05000298/LER-1987-001, :on 870101,two Separate Reactor Scrams Occurred Due to Actuation of Reactor Protection Sys High Pressure Scram Logic.Caused by Procedural Inadequacy.Inservice Leak Test Procedure Revised

:on 870101,two Separate Reactor Scrams Occurred Due to Actuation of Reactor Protection Sys High Pressure Scram Logic.Caused by Procedural Inadequacy.Inservice Leak Test Procedure Revised

ML20213A407
Person / Time
Site:	Cooper
Issue date:	01/29/1987
From:	Horn G, Reeves D NEBRASKA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CNSS870048, LER-87-001, LER-87-1, NUDOCS 8702030262
Download: ML20213A407 (3)

LER-1987-001, on 870101,two Separate Reactor Scrams Occurred Due to Actuation of Reactor Protection Sys High Pressure Scram Logic.Caused by Procedural Inadequacy.Inservice Leak Test Procedure Revised

Event date:
Report date:
2981987001R00 - NRC Website

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While conducting a scheduled Reactor Coolant System (RCS) In-service Leak Test following a refueling / major maintenance outage, two separate reactor scrams occurred due to actuation of the Reactor Protection System (RPS) High Pressure scram logic.

At the time of these events, the plant was in a cold shutdown condition with the Reactor Mode Switch in the SHUTDOWN position and all control rods fully inserted.

Instrument line excess flow check valve leakage verification testing was in progress.

The cause was deternined to be due to a procedural inadequacy. The procedure required establishing and maintaining RCS pressure at a value which encroached upon the Reactor Vessel High Pressure scram setpoints, without blocking the High Pressure Scram relays. A potential contributing factor could have been the instrument line flow testing that was in progress, since such testing has the potential to cause pressure fluctuations in the High Pressure scram sensors sensing lines. Other than the fact that these events constituted unnecessary challenges to the RPS, there was no safety significance associated eith these scrams.

Corrective action to be taken to prevent recurrence of this type of event in the future involves a revision to the In-service Leak Test procedure to provide for test performance in a manner which will preclude unanticipated trips due to High Pressure.

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EVENT DESCRIPTION

While conducting a scheduled Reactor Coolant System In-service Leak Test on January 1, 1987 prior to restoration of the plant to service following a refueling /

major maintenance outage, two separate reactor scrams were initiated; one at 8:07 p.m.,

and another at 11:42 p.m., due to actuation of the Reactor Vessel High Pressure scram logic.

B.

PLANT STATUS Cold shutdown condition with the Reactor Mode Switch in the SHUTDOWN position, all control rods fully inserted and Reactor Coolant System temperature less than 200*F.

At the time of these events, pressure was being maintained at 1028 1 10 psig, in accordance with the guidance established in Procedure 2.1.14, Reactor Vessel In-service Leak Test.

During this same time frame, instrument line excess flow check valves were being tested in accordance with Procedure 6.3.10.2, Instrument Line Flow Check Velve Test.

C.

BASIS FOR REPORT Unnecessary actuation of the RPS Reactor Scram circuitry which is reportable in accordance with 10CFR50.73, paragraph (a)(2)(iv).

D.

CAUSE OF EVENT

Procedural inadequacy in that performance of the In-service Leak Test required pressure to be maintained at a value (1028 10 psig) which encroached upon the Reactor Vessel High Pressure scram setpoints (1035 1 5 psig), without blocking the RPS High Pressure Scram relays. The excess flow check valve testing being accomplished on the instrument lines could also have been a contributing factor since during such testing, pressure fluctuation in the sensing lines used by the High Pressure scram sensors may occur.

E.

SAFETY SIGNIFICANCE

None, since performance of the In-service Leak Test requires the reactor to be in the cold shutdown condition with the Reactor Mode Switch in the SHUTDOWN position.

F.

CORRECTIVE ACTION

Immediate corrective action taken included resetting of the RPS Scram signal, rentoration of RCS pressure to the required test pressure, and completion of the In-service Leak Test.

Additional corrective action which is planned involves a revision to Procedure 2.1.14 to provide for test performance in a manner which will preclude unantic-ipated trips due to High Preneure.

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COOPER NUCLEAR STATION Nebraska Public Power District

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O CNSS870048 January 29, 1987 U. S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.

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Dear Sir:

Cooper Nuclear Station Licensee Event Report 87-001 is forwarded as an attachment to this letter.

Sincerely, g,

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G.

lorn Division Manager of Nuclear Operations GRil:1b Attach.

cc:

R. D. Martin L. G. kuncl K. C. Walden C. M. Kuta 1NPO Records Center ANI Library r

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