RA-16-008, Response to Request for Additional Information Regarding Request for Extension to Comply with Phase 2 of NRC Order EA-13-109: Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe..

Response to Request for Additional Information Regarding Request for Extension to Comply with Phase 2 of NRC Order EA-13-109: Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe..

ML16047A094
Person / Time
Site:	Oyster Creek
Issue date:	02/15/2016
From:	Jim Barstow Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
EA-13-109, RA-16-008, RS-16-016, TAC MF4352
Download: ML16047A094 (12)

Text

Exelon Generation (~)

RS-16-016 RA-16-008 February 15, 2016 U.S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, DC 20555-0001 Oyster Creek Nuclear Generating Station Renewed Facility Operating License No. DPR-16 NRC Docket No. 50-219

Subject:

Response to Request for Additional Information Regarding Request for Extension to Comply with Phase 2 of NRC Order EA-13-109: Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions (TAC No. MF4352)

References:

1. NRC Order EA-13-109, Issuance of Order to Modify Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions, dated June 6, 2013

2. Exelon Generation Company, LLC Letter to USNRC, Request for Extension to Comply with NRC Order EA-13-109, "Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions,"

dated June 2, 2014 (RS-14-081)

3. Exelon Generation Company, LLC Letter to USNRC, Permanent Cessation of Operations at Oyster Creek Nuclear Generating Station, dated January 7, 2011

4. NRC Email J. Hughey (NRC) to D. Distel (Exelon) - Request for Additional Information Regarding Request for Extension to Comply with NRC Order EA-13-109: Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions, dated May 6, 2015 On June 6, 2013, the Nuclear Regulatory Commission (NRC) issued Order EA-13-109 (Reference 1) to all licensees that operate boiling-water reactors with Mark I and Mark 11 containment designs. The Order was effective immediately and is applicable to Oyster Creek Nuclear Generating Station (Oyster Creek). In Reference 2, Exelon Generation Company, LLC (EGC) requested an extension of the final compliance dates of Order EA-13-109 requirements in Section IV of NRC Order EA-13-109 concerning implementation of the Phase 1 (wetwell vent) and Phase 2 (drywell vent) at Oyster Creek until January 31, 2020. Also in Reference 2, EGC stated that it will submit a request for relief from NRC Order EA-13-109 no later than

U.S. Nuclear Regulatory Commission Response to Request for Additional Information February 15, 2016 Page 2 January 31, 2020 based upon the permanent shutdown condition of the plant at that time. In Reference 3, EGC had previously notified the NRC of EGC's plans to permanently shut down Oyster Creek and cease operation no later than December 31, 2019.

The purpose of this letter is to provide the response to the NRC request for additional information (RAI) (Reference 4) regarding the Oyster Creek request for extension to comply with Phase 2 of NRC Order EA-13-109. The responses to the NRC RAls are provided in the enclosure to this letter.

This letter contains new regulatory commitments, which are identified in Enclosure 2 to this letter. If you have any questions regarding this response, please contact David P. Helker at 610-765-5525.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 15th day of February 2016.

Respectfully submitted, James Barstow Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosures:

1. Oyster Creek Nuclear Generating Station - Response to Request for Additional Information Regarding Request for Extension to Comply with Phase 2 of NRC Order EA-13-109: Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions (TAC No. MF4352)

2. Summary of Regulatory Commitments cc: Director, Office of Nuclear Reactor Regulation NRC Regional Administrator - Region I NRC Senior Resident Inspector - Oyster Creek Nuclear Generating Station NRC Project Manager, NRA - Oyster Creek Nuclear Generating Station Mr. John D. Hughey, NRR/JLD/JOMB, NRC Manager, Bureau of Nuclear Engineering - New Jersey Department of Environmental Protection Mayor of Lacey Township, Forked River, NJ

Enclosure 1 Oyster Creek Nuclear Generating Station Response to Request for Additional Information Regarding Request for Extension to Comply with Phase 2 of NRC Order EA-13-109:

Order Modifying Licenses with Regard to Reliable Hardened Containment Vents Capable of Operation Under Severe Accident Conditions (TAC No. MF4352)

(7 pages)

Response to Request for Additional Information Page 1of7 Similar to Phase 1 RAls, the staff will be evaluating Oyster Creek's request against the technical guidance of NEI 13-02, Rev. 1, as endorsed by ISG-2015-01. As such, the licensee should provide a discussion of the differences between Oyster Creek's Phase 2 hardware and procedural strategies during the period of extension and the requirements of Sections B.1 and B.2 of Order EA-13-109. Utilize information from NEI 13-02, Rev.1, Section 1.2, HCVS Guiding Principles, as appropriate. This discussion may include any proposed compensatory measures.

Response

In accordance with NRC Order EA-13-109 §IV.B, Oyster Creek's Phase 2 compliance date is no later than startup from the first refueling outage that begins after June 30, 2017, or June 30, 2019, whichever comes first. Startup from the first refueling outage after June 30, 2017 is Fall 2018 and; therefore, defines the Order Phase 2 compliance date. As previously documented in Reference 3 of the cover letter, Exelon Generation Company, LLC (EGC) plans to permanently shut down Oyster Creek and cease operation no later than December 31, 2019. Therefore, the period of extension is limited to approximately 13 months from the compliance date. Oyster Creek will fully implement Order EA-12-049 (FLEX) in Fall 2016. The FLEX capability under Beyond Design Basis External Event (BDBEE) conditions will provide a significant additional margin of safety for preventing core damage, and further reduces the risk of core damage where Order EA-13-109 Phase 2 capability may be needed. This reduction in core damage probability resulting from an Extended Loss of AC Power (ELAP) combined with the short duration of the period of extension based on the limited remaining plant operating life substantially reduces the risk associated with an ELAP-related core damage event where Order EA-13-109 Phase 2 capabilities are applicable.

Oyster Creek will not have hardware capabilities required by Order EA-13-109, Attachment 2, Section B.1 (Drywell Vent Functional Requirements) during the period of extension.

Oyster Creek will implement a containment venting strategy that, under severe accident conditions, makes it unlikely that a severe accident capable drywell vent is needed for at least seven (7) days. The venting strategy will be substantially consistent with Order EA-13-109, , Section B.2 (Containment Venting Strategy Requirements) and the guidance for Phase 2 contained in NEI 13-02, Revision 1, including the necessary procedures, installed and portable equipment including instrumentation necessary to support the venting strategy. This venting strategy will be in place during the period of extension.

Additional details of the venting strategy capabilities and how they differ from NEI 13-02, Revision 1 guidance is provided in the response to Question 2. Compensatory actions are also discussed in the response to Question 2.

Response to Request for Additional Information Page 2 of 7 If hardware and procedural strategies described as Option 1 (SAWA) or Option 2 (SAWA with SAWM) of NEI 13-02, Rev.1, Section 1.2, HCVS Guiding Principles, are to be employed during the period of extension, the licensee should provide a discussion of the capabilities of Oyster Creek's hardware and procedural strategies as compared to the guidance of NEI 13-02, Rev. 1, Appendix C, Severe Accident Water Management, and Appendix I - Severe Accident Water Addition. This discussion may also include any proposed compensatory measures.

Response

Oyster Creek will implement the elements of Option 2, Severe Accident Water Addition (SAWA) and Severe Accident Water Management (SAWM) as described in NEI 13-02, Revision 1, Section 1.2, HCVS Guiding Principles, during the period of extension. This response assumes a baseline FLEX capability for installed and portable equipment including instrumentation that will exist when Order EA-12-049 compliance is achieved. It is from this assumption of baseline equipment capability that hardware and procedure strategy capabilities have been assessed to compare against the guidance of NEI 13-02, Revision 1, Appendices C and I. It is also from this assumption of baseline capability that appropriate compensatory actions have been determined for the interim period.

Comparison to NEI 13-02, Revision 1, Appendix I, Severe Accident Water Addition:

Section 1.1.2, Water Addition Point

• The Oyster Creek water addition point will be to the Reactor Pressure Vessel (RPV) via Core Spray Loop 1, which is the same as one of the two FLEX flow paths. The planned location for connection and control of flow during a FLEX (no core damage) event is the grade level (elevation 23' referenced to mean sea level) of the Reactor Building, a short distance from the building entry point. This location is not expected to be accessible under severe accident conditions. As a compensatory action, Oyster Creek will design and construct a valve manifold that can be located outside the Reactor Building and away from the containment vent piping such that dose rates to plant operators will remain acceptable for seven (7) days. The valve manifold will allow for manually operated SAWA flow control in an environmentally suitable location. The initial connection to the core spray system can be made before the Reactor Building becomes uninhabitable due to high radiation levels. The assumed time to core damage is 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 40 minutes and is based on the time from start of the ELAP to Isolation Condenser shell side water boil down to the top of the condenser tube bundle. This time is conservative because there is additional heat removal capability as the Isolation Condenser shell side continues to boil down and uncover tubes.

Section 1.1.3, RPV Pressure Control Oyster Creek has implemented the Boiling Water Reactor Owners Group (BWROG) EPG/SAGs that provide the necessary direction to control pressure and to depressurize the RPV prior to entry into the SAGs. Oyster Creek capabilities are consistent with this guidance without the need for compensatory actions.

Response to Request for Additional Information Page 3 of 7 Section 1.1.4, Water Addition Source The Oyster Creek site specific required SAWA flow rate is 275 gallons per minute for the first four hours and 55 gallons per minute for the remainder of the 168 hour0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> (seven day) period. This flow rate is based on guidance in NEI 13-02, Revision 1, Section 4.1.1.2.3. Rated Thermal Power for Oyster Creek is 1930 MWth* The hydraulic calculation demonstrated FLEX (SAWA) pump capability is 449 gallons per minute to the intended SAWA connection point with the currently planned FLEX configuration thus providing substantial margin to the required flow rate of 275 gpm to account for the planned modifications to the FLEX (SAWA) flow path. These modifications are not expected to have a substantial impact on the FLEX (SAWA) pump flow capability. The hydraulic calculation will be reviewed and revised as needed to account for modifications to the FLEX (SAWA) flow path to account for the additional valve manifold and hose from the FLEX (SAWA) pump to the installed connection point of Core Spray System Loop 1. The revision to the hydraulic calculation will provide confirmation of at least 275 gpm SAWA flow capability in the FLEX (SAWA) flow configuration.

The time needed to establish SAWA flow using the above described configuration is less than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> from the onset of the loss of all injection sources.

The SAWA connection point will be to Core Spray Loop 1 on Reactor Building grade elevation 23'. This connection point is located a short distance from the Reactor Building entry location and is easily accessible. Considering the ease of access and the short distance within the Reactor Building to the connection point, there is reasonable assurance that the connection can be made using portable hoses well within the time frame of expected Reactor Building habitability including radiation and thermal conditions.

The installed flow path to the RPV includes check valves V-20-150 and V-20-152 that will provide the backflow prevention function. These check valves are also Primary Containment Isolation Valves (PCIVs). As PCIVs, these valves are tested consistent with PCIV testing requirements defined in the plant Technical Specifications and this satisfies the testing requirements for back flow prevention valves defined in NEI 13-02, Revision 1 guidance and other endorsed guidance related to HCVS Phase 2 implementation.

Section 1.1.5, Motive Force Motive force for SAWA will be provided by the same equipment used for FLEX as implemented under Order EA-12-049. The FLEX (SAWA) pump is a portable diesel driven pump. This pump will be deployed to a location that is well shielded by intervening structures that will substantially lower dose rates from the containment vent line when used under severe accident conditions.

The path from the fuel oil storage tanks to the equipment deployment location is also well shielded by intervening structures. FLEX and SAWA water flow paths to the RPV are essentially the same.

Motive force for SAWA electrical loads will be provided by the same equipment used for FLEX as implemented under Order EA-12-049. The FLEX (SAWA) generator is a portable diesel driven generator. This generator will be deployed to a location that is well shielded by intervening structures that will substantially lower dose rates from the containment vent line when used under severe accident conditions. The path from the fuel oil tanks to the equipment deployment location is also well shielded by intervening structures. SAWA electrical loads are

Response to Request for Additional Information Page 4 of 7 enveloped by the FLEX electrical loads in terms of being powered by the FLEX electrical strategy and with total SAWA loading on the FLEX portable diesel generator that is less than or equal to total FLEX loads.

The 480 volt portable diesel generator connection point to the plant 480 volt distribution system will occur in the 480 volt switchgear room. This room is located outside the Reactor Building; however, the torus extends under the floor of this room. There is two (2) feet of reinforced concrete between the top of the torus and the grade elevation of the 480 volt switchgear room.

This shielding will provide a substantial reduction in dose rates to personnel making the cable connections and electrical lineups, but the shielded dose rates may exceed 2 R/Hr based on a comparison of the Oyster Creek configuration with radiological evaluations performed at other Mark I sites. The minimum time to core damage is 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 40 minutes and the FLEX timeline for completing the electrical connection lineup is 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> and 30 minutes. This results in an approximate 50 minute window in which personnel may be exposed to a 2 R/Hr or greater dose field. Oyster Creek will further evaluate implementation times to determine if a shorter deployment time can be achieved. As an alternative, Oyster Creek may perform a Modular Accident Analysis Program (MAAP) evaluation to determine a best estimate time to core damage that considers the additional time from Isolation Condenser shell side boil down to the top of the tube bundle to the onset of core damage. Using one or a combination of both options, Oyster Creek will confirm the cable connections and electrical lineups can be completed with an acceptable dose to personnel consistent with NEI 13-02, Revision 1, Section 4.2.5.1.

Section 1.1.6, Instrumentation The Oyster Creek FLEX electrical strategy repowers wide range torus level and wide range drywell pressure instruments that are Regulatory Guide (RG) 1.97 qualified. The instruments that are repowered are shown in the following table.

Instrument Instrument Powered by RG 1.97 Number Function FLEX Strategy Qualification Notes Torus wide range Only need one of Ll-243-2A & 28 Yes Yes level two instruments Drywell wide Only need one of PT-53 & 54 Yes Yes range pressure two instruments The FLEX strategy does not have a means of measuring flow rate to the RPV. Oyster Creek will select a suitable in-line flow measurement instrument so that the SAWA flow rate can be determined and monitored.

Section 1.1.7, Severe Accident Considerations Unless specifically noted in Sections 1.1.2 through 1.1.6, Oyster Creek has determined that the thermal and radiological impacts on operator actions that may exist under severe accident conditions assumed in Order EA-13-109 and as defined in NEI 13-02, Revision 1 are acceptable.

Comparison to NEI 13-02, Revision 1, Appendix C, Severe Accident Water Management:

Oyster Creek will implement a Severe Accident Water Management strategy consistent with Appendix C of NEI 13-02, Revision 1. This will include implementation of the BWROG

Response to Request for Additional Information Page 5 of 7 EPG/SAG Revision 3 and approved Issue 1314 that incorporates guidance for SAWA/SAWM in the plant Severe Accident Management Guidelines (SAMGs). This is consistent with the approach taken by BWRs with Mark I and II containments that submitted combined Phase 1 and 2 Overall Integrated Plans (OIPs) on or before December 31, 2015.

Significant attributes of the water management strategy that will be implemented include:

1. Preservation of the wetwell vent path for at least seven (7) days.

2. Use SAWA equipment and capabilities to execute the SAWM strategy.

3. Initiate SAWA flow at 275 gallons per minute within eight (8) hours of the ELAP event and reduce that flow rate as needed after four (4) hours in order to maintain torus level below the wetwell vent line. Maintain a minimum flow capability of 55 gallons per minute for the remainder of the 168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> following the start of the ELAP.

4. Monitor torus level and drywell pressure adjusting SAWA flow and venting containment as necessary to maintain containment parameters within acceptable limits.

These attributes are consistent with the SAWM strategies being implemented for BWRs with Mark I and II containments to meet the Phase 2 requirements of NRC Order EA-13-109.

Significant existing plant design features that support the water management strategy include:

1. The wetwell vent line connection point to the torus is 12" from the top of the torus and provides essentially the full volume of the torus to accommodate water addition for at least seven days without the loss of the wetwell vent function.

2. The wetwell wide range level instrument spans from 1O" from the torus bottom to the top of the torus. The span of the instrument will provide monitoring capability of torus level for at least seven days.

3. Nominal wetwell level is 153 inches providing available freeboard of 195" (16'-3") before the loss of wetwell vent function.

4. The drywell spillover height is 2'-5" as defined from the elevation of the drywell floor to the lip of the vent pipes from the drywell to torus. This provides quenching of core debris and prolongs the time to containment failure from liner melt-through should SAW A flow be interrupted or delayed.

These plant design features are consistent with the reference plant evaluations performed in support of the SAWM strategy guidance provided in NEI 13-02, Revision 1, and documented in EPRI Technical Report 3002003301, Technical Basis for Severe-Accident Mitigating Strategies.

The reference plant analysis demonstrates that a SAWM strategy can preserve the wetwell vent path for at least seven days and makes it unlikely that a drywell vent is needed to maintain containment pressure within acceptable limits. The above described SAWM attributes and plant specific design features provide reasonable assurance that the reference plant evaluation results are applicable to Oyster Creek when the SAWM strategy and the compensatory measures described below are implemented.

Response to Request for Additional Information Enclosure .1 Page 6 of 7 Compensatory Measures

1. Construct a portable valve manifold that can be located outside the Reactor Building and used to control SAWA flow to the RPV.

2. Incorporate an in-line flow meter in the SAWA flow path so that SAWA flow rate can be monitored and adjusted as needed to preserve the wetwell vent path.

3. Review and revise, if necessary, the hydraulic calculation to confirm the FLEX (SAWA) pump can deliver at least 275 gallons per minute flow rate to the RPV with containment pressure at the Primary Containment Pressure Limit (PCPL). The calculation will consider changes in the flow path from the currently planned FLEX to the SAWA flow path.

4. Confirm a sufficient quantity of hose and connectors to support the SAWA flow path using the portable manifold described in Item 1.

5. Perform either a MAAP evaluation to determine best estimate time to start of core damage, or confirm that the electrical cable deployment and electrical lineup can be completed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 40 minutes from the start of the ELAP.

6. Implement BWROG EPG/SAG Revision 3 and Issue 1314 to provide guidance for implementing SAWM strategies. The elements of this guidance are shown on Attachment 1.

Response to Request for Additional Information Page 7 of 7 Attachment 1 - SAWM SAMG Approved Language The following general cautions, priorities and methods will be evaluated for plant specific applicability and incorporated as appropriate into the plant specific SAMGs using administrative procedures for EPGISAG change control process and implementation. SAMGs are symptom based guidelines and therefore address a wide variety of possible plant conditions and capabilities while these changes are intended to accommodate those specific conditions assumed in Order EA-13-109. The changes will be made in a way that maintains the use of SAMGs in a symptom based mode while at the same time addressing those conditions that may exist under extended loss of AC power (ELAP) conditions with significant core damage including ex-vessel core debris.

Actual Approved Language that will be incorporated into site SAMG*

Cautions:

• Addressing the possible plant response associated with adding water to hot core debris and the resulting pressurization of the primary containment by rapid steam generation.

• Addressing the plant impact that raising suppression pool water level above the elevation of the suppression chamber vent opening elevation will flood the suppression chamber vent path.

Priorities:

With significant core damage and RPV breach, SAMGs prioritize the preservation of primary containment integrity while limiting radioactivity releases as follows:

• Core debris in the primary containment is stabilized by water addition (SAWA).

• Primary containment pressure is controlled below the Primary Containment Pressure Limit (Wetwell venting).

• Water addition is managed to preserve the Mark 1/11 suppression chamber vent paths, thereby retaining the benefits of suppression pool scrubbing and minimizing the likelihood of radioactivity and hydrogen release into the secondary containment (SAWM).

Methods:

Identify systems and capabilities to add water to the RPV or drywell, with the following generic guidance:

• Use controlled injection if possible.

• Inject into the RPV if possible.

Maintain injection from external sources of water as low as possible to preserve suppression chamber vent capability.

• Actual language may vary by acceptable site procedure standards, but intent and structure should follow this guidance.

Response to Request for Additional Information Enclosure 2 Page 1 of 2 Enclosure 2

SUMMARY

OF REGULATORY COMMITMENTS The following table identifies commitments made in this document. (Any other actions discussed in the submittal represent intended or planned actions. They are described to the NRC for the NRC's information and are not regulatory commitments.)

COMMITTED I COMMITMENT TYPE I

COMMITMENT DATE OR ONE-TIME ACTION PROGRAMMATIC "OUTAGE" I I (Yes/No) (Yes/No)

1. Construct a portable valve manifold that can be located outside the Reactor Building and used to control SAWA flow to the RPV. Prior to startup from Location will be away from the containment OC1 R27 Refuel vent piping such that dose rates to plant Yes No Outage operators will remain acceptable for seven (Fall 2018)

(7) days.

2. Incorporate an in-line flow meter in the Prior to startup SAWA flow path so that SAWA flow rate can from be monitored and adjusted as needed to OC1 R27 Refuel Yes No preserve the wetwell vent path. Outage (Fall 2018)

3. Review and revise, if necessary, the Prior to startup hydraulic calculation to confirm the FLEX from (SAWA) pump can deliver at least 275 OC1 R27 Refuel Outage gallons per minute flow rate to the RPV with (Fall 2018) containment pressure at the Primary Containment Pressure Limit (PCPL). The Yes No calculation will consider changes in the flow path from the currently planned FLEX to the SAW A flow path.

Response to Request for Additional Information Enclosure 2 Page 2 of 2 COMMITTED I COMMITMENT TYPE I

COMMITMENT DATE OR ONE-TIME ACTION PROGRAMMATIC 11 0UTAGE 11 I I (Yes/No) (Yes/No)

4. Confirm a sufficient quantity of hose and Prior to startup connectors to support the SAWA flow path from using the portable manifold described in OC1 R27 Refuel Outage Item 1. Yes No (Fall 2018)

5. Perform either a MAAP evaluation to Prior to startup determine best estimate time to start of core from damage, or confirm that the electrical cable OC1 R27 Refuel deployment and electrical lineup can be Outage completed within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 40 minutes from (Fall 2018) the start of the ELAP. Oyster Creek will Yes No confirm the cable connections and electrical lineups can be completed with an acceptable dose to personnel consistent with NEI 13-02, Rev. 1, Section 4.2.5.1.

6. Implement BWROG EPG/SAG Revision 3 Prior to startup and Issue 1314 to provide guidance for from implementing SAWM strategies. The OC1 R27 Refuel Outage elements of this guidance are shown on (Fall 2018) No Yes Attachment 1 of Exelon letter to the NRC (RS-16-016).