ML20151Z046
| ML20151Z046 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 01/31/1986 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML17324A617 | List: |
| References | |
| WCAP-11056, NUDOCS 8602130275 | |
| Download: ML20151Z046 (85) | |
Text
{{#Wiki_filter:_ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ _ WCAP-11056 WESTINGHOUSE HON-PROPRIETARY CLASS 3 NRC PRESENTATION REPORT ON STEAM GENERATOR TUBE INTEGRITY FOR D.C. COOK UNIT 2 JANUARY 1986 I' B602130275 860207 "' PDR ADOCK 05000316
.P PDR
TABLE OF CONTENTS
, NRC PRESENTATION REPORT STEAM GENERATOR TUBE INTEGRITY DC COOK UNIT 2 JANUARY 1986 ,
1.0 RECENT PLANT OPERATING HISTORY OVERVIEW 2.0 INSERVICE INSPECTION RESULTS 2.1 Eddy Current Tube Indication Data e 2.2 Eddy Current Signal Classification 3.0 DESTRdCTIVE EXAMINATION OF DC COOK 2 SG TUBES 3.1 Tube Pull 3.2 Metallography Data - Support Plate Locations 3.3 Metallography Data - Tubesheet Top Locations 3.4 SEM/EOS Analysis of 00 Deposits 3.5 Leak Before Break Characteristics of Multiple SCC 4.0 ECT UNCERTAINTY AND DEGRADATION GROWTH RATE DETERMINATION 5.0 BORIC ACID INHIBITION 6.0 OPERATING INTERVAL MARGIN DETERMINATION 6.1 Structural Integrity Conservatism 6.2 Leak Before Break Verification
- 6.3 Operating Interval Determination 7.0 DC COOK UNIT 2 STEAM GENERATOR SECONDARY WATER CHEMISTRY
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INTRODUCTION n At the request of the NRC staff, on December 4,1985 American Electric Power Service Corporation (AEPSC) presented to the staff a discussion of recent
- 0. C. Cook Unit 2 steam generator issues, and provided justification for continued operation through the end of the current fuel cycle. During the presentation, steam generator tube leaks during July and August, 1985 were reviewed. Actions to re-establish steam generator tube bundle integrity were discussed, and the application of remedial measures was addressed. This report is intended to summarize that' presentation, and has been prepared based on the viewgraphs used by the presenters.
1.0 OVERVIEW OF RECENT PLANT OPERATING HISTORY
'D. C. Cook Unit 2 incorporates a nuclear steam supply system manufactured by Westinghouse, and is licensed for 3411 MWt. Initial criticality was on March 10, 1978. The unit is currently operating in its fifth fuel cycle, with the i
Cycle 6 refueling scheduled to begin in March 1986. At that time, about 5.3 1 effective full power years of operation will have been accrued.
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- 0. C. Cook Unit 2 has four Westinghouse Series 51 steam generators, l illustrated in Figure 1-1. The Series 51 steam generator has 3388 tubes, l
0.815 inch 0.0. by 0.050 inch thick; tubing material is Inconel 600 in the l mill annealed condition. The tubes are hardrolled for a distance of 4 approximately [ ] inches'above the bottom of the tubesheet, leaving an open annular crevice of approximately [ ] # inch depth and [ ]C mil radial gap. Tube support plates are carbon steel with drilled tube holes having a radial clearance of approximately [ ]# mils, i From start-up until November 1983, there were no indications of secondary side corrosion except for minor tube denting at the hot leg tubesheet surface. The only significant tube degradation experienced during that time was primary side cracking of the Row 1 U-bends; preventative plugging of all Row 1 9374Q:10/012786 Page 1
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l l tubes resolved this issue. The other, although minor, degradation mechanism noted during the first five calendar years was wear at anti-vibration bar (AV8) intersections; the total number of tubes involved is small, and subsequent inspections have shown little if any growth rate on tubes with previous AVB wear. The first significant indication of secondary side corrosion on D. C. Cook 1 Unit 2 came in November 1983. During start-up on November 7,1983 following an outage to plug Row 1 tubes, there were immediate indications of primary-to-secondary leakage in steam generator 21, and the unit was removed from service. The leak rate was measured at 0.293 gpm. Visual inspection of the primary side of the tubesheet under a static head of water showed the hot
~1eg of tube R16C40 to be leaking. Subsequent eddy current testing (ECT) of about 725 tubes in steam generator 21 revealed the defect in R16 C40 to be just above the secondary face of the tubesheet, and indicated two additional tubes with similar tube degradation, R14C40 and R14C41. Intergranular corrosion was assumed to be the degradation mechanism. In addition, ECT of over 500 tubes in S/G 22 was perforned; no degradation was found. The unit was restarted on November 22, 1983, and ran until March 10, 1984 when it was removed from service for refueling.
Steam generator activities during that refueling outage included complete ECT of all four steam generators and removal of sections of seven tubes for metallographic analysis. ECT resulted in plugging 61 tubes due to indications at or just above the tubesheet surface and 5 tubes due to indications in the tubesheet crevice region. Meta 11ography confirmed that degradation was due to intergranular attack / stress corrosion cracking (IGA / SCC), probably caused by a caustic environment. The unit was restarted on July 7, 1984 and ran without steam generator related problems until it was removed from service on July 15, l 1985, with an indicated leak in steam generator 23. Details of that tube leak event and two subsequent leaks were provided in
- letter AEP
- NRC: 0936A, and are summarized below for convenience:
I i ! 9374Q:10/012786 Page 2
- 1. Unit 2 was removed from service July 15, 1985 with a primary to secondary leak of 0.22 gpm. Visual inspection under a static head showed one leaking tube (R16 C56) 1'n steam generator 23. Helium leak detection revealed no other leakage. ECT of the leaking tube revealed an indication approximately one inch below the top of the tubesheet. Additional ECT of a block of 24 tubes around tube R16 C56 revealed tube R15 CSS to have a pluggable indication. Re-analysis of ECT data from 1984 showed tube R15 C55 had a 20 percent through-wall indication that was not identified at the time.
- 2. Unit 2 was restarted on August 2. During stset-up, radiation monitors on the condenser air ejectors and steam generator blowdown samples indicated slight additional leakage in steam generator 23. The unit was again removed from service. ECT of approximately 1500 tubes in the sludge pile region of the tubesheet was conducted. As a result, 35 tubes were plugged. Many of the tubes plugged had no previous indication of degradation. Due to concern over the apparent pervasiveness of IGA / SCC in the tubesheet region, Westinghouse recommended and AEPSC elected to perform a boric acid soak at 30 percent power with [ ]**C
. boron concentration, followed by on-line boric acid addition to maintain a
[ ]"'C # boron concentration. Addition of boric acid was intended to neutralize the alkaline environment and thus possibly slow the rate of IGA / SCC. i
- 3. Unit 2 was again restarted, but on August 23, during a hold at 30 percent power for a boric acid soak, a 0.2 gpm steam generator leak was detected.
All four steam generators were opened and visually inspected under a static head. Two leaking tubes were identified in steam generators 22 and 24.. ECT was expanded to include 100 percent of the tubes in all steam , l generators. Table 1-1 provides a summary of the final results of eody current test indications as tabulated for the hot leg of all four steam generators at DC Cook Unit 2 resulting from the Summer 1985 forced outage. The distribution by size of all indications reported less than 20 percent, as well as those indications reported as greater than 20 percent, distorted indications (DI's) and 1 93740:10/012786 Page 3 l l
t 4 squirrels (SQR's) are separately tabulated . A DI is a signal that the eddy current analyst believes to be an indication, but that is too distorted to quantify. A SQR is considered to be a special class of distorted indication confined to the tubesheet region. Distorted indications and squirrels will be further defined in Section 2.2 of this report. The data is segregated into 4 locations (elevations) 1.e., the support plates, tubesheet crevice region. I tubesheet surface (defined as a location from the tubesheet top extending
. upwards a distance of 6 inches into the free span of a tube), and miscellaneous (AVB intersections, free spans). The number of indications reported at the four elevations of interest are entered in the columns designated as " Percent Indication". The wall penetration ranges are arbitrarily assigned in class widths of 10 percent. Some tubes have multiple indications, but only one indication per tube is tabulated; therefore, totals l reflect actual number of tubes affected.
The plugging criteria implemented by AEPSC are defined by the boundary line within the table and are based on both technical specification requirements and administrative guidelines established by AEPSC. Table 1-1 shows that all . indications within the tubesheet crevice region were plugged. Any indications at the tubesheet surface interpreted as greater than 30 percent through wall,
. as well as 01's were plugged. As a result, a total of 142 tubes were plugged f due to hot leg indications. Of the total, 93 tubes were plugged to comply with technical specification requirements.
1 Indications at the hot leg support plates reported during the August 23, 1985 outage were the first such indications discovered on Unit 2. As the condition of the tubes at the support plate locations could influence future decisions regarding tubesheet region remedial actions. AEPSC elected to remove tube samples to assess the condition of the tubes at the tube support plates. Five
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tubes were removed from steam generator 22. Also, in-situ sludge samples and scrapings from the tubesheet crevice region were collected from the removed tube locations. 1 ~ 9374Q:10/012786 Page 4
I 2.0 INSERVICE INSPECTION RESULTS 2.1 EC Tube Indication Data Tubesheet maps and three dimensional histogram plots provided in Figures 2-1
- l. through 2-19 generated from the Summer 1985 eddy current inspection data ,
i visually demonstrate the condition of the tubes in each DC Cook Unit 2 steam generator. A tubesheet map identifying a composite of distorted indications and percent through wall indications is provided for each steam generator. Tube degradation elevation and row / column location is also identified. As can be observed from the tubesheet maps in Figures 2-1, 2-5, 2-9 and 2-13, the distribution of hot leg indications in each steam generator is random. Tubesheet maps provided. illustrate the distribution of percent quantifiable indications within the hot and cold leg of the tube bundle of each DC Cook Unit 2. steam generator. Also tubesheet maps identifying the locations of I distorted indications in the hot leg of each steam generator are also furnished. .As can be seen from the corresponding t'ubesheet maps, a - significant number of both quantifiable and distorted indications are present 1 in the hot leg side of each steam generator. Specifically, significant number of both quantifiable and distorted indications were identified at hot leg tube support intersections. The majority of the pluggable indications occurred in the crevice region or at the top of the tubesheet. 2 I Data from steam generator 24 can be considered representative of the other steam generators. Figure 2-14 graphically illustrates the indication count for percent indications in steam generator 24 hot leg per tube degradation elevati.on. As can be determined from the three dimension.al histogram plot, quantifiable indications were located up to the sixth tube support plate elevation and that the majority of pluggable indications were located at the top of the tubesheet or in the tubesheet crevice. Table 2-1 provides a summary of percent indications for all elevations in the steam generator 24 hot and cold leg. The distribution by size of all quantifiable indications reported in steam generator 24 hot and cold leg are separately tabulated. The data on the hot leg side of the steam generator is segregated into tubesheet i 9374Q:10/012486 Page 5 i I
i crevice, tubesheet top support plate iocations 1,2,3,4,5 and AVB locations. The data on the steam generator cold leg side is segregated into tubesheet top, tube support plates 1,3,5 and 6. Figure 2-18 graphically illustrates the j pluggable indications discovered in steam generator 24 hot leg. There were no pluggable indications in the cold leg of steam generator 24. Figure 2-19 sununarizes in histogram form the total pluggable indications in all four DC Cook Unit 2 steam generators. 2.2 Eddy Current Signal Classification As noted above, during the course of the Sunener 1985 ECT of the DC Cook Unit 2 steam generator tubes, indications and distorted indications were found in the l tubesheet region and at hot leg support plate intersections. The August 1985 field eddy current inspection was conducted by Westinghouse utilizing both standard bobbin coil and 8XI pancake coil probes. Disposition of indications l discovered during the field eddy current review was based on analysis using l 400 KHz- differential mode data. Field eddy current signal, interpretation resulted in four signal classifications:
- 1. Clear Indications; A signal with unequivocal phase angle measureable at 400 K' H z, confirmed at 100 KHz, greater than 1 volt.
- 2. Distorted Indications (DI's); A signal visible at 400 KHz believed by the interpreter to represent tube degradation but with an unquantifiable phase angle. When reviewing these signals at mixed frequencies, the signals do not necessarily provide the expected correlation to further define the DI's at the support plates as characteristic of tube degradation.
- 3. Souirrel (SQR); A tubesheet crevice region signal whose trace at 400 KHz is complex and phase angle unclear, but whose presence represents change.
These indications have been historically proven to compromise tube wall integrity and have thus been classified as tube degradation. l
- 4. Absolute Drift; Shift in 100 KHz/400 KHz absolute mix Y-axis (+) and X-axis (-) traces suggestive of possible tube degradation while the 400 KHz differential trace is quiet.
9374Q:10/012486 Page 6
Figure 2-20 shows Digital Data Analysis Instrument display screen readouts of typical " clear indications". Interpretation of the Summer 1985 eddy current inspection data using a frequency of 100 KHz- absolute mode suggests that the localized tube degradation in the DC Cook Unit 2 steam generators originates from the tube outer diameter (00). Figure 2-21 shows Digital Data Analysis Instrument display screen readouts of typical distorted indications. Again, as is the case with the " clear
~ indications", Summer 1985 eddy current test data suggests that the origin of the DI's is from the tube OD. Figure 2-22 shows the display of a typical
" squirrel" signal.
Figure 2-23 is a typical eddy current display of absolute mode baseline drif t in the tubesheet region. Absolute mode baseline drif t has been suggested by some analysts to be an indicatian of IGA. 3.0 DESTRUCTIVE EXAMINATION OF DC COOK 2 SG TUBES 3.1 Tube tull Selection As a consequence of the discovery of ECT indications at hot' leg tube support plate intersections. AEPSC elected to assess the condition of the tubes by removing tube samples for destructive testing. Sections of five tubes were selected and removed from steam generator 22 based on field ECT data. One tube selected as a control had no indications; the remaining four had indications in the tubesheet region and/or at support plate intersections. The tubes pulled are listed below: R6 C40 including support plate locations 1,2,3 R7 C38 including support plate locations 1,2,3 R11 C24 including support plate locations 1,2,3 R12 C42 including support plate locations 1,2,3,4,5 ' R18 C77 including support plate locations 1,2,3,4,5 9374Q:10/012786 Page 7
Table 4-1 lists the field eddy current results for these tubes. The destructive examination plan included metallography, tube support plate tube sample burst testing, and analysis of 00 deposits by scanning electron microscope (SEM) and energy-dispersive X-ray spectrometry (EDS). Destructive examination revealed tube support plate and tubesheet top locations contained axial SCC and IGA consistent with caustic crevice corrosion.. Multiple cracking has been observed at the top of the tubesheet and at the tube support plate locations. Tube support plate location !- degradation is distributed in from one to four quadrants of the tube circumference at the respective tube support plate elevations. The tube degradation is composed of short axial cracks with an aspect ratio of less i than [ ] # , the latter being consistent with leak before break i characteristics. All tube support plate SCC was confined to support plate crevices. Support plate burst tests were conducted to further aid in the
. characterization of tube. wall degradation and to determine the structural capability of the DC Cook Unit 2 steam generator tubing Support plate burst tests revealed the burst fracture as being composed of numerous short axial l -. cracks (0.1-0.2 inch in length) with tensile torn ligaments between them. The burst tests also permitted the determination of tube support plate cracking aspect (crack length to depth) ratios. The lowest burst pressure was l
approximately two-thirds that of an undegraded tube. Additionally, the reinforcement of the tube by the support plate was confirmed by burst testing a degraded sample in a support plate " collar". The fracture occurred in the previously undegraded tubing away from the support plate intersection, at an expected undegraded tube burst pressure. 3.2 Metallography Data- Support Plate Locations Table 3-1 provides a summary of the metallographic data for the support plate elevations. An example of the crack morphology is provided in Figure 3-1, a transverse micrograph of tube R18 C77 fifth tube support plate location showing axial SCC and some surface IGA. Figure 3-2 is the SEM f ractography of the burst face of tube R7 C38, at the first tube support plate elevation. The fractograph defines both the IGA corrosion boundary and the locations of the 9374Q:10/012486 Page 8
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' tensile torn ligaments. Figure 3-3 further characterizes the circumferential distribution of axially oriented, multiple SCC, occurring around the steam generator tubes. The depth of the individual SCC varies, with the mean depth significantly less than the maximum. Figure 3-4 is a histogram plot of crack j depth distribution for the first tube support plate location of tube R18 C77 t
of steam generator 22. .The mean crack depth for this sample is approximately 4 half the maximum crack depth found around the circumference (9.6. mils vs. 20.6 mils). 1 3.3 Metallography Data- Tubesheet Top Locations Three of the five top of the tubesheet samples were examined using both j nondestructive and destructive examination techniques; the rest of the tube pulls were archived. For the locations examined, tube degradation was found to be axial SCC and IGA with all degradation remaining at or below the top of the tubesheet. , Table 3-2 provides a sununary of the metallographic data resulting from the tube pull examination of samples at the top of the tubesheet. Figures 3-5 i- through 3-8 are transverse micrographs of the tubesheet top Mcation showing *
-. the occurrence of multiple SCC. Figure 3-8 illustrates a through-wall SCC penetration.
' 3.4 SEM/EOS Analysis of 00 Deposits In an effort to identify the cause of the tube degradation occurring in the DC Cook Unit 2 steam generators, tubesheet top and support plate deposits from 3 of the 5 pulled tubes were taken and analyzed. Table 3-3 provides sunenary data of the composition of selected 00 deposits from steam generator tubes from DC Cook Unit 2. In general, the SEM/EDS analysis of the sludge deposits was inconclusive as to determining whether the source of tube degradation is 2
Caustic attack as 00 deposits gave neutral pH readings. In general, high concentrations of Mg, A1, Si, Ca, Cu were found in addition to base metal cor.stituents of Ni, Cr and Fe. Some analyses also revealed the presence of Na. 9374Q:10/012786 Page 9
4 i f 3.5 Leak Before Break Characteristics As discussed previously an examination of the metallographic sections from the
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i DC Cook Unit 2 steam generators has characterized the morphology of the cracks , to be multiple SCC with some evidence of shallow intergranular penetration. Leak before break verification is based on demonstrating that a single l i through-wall crack leaking at the plant technical specification limit during normal operation would develop prior to a crack reaching the critical axial -l
. length corresponding to burst failure at a pressure equivalent to.the pressure differential resulting from a postulated SLB/FLB event.
j . As metallography revealed, all tube support plate SCC and tubesheet top SCC on the tube samples was of short axial length (0.1-0.2 inch) confined within the ! tube support plate thickness or within the tubesheet crevice. Therefore, tube burst would not be expected to occur as a result of the tube degradation ongoing within the DC Cook Unit 2 steam generators. Table 3-4 provides a sunencry of burst test data f rom the four intersections tested. Conservatively, three of the four tube support plate intersections were burst 4 test without the constraining effect of a tube support plate " collar". As can be seen from Table 3-4, burst pressures approximately [ ]' # times the 4 -- OC Cook Unit 2 normal operating primary-to-secondary pressure dif ferential of I 1430 psid were obtained. Also, the burst test result for the tube intersection where a support plate collar was used to simulate tube support plate restraint burst at a pressure equivalent to an undegraded tube. Figure ! 3-9 graphically illustrates the constraining effect of tube support plate 5 restraint on tube burst strength. Also, Figure 3-10 shows the burst opening ! of the tube tested simulating the constraining offect of the tube support plate collar. The tube burst at a location outside the thickness of the tube support plate. Moreover, it has been observed, based on steam generator axial cracks, that 3 the growth of part through-wall cracks in tubes exhibit a limited aspect ratio
- (crack length to depth ratio) which results in extension through-wall prior to l reaching the SLB/FLB critical crack length. As mentioned previously, burst testing was conducted on tube support plate intersections to determine support plate intersection tube crack aspect ratios. Figure 3-11 provides a plot of 93740
- 10/012786 Page 10
__ _ _ _____ ___._ _ ___. _ _._ _ ____ _ _ _ ___. . _ . _ ..,___._ ,___.._,r , _ .-
crack aspect ratio versus crack penetration. Crack aspect ratio decreases as crack penetration progresses through-wall, which is supportive of leak-before break characteristics. 4.0 ECT UNCERTAINTY ANO DEGRADATION GROWTH RATE DETERMINATION I Table 4-1 provides a compilation of the field eddy current results for the five pulled tubes from the DC' Cook-Unit 2 steam generators. Figure 4-1 furnishes a comparison between field eddy current inspection and tube destructive examination comparison. Figure 4-2 is a plot of crack depth distribution for the first support plate. elevation of tube R18C77 in steam generator 22. As can be determined f rom Figure 4-1, the threshold level of detection for the degradation occurring in the DC Cook Unit 2 steam generators is approximately 40 percent through-wall. As the crack penetration progresses further through-wall, the ECT inspection depth of penetration more closely predicts the actual depth of penetration. For tube samples in which metallography revealed tube degradation in excess of 40 percent, the field eddy current estimates yield an average of [ l8'C percent under-prediction. However, as mentioned above, the amount of under-prediction decreases as the depth of cracking penetration increases. Figure 4-3 illustrates the effect of crack depth versus ECT inspection uncertainty. Pertaining to crack degradation growth rates in the DC Cook Unit 2 steam generators, calculations indicate that SCC progression rate through-wall varies with elevation in the steam generator (as is illustrated in Table 4-2). Tube degradation growth rate-in the tubesheet crevice is greater than the growth rate at the top of the tubesh c et and at the tube support plate level. Overall average degradation rate for all three elevations is approximately 10 percent over 10.5 months of equivalent full power operation. In a direct comparison of 1984 and 1985 ECT data, a conservative calculated crack penetration growth rate of 28 percent per 10.5 ef fective full power months (8 percent per 3 effective full power months) occurred in the tubesheet crevice. 9374Q:10/012486 Page 11 1
In determining a representative SCC progression rate through-wall occurring in the DC Cook Unit 2 steam generators over the 1984/1985 operating interval, several approaches were evaluated by Westinghouse:
- 1. Tubes with quantifiable eddy current signals in 1984 were compared with the corresponding eddy current signals obtained in 1985, with compensation for a [ ] percent tube through-wall detection threshold for SCC and eddy current undersizing due to differences between the inspection standard and the indication crack morphology. '
- 2. Depth estimates were defined by eddy current analysts for a sample of eddy current signals with varying degrees of clarity (including Di's in 1985 and best estimates of difficult-to-quantify data reported in 19'4) 8 and compa red.
- e. Tube support plate intersection eddy current depth estimates for clear, quantifiable eddy current signals in 1984 were compared to corresponding clear, quantifiable 1985 eddy current signal depth estimates.
Of the three methodologies utilized for calculating growth rates listed above, referring to Table 4-2, the first listed above yields the highest growth rate (which is occurring in the tubesheet crevice region). Establishing a detection threshold in determining crack penetration depth results in a more accurate determination of crack penetrations which are not readily detected up to a threshold value with a sizing accuracy improving with increasing crack penetration. The latter characteristic (i.e., eddy current undersizing) biases growth rates to be larger than actual if not accounted for. In determining the expected growth rate for tube wall' crack penetration depth, eddy current undersizing was compensated for by correcting any signal with a sized indication to account for dif ferences between the ASME Code inspection standard and the actual indication crack morphology and, if in the previous inspection no size was reported, the depth of crack penetration was assumed to ' a be at the threshold level of detection of [ J c.e percent through-wall. I i 9374Q:10/012786 Page 12
5.0 SORIC ACID INHIBITION Pertaining to on-line boric acid inhibition, the Westinghouse approach to the
. development of boric acid as an IGA / SCC inhibitor is [
I 1 l j a.c.e AEPSC has currently implemented a program for both boric acid enhanced off-line crevice flushing, boric acid soaks and on-line addition of boric acid as a method to arrest the IGA / SCC tube degradation occurring in the DC Cook Unit 2 steam generators. 9374Q:10/012486 Page 13
6.0 OPERATING INTERVAL MARGIN DETERMINATION 6.1 Structural Integrity Conservatism Minimum wall requirements for the D. C. Cook Unit 2_ steam generator tubing were calculated in accordance with the criteria of USNRC Regulatory Guide 1.121, entitled '8 asis for Plugging Degraded PWR Steam Generator Tubes'. The
! basic requirements consist of:
- 1. Allowable minimum wall determination per the following:
- 1. For nornal plant operation, primary tube stresses are limited such that a margin of safety of 3 is provided against exceeding the ultimate tensile strength of the tube material, and the yield strength of the material is not exceeded, considering normal and upset conditions.
- 2. For accident conditions, the requirements of paragraph N8-3225 of Section III of the Code are to be met.
In addition, it must be demonstrated that applied loads are less than the burst strength of the tubes at operating temperature as determined by testing.
- 3. For all design transients, the cumulative fatigue usage factor must be
- less than unity.
II. Leak Before Break demcastration, i.e., that a single through-wall crack I with a specified leakage limit (technical specification leak rate limit) l during normal operation would not propagate and result in tube rupture during postulated accident condition loadings. In establishing the safe limiting condition of a tube in terms of its remaining wall thickness, the effects of loadings during both the normal operation and postulated accident conditions must be evaluated. [ 9374Q:10/012486 Page 14'
1
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- C # Therefore, item I (3) above need not be addressed for the DC Cook Unit 2 steam generator tubes.
Table 6-1 provides a summary of DC Cook Unit 2 tube properties and operating information utilized in the development of the allowable tube wall loss. In the calculation of tube minimum wall, three distinct areas of tube degradation within the DC Cook Unit 2 steam generators were addressed: tubesheet crevice, tubesheet top ( defined as the area from the very top of the tubesheet on the secondary side extending approximately 6 inches into the f ree span of the tube) and tube support plate intersections. Based on the destructive examination of the five tubes pulled from steam generator 22, the tube minimum wall determination for localized tube degradation occurring at the tube support plate elevations in the DC Cook Unit 2 steam generators assumed:
- 1. Tube degradation to be characterized as multiple SCC, 0.~1- 0.2 inch in axial extent
- 2. Partial through-wall cracking was evaluated as single and multiple cracks.
- 3. As tube support plate degradation was confined to the thickness of the ,
tube support plate, the maximum macrocrack length is equal to support plate thickness or 0.75 inch. I
- 4. Li.nk up of the multiple SCC was considered improbable at postulated accident condition pressure differential as reflected in the pulled tube specimen burst tests. l 9374Q:10/012486 Page 15 l
Likewise, a tube minimum wall determination for localized tube degradation occurring at the tubesheet crevice / top of the tubesheet assumed:
- 1. Tube degradation to be characterized as either multiple SCC or intergranular ' CC S combined with shallower, more widely spread intergranular attack (IGA / SCC).
- 2. Tubesheet crevice / top of the tubesheet tube wall degradation was evaluated as equivalent thinning (as a result of IGA) with a superimposed crack.
- 3. The axial extent of the equivalent thinned length of tube degradation is 1.5 inches. Also, the IGA (equivalent thinning) was uniform around the tube circumference.
Per NUREG/CR-718 " Steam Generator Tube Integrity Program Phase I i Report", uniformly thinned tube around its circumference with an axial extent of 1.5 inches would be expected to have a burst pressure equivalent to an undegraded tube having the same wall thickness and outside diameter as the thinned region of the tube. Results of these calculations are provided in Table 6-2 for each of the above areas of tube degradation. Moreover, Table 6-3 provides a sunenary of minimum wall determination for the three regions of localized tube degradation occurring in the DC Cook Unit 2 steam generators. In each case, the RG 1.121 j criterion for normal operation that primary tube stresses are limited such j that a margin of safety of 3 is provided against exceeding the ultimate tensile stress of the tube material was determined to be the limiting l
' criter. ion for determination of tube minimum wall.
6.2 Leak Before Break Verification As stated in Section 3.4 of this sununary report, the leak before break rationale is to limit the maximum allowable primary-to-secondary leak rate during normal operation such that the associated crack length through which technical specification leakage occurs is less than the critical crack length 9374Q:10/012486 Page 16
corresponding to tube burst at the maximum postulated pressure condition loading (FLB). Thus, on the basis of normal operation, unstable crack growth is not expected to occur in the unlikely event of the limiting accident. Moreover, it has also been demonstrated in Section 3.4 of this report that growth of part through wall cracks exhibit a limited aspect ratio. This characteristic results in crack extension through-wall prior to reaching the SLB/FLB critical crack length (Figure 3-11). For tube support plate intersections, an examination of metallographic sections from steam generator 22 has characterized the morphology of the cracks to be multiple SCC. All tube support plate SCC has been of short axial extent (0.1-0.2 inch) confined within the tube support plate thickness. The single crack length corresponding to the plant technical specification leak rate limit of 0.35 gpm at a normal operating pressure differential is approximately [ ] inch. The critical crack length corresponding to burst during a postulated FLB accident is approximately [ ]a,c.e inch; therefore, a leak before break margin of 52 percent is demonstrated.
.For tubesheet crevice and top of the tubesheet locations, localized tube wall degradatioh occurring either within the sheet tube or at a range of 0 to 6.0 inches above the top of the tubesheet has been characterized through metallography to be either multiple SCC below or a combination of IGA / SCC only above the top of the tubesheet. The superimposed crack length corresponding to a plant technical specification leak rate limit of 0.35 gpm at a normal operating pressure differential for a tube " thinned" uniformly around the
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circumference of a tube 62 percent through-wall with an axial extent of 1.5 inches is approximately [- ]a c.e inch. The critical crack length corresponding to burst during a postulated FLB event is approximately [ ]"_'," # inch; therefore a leak-before-break margin of 25 percent is demonstrated. AEPSC implements a leak rate monitoring program which emphasizes both absolute leak rate level and rate of change. It is important to note that very low leakage rates are detectable by leakage monitoring. This effort further supports the demonstration of tube bundle integrity. 9374Q:10/012486 Page 17
4 2 6.3 .0perating Interval Determination During the operation of a steam generator, the influence of the operating environment may affect some of the tubes and result in localized wall
- f. degradation. As part of.a preventive program to detect tubing wall loss, inservice inspection using eddy current techniques is performed. Affected
- tubes with a wall thickness. greater than the minimum acceptable wall thickness i are acceptable for continued service, provided margin is' added to the minimum
! r'equired tube wall thickness to account for eddy current measurement uncertainty and an operational allowance for continued degradation until the next scheduled inspection. Table 6-4 summarizes expected available safety margin for locally degraded steam generator tubing (per tube elevation) upon completion of Cycle 5 operation of DC Cook Unit 2. The safety margins available upon the completion of the present fuel cycle are based on the maximum permissible wall loss per tube location calculated in accordance with RG 1.121 criteria ([ ] percent for the tubesheet crevice / top of the tubesheet [ ]C percent for tube support plate . location degradation), the established eddy current measurement ' uncertainty for steam generator tube degradation ([ al .c.e j- percent), a growth rate allowance (8 percent for 3 EFPM's) and the remaining 1 operating interval (3 EFPM's). The eddy current measurement uncertainty and crack penetration growth rate allowance utilized in the above safety nergin ! determinations represent conservative allowances based on tube pull metallography results (Section 4.0). 7.0 DC COOK UNIT 2 STEAM GENERATOR SECONDARY WATER CHEMISTRY
.The objective of the maintenance of appropriate water chemistry conditions in the secondary side of PWR' power plants is to minimize the potential for
- corrosion in secondary system components and, in the long term, increase plant availability. The general criteria for establishing secondary water chemistry guidelines to provide chemistry control are as follows
l 4 l , ] 93740:10/012486 Page 18
- 1. The rate of ingress of impurities to the steam generator should be maintained as low as reasonably achievable, and consistent with the best achievable power plant operating practices.
- 2. The impurity concentration limits are the known maximum values which are consistent with the known corrosion behavior of secondary materials.
- 3. .The defined impurity concentration limits are consistent with those concentration ranges detectable by currently available equipment and procedures.
Table 7-1 summarizes the secondary side water chemical specification history for the DC Cook Unit 2 steam generators. Figures 7-1, 7-3 and 7-4 are provided to show specific examples of the more stringent secondary water chemistry control guidelines being implemented, i.e., improvements in impurity concentrations of yearly average dissolved oxygen, yearly average steam generator cation conductivity and steam generator sodium concentrations, respectively. Figure 7-2 represents a histogram plot of main condenser tube pluggage through 1984. Leakage of the arsenical copper condenser tubes was a major contributor to the ingress of impurities into the secondary side. This problem was resolved in 1984 when the~ main condensers were retubed with 304 stainless steel. i 9374Q:10/012486 Page 19 kb
. . = _ - .-
Table 1-1 Final Results of Eddy Current Test Indications j Aug. 1985 Outage DC Cook Unit 2
% Indication (20 d'0-29 35 >, 4 0 Sy DI** Total 0 32 20i .16 142 236 Support Plates 26 N/A Crevice Region 1 . 1 3.
47 13 10 75 2 Tubesheet surface 13 9 14i 30 O .. 7 73 i l e. Miscellaneous 26 21 5 '. O N/A -
~52 Total 66 63 42 93 13 159 436 I
Table 2-1 D. C. Cook Unit 2 Summary of Percent Indications s/G 24 HL (20 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99 Crovice 2 1 3 2 2 1 2 5 l Tubesheet 12 20 18 10 4 2 3 2 1 1 10 8 2 3 2 1 5 5 4 1 3 3 2 1 4 3 5 3 6 - 7 , Allis. I 6 1 2 2 8 i 3 5 3 1 i i t 4 1 3 S/G 24 CL 7tbesheet 2 1 5 2 2 l 3 1 1 i 5 1 i 6 1 , I I i . ._ - _ . _ . . . ._ . _ . , . _ _ _ _ _ _ _ _ _ _ . _ . _ _ . _ . _ _ _ _ _ _ . _ _ , _ _ _ _
._._.m _ . . _ . _ _ . _ . _ _ _ _ _ -. _ _ - . . _ . - . -
Table 3-1 Sumary of Metallographic Data- Support Plate Evaluation 1 'DC Cook Unit 2 Sept. 1985 Tube Pull'
- TUBE LOCATION FIELD TYPE OF MAXIMUM QUANDRANTS OF i E/C DEGRADATION PENETRATION CIRCUMFERENCE
] ) (1) INVOLVED R6040, Control 1st S.P. N.I.R. No Degradation N/A N/A Found ) 3rd S.P. N.I.R. SCC- 20 1/4 l i R7C38 1st S.P. 38% SCC 59 4/4 2nd S.P. N.I.R. SCC 31 2/4 3rd S.P. N.I.R. SCC 25 2/4-i l R11C25 3rd S.P. N.I.R. SCC 30 2/4 1
- R12C42 1st S.P. N.I.R. SCC 20 1/4
) - 1 3rd S.P. N.I.R. SCC 22 1/4 1 ] 5th S.P. N.!.R. SCC & Minor IGA 12 1/4 1 R18077 1st S.P. Distorted Signal SCC 56 1/4 l 2nd S.P. Distorted Signal SCC 52 4/4 3rd S.P. N.I.R. SCC 34 2/4 l , i 4th S.P. N.I.R. SCC 42 2/4 5th S.P. 34% SCC 46 3/4 ,
Table 3-2 Sunwary of Meta 11ographic Data Tubesheet Top E"evation DC Cook Unit 2 Sept. 1985 Tube Pull i FIELD TYPE OF ., , MAXIMUM QUANDRANTS OF TUBE LOCATION E/C DEGRADATION - PENETRATION CIRCUMFERENCE (%) INVOLVED R6C40 O.5 inch below N.I.R. SCC 36 1/4 T/S Top R12C42 T/S Top to 2.1" 82% IGA and SCC 100 2/4 ! Below R18C77 T/S Top N.I.R. SCC 14 1/4 r
.= - . _ . ._.
Composition of selected OD d::pesits fr m etzm Table 3-3 generator tubes from D. C. Cook Unit 2 as determined by SEM/EDS in (%) TUDE PIECE 1.0CA180N AREA No Ms At 51 P S K Cs T1 Cr Mn Fe M1 Cu 2n As Me P' b COMMENTI RISC77 2A2A TTS 1 - 27 1.9 1.4 - - - .1 .4 20.9 - 20.4 47.0 3.2 14 - -
.3 eteen 1 2 - 4.3 3.3 2.4 -
.3 -
.2 .3 7.2 11 49.9 27.9 2.0 11 - -
.1 deposit 3 - 8.0 12.4 14.4 - - -
10 .1 .5 .9 58.5 1.1 .9 - - - 2.0 deposit 4 , 14 4.5 3.8 - - - .3 - 12.5 - 19.4 37.8 34 .4 14.9 .- 1.0 eteen 1/2' below TTS 1 - 7.2 3.9 4.1 -
.2 -
. 3 .4 5.9 - 49.9 22 0 - - -
1.3 1.7 deposit 2 - 7.4 5.2 4.0 *- .9 *
.2 .1 11.4 -
25.7 43.0 - - - - - clean
.1 .8 14.7 4.4 - 7.9 0.0 - - - - - deposit
~1/2* above TTS 1 - 20 4 2.4 34.0 - 2.9 2 9.4 - 2.4 .8 - - - - .4 22.2 -
14.3 45.4 .8 20 - - - clean 49-1 tot op 1
- 4.2 2.4 2.9 - .4 -
14 - 14.1 - 13.9 52.3 3.4 .7 - - - clean 2A - 4.3 3.3 3.0 1.0 - - 23 .4 10.0 - 31.4 30.4 8.4 14 - - 1.9 deposit 2B - 3.4 1.9 2.1 - - - .8 .e 14.7 - 12.0 54.0 4.8 .8 - - 18 eteen 48-1 2nd sp 1 - 84 3.9 14.7 - - - 12 3 .1 - .4 57.3 .3 1.0 - - 13 - deposit i 2 - 23.3 12.9 15.7 - - -
.5 -
4.9 - 15.0 21.4 2.1 .7 - -
.5 clean l
3 9.4 - 1.8 11 -
.1 - .1 .4 21.8 - 15.3 44.1 4.2 10 - - - clean
.8 89.9 2.8 - - - - - deposit 4 - -
3.4 19 - .3 - .3 - .5
- - .5 - 2.5 1.2 39.7 6.8 1.4' 11 - 1.0 - deposit 88-3 3rd op 1 - 21.4 12.1 11.9 -
2 - 25.9 23.2 22.3 - - - .7 - 2.2 14 12.4 54 4.4 .8 - 10 - deposit 3 - e.2 3.9 5.7 - - -
.7 - 12.8 -
23.4 42.4 3.2 .4 - - 15 deposit 4.2 19.9 - - 14.4 - 3.3 - 38.7 9.3 .9 - - 2.3 - deposit 4 - 5.1 - 1.1 20 4.0 - 15.4 20.5 4.5 .4 - - - deposit 105-3 4th op 1 - 24.0 7.7 15.9 - - .2 l 2 - 4.4 .2 20.5 - 3.4 - 42 9 - .4 .4 18.1 3.7 .8 - - - - de' posit 1.4 24.0 9.4 .5 33.0 - .1 .2 22.4 18 .8 - - - - deposit 3 - 4.3 - 4 - 9.7 1.9 2.4 - - - 1.8 .2 14.7 - 10.0 52 4 3.7 13 - - 1.5 clean 5 - 11.4 2.0 4.8 - - - 28 - 14.5 - 10.2 51.0 - - - 2.0 - . clean 1282-A Sth op 1 - 7.0 4.4 2.5 - .2 - .1 .2 14.1 - 11.9 49.0 e.7 17 - - - clean 2 - 24.0 28.4 21.1 2.5 .1 - 20 - 2.5 1.7 8.5 4.1 1.1 4 - - 11 deposit 3 - 14.8 22.3 18.0 .7 - - .8 - .7 1 2 34.9 1.2 1.0 .7 - 1.1 .4 deposit
.1 .2 12.7 -
23.0 36.5 4.3 1.0 - .4 - deposit 4 - 8.7 8.7 4.1 - .4 - 1.2 87.1 .9 3.9 .4 - - - deposit 5 - 3.5 .4 11 - .1 - .8 -
.3 1.1 .2 .7 1 1 e4.5 1.2 15.9 - - - - deposit R4C40 2A2-C TTS 1 - See 2.8 3.7 - - -
2 - 74 5.4 30 .4 - - - .3 15.5 - 8.1 54.4 4.9 - - - clean 3 - - 3.5 4.5 - - - .2 .4 '18.0 - 20.8 44.0 4.0 12 - - 12-. clean 4.9 - - - .2- .4 7.8 a 54.0 15.0 5.1 - - - - deposit 4 - 9.8 2.7 59-3 tot op 1
- 8.4 3.5 2.8 - - - .2 .4 15.4 ,
8.5 53.5 5.9 9 - .2 - clean 4.2 - 7 1.4 34.1 2.7 .5 - - 12 - deposit 2 - 24.7 10.9 17.8 1.5 - - 3 - 20.3 4.1 23.7 - 22 - 5.7 - .8 .8 31.5 4.4 3.9 .e - - - deposit 4 - 5.7 1.4 10.5 - - - .3 .5 14.1 - 9.3 52.3 4.4 - - - 13 clean 5 - 22.8 5.4 20.8 - 3.4 - 3.4 - 1.0 - 28.7 8.9 2.1 .e 1.8 1Bal - derosit 1.8 .3 8.4 - 8.3 20.3 .4 - - - 5.1 deposit 78-3 3rd op 1 - 23.5 9.8 21.8 - - - 6.7 - .5 .4 17.7 1.2 .3 - - 2.0 - deposit 2 - 21.8 11.5 31 7 2.9 2.2 - deposit 3 - 19.0 13.7 32 4 3.5 - - 10.5 - .4 .e 15.0 .7 3 - - 3.9 - 4 - 11.9 8.7 17.0 - - - .4 .3 14.0 - 9.0 31.4 1.2 .3 - - 55 eteen 17 .4 22.3 5.0 .5 - - - - deposit 5 - 28.3 12.4 23.8 19 .8 - 2.4 - I (J N
Table 3-3 Ccmp:siti:n cf cicted OD d:po:its from ctzm (cont) jentrator etermined tubes from D. C. Cook Unit 2 as by SEM/EDS. TUDE PIECE LOCAT198f AREA No Me , At ---- 31 P S K Cs Tl Cr Mn re M1 Cu Zn As Me Pb C(NueENT* 2.9 41 - - -
.tI - 10.5 - 15.1 55.4 - 1 2 (C1) - .4 eteen R12C42 24-2 TTS 1 3 0 (C1) - - eteek below t/s top 14 - - 2.9 9.0 - .5 - .1 - 11.4 - 11.0 41 4 -
2 - 47 4.2 5.5 - - - '.3 - 14.5 - 14.0 47.0 - 1.0 (C1) - 3.3 eteen
- - .2 .2 3.0 - 11.1 55.3 - 3.5 (C1) - - creek 24 - - 3.9 21 9 -
- 11 eteen 3 - - 58 4.4 - - - .3 - 16.0 - 12.8 54 0 - .9 (C1)
- - deposit 4 - 95 4.2 0.4 - 1.1 - .4 .1 5.7 - 25.3 39.3 3.4 2 1 (C1)
- - 3.7 24 2 - $4.0 .4 (C1) - - depeelt 24-4 TTS 1 -
23.1 17 2 15.2 - 9 - .3 See 4.8 .4 (Cil - - deposit above t/s top 2 - 10.0 9.1 13.0 - .5 - 14 - .3 1.3 57.4 deposit 3 - 25.9 29 3 30.3 - 32 - .5 - - 7.2 4.5 - .e .4 1 0 (C1) - 4 - - 4.1 3.3 - - - - - 17.9 - 11.4 57 1 4.3 10 .4 (C1) - deeocit deposit
- - 15 9 - - .5 45.2 .5 1.4 - - - .9 45-4 ist se 1 - 9.4 3.0 22.9 -
deposit 2 - 9.5 4.0 e.5 - - - .0 - 13.1 - 18 8 41 2 31 .4 - - 2.3
- - 12 deposit 3 -
31 9 7.7 24.9 - .5 - 10.5 - - 1 3 39.2 .5 .3 .2 deposit 4 - 14.1 2.4 17.0 - 1.2 - 5.0 - .2 .4 52.9 .e 23 .1 - - -
.3 24 - depeelt
- 5 - 8.0 3.2 19.1 - - - 13 7 - 1.2 . 45.0 32 1.0 -
- - - depeelt 99-4 3rd op 1 -
15.4 13.4 42 1 - - - 28 - .7 1.0 21.9 15 .7 .3
- - 1.0 7.3 .7 .7 - - 25 - deposit 2 - 7.4 0 1 43.0 - - -
29 1
- - .4 - 13.7 - 7.9 52 7 - - - - 2.0 eteen 3* - 11 0 5.4 4.0 -
4 - 19.0 16.4 43.7 = .1 - 70 .2 .3 1.1 8.4 11 .7 .4 - - 1.4 deessit
- - - 1.s 47.0 - 9.4 - - - - deposit 143-3 5th op - 12 6 25 4.2 - - .4 1
441 - - - .7 .2 .3 .7 00.9 .4 35 - - - .4 deessit 2 - 8.1 -
- - - .8 deposit 1.2 - - 1.7 -
3.3 - 24.0 12 4 1.9 3 - 24.4 10.9 14 1 - - #- 2.5 eloon 4 - 7.2 2.7 4.8 - - - .2 - 15.4 - 9.4 57.9 - 35.5 21 0 3.2 - - - .1 depeelt 5 11 0 2 8 14.7 - 1.2 - 34 - 5.4 - f 9 e
+
+
co 0 g
Table 3-4 Burst test data DC Cook Unit 2 Sept 1985 Tube Pull SPECIMEN PURST PRESSURE PURST A D PURST LENGTH / WIDTH (psa3 ( 2,3 4anches/anchesa
=
eeeeeeeeeeee eseeeeeeeeeeeeeee seeeeeeeeeee seeeeee4seeeeeeeeeeeee
... . . . a,c,e
_~ e A tensile t estt.SI of 58.7 of and R7Ci8 an showed uttamatethe 8.070stronglh tensste inch CDof8.952 97.3 inch p.53 wall tube had a yield strenSth 4a
Table 4-1 D. C. COOK UNIT 2 - S.G. 22 1985FIELDECTRESULTS(a) TUBE "SEGENT" TSP's TUBE T.S. T.S. ROW COL _ Q CREVICE TOP 1 '2- 3 4 5 6 40 ----- - --- - -- - - - M I R- - - -- - -- - -- - - - X X 7 38 NIR MIR NIR 38% P NIR X X . 11 25 NIR AD X NIR MIR MIR X X 12- 42 NIR 82 X ---- -- -- - -- N I R- -- ----- - -- 18 77 NIR NIR MIR DI DI NIR NIR 34% (a)=BobbinCoilInspection X = Not Pulled NIR = No Indication Reported P = Possible Indication AD = Drift in Absolute Mode ,'
~~~ *
- e , -p e y.., s. . .
. Table 4-2 D.C. COOK UNIT 2, GROWTH .*04' '85*
METHOD OF LOCATION OF DETERMINATION T.S. CREVICE A80VE T.S. T.S.P.'S MMMMMMMMMMMMMMM MMMMMMMMMM MMMMMMMMM MMMMMM
'8S' '84' COMPARISON 28% 14% -
6% WITH COMPENSATION (69 POINTS) (80 POINTS) (340 POINTS) FOR DETECTION THRESHOLD ~.'"
'8S' '84' COMPARISON -
11% 16% 8% BY FORCING ~ E,CT (S POINTS) (10 POINTS) (36 POINTS) CALLS, S.G. 24.
'8S' '84' COMPARISON N/A N/A 7%
OF ECT SIGNALS WITH. , (12 POINTS) GOOD SIGNAL / NOISE RATIO AND STRUCTURE. I1/05
Table 6-1 DC COOK UNIT 2 TUBE PROPERTIES AND OPERATING INFORMATION FOR THE EVALUATION OF THE ALLOWABLE TUBE WALL LOSS FOR THE DC COOK UNIT 2 TUBES THE FOLLOWING INFORMATION WAS USED: TUBING GEOMETRY: 0.875" DIAMETER C.050" THICK MATERIAL PRdPERTIES: , a,c.e OPERATING CONDITIONS NORMAL: Pi = 2250 psi Po = B20 psi
, 6P = 1430 psid P
FLB : AP- 2650 psid LOCA: Maximum external pressure, O internal pressure I
I l
\
l i l Table 6-2 j DC COOL Uf 4I T 2 STEAM GEr:ERATOR TUBE MINIMUM ACCEPTABLE WALL REQUIREMENTS TUBE SUPPORT PLATE ELEVATION CRITERIA COrJDI T I ON M IiJ I MUM WALL (IfJCHES) a,c.e YIELD NORMAL ASME CODE FAULTED S /3 NORMAL 1 l TUBESHEET CREVICE AND ABOVE THE TOP OF THE TUBESHEET ELEVATION l i CRITERIA CONDITION MINIMUM WALL (INCHES) YIELD NORMAL a,c.e ASME CODE FAULTED 5 /3 NORMAL i S l
Table 6-3 DC COO 6. UNIT 2 MINIMUM WALL DETERMINATION
SUMMARY
SG GEOMITRIC */. LOCATION CONDITION BASIS
-- - a,c.e TUBE SUFFORT DEGRADATION F LATE - AXIAL EXTENT LIMITED TO O.75 IN.
TOP OF DEGRADATION TUBESHEET AXIAL EXTENT GREATER THAN 1.5 INCH TUBESHEET DEGF:ADATION AXIAL EXTENT
=
GREATER THAN 1.5 INCH I s G e *
- Table 6-4 D C COOK NUCLEAR PLANT UnlT 2 OPERATINr, INTERVAL JUSTIFICATI0'l CATEGORY CREVICE ABOVE TS TSP
"'C
ALLOWABLE % ECT UNCED,TAINTY , GR0'lTH 8,0* 8.0* 8,0* PLUGGING LEVEL REQUIRE 9 (%) 39 38 46
-PLUGGING LEVEL IMPLEP1ENTED (%) ALL 30 40 f1ARGIN AFTER 3 MONTHS OPERATION (%) ---
g,n s,n
- WORST CASE GROWTH RATE PROJECTED FOR 3 EFPM OPERATION l
O t e
- - - - - -_ -,.---,,-e. . n. - - - - -.,c, , , - . , - - - , - - - - -
Table 7-1 D. C. COOK NUCLEAR PLANT SECONDARY SIDE WATER CHEMISTRY SPECIFICATION HISTORY STEAM GENERATOR AUGUST 1985 0CTOBER 1984 NOVEMBER 1983 SEPTEMBER 1974 Cook Cook Cook Cook Cook Cook Limit SGOG Limit SGOG Normal Limit Normal Limi CAT COND (umho) .8 ,8 1,1 .8 <1.5 1.5 2.0 7.0 S0DIUf1 (ppb) 20 20 20 <20 20 100 500 20 30* 50 20 <50 50 150 .500 CHLORIDE (PPb ) 20 SULFATE (ppb) 20 20 N/A N/A N/A N/A 30* -- 7.5 8.5-9.0 8.6-9.2 8.6-9.2 <8.8 8.5 9H 7.5 -- b -- -- 150 --
<150 -- <150 100 OH as CaC03 (PP )
SILICA (ppb) 500 300 500 300 <500 500 BORON (ppm) 5-10 5-10 -- -- -- LOWER DETECTABLE L!ti!T
STEAM OUTLET TO TURBINE GENERATOR DEMISTERS SECONDARY MOISTURE SEPARATOR - 3 NEN5h .,/ r-l -- T SECONDARY MANWAY h ORIFICE RINGS 6 -- - - -
.)] !
t
~
C] U lu j
- s. ,
_: s i SWIRL VANE PRIMARY MOISTURE SEPARATOR s
'gb -
/ UPPER SHELL
]
i
'J h *
- FEEDWirER RING FEECWATER INLET ' :
e 7 [
- ' J H0ZZLES ANilVlBRATION BARS .
z'x s
'g f TUBE BUNDLE iL'A /
s
.;Jrpgjeg
,y dddhil.ji@
liu ; q Wi%ma 7 r' c3 l II '3 %
/ bb LOWER SHELL WRAPPER
~s lk
/
3 hk hl TUBE SUPPORT PLATES 3 i!j$! gr BLOWDOWN UNE MIM TUBE SHEET
\ \
pi' g SECONDARY HANDH0LE N " c
%Q, j%$.
i
' 3 ., :
T* PRIMARY MANWAY L N. .J,, TUBE LANE BLOCK PRIMARY COOLANT INLET PRIMARY COOLANT OUTLET
@ SERIES 51 STEAM GENERATOR not to suu Figure 1-1
DONALD COOK UXIT 2 S/G 21 Model 51 August 1985 Hot Leg Inspection
- Disterted ladleeuens and Pereent Through-van Indleauens -
M Top of Tube Sheeb M Support Plates o < 20 Percent A 20 - 39 Percent M Above Tube Sheet M U - Bends *
*"** M Below Top of Tube Sheet
, p3 ed v Distorted Indication 40 N 5
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D0XALD COOK UXIT 2 S/G 21 Model 51
; August 1985 Hot Leg Inspection
- PERCENT INDICATION MAP - a.c.e c .
o < 30 Percent E Top of Tube Sheet M Support Plates A 20 - 39 Peroemt M Above Tube sheet M U - Bands
#***I
, pg d M Below Top of Tube Sheet to 4)
[- 30 3) s al Il II .]
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D0XALD COOK UXIT 2 S/G 21 Model 51
- August 1985 Hot Leg Inspection-
*c*
- Distorted Indications -
a m. tort.d z.meau.. M Top of Tube Sheet M Support Plates
, g,4 pgg 354 Above Tube Sheet M U - Bends M Below Top of Tube Sheet at Tube End
# 40 n
M i M a
- 5 20 20 I
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D0XALD COOK UXIT 2 S/G 21 Model 51 August 1985 Cold Leg Inspection
- PERCENT INDICATION MAP -
a .c.e E Top of Tube Sheet ' E Support Plates o < 20 Peroomt A 20 - 39 Peroemt M Above Tube Sheet E U - Beads
, g" E Below Top of Tube Sheet l
48 40 i I N N I N . 5 it O l !
~
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D0XALD COOK UXIT 2 S/G 22 Model 51 August 1985 Hot Leg Inspection
- a,c.e
- Mderted ladleations and Perecat Through-wsH Indications o < o p.,o..t M T*P of Tube Sheet M Support Mates A 20 - 39 Peroemt M Above Tube Sheet E U - Bends
*
- E Below Top of Tube sheet
~, p3 v Distorted Indleetion 40 0 i
2 30 $l "ot al 10 18
~
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- 4 D0XALD COOK UXIT 2. S/G 22 Model 51 l
i j August 1985 Hot Leg Inspection . PERCENT INDICATION MAP a .c.e I o < . ,,,,,,, m T*P of Tube Sheet' N Support Plates 1 A 20 - 39 Peroomt M Above Tube Sheet M U - Bends
- P a M Below Top of Tube Sheet
, p 48 40 , h a N 30 N 20 i
- 10 10 8 -
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t i
- i. LNo Amen. A.,i,/ecr / Leon *,A/ h 6 ,Aase. 11 W /Lc= /aK
l D0XALD C00I UIT 2 S/G 22 Yodel 51 August 1985 Cold Leg Inspection PERCENT. INDICATION MAP - a c.e o < 20 Pet M Top of Tube Sheet' M SEpport Plates A 20 - 39 Feroomt M Above Tube Sheet M U - Beede
, Ip "g M Below Top of Tube Sheet t
1 48
- S
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1
; D0XALD COOK UXIT 2 S/G 22 Model 51 1
August 1985 Hot Leg Inspection i i . Distorted Indications a,c e o Distorted Indiention x M o W P1 g ed E Top of Tube Sheet E Support Plates 14 Above Tube Sheet E U - Beads E Below Top of Tube Sheet & Tube End .i l M M 1 b 5 2 % a
~
M N t 10 10 l l
~
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DONALD C00I UXIT 2 S/G 23 Model 51 l August 1985 Hot Leg Inspection
. Disterted ladientions and Foresat Through-wall ladications
- a ,c.e M Top of Tube Sheet M SuppErt Plates o < 20 Pereent A to - 39 Peroomt M Above Tube Sheet E U - Bea4s
- y,$F;reeat, m E Below Top of Tube Sheet v m,terted ram.eu.a i
M 40 n
- j 2 5 a
't e
N 20 le 10 l
~
8 8 3 $ $ 4h $ 2 lb l I Manway Nozzle GENASYS Steam Generator Analysis System Tdr'ndanee WIm /%m*A/ F4/enanon MM l'm Ietr
D0XALD COOK UXIT 2 S/G 23 Model 51 August.1985 Hot Leg Inspection PERCENT INDICATION. MAP a .c.e
, < , , , _ , m T., .c Tab. sm t s s ,,.rt ri t A 20 - 39 Peroemt M Above Tube Sheet a U - Bends l Me$',Di m soleir T*, of Tube Sheet
- M M i n i N N l A 7
N N 14 10 2 R $ 4 8 8 8 8 th Manway Nozzle
- GENASYS Steam Generator Analysis System r E+._ hamW- aerridt Ten 9waaest Arbir dra /Atf
D0XALD C00I UIT 2 S/G 23 Yodel 51 August 1985 Hot Leg Inspection
- Distorted Indications a c.e o m. tort.4 rom u..
, u,4 gg M Top of Tube Sheet M Support Mat.s et n.= Tus. Sn..t M u - Be.4.
M Below Top of Tube Sheet & Tube Ena l 40 .4 4 h n lQ a
'?
~
N 10 10 15 l
~
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! GENASYS Steam Generator Analysis System
- I 1
l D0XALD COOK UNIT 2 S/G 23 Model 51 I i August 1985 Cold Leg Inspection
! - PERCENT INDICATION MAP -
a,c,e i o < 20 P m t M Top of Tube Sheet M Soph Plates l A 20 - 39 Parasat M Above Tube Sheet M U - Bends j
* " M Below Top of Tube Sheet
, g I
i
! 40 40 l
l l l I M 30
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l . 4 i 7
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- il 10 t
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- v. a: a - n . .o. e... .no v i: .n. a s.:. e ra c
D0XALD COOK UXIT 2 S/G 24 Model 51 August 1985 Hot Leg Inspection 1 - Disterted Indications and Percent Through-van ladleations a,c,e 1 E Top of Tube Sheet E Support Plates I o < 20 Peroomt a 20 - 39 Peroent M Above Tube Sheet E U - Bonds
- Pereen M Below Top of Tube Sheet
, h, p)
Y Disterted Indication
; M N 3 ?
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'l rdanem Mler Coon &hl Tal&viom Beebie Gun IM
- m. 4. --- ----
4 --a a .- - - a * - - 4s,.A w a _ 4%__.,_ 4 _ , . , _ _ D.C.C00< UNIT 2 INJICATION COUNT 8/85...,,c, 4 m i Z O H
<C C)
H. . O i Z I H 11
- a CE n LIJ i & CD c 1 A D Z
7
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I 1 l l PERCENT INDICATIQNS S/5 24 IIdT LEG
D0XALD COOK UNIT 2 S/G 24 Model 51 August 1985 Hot Leg Inspection PERCENT INDICATION ' MAP - a,c.e ! o < to Peroomt E Top of Tube She'et E Eupport Plates t 4 20 - se percent 314 Above Tube sheet E U - Beads
- h ,3'O #g pQ",*, E Below Top er Tube sheet 5 M N 3
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4 D0XALD COOK UXIT 2 S/G 24 Model 51 August 1985 Hot Leg Inspection
- Distorted Indications a ,c,e i c -
o Disterted Indleati s E Top of Tube sheet M Support Plates
, g,4 g WW1 Above Tube Sheet M U - Beads E Below Top of Tube Sheet & Tube End i
43 44 i l
- j 30 33
- a
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1 D0XALD COOK U31T 2 S/G 24 Model 51 i August 1985 Cold Leg Inspection
^cd
- PERCENT INDICATION MAP a < 20 Peroomt M Top W W n M W mw A 20 - 38 Pereent M Above Tube Sheet E U - Bends
* ~ #" E Below Top of Tube Sheet
, g 40 4
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D.C.C00K UNIT 2 PLUGGABLE INDICATIONS. ..c.. m B i-' 5 a 5 es 5 9 3 E ~ . a .
,E ~
TYPE OF INDICKTION ~~ STG 24 8/85
D.C. COOK UNIT 2 PLUGGABLE INDICATIONS -
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C2 M e O 5 E e = n m '
- h CE
~
elui TYPE OF INDICATION COMPOSITE 8/85
U. L. COOK UNIT #2 (AMP) CliAllllEL 110 -- t CilAllllEL fl0 --- 1 BETWEEN THE TWO BLACK DOTS e "II,lDICATION" o g j 'f'
/
STRAIGHT LINE TRANSITICN I s- n.
- LOWER LEFT QUADRANT l 'N g.-N
)y g SUPPORT LOBES
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>l VOLT PEAK TO PEAK 3.4 VOLTS J 29 M 47 M 1.E.0 VOLTS 137 g 40 y FIGURE 1 -,
400 KHZ - DIFFERENTIAL FIGURE 3 "THRU-WALL (%) PENETRATION" FIGURE 2 100 KHZ - ABSOLUTE FIGURE 4 CHAtillEL 180 -- 4 C11f44t4EL I40 -- 4 _,= / ,s'
'f
,/.,/
,/ ,,,,
() f f p- OD INDICATION / f' // 8 i i T.83 VOLiS 81 DEG 0 ?. 3.21 VCLTS 20,2 DEG Figure 2-20 Eddy Current Displays for Typical
" Clean Indications"
CHA!4HEL 110 - 1 Clinl4HEL HO -- 1 (s.' % s f'.s My i 7f-NO LEFT EXCURSION AND ,'y f,. 5 . CURVED TRANSITION o o,
\'.N...,,
l N.
. i.,
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el VOLT PEAK TO PEAK 2.57 VOLTS 135 L'1:!i al , 0.9;' v0LTs 159 e of FIGURE 5 400 KHZ - DIFFERENTIAL FIGURE 7 "DI" FIGURE 6 100 KHZ - ASSOLUTE FIGURE 8 CHANNEL HO -- 4 CHAHHEL HO -- 4
- <S
//,%.s.C7 / /
.././
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/ //
i f f/
/ OD INDICATION-W
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2.37 VOLIS 54 DEG L 52 YOLTS 48 DEG 0 *< Figure 2-21 Eddy Current Displays For Typical
" Distorted Indications"
a,c.e Figure 2-22 Eddy Current Display SG 22, R25C51- Squirrel Indication
E 4,C.E O e e e et e up Figure 2-23 Eddy Current Displays for Tube R11C25 , $G 22, Representing absolute drift
.- . bY- 2 .
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e ,, Figure 3-1 Transverse metallography of tube R18C77 5th S.P. location showing axial SCC and some surface IGA. ' 26
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DRAFT 11/55 CRACr DEDTH DISTR $UTICN t1EAN - APPROX.1/2 MAX. 16 M'
- i. a 16 E ~j
' 14 ] 11EAN
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N F-12 3 rjq FRIOUENCY OF 10 I
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MICR0 M981 3 3 5 7 9 11 13 15 17 19 21 CRACK OEPTH. MILS Figure 3-4 Plot of crack depth distribution for the 1st S.P. location of R18C77. e 27
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Figure 3-5 Transverse metallography of the tubesheet top location of R18C77 showmg SCC. . 29
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Y : h@6#dT8,7.MhRh'=' A ML h Figure 3-6 Transverse metallo location (actually 0. graphy 5 inches ofbelow the tubesheet top) of top R6C40 showing 3CC. ' 30
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O 33
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e 0 e 34
- n e -
s COOK BUPST TEST DATA a.c.e . PRESSURE.100C PSI BURST DELTA DIAMETER. X - Figure 3-9 Cook Burst Test Data (Table 3-4 Supplement) O 4b
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;M 1, Rucar is 83r* 2.4x Figure 3-10 Burst opening on specimen R11C25,3rd S.P. region, at a location well away from the restraint S.P.
collar used on this burst test. 16
-. a,c.e CRACK ASPECT ratio - L/D R7C30452 R7C38752 R7C359 2
, uma rene ma ouri, a Fgiure 3-11 Aspect ratios from the ist,2nd, and 3rd S.P.
region of tube R7C38 plotted versus crack penetration. O e
Figure 4-1. D C. C00r. UtiiT 2 - til9ECTi0tl Atl0 DESTRUCT!VE EXAt1 COMPAR1501
~]a,ce 100 90 '
80 70
!:' I!!SPECTION 60 DEATH OF 50 PP.ETRATION %
ao 30 20 10 0 0 to 20 30 40 50 60 70 80 90 100 CESTPUCTivE ExAr1 DEPTH C# Pitier A 40ta. , MAXif1UM % DEcTput? vE.NeerESTouCTivE DATA SG ON '** tEG t *C ATl*N ACTUAL INITIAL ECT 2ND E*.T MAY % % % 24 19 55 HOT ABOVE T S 65 60 SC-60 24 21 53 HOT A:0VE T S 65 SIGN 18'C ANT to 21 16 44 HOT A30 VET 5. 64 546t.;FICANT 40 21 4 42 HOT A30VE T.S. 46 - 20* 2: 16 40 HOT ABOVE T.S 100 100 SIGNIFiCANT 21 16 35 HOT A!OVE T S. <5 - - 21 16 53 HOT ABOVE T S. 0 0- 0-
- 6 40 %T
- 5. C;~V'CE It -- ---
- 1: 4: HOT T 5 GEvlCE 80-:00 E: SO 22 13 77 HCr !E GE'/:CE IJ -- ---
2 18 77 n0T IST T53 56 SIG!;J. CANT 20-40 22 18 77 HOT t;D TS: 5 + 31GINICAt4T 30-40 22 18 77 HOT 3:0 T3D 344- - - 22 13 77 HOT 4fH TIP J+ -- --- 22 18 77 HOT STH TEP 46 34 4t) 22 2 4: H0T :!! T3: 20 - -- 22 1: J: 607 3:0 T5: 02 - ---
- 12 4: HOT STw !P *: -- ---
02 1: 25 Ha,T 3:0 T!? 30 --- --- 2: T I3 woi '!T T : 59 30 40
- 2 7 33 4T ?.0 T5P 3: .0 20 22 7 35 HOT 300 TSP 5
*: 6 40 HOT 300 T!: 00 --- ..-
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11/05 CRACK DEPTH DISTRIBUTION 18 16 14 12 10 FREQUENCY OF OCCURRENCE 8 6 4 2 R18C77-1 0 tilCR0 M981 1 3 5 7 9 11 13 15 17 19 21 - CRACK DEPTH, MILS Figure 4-2 Plot of Crack Depth Distribution For The 1st Support. Plate location of R18C77 9 6- _.. . ..... . , , ,
Figure 4-3 D C. COC*. UNIT 2 ECT tNSPECTION UNCERTAINTY VS DE;'H T"4:0 d,C,0 25 20 DtFFE?INCE B!% TEN ECT Att DESTRUCTIVE 15 E.' A" MA/.: MUM DEFin. : 10 5 0 0 10 20 30 40 50 60 70 80 93 100 DE:TH % ,ifg3 O h .W
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I . EFFECT OF BORIC ACID w ON PRE-INITIATED CRACKS- - 8,C,e k O I
)
Days to Produce Throughwall Crack - 894 B18667.032
EFFECT OF BORIC ACID IN REFERENCE IGA TESTS ' IGA Depth pm -
,,c,,
240 200 2 E 160 g T 120 80 40
, 90 120 150 180 ....,.r;,
Days .
SERIES #5 TEST #2 AXIAL DISTRIBUTION OF Q W MO.LAR RATIO OF BORONJFO SODIUM - B/Na Molar Ratio _ 12 10 8 2 6 I 2 O 4 8 8 10 12 14 16 18 20 22 , Axial Location in inches from Bottom 896 B1884F.041 1
to
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