Text

License Amendment Request for Technical Specification 3.3.4, Control Rod Drive Trip Devices, Technical Specification Change (TSC) Number 2003-09, Supplement 1
	ML040850418
Person / Time
Site:	Oconee
Issue date:	03/15/2004
From:	Rosalyn Jones; Duke Energy Corp
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	Download: ML040850418 (42)
	v • d • e

Duke R. A. JONES

rPowere Vice President A Duke Energy Company Duke Power 29672 / Oconee Nuclear Site 7800 Rochester Highway Seneca, SC 29672 864 885 3158 864 885 3564 fax March 15, 2004 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Attention: Document Control Desk

Subject:

Oconee Nuclear Station Docket Numbers 50-269, 270, and 287 License Amendment Request for Technical Specification 3.3.4, Control Rod Drive Trip Devices Technical Specification Change (TSC) Number 2003-09, Supplement 1 In a submittal dated January.15, 2004, Duke Energy Corporation (Duke) proposed to amend Appendix A, Technical Specifications, for Facility Operating Licenses DPR-38, DPR-47 and DPR-55 for Oconee Nuclear Station (ONS), Units 1, 2, and 3. The proposed License Amendment Request (LAR) revises the Technical Specifications (TS) for the Control Rod Drive (CRD) Trip Devices. This supplement clarifies the scope of the change Duke is requesting the Nuclear Regulatory Commission (NRC) to approve.

Duke's January 15, 2004, submittal indicates that the replacement of the CRD/Reactor Trip Breakers (RTBs) is part of the overall digital Control Rod Drive Control System (CRDCS) upgrade. The replacement of the RTBs, although included in the overall modification, is not a digital upgrade. The digital upgrade involves the CRD control system only. The portion of the modification requiring a Technical Specification change to allow implementation is the RTB replacement.

Duke is replacing the existing two AC RTBs and four DC RTBs with four AC RTBs. Duke proposes to revise TS 3.3.4, "Control Rod Drive (CRD) Trip Devices," to address the new configuration. Since ONS Technical Specifications are common to all three units, Notes will be used to indicate the applicable requirement for each unit based on whether the RTB upgrade is complete. The proposed change to TS (D I www. duke-energy.com

U. S. Nuclear Regulatory Commission March 15, 2004 Page 2 3.3.4 adds a Limiting Condition for Operation (LCO) and appropriate ACTIONS for the new configuration. After completion of the modification on all three units, Duke will submit a TS change to remove the obsolete requirements related to the existing CRD Trip Devices.

The revised TS pages are included in Attachment 1. contains the markup of the current TS pages.

The Technical Justification for the amendment request is included in Attachment 3. Attachment 4 provides a revised No Significant Hazards Consideration that addresses only the RTB portion of the overall modification. The final conclusion that there are no signification hazards involved in the LAR remains unchanged. These attachments replace the previously provided attachments in their entirety. The supplement does not impact the Environmental Assessment provided in the January 15, 2004, submittal.

The proposed changes are administrative in nature and have been determined to be within the scope of the original Plant Operations Review Committee and Nuclear Safety Review Board reviews.

Duke plans to implement this modification first on Unit 3 during the fall 2004 refueling outage. Approval of this proposed LAR is requested by September 30, 2004, to support this implementation schedule. A 90-day implementation period is requested for the Technical Specification change.

Implementation of these changes will not result in an undue risk to the health and safety of the public.

UFSAR changes necessary to reflect approval of this submittal will be made in accordance with 10 CFR 50.71(e).

Pursuant to 10 CFR 50.91, a copy of this proposed amendment is being sent to the South Carolina Department of Health and Environmental Control for review, and as deemed necessary and appropriate, subsequent consultation with the NRC staff.

U. S. Nuclear Regulatory Commission March 15, 2004 Page 3 If there are any additional questions, please contact Boyd Shingleton at (864) 885-4716.

Ver t ly yours, Jones, Vice President Oconee Nuclear Site

U. S. Nuclear Regulatory Commission March 15, 2004 Page 4 cc: Mr. L. N. Olshan, Project Manager Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop 0-14 H25 Washington, D. C. 20555 Mr. L. A. Reyes, Regional Administrator U. S. Nuclear Regulatory Commission - Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30303 Mr. M. C. Shannon Senior Resident Inspector Oconee Nuclear Station Mr. Henry Porter, Director Division of Radioactive Waste Management Bureau of Land and Waste Management Department of Health & Environmental Control 2600 Bull Street Columbia, SC 29201

U. S. Nuclear Regulatory Commission March 15, 2004 Page 5 R. A. Jones, being duly sworn, states that he is Vice President, Oconee Nuclear Site, Duke Energy Corporation, that he is authorized on the part of said Company to sign and file with the U. S. Nuclear Regulatory Commission this revision to the Renewed Facility Operating License Nos. DPR-38, DPR-47, DPR-55; and that all the statements and matters set forth herein are true and correct to the best of his knowledge R. A. to Vice President Oconee Nuclear Site S scrib ed and sworn to before me this / A day of L*L X1 2004 Notary Public My.Commission Expires:

ATTACHMENT 1 TECHNICAL SPECIFICATION Remove Page Insert Page 3.3.4-1 3.3.4-1 3.3.4-2 3.3.4-2 3.3.4-3 3.3.4-3 TECHNICAL SPECIFICATION BASES B 3.3.4 B 3.3.4-6 B 3.3.4 B 3.3.4-7

CRD Trip Devices 3.3.4 3.3 INSTRUMENTATION 3.3.4 Control Rod Drive (CRD) Trip Devices LCO 3.3.4 a. Four AC CRD trip breakers shall be OPERABLE for Unit(s) with the CRD/Reactor Trip Breaker (RTB) Upgrade complete.

b. The following CRD trip devices shall be OPERABLE for Unit(s) with the CRD/RTB Upgrade not complete:

1. Two AC CRD trip breakers;

2. Two DC CRD trip breaker pairs; and

3. Eight electronic trip assembly (ETA) relays APPLICABILITY: MODES 1 and 2, MODES 3, 4, and 5 when any CRD trip breaker is in the closed position and the CRD System is capable of rod withdrawal.

ACTIONS

.------------------------ NOTE---------------------------------------------------------

Separate Condition entry is allowed for each CRD trip device.

CONDITION REQUIRED ACTION COMPLETION TIME A. One or more CRD A.1 Trip the CRD trip 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months trip breakers diverse breaker.

trip Functions inoperable OR OR A.2 Remove power from 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months the CRD trip breaker.

One or more required DC CRD breaker pair diverse trip Functions inoperable.

(continued)

OCONEE UNITS 1, 2, & 3 3.3.4-1 Amendment Nos. I

CRD Trip Devices 3.3.4 CONDITION REQUIRED ACTION COMPLETION TIME B. One or more CRD B.1 Trip the CRD trip 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months I trip breakers breaker.

inoperable for reasons other than OR Condition A.

B.2 Remove power from 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months OR the CRD trip breaker.

One or more required DC CRD breaker pairs inoperable for reasons other than Condition A.

C. One or more C.1 Transfer affected 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months required ETA relays CONTROL ROD group I inoperable. to power supply with OPERABLE ETA relays.

OR C.2 Trip corresponding AC 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months CRD trip breaker(s).

(continued)

OCONEE UNITS 1,2, &3 3.3.4-2 Amendment Nos. I

CRD Trip Devices 3.3.4 CONDITION REQUIRED ACTION COMPLETION TIME D. Required Action and D.1 Be in MODE 3. 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months associated Completion Time not met in AND MODE 1, 2, or 3.

D.2.1 Open all CRD trip 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months breakers.

OR D.2.2 Remove power from all 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months CRD trip breakers.

E. Required Action and E.1 Open all CRD trip 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months associated Completion breakers.

Time not met in MODE 4 or 5. OR E.2 Remove power from all 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months CRD trip breakers.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.3.4.1 Perform CHANNEL FUNCTIONAL TEST. 31 days OCONEE UNITS 1,2,&3 3.3.4-3 Amendment Nos. I

CRD Trip Devices B 3.3.4 B 3.3 INSTRUMENTATION B 3.3.4 Control Rod Drive (CRD) Trip Devices BASES BACKGROUND The Reactor Protective System (RPS) contains multiple CRD trip devices:

four AC trip breakers for Unit(s) with CRD/Reactor Trip Breaker (RTB) upgrade complete or two AC trip breakers, two DC trip breaker pairs and eight electronic trip assembly (ETA) relays for Unit(s) with the CRD/RTB upgrade not complete. For Unit(s) with the CRD/RTB upgrade not complete, the system has two separate paths (or channels), with each path having one AC breaker in series with a pair of DC breakers and functionally in series with four ETA relays in parallel. For Unit(s) with the CRD/RTB upgrade complete, the system has two separate paths (or channels), with each path having two AC breakers in series. In either case, each path provides independent power to the CRDs. Also, in either case, either path can provide sufficient power to operate the entire CRD System.

For Unit(s) with the CRD/RTB upgrade complete, Figure 7.1, UFSAR, Chapter 7 (Ref. 1), illustrates the configuration of Reactor Protection System (RPS) Reactor Trip Modules (RTM's) and the trip breakers. For Unit(s) with the CRD/RTB upgrade not complete, Figure 7.1 a, UFSAR, Chapter 7 (Ref. 1), illustrates the configuration of the CRD trip devices. To trip the reactor, power to the CRDs must be removed. Loss of power causes the CRD mechanisms to release the CONTROL RODS, which then fall by gravity into the core.

Power to CRDs is supplied from two separate sources through the AC trip circuit breakers. For Unit(s) with the CRD/RTB upgrade complete, these breakers are designated A, B, C, and D and their undervoltage (trip) coils are powered by RPS channels A, B, C, and D, respectively. For Unit(s) with the CRD/RTB upgrade not complete, these breakers are designated A and B, and their undervoltage trip coils are powered by RPS channels A and B, respectively. From the circuit breakers, the CRD power travels through voltage regulators and stepdown transformers. For Unit(s) I OCONEE UNITS 1, 2, & 3 B 3.3.4-1 Amendment Nos. I

CRD Trip Devices B 3.3.4 BASES BACKGROUND with the CRD/RTB upgrade complete, these devices in turn supply (continued) redundant buses that feed the Single Rod Power Supply (SRPS). For Unit(s) with the CRD/RTB upgrade not complete, these devices in turn supply redundant buses that feed the DC power supplies and the regulating rod, APSR and auxiliary power supplies.

For Unit(s) with the CRD/RTB upgrade not complete, the DC power supplies rectify the AC input and supply power to hold the safety rods in their fully withdrawn position. One of the redundant power sources supplies phase A; the other, phase CC. Either phase being energized is sufficient to hold the rod. Two breakers are located on the output of each power supply. Each breaker controls half of the power to two of the four safety rod groups. The undervoltage trip coils on the two circuit breakers on the output of one of the power supplies is controlled by RPS channel C.

The other two breakers are controlled by RPS channel D.

For Unit(s) with the CRD/RTB upgrade not complete, in addition to the DC power supplies, the redundant buses also supply power to the regulating rod, APSR and auxiliary power supplies. These power supplies contain silicon controlled rectifiers (SCRs) that are gated on and off to provide power to, and remove power from, the phases of the CRD mechanisms.

The gating control signal for these SCRs is supplied through the closed contacts of the ETA relays. These contacts are referred to as E and F contactors, and are controlled by the C and D RPS channels respectively.

The following applies to Unit(s) with the CRD/RTB upgrade not complete:

The AC breaker and DC breakers are in series in one of the power supplies; whereas, the redundant AC breaker and DC breakers are in series in the other power supply to the CONTROL RODS. The logic required to cause a reactor trip is the opening of a circuit breaker in each of the redundant power supplies. (The pair of DC circuit breakers on the output of the power supply are treated as one breaker.) This is known as a one-out-of-two taken twice logic. The following examples illustrate the operation of the reactor trip circuit breakers.

a. If the A AC circuit breaker opens:

1. the input power to associated DC power supply is lost, and

2. the SCR supply from the associated power source is lost.

OCONEE UNITS 1, 2, & 3 B 3.3.4-2 Amendment Nos. I

CRD Trip Devices B 3.3.4 BASES BACKGROUND b. If the D DC circuit breaker(s) and F contactors open:

(continued)

1. the output of the DC power supply is lost, and

2. when the F contactor opens, SCR gating power is lost.

c. The combination of (a) and (b) causes a reactor trip.

The following applies to Unit(s) with the CRD/RTB upgrade complete:

Two AC breakers (A and C) are in series to feed one redundant train of the SRPS, whereas the other two series AC breakers (B and D) feed the other redundant train of the SRPS. The minimum required logic required to cause a reactor trip is the opening of a circuit breaker in each parallel path to the SRPS. This is known as a one-out-of-two taken twice logic. The following examples illustrate the operation of the reactor trip circuit breakers.

a. If the A or C circuit breaker opens input power to one train of the SRPS's is lost.

b. If in addition, the B or D circuit breaker opens input power to the other train of the SRPS's is lost, which will result in the dropping of all rods (except APSR's) into the core.

The logic developed within the RPS Reactor Trip Modules will result in all AC breakers tripping if any two RPS channels receive a trip signal.

In summary, two tripped RPS channels will cause a reactor trip. For example, a reactor trip occurs if RPS channel B senses a low Reactor Coolant System (RCS) pressure condition and if RPS channel C senses a variable low RCS pressure condition. When the channel B bistable relay de-energizes, the channel trip relay de-energizes and opens its associated contacts. The same thing occurs in channel C, except the variable lower pressure bistable relay de-energizes the channel C trip relay. When the output logic relays in channel B and C de-energize, the B and C OCONEE UNITS 1, 2, & 3. B 3.3.4-3 Amendment Nos. I

CRD Trip Devices B 3.3.4 BASES BACKGROUND contacts in the trip logic of each channel's reactor trip module (RTM) open (continued) causing an undervoltage to each trip breaker. All trip breakers and required ETA relay contactors open, and power is removed from all CRD I mechanisms. All rods fall into the core, resulting in a reactor trip.

APPLICABLE Accident analyses rely on a reactor trip for protection of reactor core SAFETY ANALYSES integrity, reactor coolant pressure boundary integrity, and reactor building OPERABILITY. A reactor trip must occur when needed to prevent accident consequences from exceeding those calculated in the accident analyses. The CONTROL ROD position limits ensure that adequate rod worth is available upon reactor trip to shut down the reactor to the required SDM. Further, OPERABILITY of the CRD trip devices ensures that all CONTROL RODS will trip when required. More detailed descriptions of the applicable accident analyses are found in the Bases for each of the individual RPS trip Functions in LCO 3.3.1, "Reactor Protective System (RPS) Instrumentation."

The CRD trip devices satisfy Criterion 3 of CFR 50.36 (Ref. 2).

LCO The LCO requires all of the specified CRD trip devices to be OPERABLE.

Failure of any required CRD trip device renders a portion of the RPS inoperable and reduces the reliability of the affected Functions. Without reliable CRD reactor trip circuit breakers and associated support circuitry, a reactor trip may not reliably occur when initiated either automatically or manually.

All required CRD trip devices shall be OPERABLE to ensure that the reactor remains capable of being tripped any time it is critical.

OPERABILITY is defined as the CRD trip device being able to receive a reactor trip signal and to respond to this trip signal by interrupting power to the CRDs. Both of the CRD trip breaker's diverse trip devices and the breaker itself must be functioning properly for the breaker to be OPERABLE.

For Unit(s) with the CRD/RTB upgrade not complete, both ETA relays I associated with each of the three regulating rod groups and the two ETA relays associated with the auxiliary power supply must be OPERABLE to satisfy the LCO. The ETA relays associated with the APSR power supply OCONEE UNITS 1, 2, & 3 B 3.3.4-4 Amendment Nos. I

CRD Trip Devices B 3.3.4 BASES LCO are not required to be OPERABLE because the APSRs are not designed (continued) to fall into the core upon initiation of a reactor trip.

Requiring all breakers and ETA relays (for Unit(s) with the CRD/RTB upgrade not complete) to be OPERABLE ensures that at least one device in each of the two power paths to the CRDs will remain OPERABLE even with a single failure.

APPLICABILITY The CRD trip devices shall be OPERABLE in MODES 1 and 2, and in MODES 3, 4, and 5 when any CRD trip breaker is in the closed position and the CRD System is capable of rod withdrawal.

The CRD trip devices are designed to ensure that a reactor trip would occur if needed. Since this condition can exist in all of these MODES, the CRD trip devices shall be OPERABLE.

ACTIONS A Note has been added to the ACTIONS indicating separate Condition entry is allowed for each CRD trip device.

A.1 and A.2 Condition A represents reduced redundancy in the CRD trip Function. For Unit(s) with the CRD/RTB upgrade complete, Condition A applies when:

one diverse trip Function (undervoltage or shunt trip device) is inoperable in one or more CRD trip breaker(s).

For Unit(s) with the CRD/RTB upgrade not complete, Condition A applies when:

One diverse trip Function (undervoltage or shunt trip device) is inoperable in one or more CRD trip breaker(s) or breaker pair; or

One diverse trip Function is inoperable in both DC trip breakers associated with one protective channel. In this case, the inoperable trip Function does not need to be the same for both breakers.

If one of the diverse trip Functions on a CRD trip breaker (or breaker pair for Unit(s) with the CRD/RTB upgrade not complete) becomes inoperable, actions must be taken to preclude the inoperable CRD trip device from preventing a reactor trip when needed. This is done by manually tripping OCONEE UNITS 1,2, &3 B 3.3.4-5 Amendment Nos. I

CRD Trip Devices B 3.3.4 BASES ACTIONS A.1 and A.2 (continued) the inoperable CRD trip breaker or by removing power from the inoperable CRD trip breaker. Either of these actions places the affected CRDs in a one-out-of-two trip configuration, which precludes a single failure from preventing a reactor trip. The 48 hour5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months Completion Time has been shown to be acceptable through operating experience.

B.1 and B.2 Condition B represents a loss of redundancy for the CRD trip Function.

Condition B applies when both diverse trip Functions are inoperable in one or more trip breaker(s ) (or breaker pair for Unit(s) with the CRD/RTB upgrade not complete).

Required Action B.1 and Required Action B.2 are the same as Required Action A.1 and Required Action A.2, but the Completion Time is shortened.

The 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Completion Time allowed to trip or remove power from the CRD trip breaker allows the operator to take all the appropriate actions for the inoperable breaker and still ensures that the risk involved is acceptable.

C.1 and C.2 Condition C does not apply to Unit(s) with the CRD/RTB upgrade complete.

Condition C represents a loss of redundancy for the CRD trip Function.

Condition C applies when one or more ETA relays are inoperable. The preferred action is to restore the ETA relay to OPERABLE status. If this cannot be done, the operator can perform one of two actions to eliminate reliance on the failed ETA relay. This first option is to switch the affected CONTROL ROD group to an alternate power supply. This removes the failed ETA relay from the trip sequence, and the unit can operate indefinitely. The second option is to trip the corresponding AC CRD trip breaker. This results in the safety function being performed, thereby eliminating the failed ETA relay from the trip sequence. The 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Completion Time is sufficient to perform the Required Action.

D.1, D.2.1. and D.2.2 With the Required Action and associated Completion Time of Condition A, B, or C not met in MODE 1, 2, or 3, the unit must be brought to a MODE in which the LCO does not apply. To achieve this status, the unit must be brought to MODE 3, with all CRD trip breakers open or with power from all CRD trip breakers removed within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months . The allowed Completion Time OCONEE UNITS 1, 2, & 3 B 3.3.4-6 Amendment Nos. I

CRD Trip Devices B 3.3.4 BASES (continued)

ACTIONS D.1. D.2.1, and D.2.2 (continued) of 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months is reasonable, based on operating experience, to reach'MODE 3 from full power conditions in an orderly manner and without challenging unit systems.

E.1 and E.2 With the Required Action and associated Completion Time of Condition A, B, or C not met in MODE 4 or 5, the unit must be brought to a MODE in which the LCO does not apply. To achieve this status, all CRD trip breakers must be opened or power from all CRD trip breakers removed within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . The allowed Completion Time of 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months is reasonable, based on operating experience, to open all CRD trip breakers or remove power from all CRD trip breakers without challenging unit systems.

SURVEILLANCE SR 3.3.4.1 REQUIREMENTS SR 3.3.4.1 is to perform a CHANNEL FUNCTIONAL TEST every 31 days.

This test verifies the OPERABILITY of the trip devices by actuation of the end devices. Also, this test independently verifies the undervoltage and shunt trip mechanisms of the trip breakers. The Frequency of 31 days is based on operating experience, which has demonstrated that failure of more than one channel of a given function in any 31 day interval is a rare event.

REFERENCES 1. UFSAR, Chapter 7.

2. 10 CFR 50.36.

OCONEE UNITS 1, 2, & 3 B 3.3.4-7 Amendment Nos. I

ATTACHMENT 2 MAR UP OF TECHNICAL SPECIFICATION

CRD Trip Devices 3.3.4

a. Four AC CRD trip breakers shall be OPERABLE for Unit(s) with the CRD/Reactor 3.3 INSTRUMENTATION Trip Breaker (RTB) Upgrade complete.

3.3.4 Control Rod Drive (CRD) Trip Devices I LCO 3.3.4 The following CRD trip devices shall be OPERABLE EI-~9 Two AC CRD trip breakers; 2J--~o Two DC CRD trip breaker pairs; and EI-0 Eight electronic trip assembly (ETA) relays.

for Unit(s) with the CRD/RTB Upgrade not I complete l APPLICABILITY: MODES 1 and 2, MODES 3, 4, and 5 when any CRD trip breaker is in the closed position and the CRD System is capable of rod withdrawal.

ACTIONS

t--______----__________________________--------

ImItJ Separate Condition entry is allowed for each CRD trip device.

CONDITION REQUIRED ACTION COMPLETION TIME A. One or more CRD trip A.1 Trip the CRD trip 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months breaker a breaker.

Ggiverse trip Functions inoperable. OR A.2 Remove power from 48 hours5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months the CRD trip breaker.

(continued)

I OR One or more required DC CRD breaker pair diverse trip Functions inoperable.

OCONEE UNITS 1, 2, & 3 3.3.4-1 Amendment Nos.[g0, 3 , & OO

CRD Trip Devices 3.3.4 ACTIONS (continued)

CONDITION I REQUIRED ACTION COMPLETION TIME B. One or more CRD trip B.1 Trip the CRD trip 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months break ad breaker.

OR reasons other than OR those in Condition A. One or more required DC B.2 Remove power from 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months CRD breaker pairs inoperable for reasons the CRD trip breaker. other than those in

_r Condition A.

C. One or mor ET C.1 Transfer affected 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months relays inoperable. CONTROL ROD group required to power supply with OPERABLE ETA relays.

OR C.2 Trip corresponding AC 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months CRD trip breaker(s).

4 4 D. Required Action and D.1 Be in MODE 3. 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months associated Completion Time not met in AND MODE 1, 2, or 3.

D.2.1 Open all CRD trip 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months breakers.

OR D.2.2 Remove power from all 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months CRD trip breakers.

I I (continued)

OCONEE UNITS 1, 2, & 3 3.3.4-2 Amendment Nos. , 396, & '00l

CRD Trip Devices 3.3.4 ACTIONS (continued)

CONDITION REQUIRED ACTION COMPLETION TIME E. Required Action and E.1 Open all CRD trip 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months associated Completion breakers.

Time not met in MODE 4 or 5. OR E.2 Remove power from all 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months CRD trip breakers.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.3.4.1 Perform CHANNEL FUNCTIONAL TEST. 31 days OCONEE UNITS 1, 2, & 3 3.3.4-3 Amendment Nos.[3,06, 3 6, & 0OO0

CRD Trip Devices l For Unit(s) with the CRD/RTB upgrade complete, the system has two separate paths (or B 3.3.4 I channels), with each path having two AC breakers inseries. In either case, B 3.3 INSTRUMENTATION four AC trip breakers for Unit(s) with CRD/Reactor Trip Breaker (RTB) upgrade complete or B3.3.4 Control Rod Drive (CRD) Trip Devices for Unit(s) with the CRD/RTB upgrade not complete. For Unit(s)

BASES I with the CRD/RTB upgrade not complete, lI lBACKGROUND The Reactor Protective System (RPS) contains multiple CRD trip devices:1 Also, In two AC trip breakers, two DC trip breaker pairs, and eight electronic trip either assembly (ETA) relay& She system has two separate paths (or channels), case with each path having one AC breaker in series with a pair of DC breakers and functionally in series with four ETA relays in parallel rgach path provides independent power to the CRDsgither path can provide sufficient power to operate the entire CRD System.

UFSAR, Chapter 7 (Ref. 1), illustrates the configuration of CRD trip devices. To trip the reactor, power to the CRDs must be removed.

Loss of power causes the CRD mechanisms to release the CONTROL RODS, which then fall by gravity into the core.

Power to CRDs is supplied from two separate sources through the AC trip circuit breakers. hese breakers are designated A and B, and their undervoltage trip coils are powered by RPS channels A and B, respectively.

For Unit(s) with the From the circuit breakers, the CRD power travels through voltage CRD/RTB upgrade complete, Figure 7.1, regulators and stepdown transformers.N/hese devices in turn supply UFSAR, Chapter 7 (Ref. redundant buses that feed the DC power supplies and the regulating rod, 1), Illustrates the APSR and auxiliary power supplies. For Unit(s) with the CRD/RTB upgrade not complete, configuration of Reactor Protection System (RPS) SWhe DC power supplies rectify the AC input and supply power to hold the Reactor Trip Modules safety rods in their fully withdrawn position. One of the redundant power (RTM's) and the trip breakers. For Unit(s) sources supplies phase A; the other, phase CC. Either phase being with the CRD/RTB energized is sufficient to hold the rod. Two breakers are located on the upgrade not complete, output of each power supply. Each breaker controls half of the power to Figure 7.1 a two of the four safety rod groups. The undervoltage trip coils on the two circuit breakers on the output of one of the power supplies is controlled by RPS channel C. The other two breakers are controlled by RPS channel D.

For Unit(s) with the CRD/RTB upgrade Ain addition to the DC power supplies, the redundant buses also supply complete, these breakers power to the regulating rod, APSR and auxiliary power supplies. These are designated A, B, C, and D and their undervoltage power supplies contain silicon controlled rectifiers (SCRs) that are gated on (trip) coils are powered by and off to provide power to, and remove power from, the phases of the RPS channels A, B. C, and CRD mechanisms. The gating control signal for these SCRs is supplied D, respectively. For Unit(s) through the closed contacts of the ETA relays. These contacts are referred with the CRD/RTB upgrade to as Eand F contactors, and are controlled by the C and D RPS channels not complete, respectively.

For Unit(s) with the CRDIRTB upgrade complete, these devices Inturn supply redundant buses that feed the Single Rod Power Supply (SRPS). For Unit(s) with the CRD/jTB upgrade not complete, OCONEE UNITS 1, 2, & 3 B 3.3.4-1 Amendment Nosj 396 30, & 3,060

BACKGROUND The AC breaker and DC breakers are in series in one of the power (continued) supplies; whereas, the redundant AC breaker and DC breakers are in The following applies to Unit(s) with the series in the other power supply to the CONTROL RODS. The logic CRD/RTB upgrade complete: required to cause a reactor trip is the opening of a circuit breaker in each of Two AC breakers (Aand C) are Inseries to the redundant power supplies. (The pair of DC circuit breakers on the feed one redundant train of the sRPs, output of the power supply are treated as one breaker.) This is known as a whereas the othertwo series AC breakers one-out-of-two taken twice logic. The following examples illustrate the (Band D) feed the other redundant train of operation of the reactor trip circuit breakers.

the SRPS. The minimum required logic required to cause a reactor trip Isthe opening of a circuit breaker In each parallel a. If the A AC circuit breaker opens:

path to the SRPS. This is known as a one-out-of-two taken twice logic. The following examples illustrate the operation 1 the input power to associated DC power supply is lost, and of the reactor trip circuit breakers.

2. the SCR supply from the associated power source is lost.

a. If the A or C circuit breaker opens SRPSus is lost r b. If the D DC circuit breaker(s) and F contactors open:

b. If In addition, the B or D circuit 1. the output of the DC power supply is lost, and breaker opens Input power to the other train of the SRPS's Is lost, which will result In the dropping of 2. when the F contactor opens, SCR gating power is lost.

all rods (except APSR's) Into the core. C. The combination of (a) and (b) causes a reactor trip.

The logic developed within the RPS Reactor Trip Modules will result In all AC breakers In summary, two tripped RPS channels will cause a reactor trip. For tripping Ifany two RPS channels receive a example, a reactor trip occurs if RPS channel B senses a low Reactor trip signa. Coolant Syster. (RCS) pressure condition and if RPS channel C senses a variable low RCS pressure condition. When the channel B bistable relay de-energizes, the channel trip relay de-energizes and opens its associated contacts. The same thing occurs in channel C, except the variable lower pressure bistable relay de-energizes the channel C trip relay. When the output logic relays in channel B and C de-energize, the B and C contacts in the trip logic of each channel's reactor trip module (RTM) open causing an undervoltage to each trip breaker. All trip breakers and ffA relay contactors open, and power is removed from all CRD mechanisms. All rods fall into the core, resulting in a reactor trip.

APPLICABLE Accident analyses rely on a reactor trip for protection of reactor core SAFETY ANALYSES integrity, reactor coolant pressure boundary integrity, and reactor building OPERABILITY. A reactor trip must occur when needed to prevent accident consequences from exceeding those calculated in the accident analyses.

The CONTROL ROD position limits ensure that adequate rod worth is I required OCONEE UNITS 1, 2, & 3 B 3.3.4-2 Amendment Nosf3 , 30X,& 3,O26

CRD Trip Devices B 3.3.4 BASES APPLICABLE available upon reactor trip to shut down the reactor to the required SDM.

SAFETY ANALYSES Further, OPERABILITY of the CRD trip devices ensures that all CONTROL (continued) RODS will trip when required. More detailed descriptions of the applicable accident analyses are found in the Bases for each of the individual RPS trip Functions in LCO 3.3.1, "Reactor Protective System (RPS)

Instrumentation."

The CRD trip devices satisfy Criterion 3 of CFR 50.36 (Ref. 2).

LCO The LCO requires all of the specified CRD trip devices to be OPERABLE.

Failure of any required CRD trip device renders a portion of the RPS inoperable and reduces the reliability of the affected Functions. Without reliable CRD reactor trip circuit breakers and associated support circuitry, a reactor trip may not reliably occur when initiated either automatically or manually.

All required CRD trip devices shall be OPERABLE to ensure that the reactor remains capable of being tripped any time it is critical.

OPERABILITY is defined as the CRD trip device being able to receive a reactor trip signal and to respond to this trip signal by interrupting power to the CRDs. Both of the CRD trip breaker's diverse trip devices and the

__. _ -_B ._ - _. I _- _ _ _-____ l.. I_ .mu __ ,_ a_-. L_--

For Unit(s) with the Dreamer ItselT must De Tunctioning properly Tor The Dreaver to De CRD/RTB upgrade not complete, -l`oth ETA relays associated with each of the three regulating rod groups and the two ETA relays associated with the auxiliary power supply must be OPERABLE to satisfy the LCO. The ETA relays associated with the APSR power supply are not required to be OPERABLE because the APSRs are (for Unit(s) with the not designed to fall into the core upon initiation of a reactor trip.

CRD/RTB upgrade not complete)

Requiring all breakers and ETA relays o be OPERABLE ensures that at least one device in each of the two power paths to the CRDs will remain OPERABLE even with a single failure.

APPLICABILITY The CRD trip devices shall be OPERABLE in MODES 1 and 2, and in MODES 3, 4, and 5 when any CRD trip breaker is in the closed position and the CRD System is capable of rod withdrawal.

The CRD trip devices are designed to ensure that a reactor trip would occur if needed. Since this condition can exist in all of these MODES, the CRD trip devices shall be OPERABLE.

OCONEE UNITS 1, 2, & 3 B 3.3.4-3 Amendment Nos4oX,30,9/& 3I6 j

CRD Trip Devices B 3.3.4 BASES (continued)

For Unit(s) with the A Note has been added to the ACTIONS indicating separate Condition CRD/RTB upgrade entry is allowed for each CRD trip device.

complete, Condition A applies when:

A.1 and A.2 One diverse trip Function Condition A represents reduced redundancy in the CRD trip Function.

(undervoltage or -Condition A applies when:

shunt trip device) is inoperable in . One diverse trip Function (undervoltage or shunt trip device) is one or more inoperable in one or more CRD trip breaker(s) or breaker pair; or CRD trip breaker(s). . One diverse trip Function is inoperable in both DC trip breakers associated with one protective channel. In this case, the inoperable trip For Unit(s) with the Function does not need to be the same for both breakers.

CRD/RTB upgrade not complete, If one of the diverse trip Functions on a CRD trip breaketr/ekeair

/ becomes inoperable, actions must be taken to preclude the inoperable CRD trip device from preventing a reactor trip when needed. This is done

/ by manually tripping the inoperable CRD trip breaker or by removing power from the inoperable CRD trip breaker. Either of these actions places the (or breaker pair for affected CRDs in a one-out-of-two trip configuration, which precludes a CRD/RTs upgrade not single failure from preventing a reactor trip. The 48 hour5.555556e-4 days 0.0133 hours 7.936508e-5 weeks 1.8264e-5 months Completion Time complete) has been shown to be acceptable through operating experience.

B.1 and B.2 Condition B represents a loss of redundancy for the CRD trip Function.

(or breaker pair for Condition B applies when both diverse trip Functions are inoperable in one Unit(s) with the or more trip breakerso er as.I CRD/RTB upgrade not complete) Required Action B.1 and Required Action B.2 are the same as Required Action A.1 and Required Action A.2, but the Completion Time is shortened.

The 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Completion Time allowed to trip or remove power from the CRD trip breaker allows the operator to take all the appropriate actions for the inoperable breaker and still ensures that the risk involved is acceptable.

rC.1and .2 lCRD/RTI3 upgrade complete.l Condition C represents a loss of redundancy for the CRD trip Function.

Condition C applies when one or more ETA relays are inoperable. The preferred action is to restore the ETA relay to OPERABLE status. If this cannot be done, the operator can perform one of two actions to eliminate OCONEE UNITS 1, 2, & 3 B3.3.4-4 Amendment Nosf396 30,& 3,dO

CRD Trip Devices B 3.3.4 BASES ACTIONS C.1 and C.2 (continued) reliance on the failed ETA relay. This first option is to switch the affected CONTROL ROD group to an alternate power supply. This removes the failed ETA relay from the trip sequence, and the unit can operate indefinitely. The second option is to trip the corresponding AC CRD trip breaker. This results in the safety function being performed, thereby eliminating the failed ETA relay from the trip sequence. The 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months Completion Time is sufficient to perform the Required Action.

D.1, D.2.1. and D.2.2 With the Required Action and associated Completion Time of Condition A, B, or C not met in MODE 1, 2, or 3, the unit must be brought to a MODE in which the LCO does not apply. To achieve this status, the unit must be brought to MODE 3, with all CRD trip breakers open or with power from all CRD trip breakers removed within 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months . The allowed Completion Time of 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months is reasonable, based on operating experience, to reach MODE 3 from full power conditions in an orderly manner and without challenging unit systems.

E.1 and E.2 With the Required Action and associated Completion Time of Condition A, B, or C not met in MODE 4 or 5, the unit must be brought to a MODE in which the LCO does not apply. To achieve this status, all CRD trip breakers must be opened or power from all CRD trip breakers removed within 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months . The allowed Completion Time of 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months is reasonable, based on operating experience, to open all CRD trip breakers or remove power from all CRD trip breakers without challenging unit systems.

SURVEILLANCE SR 3.3.4.1 REQUIREMENTS SR 3.3.4.1 is to perform a CHANNEL FUNCTIONAL TEST every 31 days.

This test verifies the OPERABILITY of the trip devices by actuation of the end devices. Also, this test independently verifies the undervoltage and shunt trip mechanisms of the trip breakers. The Frequency of 31 days is based on operating experience, which has demonstrated that failure of more than one channel of a given function in any 31 day interval is a rare event.

OCONEE UNITS 1, 2, & 3 B 3.3.4-5 Amendment Nos[396, 30,& 3do

CRD Trip Devices B 3.3.4 BASES (continued)

REFERENCES 1. UFSAR, Chapter 7.

2. 10 CFR 50.36.

OCONEE UNITS 1, 2, & 3 B 3.3.4-6 Amendment Nos.[3@,

30/,& 3,06

March 15, 2004 Attachment 3 Technical Justification

March 15, 2004 Page 1 Attachment 3 Technical Justification Overview The Control Rod Drive (CRD) Reactor Trip Breakers (RTBs),

including cabinets, are being replaced to address obsolescence and age-related degradation issues. This work is being performed as part of the overall digital Control Rod Drive Control System (CRDCS) upgrade, which replaces the existing relay based CRDCS with a solid-state programmable digital CRDCS. This upgrade also includes replacing the electronics and controls and the CRD RTB cabinets located in the Cable Room and replacing the Operator Control Panel (OCP) located in the Control Room. The replacement of the RTBs, although included in the overall modification, is not a digital upgrade. The digital upgrade involves the CRD control system only. The portion of the modification requiring a Technical Specification change to allow implementation is the RTB replacement.

As part of the RTB replacement, Duke is replacing the existing two AC RTBs and four DC RTBs (refer to Figure 1 on page 10) with four AC RTBs (refer to Figure 2 on page 11).

The existing 2-AC RTB cabinet and the 4-DC RTB cabinet will be replaced by a single 4-AC breaker cabinet in the same location at the old 2-AC breaker cabinet. Duke proposes to revise TS 3.3.4, "Control Rod Drive (CRD) Trip Devices," to address the new configuration.

The CRD/RTB upgrade addresses equipment obsolescence and age-related degradation issues and will improve reliability of the RTBs throughout the extended life of Oconee Nuclear Station.

Description of the Technical Specification Change The proposed Technical Specification change revises TS 3.3.4 and associated TS Bases.

TS 3.3.4 - Control Rod Drive (CRD) Trip Devices The Limiting Condition for Operation (LCO) is partitioned into two parts to specify requirements based on the status of

March 15, 2004 Page 2 the CRD/RTB replacement for each Oconee Unit. LCO 3.3.4.a requires that four AC CRD trip breakers be OPERABLE for Unit(s) with the CRD/RTB upgrade complete. LCO 3.3.4.b retains the existing requirements for Unit(s) with the CRD/RTB upgrade not complete. For Unit(s) with the CRD/RTB upgrade complete the Condition associated with a DC CRD trip breaker pair is eliminated since each breaker pair is replaced with an AC trip breaker. This is accomplished by dividing the Condition into two parts with the second part only applying to Unit(s) with the CRD/RTB upgrade not complete. The Required Action and Completion Time associated with each Condition remains the same. For Unit(s) with the CRD/RTB upgrade complete, LCO Condition C no longer applies since the new system will not contain ETA's.

The associated Technical Specification Bases were revised to reflect the changes to the Technical Specifications.

After completion of the modification on all three units, Duke will request a Technical Specification change to remove obsolete requirements.

Justification for the Technical Specification Change The new and the old trip system provide the same safety related function and are identical in design in that the breakers, under the control of the Reactor Protective System (RPS), are placed in the two power feeds to the Control Rod Drive Control System. These breakers are used to interrupt the power to the Control Rod Drive Mechanisms power supplies causing the rods to drop.

The CRDM's are designed with a split/hinged rotor containing roller nuts at one end. The split rotor allows it to engage and disengage the roller nuts from a leadscrew which is coupled to a control rod. Once the mechanism is energized the split rotor will-be pulled outward toward the stator engaging the roller nuts with the leadscrew. When de-energized the hinged rotor will open, disengage the roller nuts from the leadscrew and the rod will drop into the core.

The ability to hold and move a rod when it is energized as well as disengage and drop the rod when de-energized makes the CRDM mechanically safety related. The necessity to

March 15, 2004 Page 3 remove power from the mechanisms such that they will de-energize makes the RTBs safety related. What falls between these two items (i.e., currently the old Control Rod Drive Control System) is of no consequence as long as the power necessary for the CRDM stators to remain energized can be interrupted.

The existing system removes power via two AC breakers, four DC breakers and eight electronic trip assemblies (ETA)

(reference Figure 1 on page 10). Opening the 2 AC breakers removes all power to the CRD mechanisms. If one of these breakers were to fail then all power would still be removed from the mechanisms as follows: Power to the safety groups (1 - 4) would be removed by opening power to their holding phases via safety related DC breakers. Power to the regulating rods would be removed by interrupting the gating supplies to the SCRs that provide them power (non-lE RPS trip) via the electronic trip assemblies. The gating control signal for the SCRs is supplied through the closed contacts of the ETA relays.

The new Trip Breaker arrangement allows direct correlation between the four RPS Trip Channels (A, B, C, and D) and the four new AC Trip Breakers (A, B, C, and D). The new system ensures that power is removed from the CRDMs in a simpler method by adding an extra AC breaker in each train of power and eliminating the need for DC breakers and non-lE RPS trips (reference Figure 2 on page 11). In this setup as long as one of the two breakers opens (i.e. a single failure results in one breaker not opening) in each train then all power will be removed from the mechanisms resulting in their release.

The safety related portion of the breaker is the undervoltage trip assembly (UVTA). There is no interface between the UVTA in either the new or old control systems.

A backup to this device is the shunt trip assembly (STA).

This device is under control of the RPS (as a backup to the UVTA) and the control system as a Source Interrupt Device (SID). This is a non-safety related interface between the 2 systems.

The RTB cabinetry also houses the Reactor Trip Confirm (RTC) circuitry as well as the control power transformers that provide control power to the control system. RTC circuitry

March 15, 2004 Page 4 is developed by monitoring the auxiliary contacts on the breaker and sending a contact status to the Breaker Interface Cubicle where the contact status is multiplied using additional relays. These are non-safety related devices that are mounted inside separate cubicles of the safety related cabinetry. This interface exists on both the old and new system. The breaker is also monitored via additional auxiliary and relay contacts for interface with various non-safety related plant monitoring systems such as the Annunciator, Events Recorder and Plant Computer.

In summary, the new CRD/RTB configuration continues to fulfill the safety-related function of removing power to the CRDMs. There are no safety related/non-safety related interfaces that can prevent this function from occurring. As such, the proposed TS change for the new configuration will continue to ensure the safety-related RTB function will be fulfilled.

Modification Details Description of New CRD/RTB Design A reactor trip is initiated on both the old and new systems by removing power from the CRDMs. The advantage of this design is that the only safety related components required are the CRDMs and RTBs. The CRDMs must be designed to release the Control Rods when power is removed, and the RTBs, must be designed to open on command to remove power from the CRDMs.

Similar to the existing system, the new digital Control Rod Drive Control System (CRDCS) provides power to the CRDMS via the Single Rod Power Supplies (SRPS) from two independent power supplies. Each of these power supplies will connect to the digital CRDCS via two RTBs connected in series (refer to Figure 2 on page 11 for a simplified diagram). This arrangement of parallel feeds, each with redundant breakers, operates in a one out of two taken twice configuration to interrupt power to the CRDMs. This configuration is designed such that a single failure of any breaker, either in the open or closed position, will not cause or prevent a reactor trip.

RTBs A, B, C and D are actuated via RPS Channels A, B, C and

March 15, 2004 Page 5 D, respectively, and are considered Nuclear Safety Related/Class 1E. The safety function of these breakers is to open upon command from the RPS. This action is performed by the RPS de-energizing a normally energized under voltage (UV) coil contained within the breaker resulting in the breaker opening. Additionally, an isolated, non-safety related diverse trip of the breakers is initiated in the RPS which de-energizes a relay, which in turn energizes the shunt trip coils of these breakers, which also results in the breaker opening.

Channel Independence The RPS is designed with four independent and redundant channels, each connected to one of four AC RTBs. The acceptability of the independence and redundancy of the RPS is assumed since this system will not be changed per this modification. The four replacement RTBs will be housed in two cabinet assemblies of four cubicles each. The design function of the first cabinet is to interrupt the train A power to the digital CRDCS and will consist of RTBs A and C connected in series. The design function of the second cabinet is to interrupt train B power to the digital CRDCS and will consist of RTBs B and D connected in series.

Physical and electrical separation is maintained via the breaker assemblies being mounted in individual cubicles of the two Train related cabinets. The replacement RTB cabinets have been seismically qualified by testing an additional set of equipment specifically for such purpose. The RTB cabinets are seismically mounted. Electrical separation between the two breakers in the same cabinet is maintained by routing the RPS cabling to the breakers via conduit once it enters the cabinet assemblies.

The new RTB cabinets will be located in the cable room of the control complex in the plant Auxiliary Building. This location is analyzed and has been determined to be a mild environment. The two new RTB cabinets will be located in the previous location of the 2-AC breaker cabinets. The new RTB cabinets will not be exposed to any post design basis event harsh environments.

Since the under voltage trip assembly (UVTA) is actuated by cabling that runs external to the breaker cabinets, the

March 15, 2004 Page 6 effect of open and short circuited conductors was considered.

Either an open or short circuited conductor will result in a loss of voltage to the UVTA resulting in a breaker trip.

Single Failure Criteria As a part of a protection system, the RTBs must meet IEEE-279,"Criteria for Protection Systems for Nuclear Power Plants". Also utilized during the design of the RTB replacement were IEEE-379, "Standard Application of the Single Failure Criterion to Nuclear Power Generating Class 1E Systems", USNRC Regulatory Guide (RG) 1.53, "Application of the Single Failure Criterion to Nuclear Power Plant Protection Systems." and USNRC RG 1.75, "Physical Independence of Electric Systems.0 During.normal operation all four of these breakers will be closed. When the RPS detects a condition necessitating a reactor trip, each RPS channel will send a trip signal to its respective RTB. Once this occurs there are only two possible responses from the reactor trip breaker assemblies, i.e., the breaker trips (the proper response) or the breaker does not trip (i.e., the single failure). This ensures that given a single RTB failure, the safety function of removing power to the CRDM's will be accomplished. There are no credible common cause or common mode failures that have been identified as part of the single failure analysis performed on the RTBs that would prevent this response. One common cause failure considered as part of the design was a seismic event that would result in a loss of geometry of the breaker cubicles. RTB failure to trip due to this type of common mode failure is precluded by.the seismic qualification of the breakers. A second cause of a common mode failure would be exposure to a harsh environment. This is not considered credible due the location of the breaker assemblies. A third common cause failure could be the result of EMI or RFI. This is not considered credible since the UVTA is inherently a low impedance device and thus not susceptible to this class of failure. Also the breakers do not use any embedded analog or digital devices to perform their trip function.

March 15, 2004 Page 7 Design Criteria The breakers are designed to meet the following criteria:

Rated for 600VAC (+/- 10%)

Rated for 600 Amp continuous

Maximum open time

80 ms

22,000 Amps fault at 635 VAC

UV coil dropout at minimum of 30% and pickup at maximum of 85% of rated voltage

Shunt trip shall operate correctly over the range of 88.7 to 134.6 VAC

Qualified life of breakers is to be 40 years without component replacement

Cyclic life shall be a minimum of 1500 cycles

Operating temperature range of 32 to 130 degrees F

Operating relative humidity range of 5% to 95%

Seismic Category 1 as defined by USNRC RG 1.29 "Seismic Design Classification"

Seismically qualified in accordance with IEEE 344-1975 and USNRC RG 1.100

ANSI C37.13 "Low voltage AC power circuit breakers and AC power circuit protectors"

ANSI C37.16 "Preferred ratings, related requirements and application recommendations for Low voltage Power Circuit Breakers and AC power Circuit Protectors"

ANSI C37.19 "Safety Requirements for Low Voltage AC Power Circuit Breakers and Switchgear Assemblies"

ANSI C37.50 "Test Procedures for Low Voltage AC Power Circuit Breakers used in Enclosures."

The new design is considered better than existing design in two ways. First, the new Cutler Hammer DS II breakers are manufactured using a well developed and proven breaker design. The DS II trip breakers are an updated version of the successful line of DS I breakers. The new breaker trip mechanism used is the same as contained in the Westinghouse family of DS I series breakers which are widely used as RTBs in the United States. The DS II and DS I breakers are from the same company. The nuclear breaker products of Westinghouse were acquired by Cutler-Hammer. These new qualified breakers will be used to replace the original, obsolete, and increasingly difficult to maintain General

March 15, 2004 Page 8 Electric AK-15 and AK-25 breakers. Secondly, overall reliability of the system will be increased with the new equipment. The design function of the new equipment mimics the original and accomplishes the same function of removing power from the CRDM's, given a single failure, and drops all of the rods in the core. The existing design uses a larger parts count of active components (two AC breakers, four DC breakers and eight Electronic Trip Assemblies) to accomplish the design basis requirements of the system. The new system is a much improved design, utilizing only four AC breakers, and reduced parts count, thereby reducing the susceptibility of the system to equipment failures and improving reliability. The number of breakers is reduced from 6 to 4 and the Electronic Trip Assemblies are removed.

This design is similar to the design currently used at Davis Besse. The Davis Besse design is shown as more reliable than the Oconee design in BAW-10167A, Supplement 3, "Justification for Increasing Reactor Trip System On-line Test Intervals."

The NRC Safety Evaluation Report for this topical was transmitted to Framatome Technologies, Inc. by letter dated January 7, 1998.

Impact on Anticipated Transient Without Scram (ATWS)

Requirements Duke reviewed commitments related to ATWS design requirements and confirmed that implementation of the digital CRDCS will not negatively impact ATWS systems at Oconee. Duke provided the final design description for ATWS modification by letter dated August 30, 1989. The NRC provided the safety evaluation for the ATWS design by letter November 29, 1989.

The sensor and logic portions of the ATWS Mitigating System Actuation Circuitry (AMSAC)/Diverse Scram System (DSS) system will not be changed by this modification. The actuation portion of the DSS subsystem, which is contained within the CRDCS system, will be modified. The primary design requirement of the DSS system is that it be diverse from the RPS. The diversity of DSS from RPS will not be impacted.

The digital CRDCS will initiate a reactor trip, when commanded by DSS, by removing the gating pulses from the silicon controlled rectifiers (SCRs) that create the DC power necessary to energize the CRDM stators. None of the PLC's,

March 15, 2004 Page 9 solid state relays or single rod power supplies used to implement this function are used for any purpose in the RPS.

The new DSS actuation design will be better than the current design in that it will use highly reliable triple modular redundant equipment to drop all of the control rods into the core. The current system uses obsolete and increasingly maintenance intensive original equipment to drop a portion of the rods into the core (Groups 5, 6, and 7) upon actuation by DSS.

March 15, 2004 Attachment 3 Page 10 FIGURE 1 Existing RTB Configuration A Power B Power Supply Reactor Trip Switch Supply AC AC Breaker Breaker I 600 VAC, 30 600 VAC, 30 120 VAC, 60D 120 VAC, 60 DC DC Breakers Breakers

March 15, 2004.

Attachment 3 Page 11 FIGURE 2 New RTB Configuration A Power B Power Supply Reactor Trio Switch Supply 2

A --- RRSA RPSBB- -- B I I I

C RPS C RPS D --

5---- D 600 VAC, 30) 120 VAC, 60D

March 15, 2004 ATTACHMENT 4 NO SIGNIFICANT HAZARDS CONSIDERATION

March 15, 2004 Page 1 Attachment 4 No Significant Hazards Consideration Pursuant to 10 CFR 50.91, Duke Energy Corporation (Duke) has made the determination that this amendment request involves a No Significant Hazards Consideration by applying the standards established by the NRC regulations in 10 CFR 50.92.

This ensures that operation of the facility in accordance with the proposed amendment would not:

(1) Involve a significant increase in the probability or consequences of an accident previously evaluated:

The proposed LAR modifies the Technical Specifications to incorporate new TS requirements associated with the new Control Rod Drive (CRD)/Reactor Trip Breaker (RTB) configuration. The proposed LAR will continue to ensure that the CRD trip devices will be operable to ensure that the reactor remains capable of being tripped at any time it is critical. Reliable CRD reactor trip circuit breakers and associated support circuitry provide assurance that a reactor trip will occur when initiated.

The new RTBs will have the same seismic and quality group qualifications as the existing components in the CRDCS system. The new RTBs will enhance the reliability of the system by resolving age-related degradation issues and replacing obsolete equipment. Therefore, the proposed LAR does not involve a significant increase in the probability or consequences of an accident previously evaluated.

(2) Create the possibility of a new or different kind of accident from any kind of accident previously evaluated:

The proposed LAR modifies the Technical Specifications to incorporate new TS requirements associated with the new CRD/RTB configuration. The systems affected by implementing the proposed changes to the TS are not assumed to initiate design basis accidents. Rather, the systems affected by the changes are used to mitigate the consequences of an accident that has already occurred.

The proposed TS changes do not affect the mitigating function of these systems. The reliability of the mitigating systems will be improved by implementation of

March 15, 2004 Page 2 the RTB Upgrade. Consequently, these changes do not alter the nature of events postulated in the Safety Analysis Report nor do they introduce any unique precursor mechanisms. Therefore, the proposed amendment will not create the possibility of a new or different kind of accident from any accident previously evaluated.

(3) Involve a significant reduction in a margin of safety.

The proposed TS changes do not unfavorably affect any plant safety limits, set points, or design parameters.

The changes also do not unfavorably affect the fuel, fuel cladding, RCS, or containment integrity. Therefore, the proposed TS change, which adds TS requirements associated with the CRD/RTB upgrade, do not involve a significant reduction in the margin of safety.

Duke has concluded, based on the above, that there are no significant hazards considerations involved in this amendment request.

ML040850418

Text

Subject:

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