick (CENG) to Document Control Desk (NRC), Nine Mile Point Nuclear Station, Unit 2, Response per Order EA-13-109 Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions, dated December 12, 2013.
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