ML19261B230
| ML19261B230 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 04/28/1978 |
| From: | Webb Patricia Walker GENERAL ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML19261B218 | List: |
| References | |
| 78-509-66, NUDOCS 7902140269 | |
| Download: ML19261B230 (41) | |
Text
{{#Wiki_filter:PME TRANSMITTAL NO. 78-509-66 APRIL 1978 DRESDEN 1 RADIATION LEVEL PROGRAM CORROSION TESTS PROGRESS REPORT NUCLEAR ENERGY BUSINESS GROUP
- SAN JOSE, CALIFORNIA 95125 GEN ER AL h ELECTRIC m : % 2co
GEN ER AL h ELECTRIC ~ PME TRANSMITTAL NUCLEAR ENERGY DIVISION DRF 509DEV0021 PLANT MATERIALS ENGINEERING INTERIM REPORT FRACTURE MECHANICS TESTS OF SIMULATED CLAD CRACKS IN ADDITIONAL HEATS OF ASTM A335-P1, A302-B, A106-B, AND A105 EXPOSED TO DOW NS-l CLEANING SOLVENT April 28,1978 PREPARED BY: '#dh
- Mr W. L. Walker Plant Materials & Process Development APPROVED BY:
(( <? 4
- f. C. Danko, Manager Plant Materials & Process Development APPROVED BY:
/ '[ A N G. M. Gordon, Manager Plant Materials Engineering ) APPROVED BY: I d /M R. A. Proebstle, Manager Applied Metallurgy & Chemistry THE DATA REPORTED IN THIS DOCUMENT WERE GENERATED IN A CUSTOMER-FUNDED PROGRAM AND SHALL BE TREATED AS PROPRIETARY INFORMATION. DISTRIBUTION T. E. Adams - (12) G. M. Gordon R. L. Cowan R. A. Proebstle J. C. Danko C. P. Ruiz
e f DISCLAIMER OF RESPONSIBILITY i This document was prepared by the General Electric Company pusuant to a ommonwealth Edison Company. Except as otherwise provided contract with the c in such contract, acither the General Electric Company nor any of the contributors to this document nor any of the sponsors of the work makes any warranty or reprc entation (express or implied) with respect to the accuracy, completeness, or usefulness of the information contained in this document or that the use of such information may not infringe privately owned rights; nor do they assume any responsib!!ity for liability or damage of any kind which may result from the use of any of the inforr:ation contained in this document.
INTERIM RFPORT FRACTURE MECHANICS TESTS OF SIMULATED CLAD CRACKS IN ADDITIONAL HEATS OF ASTM A335-Pl, A302-B, A106-B, AND A105 EXPOSED TO DOW NS-1 CLEANING SOLVENT by W. L. Walker INTRODUCTION During the proposed Dresden 1 chemical cleaning operation, the exposure of bare carbon steels and low alloy steels will be mini ized. However, a m number of areas of stainless steel-clad carbon and low alloy steels will be exposed to the solvent (NS-1). Questions were raised during discussions on the propagation of any through-clad cracks which might exist at these locations. An expanded fracture mechanics corrosion test program was initiated to provide answers to this question, and questions related to subsequent service behavior of existing cracks following exposure to NS-1. The steels of interest were A336-F1, A302-B, A335-P1, A106-B, and A105. This report summarizes the data generated on two additional heats each of A335-P1, A302-B, and A105, and a single additional heat of A106-B. The results of testing of multiple heats of A336-F1 have been previously reported in PME Transmittal No. 77-509-70 (August,1977) and the results of testing single heats of the 'four alloys previously mentioned have been reported in PME Transmittal No. 78-509-002 (January,1978).
SUMMARY
Simulated clad-cracked 1-T WOL fracture mechanics specimens were prepared from heats of material which had been weld clad in the notch area and post-weld heat-treated. A fatigue pre-crack was propagated through the stainless steel weld deposit and stainless steel cover plates were electrically coupled to five sides of the specimens, to give a very large cathode-to-anode surface area ratio at the tip of the crack in the carbon or low alloy steel base metal. Triplicate specimens from each heat were loaded to stress intensities of 90 ksi M. and exposed to a simulated cleaning cycle of approximately 100 hours at 250 F (121 C). In addition, triplicate specimens from each heat were loaded to 90 ksi M. and exposed to demineralized water at 250 F for approxi-mately 100 hours as controls. Following the 250 F exposures, all specimens were subjected to simulated BWR service exposures totalling 738 hours, with examinations at 167, 496 and 738 hours. Examinations of the specimens following the NS-1 exposure revealed varying degrees of galvanic corrosion in the fatigue pre-crack, on all four alloys. One specimen of A335-Pl exhibited a large increase in crack length during the NS-1 exposure, but a similar increase was observed on a control specimen of the same alloy from a different heat. Crack length measurements made photographically during the simulated BWR exposure did not indicate any evidence of accelerated crack extension on any of the specimens resulting from expsoure to NS-1. However, cestructive metallographic examinations performed on single specimens from each heat did indicate some crack extension occurred in the A105 specimens exposed to NS-1, although some evidence of similar extension was also observed on the control specimen from this alloy. The apparent extension was approxi-mately 0.01 inches. Longer term exposure of specimens will be required to evaluate the significance of these observations. DETAILED DISCUSSION Materials Specimens were fabricated from tne following heats of materials in the indicated product forms. Alloy Heat No. Product Form A335-Pl 3582 16" Sch. 160 Pipe A335-P1 814950 18" Sch.140 Pipe A302-B 5923 3.9" Plate A302-B 5933 3.9" Plate A106-B 66402 12" Sch.160 Pipe A105 44331 13g" 0.D., ik" Wall, Sleeve Forging A105 2748 13h" 0.D.,1 " Wall, Sleeve Forging Mechanical properties tests and chemical analyses were performed on each mater-ial. All elements were within specification limits and a detailed listing of of both mechanical properties and composition will be presented in the final report on the fracture mechanics test program. Specimen Fabrication Specimen fabrication was basically the same as in previously reported runs,with the plate materials being grooved, welded, post-weld heat-treated, and then final machined into ASTM A399 l-T WOL specimens. Specimens were prepared from the piping and sleeve forging materials by rough-machining specimen blanks from the walls, tack-welding the blanks together for machining of the groove, machining, welding, and post-weld heat-treating, and final machining to A399 specifications. All post-weld heat treatments consisted of three hours at 1150 F with a furnace cool. Eight specimens were machined from each material, cover plate attachment holes were tapped, and the specimens were fatigue pre-cracked in accordance with ASTM A399 into the base metal. One specimen of A106-B material was lost during machining because of misplacement of the bolt loading hole, and one speci-men of A302-B was lost during pre-cracking due to the development of a crack oriented 90 degrees to the direction of fatigue pre-crack. Specimen Loading The stress intensity for this series of tests was 90 ksi /Iii. Compliance curves were generated on single specimens from each heat, and the crack opening displacement (COD) values required for the elected stress intensities were calculated for each of the specimens. The specimens were loaded with a torque wrench, with continuous C0D value measurement, to the selected levels. Six specimens from each heat (except for one A302-B heat) were loaded to the 90 ksi /IIIlevel, and the remaining specimens from each heat were left uninaded and reserved as spares in the event that further work might be required on short noti ce. Crack lengths were measured after loading of each specimen. Specimen Exposure and Crack Length Measurements Prior to exposure of the specimens, five of the six machined faces were masked with a pressure-sensitive silicone rubber gasketing material to exclude solvent from the stainless cover plate-low alloy steel crevice area. The specimen face left open was the notched face, to permit free access of test solutions to the crack tip. The stainless steel cover plates were then bolted to the specimens and the specimens were exposed to the test solutions. Three specimens from each heat were exposed to demineralized water at a tem-perature of 250 F for a total of approximately 100 hours at temperature, except for A302-B Heat No. 5933 in which only two specimens were run. These specimens acted as controls for the determination of the effects of exposure to NS-1. The remaining specimens from each heat were exposed to simulated "used" NS-1 solution which had been nitrogen sparged for a minimum of four hours prior to insertion of the specimens. The test vessel was a Teflon-lined pipe spool piece, with Teflon-lined blind flanges for closures. The solution volume-to-surface area ratio during the NS-1 exposure was approximately 1 gal /ft. Specimens were exposed to the NS-1 solution for approximately 100 hours at 250 F. No problems in maintaining temperature control through the use of straight line voltage and variable transformers had been encountered in any of the previous runs. However, during both the water control and the NS-1 exposures in this part of the investigation, significant line voltage fluc-tuations occurred which resulted in test temperatures rising to as high as 269 F, and several vessel blowdowns were required during each run. Since all specimens in this portion of the investigation were exposed to higher temperatures for significantly longer periods of time than any of the other specimens, this set of runs may represent more severe conditions from a corrosion standpoint. Following the initial exposure to either demineralized water or NS-1 the cover plates were removed from the specimens and the silicone rubber gaskets were stripped off. Crack length measurements were made optically, when poss-ible, and photograph _ically when optical measurements proved to be inadequate. Some grinding of specimens exposed to NS-1 was required to remove corrosion product resulting from general pitting attack which occurred on the exposed surfaces, and to clearly delineate the notch and crack tip where crevice and galvanic corrosion occurred. Light polishing of the control specimens which were exposed to demineralized water was required in order to measure crack lengths on those specimens. Following crack length measurements on the control and simulated NS-1 cleaning cycle specimens, the stainless steel cover plates were replaced on all specimens. The specimens were then subjected to three exposure periods in simulated BWR water (0.2 ppm oxygen, 550 F) with durations of 167, 239, and 332 hours. The initial exposure was begun with the specimens immersed in air-saturated water which was displaced from the autoclave during heatup by 0.2 ppm oxygen water. The two subsequent exposures were begun with nonncl loop water at the lower oxygen level. After each ex.osure period, the spec.' mens were removed from test, the side cover plates were removed, and cra k length measurements were made. Throughout the entire program, the specimens were stored under conditions of 100% relative hum-idity when not. actually on test in order to prevent dehydration of corcion products in the crack tip, except during optical and photographic measure-ment of crack lengths. - _m
RESULTS Specimen Examinations Optical measurements of crack lengths were made on all the control specimens initially exposed to 250 F demineralized water at each examination period. Light hand polishing of the side groove with 120 - 600 grit silicon carbide paper was necessary in order to delineate the cracks clearly. Some di ffi-culties in obtaining clear delineation were encountered on several speci-mens, and subsequent metallographic examination revealed that this was due to the presence of fine cracks which were not resolved at the magni-fications us9d for the optical and photographic measurements. In addition, the polishing techniques used to date also contributed to the lack of delin-eation of these fine cracks. Polishing procedures have been corrected for future tests, and optical examinations at higher magnifications will be made prior to either optical or photographic measurements in the future. There are no indications that similar problems have been encountered in previous runs. The specimens exposed to NS-1 suffered varying degress of corrosion, and optical measurements of crack lengths were not possible because of the shallow depth of focus of the optical measuring equipment. Air cool grinding of the side groove to reach base metal and achieve satisfactory delineation of the notch root and crack was required. By agreement with Dow Nuclear Services, only a single specimen from the high stress intensity group of each heat was ground heavily, in order to avoid compromising the fracture mechanics aspect of the specimens through reduction of the speci-men thickness. Demineralized Water Control Exposures Some indications of crack propagation were observed after the exposure of approximately 100 hours to demineralized water at 250 F in control speci-mens from A335-P1 (Ht. No. 914950), and A302-B (both heats). These indi-cations were based on nondestructive photographic measurements of the crack lengths from the outside surface of the specimens, and some amount of uncertainty is associated with such measurements because of the inter-pretation of polishing artifacts, surface discontinuities, and limits on resolution of fine cracks. After completion of the three subsequent simu-lated BWR exposures, a single specimen from each alloy was subjected to destructive metallographic examination for confirmation of the initial observations. A typical as-received fatigue pre-crack is shown in Figure 1. The appear-ance of the side groove on the A335-P1 specimen following the demineralized water exposure is shown in Figure 2. Measurement of the clearly delineated crack length indicates an extension of approximately 0.010 inch.
- However, there is a diffuse indication which, if measured at its extreme limit, would give a value of approximately 0.18 inch.
The length of the clear crack increased, and the length of the diffuse indication decreased somewhat, throughout the subsequent simulated BWR exposures, which indicates that most, if not all of the propagation occurred during the 250 F exposure. A photo-graph of the specimen following 738 hours exposure to simulated BWR service is shown in Figure 3. Specimens from both heats of A302-B exhibited diffuse crack indications, but not of the magnitude of the single specimen from A335-Pl. An example is shown in Figure 4. Like the A335-P1 specimen, little or no crack exten-sion was observed during subsequent simulated BWR exposures. Single speci-mens from both materials were subjected to destructive metallographic examination following completion of the BWR exposures, and these results will be presented in a later section of this report. _"ljsed" NS-1 Exposures All specimens exhibited varying degrees of general corrosion which necessi-tated grinding of the side groove to base metal in order to delineate the crack. As in previous runs, a single specimen was selected from each heat of material, and only one side groove was ground and polished. The appearance of these specimens is shown in Figures 5 through 11. There was clear evidence of crack extension of approximately 0.2 inch in one heat of A335-P1 (Heat No. 3582), but no evidence in the other. These results are contrary to the results observed in the demineralized water control specimens where crack extension indications of approximately 0.2 inch were observed in one specimen from Heat No. 814950 and no indications were observed in any specimen from Heat No. 3582. Some possible evidence of slight crack propagation during the NS-1 exposure was also observed in A106-B (Heat No. 66402) and one heat of A105 (Heat No. 44331), as shown in Figures 9 and 10 respectively. No other specimens gave indications of crack pro-pagation during the NS-1 exposure. Simulted BWR exposures As stated previously, all specimens were exposed to three periods in simu-lated BWR water (0.2 ppm oxygen, 550 F), with the first startup made in air-saturated water. Photographs of the specimens selected for grinding from those exposed to NS-1 are shown in Figures 12 through 18. Optical and photographic crack length measurements were made on all control specimens from each heat of material, following each exposure period. Photographic measurements were also made on the single ground high stress intensity specimen from each heat followir.g each BWR exposure. The results of these measurements did not in-dicate significant effects of NS-1 on crack extension in subsequent BWR ser-vice. Exposure to high temperature water appears to cause dissolution of the corresion product from the initial NS-1 exposure, but not significant crack extension. Fracture Surfaces In previous runs, pairs of specimens from each heat of material were loaded to stress intensity levels of 40 ksi M., and single specimens from each heat were fractured following the simulated BWR exposure to determine the general shape of the crack front. All previous data had indicated straight crack fronts, and there had been no indications of significant differences between the 40 ksi 6. specimens and those loaded to 90 ksi/Iii. Since the results from these specimens had been the same as those loaded to higher levels, and a possibility of additional testing being required on short notice at scme later date existed, the lower stress specimens were not loaded or run in this series of tests. Furthermore, the need for longer term simulated BWR exposures of previously tested specimens had been discussed and agreed to by Commonwealth Edison. For these reasons, none of the high stress specimens were fractured in this series of tests. How-ever, the metallographic results to be discussed in the following section provide information regarding the crack front shapes. Metallographic Examinations The single high stress intensity specimen from each heat of material which had one side-groove ground to permit crack length measurements throughout the simulated BWR exposures was sectioned for metallographic examination at the specimen mid-plane. In addition, a single control specimen from each alloy was also sectioned for metallographic examination. The selection of the control specimen for examination was made on the basis of maximum indication (s) of crack propagation during the course of the exposures. The results obtained from A335-P1 are shown in Figures 19 through 22. As indicated by the photographic measurements, the specimen from Heat No. 3582 exposed to NS-1 shows clear evidence of crack propagation, as shown in Figure 19, while the specimen from Heat No. 814950 exhibited only general galvanic corrosion as shown in Figure 20. In addition, the crack extension measured metallographically was approximately 0.4 inch while the extension estimated from prior external photographic measurements was only approximately 0.2 inch. These results would indicate an acceleration of the cracking process at the specimen mid-plane, which was confirmed by the results of the A335-P1 control specimen from Heat No. 814950. When metallography was completed on this specimen it was discovered that the sectioning cut had not included the full crack length, as shown in Figure 21. The remainder of this specimen was recovered from scrap, fortunately, and the true crack extension was estimated to be approximately 0.4 inch. A more precise figure is not possible because of the unknown loss of material during the sectioning process. Photographic crack length estimates had indicated values of approximately 0.2 inch. throughout all examinations of this specimen, and Figure 22 clearly shows the extension of the crack in the mid-plane without indications on the exterior surfaces of the specimen. All of the data generated previously, and most of the data obtained in this portion of the investigation, have indicated relatively straight crack fronts as shown in Figure 23-A. However, these two specimers clearly have leading crack fronts in the mid-plane area as shown in Figure 23-B. While the true cause of these differences on these specimens is unknown, one can speculate that a leading mid-plane crack front occurs when the specific crevice solution chemistry at the crack tip represents a more nevere corrodant than the external environment. If the external environment is more agressive than that at the crack tip, propagation tends to be more rapid on the specimen side grooves, and a trailing crack front results as shown in Figure 23-C. The only external evidence of leading crack fronts observed in this investi-gation has been the diffuse crack indications, and only one other specimen (water control from A335-P1 Heat No. 814950) has exhibited such large indi-cations. Further testing of these specimens must proceed in their present condition, and examination techniques will be refined to detect diffuse indications. The A302-B specimens are shown in Figures 24 through 26. The specimens exposed to NS-1 exhibit crack blunting and general crevice corrosion, but no indications of crack extension. The A302-B control specimen shows no indications of crack extension. The A106-B specimens are shown in Figures 27 and 28. The specimen exposed to NS-1 shows some slight indications of crack extension during the simulated BWR exposure. No indication of crack extension was observed on the control specimen. The A105 specimens are shown in Figures 29 through 31. Some indications of slight crack extension (approximately 0.01 inch) during the NS-1 cycle were observed on the specimen from Heat No. 44331, and equally slight indica-tions of crack extension during the BWR exposure cycle were observed on the specimen from Heat No. 2738. However, similar extension may have occurred in the control specimen, shown in Figure 31. A comparison of the externally measured crack length with the metallographically measured length on the specimen from Heat No. 44331 which was exposed to NS-1 indicates a slightly leading mid-plane crack front in this specimen also. CONCLUSION The data generated in this portion of the investigation continue to indicate that the general effect of exposure to NS-1 on simulated through-clad cracks is some galvanic / crevice corrosion which results in some undercutting of the clad and blunting of the existing crack tip. While crack extension of approximately 0.4 inch was observed in a single A335-P1 specimen exposed to NS-1 in this portion of the investigation, similar extension was observed in a single control specimen of this same alloy which saw no exposure to NS-1. Specimens of A105 material exposed to NS-1 continue to exhibit slight indications of crack extension either during the simulated cleaning itself or in subsequent simulated BWR service exposures, without the consistent observance of similar extension in control specimens. The magnitude of the crack extensions observed in A105 material in both this and the previous run is approximately 0.01 inch, and longer term exposures will be required to evaluate the significance of these observations. Sli ght crack extension has been observed or other alloys, but the magnitude of the extension of the specimens exposed to NS-1 was generally similar to that of the control specimens. Extended simulated BWR environmental exposures are planned for specimens from all heats of materials tested to date. Data from these exposures should provide more definitive answers to some of the questions raised regarding differential behaviors within the same alloy or within the same heat, and the significance of the small crack extensions consistently observed on A105 material. A preliminary data summary of all carbon and low alloy steel fracture mechenics test results is shown in Table 1. The extension values shown ir. Table l represent the combined increase in original crack length resulting from both general corrosion and true crack extension, if such cracking occurred. The " maximum" values shown represent the maximum difference exhibited by any specimen within the heat at the particular measurement point, and are not necessarily from the same specimen at different measurement points. In addition, the "metallographic" value does not necessarily represent the speci-men from which either of the " maximum" values was obtained. Additional metallography will also be necessary. This repolishing may result in some differences in the "metallographic" values between those shown in this report and the final report, due to differences in depth of corrosion / cracking at different points through the specimen thickness. However, these differences should not be of a magnitude which would result in significant changes in the conclusions from the work performed to date. TABLE 1 Maximum Measured Metallographic o Crack Extension (in.) Measurement Alloy Ht. No. Exposure 250F(I) BWR(2) 250F + BWR(3) Remarks A336-F1 210832 HO 0.023 0.013 ND 2 NS-1 0.022 0.01 6 0.007 No Cracking 43563 HO -0.004 0.010 ND 2 NS-1 -0.019 0.011 -0.015 No Cracking 45716 HO 0.005 0.002 ND 2 NS-1 0.007 0.026 -0.015 No Cracking A335-P1 3263 H0 2 0.019 0.020 ND NS-1 0.078 0.020 0.011 No Cracking 3582 HO 0.017 0.003 ND 2 NS-1 0.1 80 0.01 7 0.42 Cracking in NS-1 814950 HO 0.1 76 -0.050 0.4 Cracking in H 0 2 2 NS-1 0.037 -0.004 0.035 No Cracking A302-B 2529 HO 0.002 0.017 ND 2 NS-1 0.042 -0.036 -0.017 No Cracking 5923 H0 0.038 0.009 ND 2 NS-1 0.044 0 0.029 No Cracking 5933 HO 0.012 0.017 0.017 No Cracking 2 NS-1 0.040 0.004 0.017 No Cracking A106-B 66549 HO -0.044 0.023 ND 2 NS-1 -0.005 -0.010 -0.029 No Cracking 66402 HO 0.011 -0.004 -0.014 No Cracking 2 NS-1 0.028 -0.008 0.010 Cracking in BWR A105 38875 HO -0.004 0.036 0.012 No Cracking 2 NS-1 0.010 0.007 -0.020 Cracking in BWR 44331 HO 0.013 0.001 -0.005 Possible Cracking 2 NS-1 0.027 -0.009 0.057 Cracking in NS-1 2748 H0 0.029 -0.005 ND 2 NS-1 -0.0 01 -0.003 0.004 Cracking in BWR 1. Photographically measured length after 25.0 F exposure minus as-received length 2. Photographically measured length after 3rd BWR exposure minus length after 250 F exposure. 3. Metallographically measured length minus as-received length 4. ND - Not Determined Metallographically
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FIGURE 14 - Notch root and crack on A302-B (Ht. No. 5923) specimen after simulated BWR exposures. All photos at 8.6X magnification.
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%c ;t wa >..t e j.. ' ?t-A y q n v. y N c. 1 l'Ig (;, 'k y :y .gm W :' __ f ifp: : T ' - -~~ w '. 406 hours exposure ~ b w.. ~.w,.. i 7 7 .e 4 r W-g- p.m [2* p" 738 hours exposure g-1 e.6:.l.m.[+tw. ~l ~ _ ;:, y 33 I L. FIGURE 15 - Notch root and crack on A302-B (Ht. No. 5933) specimen after simulated BWR exposures. All photos at 8.6X magnification.
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I L. FIGURE 16 - Notch root and crack on A106-B (Ht. No. 66402) specimen after simulated BWR exposures. All photos at 8.6X magnification.
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.[ j. j;k. .</. 4< , -rweg,anx%. 7. ?. 4sush.s. - %"w - '.ikw a.n - - -.. ..,.e mw.~7 .; n w y. ,- -: v,.. 8 ~ >r sp 4A,n-,. .pr Ii:w s ~. +.... afy mf 4 >< Tc&.p: :..:. m. s %,.s g f.7 ' ' ..s 7 738 hours exposure mw_ km. 7,L,. ru..- e r -7 a .n ~- fp 7 w. ;,n,4;p,. m ~ W%~m W.. ...._..t....#- c. FIGURE 18 - Notch root and crack on A105 (Ht. No. 2748) specimen after simulated BWR exposures. All photos at 8.6X magnification.
I:1L111!!111111111 ~ Q2 Et:;. ,%;~ . c;, _ ? : 4q a ~ !: q: E f.' i t s ( .e -l k'[L_ d3 Machined Notch and Pre-crack Area 3.8X (Scale divisions shown are millimeters)
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.$/,t,[ "Ca^ ' y q% E-p. A $ (*1 LL z%).* s '.c's 3 s '.g't,' ? 4,. j. p... Wok W $,l 1 .g f? g E,$ es, 4 p s Crack Tip Area 100X FIGURE 19 - Mid-plane section through A335-P1 (Ht. No. 3582) specimen after NS-1 exposure and 738 hours simulated BWR exposure. Note lower magnification on macro photo.
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s ,qo . =~ '7 I ?..,{ .] <y ':( ~;~ .n m.:p 79:. y k v I-i_.u..e.m L 3- - ; Machined Notch and Pre-crack Area 3.8X (Crack extends beyond specimen edge)
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\\> P p: -..i -R.,, x d ;*; M - z u. Special polish on side groove to show extent of diffuse indication. Note that indication does not extend to cut edge of specimen. (8.6X) y.. T.. 7 s. n.. : y y;,.. p..:7...-. -.. y:. ; ;2. "y '. r.,:9... p-.:p . g4 ~ v 7' 3,, a. .a s
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Note that crack does not extend to the surface of either side groove. (8.6X) FIGURE 22 - A335-Pi (Ht. No. 814950) control specimen after 97 hours U in 250 F demineralized water and 738 hours in simulated BWR environment, showing lack of crack extension to side groove surfaces.
A. Straight Crack Front Typical of prior tests in fracture mechanics program, a a a ((#g'..,i' Propagating Crack ~ i, - Z Fatigue Pre-Crack B. Leading Crac'k Front a } u i Observed on A335-P1 control <1: s. I and NS-1 specimens, and J. 71! *, possibly on A105 NS-1 --'+++444 specimen. ->- ilii.!! +---- Propagating Crack CEE +44 + +++rysu _ _ '_ - - 1 _ *---- Fatigue Pre-Crack C. Trailing Crack Front Not observed in fracture mechanics tests to date. n u a 4 + L+ %g;,*, +- Propagating Crack tittt ti t t _- :_:_::_ ~ Fatigue Pre-Crack FIGURE 23 - Schematics of three idealized crack propagation modes in 1-T WOL specimens.
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