United States Nuclear Regulatory Commission - Protecting People and the Environment

Cracking In Feedwater Lines (Generic Letter 79-20)


GL79020 

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

                               May 25, 1979 


ALL PRESSURIZED WATER REACTOR LICENSEES 

Gentlemen: 

We have recently been informed of cracking in feedwater lines at D. C. Cook 
Units 1 and 2. The cracks were discovered after Unit 2 had been shut down to
investigate leakage inside containment. Leaking circumferential through-wall
cracks were identified in the piping heat affected zones of two feedwater 
nozzle to pipe welds for two steam generators in Unit 2. Subsequent 
radiographs revealed crack indications originating on the inside of the 
pipe, in similar locations in the two other steam generator feedwater lines 
in Unit 2.  Four similar locations have been examined in Unit 1 and crack 
indications found in the locations examined. 

You are requested to submit the information identified in the enclosure in 
accordance with 10 CFR 50.54 (f) of the Commission's regulations within 20 
days of receipt of this letter. Compliance with this request does not, of 
course, relieve you from other reporting requirements of your license in 
connection with this matter. 

                                        Sincerely, 


                                        Victor Stello, Jr., Director 
                                        Division of Operating Reactors 
                                        Office of Nuclear Reactor Regulation

Enclosure:
Information Requested on PWR Feedwater Lines

cc w/enclosure
Service List
.

              INFORMATION REQUESTED ON PWR FEEDWATER LINES 

Design 

*1.  Provide as-built piping or isometric drawings of the feedwater line to 
     steam generator sparger within containment. Show details of the design 
     such as dimensions, pipe schedule, support type and locations, pipe 
     restraints, and valve(s). 

*2   Provide the results of any stress or fatigue analyses which was 
     performed for this system. 

Fabrication History 

*1.  Supply a list of the materials for the steam generator sparger, steam 
     generator feedwater nozzles and feedwater piping within containment. 

*2.  Provide the details of the welding process(es) used to make the nozzle-
     to-pipe, pipe to sparger and piping welds. Include details of welding 
     such as preheat, joint configuration (include with or without backing 
     ring), and post weld treatment, if any. 

3.   Provide the NDE performed during and after fabrication of the weld 
     joints requested in question 2. 

4.   Provide the Code edition to which the feedwater piping system was 
     fabricated. 

5.   State the fracture toughness requirements, if any, for the feedwater 
     piping system. 

Preservice/Inservice Inspection and Operating History 

1.   State whether the feedwater system welds received a preservice 
     inspection in accordance with ASME B&PV Code, Section XI. 

2.   Provide the extent of inservice inspection performed on the feedwater 
     pipe to steam generator nozzle welds. Include the results of the 
     examinations, any corrective actions taken and causes of any failures. 

3.   Provide the schedule and extent of inservice inspection for the 
     feedwater system for the next inspection interval. 

4.   Provide any history of water hammer or vibration in the feedwater 
     system and design changes and/or actions take to prevent these 
     occurrences. 

5.   Provide a description of feedwater chemistry controls and a summary of 
     chemistry data. 

* Provide the information available on these items within 20 days and any 
  remaining information within 60 days of receipt of this letter. 
Page Last Reviewed/Updated Wednesday, May 22, 2013