ML20248H649

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PNO-78-092:on 780423,plant Was Shutdown Due to Spurious Signal in Power Range Protection Sys Which Caused Reactor/Turbine Trip.Nsss & Licensee in Process of Analyzing Event.Region I Will Review Result of Analysis
ML20248H649
Person / Time
Site: Three Mile Island Constellation icon.png
Issue date: 04/24/1978
From: Klingler G, Nolan F, Sniezek J
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-78-092, PNO-78-92, NUDOCS 9806080185
Download: ML20248H649 (1)


Text

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-o . 4, h f. eg-PRELIMINARY NOTIFICATION gg

-) April 24, 1978 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-78-92 This preliminary notification constitutes EARLY notice of an event of

_POSSIBLE safety or public interest significance. The information presented is as initially received without verification or evaluation and is basically all that is known by IE staff on this date.

Facility: Metropolitan Edison Company (DN 50-320)

Three Mile Island Nuclear Station, Unit No. 2 Middletown, Pennsylvania

Subject:

SPURIOUS REACTOR TRIP / INJECTION OF S0DIUM HYDR 0XIDE On April 23, 1978, the plant was shutdown from 30% power level. The shutdown was initiated by a spurious signal in the power range pro-tection system which caused a reactor / turbine trip.

Following the trip, operation of the main steam safety relief valves occurred as a result of the pressure transient. At least.one, safety relief valve failed to close, resulting in a cooldown of the reactor es coolant system at a rate that exceeded the technical specification.

Reactor pressure decreased to approximately 750 psi. Pressurizer level was lost for approximately one minute before the high head  ;

[- ,

safety injection pumps restored the level. Operation of the high j head safety injection pumps resulted in sodium hydroxide being  !

injected into the Reactor Coolant System (See PNO-78-68). The reac-tor core remained covered during the transient.

The NSSS (B&W) and the licensee are in the process of analyzing the event. Region I will review the result of the analysis with the licensee prior to the unit's return to operation.

Media interest is not expected. The Commonwealth of Pennsylvania has been informed. A press release is not planned by the licensee nor NRC.

NRC, Region I, (Philadelphia) received notification of this occurrence by telephone from the Unit Superintendent at 11:50 p.m. April 23, 1978.

GKlingler, IE x28019 FNolan, IE x28019 JSniezek, IE x28019

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Contact:

Distribution: Transmitted H St 1l L L

  • Chairman ~Hendrie Commissioner Bradford 0

b Commissioner Kennedy S. J. Chilk, SECY C. C. Kammerer, CA Commissioner Gilinsky (For Distribution)

Q Transmitted: MNBB u L Y P B1 dg 2, ', L (, E. Volgenau, IE g L. V. Gossick, EDO E. G. Case, NRR Region a 2 I Mf gd S. H. Hanauer EDO 4 7J.J.Fouchard,PA SS Bldg F > 2 (MAIL) g OggN.M.Haller,MPA C. V. Smith, NMSS T. J. McTiernan, CIA

@n.aR.G.Ryan,OSP )l R. Minogue, SD H. K. Shapar, ELD PRELIMINARY NOTIFICATION 4g

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