ML11118A154

Request for Additional Information Regarding Completion Time Extension for TS 3.8.1 Required Action B.4 - Emergency Diesel Generators a, B, C, D, 3A, 3B, 3C, and 3D (TAC No. ME5036, ME5037, and ME5038)

ML11118A154
Person / Time
Site:	Browns Ferry
Issue date:	05/06/2011
From:	Gratton C Plant Licensing Branch II
To:	Krich R Tennessee Valley Authority
Gratton C
References
TAC ME5036, TAC ME5037, TAC ME5038
Download: ML11118A154 (6)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 6,2011 Mr. R. M. Krich Vice President, Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

BROWNS FERRY NUCLEAR PLANT, UNIT 1, 2, AND 3 - REQUEST FOR ADDITIONAL INFORMATION REGARDING COMPLETION TIME EXTENSION FOR TS 3.8.1 REQUIRED ACTION B.4 - EMERGENCY DIESEL GENERATORS A, B, C, D, 3A, 3B, 3C, AND 3D (TAC NOS. ME5036, ME5037, AND ME5038)

Dear Mr. Krich:

By letter dated November 12, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML103210334), as supplemented on February 8,2011 (ADAMS Accession No. ML110450256), Tennessee Valley Authority (the licensee) submitted a request for a Technical Specification change to extend the completion time for one diesel generator inoperable from 7 to 14 days.

Based on our review of your submittal and supplement, the U. S. Nuclear Regulatory Commission (NRC) staff finds that a response to the enclosed request for additional information is needed before we can complete the review. A draft of the enclosed questions was sent to the licensee on March 31,2011.

This request was discussed with Mr. Tom Mathews of your staff on April 27, 2011, and it was agreed that a response would be provided within 30 days from this date. During the call, the NRC staff identified an additional question regarding the manning of the temporary emergency diesels was not part of the March 31, 2011, draft. Question 2 has been modified to include a request for this additional information.

Mr. R. Krich -2 If you have any questions, please contact me at (301) 415-1055.

Sincerely, Christopher Gratton, Senior Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-259, 50-260, and 50-296

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST FOR EXTENSION OF THE COMPLETION TIME FOR INOPERABLE DIESEL GENERATORS TENNESSEE VALLEY AUTHORITY BROWNS FERRY UNITS 1, 2, AND 3 DOCKET NOS. 50-259, 50-260, 50-296 On January 19, 2011 (Agencywide Documents Access and Management System (ADAMS)

Accession No.11 0140319), the Nuclear Regulatory Commission (NRC) staff requested additional information from Tennessee Valley Authority (TVA) regarding its November 12, 2010 (ADAMS)

Accession No, ML103210334), amendment application. The following questions pertain to TVA's response dated February 8, 2011 (ADAMS Accession No, ML110450256).

1. Staff question to TVA Response to Electrical Question 3a The licensee stated that "Achieving a cold shutdown condition during an SBO [station blackout] is not part of the plant's accepted SBO licensing basis ...therefore the loads assigned to the TDGs

[temporary diesel generators] are those needed to achieve HOT SHUTDOWN conditions."

The NRC staff is not evaluating the licensee's compliance with Title 10 of the Code of Federal Regulations (10 CFR), Section 50.63. The SBO analysis demonstrated the plant's capability to maintain HOT SHUTDOWN conditions for an extended duration.

The staffs objective of requiring an extra power source for an inoperable emergency diesel generator (EDG) is to avoid a potential prolonged SBO event during the period of extended allowed outage time (AOT). The staff has limited granting AOT extensions to those licensees who have installed a supplemental alternating current (AC) power source (i.e., additional diesels, gas turbines, or other power sources) that can be substituted for an inoperable EDG in the event of an extended loss-of-offsite power (LOOP). It is the staffs position that the supplemental AC source should have enough capacity to carry all LOOP loads to bring the unit to a cold shutdown and perform the EDG's original licensing basis functions on a multi-unit site. The supplemental AC source should be able to be manually aligned to the safety busses within one to two hours to replace the inoperable diesel generator and prevent SBO conditions for an extended duration.

The SBO analysis may be used to provide assurance about the capability of the plant to maintain shutdown conditions during the time it takes to restore AC power from the supplemental source.

While the supplemental AC source is intended to be used during a prolonged SBO event, it is not intended to maintain compliance with SBO licensing basis.

The staff considers it essential for the supplemental AC source to have adequate capacity to bring the plant to cold shutdown for the following reasons:

1. The design requirements of the onsite and offsite power sources ensure that the plant is capable of achieving cold shutdown following postulated accidents and anticipated operational occurrences. The supplemental AC source is needed to replace an existing Enclosure

-2 source that has the capacity to support cold shutdown loads to maintain the defense-in-depth philosophy. An accident is not postulated.

2. Technical Specification (TS) 3.8.1.1 requires the plant to be in cold shutdown if the limiting condition for operation is not met within the allotted time. In addition, TS 3.8.1.J requires entry into Limited Condition for Operation (LCO) 3.0.3 if a combination of onsite and offsite sources are not available. The supplemental source is expected to have adequate capacity to enable the plant to satisfy the requirements of LCO 3.0.3, if needed.

3. Other regulatory requirements, such as a responding to a serious fire, may require plant shutdown and transition to cold shutdown. The supplemental AC source should have adequate capacity to bring the plant to a cold shutdown as required by 10 CFR Part 50, Appendix R.

To maintain the defense-in-depth philosophy for the proposed plant configuration, provide details about the capability of the supplemental power source to bring the plant to a cold shutdown.

2. Staff question to TVA Response to Electrical Question 3b The licensee stated that TOG load testing will use a resistive load bank, and connection to a safety-related motor. The connection of a safety-related motor or other operable safety-related component to the nonsafety-related TOG(s) could cause the connected component, and any electrically interconnected components, to become inoperable, with respect to the TSs, during the test.

The NRC staffs expectation is that, as a minimum, the TOGs have a demonstrated capability for supplying large reactive power required during starting of the largest motor and steady state power requirements for expected loads to be connected to TOGs. The testing may be conducted at the TOG vendor/supplier's facility and the use of resistive load for demonstrating the kilowatt rating of the machine is acceptable. Please describe the planned method of verifying the reactive power capability of the proposed TOG.

In addition, please describe the operator manning requirements for the TOGs. Confirm that the TOGs will be continuously manned during any period that they are required to operate while an EOG is in extended period of AOT to ensure reliable operation and equal load sharing between the two TOGs, or provide a justification why continuous manning during operation is not required.

3. Staff question to TVA Response to Electrical Question 3c The licensee stated that during TOG load test, it will be ensured that the resistive load will be equally shared between the two TOGs.

The NRC staff is concerned about the resistive and reactive load sharing of the TOGs. The loads between the two TOGs will tend to become unequal (load drifting from one TOG to another TOG) due to any minor differences between the deSign and operating characteristics of the two TOGs.

Provide details on the design features of the proposed TOGs that will ensure that the load sharing will be maintained in a balanced condition between the generators.

-3

4. Staff question to TVA Response to Supplementary Question 1 (See January 19, 2011, cover letter)

The licensee has considered the potential unavailability of the TOG during the extended allowed outage time of an EOG under maintenance. The proposed TS allows 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to restore an inoperable TOG from the point of discovery of an unavailable TOG if the unavailability was discovered after 4 days of continuous OG inoperability. In the event that the unavailability of the TOG was discovered on day 11 of the outage, there may be no incentive to restore the TOG.

The intent of extending the completion time for TS 3.8.1 is to accommodate preplanned maintenance activities for EOGs. The TOG is expected to be available at the beginning of the preplanned activity.

The NRC staffs position is that the TOGs must be available during the entire period of extended outage time, since availability of TOGs is a primary consideration for allowing extended outage time. Please revise the Required Action 8.5 Completion Time for an unavailable TOG(s) based on above considerations.

'.. ML11118A154 OFFICE LPL2-2/PM LPL2-2/LA EEEB/BC LPL2-2/BC NAME CGratton BClavton (RSola for) LLund DBroaddu$

DATE 04/29/11 05/03/11 04/29/11 05/06/11