United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-73: Direction-Dependent Leak Characteristics of Containment Purge Valves

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                             WASHINGTON, D.C.  20555

                                September 8, 1988

                                   OF CONTAINMENT PURGE VALVES 


All holders of operating licenses or construction permits for nuclear power 


This information notice is being provided to alert addressees to a potential 
problem regarding unexpected direction-dependent leakage through containment 
purge valves.  It is expected that recipients will review the information for 
applicability to their facilities and consider actions, as appropriate, to 
avoid similar problems.  However, suggestions contained in this information 
notice do not constitute NRC requirements; therefore, no specific action or 
written response is required. 

Description of Circumstances: 

On May 18, 1988, during the performance of a Diablo Canyon Unit 1 containment 
integrated leak rate test (ILRT), the licensee discovered that the 48-inch 
purge system valves inside containment did not have adequate leakage integrity
(Licensee Event Report 50-275/87-25).  The licensee then successfully 
performed a local leak rate test (LLRT) on the purge supply and exhaust 
penetrations by pressurizing the volume between the inboard and outboard 
isolation valves.  Although the LLRT was apparently a success, the valves 
inside containment were pressurized from the direction opposite to the one 
required for them to perform their safety function.  The licensee determined 
earlier that this practice was acceptable, based on information and test data 
supplied by the manufacturer stating that pressure could be applied to the 
valve from either direction and the valve would be leaktight. 

The discrepancy between the ILRT and LLRT findings indicated that the LLRT 
methodology of pressurizing the volume between the isolation valves did not 
adequately confirm the operability of the inside valve. 

The licensee's subsequent investigation found that the valves, Fisher Series 
9200 butterfly valves, have a tapered seat that gives them a directionally 
dependent leakage characteristic.  The valves inside containment are oriented 
so that the discs face outward.  Pressure from containment tends to unseat the
disc gaskets, whereas pressure from the opposite direction tends to seal 

.                                                            IN 88-73
                                                            September 8, 1988
                                                            Page 2 of 2

the gaskets against the tapered valve seats.  The valves were purchased 
because the manufacturer had specified that they could seal in either 
direction.  The licensee reversed the inboard purge valves in Unit 1 and made 
a commitment to do the same for Unit 2. 


Section III.C, "Type C tests," of Appendix J, "Primary Reactor Containment 
Leakage Testing for Water-Cooled Power Reactors," to 10 CFR Part 50 states 
that for containment isolation valve local leak rate testing, "pressure shall 
be applied in the same direction as that when the valve would be required to 
perform its safety function, unless it can be determined that the results from
the tests for a pressure applied in a different direction will provide 
equivalent or more conservative results."  LLRT results could be misleading if
the assumption that an isolation valve does not have directionally-dependent 
leakage characteristics is not true.  Direction-dependent leakage could be a 
characteristic of valves other than the make and model used at Diablo Canyon. 

No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical 
contact listed below or the Regional Administrator of the appropriate regional

                              Charles E. Rossi, Director 
                              Division of Operational Events Assessment 
                              Office of Nuclear Reactor Regulation 

Technical Contact:  James C. Pulsipher, NRR 
                    (301) 492-0877 

Attachment:  List of Recently Issued NRC Information Notices
.                                                            Attachment 
                                                            IN 88-73 
                                                            September 8, 1988 
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                            NRC INFORMATION NOTICES 
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to________

88-72          Inadequacies in the Design    9/2/88         All holders of OLs
               of dc Motor-Operated Valves                  or CPs for nuclear
                                                            power reactors. 

88-71          Possible Environmental        9/1/88         All holders of OLs
               Effect of the Reentry                        or CPs for nuclear
               of COSMOS 1900 and                           power reactors, 
               Request for Collection                       fuel cycle 
               of Licensee Radioactivity                    licensees, and 
               Measurements Attributed                      Priority 1 
               to That Event                                material 

88-70          Check Valve Inservice         8/29/88        All holders of OLs
               Testing Program                              or CPs for nuclear
               Deficiencies                                 power reactors. 

88-69          Movable Contact Finger        8/19/88        All holders of OLs
               Binding in HFA Relays                        or CPs for nuclear
               Manufactured by General                      power reactors. 
               Electric (GE) 

88-48,         Licensee Report of Defective  8/24/88        All holders of OLs
Supplement 1   Refurbished Valves                           or CPs for nuclear
                                                            power reactors. 

88-68          Setpoint Testing of Pres-     8/22/88        All holders of OLs
               surizer Safety Valves with                   or CPs for nuclear
               Filled Loop Seals Using                      power reactors. 
               Hydraulic Assist Devices 

88-67          PWR Auxiliary Feedwater Pump  8/22/88        All holders of OLs
               Turbine Overspeed Trip                       or CPs for nuclear
               Failure                                      power reactors. 

88-66          Industrial Radiography        8/22/88        All NRC industrial
               Inspection and Enforcement                   radiography 

88-65          Inadvertent Drainages of      8/18/88        All holders of OLs
               Spent Fuel Pools                             or CPs for nuclear
                                                            power reactors and
                                                            fuel storage 
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Friday, May 22, 2015