Cracking In Feedwater Lines (Generic Letter 79-20)
NUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
May 25, 1979
ALL PRESSURIZED WATER REACTOR LICENSEES
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.
Victor Stello, Jr., Director
Division of Operating Reactors
Office of Nuclear Reactor Regulation
Information Requested on PWR Feedwater Lines
INFORMATION REQUESTED ON PWR FEEDWATER LINES
*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.
*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
5. State the fracture toughness requirements, if any, for the feedwater
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
5. Provide a description of feedwater chemistry controls and a summary of
* 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 Thursday, March 25, 2021