United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for December 18, 2000

                       Headquarters Daily Report

                         DECEMBER 18, 2000

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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 - HEADQUARTERS DEC. 18, 2000

MR Number: H-00-0079

                           NRR DAILY REPORT ITEM
                           GENERIC COMMUNICATIONS



Subject: Issuance of IN 2000-21, dated December 15, 2000

NRC Information Notice 2000-21: Detached Check Valve Disc not Detected by
Use of Acoustic and Magnetic Nonintrusive Test Techniques, dated
December 15, 2000

The U.S. Nuclear Regulatory Commission is issuing this information notice
to alert addressees to the potential that nonintrusive testing (NIT) of
check valves may not provide accurate results if the NIT method was not
qualified and if baseline performance was not established when the valve
was known to be operating acceptably.

Technical contact:  J. Colaccino, NRR
                    301-415-2753
                    E-mail: jxc1@nrc.gov

Accession No.  ML003773068


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REGION IV  MORNING REPORT     PAGE  2          DECEMBER 18, 2000

Licensee/Facility:                     Notification:

Houston Lighting & Power Co.           MR Number: 4-00-0020
South Texas 1                          Date: 12/18/00
Wadsworth,Texas                        Resident Inspector on 12/16
Dockets: 50-498
PWR/W-4-LP

Subject: REACTOR TRIP WITH SAFETY INJECTION

Discussion:

At 11 p.m. on December 16, 2000, a manual reactor trip of STP Unit 1 was
initiated when all main turbine governor valves closed during
preparations to perform a scheduled monthly surveillance test of the main
turbine analog/electrohydraulic control cabinet.  A circuit card failure
resulted in the inability to properly shift the main turbine to the
impulse pressure control mode of operation.  An analysis of the exact
failure mode is ongoing.  The affected card has been replaced and tested.

After the reactor trip, primary system pressure decreased because of the
reactor coolant system (RCS) temperature decrease. At 1850 psi, the high
head injection pumps actuated and approximately 2980 gallons were
injected over a period of 6 minutes. The lowest RCS pressure seen was
1463 psi. Normal operating pressure is 2235 psi.  The water level in the
pressurizer dropped to 32.9 percent.  Normal operating level is
55 percent.  RCS temperature went from a normal value of 568 degrees F to
542 degrees F.  The cause of the lowering pressure in the RCS and
subsequent safety injection is being attributed to 3 of 12 steam dump
valves not going full closed.  The licensee found that the valves
remained from 10 to 15 percent open due to a cocked retainer nut on the
steam dump valve hand wheel assembly.  Although the control room
indication was that all steam dump valves were fully closed, the
additional steam demand from these partially open valves caused a rapid
cooldown of the primary system and resulted in the safety injection.  The
main steam isolation valves did not close; nevertheless, the pressure
decrease was terminated by the combination of pressurizer heaters and the
safety injection.

Regional Action:

The resident inspector responded to the site and verified that the plant
had been placed in a stable condition.  The licensee formed an Event
Review Team and is continuing to investigate the event.  Region IV is
monitoring the licensee's progress.

Contact:  Joseph Tapia               (817)860-8243
          Neil O'Keefe               (361)972-2507
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Page Last Reviewed/Updated Thursday, March 29, 2012