Westinghouse Electric Company, Response to RAI …RAI-DCP-CN06-SBP-01 RAI-DCP-CN09-SBP-01 RAI-DCP-CN45-SBP-01 RAI-DCP-CN59-SBP-01 Questions or requests for additional information related

ýWestinghouse Westinghouse Electric CompanyNuclear Power PlantsP.O. Box 355Pittsburgh, Pennsylvania 1 5230-0355USA

Directtel: 412-374-6206Direct fax: 724-940-8505

e-mail: [email protected]

U.S. Nuclear Regulatory CommissionATTENTION: Document Control DeskWashington, D.C. 20555

Your ref. Docket No. 52-006Ourref: DCPNRC_002983

July 29, 2010

Subject: AP1000 Response to Request for Additional Information (SRP 23)

Westinghouse is submitting a response to the NRC request for additional information (RAI) on SRPSection 23. This RAI response is submitted in support of the AP1000 Design Certification AmendmentApplication (Docket No. 52-006). The information included in this response is generic and is expected toapply to all COL applications referencing the AP 1000 Design Certification and the AP 1000 DesignCertification Amendment Application.

Enclosure 1 provides the response for the following RAI(s):

RAI-DCP-CN06-SBP-01RAI-DCP-CN09-SBP-01RAI-DCP-CN45-SBP-01RAI-DCP-CN59-SBP-01

Questions or requests for additional information related to the content and preparation of this responseshould be directed to Westinghouse. Please send copies of such questions or requests to the prospectiveapplicants for combined licenses referencing the AP 1000 Design Certification. A representative for eachapplicant is included on the cc: list of this letter.

Very truly yours,

Robert Sisk, ManagerLicensing and Customer InterfaceRegulatory Affairs and Strategy

/Enclosure

1. Response to Request for Additional Information on SRP Section 23 -Dc)(Osýjýz

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DCPNRC 002983July 29, 2010

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cc: D. JaffeE. McKennaB. AndersonM. WentzelT. SpinkP. HastingsR. KitchenA. MonroeP. JacobsC. PierceE. SchmiechG. ZinkeR. GrumbirS. Ritterbusch

U.S. NRCU.S. NRCU.S. NRCU.S. NRCTVADuke PowerProgress EnergySCANAFlorida Power & LightSouthern CompanyWestinghouseNuStart/EntergyNuStartWestinghouse

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0609Ub.doc 7/28/2010 6:49 PM

DCPNRC 002983July 29, 2010

ENCLOSURE 1

Response to Request for Additional Information on SRP Section 23

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AP1000 TECHNICAL REPORT REVIEW

Response to Request For Additional Information (RAI)

RAI Response Number: RAI-DCP-CN06-SBP-01Revision: 0

Question:

The NRC has completed its review of the final information on proposed changes for the AP1 000Design Control Document (DCD), Revision 18, dated April 26, 2010 and have the followingquestions to change number 6 related to the component cooling water (CCS) system.

Change #6

1. Information previously supplied with in a letter dated January 20, 2010 for Section15.6.2, "Failure of Small Lines Carrying Primary Coolant Outside Containment," wasomitted from the April 26, 2010 submittal. This information seemed to be relevantbut was removed without explanation. Additional information is needed to confirmthat a change is no longer needed to Chapter 15.

2. The basis for the increased CCS surge tank vent line from 2" to 3" (over flowprotection due to normal residual heat removal system leakage into CCS) was notdescribed in the DCD, Section 9.2.2. The applicant should consider adding thisinformation to the DCD.

3. The flow rate (GPM) of the CCS/RNS relief valve(s) through the WWS was notdescribed as related to the capacity of the auxiliary building sump pumps (concernsfor potential building flooding if the relief valve flow rate exceeds the sump pumpflow rate). The applicant should consider adding this information to the DCD.

Westinghouse Response:

1. The information was deleted from this section in the final proposed change because itdescribes a non-limiting case (i.e., it is bounded by the sample line break). Discussion ofthe RNS heat exchanger tube leak has been incorporated into Appendix 19E, Section19E.2.5. The revision proposed to DCD Section 19E.2.5 is included below for reference.

2. The CCS surge tank line vent / overflow line was increased in size from 2" to 3" to eliminatethe potential for over-pressurizing the surge tank (designed as an atmospheric tank) in theevent of a large RNS heat exchanger tube leak that causes a significant increase in liquidvolume in the CCS. The basis for the increase in surge tank vent line size is described inthe proposed revision to DCD Section 9.2.2.3.3 provided below.

3. The maximum flow rate possible as a result of a double-ended break of one RNS heatexchanger tube is slightly more than 500 gpm. The large relief valve on the RNS heatexchanger cooling water line discharges to the Radioactive Waste Drain System (WRS)Auxiliary Building Equipment and Floor Drain sump at elevation 66' 6". This sump ispumped to the Waste Holdup Tank by two air-driven sump pumps, each of which has anominal capacity of 125 gpm. In the event that the relief valve discharges continuously for

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an extended period of time, the WRS Floor Drain Sump may overflow into the 66'6" level ofthe Auxiliary Building. Section 3.4.1.2.2.2 in Tier 2 of the DCD describes Auxiliary Buildingflooding events. In the radiologically controlled area of the first level (elevation 66'6") thereare no safe shutdown components and the maximum flood elevation has been determinedto be 12 inches or less, assuming that the flooding is identified and isolated within 30minutes.

Design Control Document (DCD) Revisions:

9.2.2.3.3 Component Cooling Water Surge Tank

The component cooling water system has a single surge tank. The surge tank accommodates changes incomponent cooling water volume due to changes in operating temperature. During normal operation, thetank is designed to accommodate 50 gallons per minute leakage into or out of the system for 30 minutesbefore any operator action is required. For abnormal operation, the surge tank vent line is sized toaccommodate a double ended tube rupture in the RNS HX (i.e., 520 gpm) without exceeding the surgetank design pressure or allowing pressure to increase above CCS system design pressure at the highestpressure point in the system.

The tank is a cylindrical, vertical unit constructed of carbon steel.

19E.2.5 Component Cooling and Service Water Systems

..he AP.OO ---.. . .yt and c.mpone.t c.ling water s...... ar. de.. e..be.d in-:.ub•co- 9.2. I and 9-2.2 -pCcieS:'e,'.

Two different means are provided to protect the lower-pressure CCS from oveWressure if RNSheat exchanger tube leakage occurs during plant cooldown or shutdown operations.

A relief valve is located on the CCS cooling water line inside the upstream and downstreammanual isolation valves for each RNS heat exchanger. The valve satisfies requirements inSection VIII of the ASME code for overpressure protection of heat transfer equipment. This reliefvalve provides both thermal overpressure and tube leakage protection in the event that the sectionof piping containing the RtNS heat exchanger is isolated from the remainder of the CCS. The valvedischarges directly into the auxiliary building sump.

If RNS heat exchanver tube leakage occiurs with the affected heat exchanger not isolated friom theCCS. the excess volune added to the CCS by the leak will begin to fill the CC S surge tank. If theCCS surge tank fills before the leak is isolated, fluid is discharged through the tank vent into the

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API1000 TECHNICAL REPORT REVIEW


turbine building sump to prevent over-pressurization of any portion of the CCS. Leakage into thesystem will produce a CCS liquid radiation monitor alami, and an increase in CCS surge tanklevel that results in a tank high level alann.

Doses firom the RNS heat exchanger tube nipture event would be below those produced by thepvimarv samole line break outside containment with the plant at power.

PRA Revision:None

Technical Report (TR) Revision:None

( WestinghouseRAI-DCP-CN06-SBP-01

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Question:

The NRC has completed its review of the final information on proposed changes for the AP1 000Design Control Document (DCD), Revision 18, dated April 26, 2010 and have the followingquestions to change number 9 related to the component cooling water (CCS) system.

Change #9

1. The description of the design change included a statement which stated, "Eliminatethe RNS heat exchanger relief valve discharge lines from thermal relief valveheader". This statement needs further explanation under "Description of change toDCD/Reason for change to DCD," since the thermal relief valve header was notpreviously described or shown on DCD Figure 9.2.2-2, Sheet 3.


The "Eliminate the RNS ... " statement should be replaced with "Larger pressure relief valves

have been added to the component cooling water system."

The reason for this design change is further clarified by:

The original (1" x 1") thermal relief valves provided for the RNS and SFS heat exchangers wereintended to discharge to the floor of the CCS valve room, where the discharge would becollected by a nearby floor drain. Now that much higher capacity relief valves are needed forthe RNS heat exchanger cooling water lines to meet ASME VIII equipment overpressureprotection requirements, the larger valves needed for the RNS heat exchanger (V302A/B) arepiped to a dedicated drain collection funnel located in the valve room to minimize the potentialrelease of large quantities of vapor and water spray to the room in the event that a high capacitydischarge occurred. The smaller valves (V342A/B) are also provided with their own collectionheader that discharges near the existing room floor drain. These changes are shown in therevised Sheet 3 of DCD Figure 9.2.2-2.

Design Control Document (DCD) Revision:(See revised Sheet 3 of DCD Figure 9.2.2-2 attached.)

PRA Revision:None


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Question:

Based on a review of the proposed changes for the AP1 000 Design Control Document (DCD),Revision 18, additional information is needed to address the following considerations related tochange number 45 for section 5.2.5, "Reactor Coolant Pressure Boundary Leakage Detection"

1. The operating experiences at Davis Besse (NRC Bulletin 2002-01) indicated that prolongedlow-level unidentified reactor coolant leakage inside containment could cause materialdegradation such that it could potentially compromise the integrity of a system leading to thegross rupture of the reactor coolant pressure boundary. The question was raised regardingpractices for identifying and resolving degradation of the reactor coolant pressure boundary.Pursuant to 10 CFR Part 52.79 Item 37, "information necessary to demonstrate howoperating experience insights have been incorporated into the plant design," the applicant isrequested to address this issue.

This issue could be addressed by operating procedures. The procedures would specifyoperator actions in response to prolonged low level unidentified reactor coolant leakageconditions that exist above normal leakage rates and below the Technical Specification (TS)limits to provide operator sufficient time to take actions before the TS limit is reached. Theprocedures would include identifying, monitoring, trending, and repairing prolonged low-levelleakage. The guidance about developing such procedures for ensuring effectivemanagement of leakage, including low-level leakage, is available in Regulatory Guide 1.45,Revision 1 (dated May 2008), "Guidance on Monitoring and Response to Reactor CoolantSystem Leakage," Regulatory Position C3, "Operations-Related Positions."

In the DCD, the applicant is requested to clarify whether it will commit to the aboveprocedure guidance, or a proposed alternative. If it is an alternative, the applicant shouldprovide its description. In the DCD, the applicant should either provide such procedures oridentify COL information items for the COL applicants to develop such procedures.

2. In order to support the procedures described in RAI Question 1 above, the applicant isrequested to define the alarm setpoints and demonstrate that the setpoints are sufficientlylow to provide an early warning for operator actions prior to Technical Specification limits. Inaddition, the applicant is requested to provide procedures for converting the instrumentoutput to a common leakage rate.

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These issues are programmatic in nature and should be addressed by the COL Applicant. Assuch, WEC will include an appropriate COL Information Item in the DCD as shown in the DCDRevision section below.

Design Control Document (DCD) Revision:

DCD Tier 2, Chapter 1, Table 1.8-2, will be revised to add a new COL information item to read:5.2-3 Response to Unidentified 5.2.6.3 NA Yes --

Reactor Coolant SystemLeakage Inside Containment

DCD Chapter 5, will be revised to add a new Subsection 5.2.6.3 to read:5.2.6.3 Response to Unidentified Reactor Coolant System Leakage Inside ContainmentThe Combined License applicant will provide information to address prolonged low-levelunidentified reactor coolant leakage inside containment which could cause material degradationsuch that it could potentially compromise the integrity of a system leading to the gross rupture ofthe reactor coolant pressure boundary. This issue could be addressed by operating procedures.The procedures should address operator actions in response to prolonged low level unidentifiedreactor coolant leakage conditions that exist above normal leakage rates and below the TechnicalSpecification (TS) limits to provide operator sufficient time to take actions before the TS limit isreached. The procedures should address identifying, monitoring, trending, and repairingprolonged low-level leakage. The procedures should also define the alarm setpoints anddemonstrate that the setpoints are sufficiently low to provide an early warning for operator actionsprior to Technical Specification limits. In addition, the procedures should address converting theinstrument output to a common leakage rate.

PRA Revision:None


O Westinghouse

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Question:

The NRC has completed its review of the final information on proposed changes for the AP1000Design Control Document (DCD), Revision 18, dated May 10, 2010 and have the followingquestions to change number 59.

The Westinghouse Description of Design Change states the following: "Duct the radiatorexhaust to the outside through hurricane louvers, and provide recirculation bypass to control theroom temperature."

This design change description appears to be inconsistent with the revised DCD text describingthe removal of diesel generator heat from the room. The proposed revision to Subsection9.4.2.2.1.5, "Mechanical Equipment Areas HVAC Subsystem," is as follows, "Ventilation andcooling for the room when the ancillary diesel generators operate is provided by means ofmanually operated dampers and opening doors to allow radiator discharge air to be exhausteddirect to outdoors airflow through the radiator, which is discharged outdoors."

The ducting of radiator exhaust described in the Description of Change appears to have beendeleted from the DCD description and there is no mention of the recirculation bypass feature inthe DCD description. The DCD description suggests that the heat from the radiator isdischarged to the room and then released from the room via a louver/damper in the outside walland by opening the doors to the room. In addition, the description does not mention hurricanelouvers.

The Description of Change also states: "Extend exhaust ductwork to new fuel tank location."This change is not clearly described in the DCD description. Is this the exhaust from the room,the diesel engine, or the diesel radiator? How does this change impact room and/or dieselcooling? Has an analysis been performed to demonstrate that this approach to dieselgenerator heat removal will not impact the operation of the diesel generator or exceed thedesign maximum room temperature for the diesel generator package?

The applicant should provide consistent and sufficient design description to clarify the designchanges.


The ancillary diesel(s) are cooled during engine operation as follows:

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" The exterior doors are opened to provide a path for cooling air to enter into the ancillarydiesel generator room.

" The diesel generator radiator fan takes air from the ancillary generator room and forces itthrough the radiator

" The diesel generator radiator discharge is ducted to a back draft damper, and then to adischarge (hurricane) louver

" The air from the discharge louver exhausts to the outside environment.

There is a manual damper in the exhaust ducting from the radiator to the discharge louver. Thismanual damper is opened only during cold weather operation. Opening this damper, along withpositioning the exterior doors, can be used to control room temperature in cold weather.

The exhaust louvers downstream of the ancillary generator radiators have been designed ashurricane louvers as a form of investment protection for the generators. The doors to theancillary generator room are also to be designed to withstand hurricanes. Although not calledout directly in the design documents, it is Westinghouse's opinion that it is very unlikely that ahurricane would be passing through the plant area 72 hours to 7 days after a combined Loss ofOffsite Power (LOOP) and failure of both auxiliary generators. In the event that a hurricanecauses a loss of offsite power and loss of the two auxiliary generators, the ancillary generatorsdo not need to run until 72 hours after the incident, by which time the storm will have left thearea, and there will be no need to open the doors for generator ventilation during the hurricane.

The exhaust duct that is extended to the new fuel tank location is the duct that is connected toVXS exhaust fan MA 12. The duct is relocated to exhaust from the fuel tank location to ensurethat the spread of fuel vapors is minimized. This exhaust fan, along with the normal HVACsupply is used to maintain the room design temperature when the ancillary diesel generator(s)are not running. The exhaust ducting change has minimal impact on the room cooling. Further,it will have no measurable impact on the room conditions when the ancillary diesel generator(s)are running.

Design Control Document (DCD) Revision:The last sentence of DCD 9.4.2.2.1.5 will be revised from

Wentilation and cooling for the room when the ancillary diesel generators operate isprovided by means of manually operated dampers and opening doors to allow airflowthrough the radiator which is discharged outdoors."

to

"Ventilation and cooling for the ancillary diesel generator room when the dieselgenerators operate is provided by opening the doors to allow airflow into the room. Airfrom the ancillary diesel generator room is exhausted to the outdoors through the diesel

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generator radiator(s), ducting, back draft damper(s), and hurricane louvers. There is amanual damper in the duct downstream of each diesel radiator that discharges air intothe room. This manual damper can be used to control room temperature in coldweather."

PRA Revision:None


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Documents

Westinghouse Electric Company, Response to RAI …RAI-DCP-CN06-SBP-01 RAI-DCP-CN09-SBP-01 RAI-DCP-CN45-SBP-01 RAI-DCP-CN59-SBP-01 Questions or requests for additional information related