ML20235G855
| ML20235G855 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, Limerick, 05000000 |
| Issue date: | 09/24/1987 |
| From: | Alden W PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Russell W NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-87-001, IEB-87-1, NUDOCS 8709300259 | |
| Download: ML20235G855 (1) | |
Text
-_-______y_____
.F PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHIA A. PA.19101 (215)841-4000 September 24, 1987 Docket Nos.:
50-277 50-278 50-352 Mr. William T.
Russell Administrator, Region I U. S. Nuclear Regulatory Commission ATTENTION:
Document Control Desk Washington, DC 20555
Subject:
Response to IE Bulletin 87-01
" Thinning of Pipe Walls in Nuclear Power Plants"
Dear Mr. Russell:
The attached responses for both Peach Bottom and Limerick are being resubmitted with a date of signature.
This information was omitted from the original transmittal because of a clerical oversight.
Please take appropriate action to correct the files for this Bulletin.
We regret any inconveniences this may have caused.
Very truly yours, d*
f g-s_
8709300259 870924 PDR ADOCK 05000277
//
G PDR William M. Alden Engineer-In-Charge Licensing Section cc:
Addressee J. W. Gallagher w/ attachment T.
P. Johnson w/ attachment E. M.
Kelly w/ attachment Attachment t
COPY L
PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 -
PHIL ADELPHI A. PA.19101 821st Bet soo)
' "T.T,f.^,0.77".'"
September 9, 1987 Docket Nos. 50-277 Mr. W. T. Russell,' Administrator 50-278 U.S. Nuclear Regulatory Conmission Region 1 Attn: Doctment Control Desk -
Washington, DC 20555 Peach Bottom Atomic Power Station, Units 2 6 3 Sub. Ject :
Response to 1.E.Bulletin 87-01 " Thinning of Pipe Walls'at Nuclear Power Plants" Mod Reauest #2259 NRC Bulletin No. 87-01 dated 7/9/87
Reference:
Peach Bottom Atomic Power Station Units 2 & 3
Attachment:
Response to NRC 1. E. Bulletin No. 87-01 Thinning of Pipe Walls in Nuclear Power Plants
.Flie:
GOVT 1-1 (Bulletins)
Dear Mr. Russell:
The referenced bulletin requests infonnation regarding utility programs addressing pipe wall thinning due to erosion / corrosion under Philadelphia Electric's response single and two phase flow conditions.
to the five requested actions is provided in the following attachment.
If further information is required, please do not hesitate to contact us.
Sincerely, k
b PRB/pdO806S706 Attachment I
Copy to: Addressee T. P. Johnson, Resident inspector U.S. Nuclear Regulatory Conmission Peach Bottom Atomic Power Station
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o Distribution:
S. J. Kowalski J. W. Gallagher M. J. Cooney R. H. Logue/W. M. Alden G. M. Leitch M. J. McCormick H. H. Traver R. A. Segletes T. C. Hinkle D. M. Smith L. B. Pyrlh J. M. Madara, Jr.
D. R. Helwig A. R. Diederich F. J. Coyle P. K. Pav11 des 1
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ATTACFNENT l
Peach Bottom Atomic Power Station Units 2 C 3 Response to NRC 1.E. Bulletin No. 87-01 Thinnino of Pipe Walls in Nuclear Power Plants The subject NRC Bulletin was generated as a result of the 1986 Surry feedwater pipe break accident. Licensees were requested to provide the following information concerning their programs for rronitoring-the wall thickness of 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.
Information for Peach Bottom Units.2 & 3 in response to 1.E.Bulletin 87-01 is provided below.
1.
Identify the codes or standards to which the piping was designed and fabricated.
Response
The piping systems included in the Peach Bottom Units 2 and 3 Inspection programs are listed in Table 1.
The applicable design code for each system is as shown.
2.
Describe the scope and extent of your programs for ensuring that pipe wall thicknesses are not reduced below the minimun allowable thickness.
Include in the description the criteria that you have established for:
Selecting points at which to make thickness treasurerrents.
a.
b.
Determining how frequently to make thickness measurements.
Selecting the methods used to make thickness c.
measurements.
d.
Making repalr/ replacement decisions.
Resoonse:
The inspection programs for Peach Sottom Units 2 & 3 address carbon steel piping systems subject to single phase or two phase flav erosion / corrosion (E/C). Each is addressed separately belov:
l,;
1 Two Phase E/C l3
'J Based.on our experience dealing with E/C of carbon steci j
1
- piping' In fossil stations,. chrone-noly piping was installed in' systems such as extraction steam and piping doanstream of control.. valves in feedwater heater drains.
This application
-includes most of the large dlameter lines subject to two
. phase: flow.
Inspection of particular systens such as the
. turbine _crossaround piping (tiger striping) has been
- performed for a number of years. A comprehensive review of piping systems to address E/C of carbon steel piping subject to wet stesn envi ronments was performed in 1983.
This review concentrated on identifying the remaining carbon steel piping subject to two phase f. low.
The analysis included the review of the system operating parameters and whether.there were significant pressure drops (orifices, control valves) which
'could. lead to flashing.or cavitation.
The operating history
. of the various systers was also reviewed to Identify prevlous repairs due to leaks or system operational problems.
Based on this review,16 carbon steel piping systens or portions thereof where included in the insoection program as shown In Table 1.
The piping Inspection points were selected based upon a.
locations in the system where there are abrupt changes in the direction of floa (elboas, tees) Innedlately downstream of significant pressure drops Cortfices, contro1' valves) and at other fittings which cause floa perturbations (reducers, branch connections).
b.
The frequency of the inspections for each of the 16 piping systems is determined by review of the prior.
' inspection data.
Those systems which historically have shown significant E/C damage are scheduled for Inspection every refueling outage. The remaining lines l
which have not shown E/C damage based on data review or j
have low estimated erosion rates are scheduled for
-l Inspection every 2 or 3 refueling outages.
c.
All. Inspections to date have been by manual ultrasonic j
(UT) thickness measurements supplemented by visual l
examination where practical.
PECo chose UT because l
it provides accurate verifiable data, d.
Repatr/ replacement decisions are based upon review of the inspection data, estimating the erosion rate and camparing it to the design min. wall requirements.
All piping belov code min. wall or anticipated to encroach
{
on min wall within the next operating cycle is scheduled for replacement.
Replacements are made with chrcme-noly materials whenever practical.
['
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Sinole Phase E/C Following the-Surry 'fallure PECo developed a progran to
. detect. single phase E/C damage. Piping systems were selected for inspection based upon review of parameters known to contribute to single phase E/C.
Systens were initially screened using operating temperature. Those systems operating in the. temperature range of high E/C susceptibility were further evaluated based upon bulk velocities'and configuration including' the spacing. between fittings in the overall systen.
A.11st _of the single phase systems included in the Peach Bottom progran is contained in Table 1.
Inspection point selection was primerlly based upon a.
temperature, bulk velocity and systen geometry.
The i
' Initial step in inspection point selection was to rank the systens or subsystems, for potential E/C danage using operating conditions. These system data points vere plotted on a graph which relates velocity and temperature to a predicted E/C rate'for a given geanet ry.
This graph Is_shown in Figure 1. Pipe geometry factors were then applied to the various canponents3 in each systen to prioritize inspection locations.
The final locations selected represent the highest rated components for potential E/C damage. A total of 25 locations were chosen for inspection, b.
Since no baseline thickness data is available for conparison, we Intend to perform inspections during the next two refueling outages in order to establish E/C wear rates.
The inspection frequency for subsequent outages will be determined based upon evaluation of the inspection data and the estimated wear rates.
1 This section is identical to the description provided for c.
two phase flow.
d.
This section is identical to the description provided for two phase flow.
3.
For liculd-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.)
Piping meterial (e.g. chromlun content).
a.
b.
Piping configuration (e.g. fittings less than 10 pipe diameters apart).
4 pH of water in the system (e.g. pH less than 10),
c.
d.
System temperature (e.g. between 190'and 500F).
Fluid bulk velocity (e.g. greater than 10ft/sec.).
e.
f.'
0xygen content in the system (e.'g. oxygen content-less l
than 50 ppb).
i
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.Response
- The evaluation of each parameter listed above in the selection
.~of inspection locations Is discussed below; Piping material composition'can have a significant a..
affect on the E/C rate of a component. Most severe E/C damage has occurred in plain carbon steel piping Small additions of Cr, Cu and Mo can significantly systems.-
reduce.E/C damage of carbon steels. Hcwever, specific chemical analysis information for the systems included in the program for Peach Bottom was not available..
l Therefore, the carbon steel pipe material was considered identical for all system components and was not used for selecting inspection points within a system.
b.
Piping configuration is a important factor contributing to the E/C rate.
The relationship of piping geometries that produce the greatest turbulence also produce the highest'E/C rates.
Pipe component geometry and the spacing between canponents was considered within each system to identify and prioritize Inspection locations, Peach Bottom is a BWR with neutral pH.
As pH levels c.
increase above 0.2, E/C ls reduced.
Since pH was constant throughout the systems evaluated it was not considered for inspection point selection.
j d.
Fluid temperature was considered for rating the pipe systems or subsystems in terms of the predicted E/C rate. Temperature versus E/C rate has a peak between 240 to 300F. The nurter of inspection locations is greater for systems operating in this temperature range.
Fluid bulk velocity coupled with pipe configuration e.
produce turbulent ficw.
Flow In conjunction with temperature determine the E/C rate. Velocity and temperature were used for ranking the pipe systems.
Velocity and pipe gecmetry were used for selecting the Inspection locations within a system.
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The oxygen content of the water strongly affects the LThe data curves'for oxygen i
-E/C rate of. carbon' steel.
content versus E/C rate. vary considerably; hoaever,. the Peach Bottom feedwater oxygen levels'have been historically between 20-30 ppb'which are significantly higher than those reported for Surry (4 ppb).
Since the oxygen levels are reintively constant for the piping systenc
' evaluated,' oxygen was not specifically considered.for selecting Inspection locations.
.4.
Chronologically 'llst and sunnarize the results of all Inspections that have been perfonned, which were specifically conducted for the purpose of. identifying pipe wa111 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.
Belefly descr ibe the inspection' progran and Indicate a.
l whether. It was specifically intended to nrasure wall thickness or whether wall thickness measurements were an incidental detennination.
b.
Describe what piping was examined and hcw Ce.g. describe the inspection instruments, test method, reference thickness, locations examined, neans for locating measurement points in subsequent inspections, Report thickness measurement results and note those c.
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 materi al s.
Resoonse:
A chronological 11 sting of Inspections perforced at Peach Botton is provided in Table 11.
The inspections listed in Table 11 were specifically a.
. intended to neasure well thickness in response to E/C concerns.
b.
A description of the piping inspected is provided In Table II.
All of the inspections were perforned l
utilizing manual UT technt aues. The inspectors were I
Quallfled in accordance with SNT-TC-1A and the procedures prepared by a cualified Level III.
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6-1)
Two Phase In order to maintain repeatability.of thickness measurement
. data,.the inspectton approach has remained unchanged' since 1983.
Most of.the two phase Inspections are performed on small diameter piping.
Each-location is given a unique Identification. Typically there are 4 measurements. per location 90 degrees apart.
Prior to recording the measurements, the entire area is scanned in order.to insure that local areas of wall thinning are being detected.
If an area-is found to'be'below the speelfled thicknesses shown in Table 11, the affected-area is mapped and the minimun value located and recorded.
For the 42 in, dia, turbine crossaround, piping, i nte rnal visual examinations are perfonned in addition to UT thickness measurements.
2).
Sinale Phase Single phase inspections also use manual UT. A specific procedure for scanning and data recording was generated based upon experlence gained from the Surry fallure.
Since these inspections are generally performed on large diameter lines, the scans are concentrated on inspection bands in regions where E/C damage would raast likely occur.
The minimum value detected and the thickness range are recorded.
If an area is found to be below the specified value, the area is mapped, a grid established and the min. value located and recorded.
Thickness measurement results are recorded in Table II.
c.
The miniman wall values are calculated from ANSI B31.1 Par. 104.1.2 plus a corrosion allowance ranging from 0.030" to 0.080" depending on the pipe diameter.
Measurements thicker than these specified values are considered acceptable unless reviews of prior data indicate an extremely high E/C rate.
Those measurements thinner than the specified value require l
engineering evaluation.
l d.
If the engineering evaluation determines that a code min.-wall violation is likely during the next operating cycle, replacement of the piping is scheduled.
Removed l
plpe sections are visually examined to determine if cavitation damage is present; no formal failure analysis f
j is performed. Wherever practical, replacerunts are made
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l-using 1 1/4 Cr-1/2 Mo material.
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7-5.
Describe any plans either for revising the present program or for developing new or additional programs for rionitoring pipe wall thickness.
Responset The Peach Bottrm E/C pepgram provides for the addition or deletion of Inspect 1on areas based upon new infonmtIon.
We intend to perform t he' E.PRI Chexal-Horowitz-Erosion-Corrosion (CHEC) analysis for single phase E/C and will amend our program upon evaluatl.'.of the results, in addition, we Intend to evaluate fincings f rcrn other utl11ty inspections for their applicability to Peach Bottom.
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System Selection Priority Based on Temperature and Velocity (See Figure 1) 4 1
1 1.,
Drain 11ne from 3rd heater to 2nd heater at control valve inlet f
4 reducer.
2.
Condensate piping from 3rd heater to 4th heater.
3.
Condensate piping from 2nd heater to 3rd heater.
1 Drain line from 4th heater to 3rd heater at control valve inle',
4 reducer.
5.
Drain line from 3rd heater to 2nd heater.
I 6.
Condensate piping from 1st heater to 2nd heater.
1 7.
Drain line from 2nd to ist heater at control valve inlet reducer.
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8.
Drain line from 5th to 4th heater at control valve inlet reducer.
9.
Condensate piping from 4th to 5th heater.
10.
Feedwater piping from reactor feed pumps to reactor.
11.
Condensate plplag from 5th heater to reactor feed pump suction.
12.
Condensate piping from drain cooler to ist heater.
13 Moisture separator drain 11nes to control valve.
PRS /pdO6198704 l
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Table 1 Pipe Systens Inspected for Erosion / Corrosion Damage All piping for two phase and single phase flav systens was designed in accordance with ANSI B31.1 1967 except where noted.
Pipe materials are A106 Grade B or A53 Grade B except where noted.
Fitting meterials are A234 WPB or A505 Grade II except where noted.
A.
Two Phase Flav 1,
Main steam crossaround piping between the high pressure turbine exhaust and the moisture separator inlet.
(see note 1).
I 2,
Reactor feed pump recirculation (min.-flow) piping from valves A0-2139/3139A, B and C to the condenser Inlet.
3.
Feedwater long path recirculation piping between orifice R0-2663/3663 and the condenser Inlet.
4 Reactor water clean-up piping between R0-106 and the condenser inlet.
5.
Maln steam drains - neln steam lead drains, rein stop valve above seat drains, high pressure turbine inlet lead drains.
(see note 1) 6.
HPCI steam dralns-HPCI turbine steam supply line drain from steam trap (ST-3) to concenser, HPCI turbine stop valve above seat drain from orifice R0-70A to the drain pot.
1 7.
RCIC steam drains - RCIC turbine steam supply line draln from steam trap (ST-122) to condenr>er, RCIC turbine stop valve above seat drain fran orifice R0-76 to the barometric condenser.
8.
Reactor feed puns turbine steam supply piping drains - steam j
lead, high pressure rain stop valve above seat and below seat, low pressure rain stop valve above seat and below seat drains.
(see note 1) i J
9.
Reactor feed puno turbine first stage and shell drains downstream of valves A0-2557/3557 and A0-2685/3625.
10.
Reactor feed pump leakoff loop seal.
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- 11. Offgas recombiner preheater steam supply drain. _
12.
Extractlon steam 1ines to condenser.
- 13. Feedwater heater vent lines to condenser downstream of orifices R0-2059/3059, 2062/3062, 2068/3068 and 2071/3071.
14 Main turbine 13th stage shell drain.
(see note 1) 15 Any carbon steel relief valve discharge piping where lealtage through the valve is suspected.
16.
Reactor feed pump suct!on side relief valve dlscharge piping dovnstream of valves RV-?l41/3141A, B, C.
B.
Sincle Phase Flcw (Bulk velocities indicated) 1.
Feedwater piping (14-17 feet /sec.).
2.
Condensate piping (10-12 feet /sec.).
3.
Feedwater heater drain piping (4-7 feet /sec.3 4.
Motsture sep&rator drain piping (4-7 feet /sec.).
Note 1 - These piping systems or portions thereof are design in accordance with the turbine renufacturer's proprietary-reculrements.
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COPY PHILAD ELPHI A ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 PHILADELPHIA A. PA.19101 1215) 8415ool
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September 9, 1987 Docket No. 50-352 Mr. W. T. Russell, Administrator U.S. Nuclear Regulatory Conmission Region I Attn: Doctment Control Desk Wash,lngton, DC 20555 Sub.j ect :
Limerick Generating Station, Unit 1 Response to 1.E.Bulletin 87-01 " Thinning of Pipe Walls at Nuclear Power Plants" Mod Request t!5613 NRC Bulletin No. 87-01 dated 7/9/87
Reference:
Attachment:
Limerick Generating Station, Unit 1 Response to NRC I. E. Bulletin No. 87-01 Thinning of Pipe Walls in Nuclear Power Plants Flie:
GOVT 1-1 (Bulletins)
Dear Mr. Russell:
The referenced bulletin requests information regarding utility programs addressing pipe wall thinning due to erosion / corrosion under single and two phase flow conditions.
Philadelphia Electric's response to the five requested actions is provided in the following attachment.
If further information is required, please do not hesitate to contact us.
Sincerely, PRB/pdO8218706 Attachment Copy to: Addressee E. M. Kelly, Senior Resident inspector e-U.S. Nuclear Regulatory Conmiss1on g6-P. D. Box 47 p
Sanatoga, PA 19464
)
Y M.
Distribution:
S. J. Kowalski J. W. Gallagher M. J. Cooney R. H. Logue/W. M. Alden G. M. Leitch M. J. McCormick H. H. Traver R. A. Segletes T. C. Hinkle J. F. Franz, Jr.
L. B. Pyrih J. M. Madara, Jr.
D. R. Helwig A. R. Dioderich G. M. Zalmis P. K. Pavl(des
ATTACHMENT Limerick Generattnq Station Unit 1 Response to NRC 1.E. Bulletin No. 87-01 Thinning of Pipe Walls in Nuclear Power Plants i
The subject NRC Bulletin was generated as a result of the 1986 Surry feedwater pipe break accident.
Licensees were requested to provide the following information concerning their programs for l
nonitoring the wall thickness of pipes in condensate, feedwater, steam, and connected higii energy piping systems, including all safety-related and non-safety-related piping systems fabricated of carbon steel.
information for Limerick Unit 1 in response to I. E.Bulletin 87-01 is provide belav 1.
Identlfy the codes or standards to which the piping was designed and fabricated.
Response
The Limerick, Unit 1 program is under development.
The piping systems presently included in the program scope are listed in Table 1.
The appilcable design code for each systefn is as shown.
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:
Selectir.g points at which to make thickness measurements, a.
b.
Determining how frequently to make thickness measurements.
Selecting the methods used to make thickness c.
measurements.
d.
Making repatr/ replacement decisions.
Resoonse:
The inspection program for Limerick, Unit 1 will address carbon steel piping systems subject to single phase or two phase flow erosion / corrosion (E/C). Each is addressed separately below:
f
'l
_2 Two Phase E/C Development of a program to address E/C.of, carbon steel piping subject to wet steam environments 1s in progress.
. Since 1.imerick, Unit I has completed only one fuel cycle of operation significant E/C damage is not expected.
In '
addition mst of the large diameter piping systems subject-to two phase flow such as extraction steam are fabricated from chrome-rroly materials. We plan to review piping systems uti1Izing experlence galned form-Inspections performed at Peach Bottom and fossil stations in order to identify remaining carbon steel piping potentially affected by E/C damage. The analysis will include review of the system operating parameters and whether there are significant pressure drops which could lead to flashing or cavitation.
Based on this review a program will be developed to nonitor pipe wall thickness'for the identified suspect systems.
The piping inspection points will include locations in a.
the system where there are abrupt changes in the direction of flow (elbows, tees) Immediately downstream of significant pressure drops (orifices, control valves) and at other fittings which cause flow perturbations (reducers, branch connections).
b.
The Inspection frequency for each of ~ the piping systems will be' determined by review of.the prior inspection data. Those systems exhibiting high E/C wear rates will be scheduled for more frequent inspection.
Inspections.wlli utillze ultrasonic: CUT). thickness c.
measurements supplemented by visual examination where practical.
PEco chose UT because it provides accurate verifiable data, Repair / replacement decisions will be based upon review d.
of the inspection data, estimating the erosion rate and All ccmparing it to the design min. wall requirements.
piping below code min. wall or anticipated to encroach on min, wall within the next operating cycle will be scheduled for replacement.
Replacements will be made i
~j with chrcrne-rroly materials whenever practical.
I
Sinale Phase E/C Following the Surry failure PECo developed a program to detect single phase E/C damage. Piping systems were selected for inspection based upon review of parameters known to contribute to single phase E/C.
Systems were initially screened using operating temperature. Those systems operating in the temperature range of high E/C susceptibility were further evaluated based upon bulk velocities and configuration including the spacing between fittings in the overall system.
A list of the single phase systems included in the Limerick, Unit 1 program is contained in Table 1.
Inspection point selection was primarily based upon a.
The temperature, bulk velocity and system geometry.
Initial step in inspection point selection was to rank the systems or subsystems for potentlal E/C damage using operating conditions. These system data points were plotted on a graph which relates velocity and temperature to a predicted E/C rate for a given geometry. This graph is shown in Figure 1. Pipe geometry factors were then applied to the various components in each system to prioritize Inspection locations. The final locations selected represent the highest rated ccmponents for potential E/C damage. A total of 26 locations were chosen.
Since no base 11ne thickness data is available for b.
comparlson, we intend to perform inspections during the next two refueling outages in order to establish E/C wear The inspection frequency for subsequent outages rates.
will be detennined based upon evaluation of the Inspection data and the estimated wear rates.
This section is laentical to the description provided for c.
two phase flow.
This section is identical to the description provided d.
for two phase ficw.
For liquid-phase systems, state specifically whether the 3.
folicwing factors have been considered in estabitshing your criteria for selecting points at which to tronttor piping thickness (Item 2a.)
Piping material (e.g. chrom 1un content).
a.
Piping configuration (e.g. fittings less than 10 pipe b.
diameters apcrt),
pH of water in the system (e.g. pH less than 10).
c.
d.
System temperature fe.g. between 190 and 500F).
1
.4
. Fluid bulk velocity (e.g. greater than 10ft/sec.).
f i
-e.
f
'f.
Oxvgen content in the system (e.g. oxygen content -less than 50 ppb).
Response
-The evaluation of ~each paraceter listed above in the selection of Inspection locations Is discussed belon:
Piping naterial composition can have a significant a.
' affect on the E/C rate of a component.
Most. severe
' E/C danage has occurred. In plain carbon steel piping Small additlons of Cr, Cu and Mo can significantly systems.
reduce E/C damage of carbon steels. However, specific chemical analysis information for the systems included in the program for Linerick, Unit I was not available.
Therefore, the carbon steel pipe meterial was considered identical for all system components and was not used for selecting Inspection points within a system.
b.
Piping configuration is an important factor contributing to the E/C rate. The relationship of piping geometries that produce the greatest turbulence also produce the highest E/C rates. Pipe camponent geanetry and the spacing between components was considered within each systen to identify and prioritize inspection locations.
Limerick, Unit 1 is a BWR with neutral pH.
As pH levels c.
Increase above 9.2, E/C is reduced. Since pH-was constant throughout the systems evaluated it was not considered for inspection point selection.
d.
Fluid temperature was considered for rating the pipe systems or subsystens in terns of the predicted E/C rate. Temperature versus E/C rate has a peak between l
l 240 to 300F. The nunber of inspection locations is greater for systens operating in this temperature range.
Fluid bulk velocity coupled with pipe configuration e.
produce turbulent flow.
Flow in conjunction with temperature detennine the E/C rate. Velocity and temperature were used for ranking the pipe systens.
Velocity and pipe geometry were used for selecting the inspection locations within a system.
l:
f.
The oxygen content of the water strongly affects the E/C rate of carbon steel. The data curves for oxygen content versus E/C rate vary considerably; however, the oxygen levels are relatively constant for the piping systens evaluated; therefore, oxygen was not specifically considered for selecting inspection locations.
o O
Chronologically list and suTmarize the results of all : Inspections
~
that have been performed,.which were specifically conducted for the purpose.of Identifying pipe wall thinning, whether or not pipe veil thinning was. discovered, and any other inspections where pipe wall thinning was discovered even though that was not the-purpose of that inspection.
_Briefly describe the Inspection program and Indicate a.
whether it was specifically Intended.to measure wall thickness or whether wall; thickness measurements were an Incidental determinatten, b.
Describe what piping was examined and how (e.g. describe the inspection Instruments, test method, reference thickness, locations examined,' means for locating measurement points 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 repal r or replacement, including any change of materials.
Response
A chronological listing of Inspections performed at Limerick, Unit i during the first refueling outage is provided in Table II.
The Inspections listed in Table 11 were specifically a.
intended to measure wall thickness in response to E/C concerns.
b.
A description of the piping inspected is provided in Table 11.
All of the Inspections were performed utlllzing manual UT techniques. The inspectorn were quallfled in accordance with SNT-TC-1A and the procedures prepared by a cuallfled Level III.
The inspection results listed in Table II are from single phase flow piping systems. As mentioned previously, the two phase flow inspection program is under develcoment.
Since Limerick, Unit 1 had only been operating for one fuel cycle, the prtrury purpose for performing the inspections was to gather basellne thickness data.
The single phase examinations are generally performed on large diameter lines.
Scans are concentrated on Inspection hands in regions where E/C damage would rest likely The minimtm value detected and the thickness occur.
range are recorded.
If an area is found to be below the specified value, the area is mapped, a grid established and the min. value located and recorded.
Thickness measurement results are recorded in Table II.
c.
The specified minimun wall values are also'11sted, tieasurements thicker than these specified values are considered acceptable. Those measurements thinner than the specified value will require engineering evaluation.
d.
If the engineering evaluation determines that a code min.-wall violation is likely during the next operating cycle, replacement of the piping will be scheduled.
Wherever practical, replacements will be nede using 1 1/4 Cr-1/2 Mo naterial.
5.
Describe any plans either for revising the present program or for developing new or additional programs for nonitoring pipe wall thickness.
Response
The Limerick, Unit 1 E/C program is still under development.
We intend to perform the EPRI Chexal-Horowitz-Erosion-Corrosion (CHEC) analysis for single phase E/C and will anend our program upon evaluation of the results.
In addition, we intend to evaluate findings from other utility inspections for their appilcability to Limerick.
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