ML20212K460

Special Rept:On 870106,PORV 1RY455A Lifted for 2 S.Caused by Rapid Increase of RCS Temp When Reactor Cooling Pump 1C Started.Opening PORV Terminated Pressure Transient.On 870112,bubble Formed in Pressurizer to Prevent Recurrence

ML20212K460
Person / Time
Site:	Braidwood
Issue date:	02/03/1987
From:	Hunsader S COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
2681K, NUDOCS 8703090321
Download: ML20212K460 (2)

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'N Colnfnonwealth Edloon

' One First National Plaza. Chicago, Illinois 4g T \ / Address Reply to: Post Omco Box 767

'v/ Chicago. Illinois 60690 0767 February 3, 1987 PR10R!iY liOUTING E ett 1 See ad k3 l a,w" -

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Mr. James G. Keppler f;p g9gr s m

Regional Administrator L us"L U.S. Nuclear Regulatory Commission Region III M [

tra 799 Roosevelt Road Fit. N L9 %

Glen Ellyn, IL. 60137

Subject:

Braidwood Station Unit 1 Thirty Day Special Report Mitigation of Reactor Coolant System Pressure Transient Using the Power Operated Relief Valves NRC Docket No. 50-456

Reference:

(a) NUREG-1223, Technical Specification, dated October, 1986

Dear Mr. Keppler:

Reference (a) Section 3.4.9.3, Action C requires Commonwealth Edison to submit a Special Report, pursuant to Specification 6.9.2, within thirty (30) days in the event the power-operated relief valves (PORVs), or the residual heat removal (RilH) suction relief valves, or the reactor coolant system (RCS) vent (s) are used to mitigate an RCS pressure transient. Attachment A provides the details of the circumstances surrounding the actuation of a PORV on January 6, 1987. In accordance with Reference (a) Section 6.9.1.8 this event will also be reported in Braidwood's next Monthly Operating Report.

Please direct any questions concerning this matter to this office.

Very truly yours,

)( W - L S. C. Ilunsader Nuclear Licensing Administrator

/klj cc: Braidwood Resident Inspector 2681K t I 8703090321 870203 I gDR ADOCK 050 46 Qgg FEB 11 W

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a AITACHMENT A On January 6,1987, at 0023 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />, the Unit 1 Reactor Coolant System (RCS) was water solid at 380 psig and 125*F with-all four Reactor Coolant Pumps (RCP) stopped. The Residual Heat Removal (RHR) Train la was running in the shutdown cooling mode. The 1C RCP was started. Approximately 46 seconds after start, the IRY455A Power Operated Relief Valve (PORV) lif ted for two seconds. Both PORV's were in the cold overpressure protection mode, in which PORV i 1RY455A has a setpoint of 470 psig at 125'F. The maximum RCS pressure reached during this pressure transient was approximately 480 psig. It is suspected that during this transient the IB RER Suction Relief Valve also lifted since its setpoint pressure is 450 psig.

This pressure transient was induced by a rapid increase of RCS temperature when the 1C RC? was started and the 125'F RCS water was swept through the steam generator tubes with the secondary coolant temperature at approximately 150*F. The letdown pressure control valve, ICV 131,was being controlled in manual the time the RCP was started in anticipation of a pressure transient with solid plant conditions. Tha val"e could not open quickly enough to mitigate the resulting pressure transient. The opening of tl.1 PORV terminated the pressure transient.

On January 12, 1987, at approtimately 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> a steam bubble was formed in the pressurizer. This steam bubble supplies a surge volume to the F.CS which can absorb pressure transients due to RCS water temperature increase. Also, a RCP has been running continuously since the incident occurred to maintain RCS temperature equal to secondary steam generator temperature. These actions will prevent recurrence of this event.

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