NL-12-0872, Response to NRC Request for Additional Information for License Amendment Request to Revise Technical Specification 3.7.9 Ultimate Heat Sink (UHS)

Response to NRC Request for Additional Information for License Amendment Request to Revise Technical Specification 3.7.9 Ultimate Heat Sink (UHS)

ML121220296
Person / Time
Site:	Vogtle
Issue date:	04/30/2012
From:	Ajluni M Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-12-0872
Download: ML121220296 (9)

Text

Mark J. Ajiuni, P.E. Southern Nuclear Nuclear Licensing Director Operating Company, Inc.

40 Inverness Center Parkway Post Office Box 1295 Birmingham, Alabama 35201 Tel 205.992.7673 Fax 205.992.7885 SOUTHERN £r COMPANY April 30, 2012 Docket Nos.: 50-424 NL-12-0872 50-425 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant, Units 1 and 2 Response to NRC Request for Additional Information for License Amendment Request to Revise Technical Specification 3.7.9 Ultimate Heat Sink (UHS)

Ladies and Gentlemen:

By letter dated September 1, 2011 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML112450171), Southern Nuclear Operating Company (SNC) submitted a license amendment request for revision of Technical Specification (TS) 3.7.9 "Ultimate Heat Sink (UHS)."

Subsequently, by letter dated January 11, 2012 (ADAMS Accession Number ML11355A007), the NRC submitted a Request for Additional Information (RAI) to enable completion of the review. The responses to RAIs 2, 4, and 5 were provided by letter dated February 10, 2012. The responses to RAIs 1, 3, and 6 was scheduled to be provided by April 30, 2012. Enclosure 1 to this letter contains response to RAI-6. Enclosure 2 supports the response to RAI 6(b).

Investigation for the remaining RAI responses to RAI-1 (a), RAI- (b), and RAI-3 indicate that an additional calculation revision will be necessary to provide the desired basis for the responses and those responses are scheduled to be provided by August 1, 2012. Please note that the additional calculation revision has the potential to impact the proposed TS Figure 3.7.9-1 provided in the submittal of September 1, 2011.

U. S. Nuclear Regulatory Commission NL-12-0872 Page 2 Mr. M. J. Ajluni states he is Nuclear Licensing Director of Southern Nuclear Operating Company, is authorized to execute this oath on behalf of Southern Nuclear Operating Company and to the best of his knowledge and belief, the facts set forth in this letter are true.

This letter contains no NRC commitments. If you have any questions, please contact B. D. McKinney at (205) 992-5982.

Respectfully submitted, M. J. Ajluni Nuclear Licensing Director Sworn to and subscribedbefore me this _3 0 day of /9 /',E " ,2012.

Notary Public My commission expires: d4/"/),

MJA/JLS

Enclosures:

1: Response to Request for Additional Information 2: Figure A-1 of Calculation X4C1202S31 Version 3 "NSCW Ultimate Heat Sink Evaluation of Various Wet-Bulb and Basin Temperatures to Required Number of Fans" cc: Southern Nuclear Operatingq Company Mr. S. E. Kuczynski, Chairman, President & CEO Mr. D. G. Bost, Executive Vice President & Chief Nuclear Officer Mr. T. E. Tynan, Vice President - Vogtle Mr. B. L. Ivey, Vice President - Regulatory Affairs Mr. B. J. Adams, Vice President - Fleet Operations RType: CVC7000 U. S. Nuclear Regulatory Commission Mr. V. M. McCree, Regional Administrator Mr. P. G. Boyle, NRR Senior Project Manager - Vogtle Mr. L. M. Cain, Senior Resident Inspector - Vogtle State of Georgia Mr. J. H. Turner, Environmental Director Protection Division

Vogtle Electric Generating Plant, Units 1 & 2 Response to NRC Request for Additional Information for License Amendment Request to Revise Technical Specification 3.7.9 Ultimate Heat Sink (UHS)

Enclosure 1 Response to Request for Additional Information to NL-12-0872 Response to Request for Additional Information

RAI-1

Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.36, Technical Specifications (TSs), requires that a Limiting Conditions for Operation (LCO) be established for a structure, system, or component that is part of the primary success path and which functions or actuates to mitigate a design basis accident or transient that either assumes the failure of or presents a challenge to the integrity of a fission product barrier. A loss of offsite power (LOSP) is one such transient that must be considered.

With respect to a LOSP, the current LCO for Technical Specification 3.7.9, "Ultimate Heat Sink" (UHS), (submitted April 26, 2004, Agency wide Documents Access and Management System (ADAMS) Accession No. ML0411190306, with request for additional information (RAI) response dated April 18, 2005, ADAMS Accession No. ML051110207), accounts for a tornado induced LOSP where a missile strike damages one Nuclear Service Cooling Water (NSCW) cooling tower cell and makes it inoperable. In the License Amendment Request (LAR) dated September 1, 2011 (ADAMS Accession No. ML112450171), the licensee states that loss of an NSCW fan due to tornado is for LOSP only - not for Loss of Coolant Accident (LOCA). The Nuclear Regulatory Commission (NRC) staff concurs, but notes that the current TS LCO conservatively accounts for a LOSP, even though LOCA heat loads were used in the analysis.

In the LAR, Southern Nuclear Operation Co., Inc. (the licensee) presented new Figure 3.7.9-1, which proposes new NSCW cooling tower fan requirements as a function of wet bulb temperature and NSCW basin temperature. This figure is based on the calculation in Enclosure 5 of the LAR. Enclosure 5 calculates UHS fan requirements using plant heat rejection rates for LOCA. However, the NRC staff does not see justification for Figure 3.7.9-1 in the LAR for a tornado induced LOSP where an additional fan cell is lost due to missile strike. The NRC staff concurs with the licensee that plant heat rejection rates for LOCA does not apply to a tornado induced LOSP, but plant heat loads for shutdown with loss of offsite power do apply. (Note the hot standby heat loads for LOSP in Enclosure 6 of the LAR are not applicable here). The NRC staff notes that Final Safety Analysis Report (FSAR) Table 9.2.5-10 provides NSCW heat loads for shutdown with LOSP.

a) Please provide justification for the proposed LCO of the LAR using heat loads for shutdown with LOSP, where only three NSCW cooling tower fans would be available to mitigate a tornado induced LOSP when operating in the four fan/spray cell required region of Figure 3.7.9-1.

b) Please provide justification for the proposed LCO of the LAR using heat loads for shutdown with LOSP, where only two NSCW cooling tower fans would be available to mitigate a tornado induced LOSP when operating in the three fan/spray cell required region of Figure 3.7.9-1.

SNC Response to RAI-1 (a)

To provide the desired basis for response to request for information RAI-1 (a) will require generation of a calculation revision. The response to RAI-1 (a) is scheduled to be provided by August 1, 2012.

El-1 to NL-12-0872 Response to Request for Additional Information SNC Response to RAI-1(b)

To provide the desired basis for response to request for information RAI-1 (b) will require generation of a calculation revision. The response to RAI-1 (b) is scheduled to be provided by August 1, 2012.

RAI-3

The licensee has presented a justification in the LAR to increase the completion time (CT) to seven days for restoring a fan to operable status as described in proposed new Condition B.

The licensee's justification states:

Current analysis demonstrates that when four fans/spray cells are required by proposed TS Figure 3.7.9-1, three running fans and associated spray cells would mitigate the most likely transient of a LOSP. Being able to mitigate a LOSP during the proposed seven-day Completion Time provides additional assurance that the NSCW system will provide the needed cooling function. Enclosure 6 is a calculation that supports the proposed change in Completion Time by the conclusion that a Loss of Offsite Power transient can be mitigated with three fans/spray cells in operation.

However, Enclosure 6 uses heat loads to hot shutdown and not total NSCW heat loads for shutdown with loss of offsite power as shown in Table 9.2.5-10 of the FSAR. If a LOSP occurs, it may be necessary to shutdown to Mode 5, which has not been accounted in Enclosure 6.

Please provide adequate justification for your conclusion that a LOSP transient can be mitigated with three fans/spray cells in operation when operating in proposed Condition B.

SNC Response to RAI-3 To provide the desired basis for response to request for information RAI-3 will require generation of a calculation revision. The response to RAI-3 is scheduled to be provided by August 1, 2012.

RAI-6

The licensee is requesting to extend the CT from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to seven days to restore operability of one NSCW cooling tower after one required fan/spray cell became inoperable. One of the licensee's justifications for this extension is the availability of the other operable NSCW cooling tower (assuming no single failure during the CT) for a design basis accident (DBE).

a) Discuss the possible single failures that could render the operable NSCW cooling tower inoperable or ineffective during a DBE should it occur during the CT, e.g. loss of the associated EDG, loss of a nuclear service water pump, etc. Discuss the compensatory measures that will be enacted during the CT that will reduce the possibility of loss of operability or effectiveness of the redundant operable NSCW cooling tower.

El -2 to NL-12-0872 Response to Request for Additional Information b) If the redundant operable NSCW cooling tower was lost during the extended CT for a DBE as discussed above, discuss the resultant max basin temperature of the other and only remaining cooling tower (cooling tower for which the seven day CT was entered) which has the remaining three fans.

SNC Response to RAI-6(a)

1) While single failures that could render the operable NSCW cooling tower inoperable or ineffective during a design basis accident are beyond design basis and are not assumed for the proposed TS change, those possible single failures are:

" Failure of the operable cooling tower's train EDG in conjunction with a LOSP would render that tower inoperable since there would be no motive energy to drive that train's NSCW pumps, fans, or valves.

" Failure of the operable cooling tower spray valve (failing closed) would result in loss of function of the operable train.

The following situations as identified in FSAR Table 9.2.1-1 were also reviewed, even though they do not render an entire cooling water tower inoperable:

" Assuming the single failure was loss of one NSCW pump in the operable train, this condition would reduce the redundancy for that train but would not result in a loss of function. Since there are three 50% pumps in a NSCW train, loss of one pump does not result in a loss of function.

" Assuming the failure of a tower blowdown control valve to close (stays in the open position), the condition would result in an insignificant (approximately 30-minute) loss of inventory, and blowdown can be isolated by manual valves.

" Failure of the supply and/or return motor operated valves associated with the containment coolers, which receive a safety injection signal to open, would result in a loss of function for two out of the four containment coolers, but NSCW system operation would not be adversely affected.

" Failure of the supply and/or return motor operated valves associated with the auxiliary containment air cooler and the reactor cavity cooler, which receive a safety injection signal to close, would not adversely affect NSCW system operation.

2) Compensatory measures that will be enacted during the CT that will reduce the possibility of loss of operability or effectiveness of the redundant operable NSCW cooling tower include verifying the applicable unit's NSCW trains and emergency diesel generators are operable and that there is no schedule work that would make a NSCW train or an emergency diesel generator inoperable, and that no planned maintenance will be performed on NSCW fans/spray cells when in Condition B of Technical Specification 3.7.9 and imminent inclement weather is forecasted.

El -3 to NL-12-0872 Response to Request for Additional Information SNC Response to RAI-6(b)

The basin temperature profile of this beyond design basis case was plotted (see Enclosure 2, Figure A-1 from calculation X4C1202S31 Version 3). The peak basin temperature of 99.9 OF occurs approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the accident. The duration of basin temperature above 95 OF is approximately 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />.

El -4

Vogtle Electric Generating Plant, Units 1 & 2 Response to NRC Request for Additional Information for License Amendment Request to Revise Technical Specification 3.7.9 Ultimate Heat Sink (UHS)

Enclosure 2 Figure A-1 of Calculation X4C1202S31 Version 3 "NSCW Ultimate Heat Sink Evaluation of Various Wet-Bulb and Basin Temperatures to Required Number of Fans" to NL-12-0872 Figure A-1 of Calculation X4C1202S31 Version 3 "NSCW Ultimate Heat Sink Evaluation of Various Wet-Bulb and Basin Temperatures to Required Number of Fans" Southern Nuclear Design Calculation Plant: Calculation Number: Sheet:

Vogtle Units I &2 X4C1202S31 A-2 Appendix A: UHS Basin Temperature for Beyond Design Basis Case Figure A-I Basin Temperature Profiles for Beyond Design Basis Case Basin Temperature (Deg. F) 0 O CO 00Y 0 W, O 0

(I Cn D 0) 1 0

00 (0o N) 0 0) 0 NMP-ES-039- F02 NMP-ES-039-001 E2-1