United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 84-45: Reversed Differential Pressure Instrument Sensing Lines

                                                            SSINS No.: 6835 
                                                            IN 84-45       

                                UNITED STATES
                            WASHINGTON, DC 20555

                                June 11, 1984

                                   SENSING LINES 


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


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. 


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 


                                                              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 

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

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
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 

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 

Hatch 2          PCVRS   D/P switch     Power testing  System test   Yes

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

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

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
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

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


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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