ML103140373

2010/10/28 Watts Bar 2 OL - Draft Watts Bar Unit 2 RAI on Chapter 8 Open Items

ML103140373
Person / Time
Site:	Watts Bar
Issue date:	10/28/2010
From:	Office of Nuclear Reactor Regulation
To:	Division of Operating Reactor Licensing
References
Download: ML103140373 (8)

Text

1 WBN2Public Resource From: Poole, Justin Sent: Thursday, October 28, 2010 4:25 PM To: Crouch, William D Cc: WBN2HearingFile Resource

Subject:

DRAFT Watts Bar Unit 2 RAI on Chapter 8 Open Items Attachments:

DRAFT Request for Additional Information - EEEB - October 2010.docxBill, Attached, for your review, are preliminary Request for Additional Information (RAI) questions regarding Watts Bar Nuclear Plant (WBN), Unit 2. Please review to ensure that the RAI questions are understandable, the regulatory basis is clear, there is no proprietary information contained in the RAI, and to determine if the information was previously docketed. Please also let me know how much time Tennessee Valley Authority (TVA) needs to respond to the RAI questions.

JustinC.PooleProjectManagerNRR/DORL/LPWBU.S.NuclearRegulatoryCommission(301)4152048email:Justin.Poole@nrc.gov Hearing Identifier: Watts_Bar_2_Operating_LA_Public Email Number: 165 Mail Envelope Properties (19D990B45D535548840D1118C451C74D6FD37245A6)

Subject:

DRAFT Watts Bar Unit 2 RAI on Chapter 8 Open Items Sent Date: 10/28/2010 4:24:35 PM Received Date: 10/28/2010 4:24:58 PM From: Poole, Justin Created By: Justin.Poole@nrc.gov Recipients: "WBN2HearingFile Resource" <WBN2HearingFile.Resource@nrc.gov>

Tracking Status: None "Crouch, William D" <wdcrouch@tva.gov> Tracking Status: None Post Office: HQCLSTR02.nrc.gov

Files Size Date & Time MESSAGE 643 10/28/2010 4:24:58 PM DRAFT Request for Additional Informatio n - EEEB - October 2010.docx 26734 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date: Recipients Received:

SER Section 8.1, General

1. For scenario with an accident one unit and spurious ESF actuation in the other unit with offsite power, TVA stated that there is no design requirement per the FSAR when supplied from off-site power. TVA also stated that the auxiliary power system and supporting analysis complies with the requirements of position C.2.b of RG 1.81.

Therefore, analysis with one unit in accident and the spurious actuation of ESF loads in the second unit has not been performed.

The staff noted that the design criteria provided in SRP Section 8.2, Part III.9 (April 1978) requires the staff to evaluate the capability of preferred power system for spurious or false accident signals (i.e., should not overload the preferred power source circuits). Provide this analysis for the staff to review.

2. For scenario with a dual-unit trip as a result of an abnormal operational occurrence in accordance with GDC 17, the applicant did not provide any specific analysis to conclude that both offsite and onsite power systems have adequate capacity and capability.

Provide this analysis for the staff to review.

SER Section 8.2.1, Compliance with GDC 5

1. FSAR Section 8.2.2, "Analysis," stated that each 161 kV circuit and CSSTs C and D have sufficient capacity and adequate voltage to supply the essential safety auxiliaries of a unit under loss-of-coolant accident (LOCA) conditions concurrent with a simultaneous worst-case single transmission system contingency.

Provide clarification to show that the loads from the second unit were considered in this analysis.

2. TVA submitted selective excerpts from calculation WBN-EEB-EDQ000-999-2007-0002 for AC Power Systems Analyses, which evaluated plant loading conditions. This calculation assumed that the existing rating of CSST A and B will be upgraded from 57/76MVA OA/FA to a design rating of 95MVA (Primary-winding) and 60MVA (secondary & tertiary winding) by retrofitting with an additional cooling system.

Clarify whether the proposed change is essential to provide adequate capacity for the shared station service transformers to handle plant loads for all postulated conditions and schedule for completing this modification. Specifically, verify that each service transformer can supply the Class 1E power system for both units under all postulated design conditions including: (a) a design-basis accident with single failure on one unit and a spurious accident signal with full load rejection on the other unit and (b) a dual-unit shutdown due to abnormal operating occurrence.

8.2.2 Compliance

with GDC 17 and GDC 18

1. In view of the Unit 2 loads being applied to the CSSTs along with Unit 1 loads, the staff requested a summary of the calculations and analyses that detail the loading for both units (or added loads of Watts Bar Unit 2 to the existing loads of Unit 1), including the design margin in the CSSTs with a design-basis accident (DBA) in one unit and a concurrent shutdown of the other unit. showed that all operational configurations for offsite power supply to the units yield loadings well within the rating of the transformer with design margins from 10% to as high as 48%.

Provide a summary of similar margin studies based on scenarios as described below for CSSTs A, B, C, and D.

a. A dual-unit trip as a result of abnormal operational occurrence.

b. Accident in one unit and concurrent shutdown of the second unit (with and without offsite power). c. Accident in one unit and spurious engineered safety features (ESF) actuation in the other unit (with and without offsite power).

2. Provide the results of the grid stability analyses to indicate that loss of the largest capacity being supplied to the grid, loss of the largest load from the grid, loss of the most critical transmission line, or loss of both units themselves will not cause grid instability in accordance with specifications after trip of a station unit in accordance with GDC 17.

8.3.1.2, Low and/or Degraded Voltage Condition

1. Confirm that the analytical values for the degraded voltage settings will be suitably accounted in the final Technical Specifications

2. The loss-of-voltage relay lower time delay of 0.4 seconds may be too short for the transmission line protection to clear the short circuit fault. Confirm the longest time setting for the 161 kV transmission line protections to clear a short circuit fault (such as time setting in a second or third zone of distance protection) does not cause the actuation of the LOV relay.

8.3.1.11, Automatic Sequencing of Loads

Describe the resequencing of loads (with time delays involved) in the scenario of LOCA followed by Delayed LOOP and ensure that all loads will be sequenced within the time assumed in the accident analysis.

8.3.1.12, Bus Ratings/Connected Loads

Revise the wording in FSAR Section 8.3.1.1, which continues to state that the connected load and the maximum demand are shown in FSAR Tables 8.3-4 through 8.3.7 (which is contrary to TVA statement that these Tables describe the board/bus rating in kilovolt-ampere (kVA ) and do not represent the connected load or the maximum demand).

8.3.1.13, Standby Diesel Generator Operation In its explanation of "appropriate alignment" of the EDGs, TVA considered the scenario "a loss of offsite power and an accident" while in the FSAR the appropriate alignment refers to the scenario of "a loss of offsite power" only. Resolve this apparent discrepancy and explain the appropriate alignment in the FSAR based on the actual design of the Standby Diesel Generator Operation.

8.3.1.14, Adequacy of Diesel Generator Capacity

Provide the explanation or basis of the maximum transient rating indicated as 4785 kW (0 to 180 second) and 5073 kW (180 second to End), and maximum step load increase rating as 8000 kVA (0 second to End).

8.3.1.15, Underground Cables

Provide documentation that the cables are designed for submergence, or the measures provided in the raceways system are adequate to prevent submergence.

8.3.2.3, Availability of the Battery Supplies to Vital Instrument Buses

1. TVA provided a summary of the results of calculations used for determining the size of the inverters, battery chargers, batteries, and fuses.

Explain why load shedding is necessary if the battery has been sized appropriately. The battery sizing concern will remain open until the applicant can confirm that the vital batteries are sized adequately.

2. TVA stated that the design change notices (DCNs) are required or anticipated for completion of Watts Bar Unit 2 and that this is an unverified assumption.

Verification that the completion of the changes.

3. TVA stated that due to duty cycle limitation imposed by IEEE Standard 450-1995, Section 5.4, it has not developed a modified performance test duty cycle or an implementing procedure for Watts Bar. Based on this response, the staff considers this issue as open and finds that the modified performance discharge test is not approved for Unit 2.

4. Based on the duty cycle limitation imposed by IEEE Standard 450-1995, Section 5.4, TVA stated that it has not developed a modified performance test duty cycle or an implementing procedure for Watts Bar.

Provide the justification for not incorporating the duty cycle limitation.

5. In its 125 VDC battery system analysis, TVA assumed starting of safe shutdown of the non-accident unit at 30 seconds is conservative. In this analysis, Unit 1 has been assumed under DBA and Unit 2 as a non-accident unit. The assumption appears non-conservative because it does not consider a DBA and LOOP at one unit concurrent with LOOP at the other unit in which case the operation of some breakers would be

simultaneous. Explain the apparent nonconservatism.

8.3.3.2, Compliance with GDC 5

TVA credited selective coordination between protective devices to assure adequate protection of safety related dc systems from failures in non 1E circuits between common circuits or safety/nonsafety-related circuits. For circuits that have short circuit current above the instantaneous setting of successive devices, selective coordination may not be achievable. Clarify the coordination in the instantaneous region of the protective devices for such circuits.

8.3.3.2.1, Sharing of DC Distribution Systems and Power Supplies Between Units 1 and 2 Address the potential consequences of a spurious accident signal in the non accident unit concurrent with an accident in the other unit and a single failure.

Address the DC system capability for a dual-unit trip as a result of abnormal operational occurrence.

8.3.3.2.2, Sharing of AC Distribution Systems and Standby Power Supplies Between Units 1 and 2 Provide an evaluation for CCS and other shared systems regarding cross train single failures, one per each unit, that could can potentially disable header valves and restrict flow resulting in inadequate cooling for operating equipment.

8.3.3.2.4, Possible Sharing of DC Control Power to AC Switchgear

Confirmation that the requirement that all possible interconnections between redundant divisions through normal and alternate power sources to various loads be identified in FSAR Table 8.3-10 regardless of the source of power and will meet the staff's positions identified in Section 8.3.1.7 of the staff SER dated June 30, 1982. Also, confirm that redundant divisions are not cross-tied when both units are at power

8.3.3.3, Physical Independence (Compliance with GDC 17)

Associated Circuits Confirm that for those circuit breakers which are required to be tested periodically, the surveillance requirements for both items 8.3.3(2) and 8..3.3(3) have been provided in the Technical Requirements Manual.

8.3.3.4 , Compliance with NUREG-0737 Items

Emergency Power for Pressurizer Equipment (II.G.1)

Confirm that for Unit 2, the PORVs and block valves will be powered from different emergency power sources, (for example, PORV on dc power and the associated block valve on ac power), both power sources emanating from the same division, but different buses.

Emergency Power Supply for Pressurizer Heaters (II.E.3.1)

Confirm Watts Bar 2 design continues to meet the guidelines of Item II.E.3.1 of NUREG-0737.

8.4.1 , Station Blackout Duration TVA has referenced the documents (Design Criteria WB-DC-40-64 and WBN calculation EPMMA041592), which had not been submitted to the staff for review on the docket.

TVA should either submit the referenced documents to the staff for review or provide a summary of the results that pertain to the information requested in the RAI dated July 12, 2010. In RAI, the staff had requested TVA to validate and provide relevant information on the factors listed in 10 CFR 50.63 for determining specified coping duration to withstand and recover from an SBO, and the expected frequency of grid-related loss of offsite power in the last 20 years did not exceed once per 20 years at the

WBN Unit 2 site.

8.4.2.1, Condensate Inventory for Decay Heat Removal Resolve the differences in the information provided to the staff originally (submittal dated August 31, 1992) and the information provided in its response dated July 31, 2010, regarding CST and the amount of condensate required for a 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> coping duration.

8.4.2.2, Class IE Battery Capacity Clarify what analysis was used for the batteries in order to reach a conclusion that batteries have adequate capacity to achieve and maintain a safe shutdown and recover from an SBO for a 4-hour coping duration.

8.4.2.3, Compressed Air

Iit is not clear from TVA's response whether the completed modifications to install bottled nitrogen to supply TDAFWP LCVs were for both WBN Unit 1 and Unit 2, or just WBN Unit 1. Since WBN Unit 2 was not licensed after issuance of the staff final SE on SBO on September 9, 1993, TVA needs to confirm whether these modifications included WBN Unit 2.

8.4.2.5, Containment Isolation

Confirm that the original information submitted to the staff is applicable to the Watts Bar Unit 2, or provide additional information to ensure that valves which must be capable of being closed or operated (cycled) during an SBO event can be positioned (with indication) independent of the blacked-out unit's power supplies.

8.4.2.6, Reactor Coolant Inventory TVA needs to include the shrinkage due to cooldown in its assessment of the RCS inventory for an SBO of 4-hour coping duration. Also TVA needs to resolve the differences in the information provided to the staff originally (submittal dated August 31, 1992) and the information provided in its response to RAI dated July 31, 2010, regarding the amount required for 4-hour coping.

8.4.4, Proposed Modifications

TVA did not elaborate on whether the completed modifications to install bottled nitrogen to supply TDAFWP LCVs were for both WBN Unit 1 and Unit 2, or just WBN Unit 1 since WBN Unit 2 was not licensed after issuance of the staff final SE on SBO on September 9, 1993.

Confirmation that the modifications to install bottled nitrogen to supply TDAFWP LCVs for WBN Unit 2 have been completed, or will be completed before startup of WBN Unit 2.

8.4.5, Quality Assurance and Technical Specifications Plant procedures related to SBO will reflect the appropriate testing and surveillance requirements to ensure the operability of the necessary SBO equipment.

Provide an affirmation that the original commitment documented in its submittal of August 31, 1992, applies to WBN Unit 2.

8.4.6, EDG Reliability Program

Confirm that the 2 EDGs credited for WBN Unit 2 are covered under the guidelines of RG 1.155, Section 1.2, or NUMARC 87-00, Revision 1 , Appendix E to maintain their target reliability of 0.975.