05000361/LER-1982-138, Forwards LER 82-138/01T-0.Detailed Event Analysis Submitted

Forwards LER 82-138/01T-0.Detailed Event Analysis Submitted

ML20069P095
Person / Time
Site:	San Onofre
Issue date:	11/24/1982
From:	Ray H SOUTHERN CALIFORNIA EDISON CO.
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML20069P098	List: 05000361/LER-1982-138, Forwards LER 82-138/01T-0.Detailed Event Analysis Submitted 05000361/LER-1982-138-01, /01T-0:on 821109,during Momentary Loss of Power to Feedwater Control Sys,Reactor Manually Tripped & ECCS Automatically Initiated.Caused by Dislodging of Power Cord. Control Cabinets Secured W/Tie Wraps & Training Updated
References
NUDOCS 8212070350
Download: ML20069P095 (3)

LER-1982-138, Forwards LER 82-138/01T-0.Detailed Event Analysis Submitted

Event date:
Report date:
3611982138R00 - NRC Website

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( F 14) 4,2-7 700 November 24, 1982 U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region V 1450 Maria Lane, Suite 210 Walnut Creek, California 94596-5368 Attention:

Mr. R. H. Engelken, Regional Administrator

Dear Sir:

Subject: Docket No. 50-361 14-Day Follow-Up Report Licensee Event Report No.82-138 San Onofre Nuclear Generating Station, Unit 2

Reference:

Letter, H.B. Ray (SCE) to R.H. Engelken (NRC),

dated November 10, 1982 The referenced letter confirmed our prompt notification to the NRC on November 9,1982 of a reportable occurrence involving a manual trip of the reactor and initiation of the Emergency Core Coaling System (ECCS).

Pursuant to Appendix A Technical Specification 6.9.1.12g to Operating License NPF-10 for San Onofre Unit 2, this submittal provides the required follow-up report with a completed Licensee Event Report (LER) l for this occurrence.

Section 6.9.1.129 requires that conditions arising from natural or l

manmade events that, as a direct result of the event require unit shutdown, operation of safety systems, or other protective measures required by Technical Specifications, shall be reported within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> with a written follow-up report within 14 days.

On November 9,1982 while in Mode 1, momentary loss of power to the Feedwater Control System was experienced. As a precaution, the reactor was manually tripped. The ECCS was automatically initiated during the resulting cooldown.

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R. H. Engelken November 24, 1982 Technicians were opening Cabinet 2L-150 to connect a recorder to measure feedwater flow during an anticipated trip test. While opening the cabinet door, the technician dislodged a power cord, deenergizing the Feedwater Control System (FCS) and the Steam Bypass Control System (SBCS).

The Operators noticed dropping Steam Generator (S/G) levels and attempted to manually raise the Main Feedwater (MFW) Pump turbine speed and reopen Main Feedwater and Bypass control valves. These efforts were unsuccessful because with the Feedwater Control System deenergized, manual as well as automatic control was disabled. The reactor was manually tripped at 1556 hours0.018 days <br />0.432 hours <br />0.00257 weeks <br />5.92058e-4 months <br /> as S/G levels continued to drop.

A technician noticed that annunciator 57C-8, " Instrument BUS 1 Instrument Rack Power Supply Failure", was illuminated and began checking instrument rack cabinets to find which cabinet was without power.

He discovered 2L-150 open and deenergized, and informed an SR0 in the Control Room that he would attempt to reenergize the cabinet. Upon returning to the cabinet, he discovered the loose power cord and pushed its plug more finnly into the receptacle, returning power to the SBCS and Main Feedwater Control System at 1600.

When power was returned, two of the SBCS valves opened fully, and MFW Main and Bypass valves reopened to their previously-set manual control positions. The rapid Feedwater addition caused the RCS to cool down sufficiently to lower the pressurizer level to below 0% and reduce RCS pressure, which resulted in a Safety Injection Actuation Signal (SIAS) at 1601. Safety injection performed as designed. Minimum RCS pressure reached during the transient was 907 psia. No evidence of substantial voiding in the RCS was apparent during or after the event.

At this point, initiating events were concluded, S/G level and Reactor Coolant System cooldown rate were brought under control.

In addition to the immediate corrective actions taken as described above, the following is the status'of other corrective measures undertaken to prevent recurrence of this type of event:

1.

All control cabinets with power supply connectors similar to that described in this incident were secured by " Tie-Wraps".

A permanent modification will be developed to secure these connectors to their respective cabinets by positive means to prevent inadvertent dislodging.

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R. H. Engelken November 24, 1982 2.

Requalification training program for the Operators and Shift Technical

' Advisors (STA's) will include lessons learned from this incident.

This will include as a minimum, instructions to Operators to return any manual control settings undertaken during such an incident, to appropriate conservative settings when not continuously being observed.

The cooldown transient evaluation is continuing and will be the subject of a separate LER 82-136 per Technical Specifications 3.4.8.lb and 6.9.1.13b to be submitted before December 9,1982.

A detailed engineering evaluation of the ECCS initiation is underway.

This will be the subject of a Special Report to be submitted before February 8,1983, per Technical Specifications 3.5.2 Action b and 6.9.2.

The evaluation will also identify any necessary design changes resulting from this incident.

The public health and safety were not affected by this occurreme Once all safety systems performed as required.

Enclosed LER 82-130 ujdresses this event.

If there are any questions, please contact me.

Sincerely, bfh

[ Nldtf7%

Enclosure: LER 82-138 cc:

A. E. Chaffee (USNRC Resident Inspector, San Onofre Unit 2) l i

U. S. Nuclear Regulatory Commission l

Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Office of Management Information and Program Control Institute of Nuclear Power Operations