ML20234E364

Submits Response to IE Bulletin 87-001, Thinning of Pipe Walls in Nuclear Power Plants, Dtd 870709.Formal Insp Program Not Necessary for Continued Safe Fuel Storage at Facility Due to Permanent Termination of Plant Operations

ML20234E364
Person / Time
Site:	La Crosse File:Dairyland Power Cooperative icon.png
Issue date:	09/09/1987
From:	Taylor J DAIRYLAND POWER COOPERATIVE
To:	Bradley Davis NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
IEB-87-001, IEB-87-1, LAC-12349, NUDOCS 8709220364
Download: ML20234E364 (5)

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. a' D DA/RYLAND hh[M[ COOPERATIVE PO. BOX 817 a 2615 EAST AVE SO : 'LA CROSSE. WISCONSIN 54602-0817 (608) 788-4000 JAMES W. TAYLOR l G neral Manager September 9, 1987 In reply, please refer to LAC-12349 DOCKET NO. 50-409 Mr. A. Bert Davis Regional Director U. S. Nuclear Regulatory Commission Directorate of Regulatory Operations Region III 799 Roosevelt Road Glen Ellyn, IL 60137 l

SUBJECT:

DAIRYLAND POWER COOPERATIVE LA CROSSE BOILING WATER REACTOR (LACBWR).

PROVISIONAL LICENSE NO. DPR-45 NRC BULLETIN N0'. 87-01 " THINNING OF PIPE WALLS IN NUCLEAR POWER PLANTS" l Dear Mr. Davis l

The Dairyland Power Cooperative has reviewed NRC Bulletin No. 87-01 dated July 9, 1987 regarding licensee programs for monitoring the thickness of pipe walls in high-energy single phase and two phase carbon steel piping systems. We have determined that in light of the permanent termination of power plant operations at LACBWR, which eliminates the routine operation of power production related high-energy (> 200*F) piping systems, that a formal inspection program is not necessary for the continued safe fuel storage activities at LACBWR.

Dairyland Power Cooperative indicated in earlier (February 1987) communications with the LACPWR NRC Resident Inspector that DPC did not have a formal inspection program for pipe wall thinning at LACBWR, but that a program was under consideration for specific Turbine plant systems because of historical erosion-corrosion in non-safety related condensate piping. LACBWR never experienced a serious safety challenge to the plant nor endangered the safety of plant personnel or the public because of leaks due to pipe wall thinning damage.

Considering the permanent non-operating status of LACBWR, Dairyland does not consider it necessary to provide a detailed response to each of the action requests in the Bulletin, but does offer the following general responses in order to aid the NRC and nuclear power industry study and future inspection philosophy of the pipe thinning phenomenon.

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. 'Mr. A. Bert Davis LAC-12349 Page 2 September 9, 1987-ACTION 1: " Identify the codes and standards to which the piping was designed and fabricated."

DPC Response Generally, the LACBWR NSSS & Balance of Plant (BOP) piping systems were designed, fabricated, and erected in accordance with ANSI B31.1-1955. In addition, the current ISI program is in accordance with ASME Section XI 1974 Edition, Summer 1975 Addendum.

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 you have established for:

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a. selecting points at which to make thickness measurements 1

b. determining how frequently to make thickness measurements _

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c. selecting methods used to make thickness measurement

d. making replacement / repair decisions" DPC Response i

LACBWR's general past practice regarding the identification, inspec tion, and disposition of pipe wall thinning type failures has been to restore the  !

l system to the original design with little, if any, further examination. The l more recent, though informal, practice at LACBWR has been to survey additional  !

piping and components within a system that required wall thinning repairs using the ASTM minimum wall thickness for new manufactured pipe as th i baseline l acceptance criteria. More rigorous evaluation would be performed if piping was found below this acceptable thickness. Suspect locations would include zones of l flow direction change, phase change, change in size, high fluid velocity (> 15 ft/sec), and other complex piping geometry arrangements. The usual methods of inspection were visual, UT acanning using a thickness standard, or by digital UT  !

thickness measurement. In practically all erosion-corrosion cases, the damaged j materials consisted of carbon steel A-105, A-106, and A-234 specification piping materials. In one case a section of a piping system was replaced using 304 SS .

piping materials in lieu of the original carbon steel material in order to provide erosion-corrosion resistance.

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) ,

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, Mr. A. Bert Davis LAC-12349 .)

Page 3 j September 9, 1987 ,

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d. system temperature (e.g., between 190 and 500*F)

e. Fluid Nik velocity (e.g. , greater than 10 ft/s)

f. oxygen content in the system (e.g., oxygen content less than 50 ppb)"

DPC Response l

As indicated earlier, DPC does not have or presently foresee a.need for a  !

high-energy pipe inspection program for pipe wall thinning at LACB#d. Some of the suggested inspection criteria, such as pipe configuration, materjals, fluid j veloc'.ty, etc. have been employed as factors in evaluating the varinus wall thinning pipe failures experienced at LACBWR. System pH, oxygen content, and. ,

other chemistry factors have been controlled at LACBWR in accordance f.th 1 establishedplantoperatingproceduresandtechnicalspecificationsandhave f generally not been significant factors in previous LACBWR erosion'byalua'tions. )

However, chemistry has been identified as a significant factor in other primary .

system corrosion type evaluations. l J

ACTION 4: " Chronologically list and summarize the results of all inspections that have been performed, which were specifically conducted for the purpose of 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 the inspection." 1 t

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 and how (e.g., describe the inspection instrument (s), test method, reference thickness, locations (

examined, means for locating measurement point (s) in subsequent  !

inspections.  ;.

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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.

DPC Response /

Due to the lack of a formal inspection and repair program for Turbine plant pipe failures, where all known documented failures of this type have occurred at LACBWR, detailed historical inspection records coincident with these pipe wall thinning repairs do not generally exist or do not contain the requested information. However, more recent repair work does include some (available)

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. Mr. A. Bert Davis LAC-12349 Page 4 September 9, 1987 t

documentation of augmented system inspection and evaluation data when repairs f, were required due to wall thinning. Without' conducting extensive research of plant and personal files, the following examples summarize some key repairs of this nature performed at LACBWR. Again, most of these repairs were performed due to their identification of through wall leakage rather than by a surveillance or augmented inspection program with the exception of one recent (1986) case.

• A106 Main Steam reheater drain control piping downstream of valve 90-22-007 partial replacement with 304 SS piping and fittings I (FC 78-11) April 1978.

• Flash Tank drain line 4 LR elbow fitting replacement with like carbon \

steel material (A234 WPB) March 1983. Same area UT inspected for thinning in March 1986 with safe local wall erosion reduction of 31%.  ;

Main Steam reheater drain control piping downstream of valve 90-22-007 including (4/78) stainless steel piping replacement UT inspection for wall thinning April 1986. Inspection disclosed as-left Flash Tank inlet nozzle thinning and thinning of reducer fitting (A234) downstream of valve which was replaced with like XS material in April 1986 (MR 411-86-90)

• #3 Feedwater Heater nozzle (N5) through wall leak (Flash Tank drain nozzle) due to erosion. Nozzle replacement consisted of original material (A 106 Gr B) in April 1986 (MR 237-86-65) with augmented UT thickness inspection of immediate piping and other similar nozzles all which were found acceptable. Service period of original Yuba #3 FWH N-5 nozzle was approximately 10 years.

Ageln, the above high-energy system wall thinning type pipe failures at LACBWR are not intended tc represent all of the failures of this type known to have occurred at LACBhR, but are represeritative of the plant experience with erosion-corrosion failures in high-energy piping systems. The known and most recent case of wall thinning repair which was the result of investigative inspection for thinning was the replacement of the reducer downstream of valve 90-22-007.

ACTION 5: " Describe any plans either for revising the present or for developing new or additional programs for measuring wall thickness."

DPC Response For reasons explained earlier, DPC no longer is planning or preparing an augmented inspection program for wall thinning in any LACBWR high-energy piping systems which may be susceptible to erosion / corrosion damage. However, DPC is considering an inspection program for its conventional operating power plants as a result of the Surry and other power plants' incidents involving high-energy thin wall piping failures. In addition, LACBWR is considering implementation of a routine pipe wall corrosion inspection program of the High Pressure Service Water System which uses raw Mississippi River water in the turbine plant PCl-35 l

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o Ar. A. Bert Davis LAC-12349 Page 5 September 9, 1987 because of historical and recent pit corrosion leakage. A recent UT thickness survey of select locations of the large bore HPSW piping in the turbine plant suggests that such an_ inspection program may benefit the long term reliability of this system.

Dairyland is pleased to be able to contribute to this NRC inquiry with the l above information and trusts that our response is satisfactory in light of the present and. future operating status of LACBWR. In closing it is our conclusion that the minor erosion / corrosion wall thinning in high-energy systems experienced at LACBWR is generally consistent with and follows the industry's knowledge and current understanding of this problem with respect to the type of service, system age, materials, configuration, etc.

If you have any questions or comments regarding our response to this Bulletin, please contact us. ,

l Sincerely, DAIRYLAND POWER COOPERATIVE

?W Sh James W. Taylor General Manager {

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cc U. S. Nuclear Regulatory Commission j Document Control Desk Washington, DC 20555 Mr. Peter Erickson, LACBWR Project Manager i Division of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission j Mr. Ken Ridgway, NRC Resident Inspector I

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