Information Notice No. 84-45: Reversed Differential Pressure Instrument Sensing Lines
SSINS No.: 6835
IN 84-45
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, DC 20555
June 11, 1984
Information Notice No. 84-45: REVERSED DIFFERENTIAL PRESSURE INSTRUMENT
SENSING LINES
Addressees:
All nuclear power reactor facilities holding an Operating license (OL) or
construction permit (CP).
Purpose:
This information notice is provided as a notification of a potentially
significant problem pertaining to reversed differential pressure instrument
sensing lines in safety-related systems. It is expected that recipients will
review the information for applicability to their facilities and consider
actions, if appropriate, to preclude a similar problem occurring at their
facilities. However, suggestions contained in this information notice do not
constitute NRC requirements and, therefore, no specific action or written
response is required.
Description:
In the past few years, the NRC has received a number of reports that
describe events that primarily occurred during construction and
preoperational testing that involved discovery of the high- and low-pressure
sensing lines for safety-related differential pressure instrumentation being
reversed. Table 1, attached to this information notice, is a summary of
those events.
A review of the events reported indicates that the vast majority of them
have occurred at boiling water reactor (BWR) facilities. In all cases
examined, the sensing lines appear to have been reversed during initial
installation of the equipment while the plant was being constructed. At many
facilities, the errors were discovered and corrected prior to commercial
operation, and as such, had limited safety significance. A few of the
events, however, involved installation errors that were undetected for
several years after the plant began commercial operation. For these plants,
there were significant reductior in safety margins because the impact
usually involved disabling of safety-related instrumentation and prolonged
loss of needed safety functions. At one plant, the differential pressure
instrumentation for automatic isolation of a pipe break in the standby
emergency core cooling system remained effectively disabled for several
years after commercial operation.
The available information suggests that there has been a significant
reduction in events involving reversed sensing lines as a result of an
industry-wide
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IN 84-45
June 11, 1984
Page 2 of 2
improvement in plant construction and startup testing. It appears, however,
that adequate procedures for verifying the proper installation of high- and
low-pressure sensing lines may not have been used for the high-flow break
detection instrumentation for the isolation condensers of some early
generation BWRs.
Licensees and applicants should consider improving the applicable
procedures, as appropriate, to ensure that reversed sensing lines in
differential pressure instrumentation are detected and corrected.
Specifically, the licensees of BWR facilities with isolation condensers
should consider verifying the proper installation of sensing lines for
isolation condenser pipe break protection instrumentation, if not already
performed.
If you have any questions regarding this matter, please contact the Regional
Administrator of the appropriate NRC regional office or this office.
Edward L. Jordan Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: R. Singh
(301) 492-8068
Attachment:
1. Table 1: Summary of Reversed Pressure
Sensing Line Events
2. List of Recently Issued IE Information Notices
.
Attachment 1
IN 84-45
June 11, 1984
Page 1 of 2
Table 1 Summary of Reversed Differential Pressure
Sensing Line Events
Found Befor
Commerical
Plant/Date System* Application* When Found How Found Operations
Braidwood AFW Supply line Pre-opera- Drawing Yes
8/83 flow trans- tional safety comparison
mitters and inspection
indicators by NRC
Limerick 1&2 RCS Vessel level/ Pre-instal- Drawing com- Yes
10/82 pressure lation parison
transmitters
LaSalle 1 RHR Pump suction Pre-opera- Hi-flow Yes
5/82 flow trans- tional testing isolation of
mitters suction valve
LaSalle 1 CS Injection valve Pre-opera- Walkdown Yes
5/82 D/P switch tional testing inspection
Foreign RCIC Turbine steam Post-opera- Incidental No
(Several) supply flow tional perio- operator
2/82 indicating dic testing observation
switch
Hatch 2 PCVRS D/P switch Power testing System test Yes
8/78
Quad Cities 2 RR Jet pump riser Refueling Walkdown No
3/78 D/P switches inspection
Oyster Creek SBGT Flow switch Power opera- Maintenance Yes
10/76 tions calibration
testing
Browns MS Steam flow Power testing Testing Yes
Ferry 3 indicating observation
9/76 switch
Browns RCIC Turbine steam Power testing RCIC system Yes
Ferry 2 supply flow testing
8/74 indicating
switch
Peach Bottom MS Steam flow D/P Power testing Incidental Yes
3 indicating operational
8/74 switches inspection
.
Attachment 1
IN 84-45
June 11, 1984
Page 2 of 2
Table 1 Continued
Found Befor
Commerical
Plant/Date System* Application* When Found How Found Operations
Browns RCIC Turbine steam Power testing RCIC Yes
Ferry 1 supply flow system
9/73 indicating testing
switch
Vermont PCVRS D/P switch Vacuum Special No
Yankee breaker investigation
8/73 opened following
valve opening
Oyster Creek IC Condensate Postscram Postscram No
10/72 return D/P isolation walkdown
switch event inspection
Vermont MS Steam flow Pre-opera- Incidental Yes
Yankee switch tional testing operational
8/72 indicating inspection inspection
Monticello HPCI Pump discharge Power testing System test Yes
1971 flow sensing
transmitters
*Abbreviations:
AFW Auxiliary feedwater
CS Core spray
D/P Differential pressure
HPCI High-pressure coolant injection
IC Isolation condensor
MS Main steam
PCVRS Primary containment vacuum relief system
RCIC Reactor core isolation cooling
RCS Reactor coolant system
RHR Residual heat removal
RR Reactor recirculation
SBGT Standby gas treatment
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