ML20084H843

AO BFAO-7423W:on 740413,HPCI Failed to Reach Rated Flow in Required Time During Performance of post-maint Testing at Rated Pressure.Caused by Defective 10,000-ohm Coverter Zero Potentiometer in Combined Ramp Generator & Signal Converter

ML20084H843
Person / Time
Site:	Browns Ferry
Issue date:	04/23/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084H846	List: ML20084H843 ML20084H852
References
AO-BFAO-7423W, NUDOCS 8305060021
Download: ML20084H843 (3)

Text

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, (Vl i TENNESSEE VALLEY AUTHOAITY Mr\ ! f7 CHAT TANCOGA, TENNESSEE i /

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r' Mr. John F. O' Leary, Director l; t' jff i

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. Office of Regulation t.f 83.nre c e U.S. Atomic Energy Co::nission  % 'p km[se]:d,! J4 Washington, DC 20545

Dear IIr. O' Leary:

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TEIIITESSEE VALLEY AUTEORITY - BRO?T.!S FERRY ITUCLEAR PLAIIT UITIT 1 -

DOCI3T I!O. 50-259 - FACILITY OPERATI1!G LICEIISE DPR ABliORMAL OCCURRCICE REPORT EFAO-7423W The enclosed report is to provide details concerning HPCI failure to reach rated flov in the required time. This event occurred on -

Browns Ferry I!uclear Plant unit 1 on April 13, 1974, and is subnitted in accordence uith Appendix A to Regulatory Guide 1.16, Revision 1, October 1973.

Very truly yours, TEli1IESSEE VALLEY AUTHORITY

.w irector of Power Production Enclos,ure CC (Enclosure):

Mr. I!ornan C. Moseley, Director Region II Regulatory Operations Office, USAEC 230 Peachtree Street,17.1. , Suite 816 Atlanta, Georgia 30303 l

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ABI!OR'*AL OCCURICI CE REPORT Report No.: BFAO-7423W Report Date: April 23, 1974 Occurrence Date: April 13, 1974 Facility: Browns Ferr/ Uuclear Plant unit 1 Identification of Occurrence EPCI failure to reach rated flow in required time.

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Conditions Prior to Occurrence The reactor was at rated te=perature and pressure at approximately 10-percent thermal power.

Descrintion of Occurrence HPCI maintenance had been perfor=ed while the reactor was in a shutdown condition follouing a special =aintencnce instruction approved on April 6,1974. This instruction required post-raintenance testing using auxiliar/ stec= before nuclear hectup and testing using reactor steam at 150 psig and at rated reactor pressure.

During the perfor=ence of this post-naintenance testing at rated pressure, HPCI failed to reach rated flow in 25 seconds. It did reach rated flow in 27.5 seconds.

Desirmation of Apperent Ceuse of Occurrence Investigation showed that the re=p signal was taking 22 seconds to reach its maximum output signal as compared to the normal 10 seconds and that there was no ,

output from the EM control box to the governor actuator. The 10,CCO-ohm converter zero potentioneter in the combined rc=p generator and signal converter was defective. The output transistors in the EGM were also defective.

Anclysis of Occurrence The EPCI had previously =et all requirements when tested with nuniliary steca before startup and uhen tested with reactor steam at the 150 psig level. Safe shutdown of the reactor would have been possible because the remaining core cooling syste=s were operable.

Corrective Action Both the combined ramp generator end signal converter and EGM control box were replaced. Surveillence testing was performed with satisfactory results. Rep.cirs

' have been co=pleted on the defective EGM control box and calibration verified.

It is possible that the transistor failure occurred following this test when a brush recorder uns connected to the output of the EGM to monitor EGM and rc=p signal converter output voltage. We have since deter =ined that the channel of s2

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Correctivef.ction(continued) the bruch recorder used to =cacure EGM output was bad. The bruch recorder uns not used during the surveillance test follettinC completion of the above work.

Instructions vill be written to provide proper procedure and precautions to be taken before connecting a bruch recorder.

Failuro Data The EGM control box is Woodward part No. 8270-811. The defective transistors are as follows: ,,

1. Q9: 2n696

2. Q,10: 2Hil31 We do not feel that this failure relates to urevious failures renorted in

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BFAO-747W cnd -7hl6W on EPCI cnd 3FAO-7416W 'on RCIC. Both HPCI and RCIC EGM control boxes are similar.

The combined re;rp generator and signal converter is Woodward part No. 8270-957.

The potentioneter is es follous: '

l. Tri:: pot Potentioneter, Bourns, 3255L-1,10X, sub=iniature, virewound elenent i

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