Information Notice No. 89-53: Rupture of Extraction Steam Line on High Pressure Turbine

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

                                 June 13, 1989 

                                   PRESSURE TURBINE


All holders of operating licenses or construction permits for nuclear power 


This information notice is being provided to alert addressees to a potential 
generic problem involving erosion in carbon steel piping in secondary plant 
systems.  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 April 18, 1989, a reactor trip from 100 percent power on high pressurizer 
pressure occurred at Arkansas Nuclear One, Unit 2 (ANO-2) as a result of a 
main turbine trip.  The turbine tripped when steam escaping from a ruptured 
high pressure steam extraction line caused a spurious actuation of the 
electrical hydraulic control system's solenoid operated trip valve.  The pipe 
rupture occurred about 3 inches below the weld which joins a 12-foot section 
of straight 14-inch diameter pipe to a second-stage extraction nozzle on the 
high pressure turbine.  The pipe wall at the rupture was worn to a thickness 
of about 1/32-inch (nominal wall thickness is about 3/8 inches).  The 180 
degree "fishmouth" rupture was about 3 inches wide.  This straight run of 
14-inch diameter pipe terminates at an elbow.  This elbow was replaced during 
the last outage because of erosion induced wall thinning.  The elbow 
degradation was discovered as a result of the licensee's secondary system 
surveillance program for wall thinning.  However, the recently failed pipe and 
those of similar geometries were not included in the surveillance samples.  In 
addition, the degraded condition of the pipe was not detected during 
replacement of the elbow.

.                                                                 IN 89-53
                                                                 June 13, 1989
                                                                 Page 2 of 2 


The high pressure turbine at ANO-2 has two 14-inch second-stage extraction 
steam lines.  Ultrasonic testing of the second 14-inch second-stage extraction 
steam line identified similar wall thinning conditions.  The piping for both 
extraction steam lines has been replaced. 

The root cause assessment of this erosion phenomenon has not been finalized.  
The licensee currently believes that the flow turbulence necessary to induce 
erosion was likely set up by the geometry of the nozzle-to-pipe connection.  
The outside diameters of the nozzle and pipe were essentially equal; however, 
the thickness of the nozzle wall was greater than the thickness of the pipe 
wall.  This resulted in a mismatch between the inside diameter of the nozzle 
and the inside diameter of the pipe.  The expansion of the steam as it exited 
the nozzle is postulated to have caused the accelerated erosion of the pipe.

NRC Information Notice 89-01 "Valve Body Erosion," dated January 4, 1989, and 
NRC Information Notice 88-17, "Summary of Responses to NRC Bulletin 87-01, 
'Thinning of Pipe Walls in Nuclear Power Plants'," dated April 22, 1988, 
provide additional discussion on erosion of piping systems.

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:  L. Gilbert, Region IV
                    (817) 860-8156

Attachment:  List of Recently Issued NRC Information Notices
.                                                            Attachment 1
                                                            IN 89-53 
                                                            June 13, 1989 
                                                            Page 1 of 1

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

88-46,         Licensee Report of            6/8/89         All holders of OLs
Supp. 3        Defective Refurbished                        or CPs for nuclear
               Circuit Breakers                             power reactors. 

89-52          Potential Fire Damper         6/8/89         All holders of OLs
               Operational Problems                         or CPs for nuclear
                                                            power reactors. 

89-51          Potential Loss of Required    5/31/89        All holders of OLs
               Shutdown Margin During                       or CPs for nuclear
               Refueling Operations                         power reactors. 

88-88,         Degradation of Westinghouse   5/31/89        All holders of OLs
Supp. 1        ARD Relays                                   or CPs for nuclear
                                                            power reactors. 

89-50          Inadequate Emergency          5/30/89        All holders of OLs
               Diesel Generator Fuel                        or CPs for nuclear
               Supply                                       power reactors. 

89-49          Failure to Close Service      5/22/89        All holders of OLs
               Water Cross-Connect                          or CPs for nuclear
               Isolation Valves                             power reactors. 

89-48          Design Deficiency in the      5/22/89        All holders of OLs
               Turbine-Driven Auxiliary                     or CPs for nuclear
               Feedwater Pump Cooling                       power reactors. 
               Water System 

89-47          Potential Problems With       5/18/89        All holders of OLs
               Worn or Distorted Hose                       or CPs for nuclear
               Clamps on Self-Contained                     power reactors and
               Breathing Apparatus                          fuel facilities. 

89-46          Confidentiality of            5/11/89        All holders of 
               Exercise Scenarios                           licenses for fuel 
                                                            cycle facilities 
                                                            and byproduct 
                                                            material licensees 
                                                            having an approved 
                                                            emergency response 
OL = Operating License
CP = Construction Permit 

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