Information Notice No. 85-75: Improperly Installed Instrumentation, Inadequate Quality Control and Inadequate Postmodification Testing
SSINS No.: 6835
IN 85-75
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
August 30, 1985
Information Notice No. 85-75: IMPROPERLY INSTALLED INSTRUMENTATION,
INADEQUATE QUALITY CONTROL AND INADEQUATE
POSTMODIFICATION TESTING
Addressees:
All nuclear power reactor facilities holding an operating license (OL) or a
construction permit (CP).
Purpose:
This information notice is to alert addressees of two recent instances of
improper system modifications, inadequate quality control and inadequate
post modification testing following installation of environmentally
qualified equipment. Recipients are expected to review the information for
applicability to their facilities and consider actions, if appropriate, to
preclude similar problems occurring at their facilities. However,
suggestions contained in this information notice do not constitute NRC
requirements; therefore, no specific action or written response is required.
Description of Circumstances:
LaSalle Unit 2
On June 10, 1985, at 11:30 a.m., the licensee informed the NRC Resident
Inspector that for approximately 5 days LaSalle Unit 2 had been without the
capability of automatic actuation of emergency core cooling (ECCS) and that
for approximately 3 days during this period the plant had been without
secondary containment integrity. The major cause of this condition was
improper installation (the variable and reference legs were reversed) of the
two reactor vessel level actuation switches which control Division I
automatic depressurization system (ADS), low pressure core spray (LPCS), and
reactor core isolation cooling (RCIC).
Unit 2 was shut down in February 1985 for an outage that included
installation of environmentally qualified electrical equipment. LaSalle has
three divisions of ECCS equipment. In March 1985, ECCS Division III was
taken out of service for maintenance. On June 5, 1985, ECCS Division II was
taken out of service for modifications. On June 3, 1985, secondary
containment was declared inoperable for maintenance on the reactor building
ventilation system. The result of these scheduled actions was that two of
three ECCS divisions and secondary containment were inoperable, leaving ECCS
Division I available for use. Subsequently, it was discovered that the
variable and reference legs to the
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IN 85-75
August 30, 1985
Page 2 of 3
reactor vessel level actuation switches for ECCS Division I had been
accidentally reversed since June 3, 1985; thus leaving the plant with no
ECCS automatic actuation and no secondary containment.
The cause of the piping reversal was initially the result of incorrect
design drawings which were released to the contractor on April 1, 1985. The
licensee's site personnel recognized the error on April 4, 1985, and issued
a Field Change Request to correct it. However, the isometric drawings being
used at the location of the modification activities were not corrected.
Therefore, the contractor proceeded to connect piping in the reverse order
from the correct configuration. Figure 1 shows the correct configuration and
Figure 2 shows the reversal. This error was not identified by the Quality
Control (QC) Program because the contractor's QC did not assign inspection
hold points for either the electrical or mechanical piping connections for
any of the 22 instruments replaced by the modification. Consequently, the
installation adequacy was not verified against the design drawings, which
did include the field change and, therefore, which could reasonably be
expected to have revealed the error in the two instruments that were piped
backwards.
Subsequent postmodification testing failed to detect the error because (as
shown in Figure 3) the test shut the instrument block isolation valves and
injected a test pressure source through the installed test connections
downstream from the instrument. This test method isolated the portion of the
piping where the reversal occurred from the test because it was upstream
of the shut valves.
The error was found as a result of a fortuitous observation by an instrument
technician who was performing an unrelated test. If this technician had not
noticed the error, there was a significant possibility that the plant would
have operated with one division of ECCS unavailable.
The safety significance of these events was reduced because the plant was in
a cold shutdown condition. However, no ECCS equipment was available for
automatic operation in the event of low reactor vessel level. In addition,
secondary containment was allowed to be relaxed because the licensee
believed ECCS Division I was operable. Primary containment also was open.
Consequently, had a leak occurred, no ECCS systems would have functioned
automatically and secondary containment would not have been available
either. Technical specifications required the operability of some ECCS
equipment during the time that the plant was shutdown, and upon loss of
ECCS, secondary containment integrity was subsequently required.
Trojan
On July 20, 1985, the Trojan Nuclear Power Plant tripped from 100% power
because of a turbine trip that was caused by the loss of the unit auxiliary
transformer. All systems functioned normally except that low suction
pressure caused one auxiliary feedwater pump to trip and then the other
auxiliary feedwater pump to trip after restart of the first auxiliary
feedwater pump.
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IN 85-75
August 30, 1985
Page 3 of 3
The cause of the trips of the auxiliary feedwater pumps can be traced back
to improper postmodification adjustment and inadequate postmodification
testing following retrofit of environmentally qualified controllers for the
auxiliary feedwater pump trips on low suction pressure were caused by
excessive combined flow from the two auxiliary feedwater pumps that draw
from a single header from the condensate storage tank. The flow control
valves were open farther than required after new environmentally qualified
controllers had been installed during a recent refueling outage.
When the flow control valves were adjusted following the modification of the
controllers, only one auxiliary feedwater pump was run at a time and used to
adjust the control valve limit switch settings. Consequently, when both
pumps were started following the reactor trip on July 20, 1985, the combined
flow was excessive.
Discussion:
Information Notice 85-23, "Inadequate Surveillance and Postmaintenance and
Postmodification System Testing," described a series of events occurring at
McGuire in November of 1984, where improper system modifications and
inadequate postmodification testing also were involved.
No specific action or written response is required by this information
notice. If you have any questions about this matter, please contact the
Regional Administrator of the appropriate regional office or this office.
Edward L. Jordan Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: Eric Weiss, IE
(301) 492-9005
M. Jordan, SRI, LaSalle
(815) 357-8611
Robert Dodds, Region V
(415) 943-3720
Attachments:
1. Figures Illustrating LaSalle Level Instrument Problems
2. List of Recently Issued IE Information Notices
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