ML20137H356

Special Rept 1-SR-86-002:on 860109,unusual Event Declared When Reactor Trip Generated by Core Protection Calculators from Flow Projected DNBR While Turbine Trip Initiated as Scheduled Part of Power Ascension Testing Program

ML20137H356
Person / Time
Site:	Palo Verde
Issue date:	01/11/1986
From:	Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
1-SR-86-002, 1-SR-86-2, ANPP-34512-EEVB, NUDOCS 8601210497
Download: ML20137H356 (3)

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Arizona Nuclear Power Project P.o. box 52034

• PHOENIX, ARIZONA 85072-2034 January 11, 1986 ANPP-34512-EEVB/BJA-98.07 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit 1 Docket No. STN-50-528, (License No. NPF-41)

Report of Notification of Unusual Event - Reactor Trip File: 86-020-404; G.1.01.j0

Dear Sirs:

Attached please find a report describing a Notification of Unusual Event at Unit 1 of the Palo Verde Nuclear Generating Station on January 9, 1986. Thi- report addresses a reactor trip during testing due to a loss of power to the reactor coolant pt.mps.

This report is prepared and submitted pursuant to Table 5.3-1 of the PVNGS Emergency Plan. By copy of this letter, we are also forwarding a copy of the report to the Regional Administrator of the NRC Region V office and other offsite authorities.

If you have any questions or concerns, please contact Mr. W. F. Quinn of my staff.

Very truly yours, m4L/f/

E. E. Van Brunt Jr.

Executive Vice President Project Director EEVB/BJA/wa Attachment cc: J. B. Martin R. P. Zimmerman R. F. Fish, Jr.

E. A. Licitra R. A. Colson, ADES C. E. Tedford, AARA R. E. Bluhm, MCDCD & ES R. G. Godbehere, MCSO R. T. Milstead, DPS INPO Records Center 8601210497 8601ft1 h

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.. Attachmen", to

+ ANPP-34512 PALO VERDE NUCLEAR GENERATING STATION UNIT 1 NOTIFICATION OF UNUSUAL EVENT OF JANUARY 9, 1986 Docket No. 50-528 License No. NPF-41 Special Report No.1-SR-86-002 At 1403 MST on January 9, 1986, the NRC Operations Center was notified, via the Emergency Notification System, of the declaration of a NOTIFICATION OF UNUSUAL EVENT for Unit 1 of the Palo Verde Nuclear Generating Station. The NOTIFICATION OF UNUSUAL EVENT was declared pursuant to Emergency Plan Implementing Procedure-02 , which requires the reporting of a reactor trip which is complicated by concurrent or subsequent events or conditions.

At approximately 1325, the plant was in Mode 1 at 100% reactor power, with a pressure of 2250 psi and a cold leg temocrature of 565 degrees F, when a turbine trip was initiated as a scheduled part of the power ascension testing program.

The test was initiated by simulating a fault on the main generator. This type of fault will open the output breakers and cause the non-essential house loads to be automatically " fast transferred" to offsite power sources. The Reactor Power Cutback System was intentionally left out of service as part of the test.

The test was initiated by actuating the Unit Differential Generator Protection Relay. As expected, the 525V generator ' output breakers opened. House loads (including the RCPs and circulating water pumps) did not " fast transfer" to the off-site power source. A reactor trip was generated by the Core Protection Calculators (CPC) from flow projected Departure from Nucleate Boiling Ratio. The Reactor Coolant Pump speed was decreasing at the time of the first CPC channel trip. After the reactor coolant pumps coasted down, core cooling occurred via natural circulation.

The steam bypass control valves received a Quick Open signal, but reclored almost immediately due to the loss of power. Steam generator pressure increased rapidly until one Main Steam Safety Valve (MSSV) lifted, remaining open for approximately 43 seconds before reseating. As the MSSV reseated, five Steam Bypass Control System (SBCS) valves modulated open. The SBCS valves reained open for approximately 45 seconds with a subsequent period of oscillation (3 open-close cycles) over about 40 seconds.

The operator took manual control of the individual SBCS valves in order to stop the secondary system induced cooldown event. At approximately the same time, a Main Steam Isolation Signal (MSIS) occurred due to low Steam Generator Pressure. The MSIS terminated the cooldown with the reactor coolant system cold leg temperature reaching 540F.

Agtachment to

. 'ANPP-34512 (Continuation of Special Report 1-SR-86-002)

The reactor coolant system temperature and pressure recovered (due to decay heat) and the operator re-established a cooldown via use of a steam generator, 2 atmospheric dump valves and the essential motor driven auxiliary feedwater pump.

Power was restored to the non-essential buses at 1328. Reactor coolant pump 1A was restored at 1408 and 2A at 1411, re-establishing forced circulation.

At 1337, the shift supervisor declared a NOTIFICATION OF UNUSUAL EVENT and made the appropriate notifications.

During the event, power was not lost to the essential power buses. Also, no safety limits were violated. The transient did not result in any challenges to the fission product barriers, or result in any releases of radioactive materials. The NOTIFICATION OF UNUSUAL EVENT was terminated at 1449.

An LER will be submitted within 30 days to further describe this event.

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