ML17266A227

LER 80-025/09X-1:on 800512,during Planned Secondary Plant Shutdown for Turbine Maint,Main Steam Header Would Not Depressurize Following Steam Stop Closure.Cause Unknown. Valve Stems Were Replaced & Verified Operable

ML17266A227
Person / Time
Site:	Saint Lucie
Issue date:	07/07/1980
From:	Schoppman M FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML17208A814	List: ML17208A813 ML17266A227
References
LER-80-025-09X, LER-80-25-9X, NUDOCS 8007150536
Download: ML17266A227 (4)

Text

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~oz Dur in a 1 armed secondar lant shutdown for turbine maintenance it was

~Q3 noted that the main steam header woul d not'e ress uri ze fol 1 owi n steam

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~QS stems were sheared with the valves stuck in the "o en" osition. Althou h

~ots onl three inch warm-u lines were involved the olant did not meet the intent of T.S. 3.7.1.5 and the FSAR anal sis. I;Ihen

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0jg ~h detertttitted. The valve o erators appear to b v- i ~ fr I-l 0 I I 3 0 5 I .I':

and the valves were verified to be o erable rior to startin up the unit.

A follow-uo reoort will be issued.

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Event Descri tion and'robable Conse uences The NSIV bypass valves are not specifically mentioned in the Technical Spec-ifications or FSAR analysis. However, their failure in the open position provides a path for continued blowdown of the steam generators on main steam rupture downstream of the HSIV. Rupture upstream of a HSIV would not be affected because .of a check valve in series with the bypass valve.

Cause Oescri tion and Corrective Action

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As a,result of the continuing engineering review of the cause of the sheared valve stems, this occurrence has been determined to be reportable in accordance with 10 CFR 21; The safety analysis for main steam line breaks, both inside and outside con-tainment, assumes isolation of each main steam line afte. NSIS. The loss of capability to isolate those lines is .an unanalysed event which allows an un-

=controlled blowdown of both steam generators and could thus constitute a

'substantial safety hazard" in relation to 10 CFR 21. ln addition, it also be noted that from a radiological standpoint, this occurrence represents must a potential substantial safety hazard. The tube rupture accident assumes isolation'f the. faulted steam generator., The'imiting condition of operation .

(LCO) for RCS specific activity (T.S.3.4.8) 'is. based on the analysis. of the tube rupture accident. Failure to isolate the'faulted steam generator could .,

substantially increase offsite exposures.

'he valves in question are Schutte and Koerting Co., motor operated bypass valves,(3 inch, 600 lb.) with a Limitorque Operator. The FPL Engineering Department is continuing the evaluation of the occurrence. Permanent corrective action will be reported.

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