ML20238F074
| ML20238F074 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 09/10/1987 |
| From: | Cutter A CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML20238F076 | List: |
| References | |
| IEB-87-001, IEB-87-1, NLS-87-181, NUDOCS 8709150367 | |
| Download: ML20238F074 (7) | |
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3' CP&L Caronna Power & Light Company SEP 101987 SERIAL: NLS-87-181 United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS.1 AND 2 DOCKET NOS. 50-325 & 50-324/ LICENSE NOS. DPR-71 & DPR-62 NRC BULLETIN NO. 87-01: THINNING OF PIPE WALLS IN NUCLEAR POWER PLANTS Gentlemen:
Carolina Power & Light Company hereby submits information requested by NRC Bulletin No. 87-01, dated July 9,1987. The subject bulletin required the submission of information concerning a licensee's programs for maintaining the thickness of pipe walls in high-energy single-phase and two-phase carbon steel piping systems.
This submittal provides the requested information regarding the Brunswick Steam ;
Electric Plant program for monitoring the wall thickness of pipes in the condensate, '
feedwater, steam, and connected high energy piping systems. Should you have any questions concerning this response, please contact Mr. A. W. Schmich at (919) 836-8759.
Your zery trul ,
/f bff'n A. B. Cutter - Vice Pres nt Nuclear Engineering I
ABC/AWS/lah (5270AWS) )
l Attachment cc: Dr. 3. Nelson Grace Mr. W. H. Ruland Mr. E. Sylvester A. B. Cutter, having been first duly sworn, did depose and .say that the information contained herein is true and correct to the best of his information, knowledge and belief; and the sources of his information are officers, employees, contractors, and agents of fl)
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Response to NRC Bulletin No. 87-01, Thinning of Pipe Walls in Nuclear Power Plants.
The following provides specific detail for each of the Bulletin action items.
l ACTION 1:
I Identify the codes or standards to which piping was designed and fabricated.
CP&L Response:
BSEP piping was designed and fabricated per original design specifications to the following codes and standards:
USA Standard Code for Pressure Piping, Power Piping (USAS) B31.1 American National Standards Institute (ANSI) B31.1 -
American Society for Testing and Materials (ASTM)
American Society of Mechanical Engineers (ASME)
Pipe Fabrication Institute (PFI)
Manufacturer's Standardization Society of the Valve and Fitting Industry (MSS)
U. S. Department of Commerce - Commercial Standard (USDC CS)
American Water Works Association ACTION 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 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 CP&L Response:
During internal repair work to the Unit 1 No. 4 high pressure feedwater heaters in 1983, the extraction steam piping to the heater was noted to have severe " tiger striping." This line has an approximate moisture content of 13% and a bulk rate velocity of 149 fps. The arbon steel line was immediately replaced with A335, P22 chrome moly piping. The lines in Unit 2 were replaced during the 1984 refueling outage in Unit 2. The moisture separator reheater (MSR) shell drain lines were also replaced on Unit 2 in 1984 because of throughwall failures. At that time, the need for an inspection program for secondary plant steam piping was er tblished. In 1985 and 1987, inspections were performed on Unit 1; in 1986, r Unit 2 was inspected. Methods and results of those inspections are given in response to action 4..
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In 1985 and 1986, UT inspections for wall thickness were performed on steam piping subject to erosion corrosion. The lines were selected based on carbon steel pipe,
} industry experience up to that time, and service conditions. The inspection locations on the lines were at elbows and tees where degradation would occur first. From the measurements taken, a frequency was established for monitoring.
Measurements were performed utilizing a Digi-Sonic 502 (D-meter). This was chosen because it would be performed quickly and economically with in-house personnel. If an occurrence of pipe wall thinning was found, that pipe would be inspected during the next refueling outage. For those cases where thinning was not i detected, the piping would be inspected during the second refueling outage following the test. Repair and replacement decisions were also based on conditions found. The philosophy has been if readings taken were below manufacturing tolerance of nominal wall, but above calculated minimum wall, the pipe would be scheduled for replacement during an upcoming outage. Piping found below calculated minimum wall would be repaired immediately.
ACTION 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 apart)
- c. pH of water in the system (e.g., pH less than 10)
- d. System temperature (e.g., between 190* and 500 F)
- e. Fluid bulk velocity (e.g., greater than 10 f t/s)
in 1987, six single-phase lines were added to the scope of the wall thickness l inspection program because ot the Surry event. Selection of the inspection lines l and locations was based on carbon steel pipe, piping configuration, system !
temperature, bulk rate velocity, and areas where valve cavitation problems were known to exist. Since the pilin a BWR is controlled and the oxygen content for the Condensate and Feedwater Systems has remained > 15 ppb throughout the life of the plant, these factors were not considered as ? priority in selection of inspection i locations. I ACTION 4:
Chronologically list and summarize the results of all inspections that have been i performed, which were specifically conducted for the purpose of identifying pipe wall thinning, whether or not pipe wall thinning was discovered, and any other l inspections where pipe wall thinning was discovered even though that was not the l 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.
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- b. Describe what piping was examined an-i how (e.g., describe the inspection instrument (s), test method, reference thickness, locations examined, means for locating measurement point (s) in subsequent inspections).
- 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.
CP&L Response:
1985 Unit I and 1986 Unit 2 UT Inspections 1
8 Inspections for wall thickness were performed on secondary steam piping subject to erosion / corrosion. Measurements were taken using a Digi-Sonic 502. The instrument was calibrated by use of a test block on the instrument before and after each location inspection. Locations were tested as follows (refer to Figure 1):
For elbows: Measure to approximate center of elbow from weld and mark a point "A"(by use of a metal marker). Using "A" as a center, mark a point equal to 1/2 the diameter of the pipe at points "B" and "C", and mark a point "D" and "E" equal to 1/4 the diameter of the pipe. Scan each quadrant and record the low, high, and typical readings in each quadrant.
For tees: Measure to the approximate center between two velds under the tee and mark a point "A". Using "A" as a center, mark a point equal to 1/3 the diameter of the pipe at points "B", "C", "D", and "E". Scan each quadrant and record the low, high, and typical readings in each quadrant.
Unit 1 Results UT inspections were performed at fif ty-four locations on 27 lines. Two lines were severely eroded, the extraction steam piping (EX), from the deaerator to the No. 3 low pressure feedwater heaters and the MSR shell drain line. The EX line was temporarily repaired with a carbon steel spool piece. Plant modifications (86-028 and 86-040) replaced both of these lines during the 1987 refueling outage with A335, P22 chroine moly piping. Slight thinning was found on 5 lines. They did not appear to be in any immediate danger of throughwall failure, but monitoring at each refueling outage was established. The other 20 lines showed little or no tninning of the pipe wall, and monitoring of these lines was established for every other refueling outage. See Table 1.
Unit 2 Results Forty-five UT inspections were performed on 26 lines. One line, the EX from the deaerator to the No. 3 feedwater heaters, was severely eroded. This line was temporarily repaired with carbon steel spool pieces and is scheduled to be replaced by a plant modification (87-135) with A335, P22 chrome moly pipe during the 1988 refueling outage. Five lines showed slight thinning, and monitoring was established for every refueling outage. The other 20 lines showed little or no wall thinning, and monitoring at every other refueling outage was established. See Table 2.
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1 Y 1987 Unit 1 UT Inspection and Results The single-phase lines selected were the reactor feed pump suctlon, heater drain pump discharge, No. 2 and No. 3 feedwater. heaters, condensate recirculation,
, reactor feed pump recirculation, and reactor core isolation cooling. Twenty-six
-locations were measured on these lines. Manual A-scan UT was used since current research has revealed this method to be very accurate, reliable., and repeatable. A special procedure is attached which outlines the method. The measurements were within manufacturing tolerance of nominal wall.- In addition, the five lines frorn the 1985 Unit 1 inspections were examined. These readings revealed a slight variance of the wall thickness; however,' the readings were still within manufacturing tolerance of nominal wall.-
ACTION 5:
Describe any plans either for revising the present or for developing new or additional programs for monitoring pipe wall thickness.
CP&L Response:
. Currently, the BSEP program for wall thinning inspections is being revised to 4 prioritize carbon steel water and steam systems in the plant. :The new program will j also address acceptance and rejection criteria based on. thinning. No plans are being made to change the A-scan UT method that is currently in place. BSEP will be reviewing various computer programs, including the current EPRI program, to
' determine if they would be advantageous to the development of inspection locations for future erosion / corrosion inspections. BSEP has obtained the EPRI Erosion Corrosion Matrix (CHEC Program) and intends to use it in developing the .
upcoming Unit 2 outage inspection program.
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