ML20084U333

Final Deficiency Rept Re RCIC Turbine Ddn 143 Egm Speed Control & Governor.Initially Reported on 730606.New Resistor & Thyrector installed.Post-maint Surveillance Test Conducted W/Satisfactory Results

ML20084U333
Person / Time
Site:	Browns Ferry, Sequoyah, 05000000
Issue date:	07/30/1973
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Kruesi F US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U341	List: ML20084U333 ML20084U358
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8306280637
Download: ML20084U333 (5)

Text

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• TENNESSEE VALLEY HORITY CHATTANCOGA, TENNESSEE

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37401 E W July 30, 1973 4,vensany0 amu 05#rNE"n's"d5 Mr. F. E. Kruesi, Director Directorate of Regulatory Operations U.S. Atomic Energy Commission Washington, DC 20545

Dear Mr. Kruesi:

This is a final report of a deficiency in Browns Ferry Nuclear Plant unit 1 RCIC Turbine (DDN 143) EGM Speed Control and Governor. That deficiency was initially reported by M. M. Price to DRO Inspector W. S. Little on June 6, 1973, at the Browns Ferry site. On July 6,1973, we submitted an interim report on r,he deficiency. In accordance with paragraph 50.55(e) of 10 CFR 50, we submit the enclosed final report.

Very trulytyours,

. E. Gilleland Assistant to the Manager of Power Enclosure CC (Enclosure):

Mr. Norman C. Moseley, Director Directorate of Regulatory Operations U.S. Atomic Energy Cor: mission Region II - Suite S18 230 Peachtree .

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1 BROWNS FERRY HUCIFE PLINT U: FIT 1 FAILURE OF EGM SPEED CO:: TROL AND GOTSR:;0R FOR THE RCIC TUR3IUS An initial report of the failure of EGM speed control and governor for the RCIC turbine was made at the Brouns Ferry site by M. M.' Price to W. S. Little, AEC-DRO RcGion II Inspector, on June 6, 1973, in compliance with 10CFR50 55(c).

. On July 6,1973, we submitted an interim report on the failure. Tnic letter constitutes our final written report pursuant to 10CFR50 55(c).

On May 31,1973, an attempt was made to run the RCIC turbine surveillance test as part of the cold functional test program for Browns Ferry Nuclear Plant Unit 1. 'Ihe operator observed that no indication of turbine speed was being received in the main control room although the pump driven by the turbine was indicating it van delivering 550 cym. The turbine was tripped. An investigation revealed that the voltages from the electronic governor unit on the turbine were erratic. The governor unit was removed from the turbine and taken to the shop where a resistor was found to be burned out (i.e., open circuited). No evidence of any other problem was found at that the. General Electric site representatives were contacted; they stated that there were no other failures of this nature on record, and that apparently a simple electronic co=ponent failure had occurred.

Therefore, replacement resistors were ordered.

On June 19, 1973, the new resistors were obtained, and one was installed in the governor unit which was then reinstalled on the turbine. Tne system was released for retesting.

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On June 20, 1973, an electrical ground fault was reported on aso-volt Dc reactor MOV board 10. The ground fault vac determined to originate in the RCIC turbine electronic governor unit. Within the unit, the fault was determined to originate at a diode that 'was directly connected to the resistor which had failed earlier. The mica washer used to insulate the diode from the chassis was found to have deteriorated, thus grounding one side of the diode to the chassis.

On June 22, 1973, aft'er removing the cround fault, the systen was again released for rctesting; another test was attempted on the RCIC system.

Tne results were not acceptabic. Tne turbino speed control was erratic, and the speed indication was not accurate.

On June 23, 1973, the electronic governor unit was again removed from the turbine. A line-surce-protector Tnyrector was found to be shorted. A new 'ihyrector was ordered.

On July 16, 1973, the new Thyrcetor was received and installed. The ciectronic covernor unit was then checked out and calibrated. Following this, the system was again released for retecting.

On July 18, 1973, a postnaintenance surveilhnee test was conducted with satisfactory results. Tne test was conducted according to procedure S1I.5.F.3.

4 Following this successful test, the RCIC turbine was declared operable. s 1

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'ihe RCIC is not considered a safety system although it does have a safety-related function while the reactor pressure vessel is isohted. During 1

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vessel isolation, intermittent bloudown to the torus removes the energy while inventory is maintained by manual or automatic initiation of the i

RCIC system. Were the RCIC system to fail, the high-pressure core injection (HPCI) or automatic pressurisation system (ADS) safety systems would be actuated to protect the reactor and safely shut down the plant.

An investigation is continuing to determine if an initial sin 5le isolated failure initiated the chain of failures. Alternately, it is possible that a single maintenance or testing mistake initiated the chain of failures.

At the the of this report, it is not clear that it will be possible to determine the chain of events with certainty. However, if initiating events or causes can be established, those vill be rept ted to DRO.

As stated above, the RCIC system is not a safety system; however, its failure could result in a challenge to the HPCI or ADS system. _ It should be noted that failure of many normally available. systems result in similar challenges to safety systems.

As noted in the sequence of events, the corrective actions have been completed for all known equipment failures. Our investigation is coni;inuing to determine the root cause of the chain of failures. However, this

. deficiency is considered to have been corrected on July 18, 1973, after successful conpletion of the testing required by S14.5.F.3.

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' Die difficulties described above were discovered during the conduct of

!- standard WA-BFNP testing and maintenance procedures. At the present f

time there is no obvious reason to believe that the initiating event was other than simple component failure. However, if further investigation m.i.w, . ., . . - . . .-- --.+-.--e~ ~. ..-m_ha.., u, , , y.

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i described above indicates other.tise, a change in the QA Program vill be initiated and vill be reported to DRO along with the report on the result of the investigation as stated above.

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