ML20058M856
| ML20058M856 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 08/06/1990 |
| From: | Storz L TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NP-33-90-12, NUDOCS 9008130093 | |
| Download: ML20058M856 (2) | |
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, J6 EISON EDISON PLAZA 2
300 MADISON AVENUE i
TOLEDO, OHIO 430'a 0001 I
Docket Number 50-346 3
1 License Number NPF-3 August 6, 1990 United States Nuclear Regulatory Commission NP 33-90-12 Document Control Desk AB-90-0014
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Vashington, D.C. 20555 1
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Subjec t: Voluntary Report of Anticipatory Reactor Trip System (ARTS)
Actuations with the Plant in Mode 5 vith all Rods Previously Inserted Gentlemen:
On June 9, 1990, at 1312 hours0.0152 days <br />0.364 hours <br />0.00217 weeks <br />4.99216e-4 months <br /> and again on June 11, 1990, at 1639 hours0.019 days <br />0.455 hours <br />0.00271 weeks <br />6.236395e-4 months <br />, with the reactor in Mode 5 the Station experienced a series of events which lead to the opening of the Control Rod Drive (CRD) trip breakers.
Each event was initially evaluated and reported to the NRC via the Emergency Notification System (ENS) under 10 CFR 50.72(b)(2)(li) as an actuation of the Reactor Protection System (RPS).
Subsequent review has determined that neither event was an RPS actuation. This Voluntary Report is being submitted to provide the details of'the events..
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The June 9, 1990, event initiated when the 4160 VAC bus D1 de-energized due to a fuse failure. The loss of the bus de-energized the booster fuel oil pump for the auxiliary boiler. This caused the boiler to trip.resulting in a loss of steam supply to steam seals and the subsequent breaking of the condenser vacuum. This caused a loss of the Main Feed Pump Turbine (MFPT) input signal to the Anticipatory Reactor Trip System (ARTS) which opened the CRD trip breakers. The event occurred at the time test jumpers vere being removed at i
the conclusion of the SFAS Sequencer D1 Bus Undervoltage Relay Functional Test, DB-ME-03041. A review of the test procedure and examination of the test jumper that was removed determined no conclusive evidence of the cause of the
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fuse failure which deenergized bus D1.
The June 11, 1990, event initiated when the control mode selector switch at the auxiliary boiler local control panel was unintentionally mispositioned by
'an Instrument and Controls mechanic.
The auxiliary boiler tripped and the scenario developed similar to the June 9 event with.the exception being that i
the control room operator opened the CRD breakers using the manual trip i
button. The operator anticipated the ARTS Actuation when he took manual action.-
1 9009130093 900606 gDR ADOCK 05000346 If PDC
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w Docket Number 50-346 License Number NPF-3 Fage 2 ARTS is only required to be operaole per Technical Specification 3.3.2.3 in Mode 1 (Pover Operation). There is no credible accident scenario in Mode 5 which requires ARTS protection.
Therefore, there is no safety significance to these events.
The Updated Safety Analysis Report (USAR) sections 7.4.1.1 and 7.4.1.2 explain that the control Rod Drive Control System (CRDCS) trip breakers can be opened by three different types of inputs.
One being from RPS, another from ARTS, the third is from the manual trip buttons.
The inputs from ARTS and the manual trip buttons are not considered part of RPS.
In addition ARTS, the manual trip buttons, and the CRDCS are not defined as ESP.
Therefore, baced on the above information, the immediate notitications made to the NRC per 10 CFR 50.72(b)(2)(ii) on June 9 and 11, 1990, are determined to have been not required. This was discussed with the NRC Region III staff and on July 17, 1990, the NRC confirmed thst a Voluntary Report would be acceptable.
Toledo Edison has reviewed the test procedure used in the first event and has decided to modify the test method to limit the potential for fatiguing the fuses. The series of procedures has already been changed and used successfully to meet the monthly surveillance requirement. The Station has alsb initiated an evaluation ot the need for providing a protective guard over the control mode selector switch involved in the second event.
Very truly yours.
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p-L. F. Storz Plant Manager JCS/ eld cci A. B. Davis, Regional Administrator, NRC Region III P. H. Byron, DR-1 NRC Senior Resident Inspector H. D. Lynch, DB-1 NRC Senior Project Manager Utility Radiological Safety Board of Ohio
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