United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for September 3, 1999

                       Headquarters Daily Report

                         SEPTEMBER 03, 1999

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                    REPORT             NEGATIVE            NO INPUT
                    ATTACHED           INPUT RECEIVED      RECEIVED

HEADQUARTERS                           X
REGION I                               X
REGION II                              X
REGION III          X
REGION IV                              X
PRIORITY ATTENTION REQUIRED  MORNING REPORT - REGION III  SEP. 03, 1999

Licensee/Facility:                     Notification:

Commonwealth Edison Co.                MR Number: 3-99-0077
La Salle 1                             Date: 09/02/99
Marseilles,Illinois                    ENS phone call
Dockets: 50-373
BWR/GE-5

Subject: LASALLE UNIT 1 SCRAM

Discussion:

At 1036 on 9/2/99, Unit 1 at the LaSalle County Nuclear Generating
Station scrammed due to low reactor vessel water level of 12.5 inches
(level 3) resulting from a feed- water transient. No emergency core
cooling systems actuations occurred or were required during the
transient. The resident inspectors responded to the control room and
observed satisfactory crew response to the scram. All Unit 1 systems
operated as designed with the exception of minor problems caused during
the automatic auxiliary power fast bus transfer.

LaSalle Unit 2 had experienced an automatic reactor scram caused by
feed-water flow oscillations on 8/21/99. The Unit 1 scram on 9/2/99
represented the second LaSalle reactor scram in 13 days. The Unit 1 scram
on 9/2/99 was caused by human error while performing lubrication of 1B
turbine-driven reactor feed pump electro-hydraulic control servo valves.
1B feed pump had two sub-control loops in the turbine control system, A
and B. The intent was to lubricate the B servo first which required
taking manual control of the B sub-control loop. At a local control panel
an operator mistakenly took manual control of the A sub-control loop
which was controlling the 1B feed pump speed. After the mistake was
pointed out by an instrument mechanic, the operator returned the A
sub-control loop to Auto. This caused a built-up A loop control signal to
reduce 1B feed pump speed. The reduced feed pump speed induced the
feed-water transient which led to the reactor scram on low reactor vessel
water level.

Regional Action:

Resident inspectors observed crew response to the scram.

Contact:  Mel Leach                  (630)829-0705
          Mark Ring                  (630)829-9703
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