ML19322C377

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PNO-78-56:on 780320,excessive Cooldown at Rancho Seco Resulted in Reactor Coolant Pressure Decrease in Excess of Tech Specs.Caused by Reactor & Turbine Trips from Loss of Instrument Power Supply.Transient Analysis in Progress
ML19322C377
Person / Time
Site: Rancho Seco
Issue date: 03/21/1978
From: Nolan F, Sniezek J, Whitt K
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
To:
References
TASK-TF, TASK-TMR PNO-78-056, PNO-78-56, NUDOCS 8001160911
Download: ML19322C377 (1)


Text

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PRELIMINARY NOTIFICATION March 21, 1978 q

PRELIMIllARY T10TIFICATION OF EVENT OP. UNUSUAL OCCURRENCE--PNO-78-56 4

This oreliminary notification constitutes EARLY notice of an event of FOSSIBLE santv' or puMic i_nterest sianificance. ~The infonnatica presented is as initially received withcut varification or evalcation

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fnd is basicalTyTlT that is kno'.m by IE sta!? cn this Eate.

Facility:

SacrarJento Municipal Utility District M d SECO J

' Rancho Seco; Clay Station, CaliTornia

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t%IECH 90, l'T78

' Docket No. 50-312

Subject:

Primary System Pressure-Temperature g

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The licenses reported that loss of an instrugnt pmer supply _ caused reactor and turbine trips at 4:25 a.m. cn March 20 1978.,Excessivel

[cooldosnicaused reactor coolant pressure'to"decreas,e. E tiviting the safety ' injection system at 1600 psig.

Pressure re: ained above 11400.psig; o

throughout the event, but the technical specificatier.s for primary 9

systea cooldown rate and pressure-temperature cperating limits were exceedad.

The licensee is still reviewing the event with Babcock &

Wilccx (NSSS) assisting in analysis of the pressure-temperature trensient.

All engineered safeguards functioned as required, and nb safety limits 4

Vere GXC0eded.

j Two Region V inspectors were dispatched. to the site on $ arch 21 to review the event prior to startup.

Earliest expected restart is late March 21,1978, providing the results of the transient analyses are acceptable.

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Media interest is expected.

The licensee plans to issue a press release.

Region V does not intend to issue a press release.

Region V (San Francisco) received notification of this event by c

telephone from the Plant Superintendent at 2:30 p.m. on liarch 20, 1978.

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Contact:

KWhitt. IE x28180 FJNolan, IE x28019 JH5niezek, IE x28019 Distribution _:

Transmitted H St M O D Chairman Hendrie Coanissioner Bradford Commissior.er Kennedy S. J. Chilk, SECY C. C. Karmerer, CA Commissioner Gilinsky (For Distribution)

L Transmitted:

MNSS 2 M PBidgE0I E. Volgenau, IE L. V. Gossick, EDO E. G. Case E R Region

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S. H. Hanuuar, ECO

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J. J. Fcuchard, PA SS Bldg _

(MAIL.)

R. Hartfield, MIPC C. V. Smith,iP.55 T. J. McTiernan, OIA P,. G. Ryan, OSP R. Minogue, SD H. K. Shapar, ELD r' "

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.._ m.m _a A.-.h _ ;

MINARY NOTIFICATICN h PRE

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80011607 /[

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