DCL-84-306, Special Rept 84-10:on 840728,addition of Cool Feedwater to Steam Generators Resulted in Decrease in Reactor Coolant Temp to Low Setpoint.At Same Time,Hi Steam Flow Bistables Tripped for Surveillance Testing

Special Rept 84-10:on 840728,addition of Cool Feedwater to Steam Generators Resulted in Decrease in Reactor Coolant Temp to Low Setpoint.At Same Time,Hi Steam Flow Bistables Tripped for Surveillance Testing

ML20098B822
Person / Time
Site:	Diablo Canyon
Issue date:	09/19/1984
From:	Shiffer J PACIFIC GAS & ELECTRIC CO.
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
CON-#484-116 DCL-84-306, OL, SR-84-10, NUDOCS 8409260300
Download: ML20098B822 (1)

Text

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PACIFIC GAS AND ELECTR,IC C O M PANY FOt*d3 l 77 BEALE STREET

• SAN FRANCISCO, CALIFORNI A 94106- (415) 781-4211 TWX 910-372-6587 JAMES D SHIFFER September 19, 1984

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PGandE Letter No.: DCL-84-306 Mr. John B. Martin, Regional Administrator U. S. Nuclear Regulatory Comission, Region V 1450 Maria Lane, Suite 210 Walnut Creek, CA 94596-5368 Re: Docket No. 50-275, OL-DPR-76 Diablo Canyon Unit 1 Special Report on ECCS Actuation, SR 84-10

Dear Mr. Martin:

Pursuant to Section 6.9.2 of Appendix A of the Diablo Canyon Unit 1 Operating License, and as specifically required by Technical Specification 3.5.2, this Special Report is submitted concerning an actuation of the ECCS which resulted in the discharge of water into the Reactor Coolant System. This occurrence was described in LER 84-022-00, dated August 27,1984 (DCL-84-292).

On July 28,1984, at 0709 PDT with the reactor in Mode 3 (Hot Standby), plant personnel were adding water to the steam generators in preparation for using steam to roll the main turbine. The addition of cool feedwater to the steam generators resulted in a decrease in reactor coolant temperature to the low setpoint. At the same time, the Hi Steam Flow Bistables were tripped for surveillance testing. The resulting combination of signals (Low-Low Tavg and Hi Steam Flow) caused a reactor trip signal and safety injection. All safety systems responded normally. This is the third ECCS actuation cycle to date. -

These conditions have in no way affected the public's health and safety.

Sincerely, V

cc: G. W. Knighton /-

Director, Office of Management Information and Program Control Service List

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