United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-75: Improperly Installed Instrumentation, Inadequate Quality Control and Inadequate Postmodification Testing

                                                         SSINS No.: 6835 
                                                            IN 85-75        

                                UNITED STATES
                           WASHINGTON, D.C. 20555

                               August 30, 1985

                                   INADEQUATE QUALITY CONTROL AND INADEQUATE
                                   POSTMODIFICATION TESTING 


All nuclear power reactor facilities holding an operating license (OL) or a 
construction permit (CP). 


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 


                                                            IN 85-75       
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                                                            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 

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. 


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. 

                                                            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. 


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

1.   Figures Illustrating LaSalle Level Instrument Problems
2.   List of Recently Issued IE Information Notices
Page Last Reviewed/Updated Friday, May 22, 2015