ML17279A563

Forwards Response to 870709 IE Bulletin 87-001, Thinning of Pipe Walls in Nuclear Power Plants. Util Committed to Maintaining Design Margin in All Plant Piping Sys

ML17279A563
Person / Time
Site:	Columbia
Issue date:	09/14/1987
From:	Sorensen G WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
GO2-87-245, IEB-87-001, IEB-87-1, NUDOCS 8709220002
Download: ML17279A563 (26)

Text

t REGULATQI. T'NFORMATION.DISTR IBUTIONKSTEN (RIDS)

ACCESSION NBR: 870'7220002 DOC. DATE: 87/09/14 NOTARIZED: NO DOCKET FACIL: 50-397 WPPSS Nuclear Pro Jecti Unit 21 Washington Public Pace 05000397 AUTH. N*NE AUTHOR AFFILIATION SORENSENI G. C. Washington Public Power Supply System

'ECIP. MANE RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

FoY wards response to 870709 IE Bulletin 87-001'Thinning of.

Pipe Walls- in Nuclear Poujer Plants. " Util committed to

~

maintaining design margin in all plant piping sys.

DISTRIBUTION CODE: IE11D COPIES RECEIVED; LTR I ENCL ( SIZE:

TITLE: Bulletin Response (50 DKT)

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/MANE LTTR ENCL ID CODE/MANE LTTR ENCL PD5 LA 1 0 PD5 PD 1 1 SANWORTHi R 1 1 INTERNAL: AEOD/DOA 1 AEOD/DSP 1 1

• EOD/DSP/TPA'B 1 1 NRR/DEBT/ADE 1 1 NRR/DEST/ADS 1 NRR/DEST/NEB 1 NRR/DOE*/EAB 1 NRR/DOEA/GCB 1 1 NR DRE EPB 1 NRR/P HAS/ ILRB 1 FILE 02 1 1 RES/DE/EIB 1 RGN LE 01 1 1 EXTERNAL: LPDR NRC PDR 1 1 NSIC TOTAL NUMBER OF COPIES REQUIRED: LTTR 19 ENCL 18

Washington Public Power Supply System 3000George Washington Way P.O. Box968 Richland, Washington 99352-0968 (509)372-5000 September 14, 1987 G02-87-245 Docket No. 50-397 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

NUCLEAR PLANT NO. 2 OPERATING LICENSE NPF-21 RESPONSE TO NRC BULLETIN NO. 87"01:

THINNING OF PIPE WALLS IN NUCLEAR POWER PLANTS

Reference:

NRC Bulletin No. 87-01: Thinning of Pipe Walls in Nuclear Power Plants, dated 7/9/87 NRC Bulletin No. 87-01 requested that licensees submit information con-cerning their programs for monitoring the thickness of pipe walls in high-energy single-phase and two-phase carbon steel piping systems. Within 60 days from receipt of the subject bulletin, the licensee was to provide certain information concerning their programs for monitoring the wall thick-ness o'f 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. The requested information is included as an attachment to this letter.

The Supply System is committed to maintaining the design margin in all plant piping systems. This is being formally implemented via WNP-2 Plant Procedure 8.3.63, "Surveillance Procedure For Monitoring Pipe Wall Thinning", whose stated goal is to identify and take action on degraded high pressure/energy lines caused by erosion/corrosion.

87p9ZZpppZ p7P9lg ADOCK 5ppp397 PDR 8

PDR

/p(j

(

t, t ~

Page Two RESPONSE TO NRC BULLETIN NO- 87-01 As is the case with the rest of the industry, the WNP-2 pipe wall thinning surveillance effort is evolving. The systems baselined to date represent expected worst case conditions; plans to baseline additional piping systems are being formulated. The Supply System will continue to remain current with the industry trends and developments through INPO, EPRI, and participa-tion in workshops, as well as through our own aggressive efforts to maintain a safe and reliable plant.

Should you have any questions, please contact Mr. P. L. Powell, Manager, WNP-2 Licensing.

Yery truly yours, G. C. S rensen, Manager Regulatory Programs HLA/bk Attachments cc: C Eschels - EFSEC JB Martin - NRC RV NS Reynolds BCP8R RB Samworth - NRC DL Williams - BPA NRC Site Inspector 901A

Question 1:

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

~Res onse:

The codes and standards under which the safety related and nonsafety related plant piping is designed are Section III of the ASNE Boiler and Pressure Vessel Code, and the ANSI B31.1 Power Piping Code; respectively. The WNP-2 FSAR (Section 3.9) lists the major safety related systems and piping design criteria for both NSSS and balance of plant systems.

Question 2:

Describe the scope and extent of your .programs for ensuring that pipe wall thicknesses are not reduced below the minimum allowable thickness.

~Res ense:

The WNP-2 pipe wall thinning surveillance effort quantifies degradation of high pr essure/energy pipe lines due to the er osion/corrosion phenomena.

Identification of those lines to whicH erosion/corrosion wall thinning is occurring is being made by measurement of the pipe wall thicknesses.

Susceptible piping systems are being wall thickness tested at selected known "worst case" locations. The WNP-2 inspection effort includes two-phase and single-phase flow systems. Consideration is given to safety systems with intermittent operation as well as plant process systems. The WNP-2 effort is based on experience and data compiled from other plants which identifies worst case piping systems and locations. Examinatio'ns of selected piping systems which are not deemed ".worst case" are also completed to ensure a thorough plant surveillance (i.e., feedwater, condensate, service water and corrosion inhibited pipe lines).

Question 2a:

Describe the criteria that you have established for selecting points at which to make thickness measurements.

~Res onse:

The susceptible pipe systems are selected based on the thermodynamic/hydraulic conditions (i.e., temperature, pressure, enthalpy, steam quality, fluid velocity, water chemistry, piping, material and pipe nominal wall thickness).

For these susceptible pipe systems, calculations are made for bulk fluid velocities and the erosion rates were predicted based on the Keller equation.*

With the under standing that the fluid'low path (pipe geometry) is a major accelerating factor to the erosion/corrosion rates, ultrasonic thickness

measurement locations are selected according to the fluid flow path; i.e., the worst case conditions exist at elbows, tees, fittings, etc. Interactions between different geometry changes are considered in the selection process.

The EPRI developed CHEC program was not available when selection criteria for the last refueling outage was established, but the selection of susceptible piping for wall thinning surveillance used the same basic parameter s; i.e.,

velocity, geometry, temperature, and material; similar to the Keller equation.

• Reference EPRI NP 3944; April 1985 Question 2b:

Describe the criteria that you have established for determining how frequently to make thickness measurements.

~Res onse:

The frequency of inspection is determined by the measured erosion/corrosion rate, and the relative difference between the actual wall thickness and the minimum wall thickness. The WNP-2 pipe wall thinning surveillance optimizes the inspection frequency to the remaining life; i.e., those pipe lines with large design margins are examined less frequently than those which have two to five operating cycles of remaining life. These pipe lines are scheduled for yearly monitoring during the last three years of life. In some cases, selected pipe can be ultrasonically tested during a forced outage to increase confidence in the calculated E/C rate.

Question 2c:

Describe the criteria that you have established for selecting the methods used to make thickness measurements.

~Res onse:

The WNP-2 pipe wall thinning surveillance uses ultrasonic methods to measure pipe wall thickness. Ultrasonic methods are considered the most'ccurate nondestructive methods available. Radiography may be used on occasion to supplement ultrasonics.

'uestion 2d:

Describe the criteria that you have established for making replacement/repair decisions.

~Res onse:

The Supply System is committed to maintaining the design margin in all plant piping systems. The HNP-2 pipe wall thinning surveillance effort optimizes the inspection frequencies with the remaining life. The remaining life of thinned pipe is calculated and adjusted to plant maintenance/refueling cycles. As the remaining cycles for unrestricted operation approaches two to five, the inspection frequency increases, thus providing sufficient lead, time to schedule repair/replace actions prior to the loss of the design margin.

question 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):

~Res onse:

A. The piping material was considered in the selection process of the single-phase piping systems inspected with ultrasonic thickness measurement techniques.

B. The piping configur ation was considered in the selection pr ocess.

C. The pH of the water was not considered because, as a BHR, the feedwater and condensate are maintained neutral.

D. The bulk system temperature was considered in the selection process.

E. The bulk fluid velocity was considered in the selection process.

F. The oxygen content of the system was not used to identify a particular location though it was used to qualitatively determine the pipe line susceptibility.

WNP-2 is a new boiling water reactor (BHR) plant. As such, less emphasis is placed on single-phase liquid erosion/corrosion (E/C) early in plant life (first four year s). This is justified through an understanding of the E/C process, other BWR/industry experience, and plant specific visual inspections.

There is evidence that BWR erosion/corrosion in feedwater or condensate piping systems is reduced in comparison to pressurized water reactors (PWR's),

partially due to the increased oxide film stability brought about by the relatively high 0 (20 ppb) and neutral pH.

question 4:

Chronologically 'list and summarize the results of al.l 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.

~Res onse:

The'resent scope for the'pipe wall thinning surveillance is an outgrowth of the results from baseline type inspections made during a maintenance outage in 1985 and the first refueling outage in 1986. The conclusion from these, inspections was that E/C is ongoing in some steam piping with conditions of low steam quality and elevated velocities. No evidence was found which indicated a single-phase E/C problem after one operating cycle.

The WNP-2 effor ts for the second refueling outage in 1987 changed from simple testing (go/no-go) to an effort which targets worst case ar eas for actual E/C rate calculations, thus enabling a predictive analysis of component life.

Component life is normalized to the plant refueling outage cycle to optimize the inspection results with repair /replacement.

WNP-2 the has 1986 taken steps to control E/C now that refueling outage inspection results, itdecision has been confirmed.

was made to Due to install a

four moisture preseparators beneath the high pressure turbine exhaust. The preseparator specifically addresses the E/C occurring in the bleed steam piping directly between the high pressure turbine and the moisture separator reheater.

Question 4a:

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.

~Res onse:

The WNP-2 surveillance effort, which quantifies pipe wall thinning due to E/C over the plant life, was formalized prior to the April 1987 refueling outage.

The goal of WNP-2 Plant Procedure 8.3.63, "Surveillance Procedure for Monitoring Pipe .Wall Thinning," is to identify and take action on degraded high pressure/energy lines caused by erosion/corr osion. The procedure provides assurance . that piping systems will be maintained with acceptable design margins. In addition, visual inspections are performed inside piping systems during various maintenance activities. Piping or component degradation due to E/C will be reported and appropriate corrective actions taken. Corrective actions may include replacement/repair of affected piping or increased surveillance. Material substitutions and/or schedule changes will also be considered.

Question 4b:

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

I i

~Res onse:

The piping examined during the 1987 refueling outage and their corresponding identification numbers are pr esented in Table I. The table describes the general function of the pipe line.

The UT measurements are made in accordance with plant procedures. The equipment consists of a dual element transducer generating a straight beam and an analyzer/data logger. Specifically, WNP-2 uses two instruments, a Nova 100D and Krautkramer DMX-l, to take the measurements. The DMX unit is supported by a HP-71B/UDL-71 data logger, IBM PC, and Viewsonics software. The test method uses the pulse/echo technique. Reference thickness measurements are made before and after each continuous string of. measurements. WNP-2 uses a grid approach for a mapping of the surface contour. The grid varies according to pipe diameter. Table II illustrates the grid schedule. The spacing is roughly the same for all pipe diameters, whereas the number of thickness measurements taken at a location incr eases with increasing pipe diameter. All thickness measurement locations (intersection of grids) are permanently marked on the pipe with a low stress stamp for repeatability.

Question 4c:

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

~Res onse:

Two tables are provided to illustrate the extent of the WNP-2 effort and the findings since plant startup. Table III summarizes the results of the ultrasonic thickness measurements. At each location, the thickness measured was greater than the minimum required wall thickness determined by the piping codes. Table III highlights the locations that, based on preliminary conservative E/C rate estimates, may be sites of increased, albeit localized, erosion. Those areas will be included in futur e inspections to evolve more accurate E/C rate information. All data taken indicates that design criteria are being met. Table IV chronologically lists other erosion/corrosion occurrences discovered during plant operation. Also listed in the table for each item are actions taken for repair.

Question 4d:

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.

~Res onse:

Pipe wall thickness measurements at selected locations during Spring 1986 and 1987 outages indicate that each wall thickness measured was greater than the

minimum wall thickness. Pipe with subsequent thickness measurements which indicate remaining life less than two operating cycles shall be considered for repair/replacement, including change of material as appr opriate.

guestion 5:

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

~Res ense:

The HNP-2 pipe wall thinning sur veillance effort is evolving. The systems baselined so far represent expected worst case conditions; plans to baseline additional piping systems are being formulated. The Supply System will continue to remain cur rent with the industry trends and developments through INPO, EPRI, and par ticipation in workshops.

TABLE I

SUMMARY

OF LOCATIONS EXAMINED DURING REFUELING OUTAGE 1987 Test Location Identification Descri tion of Pi in Selected for Surveillance 314"1 16-inch diameter bleed steam piping from high pressure 313-1 turbine to Feedwater Heater ¹6.

312-1 18-inch diameter bleed steam piping from high pressure 311-1 turbine discharge cross-under pipe to Feedwater Heater 311-2 ¹5.

304-1 20-inch diameter bleed steam piping from low pressure 303-1 turbine to Feedwater Heater ¹3.

302-1 302-2 307-1 24-inch diameter bleed steam piping from low pressure 306-1 turbine to Feedwater Heater ¹2.

305-1 356-1 10-inch diameter heater drain piping from second stage 358-1 reheater to drain tank.

362-1 8-inch diameter heater drain piping from second stage 363-1 r cheater drain tank to Feedwater Heater ¹6.

364"1 6-inch diameter heater drain piping from the moisture 365-1 separator reheater first stage drain tank to Feedwater 366"1 Heater ¹6.

367-1 393-1 6-inch diameter bleed steam piping from 16-inch bleed 393-2 steam pipe (same as 314-1) to seal steam evaporators.

390-1 12-inch or 16-inch diameter bleed steam piping from 388-1 high pressure turbine to moisture separator reheater first stage.

TABLE I

SUMMARY

OF LOCATIONS EXAMINED DURING 1987 REFUELING OUTAGE (CONT'D)

Test Location Identification Descri tion of Pi in Selected for Surveillance 369-1 16-inch diameter bleed steam piping from second stage 371-1 moisture separator reheater drain tank to Feedwater Heater 85.

372-1 3-inch diameter heater drain piping from seal steam 372-2 evaporator to Feedwater Heater 85.

342"1 8-inch diameter auxiliary steam piping from the auxiliary boiler to the seal steam evaporator.

403-1 18-inch diameter bleed steam piping from the moisture 403-2 separator reheater to the feedwater pump turbine.

334-1 24-inch diameter feedwater piping discharge from the feedwater pump.

331-1 24-inch diameter condensate piping from Feedwater 331"2 Heater b4 to Feedwater Heater 85.

430"1 6-inch and 3-inch diameter heater vent piping from 430-2 moisture separator reheater to bleed steam piping to 430-3 Feedwater Heater P6.

430"4 431-1 431-2 431-3 458-1 4-inch and 3-inch piping diameter heater vent piping 458-2 from moisture separator reheater to Feedwater Heater 459-1 k'5.

TABLE II EROSION/CORROSION PIPE GRID EXAMINATION SCHEDULE Pipe Actual Linear Distance Circumferential Spacing from 0 Diameter O.D. Between Measurements or 180 as Measured in Inches (inches) (inches) (inches) 90 45 22 2.375 1.85 .95 2.5 2.875 2.25 1.10 3 3.5 2.75 1.35 3.5 4.0 3.15 1.55 4.5 3.55 1.75 5.563 4.35 2.20 1.10 6.625 5.2 2.6 1.30 8.625 6.75 3.40 1.70 10 10.75 8.45 4.20 2.10 1.0 12 12.75 10.0 5.0 2.5 1.25 14 14 11.00 5.5 2.75 1.35 16 16 12.55 6.30 3.15 1.55 18 18 14.15 7.0 3.5 1.75 20 20 15.7 7.8 3.90 1.95 22 22 17.3 8.65 4.30 2.15 24 18.8 9.40 4.70 2.35

Table III Sheet 1 of 2 WHP-2 EROSION/CORROSION RESULTS FOLLOMING FY 1987 REFUELING OUTAGE Test Material and Nominal Minimum Wal 1 1986 1987 Location Line Number Pressure ~rem erature Thickness Thickness ~Outa e Data ~Outa e Oata PSIG oF IH IN IN IN 314-1 16"BS(3)-2 A106 GRB ELBOW 500 470 0.500 0.263 0.490 313-1 16"BS(3)-2 A106 GRB ELBOW 500" 470 0.500 .0.263 0.477 312-1 18"BS(4)-2 A106 GRB ELBOW* 265 420 0.375 0.157 0.297 311-1 18"BS(4)-2 A106 GRB ELBOW* 265 420 0.375 0.157 0.242 311-2 18"BS(4)-2 A106 GRB ELBOW* 265 420 0.375 0.157 0.246 304-1 20"BS(7)-1 A106 GRB ELBOW 50 380 0,375 0.033 0.366 303-1 20"BS(7)-1 A106 GRB ELBOM 50 380 0.375 0.033 0.355 302-1 20"BS(7)-1 A106 GRB ELBOW 50 380 0.375 0.033 0.352 302-2 20"BS(7)-1 A106 GRB ELBOW 50 380 0.375 0.033 0.372 307-1 24"BS(8)-1 A106 GRB ELBOW 50 380 0.375 0.039 0.317 306-1 24"BS(8)-1 A106 GRB ELBOW 50 380 0.375 0.039 0.375 305-1 24"BS(8)-1 A106 GRB ELBOM 50 380 0.375 0.039 0.350 356-1 10"HD(8)-2 A106 GRB ELBOW 570 490 0.365 0.201 0.350 358-1 10"HD(8)-2 A106 GRB ELBOW 570 490 0.365 0.201 0.371.

362-1 8"HD(7)-4 A106 GRB ELBOW 1250 575 0.500 0.347 0.477, 363-1 8"HD(7)-4 A106 GRB ELBOW 1250 575 0.500 0.347 0.486 364-1 6"HD(8)-2 A106 GRB ELBOW 570 490 0.280 0.123 0.315 365-1 6"HD(8)-2 A106 GRB ELBOW" 570 490 0.280 0.123 0.232 366-1 6"HD(8)-2 A106 GRB ELBOW* 570 490 0.280 0.123 0.252 367-1 6"HD(8)-2 A106 GRB ELBOW 570 490 = 0.280 0.123 0.230 393-1 6"BS(2)-2 A106 GRB ELBOM 570 '90 0.280 0.123 0.313 393-2 6"BS(2)-2 A106 GRB ELBOW 570 490 0.280 0.123 0.270 390-1 12"BS(1)-2 A106 GRB ELBOM 570 490 0.406 0.238 0.402 388-1 16"BS(1)-2 A106 GRB ELBOW 570 490 . 0.500 0.299 0.485 369-1 16"BS(9)-2 A106 GRB ELBOW 265 420 0.375 0.140 0.334 371-1 16"BS(9)-2 A106 GRB ELBOM 265 420 0.375 0.140 0.357 372-1 3"HD(10)-2 A106 GRB ELBOW 425 450 0.300 0.049 0.293 372-2 3"HD(10)-2 A106 GRB ELBOM 425 450 0.300 0.049 0.304 342-1 8"AS(1)-2 A106 GRB ELBOM 250 410 0.322 0.071 0.312 403-1 18"BS(5)-2 A106 GRB ELBOW 265 575 0.375 0.157 0.378 0.353 403-2 18"BS(5)-2 A106 GRB ELBOW 265 575 0.375 0.157 0.378 0.362 334-1 24"RFM(l)-5 A106 GRB ELBOW 1950 450 1.812 1.482 2.087 331-1 24"COND(4)-3 A106 GRB TEE 775 420 0.969 0.607 0.888 331-2 24"COND(4)-3 A106 GRB TEE 775 420 0.969 0.607 0.915 430-1 6"HV(11)-4 A335 Pll TEE 1250 575 0.432 0.267 0.430 0.426 430-2 6"HV(11)-4 A335 Pll TEE 1250 575 0.432 0.267 0.436 0.421 .

430-3 3"HV(11)-4 A335 Pll ELBOW 1250 575 0.438 0.141 0.414

.430-4 6"HV(11)-2 A335 Pll ELBOM 50 575 0.280 0.011 0;235 458-1 4"HV(12)-2 A335 Pll ELBOM 570 575 0.237 0.084 0.236 458-2 3"HV(12)-2 A335 Pll ELBOW 570 575 0.300 0.065 0.428 0.411 431-1 '"HV(11)-4 A335 Pll TEE* 1250 575 0.432 0.272 0.382 431-2 6"HV(11)-4 A335 Pll TEE* 1250 575 0.432 0.272 0.428 0.378 431-3 6"HV(11)-2 A335 Pll ELBOW 50 575 0.280 0.011 0.223 459-1 4"HV(12)-2 A335 Pll ELBOW 570 575 0.237 0.085 0.222

• Meets the criteria for increased insPection frequency and/or analysis.

Sheet 2 of 2 TABLE III DEFINITIONS

.Test Location Corresponds with descriptions given in Table 2.

Line Number Pipe line numbers were initially designated by Plant A/E used to define symmetrical piping systems within common anchor groups.

Material and Material used as specified and the fitting type at the Fitting Type ultrasonic thickness test location.

Pressure Design pressure, psig.

Temperature Design temperature, F Nominal Thickness Nominal thickness of pipe line defined as the textbook thickness* for the specified thickness for the pipe schedule. Units are given in inches.

(*Crane Technical Paper 8410)

Minimal Hall Minimum pipe wall thickness based on design temperature Thickness and pressure of the pipe line. The calculation uses the formulation referenced in the ASME Code NC-3641.1 1986 Edition, Equation 3. Units are given in inches.

P Do 222s+py A is taken to.be 0.

1986 Outage Data Six locations were baseline tested in 1986. The number represents the lowest wall thickness in the, entire data field. Units 'are given in inches.

1987 Outage Data The remaining 38 locations were baselined in 1987. The number represents the lowest wall thickness in the entire data field. Units are given in inches.

• Notes: Locations identified as 311-1, 311-2, and 312-1 are common to the bleed steam supply for Feedwater Heaters 5A and 5B. These lines exhibit the greatest E/C rate for the large diameter/higH energy pipe.

These lines also are expected to be influenced the most by the installation of moisture preseparators. The remaining life is expected to increase by several years.

TABLE IV

SUMMARY

OF OTHER INSPECTIONS The following presents the other plant inspections where pipe wall thinning was di scovered. Thi s l i st includes some exampl es where the defini ti on of erosion/corrosion is stretched to include cavitation flow or flashing flow or some other unknown condition.

1983 Auxiliary boiler deaerator return piping was discovered Startup Testing leaking. The investigation concluded that both pitting corrosion and erosion/corrosion were responsible. The pipe section was replaced with the same material and the same design.

1984 NSR drain line (6" HV(11)-4) discovered leaking at the Star tup center of the tee fitting-. Steam impingement on the back of the fitti,ng was caused by an orifice upstream of the fitting. The fitting was changed with a more erosion/corrosion resistant alloy, Type 304 stainless steel.

1984 - 1985 Heater drain valve, HD-FCV-782, was discovered=leaking Operating Cycle from the bottom of the body. The erosion/corrosion was caused by the valve disk leakage. The eroded area was drilled and a Type 410 stainless steel plug was welded to the body for the repair.

1984 1985 Heater drain valve, HD-FCV-11A2, was discover ed leaking Operating Cycle from the bottom of the body. The erosion/corrosion was caused by the valve disk leakage. Three other valves with the same operating conditions were ultrasonically tested and found with little or no erosion/corrosion wall thinning. It was concluded that the singular valve was the problem. A plug of Type 410 stainless steel was welded in place and the valve was returned to operation.

1985 Halkdown of a ~48" mitered elbow revealed a total Maintenance Outage coa$ ings loss on the outside and inside radius of a 180 bend. The pipe was part of the circulating water system used to divert flow back to the circulation water pond. Further analysis'concluded that cavitation erosion/corrosion was caused by operation outside of the recommended design. The design was changed, the

. surface was recoated and operation of the loop was changed to avoid cavitation flow.

12

1985 - 1986 Heater drain valve; KD-FCV-11A2, was again found Operating Cycle leaking. The valve disk was inspected and found to be the cause of the leakage. The hole was again repaired in the same manner and the valve disk was repaired. No further, problems have been encountered.

1985 1986 A leak was discovered on a heater drain line Operating Cycle (4" HV(11)-4). Three pinhole leaks were discovered on the outside bend radius of a 4" diameter pipe located just downstream of a flow control valve. The elbow was replaced with similar material. However; the design was changed to allow greater than 10 pipe diameters between the valve and elbow.

1985 1986 Reactor feedwater return to service, flow control Operating Cycle valve, RFM-FCV-2B, was det~rmined to be responsible for impingement attack on a 45 elbow just downstream. The elbow was repaired by patching with stainless steel pipe sections. Further analysis concluded that the valve was not adjusted to completely close during operation. The valve elbow was replaced during the 1987 refueling outage.

1986 Standby service water pipe line just downstream of Pump Refueling Outage lA and 1B discharge exhibited localized metal loss from a cavitation mechanism. Both lines exhibited wall thinning one on the valve body and the other on the pipe line. The localized areas were weld repaired and mapped for reference.

1986 - 1987 Auxiliary boiler pump 2A recirculation line to Operating Cycle deaerator tank failed due to combined pitting corrosion and erosion/corrosion,. Lack of chemical treatment for pitting corrosion inhibition has been pointed out as a contributing factor. The failure area was replaced and the unit was returned to service.

1986 " 1987 A leak was found on the low pressure side of a reducing Operating Cycle orifice in the CRD pump minimum flow line. The leak was caused by an erosion mechanism likely to be a combined flashing flow and cavitation flow problem.

Evaluation is ongoing. The failure was repaired by replacement with a similar design and material.

1986 1987 Reactor feedwater valve, RFH-FCV-15, was found with a Operating Cycle hole in the bottom. The hole was caused by cavitation flow. The hole was weld repair ed with a patch. The valve was replaced during the 1987 refueling outage with a design modification to address the cavitation problem.

13

1987 The standby service water pipe line mapped the previous Refueling Outage outage was reinspected and valves were replaced.

Additional wall thinning had occurred. The weld r epair areas were found intact; however some E/C attack was evident. The attack areas on the pipe were mapped again. , The wall thinning is believed to have been caused by cavitation from valve flow distortion. With the new valves', the erosion/corrosion is expected to subside.

1987 Reactor feedwater piping removed for a design change in Refueling Outage the vicinity of RFW-FCV-10 was inspected for surface oxide conditions. During the inspection, a small area of erosion at an elbow was observed. The erosion was documented on film. The remainder of the RFW pipe (%0 feet) exposed for the design change was visually inspected. No other indications were found.

1 14

'I