United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 87-01: Thinning of Pipe Walls in Nuclear Power Plants

                                                       SSINS No.: 6820     
                                                       OMB No.: 3150-0011  
                                                       NRCB 87-01          


                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C. 20555

                                July 9, 1987

NRC BULLETIN NO. 87-01: THINNING OF PIPE WALLS IN NUCLEAR POWER PLANTS 

Addressees: 

All licensees for nuclear power plants holding an operating license or a 
construction permit. 

Purpose: 

The purpose of this bulletin is to request that licensees submit information
concerning their programs for monitoring the thickness of pipe walls in 
high-energy single-phase and two-phase carbon steel piping systems. 

Description of Circumstances: 

On December 9, 1986, Unit 2 at the Surry Power Station experienced a 
catastrophic failure of a main feedwater pipe, which resulted in fatal 
injuries to four workers. This event was reported in IE Information Notice 
(TN) 86-1069 "Feedwater Line Break," on December 16, 1986; IN 86-106, 
Supplement I., on February 13, 1987; and TN 86-106, Supplement 2, on March 
18, 1987. The licensee submitted Licensee Event Report (LER) 86-020-00 on 
January 8, 1987; Revision 1, LER 86-020-01, on January 14, 1987; and 
Revision 2, LER 86-020-02, on March 31, 1987. A comprehensive report 
entitled "Surry Unit 2 Reactor Trip and Feedwater Pipe Failure Report," was 
attached to the updated LER, Revisions 1 and 2. The findings of NRC's 
Augmented Inspection Team were issued on February 10, 1987, in IE Inspection 
Report Nos. 50-280/86-42 and 50-281/86-42. 

Investigation of the accident and examination of data by the licensee, NRC, 
and others led to the conclusion that failure of the piping was caused by 
erosion/corrosion of the carbon steel pipe wall. Although erosion/corrosion 
pipe failures have occurred in other carbon steel systems, particularly in 
small diameter piping in two-phase systems and in water systems containing 
suspended solids, there have been few previously reported failures in large 
diameter systems containing high-purity water. Consistent with general 
industry practice, the licensee did not have in place an inspection program 
for examining the thickness of the walls of feedwater and condensate piping.

Main feedwater systems, as well as other power conversion systems, are 
important to safe operation. Failures of active components in these systems,
for example, valves or pumps, or of passive components such as piping, can 
result in undesirable challenges to plant safety systems required for safe 
shutdown and accident mitigation. Failure of high-energy piping, such as 
feedwater 

8707020018  
.

                                                             NRCB 87-01
                                                             July 9, 1987
                                                             Page 2 of 3

system piping, can result in complex challenges to operating staff and the 
plant because of potential systems interactions of high-energy steam and 
water with other systems, such as electrical distribution, fire protection, 
and security systems. All licensees have either explicitly or implicitly 
committed to maintain the functional capability of high-energy piping 
systems that are a part of the licensing basis for the facility. An 
important part of this commitment is that piping will be maintained within 
allowable thickness values. 

Actions Requested: 

Within 60 days from the receipt of this bulletin, licensees are requested to
provide the following information concerning their programs for monitoring 
the wall thickness of pipes in condensate, feedwater, steam, and connected 
high-energy piping systems, including all safety-related and 
non-safety-related piping systems fabricated of carbon steel: 

1.   Identify the codes or standards to which the piping was designed and 
     fabricated. 

2.   Describe the scope and extent of your programs for ensuring that pipe 
     wall thicknesses are not reduced below the minimum allowable thickness.
     Include in the description the criteria that you have established for: 

     a.   selecting points at which to make thickness measurements 
     b.   determining how frequently to make thickness measurements 
     c.   selecting the methods used to make thickness measurements 
     d.   making replacement/repair decisions 

3.   For liquid-phase systems, state specifically whether the following 
     factors have been considered in establishing your criteria for 
     selecting points at which to monitor piping thickness (Item 2a): 

     a.   piping material (e.g., chromium content) 
     b.   piping configuration (e.g., fittings less than 10 pipe diameters 
          part 
     c.   pH of water in the system (e.g., pm less than 10) 
     d.   system temperature (e.g., between 190 and 500 F) 
     e.   fluid bulk velocity (greater than 10 ft/s) 
     f.   oxygen content in the system (e.g., oxygen content less than 50 
          ppb) 

4.   Chronologically list and summarize the results of all inspections that 
     have been performed, which were specifically conducted for the purpose 
     of identifying pipe wall thinning, whether or not pipe wall thinning 
     was discovered, and any other inspections where pipe wall thinning was 
     discovered even though that was not the purpose of that inspection. 

     a.   Briefly describe the inspection program and indicate whether it 
          was specifically intended to measure wall thickness or whether 
          wall thickness measurements were an incidental determination. 

     b.   Describe what piping was examined and how (e.g., describe the 
          inspection, instrument(s), test method, reference thickness, 
          locations examined, means for locating measurement point(s) in 
          subsequent inspections).  
.

                                                             NRCB 87-01
                                                             July 9, 1987
                                                             Page 3 of 3

     c.   Report thickness measurement results and note those that were 
          identified as unacceptable and why. 

     d.   Describe actions already taken or planned for piping that has been
          found to have a nonconforming wall thickness. If you have 
          performed a failure analysis, include the results of that 
          analysis. Indicate  whether the actions involve repair or 
          replacement, including any change of materials. 

5.   Describe any plans either for revising the present or for developing 
     new or additional programs for monitoring pipe wall thickness. 

The written report shall be submitted to the appropriate Regional 
Administrator under oath or affirmation under provisions of Section 182a, 
Atomic Energy Act of 1954, as amended. In addition, the original of the 
cover letter and a copy of the report shall be transmitted to the U.S. 
Nuclear Regulatory Commission, Document Control Desk, Washington, D.C. 20555 
for reproduction and distribution. 

This request for information was approved by the Office of Management and 
Budget under blanket clearance number 3150-0011. Comments on burden and 
duplication may be directed to the Office of Management and Budget, Reports 
Management, Room 3208, New Executive Office Building, Washington, D.C. 
20503. 

NRC intends to summarize the information collected under this bulletin and 
study it to help determine if additional actions are required by the staff 
and/or industry. The information will be analyzed and placed in the PDR. 

If you have any questions about this matter, please contact the Regional 
Administrator of the appropriate NRC regional office or the technical 
contacts listed below. 


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


Technical Contacts:  Paul Wu, NRR 
                     (301) 492-8987 

                     Conrad McCracken, NRR 
                     (301) 492-7042 

Attachment:  List of Recently Issued Bulletins 
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Page Last Reviewed/Updated Tuesday, July 23, 2013