ML19316A480

Proposed Changes to Tech Spec 3.7 Re Limiting Conditions for Operation & Surveillance Requirements for 125 Volt Distribution Sys

ML19316A480
Person / Time
Site:	Oconee
Issue date:	02/01/1978
From:	DUKE POWER CO.
To:
Shared Package
ML19316A475	List: ML19316A474 ML19316A480
References
NUDOCS 7912110807
Download: ML19316A480 (10)

Text

,

3.7 AUX 1LIARY ELECTRICAL SYSTEMS 4

Applicability Applies to the availability of off-site and on-site ele:trical power for station operation and for operation of station auxiliaries.

4 Obj ec t ive To define those conditions of electrical power availability necessary to provide for safe reactor operation and to provide for continuing availability cf engineered safety features systems in an unrestricted manner and to pre-scribe safety evaluction and reporting requirements to be followed in the event that the auxiliary electric power systems become degraded.

Specification 3.7.1 Except as permitted by 3.7.2, 3.7.3, 3.7.4, 3.7.5, 3.7.6 and 3.7.7, the reactor shall not be heated above 200 F unless the following conditions are met.

(a) At least two 230 kV transmission lines, on separate towers, shall be in servicc.

(b) Two startup transformers shall be operable and available to the unit's 4160 volt Main Feeder Buses No. I and No. 2.

(c) One operable Keowee hydro unit shall be available to supply power through the Underground Feeder Bus, Transformer CT4 and the 4160 volt Standby Buses No. I and No. 2 to the units 4160 volt Main Feeder Buses No. I and 2. The second Keowee hydro unit shall be availab13 : supply power auto =atically through a startup transforme: +

the units 4160 volt Main Feeder Buses No. I and 2.

(d) The two 4150 volt main feeder buses shall be energized.

(e) The three 4160 volt Engineered Safety Features switchgear buses shall be energized.

(f) Three 600 volt load centers plus the three 600 volt-208V Engineered Safety Features MCC Buses shall be energized.

(g) For each unit, all 125 VDC distribution centers, diode monitors, l diodes required to supply the unit's four 125 VDC instrumenta-tion and control panel boards and the 120 VAC auxiliary control power panelboards shall be operable. The 125 VDC dnstrumentation and control batteries with their respective chargers shall be operable as fo? lows:

l 1. For operation of Unit 1 only, ICA or ICB, and 2CA or 2CB Unit 2 only 2CA or 2CB., and 3CA or 3CE Unit 3 only 3CA or 3CB, and ICA or ICB 3.7-1 -

l

2. For op2 ration of any two units, ICA or ICB, 2CA or 2CB, and 3CA or 3CB.

3. For operation of all three units, five of the six batteries with their associated chargers.

(h) Both of the 125 VDC 230 kV switching station batteries with their respective chargers, distribution centers, and panel boards shall be operable.

(i) Both of the 125 VDC Keowee batteries with their respective chargers and distribution centers shall be operable.

(j) The level of the Keowee Reservoir shall be at least 775 feet above sea level.

3.7.2 During het standby or power operation, provisions of 3.7.1 may be modified to allow the following conditions to exist:

(a) Any one of the following electrical distribution components may be inoperable for test or maintenance for the time period specified:

1. One of the two required startup transformers may be removed from service for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> provided it is expected to be restored to service within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> and the other required startup transformer is available and is aligned for automatic connection to the unit's main feeder bus, i

2. One Keowee hydro unit may be inoperable for periods no* I exceeding 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for test or maintenance provided the l operable Keowee hydro unit is connected to the underground j feeder circuit and is verified operable within one hour of the loss and every eight hours thereafter.

3. The underground feeder circuit may be inoperable for periods l not exceeding 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for test and maintenance. j

4. Both of the following items may be inoperable for periods not exceeding 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />s:

a. One complete single string (i.e., 4160V switchgear,  ;

600V load center, 600-208 MCC, and their loads) of each unit's 4160V Engineered Safety Features Power Syr. tem,

b. One 4160 volt sL_ndby bus or one 4160 volt main feeder bus in each unit.

5. One 125 VDC instrumentation and control panel board and its associated loads may be inoperable for periods not exceeding 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

(b) The following DC distribution components may be inoperable for test or maintenance for periods not exceeding 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />s:

3.7-2

1. One complete single string (i.e., 125VDC battery, charger, distribution center, and panel boards) of the 125 VDC 230 kV Switching Station

2. One complete single string (i.e., 125VDC battery, charger, and distribution center) of the Keowee 125VDC Power System may be inoperable provided the remaining string of Keovee is operable and electrically connected to an operable Keowee hydro unit.

3. One complete single string (i.e.,125VDC battery, charger, distribution center, and associated isolating and transfer diodes excluding the panel boards) of any units 125VDC Instrumentation and Control Power System.

3.7.3 In the event that the conditions of Specification 3.7.1 are not met within the time specified in Specification 3.7.2, except as noted below in Specification 3.7.4, 3.7.5, 3.7.6, and 3.7.7 the reactor shall be placed in a hot shutdown condition within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. If these requirements are not met within an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, the reactor shall be placed in the cold shutdown condition within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

3.7.4 In the event that all conditions in Specification 3.7.1 are met ex-cept that one of the two Keowee hydro units is expected to be un-available for longer than the test or maintenance period of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the reactor may be heated about 200 F if previous:y shutdown or be permitted ta remain critical or be restarted provided the following restrictions are observed.

(a) Prior to heating the reactor above 200 F or prior to the re-start of a shutdown reactor or within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or the loss of one Keowee hydro unit, the 4160 volt standby buses shall be energized by a Lee gas turbine through the 100 kV circuit.

The Lee gas turbine and 100 kV transmission circuit shall be electrically separate from the system grid and non-safety-related loads.

(b) The remaining Keowee hydro unit shall be connected to the under-ground feeder circuit and this path shall be verified operable within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and weekly thereafter.

(c) The remaining Keowee hydro unit shall be available to the overhead transmission circuit but generation to the system grid shall be prohibited except for periods of test.

(d) Operation in this mode is restricted to periods not to exceed 45 days and the provisions of this specification may be utilized without prior NRC approval only once in three years for each Keowee. hydro unit. Office of Inspection and Enforcement, Region II, will be notified within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

3.7.: In the event that all conditions of Specification 3.7.1 are met ex-cept that all 230 kV transmission lines are lost, the reactor shall be permitted to remain critical or be restarted provided the following restrictions are observed:

3.7-?

(a) Prior to the restart of a shutdown reactor or within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of losing all 230 kV transmission lines for an operating reac-tor, the 4160 volt standby buses shall be energized by one of the Lee gas turbines through the 100 kV transmission circuit.

The Lee gas turbine and the 100 kV transmission circuit shall

=

be completely separate from the system grid and non-saf ety-related loads.

(b) The reactor coolant T #"E shall be above 525 F. Reactor coolant pumg power may be used to elevate the temperature from 500 F to 525 in the case of restart. If T decreases below 500 F, restart is not permitted by this #"E specification.

(c) If all 230 kV transmission lines are lost, restore at least one of the inoperable 230 kV of f site sources to operable status within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or be in at least hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. With only one offsite source restored, restore at least two 230 kV offsite circuits to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> from time of initial loss or be in at least hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

(d) After loss of all 230 kV transmission lines, this information shall be reported within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to the Of fice of Inspection and Enforcement, Region II. If the outage is expected to exceed 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, a written report shall be submitted detailing the cir-cuestances of the outage and the estimated time to return the 230 kV transmission lines to operating condition.

3.7.6 In the event that all conditions of Specification 3.7.1 are met, and planned tests or maintenance is required which will make both Keowee units unavailable, the 4160 volt standby buses shall first be ener-gized by a Lee gas turbine through the 100 kV transmission circuit

and shall be separate f rom the system grid and non-saf ety-related i loads. The reactor shall then be permitted to remain critical for periods not to exceed 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> with both Keowee units unavailable.

Prior to hot restart of a reactor from a tripped condition, the causes and the effects of the shutdown shall be established and analyzed. A restart will be permitted if the cause of such trips are the result of error or of minor equipment malfunctions. A restart will not be permitted if the trip is a result of system transients or valid pro-tection system action.

3.7.7 In the event that all conditions of 3pecification 3.7.1 are met except that both Keowee hydro units become unavailable for unplanned reasons, the reactor shall be permitted to remain critical for periods not to exceed 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> provided the 4160 volt standby buses are energized within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> by the Lee gas turbine through the 100 kV transmission circuit and it shall be separate from the system grid and all offsite non-saf ety-related loads.

3.7-4

Prior to hot restart of a reactor froc a tripped condition, the causes and the effects of the shutdown shall be established and analy:ed. A restart will be permitted if the cause of such trips are the result of error or of minor equipment malfunctions. A restart will not be per-mitted if the trip is a result of system transients or valid protec-tion system action.

3.7.6 Any degradation beyond Specification 3.7.2, 3.7.4, 3.7.5, 3.7.6, or 3.7.7 above shall be. reported to the Office of Inspection and Enforce-ment, Region II, within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. A safety evaluation shall be per-formed by Duke Power Company for the specific situation involved vnich justifies the safest course of action to be taken. The results of this evaluation together with plans for expediting the return to the l unrestricted operating conditions of Specification 3.7.1 above shall be submitted in a written report to the Office of Nuclear Reactor Regulation with a copy to the Office of Inspection and Enforcement, i

Region II, within five days.

j Bases The auxilfary electrical power systems are designed to supply the required Engineered Safeguards loads in one unit and safe shutdown loads of the other two units and are so arranged that no single contingency can inactivate enough i engineered safety features to jeopardize plant safety. These systems were designed to meet the following criteria:

" Alternate power systems shall be provided and designed with adequate independency, redundancy, capacity and testability to permit the functions required of the engineered safety features of each unit."

The auxiliary power system meets the above triteria and the intent of AEC Criterion

17. The adequacies of the AC and DC systems are discussed below as are the bases f or permitting degraded conditions for AC power.

Capacity of AC Systems l

The auxiliaries of two units in hot shutdown (6.0MVa each) plus the auxiliaries I activated by ESG signal in the other unit (4.8 MVa) require a total AC power  !

capacity of 16.8 MVa. The continuous AC power capacity available from the on-site power systems (Keowee Hydro Units) is 20 MVa (limited by transformer CT4) if furnished by the underground circett or 30 MVa (limited by CT1 or CT2) if furnished through the 230 kV off-site transmission lines. Capacity available f rom the backup 100 kV of f-site transmission line (Lee Station Gas Turbine Generator) is 20 MVa (limited by CTS).

l Thus, the minimum available capacity from any one of the multiple sources of AC power, 20 MVa, is adequate.

1 3.7-5 I

e Canacity of DC Svstems Normally, for each unit AC power is rectified and supplies the DC system buses as well as keepit.g the storage batteries on these buses in a charged state. Upon loss of this normal AC source of power, each unit's DC auxiliary systems important to reactor safety have adequate stored capacity (ampere-hours) to independently

' supply their required emergency loads for at least one hour. One hour is considered to be conservative since there are redundant sources of AC power providing energy to these DC auxiliary systems. The loss of all AC power to any DC system is ex-pected to occur very infrequently, and for very short periods of time. The following tabulation demonstrates the margin of installed battery charger rating and battery capacity when compared to one hour of operation (a) with AC power (in amps) and (b) without AC power (in ampere hours) for each of the three safety-related DC systems ins talled at Oconee:

A. 125 VDC Instrumentation and Control Power System Charger XCA, XCB, or XCS a. 600 amps each Battery XCA or XCB Capacity b. 600 ampere-hours each (X = 1, 2, or 3)

Combined total connected loads a. Inrush (2 see) - 1160 a=ps on both 125 VDC 1 6 C buses XDCA and EDCB next 59 min. - 506 amps during 1st hour of LOCA b. 516.9 ampere-hours (x = 1, 2, or 3)

B. 125 VDC Switching Station Power System Charger SY-1. SY-2, or SY-s Rating a. 50 amps each Battery SY-1 or SY-2, Capacity b. 14.4 ampere-hours Active load per battery a. Inrush (2 seconds) - 130 amps during 1st hour of LOCA next 59 min. - 10 amps

b. 12 ampere-hours C. 125 VDC Keowee Station Power System Charger No.1, No. 2 or Standby Rating a. 200 amps each i Battery No. 1 or No. 2 Capacity b. 200 ampere-hours l Active load per battery a. Inrush (14 seconds) - 1031 amps during ist hour of LOCA next 59 min. - 179.4 amps

b. 193.6 ampere-hours Redundancy of AC Systems There are three 4160 engineered safety feature switchgear buses per unit. Each bus can receive power from either of the two 4160 main feeder buses per unit.

Each feeder bus in turn can receive power from the 230 kV switchyard through the s tartup transformers, through the unit auxiliary transformer by backfeeding through the main step-up transformer, or from the 4160V standby bus. Another unit's start-up transformer serving as an alternate supply can be placed in service in one hour.

i 3.7-6 i

.-r The standby bus can receive power from the Hydro Station through the underground feeder circuit or from a combustion turbine generator at the Lee Steam Station over an isolated 100 kV transmission line. The 230 kV switchyard can receive power froc '

j the on-site Keowee Hydro station or from several off-site sources via transmission lines which connect the Oconee Station with the Duke Power system power distribution network.

Redundanev of DC Svstems ]

A. 125 VDC Instrumentation and Control Power System f The 125 VDC Instrumentation and Control (16C) Power Systec consists of two batteries, three battery chargers, and two 16C distribution centers per unit. All reactor protection and engineered safety features loads on this system can be powered from either the Unit I and Unit 2 or the Unit 2 and Unit 3 or the Unit 3 and Unit 1 125 VDC I6C distribution centers. The 125 VDC I6C distribution centers are normally supplied from their associated battery and sharger. For one unit, in the event that only one of its cat-teries and associated chargers are operable, both I&C distribution centers will be tied together allowing operation of the DC loads from the unit's operable Dattery and charger. As shown above, one 16C battery (e.g., ICA) can supply both I&C distribution centers (e.g., IDCA and IDCB) and their '

assvciated panelboard loads. Also, one of the three battery chargers for each unit can supply all connected ESF and reactor protection loads.

5. 125 VDC Switching Station Power System There are two essentially independent subsystems each complete with an AC/DC power supply (battery charger), a battery bank, a battery charger bus, motor control center (distribution panel). All saf ety-related equ.pment and the i relay house in which it is located are Class 1 (seismic) design. Each sub-i system provides the necessary DC power to:

I

a. Continuously monitor operations of the protective relaying.

b. Isolate Oconee (including Keowee) from all external 230 kV grid faults,

c. Connect on-site power to Oconee from a Keowee hydro unit or,

d. Restore off-site power to Oconee from non-faulted portions of the cxternal 230 kV grid.

3 Provisions are included to manually connect a standby battery charger to either battery / charger bus.

C. 125 VDC Keowee Station Power System There are essentially two independent physically separated Class I (seispic) subsystems, each complete with an AC/DC power supply (charger) a battery bank, a batter / charger bus and a DC distribution center. Each subsystem l

provides the necessary power to automatically or manually start, control i and protect one of the hydro units.

l 1

3.7-7 l - - -

. g An open or shcrt in any one battery, charger of DC distribution center, cannot cause loss of both hydro units.

The 230 kV sources, while expected to have excellent availability, are not under the direct control of the Oconee station and, based on past experience, cannot be assumed to be available at all times. However, the operation of the on-site hydro-station is under the direct control of the Oconee Station and

• requires no off-site. power to startup. Therefore, an on-site backup source of auxiliary powered through a common penetock by water taken from Lake Keowee.

The use of a common penstock is justified on the basis of past hydro plant experience of the Duke Power Company (since 1919) which indicates that the cumu-lative need to dewater the penstock can be expected to be limited to about one 1 day a year, principally for inspection, plus perhaps four days every tenth year.

Operation with one Keowee Hydro unit out of service for periods less than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is permitted. The operability of the remaining Keowee hydro unit is verified within one hour by starting the unit and energizing the standby buses through the underground feeder circuit. This action is repeated once every eight hours thereafter until the Keowee hydro unit is restored to service and will prc~'.de additional assurance of the operability of the re=aining unit.

Provisions have been established for those conditions in which long term pre-ventative maintenance of a Keowee hydro unit are necessary. The primary long term maintenance items are expected to be hydro turbine runner and discharge ring welding repairs which are estimated to be necessary every six to eight years. Also, generator thrust and guide bearing replacements will be necessary.

Other items which manifest as failures are expected to be extremely rare and could possibly be performed during the permitted maintenance periods. Time periods of up to 45 days f or each Keowee hydro unit are permitted every three

, mars. During these outages the remaining Keowee hydro unit will be verified to be operable within one hour and weekly thereaf ter by starting the unit and 4

energizing the underground feeder circuit. The remaining Keowee hydro unit

< will also be availabic through the overhead transmission path and will not be used for system peaking. Additionally, the standby buses will be energized continuously by one of the Lee gas turbines through the 100 kV transmission circuits.

-This transmission circuit would be electrically separated from the system grid and all of f-site non-saf ety-related loads. This arrangement provides a high degree of reliability for the emergency power systems.

Operation which both Keowee hydro units our of service is permitted for planned or unplanned outages for periods of 72 or 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> respectively. PJanned outages are necessary for the inspection of common underwater areas such as the penstock and to enable the removal of one Keowee unit from service. This would be a controlled evolution in which the availability and condition of the of f-site grid, startup transformers and weather would be evaluated and a Lee gas turbine would be placed in operation on the isolated 100 kV transmission line prior to commencement of the outage.

3.7-8

t A time period of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for unplanned outages of both Keowee units is s-table since c Lee gas turbine vill be started within one hour and will en the standby buses through the dediciated 100 kV transmission line. This af time is reasonable to determine and rectify the situation which caused i lost of both Keowee units.

Ir. the event that none of the sources of off-site power are available and.

is considered important to continue to maintain an Oconee reactor critica-return it to criticality from a hot shutdown condition, one of the Lee ga' 4 turbines can be made available as an additional baciap source of power, t assuring continued availability as an auxiliary power to perform an order shutdown of a unit should a problem develop requiring shutdown of both hy j units.

T 4

~4 3.7-9

4.6.12 Scairanually, th2 peak invirca voltags c psbility of cach cuctionssring

- diode in the 125 VDC Instrument and Control Power System shall be measured and recorded.

Bases The Keowee Hydro units, in addition to serving as the emergeacy power sources for the Oconee Nuclear Station, arc power generating sources for the Duke syste: requirements. As power generating units, chey are operated frequently, normally on a daily basis at loads equal to or grearer than required by Table 8.5 ci the FSAR for EST bus loads. Normal as well as emergency startup and operation of these units will be from the Oconee Unit 1 and 2 Control Room. The frequent starting and loading of these units to meet Duke system power requirements assures the continuous availability for emergency power for the Oconee auxiliaries and engineered safety features equipment. It will be verified that these units will carry the equipment of the maximum safeguards load within 25 seconds, including instrumnastion lag, af ter a simulated re-quire =ent for engineered safety features. To further assure the reliability of these units as emergency power sources, they will be, as specified, tested ,

for automatie start on a monthly basis from the Oconee control room. These '

tests will include verification that each unit can be synchronized to the 230 kV bus and that each unit can energize the 13.8 kV underground feeder.  ;

1 The interval specified for testing of transfer to emergency power sources is based on maintaining maximum availability of redundant power sources.

Starting a Lee Station gas turbine, separation of the 100 kV line free the remainder of the systec, and charging of the 4160 volt main feeder buses are specified to assure the continuity and operability of this equipment. The one hour time limit is considered the absolute maximum time licit that would be required to accomplish this.

REFERENCE FSAR Section 8 4.6-3