CNL-16-051, Proposed Technical Specification Change to Revise the Note Modifying SR 3.8.1.17 of TS 3.8.1 AC Sources - Operating (TS-SQN-16-04)

Proposed Technical Specification Change to Revise the Note Modifying SR 3.8.1.17 of TS 3.8.1 AC Sources - Operating (TS-SQN-16-04)

ML17073A018
Person / Time
Site:	Sequoyah
Issue date:	03/13/2017
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CNL-16-051
Download: ML17073A018 (22)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 CNL-16-051 March 13, 2017 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, Units 1 and 2 Renewed Facility Operating License Nos. DPR-77 and DPR-79 NRC Docket Nos. 50-327 and 328

Subject:

Sequoyah Nuclear Plant, Units 1 and 2, Proposed Technical Specification Change to Revise the Note Modifying SR 3.8.1.17 of TS 3.8.1 AC Sources - Operating (TS-SQN-16-04)

In accordance with the provisions of 10 CFR 50.90, "Application for Amendment of License, Construction Permit, or Early Site Permit," Tennessee Valley Authority (TVA) is submitting a request for an amendment to Renewed Facility Operating License Nos. DPR-77 and DPR-79 for the Sequoyah Nuclear Plant (SQN), Units 1 and 2, respectively.

TVA is proposing changes to SQN, Units 1 and 2, Surveillance Requirement (SR) 3.8.1.17 of TS 3.8.1, AC Sources - Operating to delete the modifying note to allow the performance of the Surveillance Requirement in Modes 1 through 4 when the associated load is out of service for maintenance or testing.

The enclosure provides a description of the proposed changes, technical evaluation of the proposed changes, regulatory evaluation, and a discussion of environmental considerations.

Attachments 1 and 2 to the enclosure provide the existing TS and Bases pages marked-up to show the proposed changes. Attachments 3 and 4 to the enclosure provide the existing TS and Bases pages retyped with the proposed changes incorporated. The Bases pages are being provided for information only.

TVA has determined that there are no significant hazards considerations associated with the proposed change and that the TS change qualifies for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9).

U.S. Nuclear Regulatory Commission CNL-16-051 Page 2 March 13, 2017 The SQN Plant Operations Review Committee and the TVA Nuclear Safety Review Board have reviewed this proposed change and determined that operation of SQN in accordance with the proposed change will not endanger the health and safety of the public.

Additionally, in accordance with 10 CFR 50.91 (b)(1 ), TVA is sending a copy of this letter and the enclosure to the Tennessee Department of Environment and Conservation .

TVA requests approval of this proposed license amendment by March 31, 2018 with implementation within 60 days of approval.

There are no new regulatory commitments contained in this letter. If you have any questions , please contact Ed Schrull at 423-751-3850 .

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 13th day of March 2017 .

Respectfully, J. W . Shea Vice President, Nuclear Licensing

Enclosure:

Evaluation of Proposed Change cc (Enclosures):

NRC Regional Administrator- Region II NRC Senior Resident Inspector- Sequoyah Nuclear Plant NRC SQN Project Manager

ENCLOSURE TS-SQN-16-04 Evaluation of Proposed Change

Subject:

Delete the Note Modifying SR 3.8.1.17 of TS 3.8.1, AC Sources - Operating 1.0 34T 34T

SUMMARY

DESCRIPTION .............................................................................................. 2 34T 34T 2.0 34T 34T DETAILED DESCRIPTION ............................................................................................... 2 34T 34T 2.1 Proposed Changes ........................................................................................................... 2 34T 34T 34T 34T 2.2 Condition Intended to Resolve .......................................................................................... 2 34T 34T 34T 34T 3.0 34T 34T TECHNICAL EVALUATION .............................................................................................. 3 34T 34T 4.0 34T 34T REGULATORY EVALUATION .......................................................................................... 4 34T 34T 4.1 Applicable Regulatory Requirements/Criteria ................................................................... 4 34T 34T 34T 34T 4.2 Precedent .......................................................................................................................... 5 34T 34T 34T 34T 4.3 Significant Hazards Consideration .................................................................................... 6 34T 34T 34T 34T 5.0 34T 34T ENVIRONMENTAL CONSIDERATION ............................................................................ 7 34T 34T 6.0 34T 34T REFERENCES .................................................................................................................. 8 34T 34T ATTACHMENTS:

1. Proposed Technical Specifications Markups

2. Proposed TS Bases Page Markups (for information only)

3. Proposed Retyped Technical Specifications Pages

4. Proposed Retyped TS Bases Pages (for information only)

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1.0

SUMMARY

DESCRIPTION This proposed change revises the Sequoyah Nuclear Plant (SQN) Surveillance Requirement (SR) 3.8.1.17 (verify load sequence timer setpoint) of Technical Specification (TS) 3.8.1, AC Sources - Operating, to delete the modifying Note, thereby allowing the performance of the SR in Modes 1 through 4 when the associated equipment is out of service for maintenance or testing.

SQN does not have a single load sequence timer to apply loads to the EDG under accident and loss of offsite power conditions. SQN uses discrete timers that sequentially apply the individual loads to the EDG to respond to an accident or loss of offsite power condition.

TVA proposes to allow verifying that the automatic load sequencer timers are within

+/- 5% of their design setpoints to be performed in any operational mode. This change allows testing, currently required to be performed during outages, to be moved to periods with lighter, less complex maintenance schedules and therefore make more efficient use of existing limiting condition for operation (LCO) allowed outage time.

2.0 DETAILED DESCRIPTION 2.1 Proposed Changes The Note modifying SR 3.8.1.17 that prevents the performance of this SR in Mode 1, 2, 3, or 4 as planned maintenance is deleted.

Mark-ups of the affected TS pages are provided in Attachment 1. Mark-ups of the proposed TS Bases changes are provided in Attachment 2. Attachments 3 and 4 provide clean versions the TS and Bases pages with the proposed changes incorporated. Attachments 2 and 4 are provided for information only.

2.2 Condition Intended to Resolve Prior to the implementation of Improved Standard Technical Specifications (ISTS)

(NUREG-1431), SQN Custom TS SR 4.8.1.1.2.d.10 verified that the automatic load sequence timers are OPERABLE with the setpoint for each sequence timer within +/-5 %

of its design setpoint. SR 4.8.1.1.2.d contained a note which stated: made be performed in Modes 1, 2, 3, and 4 if the associated equipment was out of service for maintenance or testing. This note allowed SQN to perform this testing outside of a refueling outage. During the conversion to ISTS, TVA adopted the standard NUREG-1431 wording for corresponding ISTS SR (SR 3.8.1.17), including the modifying note that states: For DGs 1A-A and 1B-B, this Surveillance shall not normally be performed in MODE 1, 2, 3, or 4. However, this Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the plant is maintained or enhanced. Credit may be taken for unplanned events that satisfy this SR. This note prevents the routine performance of SR 3.8.1.17 in Modes 1, 2, 3, and 4. As a result, the routine performance of SR 3.8.1.17 can only be performed during refueling outages.

The proposed change allows SQN to perform SR 3.8.1.17 in Modes 1, 2, 3, and 4 if the associated equipment is out of service for maintenance or testing.

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3.0 TECHNICAL EVALUATION

The standby Emergency Diesel Generators (EDGs) serve as the plant emergency standby alternating current (AC) power sources. They are designed, installed, and tested to requirements necessary to ensure their availability.

The EDGs consist of four self-contained, water-cooled, automatic-starting, diesel engine driven, and stationary electric generators. Two EDGs in the same train are required to mitigate a design basis event (DBE) in one unit. Redundancy for single failure is provided by maintaining four EDGs in ready condition for automatic start. The EDGs are designed for automatic connection to 6.9-kV shutdown boards with automatic load sequencer timers adding large loads to the boards in the appropriate sequence so that the EDGs do not overload during the process.

The EDGs have various protective devices installed to shut down an EDG automatically to prevent heavy damage in the event of a system malfunction. As described in the SQN Updated Final Safety Analysis Report (UFSAR) Section 8.3.1.1, these protective devices are operative only during the exercise mode of operation, with the exception of the generator differential relay and the engine overspeed switch.

Calibration of the time delay relays, associated with automatic load sequence timers, may defeat certain functions in the downstream equipment energized by the timer, which may require entry into LCO Actions for the associated function. However, the time required to perform the calibration is typically a small fraction of the LCO Completion Time. Maintenance and testing of the associated functions typically require periodic entry into these same LCO Actions. Coupling the calibrations with existing maintenance or testing does not increase the unavailability of the equipment. The proposed change allows testing, currently required to be performed during outages, to be moved to periods with lighter, less complex maintenance schedules and therefore make more efficient use of existing LCO allowed outage time and inherently reducing the potential for human error.

SQN does not have a single load sequence timer to apply loads to the EDG under accident and loss of offsite power conditions. SQN uses discrete timers that sequentially apply the individual loads to the EDG to respond to an accident or loss of offsite power condition. Because of this configuration, the method of testing does not affect offsite circuits, perturb the electrical distribution system, nor challenge safety systems.

This change is consistent with NRC Generic Letter 91-04, which states, "The Staff concludes that the TS need not restrict surveillances as only being performed during shutdown. Nevertheless, safety dictates that when refueling interval surveillances are being performed during power operation licensees give proper regard for their effect on safe operation of the plant." The Standard TSs recognize this issue in the reviewers note concerning mode restrictions, which allows plant specific removal of mode restrictions based on meeting the follow three criteria.

The performance of the SR does not render any safety system or component inoperable.

This criterion is met by doing the work coupled with existing out-of-service conditions.

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The performance of the SR does not cause perturbations to any of the electrical distribution systems that could result in a challenge to steady state operation or to plant safety systems.

SQN utilizes individual discrete time delay relays, in lieu of a single load sequencer, to sequentially load the EDGs following a loss of offsite power. Calibration of the time delay relays, associated with the load sequencing, only affects downstream equipment, which will already be out of-service for testing or maintenance activities.

Therefore, there would be no challenge to steady state operation or to plant safety systems.

The performance of the SR does not cause or result in an anticipated operational occurrence with attendant challenge to plant safety systems.

The work will be coupled with existing out-of-service conditions so it would not cause or result in an anticipated operational occurrence.

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria The NRC's regulatory requirements related to the content of the TSs are contained in 10 CFR 50.36. The TS requirements in 10 CFR 50.36 include the following categories:

(1) safety limits, limiting safety systems settings, and limiting control settings; (2) LCOs; (3) surveillance requirements; (4) design features; and (5) administrative controls.

d in 10 CFR 50.59(c)(1)(i), a licensee is required to submit a license amendment pursuant to 10 CFR 50.90 if a change to the TSs is required. Furthermore, the requirements of 10 CFR 50.59 necessitate that the NRC approve the TS changes before they are implemented. TVA's submittal meets the requirements of 10 CFR 50.59(c)(1)(i) and 10 CFR 50.90.

General Design Criteria (GDC)

SQN was designed to meet the intent of the Proposed General Design Criteria for Nuclear Power Plant Construction Permits published in July 1967. The SQN construction permit was issued in May 1970. However, the UFSAR addresses the NRC GDCs published as Appendix A to 10 CFR 50 in July 1971. Conformance with the GDCs is described in Section 3.1.2 of the UFSAR.

The onsite standby AC power systems at SQN Units 1 and 2 are designed to comply with the following applicable regulations and requirements.

GDC 17, "Electric power systems," specifies that an onsite electric power system shall be provided to permit functioning of structures, systems, and components important to safety.

10 CFR 50, Appendix A, GDC 18, "Inspection and testing of electric power systems,"

specifies that electric power systems important to safety shall be designed to permit appropriate periodic inspection and testing of important areas and features.

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Regulatory Guide 1.6, Revision 0 (Reference 2), "Independence Between Redundant Standby (Onsite) Power Sources and Between Their Distribution Systems," describes an acceptable degree of independence between redundant standby (onsite) power sources and between their distribution systems.

Regulatory Guide 1.9, Revision 0 (Reference 3), "Selection of Diesel Generator Set Capacity for Standby Power Supplies." As noted in UFSAR Section 8.3.1.2.1, SQN Units 1 and 2 comply with Regulatory Guide 1.9, Revision 0 except that voltage and frequency recovery requirements are taken from Regulatory Guide 1.9, Revision 1 (Reference 4). As further noted in SQN UFSAR Section 8.3.1.2.1, an exception is taken for frequency immediately following DG breaker closure. The DG breaker is designed to automatically close at about 94 % of nominal frequency. This exception was accepted by the NRC in NUREG-1232 Volume 2 (Reference 5).

IEEE Standard 308-1971, "Criteria for Class 1E Power Systems for Nuclear Power Generating Stations," provides criteria for the determination of Class 1E power system design features and the requirements for their testing, surveillance, and documentation.

With the implementation of the proposed change, SQN Units 1 and 2 continue to meet the applicable regulations and requirements, subject to the previously approved exceptions.

4.2 Precedent In Reference 1, the NRC previously approved change to SR 4.8.1.1.2.d.10 for SQN, Units 1 and 2, added a note that allowed SQN to verify that the automatic load sequence timers were OPERABLE with the setpoint for each sequence timer within +/-5 % of its design setpoint in Modes 1, 2, 3, and 4. This note was removed from the SQN TS with the ITS implementation.

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4.3 Significant Hazards Consideration The proposed change to Sequoyah Nuclear Plant (SQN) Surveillance Requirement (SR) 3.8.1.17 of TS 3.8.1, AC Sources - Operating allows verifying that the automatic load sequencer timers are within +/- 5% of their design setpoints to be performed in any operational mode if coupled with existing testing or maintenance. This change allows testing, currently required to be performed during outages, to be moved to periods with lighter, less complex maintenance schedules and therefore make more efficient use of existing limiting condition for operation (LCO) allowed outage time.

Tennessee Valley Authority (TVA) has concluded that the proposed change to does not involve a significant hazards consideration. TVAs conclusion is based on its evaluation in accordance with Title 10 of the Code of Federal Regulations (10 CFR) 50.91(a)(1) of the three standards set forth in 10 CFR 50.92, Issuance of Amendment, as discussed below:

1. Does the proposed amendment involve a significant increase in the probability or consequence of an accident previously evaluated?

Response: No.

The proposal does not alter the function of any structure, system or component functions, does not modify the manner in which the plant is operated, and does not alter equipment out-of-service time. This request does not degrade the ability of the emergency diesel generator or equipment downstream of the load sequencers to perform their intended function. Therefore, the proposed change does not involve a significant increase in the probability or consequence of an accident previously evaluated.

2. Does the proposed amendment create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No.

The proposed change does not involve any physical changes to plant safety related structure, system or component or alter the modes of plant operation in a manner that is outside the bounds of the current emergency diesel generator system design analyses. The proposed change to revise the note modifying SR 3.8.1.17 to allow the performance of the SR in Modes 1 through 4 when the associated equipment is out of service for maintenance or testing does not create the possibility for an accident or malfunction of a different type than any evaluated previously in SQN's Updated Final Safety Analysis Report. The proposal does not alter the way any structure, system or component function and does not modify the manner in which the plant is operated. Therefore, the proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

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3. Does the proposed amendment involve a significant reduction in a margin of safety?

Response: No.

The proposed change to TS 3.8.1, AC Sources - Operating to revise the note modifying SR 3.8.1.17 to allow the performance of the SR in Modes 1 through 4 when the associated equipment is out of service for maintenance or testing does not reduce the margin of safety because the test methodologies are not being changed and LCO allowed outage times are not being changed. The results of accident analyses remain unchanged by this request. Therefore, the proposed change does not involve a significant reduction in a margin of safety.

Based on the above, TVA concludes that the proposed amendment does not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92 (c), and accordingly, a finding of no significant hazards consideration is justified.

In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

5.0 ENVIRONMENTAL CONSIDERATION

A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20. However, the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

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6.0 REFERENCES

1. Letter from NRC to TVA, Issuance of Technical Specification Amendments for the Sequoyah Nuclear Plant, Units 1 and 2, dated February 9, 1999. (ADAMS Accession Nos. 9902160015, 9902160022, and 9902160026)

2. Regulatory Guide 1.6, Revision 0, "Independence Between Redundant Standby (Onsite)

Power Sources and Between Their Distribution Systems (Safety Guide 6)"

3. Regulatory Guide 1.9, Revision 0, "Selection of Diesel Generator Set Capacity for Standby Power Supplies"

4. Regulatory Guide 1.9, Revision 1, "Selection of Diesel Generator Set Capacity for Standby Power Supplies"

5. NUREG-1232, Volume 2, Safety Evaluation Report On Tennessee Valley Authority:

Sequoyah Nuclear Performance Plan, dated May 1988 E-8

Attachment 1 Proposed Technical Specifications Markups

AC Sources - Operating 3.8.1 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.17 ------------------------------NOTE------------------------------- In accordance For DGs 1A-A and 1B-B, this Surveillance shall not with the normally be performed in MODE 1, 2, 3, or 4. Surveillance However, this Surveillance may be performed to Frequency reestablish OPERABILITY provided an assessment Control Program determines the safety of the plant is maintained or enhanced. Credit may be taken for unplanned events that satisfy this SR.

Verify setpoint for each load sequence timer is within +/- 5% of design.

SEQUOYAH - UNIT 1 3.8.1-14 Amendment 334

AC Sources - Operating 3.8.1 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.17 ------------------------------NOTE-------------------------------

For DGs 2A-A and 2B-B, this Surveillance shall not normally be performed in MODE 1, 2, 3, or 4. However, this Surveillance may be performed to reestablish OPERABILITY provided an assessment determines the safety of the plant is maintained or enhanced. Credit may be taken for unplanned events that satisfy this SR.

Verify setpoint for each load sequence timer is In accordance within +/- 5% of design. with the Surveillance Frequency Control Program SEQUOYAH - UNIT 2 3.8.1-14 Amendment 327

Attachment 2 Proposed TS Bases Page Markups (for information only)

AC Sources - Operating B 3.8.1 BASES SURVEILLANCE REQUIREMENTS (continued)

SR 3.8.1.17 Under accident and loss of offsite power conditions loads are sequentially connected to the board by the load sequence timers. The sequencing logic controls the permissive and starting signals to motor breakers to prevent overloading of the DGs due to high motor starting currents. The 5% load sequence time interval tolerance ensures that sufficient time exists for the DG to restore frequency and voltage prior to applying the next load and that safety analysis assumptions regarding ESF equipment time delays are not violated. Reference 2 provides a summary of the automatic loading of Shutdown Boards.

The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

This SR is modified by a Note. The reason for the Note is that performing the Surveillance would remove a required offsite circuit from service, perturb the electrical distribution system, and challenge safety systems.

This restriction from normally performing the Surveillance for DGs 1A-A and 1B-B in MODE 1 or 2 is further amplified to allow the Surveillance to be performed for the purpose of reestablishing OPERABILITY (e.g., post work testing following corrective maintenance, corrective modification, deficient or incomplete surveillance testing, and other unanticipated OPERABILITY concerns) provided an assessment determines plant safety is maintained or enhanced. This assessment shall, as a minimum, consider the potential outcomes and transients associated with a failed Surveillance, a successful Surveillance, and a perturbation of the offsite or onsite system when they are tied together or operated independently for the Surveillance; as well as the operator procedures available to cope with these outcomes. These shall be measured against the avoided risk of a plant shutdown and startup to determine that plant safety is maintained or enhanced when the Surveillance is performed in MODE 1 or 2. Risk insights or deterministic methods may be used for this assessment. Credit may be taken for unplanned events that satisfy this SR.

SEQUOYAH - UNIT 1 B 3.8.1-29 Revision 4546

AC Sources - Operating B 3.8.1 BASES SURVEILLANCE REQUIREMENTS (continued)

SR 3.8.1.17 Under accident and loss of offsite power conditions loads are sequentially connected to the board by the load sequence timers. The sequencing logic controls the permissive and starting signals to motor breakers to prevent overloading of the DGs due to high motor starting currents. The 5% load sequence time interval tolerance ensures that sufficient time exists for the DG to restore frequency and voltage prior to applying the next load and that safety analysis assumptions regarding ESF equipment time delays are not violated. Reference 2 provides a summary of the automatic loading of Shutdown Boards.

The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

This SR is modified by a Note. The reason for the Note is that performing the Surveillance would remove a required offsite circuit from service, perturb the electrical distribution system, and challenge safety systems.

This restriction from normally performing the Surveillance for DGs 2A-A and 2B-B in MODE 1 or 2 is further amplified to allow the Surveillance to be performed for the purpose of reestablishing OPERABILITY (e.g., post work testing following corrective maintenance, corrective modification, deficient or incomplete surveillance testing, and other unanticipated OPERABILITY concerns) provided an assessment determines plant safety is maintained or enhanced. This assessment shall, as a minimum, consider the potential outcomes and transients associated with a failed Surveillance, a successful Surveillance, and a perturbation of the offsite or onsite system when they are tied together or operated independently for the Surveillance; as well as the operator procedures available to cope with these outcomes. These shall be measured against the avoided risk of a plant shutdown and startup to determine that plant safety is maintained or enhanced when the Surveillance is performed in MODE 1 or 2. Risk insights or deterministic methods may be used for this assessment. Credit may be taken for unplanned events that satisfy this SR.

SEQUOYAH - UNIT 2 B 3.8.1-29 Revision 4546

Attachment 3 Proposed Retyped Technical Specifications Pages

AC Sources - Operating 3.8.1 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.17 Verify setpoint for each load sequence timer is In accordance within +/- 5% of design. with the Surveillance Frequency Control Program SEQUOYAH - UNIT 1 3.8.1-14 Amendment XXX

AC Sources - Operating 3.8.1 SURVEILLANCE REQUIREMENTS (continued)

SURVEILLANCE FREQUENCY SR 3.8.1.17 Verify setpoint for each load sequence timer is In accordance within +/- 5% of design. with the Surveillance Frequency Control Program SEQUOYAH - UNIT 2 3.8.1-14 Amendment 327

Attachment 4 Proposed Retyped TS Bases Pages (for information only)

AC Sources - Operating B 3.8.1 BASES SURVEILLANCE REQUIREMENTS (continued)

SR 3.8.1.17 Under accident and loss of offsite power conditions loads are sequentially connected to the board by the load sequence timers. The sequencing logic controls the permissive and starting signals to motor breakers to prevent overloading of the DGs due to high motor starting currents. The 5% load sequence time interval tolerance ensures that sufficient time exists for the DG to restore frequency and voltage prior to applying the next load and that safety analysis assumptions regarding ESF equipment time delays are not violated. Reference 2 provides a summary of the automatic loading of Shutdown Boards.

The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

SEQUOYAH - UNIT 1 B 3.8.1-29 Revision 46

AC Sources - Operating B 3.8.1 BASES SURVEILLANCE REQUIREMENTS (continued)

SR 3.8.1.17 Under accident and loss of offsite power conditions loads are sequentially connected to the board by the load sequence timers. The sequencing logic controls the permissive and starting signals to motor breakers to prevent overloading of the DGs due to high motor starting currents. The 5% load sequence time interval tolerance ensures that sufficient time exists for the DG to restore frequency and voltage prior to applying the next load and that safety analysis assumptions regarding ESF equipment time delays are not violated. Reference 2 provides a summary of the automatic loading of Shutdown Boards.

The Surveillance Frequency is controlled under the Surveillance Frequency Control Program.

SEQUOYAH - UNIT 2 B 3.8.1-29 Revision 46