ML11355A007
| ML11355A007 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 01/11/2012 |
| From: | Patrick Boyle Plant Licensing Branch II |
| To: | Ajluni M Southern Nuclear Operating Co |
| Boyle P | |
| References | |
| TAC ME7105, TAC ME7106 | |
| Download: ML11355A007 (5) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555"()001 January 11, 2012 Mr. M. J. Ajluni Nuclear Licensing Director Southern Nuclear Operating Company, Inc.
40 Inverness Center Parkway Post Office Box 1295, Bin - 038 Birmingham, AL 35201-1295
SUBJECT:
VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION, REVISION OF TECHNICAL SPECIFICATION LIMITING CONDITION FOR OPERATION 3.7.9 "ULTIMATE HEAT SINK" FOR VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 (TAC NOS.
ME7105AND ME7106)
Dear Mr. Ajluni:
By letter dated September 1, 2011 (Agencywide Documents Access and Management System Accession No. ML112450171), Southern Nuclear Operating Company, Inc. (SNC, the licensee),
submitted a license amendment request to change the Technical Specifications (TSs) for Vogtle Electric Generating Plant (Vogtle), Units 1 and 2. The amendment would revise the TS Limiting Condition for Operation 3.7.9 "Ultimate Heat Sink." The proposed changes involve revising the criteria for the Nuclear Service Cooling Water tower three and four fan operation. These proposed changes include an increase in the wet bulb temperature limit for three fan operation and addition of a Condition that allows a seven-day Completion Time for a specified situation.
Responses to the enclosed request for additional information (RAI) are needed for us to continue our review.
Please provide a response within thirty (30) calendar days of the date of this letter.
Sincerely, 7':-rJ,A '/l
. A, v' {l( ~'I-
~ f:J;;;-y--
Patrick G. Boyle, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-424 and 50-425
Enclosure:
RAJ cc w/encl: Distribution via Listserv
REQUEST FOR ADDITIONAL INFORMATION VOGTLE ELECTRIC GENERATING PLANT. UNITS 1 AND 2 LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATION 3.7.9 ULTIMATE HEAT SINK DOCKET NO. 50-424 AND 50-425
RAI-1
- 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, Agencywide Documents Access and Management System (ADAMS) Accession No. ML041190306, 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.
Enclosure
- 2 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.
RAI-2
2 The licensee has previously stated in their April 18, 2005, response to a NRC RAI that three fans supported acceptable temperature limits (Le., basin temperature < 95 degrees Fahrenheit (OF>> for emergency cooling for LOCA when ambient wet bulb temperature is a maximum of 67 of. The licensee in their September 1 r 2011, submittal now states that a maximum ambient wet bulb temperature of 73 of is sufficient to keep basin temperature
< 95 of with three fans running for LOCA. The licensee stated that this is a result of a new engineering calculation. The licensee has proposed changing the corresponding Condition LCO according to the new engineering calculation. Explain why the maximum wet bulb temperature limit considering LOCA is proposed to change from 67 of to 73 of, including what has changed between the April 18, 2005 submittal and the September 1, 2011, submittal.
RAI-3
- 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. 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.
RAI-4
- 4. The licensee has proposed compensatory measures as provision for extending the CT to seven days when in Condition B. Some of the proposed compensatory measures are unquantifiable and cannot be identified. Measures such as "additional oversight," "other safety significant components," cannot be measured or enforced.
- 3 a) It is unclear how "additional oversight" for the switchyard, emergency diesel generators (EDG), and auxiliary feed water pumps will be determined and validated. Please explain.
b) It is unclear what safety significant components will not have planned maintenance during NSCW fan repair. Please explain.
c) How will you ensure that both emergency EDG's and both NSCW trains are verified operable when in Condition B?
RAI5
- 5. The licensee has made a regulatory commitment in Enclosure 4. The NRC staff has the following concerns regarding this regulatory commitment:
a)
The Regulatory Commitment in Enclosure 4 can be applicable when inclement weather is forecasted. Please define inclement weather for the purposes of implementing this Regulatory Commitment.
b)
Does planned maintenance make a fan inoperable? If so, how does this Regulatory Commitment add safety when you could not make a second fan inoperable and remain in Condition B? If planned maintenance would not make the fan inoperable, then how are you enhancing safety by not performing this maintenance?
RAI6
- 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.
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.
January 11, 2012 Mr. M. J. Ajluni Nuclear Licensing Director Southern Nuclear Operating Company, Inc.
40 I nverness Center Parkway Post Office Box 1295, Bin - 038 Birmingham, AL 35201-1295
SUBJECT:
VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 - REQUEST FOR ADDITIONAL INFORMATION, REVISION OF TECHNICAL SPECIFICATION LIMITING CONDITION FOR OPERATION 3.7.9 "ULTIMATE HEAT SINK" FOR VOGTLE ELECTRIC GENERATING PLANT, UNITS 1 AND 2 (TAC NOS.
ME7105AND ME7106)
Dear Mr. Ajluni:
By letter dated September 1, 2011 (Agencywide Documents Access and Management System Accession No. ML112450171), Southern Nuclear Operating Company, Inc. (SNC, the licensee),
submitted a license amendment request to change the Technical Specifications (TSs) for Vogtle Electric Generating Plant (Vogtle), Units 1 and 2. The amendment would revise the TS Limiting Condition for Operation 3.7.9 "Ultimate Heat Sink." The proposed changes involve revising the criteria for the Nuclear Service Cooling Water tower three and four fan operation. These proposed changes include an increase in the wet bulb temperature limit for three fan operation and addition of a Condition that allows a seven-day Completion Time for a specified situation.
Responses to the enclosed request for additional information (RAI) are needed for us to continue our review.
Please provide a response within thirty (30) calendar days of the date of this letter.
Sincerely, IRA!
Patrick G. Boyle, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-424 and 50-425
Enclosure:
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