ML19276E680

Deficiency Rept on 780620,0815 & 1016:potential Exists to Render Diesel Generator 1C & 1-2A Inoperable If Loss of Offsite Power or LOCA Occurs.Failure Could Leave Entire Plant W/No River Water Pumps Available

ML19276E680
Person / Time
Site:	Farley
Issue date:	11/17/1978
From:	ALABAMA POWER CO.
To:
Shared Package
ML19276E678	List: ML19276E677 ML19276E680
References
NUDOCS 7903200245
Download: ML19276E680 (8)

Text

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JOSEPH M. FARLEY NUCLEAR PLANT-UNIT 2 ALABAMA POWER COMPANY REPORT OF 10CFR50.55(e) DEFICIENCY A design condition has been detected which can render Diesel Generator lC and 1-2A inoperable when both Farley units are in operation and loss-of-offsite power (LOSP) on both units or LOSP on both units and LOCA on one unit occur.

Presently, as shown in , Figure 1, Diesel Generator 1C has its auxiliaries powered from emergency Motor Control Center (MCC) IN. MCC IN gets its power supply from emergency 600V Load Center 1R. The 600V Load Center 1R is a shared load center capable of being energized from either unit. When it is energized from Unit 1 it is supplied from the 4KV Bus lH through Station Service Transformer 1R. When it is energized from Unit 2 it is supplied from the Unit 2 4 KV Cus 2H through Station Service Transformer 2R. The two 600V incoming breakers of 600V Load Center 1R are key interlocked so that only one can be closed at any time. The alignment of Load Center 1R to Unit 1 er Unit 2 can be performed manually only, from the local control panel located in the diesel building.

As shown in Figure 1, Diesel Generator 1-2A has its auxiliaries powered from emergency MCC 1S. MCC 15 is a shared MCC capable of being energized from either unit. When it is energized from Unit 1 it is supplied from the Unit 1600V Load Center 10, which in turn is powered from Unit 14KV Bus IF through Station Service Trans former ID. When it is energized frcm Unit 2 it is supplied from the Unit 2 600V Load Center 2D, which in turn is powered from Unit 2 4 KV Bus 2F thrcugh Station Service Transformer 2D. The alignment of MCC 15 to Unit 1 or Unit 2 can be performed manually only from the MCC 1S located in the diesel building.

Under LOSP on both units or LOSP on both units and LOCA on Unit 1, Diesel IC is a source of power for Unit 2 Train A hot shutdown loads, while Diesel 1-2A is a source of power for Unit 1 LOCA loads. If, at the accident occurrence, 600V Load Center 1R is aligned te Unit 1, it will be deenergized since 4 KV Bus lH is deenergized, and Diesel Generator 1C loses its auxiliaries. At this time, MCC IN 7 903 2 0 0 g2e/di

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has a be connected to Station Service Transformer 2R by the manual operation of the key interlocked incoming breakers of 600V Load Center 1R. Diesel genera tor manu-facturer has specified that diesel genera tor can run without its auxiliaries for one minute if the engine is at operating tempera ture, or for three minutes from cold start. If the manual changeover of power source to llCC 1R cannot be accomplished in the specified time, Diesel b nerator 1C could be automatically tripped bec.use of low lube oil pressure, or damaged beca':se of loss of cooling water. The high cooling water temperature is alarmed, but does not trip the diesel generator auto-mati ally under accident conditions.

If Diesel Generator IC is disabled, no source of power for Unit 2 Train A safeguard loads will be availchle, and a single failure on Unit 2 Train B can render Unit 2 incapable of being shutdown. (4 KV Bus lH is deenergized under the postulated conditions since the tie breaker between 4 KV Bus IF and 4 KV Bus lH is open.)

If, under the above conditions f4CC 1S is aligned to Unit 2, it will be deenergized and Diesel Generator 1-2A loses its auxiliaries. If Diesel Generator 1-2A is disabled, no source of power for Unit 1 Train A LOCA loads will be available.

In this case, if we apply the single failure criterion to Unit 1 Train B instead of Unit 2 Train B, Unit 2 will meet the hot shutdown requirements, while Unit I cannot neet the LOCA requirements.

Under LOSP on both units and LOCA on Unit 2, Diesel Generator 1C is the source of power for Unit 1 Train A hot shutdown loads, while Diesel Generator 1-2A is the source of power for Unit 2 LOCA loads. If, at the accident occurrence 600V Load Center 1R is aligned to Unit 2, it will be deenergized since 4 KV Bus 2H is deenergized, and Diesel Generator 1C loses its auxiliaries. Diesel Generator 1C will be disabled, no source of power for Unit 1 Train A safeguard loads will be '

available, and a single failure on Unit 1 Train B can render Unit 1 incapable of being .

shutdown. (4 KV Bus 2H is deenergized under the postulated conditions since the tie breaker between 4KV Bus 2F and 4 KV Bus 2H is open.)

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If, under the above conditions fiCC 15 is aligned to Unit 1, it will be deenergized, Diesel Generator 1-2A disabled, and no source of power for Unit 2 Train A LOCA loads will be available. In this case, if we hpply the single failure criterion to linit 2 Train B instead of Unit 1 Train B, Unit 1 will meet the hot shutdown requirements, while Unit 2 cannot meet the LOCA requirements.

Thus, under the criteria of 10CFRCO.55(e) the referenced problem constitutes a significant deficiency. Note that the referenced problem is only a safety pro-blem when Unit I and Unit 2 are operated simultaneously.

A second problem identified concerning the diesel generator relates to the following. The Farley Nuclear Plant is intended to'be designed to accommodate the Loss of Pond Dam along with Loss-of-Offsite Power and a single failure. Under this event, the river water systems will be automatically diverted to the wet pit which supplies suction to service water pumps.

For this event, for Unit 1 operation alone, a minimum of 2 river water pumps will be required. Therefore, to accommodate single failure, 4 river water pumps

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are powered from the diesel generator system.

For Unit 1 and Unit 2 operation, a minimum of 4 river water pumps are required ar,d to accommodate single failure, 8 river water pumps are to be sequenced onto the diesel generator system.

With Unit 1 in operation alone two (2) emergency power sources (diesel generator 1C-Train A and diesel generator 2C-Train B) are dedicated to the River Ma ter Sys tem. Four river water pumps with automatic starting capability are

'available so that in the event of single failure at least 2 river water pumps will Therefore, start, meeting the minimum requirements for safe shutdown of the unit.

k there is no deficiency for Unit 1 operation.

t t However, af ter two units go into operation, only one emergency power source (diesel generator 2C-Train B) is dedicated to the River Water System, hence only

i -c-4 river water pumps with automatic capability would be available. The failure of diesel generator 2C could leave the entire plant with no river water pumps available. This deviates from our commitment in the FSAR and does not ccet the minimum River Water System availability requirements for safe shutdown of both Uni ts . R'edesign to provide a minitrum of four river water pumps on Loss of Offsi te Power is undentay.

To correct the first problem the following corrective action will be taken (refer to Figure 2):

(1) The key interlock feature of breakers ER02 and ER05 on Load Center IP. will be removed and replaced by an electrical interlock, so that only one of the two breakers could be closed at any time.

The electrical circuitry of these breakers 1.ill be changed to accomplish the following: (a) automatically connect Locd Center 1R to Bus IH (ER02 closed and ER05 open) when Diesel Gnerator 1C is aligned to Unit 1 (DH07 on Bus lH closed); (b) automatically connect Load Center 1R to Bus 2H (ER05 closed and ER02 open) when Diesel Generator 1C is aligned to Unit 2 (DH07 on Bus 2H closed).

(2) !!anual transfer switch on f:CC 1S will be removed and the incoming feeders from Load Centers ID and 2D will be solidly connected to the !!CC.

. Breakers EDl3 on Load Center ID and ED13 on Load Center 20 will be electricaily interlocked, so that only one of the two breakers could be closed at any time. The electrical circuitry of these breakers will be changed to accomplish the following: (a) automatically connect fiCC IS to Load Center 10 (E013 on Load Center ID closed and EDl3 on Load Center 2D open) when Diesel Generator 1-2A is alignet to Unit 1 (DF08 on Bus IF closed), (b) automatically connect f4CC IS to Load Center 2D (E013 on Load Center 20 closed and EDl3 on Load Center 10 open) when Diesel Generator 1-2A is aligned to Uni t 2 (DF08 on Bus 2F closed).

In order to correct the second problem, the following changes to the logic, schematic, and wiring concerning the diesel generator are proposed (see figures 1, 2 and 3):

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(1) Af ter the sequencer has added the LOSP loads to Bus IF, the 4 KV Bus IF will furnish power to the 4 KV Bus 1H. Three Unit 1 Train A river water pumps (Numbers 8, 9, and 10) will be started on Bus lH in sequence.

(2) The LOSP sequencer on Bus 2F will be modified to eliminate containment cooler 2B from being added automatically. As in the pas t, containment cooler 2A will be automatically applied to Bus 2F. Af ter LOSP sequencer has added LOSP loads to Bus 2F, the river water pumps sequencer on Bus 2H will be unblocked to enable one river water pump (Number 6) to automatically be applied to Bus 2H.

(3) Should diesel generator 2C fail, diesel generator 1B will furnish power to Bus lJ and diesel generator 2B will furnish power to Bus 2J after the sequencers on Buses 1G and 2G have had LOSP loads added. Two river water pumps (Numbers 4 and 5) will start on Bus lJ and two river water pumps (Numbers 1 and 2) will start on Bus 2J.

(4) The existing feature of the diesel generator 2C working like a backup for diesel generator 18 or 2B if ei ther fails to furnish power to the hot shutdown load will be removed. This feature is not required to meet single failure criteria.

In the design event discussed, the river water system will be automatically diverted to the pond wet pit which supplies suction to the service water pumps.

Additional stop logs will be addert to the pond wet pit to ensure that adequate wet pit level is maintained.

The above changes will ensure that the plant has adequate river water supply with both units operating. Both problems will be corrected prior to the issuance of the Unit 2 Operating License.

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