ML20049J543
| ML20049J543 | |
| Person / Time | |
|---|---|
| Site: | McGuire  |
| Issue date: | 03/16/1982 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML20049J542 | List: |
| References | |
| PROC-820316, NUDOCS 8203180324 | |
| Download: ML20049J543 (64) | |
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{{#Wiki_filter:- i ATTACHMENT 1 MCGUIRE NUCIEAR STATION MODEL D STEAM GENERATOR OPERATION PROGRAM Introduction In response to the problem of premature fretting wear in Westinghouse Model D steam generators, Duke Power Company has followed a very cautious schedule for - power operation at McGuire. It is known that the rate of wear in the Model D steam generator is greatly increased by operating at high power levels; there-fore, the operating time at power levels of 90% and above has been minimized. This conservative approach in avoiding unnecessary operation at high power levels has been successful in minimizing the amount of tube wall degradation due to wear at McGuire. Duke Power Company and Westinghouse have continued to pursue an aggressive course of action to define the nature and extent of the vibration problem and to identify a satisfactory set of operating limita-tions for Model D steam generators while permanent corrective action is being developed. The purpose of this document is to define the basis for continued power operation at McGuire. It is our intention to operate McGuire at power levels at which steam generator tube wear is minimized, consistent with the calcu-lation contained in this report, and to maintain a substantial safety margin to assure the integrity of the steam generator tubes. The program for establishing safe operating levels for the unmodified Model D steam generators at McGuire is based on the results of the following tasks: 8203180324 820316 PDR ADOCK 05000369 P PDR 1
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- 1. An engineering investigation of the nature of fretting wear in steam generator tubes, including identification of the parameters which have an effect on tube wear rate, and a determination of the relationship between the extent of tube wear and the time of exposure to the environment in which wear occurs.
- 2. Determination of the largest wear defect existing in the McGuire steam generator. The size of this defect is established'from field eddy current information from the McGuire steam generators and comparison with results observed on the tubes removed from Ringhals and Almaraz. Assisting in this effort is an eddy current technique evaluation program sponsored by Duke Power, the results of which are included in this report.
- 3. Determination of the volumetric metal removal rate (wear rate) as a function of power level, based on the operating history of McGuire 1 and the results of task 2.
- 4. Extrapolation of the wear rate information developed in task 3, based on the anticipated operation of McGuire prior to the next inspection,- and selection of the expected amount of wear to be incurred prior to the next inspection. This amount of wear will then be compared to a
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conservatively selected maximum permitted defect.
- 5. Reinspection of the steam generators at the end of the specified operating period.
2
S l The program outlined above, which is based on the principles contained in NRC Regulatory Guides 1.83 and 1.121, is considered by Duke Power Company to be a safe and effective method of ensuring the integrity of the steam generator tubing at McGuire. During this period of operation, we will monitor several sets of instrumenta-tion installed on and inside the steam generator. Data will be recorded from these instruments and analysis of the data will be performed by both Westinghouse and Duke Power. It is not possible at this time to establish the relationship between any instrumentation readings and the onset of tube wear for any types of instrumentation we are using now. We believe that the use of instrumentation results, when interpreted through the use of periodic eddy current examinations and continuing laboratory research, may eventually help to establish a long term operating power level at which tLe rate of tube wear will be. acceptably small. Due to the limited extent of instrumentation, and concerns about its long term reliability, we do not intend to use instrumentation readings as a guide in establishing operating power limitations during the next operating period. Whereas-it confirmed that Model D steam generators will eventually require the installation of some type of modification to permit unrestricted operation at full power, such a modification necessarily requires lengthy ( ielopment time and extensive testing prior to its use. The decision concerning the operating power limitations for the unmodified steam generators is influenced by our concern for avoiding tube degradation which could adversely affect the long term reliability of the steam generators. It is imperative that the maximum 3
r i e i-operating power level at which the tube wear rate is negligible be established during the next period of operation. We expect our proposed program for the next operating period to' accomplish that objective with minimal risk to the long term reliability of the steam generator tubing. 1-4. .{ 4 1 4 4 1 1 l 1 3 ) 4 I t 1 1 j 4 j 4 l
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o Engineering Aspects of Steam Generator Tube Fretting Wear The mechanism of fretting wear between metals in contact has been studied extensively (Reference 1). According to classical wear theory, fretting wear consists of adhesion and metal transfer between the surfaces in contact. If a circulating fluid is available to remove the debris created by the metal tranfer process, then the wear will proceed to affect the two surfaces substantially.if the time of exposure to the wearing environmental is long enough. Since each event of impact can be assumed to remove an average amount of material, the wear rate (volumetric or mass removal rate) is usually modeled as a constant for a given set of critical parameters as discussed below. Therefore the total volume removed by th9 wear process is proportional to the time of exposure to the environment producing the wear. Specific experimental and analytical work has been performed to assess the wear rate for fretting wear of steam generator tubes (References 2, 3, 4, 5). A number of parameters have been identified as being important in determining the wear rate, including:
- 1. Material of the tube and tube support plate,
- 2. Gap between the tube and tube support plate,
- 3. Amplitude and frequency of the tube vibration,
- 4. Preload force which presses the tube against one side of the
! support plate hole, and
- 5. Support plate thickness and hole configuration.
5 l
i Experimental work has been concerned with determining quantitative relationships between wear rate and variations in these parameters (References 2, 4, 5). The principal.results of this experimental work can be summarized as follows:
- 1. The wear rate increases for increased tube to tube support plate gap and for higher support plate reaction forces.
- 2. Wear rates increase as the duration of exposure to the fretting environment increases, particularly for very long durat'an tests. This is because the gap between the tube and the support plates is increased by the metal removal.
- 3. Increases in frequency and amplitude of vibration cause the wear rate to increase.
- 4. Wear rate may be decreased very greatly by increasing the preload with which a tube presses against one side of a support plate hole.
- 5. Wearing tubes produce large amounts of acoustical activity in the steam generator. The absence of rattling in the heat exchanger indicates no tube wear.
From these experimental programs, models have been developed to predict wear rates as a function of the important parameters. One such model (Reference 3), which considered all of these factors is 6
o A A t _c _g W = f (w, D, D, _D , R, -Pg ) where W = weight loss per cycle of vibration w = vibration frequency A /D = non-dimensional vibration amplitude A /D = non-dimensional tube gap t/D = non-dimensional wall thickness R, - Pg = difference between the shear force and preload at the support This model has been shown to give reasonable agreement with data over a wide range of expermiments. Because the model contains the non-dimensional gap, it shows that the wear rate can be expected to change if the diametral gap between the tube and the support plate hole increases as material is removed from the tube. An assessment of the data (2) upon which this model is based reveals that the wear rate would increase about 60% for an change in the tube to tube support plate gap of 40%, as would occur if the gap in the McGuire-steam generators were to increase from the nominal 0.024 inches to 0.034 inches. Another consideration highlighted by this model is the probability of steam generator to steam generator variation in the response to an environment which produces wear. Wear rates are particularly sensitive to the tube preload at the support plate, with a relatively small increase in preload causing an order of magnitude reduction in tube wear rate. For stainless steel tubes, 7
m _ _ O this order of magnitude change occurred due to an increase in preload of about two pounds (Reference 2). Duke Power Company considered this possible varia-bility in their eddy current test program by inspecting 100% of the tube in the first three rows (47, 48 and 49) in all four steam generators.
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The following conclusions may be made concerning the engineering aspects of steam generator tube fretting wear:
- 1. The wear rate is a complex function of a number of variables, but for a given vibration level (i.e. , a given power or feed flow level), the volumetric material removed is proportional to the time of exposure to the environment. causing-the fretting wear.
.1
- 2. If wear progresses a significant amount, such that-the tube to support plate gap increases, the volumetric removal rate will increase. It is essential, therefore, to put substantial margin'into the wear
, calculation. I 8
o
References:
- 1. Engel, P.A., Impact Wear Of Materials, Elsevier Secientific Publishing Company, The Netherlands, 1976.
- 2. Blevins, R.D., " Fretting Wear of Heat Exchanger Tubes, Part I:
Experiments," ASME Journal of Engineering for Power, Volume 101, October 1979, pp. 625-629.
- 3. Blevins, R.D., " Fretting Wear of Heat Exchanger Tubes, Part II: Models,"
ASME Journal of Engineering for Power, Volume 101, October, 1979, pp. 630-633.
- 4. Roger, R.J., and R. J. Pick, " Factors Associated with Support Plate Forces Due to Heat Exchanger Vibratory Contact," Nuclear Engineering and Design, Volume 44, pp. 247-253.
- 5. Ko, P.L., " Experimental Studies of Tube Frettings in Steam Generators and Heat Exchangers," ASME Journal of Pressure Vessel Technology, Volume 101, May, 1979, pp. 125-133.
9
t Determination of Defect Sizes for McGuire The eddy curreny inspection of McGuire revealed that in the 'C' steam generator, there were four eddy current indications which could be classified as the onset of tube wear. These defects are extremely small and are there-fore difficult to characterize accurately for size. It is necessary, there-fore, to make some conservative estimate of what the size of these defects might be so that a wear rate can be calculated. There are two approaches which were used in estimating the size of these defects. The first method involved comparison of the extent of the defect, as determined from eddy current, with the extent of actual defects as determined from the laboratory examination of tubes removed from Ringhals and Almaraz. The second method is a comparison of the eddy current signals observed in the field with those obtained during the eddy current development program performed by Duke Power Company. The axial extent of the four indications in the McGuire steam generator ranges from 0.2 to 0.5 inches as measured by eddy current. This axial extent is shorter than 13 of the 15 defects found on the tubes removed from Ringhals 3. The two tubes with axial extent of indication in the range of 0.2 to 0.5 inches had volumes of 1 x 10~5 and 7 x 105 cubic inches. A similar condition exists for the two tubes removed from Almaraz, where three defects with axial extents less than 0.6 inches had volumes of 5 x 10~5, 3.6 x 10 5, and 4.6 x 106 cubic inches. It can be concluded from this comparison that the axial extent of the indications at McGuire are consistent with defect volumes less than 1 x 10~4 cubic inches. 10 (
Because a normal eddy current probe is symmetric about its axis, eddy current signals contain no readily available information about the circumferential excent of a defect. In an attempt to estimate the circumferential extent of the possible defect represented by the eddy current indications, a technique called template matching was used. This technique takes information from eddy current signals for which the geometry of the corresponding tube wall defect is known and uses that information to draw conclusions about the geometry of the defect associated with another eddy current signal for which actual defect geometry is unknown. This technique was applied to the largest eddy current indication signal of the four found in the C steam generator at McGuire. We conclude that an upper bound for the circumferential extent of the defect associated with the biggest indication is less than 90 . A comparison of this circumferential extent with data on the defects found on the four tubes removed from Ringhals and Almaraz shows that combinations of axial extent less than 0.4 inches (which we have measured relatively accurately from the McGuire data) and circumferential extents less than 90 are consistent with defect volumes of less than 1.0 x 10~4 cubic inches. We also compared this estimated extent of the largest defect in McGuire with defects produced during our eddy current research program. These defects were created by a process called electrodischarge machining which has the advantage of avoiding work hardening of the remaining surface metal. The disadvantage of electrodischarge machining is that the defects are perfectly rectangular and no tapers are present, either in the axial or circumferential directions. Thus, the volume associated with a given through wall depth is greater than 11
that seen for similar defects present on the tubes removed from Almaraz and i Ringhals. Actual small volume defects on the removed tubes have large amounts of taper, both in the axial and circumferential directions, and are more l triangular than rectangular in shape. We have estimated that this effect causes the defects we produce by electrodischarge: machining to have volumes 2 or more times larger than actual defects with similar through wall penetration. A defect produced in the laboratory with an axial extent of .375 inches and a circumferential extent of 90* which was matched by eddy current signal to the biggest of the eddy current indications found in McGuire had a volume approximately 4 x 10 4 cubic inches. Because of the amount by which the volume of the laboratory produced defects overestimates volumes of actual field defects, we conclude that the biggest actual field defect has a volume less than 1 x 104 The final piece of evidence we considered in bounding the possible defect sizes is the fact that only four eddy current indications occurred in only one steam generator at McGuire, with each indication appearing on only one tube at one support plate intersection. If one looks at the eddy current results from Ringhals and Almaraz, it can be seen that the presence of moderate size defects (of volumes greater than 1 x 10~4) is complemented by the presence of multiple smaller defects, many of which were detected by eddy currrent at Ringhals and Almaraz and would have been detected at McGuire. We conclude that the extremely small number of abnormal eddy current signals found at McGuire supports our contention that the associated defects are very small with volumes less than 1 x 104 cubic inches. 12
The tables on the next two pages show a summary of the defects found on the four tubes removed from Ringhals and Almaraz. 13
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I v ALMARAZ TUBE EXAMINATION DATA ALMARAZ l Steam Generator 1 l R49 C74 Max. Depth Eddy Current Vol. of Metal of Penetration Result, % Intersection Renoved (in3) Inch % Field Lab Flow Dist. - - -- NDD -- Baffle Baffle 2. 0 0 0 <20 NDD Baffle 3 9 x 10~# 0.007 16 46 40 Baffle 4 - -- - NDD NDD (window) Baffle 5 1 x 10-3 0.010 23 54 45-50 Baffle 6 1 x 10 -3 0.006 14 60 40 l Baffle 7 - - - NDD NDD - (window) . _ _,, _ _ l Baffle 8 7 x 10 0.007 16 27 25 1 Baffle 9 -- - -- NDD NDD (window) I Baffle 10 5 x 10-5 . 0.002 5 NDD 35 Tube Support 0 0 0 NDD NDD Plate R49 C42 Flow Dist. - - - NDD - baffle BaffTe 2 0 0~ 0 NDD -- Biffle 3 9.7 x 10 0.009 21 43 40 3.8 x 10' -*- Baffle 4 O.009 21 39 . Baffle 5 5.4 x 10-# 0.005 12. 38 <20 Baffle 6 9.0 x 10-# 0 009 2T 47 40 Baffla 7 3.6 x 10- 0.003 7 NDD NDD Baffle 8 4.6 x 10' O.001 2 NDD NDD Baffle 9 0 0 0 NDD NDD Baffle 10 - 0 0 0 NDD HDD t
O Determination of the Maximum Allowable Defect In order to extrapolate wear rates and identify and operating program for McGuire, it is necessary to determine the maximum allowable defect which would be acceptable. There are three considerations used in making this determination.
- 1. Based on the tube plugging criteria contained in the McGuire Technical Specifications, any defects created by the operation of McGuire will.not become large enough to be a pluggable indication.
- 2. Because of uncertainty in the methods and models used, substential margin should be included. This margin should also take into account any possible increases in the wear rate which might occur due to the onset of wear and the increase in the diametral gap between tube and support plate.
- 3. The maximum through wall penetration corresponding to the maximum allowable defect size should be predictable and small. The actual defects found on the tubes removed from Ringhals and Almaraz should be used a guide in relating defect volume and through wall penetration.
On the basis of the criteria above, the maximum allowable defect size was selected as 1 x 10~3 cubic inches. This size is substantially less than moderate defects found in Ringhals and Almaraz - for example, defects which penetrated 30-50% through wall were four to seven times larger than 1 x 10 ~3 16
1 i' cubic inches. There were seven defects found on the tubes removed from Ringhals and Almaraz with defect sizes of between-0.9 x 10~3 and I x 10~3 cubic inches; the through wall penetration associated with these defects ranged from 14% to 23%. The anticipated through wall penetration in McGuire due to a defect with a volume of 1 x 10~3 cubic inches can therefore be considered to be less than 25%, providing substantial margin to the plugging limit of 40% and compensating for the uncertainty in the model used for wear. Defects with a volume.around 1-x 103 cubic inches have been shown to be easily detectable and conservatively sizable by the eddy current techniques used at McGuire. McGuire Operating History At the time McGuire was shutdown on February 26, 1982, the unit had accumulated the following operating history. Power Level Hours at or above this power level 50% 1500 75% 324 90% 72 100?. 23 i The total number of effective full power hours on the reactor core was 1093. i 17
o. Calculation of Wear Rates for McGuire The following assumptions are used to calculate wear rate as a' function of power level at McGuire.
- 1. For a given power level, the wear rates is based on the assumption that all wear occurs at or above that power level. This is a conservative assumption because it allows no credit for wear which may have taken place at lower power levels.
- 2. The wear rate at each power level is calculated based on the number of hours at. or above that power level, but no credit is taken for the fact that the wear rate is_ greater during the. hours above the given power level. For example, of the 324 hours at or above 75%, 72 of those hours were at or above 90%, but the wear rate calculation assumes that the wear rate did not increase as power went above 75%. This tends to overestimate the wear rate at 75% power.
- 3. In combining wear rates for operation at different power levels, wear amounts are calculated independently.
The following table summarizes the calculated wear rates for each power level and gives the number of allowable hours of operation at each power level which corresponds to the maximum allowable defect. 18
I Power Level Wear rate ( ) Allowable hours 50% 1 x 107 1 x 104 75% 4.63 x 107 2.16 x 103 90% 2.08 x 108 480 100% 6.52 x 108 153 19
y Analysis and Discussion of Margins. The. calculated wear rates, and the allowable operating intervals which were derived based on these rates, are considered by Duke Power Company to-be extremely conservative models of the actual wear process inLthe McGuire steam generators. The extent of wear which we expect to result from our proposed operation prior to the next steam generator inspection is most probably much less than we have shown in this calculation. The following are examples of the types of margins we have used in arriving at our position:
- 1. The field eddy current _results from Ringhals and Almaraz, and our own i work performed in support of our eddy current test program for McGuire, establish that largest defect of the four seen in the C steam generator at McGuire has a volume smaller than 1 x 104 cubic inches. However, we f
have chosen a defect size of 1.5 x 104 cubic inches, 50% bigger than the upper bound we established by eddy current for the actual defects, upon which to base our wear calculation and our proposed operating intervals.
- 2. The largest defect permitted to result during the next period of operation at power is l.0 x 10 ~3 cubic inches. This corresponds to a i through wall penetration of less than 25% based on a number of actual.
defects found on tubes removed from Almaraz and Ringhals 3. This amount j of through wall penetration is less than the 40% plugging criteria in the
- McGuire Technical Specifications and only one-half of the 50% plugging j criteria developed by Westinghouse for Ringhals and Almaraz based on 4
4 20
first testing of tubes with similar defects. The defect size limit of I x 103 cubic inches selected as a limit for McGuire can be compared to the actual sizes of defects found on the removed tubes from Ringhals and Almarrz. A defect 30% through wall was found to have a volume of.4.5 x 103 cubic inches. A defect 50% through wall had a volume of 7 x 10~3 cubic inches. Thus a 40% through wall defect can be assumed to have an approximate volume of 5.75 x 10~3 cubic inches or about six times larger than for the maximum size limit of 1 x 103 cubic inches. Thus it can be concluded that it will take six times as long for a defect to progress from 23% to 40% through wall as it did to produce the 23% defect originally. Therefore, there is substantial margin contained in the defect size of 1.0 x 103 cubic inches such that safety limits are not in any way challenged by the use of this criteria.
- 3. The posulated wear rate for operation at 75% power was calculated in a very conservative manner. The _324 hours of operation used as a basis for the wear rate calculation contains 72 hours, or more than 20% of the time, at 90% and above. The results of research and literature review show that the wear rate increases substantially as power level increases, but no credit was taken for those 72 hours at 90% and above in determining the wear rate at 75% power. Thus the wear rate calculated for 75% power can be considered an upper bound. Duke Power Company considers it likely that all of the tube wear postulated to be present in the C steam generator at McGuire was caused by our operation at 90% and above. This conclusion is based on the following:
21
1 Consider the largest defect'that was found in Ringhals 3. This defect had a volume of 1.5 x:102 cubic inches.
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If it is assumed that.this amount'of wear was created in that tube only by operation at 90% and above, of which Ringhals 3 had 1640 hours, the linear wear rate may be assumed to be 1.5 x 102 cubic inches = 9.14'x 10 s , cubic inches , 1640 hour i d + T I e j 3 k 22
.e:
o ., A r A If wear proceeds'at.the same rate in McGuire.1 for operation at 90% power and above, 72 hours of operation would produce a defect of a -
,n, (d 72 x 9.14 x 10~8 = 6.59 x 10~4 cubic inches r.
~
Note that_ this defect is substantially larger (by a factor of 6 or more) Ji than the postulated defect size based on evaluation of the eddy. current signals found in the C steam generator at McGuire 1. It is, therefore, a t reasonable assumption that the indications seen at McGuire were the result of the short period of operation at and above 90% power. Further evidence is given by the results of the eddy current inspection performed at-McGuire in early December, 1981, after over 100 hours of operation at 75% power, during which all steam generators were found to be completely free of indications of wear. Because it is most likely that even short periods of operation at 90% and above have the potential to cause wear of the steam generator tubes, 75% is'the highest power level at which we intend to operate during the next period of operation at power. 22 a
l Other Considerations l l
- 1. Loose Parts l
During this outage, tasks were performed inside the steam generators which necessitated the temporary introduction of various tools and equipment into the steam generator. Administrative controls are in l l t effect to assure that all material taken into a steam generator is either 1 installed or removed at the completion of the work. In addition to the checks done by those individuals performing or supervising the work, a l separate QA inspection is performed as part of final closcout of the steam generators. Every effort is made to prevent leaving any items inside a generator which could become a loose part and subsequently cause damage to the internal structures of the steam generator.
- 2. ALARA Duke's program of power operation followed by eddy current testing has the benefit of assessing the integrity of the tubes and their acceptability for safe, future service. On the other hand, this eddy current testing (and for the current outage, internal instrumentation 1
installation) does result in increased radiation exposure to station personnel and other workers. The projected person-REM dose commitment for the ECT is 1.5 person-REM per steam generator for a total of 6.0 person-REM. For the internal instritmentation installation in the "A" steam generator the estimate is 3.2 person-REM. When these dose 23
commitments are compared to the benefit attained from operation of the unit, the dose commitments are readily justifiable.
- 3. Procedure Review Duke Power Company has reviewed the McGuire Steam Generator Tube Rupture Procedure in light of the recent event at Ginna. In particular, the sequence of events for the Ginna. In particular, the sequence of events for the Ginna transient was reviewed and an assessment of the adequacy of the McGuire procedure was made in light of this event. The conclusion was that the McGuire procedure would have adequately handled the event.
There were several areas noted where clarifications / improvements would be helpful; however, it was determined that no changes should be made in the procedure until completion of the generic review of the Tube Rupture Guideline by the Westinghouse Owners Group Procedure Subcommittee. 4 Shutdown Criteria l The McGuire-Unit I steam generators have various acoustic and vibration monitoring instrumentation installed on an in them. As noted elsewhere in this report, these instruments are primarily intended to be used for off-line diagnostic purposes, not for use in making real time operational decisions related to tube vibration phenomena. The criteria that would be used to assess the need for plant shutdown are the existing Limiting Conditions for Operation in the Technical Specification, namely the 24 l 1
O criteria that limits primary to secondary leakage thrsugh all steam generators to a total of 1 gpm and 500 gpd (.35 gpm) through any one i steam generator. It should be noted that with the proposed operation plan, the potential 1 for tube wear which would result in any leakage is virtually nonexistent. Conclusions
- 1. The four eddy current indications seen in the 'C' steam generator are likely to be evidence of the onset of fretting wear due to flow induced vibration of the steam generator tubes. If there are actual defects present, they are extremely small (volumes less than 1 x 10~4 cubic inches). The fact that only four tubes were affected in one steam t
generator, and that all other steam generators showed no evidence of tube wear, supports the conclusion that our previous period of operation was at the threshold of the point at which tube wear begins.
- 2. Based on conservative calculations of tube wear rate, and allowing for a maximum defect size which is substantially smaller than a defect which would cause any concern for the integrity of the steam generator tubing, a program for at power operation of the McGuire I steam generators has been defined. This program permits power operation at 75%, but not t
t higher, for a relatively short period of time prior to the next steam generator inspection.
- 3. Several different sets of instrumentation will be used to monitor steam generator acoustic and vibratory response during the next period of 25
operation. The results of the analysis of data from these instruments, when combined with the results of the next eddy current inspection of the steam generators, may give us additional insight into the nature of the flow induced vibration problem in the McGuire 1 steam generators. At this time, there is insufficient information available on the effective-ness and reliability of this instrumentation to permit its use in on-line monitoring of the steam generator performance.
- 4. It is our intention to avoid steam generator tube degradation in McGuire I which would interfere with the long term operability and reliability of the steam generators. In performing the calculations contained in this report, and arriving at the conclusion that the next operating period would be at 75% power, we have included substantial amounts of margin and made very conservative assumptions. It is our conclusion that tube wear produced during the next operating period will be so small as to be unmeasurable, and not even approach the maximum allowable size which we used as a basis for the calculation. We have concluded that the risks associated with our proposed operating program are acceptably small, and the steam generator short term and long term integrity and reliability will be unaffected during the next operating period.
26
ATTACHMENT 2 I. INTRODUCTION A. Problem Description The details of the preheater wear phenomena are presented in the section of this submittal covering wear rates and power escalation. Related to ! i eddy current testing three characteristics of the defects are important.
- 1. Complete absence of cold work in the wear area.
- 2. Physical dimensions of defect (i.e. length, circumferential extent, depth, and volume).
- 3. Location of defects relative to the tube support plates.
i i These aspects, as well as the overall problem of defect detection and sizing, are addressed in the ongoing program described below. B. Program and Objectives The eddy current testing (ECT) program was a two phase program utilizing both laboratory and field testing.
- 1. Laboratory Program A matrix of known defects was constructed. This matrix is shown in 1
i Table 1. The size of the defects in the matrix span the range from those not reliably detectable to those well in excess of the detect-tability limits. In addition comparison of Tables 1, 2 and 3 shows
- that the artificial defects closely approximate the volumes found in the field specimens. Only one field defect was smaller than the smallest laboratory defect. The effects of defect physical dimen-sions on the detectability and sizing were investigated. Several frequency combinations and different techniques were evaluated, in-cluding
i.
r-l 1. 200khz - 400 khz differential mixed outputs. l j 2. 130khz - 550 khz differential mixed outputs. l ' l
- 3. 100 - 300 khz absolute mixed outputs.
The important results of the test program are summarized in Appendix I. I 2. Field Program l ~ l The Duke Power Company field testing program covered two aspects. l l First, the results of the ECT at the two Westinghouse facilities ! exhibiting wear were reviewed and evaluated.- The results of this l ! effort are presented in Section III.A. Second, a testing program l for the McGuire steam generators was developed. This program was based partially on the laboratory program and partially on testing. results from other facilities. The McGuire program is presented in Section III.B. I l l l l r. l-
II. LABORATORY RESULTS AND DISCUSSION A. Detectability Since there was little experience with the type defects observed the limits of detectability were not well defined. In order to assess these limits, a range of defect depths from 2.5% to 20% through wall (TW) was tested. Some of the results of this testing are presented in Figures 1 through 3. Each figure includes the raw eddy current defect signal with the support plate and the results of the 200khz - 400khz mix. The mix eliminates the support plate signal leaving the defect signal for eval-uation. Figure 4 is the ASME calibration standard taken at the same instrument settings as the mixed signals. Comparison of figures 1-4 shows that distortion of the support plate signal caused by the 5% and 10% TW defects is readily observed. However, the 2.5% through wall defect caused little or no distortion. A comparison of the 200khz/400khz mix output shows similar results (Figures Ib, 2b, 3b). The presence of a defect is readily observed for the 5% and 10% TW defects but not for the 2.5% TW when the circumferen-tial extent of the defect is less than approximately 60 . From these comparisons it was concluded that under laboratory conditions 5% TW defect similar to actual wear defects could be reliably detected. In trans-lating this detection limit from laboratory conditions to field conditions several factors cause a degradation in the threshold. Based on the experience of those involved, it is concluded that in the field a 10% TW defect can be reliably detected. This conclusion is supported by a review of the field data and will be discussed later (Section III.A).
The detection limit for eddy current is as much a function of volume of the defect as through wall depth. This can be seen by comparing the results of laboratory ECT's of defects with the same TW depth but different dimensions, particularly the 2.5% TW defects: 1.e., the .375 x 180* is detectable under most conditions, while, as noted above, the
.375 x 30 is not. (Figures 1, 2 and 3) Therefore a more important threshold for consideration is the minimum detectable volume. Based upon the laboratory results a minimum detectable volume is between 5 x
- ~
10 5 and 1 x 10 4 in 3 (Figure 1, Defect B and C). This result will be compared with the minimum detectable volume based on field results (Section III.A.). Two differential mixing approaches are currently used to evaluate the wear type defects, 200khz/400khz and 130khz/550khz. In order to deter-mine whether one of these mixes was more suitable for detecting wear defects, a series of tests was conducted. It was felt that the 200/ 400khz mix offered advantages in that tube I.D. noise effects would be reduced and defect signals would be rotated off the horizontal, enhanc-ing detectability. This I.D. noise results in a noise signal in the horizontal direction. Figures 5a through Sc show a series of differen-tial support plate signals and a wobble signal at several frequencies. The wobble signal is comparable to the I.D. noi;e signal referenced" above. It can be seen that the sensitivity to tube I.D. noise increases with increasing frequency. The defects expected in the initial stages of wear have small TW penetration and their phase angles approach the horizontal direction. As the frequency increases, the phase angle of a
given small TW penetration defect rotates further toward the horizontal direction (Figure 6a, b). Small TW defects at 500khz and 600khz are almost in the horizontal direction, therefore the horizontal I.D. noise signal will be difficult to separate from the small amplitude, small TW defect signals. A similar series of tests was conducted utilizing the absolute coil. The results are the same and are presented in Figures 7a, b and 8a, b. Based on these tests the 200khz/400khz differential 4 mix and 100khz/300khz absolute mix were chosen for field testing. For these frequencies the defect signal is rotated off the horizontal, again i enhancing detectability. The absolute coils were evaluated with respect to detectability. Since it was concluded that the differential coil offered a suitable threshold for detectability, extensive testing in this area was not conducted. It ~ i is known that the absolute coil offers a significant advantage in detecting and characterizing tapered defects, therefore the 100khz/300khz absolute examination has been included as part of the field tests at McGuire Nuclear Station (Section III.B.).
- 8. Sizing of Defects
- 1. Depth The accurate estimation of defect TW penetration using ECT results has proven to be difficult, usually resulting in some error. Figure 9 shows the predicted TW depth of the laboratory
- sample versus the actual depth, utilizing the 200khz/400khz i
mix. Two conclusions can be drawn from this comparison. For small volume defects of the simulated wear type there is significant conservatism in the ECT predictions with respect to TW depth. 1
l The ereor is systematic: i.e., higher at lower TW depths.
- 2. Volume Figure 10 presents a plot of the defect amplitude versus volume. This data can be fitted using a linear regression technique. The equation for this fit is shown on Figure 10.
The value of the correlation coefficient suggests a reasonable relationship between volume and amplitude. This data will be utilized later in estimating the volume of Field Defects (Section III.B.).
III. FIELD TESTING RESULTS AND DISCUSSION A. Almaraz/Ringhals Pulled Tube Eddy Current
- 1. Sizing The results of ECT conducted on four tubes removed from Almaraz and Ringhals steam generators were evaluated. This review included both the in-field and laboratory ECT results. ECT predictions on these tubes were based primarily on the 130khz/550khz mix. Figure 11 is a plot of the predicted TW penetration for the pulled tubes using in-field ECT results. Figure 12 is the same plot using laboratory results. The difference in the graphs is due to the absence of the support plates in the laboratory examination. From these plots three conclusions can be drawn.
- The ECT predictions are conservative for both the field and laboratory test with respect to TW depth.
- The error is systematic.
- The presence of the support plate increases the overpredic-tion (i.e. the conservation) in the TW depth.
These field resuits are supported by the laboratory results presented earlier.
- 2. Detection Limit From Field Data A minimum detectable volume and TW depth has been determined from the pulled tube ECT. In order to determine minimum detectable volume based on field data, Figure 13 is used. This figure was constructed using the information in Tables 2 and 3. To' construct Figure 13, detection of a defect was assigned the value of one on
'the Y-axis, non-detection (i.e., NDD on the tables) is assigned a
value of zero. Using this criteria, all defects are plotted versus
~
volume. From this plot, a min' mum detectable volume of 1 x 10 4 in3 can be determined. Figure 14 presents the defect volume from Tables 2 and 3 plotted versus dctual depth. Entering this graph with minimum field detected volume shows the minimum field detected TW depth to be approximately 8%. This result agrees favorably with the results generated in the laboratory (i.e. , minimum reliably detected of 10%TW (Section II.A). B. McGuire ECT Results and Discussion
- 1. McGuire 1 Previous Testing The McGuire testing program included ECT after power operation at the 50% and 75% power level. The current ECT program was conducted af ter operation at 50% power with several days at 90% and100%
power. The details of the operating schedule are discussed in the section covering wear rates and power escalation. The results of the October and December inspections showed no wear type indications present in the "A" generator.
- 2. March, 1982 ECT Results In March, 1982, all McGuire steam generators were inspected. The program consisted of a 200khz/400khz differential coil examination plus 100khz/300khz absolute coil examination.
- 3. "A" Steam Generator Results A total of 10 tubes with mildly distorted support plates were observed in the "A" Steam Generator. An example of these distor- )
1 tions is shown in Figure 15. These distortions were not observed in any other unit. Both the B&W signal subtraction. technique and 1 l
the 200khz/400khz mix were used in an attempt to size the indica-tions. Both of these techniques indicated no through wall penetra-tion. Since absolutely no TW depth could be measured, these indica-tions have been characterized only as distorted signals. They have been noted for future inspections.
- 4. "C" Steam Generator Results Four tubes with 0.0. defects were observed in the "C" steam generator. The eddy current signals are shown in Figures 16 and
- 17. All defects have been characterized as small volume 0.D., less than 20% TW depth defects at the fifth tube su'pport plate. A detailed characterization is shown in Table 4. Since typical calibration curves have no defects below 20% TW depth, it is diffi-cult to accurately predict TW penetration below this depth. Based on signal characteristics, it is estimated that the through wall depth is between 5 and 10% TW (.002" .005").
- 5. Volume Determination Since the volume of the defects is an extremely important parameter in calculating wear rates, several methods were used to estimate it.
" Template Matching": This technique uses known laboratory defect samples to genera te distorted support plate signals which closely approximate the actual field distorted support plate signals. The parameters varied to obtain signals are:
- a. Defect and support plate edge, relative position
- b. Volume of defect j l
j
- c. Shape of defects: 1.e., length, width, and depth The results of this technique are shown in Figure 18. This figure can be compared to the signal for tube 49-75 (Figure 16a). As can be seen, the support plate entrance and exit lobes ae somewhat similar. In addition, the defect signal magnitudes are comparable. It is felt that the difference in the loop opening between the actual defect signal and the simulated signal is due to defect tapering and length differences.
- Volume vs. Amplitude Plot: This technique uses laboratory or field generated volume versus amplitude curves to obtain the estimated volume of a field defect. The volume versus amplitude curve for simulated wear defects is shown in Figure 10. Figure 10a shows the volume versus amplitude curve for the defects on tubes removed from service.
- The volume of the McGuire defects can be estimated using Almaraz and Ringhals dimension data. The maximum length of the McGuire "C" steam generator defects is estimated to be no larger than
.4 inches. Using Figure 19, which presents a dimensional analysis of tubes pulled from Almaraz and Ringhals steam generators (length vs. actual depth and circumferential extent versus actual depth), allows an estimation of circumferential extent and defect depth. From this data the estimated volume is calculated to be 4 x 10 4 in3 The volumes resulting from all of the above tech-niques are shown in Table 5, ranging from 3 x 10 4 to 8 x 10'4 in3 The characteristics of the McGuire 1, "C" steam generator indications indicate that they are small volume, probably near
the limits of detection. It is felt that the highest calculated
~
volume: 1.e., 8 x 10 4 in3, represents an upper bound. To quantify how far below this upper bound the actual defect volumes lie is extremely difficult. However, best estimates would indi-cate that the actual McGuire 1 defect volumes are near the theor-
~
etical limit of detection of approximately 1 x 10 4 in3 I
IV.
SUMMARY
/ CONCLUSIONS
- 1. Differential coil examinations can provide adequate detectability.
- 2. A 10% through wall defect.can be reliably detected in the field. This threshold is strongly dependent on the defect volume. However, field defects with 10% through wall penetration have more than sufficient volume to allow reliable detection.
~ ~
- 3. A minimum detectable volume is between 5 x 10 5 and 1 x 10 4 in3
- 4. Defects with minimum detectable through wall penetration cannot be accurately sized.
- 5. Eddy current sizing techniques for small volume defects provide considerable conservatism i.e. , over prediction of depth.
- 6. The 200/400 KHZ mix provides better sensitivity to shallow defects than the 130/550 KHZ mix in the presence of ID noise such as that experienced in the field.
- 7. The McGuire I, "C" Steam Generator defects are of the fretting / wear type seen at other units.
- 8. The McGuire I, "C" Steam Generator indications are extremely shallow, probably on the order of 5% to 10% through wall.
h
~
- 9. The volume of these defects is near the detection threshold of 1 x 10 4 in3 f
I I
Table 1 Defect Matrix - Volumes (lN) Thru Wall (%) Depth (IN) Width (IN) x Circ (*) Width (IN) x Circ ( ) Width (IN) x Circ ( ) Width (IN) x Circ ( ) t
.75" x 30* 75" x 60* .75" x .90* l 75" x 180 2.5% !.001" 7.4 x 10 -5 1.5 x 10 ~4 2.2 x 10' 4.4 x 10'4 51 .002" 2.9 x 10'4 5.9 x 10I 8.8 x 10 ~4 1.8 x 10 -3 10% 004" 5.9 x 10 ~4 1.2 x 10' 1.8 x 10' 3.5 x 10' 15% .006" 8.8 x 10I 1.8 x 10 -3 2.6 x 10 -3 l 5.3 x 10'3 1
20% .008" 1.2 x lo- 2.3 x 10' -3 ~3 3.5 x 10 {7.0x10 2.9 x 10 -3 -3 25% .010" 1.5 x 10' 4.4 x 10 8.7 x 10'
! .375" x 30 .375" x 60 .375" x 90 .375" x 180 2.5% .001" 3.7 x 10 -5 7.4 x 10 -5 1.1 x 10 -4 2.2 x 10 -4 I
5% .002" 1.5 x 10 -4 2.9 x 10'4 4.4 x 10 -4
, 8.8 x 10
-4 10% .004" ! 2.9 x 10 -4 5.9 x 10'4 8.8 x 10
-4 l1.8x10' 15; .006" l4.4x10 8.8 x 10I i 1.3 x 10 -3 , 2.6 x 10 -3 1
20; .008" i 5.8 x 10I 1.2 x 10 ~3 1.8 x 10 -3 I3.5x10'3 25; .010" 7.3 x 10' l.5 x 10
-3 -3 ,! 4 .4 x 10 -3 2.2 x 10
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' TABLE 3 - AtJ!ARAZ TUBE EUNINATION CATA AutARAZ l Steam Generator 1 .
Max. Depth Eddy Current R49 C74 Result, % Vol . of Metal of Penetration Intersection _ Renoved (in3 ) Inch % Field Lab Flow Dist- ' - - - fiDD -- Baffle Baffle 2. , 0 0 0 <20 tiDD Baffle 3 9 x 10 0.007 16 46 40 Baffle 4 - -- - fiDD fiDD (window) Baffle 5 1 x 10-3 0.010 23 54 45-50
-3 Baffle 6 1 x 10 0.005 14 60 40 Baffle T - - -
IIDD tiDD. (win::w) ,, _ _ BaMie B 7 x 10 4 0.007 T6 27 - 25 . Ba Mle 9 -- - -- fiDD fiDD (winecw)
-5 Baf5 e 10 5 x 10 . 0.002 5 tiDD 35 Tu h Support 0 0 0 tiDD fiDD Pla:a R49 ??
Flc- Cist -
- - - flDD -
ba.H'. e-Baffia 2 0 0' 0 ?!DD -- Bif le-3 9.7 x 10 0.009 21 43 40 Baffle 4 3.8 x 10 0.009 21 39 Baffle 5 5.4 x 10-' O.005 12. 33 <20 Baffle E 9.0 x 10 -0 0.009 2T 47 40 BaffIe 7 3.6 x: 10- 0.003 7 NDD tlDD Baffle 8 4.6 x 10-6 0.001 2 tiDD tiDD Baffle 9 0 0 0 tiDD tiDD Baffle 10 , 0 0 0 tiDD tiDD _ =
TABLE 4 MCGUIRE I, "C" STEAM GENERATOR TUBE DEFECTS Row / Tube R49 C40 .2 .4 s60 0 .002 .004" (5 - 10%) R19 C41 .2 .4 s60 .002 .004" (5 - 10%) P49 C74 s .4 s60 .002 .004" (5 - 10%) R49 C75 .2 .4 s60 .002 .004" (5 - 10%) b
O Table: 5 MCGUIRE I. STEAM GENERATOR TUBE DEFECT Volume Estimation 3 Technique Volume (in ) Template Match 8 x 10 -4 Volume vs Amplitude 5 x 10 -4 (Laboratory) Volume vs Amplitude 3 x 10 -4 (Pulled tubes)
-4 Dimensional Analysis 4 x 10 (McGuire I. 4 Pulled Tube Data)
A B C D Length (in) x Width ( ) .375 x 180 .375 x 90 .375 x 60* .375 x 30
-4 Volume in 2.2 x 10 1.1 x 10 7.4 x 10 -5 3.7 x 10 -5
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Figure 3
l i l
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I I 1 80% 60% 40% 20% AS/7/6 GrAN-
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. v . ...
y' , , ,,; . , . .s
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f' ' ;' -< I 'T,' 100% z.
'.4'-- , e; [00/300 kh:: Mix
}: :.: '_; l '
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M*1
- <3 v.- -
(Absolute) S'pport Plate i i- '.00/400 kh-
.. ... . , c.
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'.a, y ..- .' - ;, )iff./ Absolute t
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/
4 y 7 _ . . . . _ _ _ . _ . _ . . . _ _ _ _ . . . _ . _ _ ,m. , 100% 80% 60% 40% 20% l
.G E Calibration Standard i
I Figure 4 l
(a) -. 100 kh: 200 kh:
.. 3 1
Y;h i s ..d lAM'g# L"#gf Support Plate Signal endal M
.([ ,
;,' h M
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., s .
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e Figure 5 t
(c) 100 khz 200 kh: p
. i
- d. *s
.< . .i ' c '.j h ,.1;.it '$ yV!' V ' ;91,j,f e,i
- .,..s .
..t Wobble Signal
. . , , , . , - . i $,., . i;.. w..
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(al 100 kh: 200 kh
- i. '4
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i t. l 100% SOS 60% 40; 20% 'Ih' 1005 80% 60% 40% 20% T4 400 kh: 300 kh:
,fR: o k w 1 .
f
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993 800 60% 40% 20% Td ASME Calibration Standard Differential Coil Figure 6
100 kh: 200 kh:
" ^
(a) - -
\' e
;.
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. . k j' W*
, . x . u-s t -
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300 khz 400 kh:
~
(b) A Kb
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500 kh: 6', - Support Plate and hubble Sigrc.1 100-600 kh: Absolute Coil Figurc 7
l Ca) ICc kW ~ - 2co khs . r.Mafg m** . , ,
,.1 m T. M ' '._h; s'
$ , . b'. $
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h kh+__ y.co gqg 100% 60% 20% 1001 60% 20% 80% 40% 80% 40% Sto kka h,
- r.- 4, a
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, - bOC NO ,_
l 100% S0% 60". 400 20% D.' l l ASME Calibration Standard 100 kh: - 600 kh: Absolute l Figure 8
Figure 9 100 Simulated wear Specimens 80 , ( 1 te) 200 x 400 Kh Mix
/ (ASME STD.)
l Eddy Current depth, percent 60- /, o f h'all x ,/
/
40
-r-X
/
x XX X f, 20-- #
/
/
/x
/ -~ ~ ~ ~
2'O 40 ~~50 80 lb0 True depth, percent of h'all
av' ' , Figure 10-g..ec si' ,.o h $.31sc N
~,
.;. w' 4 .. .- .
h-N% ire I Larps6
&feef (L 49 Gen 40) i i
l [ Vo/an6 venus swfAArb l .c A& & a'%y SP rh' ens i t ) I i i ~, i lo yo b {, s3 3 % 4t anaTsM, [_ _ L. . o . h=3 - . = -.
- t Figure 10A.
(r. . b
- 4. .~o 3 x + i.% to 4 j o*
- s
/ +
w. y
,7
. /-
i
/
a - M%)te Z /a29ed 2hfed '
,,.s (Row 4% town 40) '
i i volume ursas Aph;bcle l & M M ds (4 %,ha4) h i i i i l' ** 3' ka G^ kt?.. .; lelw;c % .j
. - - - - , - . . - . ._ -..-..-- _ _._. ..-.. - --- ...-..,- ...- . .-.. . . - _ _ - = - - - - , . , . - - . . - ,
Figure 11 100-- A [' In-plant
,,,? Analysis (Plate)
, (A9tE STD.)
./
80-- Correlation Coefficient p = .88 / y = .69x + 32 - ' x / A Ringhals
/
'3 f ,/ x Almara::
'A Eddy Current 60-- x g O ,'
depth, percent - of wall - z _. _ _. __ _ __ .- - Ringhals Plugging Limit _ _ _ _ __ _ _ 7 X/ x - 40 _____ ,8 1 - - - -- - - -McGuire Plugging Limit
/X X
/ 6 /
/ 6 X
20--
/
/
/
/ , , , . i 50 40 60 80 lb0 True depth, percent of wall
Figure 12 - Ilot Cell lab Analysis (No Plate) (A91E STD.) 80._ ,-
// Ringhals Correlaton Coefficient _- .95 Almaraz y=.73 x+ 25 ' -'
/
Eddy Current g
/
,e f
Depth, % of wall 60__ f
/
/
_ _ . ._,_ _ _ _ ._ _ _ Ringhals Plugging Limit y /
'/ .!
40.. y j X / . /
/
/ gX ,/
20 i i / 1 Y /
~~ ~
20 0 6b 8'O ~10'0~ Tnie Depth, t of wall
. .c a s
e c vi n
,C To oc 9
.c x-4 80 w-to = 25.
- o 4H o =o Y *of h *b
=d
~~
- u. I. <
4 4 4 en 4 c omntoA aIqu2003ag wnurtuTN
- of ,
4 o B
.o 4
'd (4 g.01 <3 <0 7.c l <C d A2TIIQURold uoTaco2ag o o Cl
1 10.: Figure 14 l , . l /. j --l. / Correlation Coefficient = .68 I Best Fit Regression-Line is
/ ' ?
I 'y = .0'49x + 4.64x10 /: { l/
! 1 so'*
/l e /4
/ 1 e-
/ I
/ I M I
' .E ' /
- / I Y lo eg go / I -Data taken from Ringhals
; / l and Almare: pulled tubes i
i e/
- I j
- I 1
./ e xl
*/
j l
.sl
!' ef al
,o
-4 31 Estimate of Minimum..
- --tf a
- ,/ 8 $I Detectable Volume / Depth I
/ l, dl i
m i l
'l 4!
l di i I l I l
,g-r
- I l
l l l l l
- I I
- I l
I i l I I 20 4d 6d $0 ld0 Depth, percent GEE *U
Figure 15 l McGuire I "A" Steam l Generator (a) y 4 Typcial Distort Suppor Plate Signals
?
49-62 14th Distorted ' 1 1 (b) - --
.- < . .~
, '; f40,,
g.3. ,- ' , ' . . .<. ,e '. , . : ..r.. 1,. h* 5.,
- 'if[.[.h' j g#s.y;'. ';. . ,)
49-62 16th Distorted s s* p s., b l fi , - 'L
'1 (- } - R& j'. 's ' *
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200 kh: (Diff.) 200 kh: (Diff.) (a)
~
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- ., w < : :
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- l 'i AW 'l l
'd - .
i l 1 100 kh (Absolute) 300 kh: (Absolute) : (b) 400 kh: (Diff. ) 200 klu (Diff.) 1 R49C7f
, .. . - .y . . . . . . , .. , , :w r -
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( , , . 300 kh: (Absolute) 100 kle (Absolute) McGuire I "C" Steam Generator Tube Defects Figure 16
(a) _ 400 khz (Diff.) 200 kh: (Diff.)
. 4 4 h; R49C41 ' 8# @ J ?,7 'I N <, N M '
- 1. ' '... : { . ' .', ' j..y '~ A h '
9 9 *4 i;ezr',, $ 7*. f' K ",';; 3.t l} .*s5 9l Eh' i * ;V.R ';$ a;' h" ? [M E'D
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-i - 4. . , .. e W.
.h, ln, h $' f' ,y 1j $l.$
l l l (b) 100 kh (Absolute) 300 kh: (Aboslute) 400 kh: (Diff.) 200 kh: (Diff.)
..~ y. .'- ;w .2 m< . .. <
> l O,gN:; y-i R49C 7+ 1. 1 " S' A. ". . . . -,/ 'N#t M. M*M:
f' .. .*h_bb kl f.N;,'N,h A$'~'[: '?F ? ff 4~' - >;,, . ..y-N. : ' . . .- ' $ , ':.. ,.;<
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100 kh: (Absolute) 300 kh: (Absolu+e) McGuire I "C" Stea:n Generator Tube Defect Figure 17 t l I
.. . _ .. - - = .
t 1 l i l l I i l I t
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- c. . v. . y,g.-; ; ,
l o . i Q .'.,.a,'... .j' - _. * * 'k .':- ...;. .;..,~, , 'A .
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, - ,,. y 3-(.;;; ,'< ; ;
DEFECT SIGNAL t - y:, - , . . . ,, ...y.
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... ., '..g+'~~_
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i i Figure 18 - Template match for defect on tube R49C75 McGuire Unit I, "C" Steam Generator
- - , : " . . ; s j '
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d
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a W s l - a l s f h g ae o i e n t r ng t _ 9 i ee n 1 R s e rD e e b. e c r r m u ozu f , mt e-p g ret i fr ad un ce , F ame tll. rt
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