ML12089A491

Response to NRC Second Request for Additional Information Regarding the Heavy Load Lifts and UHS One Time Change in Support of Unit 2 SGRP

ML12089A491
Person / Time
Site:	Sequoyah
Issue date:	03/05/2012
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME7225
Download: ML12089A491 (14)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 March 5, 2012 10 CFR 50.4 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Sequoyah Nuclear Plant, Unit 1 Facility Operating License No. DPR-77 Docket No. 50-327

Subject:

Response to NRC Second Request for Additional Information Regarding the Heavy Load Lifts and UHS One Time Change in Support of Unit 2 SGRP (TAC NO. ME7225)

Reference:

1. Letter from TVA to NRC, "Application to Revise Sequoyah Nuclear Plant, Unit 1, Operating License and Technical Specification 3.7.5, "Ultimate Heat Sink," to Support Sequoyah Nuclear Plant, Unit 2, Steam Generator Replacement Project (TS-SQN-2011-05)," dated September 29, 2011

2. Electronic Mail from NRC to TVA, "Sequoyah, Unit 1 LAR - Heavy Load Lifts and UHS One Time Change in Support of Unit 2 SGRP (TAC NO. ME7225)," dated January 13, 2012

3. Letter from TVA to NRC, "Response to NRC Request for Additional Information Regarding the Heavy Load Lifts and UHS One Time Change in Support of Unit 2 SGRP (TAC NO. ME7225), dated February 10, 2012

4. Electronic Mail from NRC to TVA, "Sequoyah, Unit 1 LAR - Heavy Load Lifts and UHS One Time Change in Support of Unit 2 SGRP (TAC NO. ME7225)," dated February 2, 2012 By letter dated September 29, 2011 (Reference 1), the Tennessee Valley Authority (WVA) submitted a one-time request for amendment to the Operating License (OL) for Sequoyah Nuclear Plant (SQN), Unit 1. The amendment request proposed to add a one-time license condition to the SQN, Unit 1, OL for the conduct of heavy load lifts Printed on recycled paper 7~c5~0

U.S. Nuclear Regulatory Commission Page 2 March 5, 2012 associated with the SQN, Unit 2, Steam Generator Replacement Project (SGRP).

The one-time license condition establishes special provisions and requirements for the safe operation of SQN, Unit 1, while large heavy load lifts are performed on SQN, Unit 2. In addition, a one-time change to SQN, Unit 1, Technical Specification (TS) 3.7.5, "Ultimate Heat Sink," is also proposed to implement additional restrictions with respect to maximum average Essential Raw Cooling Water System supply header water temperature during large heavy load lifts performed to support the SQN, Unit 2, SGRP.

By electronic mail dated January 13, 2012, (Reference 2), the NRC forwarded a request for additional information (RAI) regarding the proposed changes establishing the special provisions and requirements for large heavy load lifts on SQN, Unit 2.

TVA responded to this first RAI by letter dated February 10, 2012 (Reference 3).

Subsequently, in an electronic mail dated February 2, 2012, the NRC forwarded a second RAI regarding the proposed changes and requested a response within 30 days. The enclosure to this letter provides TVA's response to the second RAI. As discussed in the response to Question 2 of the enclosure to this letter, a change was made to Figure 6-1 of Enclosure 2 to the Reference 1 letter. No other changes have been made to the license amendment request of Reference 1 or to the first RAI response of Reference 3.

There are no regulatory commitments included in this submittal. If you have any questions, please contact Clyde Mackaman at (423) 751-2834.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 5th day of March 2012.

Res tfully, 4SheaCorporate Nuclear Licensing

Maager,

Enclosure:

Response to NRC Second Request for Additional Information Regarding the Heavy Load Lifts and UHS One Time Change in Support of Unit 2 SGRP cc (Enclosures):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Sequoyah Nuclear Plant Director, Division of Radiological Health, Tennessee State Department of Environment and Conservation

ENCLOSURE TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT UNIT 2 RESPONSE TO NRC SECOND REQUEST FOR ADDITIONAL INFORMATION REGARDING THE HEAVY LOAD LIFTS AND UHS ONE TIME CHANGE IN SUPPORT OF UNIT 2 SGRP NRC Question 1

Background:

Although they are simple schematics, Figures 6-1 and 8-2 both show the isolation boundary valve of the 2B essentialraw cooling water (ERCW) header (2-FCV-67-82) to be outside the boundary of the Auxiliary Building and adjacent to the potential drop zone.

Issue:

The application does not assume that the isolation function of the subject valve could potentially be impacted by the postulated drop; however, the valve is clearly shown to be outside of the Auxiliary Building and adjacent to the potentialdrop zone. Following a postulated drop, if 2-FCV-67-82 is, in fact, in the ERCW tunnel and could be affected by a heavy load drop, the isolation function would be negated and, via the cross-tie, the lB header would be discharging through the broken end of the 2B header. This would criticallychange flow and heat load calculationsin the cross-tied configuration andpotentially cause massive flooding of the ERCW tunnel.

Request:

Please provide a detailed description of the physical location of ERCW system valve, 2-FCV-67-82, with respect to the potentialdrop zone of a heavy load. If 2-FCV-67-82 is in the potential drop zone, describe how the ERCW 2B headerwill be isolated.

TVA Response Valve 2-FCV-67-82, along with its companion valve 2-FCV-67-81, are located at the entrance to the pipe tunnel from the Auxiliary Building. The valves are inside the pipe tunnel, but outside of the tunnel area to be enclosed by the temporary wall as shown on Figure 8-1 of Technical Report No. SQN2-SGR-TR1 submitted in Reference 1. These valves are outside of the postulated load drop zone. Figure 1 of this enclosure outlines the location of the valves with respect to the potential drop zone of a heavy load on Figure 6-2 of Technical Report No.

SQN2-SGR-TR1 submitted in Reference 1. Figures 2 and 3 of this Enclosure provide additional details of the valve locations as taken from SQN drawing nos. 1, 2-41 N700-2, "Concrete General Outline Features," and 1, 2-47W850-8, "Mechanical ERCW."

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NRC Question 2

Background:

The application refers several times to essential cross-tie valves with unique identifiers:

O-VLV-67-1610, -1611, -1612, and -1613. These valves are presumed to be shown (although not labeled as such) in Figures 6-1 and 8-2 on the 16-inch piping labeled as "Aux Bldg Header Crosstie."

Issue:

The subject valves are not shown on the latest UFSAR Figure 9.2.2-2 for the ERCW system, nor does the application identify them as temporarily installed equipment.

Request:

Please provide an explanation for the absence of the ERCW header cross-tie valves O-VLV-67-1610, -1611, -1612, and -1613 from UFSAR Figure 9.2.2-2. Also, provide an updated Figure 6-1 showing where these valves are located or accurately describe the location of these valves on Figure 6-1.

TVA Response The valves and cross-tie lines were installed under Design Change Request (DCN) 21894. The DCN indicated Updated Final Safety Analysis Report (UFSAR) Figure 9.2.2-2 was to be updated to include the changes. The UFSAR update for these DCN changes was not processed appropriately and, consequently, had not been incorporated into the UFSAR. TVA has taken the required actions to include this drawing revision in Amendment 24 to the UFSAR.

This issue was recorded in TVA's Corrective Action Program. of this enclosure provides a full size, updated UFSAR Figure 9.2.2-2 with the cross-tie valves indicated. Figure 4 of this enclosure provides an updated Figure 6-1 as requested, with the valve numbers for the cross-tie valves added to accurately depict their location.

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NRC Question 3

Background:

Due to the temporary alignment of the ERCW system to accommodate the mitigation strategy for the potential drop of a heavy load, the subject amendment requests to lower the required average water temperature of the ERCW system header from 87 degrees F to 74 degrees F.

This new temperature value is the result of a steady-state hydraulic analysis of the ERCW system.

Issue:

Although the resulting 74-degree F value is requested by the subject application,there is no description of the design inputs and assumptions of the calculationwhich determined this new number.

Request:

Please describe the changes in the design inputs and assumptions of the new hydraulic analysis from the currenthydraulic analysis. Explain why the maximum allowed ERCW system header temperaturechanges from 87 degrees F to 74 degrees F.

TVA Response The current hydraulic analysis provided the basis for the new hydraulic analysis.

For the new hydraulic analysis, the component alignments in the current hydraulic analysis were changed to represent the ERCW system alignment required to assure a safe shutdown of SQN, Unit 1 during Steam Generator Replacement Project (SGRP) activities on SQN, Unit 2. Thus, the new hydraulic analysis uses the same modeling methodology and calculation methods as the current hydraulic analysis and the design inputs and assumptions are consistent. As a result of the postulated heavy load drop described in the submittal (Reference 1 of the cover letter), a system alignment change for the prerequisite valve alignment was necessary due to the considerations for damage to the ERCW 'B' discharge piping. This change resulted in the need to lower the Ultimate Heat Sink temperature because of a worst case reduction in flow rate to the most limiting component of approximately 38 percent.

The results of the hydraulic calculation would not support the required flow rates for the full design basis Ultimate Heat Sink temperatures, so a thermal calculation change was prepared that determined the appropriate Ultimate Heat Sink limitation at which the required heat transfer/equipment cooling would be accomplished for the affected safety related components.

The calculations established that, for the ERCW system alignment required to assure a safe shutdown of SQN, Unit 1, during SGRP activities on SQN, Unit 2, the ERCW system can perform its safety function subject to a maximum ERCW supply temperature of 75.6 degrees F.

This was rounded down to 74 degrees F, for conservatism.

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NRC Question 4

Background:

Due to the temporary alignment of the ERCW system to accommodate the mitigation strategy for the potential drop of a heavy load, the subject amendment requests to lower the required average water temperatureof the ERCW system header from 87 degrees F to 74 degrees F.

Issue:

Quantifying the historicalaverage temperature of the water in the ERCW header will provide a benchmark by which the NuclearRegulatory Commission staff can establish a realisticmargin between the water temperature which will be technically requiredand that which is likely to be provided.

Request:

Please provide a summary of the last five years historicaldata which shows the actual, average temperature of the water in the ERCW header during the approximate time of year when the subject heavy load lifts are scheduled to be performed. (e.g. From OctoberXX to November XX of 20XX, the average temperatureof the ERCW header water was XX degrees. etc.)

TVA Response By the preliminary outage schedule, the unit shutdown will be on October 15, 2012. The core offload is scheduled to complete October 22, 2012, with the first heavy load lift soon thereafter.

The last heavy load lift is scheduled to completed by November 20, 2012. From October 15 to November 20, the average ERCW temperature as measured at the intake for the following years was:

YEAR AVERAGE TEMP 2011 63.4 degrees F 2010 64.0 degrees F 2009 63.9 degrees F 2008 63.9 degrees F 2007 65.8 degrees F In addition, Figure 5 of this Enclosure provides the historical SQN ERCW intake temperatures for the period of October 15 to November 20 for the years 1981 through 2011. This graph depicts the median, average, minimum, maximum, average minus standard deviation and average plus standard deviation temperatures of the water at the ERCW intake.

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FIGURE 1 Location of Valves with Respect to the Drop Zone Figure 6 Heavy Load Lifting Postulated Drop Zone Technklca Report No. SON2-SGR-TR I Page 53 of 9g E-5

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FIGURE 5 SEQUOYAH ERCW INTAKE TEMPERATURES 1981-2011 UPDATE 12/31111 80.00 78.00 76.00 74.00 72.00 70.00 68.00 -Median

.-.66.00 -Average 1-

- Minimum 62.00 Temp

-Maximum 60.00 Temp

-Average -

58.00 Std Dev

-Average +

56.00 Std Dev 54.00 52.00 50.00 C,,,

hDATp DATE J

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ATTACHMENT 1 UFSAR Figure 9.2.2-2 E-1O

(insertfull size UFSAR Figure 9.2.2-2)

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THIS PAGE IS AN OVERSIZED DRAWING OR FIGURE, THAT CAN BE VIEWED AT THE RECORD TITLED:

"FIGURE 9.2.2-2 ESSENTIAL RAW COOLING WATER SYSTEM (REVISED BY AMENDMENT 24)

WITHIN THIS PACKAGE D-01