ML19329B278

LER 77-110/03L-0:on 771211,control Loss Occurred to Both Auxiliary Feed Pumps During Reactor Turbine Trip Test.Caused by Independent Component Failures.Auxiliary Feed Pumps Modified & Control Relays Replaced

ML19329B278
Person / Time
Site:	Davis Besse
Issue date:	01/03/1978
From:	Beyer B TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19329B276	List: ML19329B275 ML19329B278
References
LER-77-110-03L, LER-77-110-3L, NUDOCS 8002040666
Download: ML19329B278 (3)

Text

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,a i4; l Test, control of both AFP Turbines was lost.

Io isl l speed stop while AFPT l-2 would not increase above the low speed stop. The unit was ;

l o is I l in Mode 3, " Hot Standby" which satisfied Limiting Condition for Operation 3.0.3 which [

There was no danger to  ;

l 0 l 7 l l requires the station to be in Hot Standby within one hour.

the health and safety of the public or to unit personnel. (NP-33-77-110) l

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OCCURRENCE REPORT REVISION SEQUENTIAL REPORT No. CODE TYPE No.

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i, ;i , g 1-1 control was lost due to turbine governor mechanical binding. AFFT l--2 control I i

,,,,,g power was lost due to blown control power supply fuses caused possibly by sticking t

,, ,,,l relays.

Both Auxiliary Feed Pump Governors were modified by adding an oilite bush- j

,,,4; l ing and both control relays were replaced on AFPT l-2.  ;

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TOLEDO EDISON COMPANY DAVIS-BESSE UNIT CNE :.TCLEAR POWER STATION y- SUPPLD'E' ITAL INFORMATION FOR LER NP-33-77-110 1 DATE OF EVENT: December 11, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of control to both Auxiliary Feed Pumps during Reactor / Turbine Trip Test Conditions Prior to Occurrence: The unit was in Mode 3, " Hot Standby", with Power (MWT) = 0 and Load (MWE) = 0.

Description of Occurrence: At 0710 hours0.00822 days <br />0.197 hours <br />0.00117 weeks <br />2.70155e-4 months <br /> on December 11, 1977, the reactor was tripped for the 40% " Reactor / Turbine Trip Test", TP 800.14. During the trip recovery, both Steam Generators secondary side water level, decreased below the level trip set-point of the Steam and Feedwater Rupture Control System (SFRCS). This automatically started both Auxiliary Feed Pumps.

Auxiliary Feed Pump 1-1 started properly and supplied feedwater but control was lost when the governor would not vary from the high speed stop. Auxiliary Feed Pump 1-2

'~ hstarted but later failed at the minimum speed, also indicating a loss of control.

g ,f This placed the unit in excess of the Action Statement of Technical Specification 3.7.1.2 which requires two independent Auxiliary Feed Pumps in Modes 1, 2 and 3.

The unit was in Mode 3, " Hot Standby" which satisfied Limiting Condition for Opera-tion 3.0.3 which requires the unit to be in Hot Standby within one hour and Cold Shutdown within the following thirty hours if the corrective action is not completed.

Designation of Apparent Cause of Occurrence: On Auxiliary Feed Pu=p Turbine (AFPT) 1-1, the governor (Woodward Type PG-PL) speed setting shaft was binding where it enters the governor housing, and at the governor receiver bracket (the bearing sur-face). Also, the speed changer drive clutch was slipping which resulted in the governor not responding to the speed change signal. The cause of the binding was an improper initial installation of the roll pin (high speed stop pin) which allowed a bearing washer to stick.

On AFPT l-2, the control power fuses which also provide power for the governor speed changer motor were blown preventing the governor from responding to control signals.

The control power fuses were possibly blown by a momentary sticking of a relay in the speed control circuit. l Analysis of Occurrence: There was no danger to the health and safety of the public l or to unit personnel. ihe reactor was previously tripped and the unit was in Mode No steam line or feedwater rupture  !

3, " Hot Standby" at the cine of the occurrence.

r ~ occurred. l x_ /

3 s TOLEDO EDISON COMPANY

\ DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE .

PACE 2' dSUPPLEMENTAL INFORMATION FCR LER NP-33-77-110 Corrective Action: On AFPT l-1, the roll pin which caused the washer to bind was correctly positioned; the governor speed setting shaft bearing area was cleaned and lubricated; and the speed changer drive clutch tension was adjusted to pro-

] vide more torque before slipping.

On AFPT l-2, the blown fuses were replaced. The roll pin was inspected and found properly positioned. Both the relays were replaced in the speed control circuit to correct for the possible momentary sticking.

A modification was made (Facility Change kequest 77-301) on-born governors install-ing an oilite bushing for the speed setting shaft bearing surface in the governor housing to eliminate the binding experienced on AFFT l-1.

I After repairs, the governors for both turbines were tested through ten cycles (high speed to low speed). Auxiliary Feed Pump 1-2 was declared operable at 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> on December 11, and Auxiliary Feed Pump 1-1 was declared operable at 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> on December 11, removing the unir from the Action " Statement of Technical Specification 3.0.3 and 3.7.1.2, respectively.

Surveillance Testing frequency has been increased to weekly pending outcome of

. engineering evaluation being made to increase reliability of AFPTs. Additionally, the method of Surveillance Testing has been modified-to allow additional exercis-

, ing of the governor.

Failure Data: Blown fuses have occurred in the AFPT governor speed changer circuits before because of relay failures (see Licensee Event Report NP-33-77-51 and NP-33-77-52). There has been no binding of the AFPT governor shafts previ*ously.

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