ML20236V301

PN-75-082:on 750830,reactor Tripped Due to Low Primary Coolant Flow,When D Loop Flow Dropped Suddenly from 100% to 40%

ML20236V301
Person / Time
Site:	Zion File:ZionSolutions icon.png
Issue date:	09/02/1975
From:	Jennifer Davis, Thornburg H, Warnick R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
To:
References
PN-75-082, PN-75-82, NUDOCS 9808030066
Download: ML20236V301 (1)

Text

f L f O,) Ja a C=h ODP PRELIMINARY NOTIFICATION - NOT FOR PUBLIC DISCLOSURE September 2, 1975

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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE --PN-75-82 /

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, This preliminary notification constitutes EARLY notice of events of if ,0f 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 OIE staff as of 9:00 a.m. on the date of this notification. IT SHOULD BE SPECIFICALLY NOTED THAT THIS NOTIFICATION MAY CONTAIN INFORMATION THAT LATER MAY BE DETERMINED TO BE INACCURATE OR INCONSISTENT. AN OFFICE OF INSPECTION AND ENFORCEMENT

. . NOTIFICATION OF AN INCIDENT OR OCCURRENCE (BLUE SHEET) SUBSEQUENTLY WILL BE ISSUED IF WARRANTED.

Facility: Commonwealth Edison Company (Zion Unit 2)

Subject:

Sudden Decrease in Reactor Coolant Flow At 0648 hrs on 8/30/75 the reactor tripped due to low primary coolant flow, when the "D" loop flow dropped suddenly from 100 percent to 40 percent. Based upon preliminary evaluations the licensee believes that there may have been a failure in the cold leg main loop isolation valve, (i.e., one or both discs of the split-discs valve may have dropped down into the flow path).

• The licensee plans at this time to, attempt a radiograph of the valve to

, - determine its internal condition before proceeding with any repair work.

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l During cooldown an automatic safety injection resulted at 0029 hrs on 8/31/75 when the pressure differences between the "D" loop and the other  ;

loops exceed 100 psid.

The licensee is planning to make a press release. IE:III is preparing a press release. The State of Illinois will be notified.

Region III received notification of this occurrence by telephone from Commonwealth Edison at 1008 hrs, 8/31/75. j

Contact:

RFWarnick, IE x7261 HDThornburg, IE x7353 JGDavis, IE x7541 Distribution:

Chairman Anders . Commissioner Mason S. J. Chilk, SECY Commissioner Gilinsky Commissioner Rowden G. F. Murphy, JCAE l Commissioner Kennedy C. C. Kammerer, CA l r" **

L. V. Gossick, EDO D. F. Knuth, IE J. A. Harris, PA B. C. Rusche, NRR H. H. Brown, ISP T. J. McTiernan, AIA K. R. Chapman, NMSS H. K. Shapar, ELD l

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10 PRELIMINARY NOTIFICATION NOT FOR PUBLIC DISCLOSURE 9808030066 750902 PDR I&E PN-75-082 PDR

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