United States Nuclear Regulatory Commission - Protecting People and the Environment

Morning Report for May 27, 1999

                       Headquarters Daily Report

                         MAY 27, 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 I  MAY 27, 1999

Licensee/Facility:                     Notification:

Northeast Utilities                    MR Number: 1-99-0019
Millstone 2                            Date: 05/27/99
Waterford,Connecticut                  SRI PC
Dockets: 50-336
PWR/CE

Subject: MANUAL REACTOR TRIP BECAUSE OF A SECONDARY STEAM LEAKS
Reportable Event Number: 35763

Discussion:

At about 3:12 p.m. on May 25, 1999, operators manually tripped the Unit 2
reactor after experiencing feedwater (FW) system transients and receiving
a report of a steam leak in the turbine building. The plant responded to
the trip as designed with no complications. Operators isolated the steam
supply to the turbine building to ensure the steam leak would be
isolated. Upon completion of the operator's standard post-trip actions,
Unit 2 was stable in Operational Mode 3, hot standby, at normal operating
pressure and temperature. Decay heat removal was provided by the steam
generators using auxiliary feedwater and the atmospheric steam dump
valves. There were no injuries as a result of the steam leak.

The source of the steam leak was the inlet flange on the relief valve on
the 1A main FW heater, the first heater downstream of the "A" main FW
pump. The relief valve, whose setpoint is 450 psi, is designed to protect
the FW heater shell. Due to improperly functioning level control valves
in the 1A and 2A heaters, the 1A heater pressure increased and lifted the
relief valve. The licensee believes that the resulting force on the
relief valve tailpiece imposed sufficient force on the relief valve inlet
flange to relieve the gasket pre-load allowing the gasket to be
displaced.

The licensee plans to remain in Operational Mode 3, hot standby, while
correcting the cause of the trip. In addition to completing some minor
repairs prior to restart, the licensee plans to test and inspect the
level control system for the FW heaters and conduct an inspection of the
secondary plant following the transient imposed by the reactor trip.

Regional Action:

The resident inspectors responded to the control room to observe the post
trip activities until the plant was stable in Operational Mode 3. The
resident inspectors are also following the licensee's investigation into
the cause of the FW system transient.

Contact:  David Beaulieu             (860)447-3170
          James Linville             (610)337-5129
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