ML15329A273
| ML15329A273 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 12/31/2005 |
| From: | Couvant T, Vaillant F, Amzallag C, Boursier J, Champredonde J Govt of France, EDF Generation |
| To: | Atomic Safety and Licensing Board Panel |
| SECY RAS | |
| References | |
| RAS 23735, 50-247-LR, 50-286-LR, ASLBP 07-858-03-LR-BD01 | |
| Download: ML15329A273 (9) | |
Text
RIV000140 Submitted: November 9, 2012 Proceedings of the 12th International Conference on Environmental Degradation of Materials in Nuclear Power System - Water Reactors -
Edited by T.R. Allen, P.J. King, and L. Nelson TMS (The Minerals, Metals & Materials Society), 2005 INFLUENCE OF A CYCLIC LOADING ON THE INITIATION AND PROPAGATION OF PWSCC IN WELD METAL 182 François Vaillant1, Jean-Marie Boursier1, Thierry Couvant1, Claude Amzallag2, Jacques Champredonde3 1
EDF/R&D/MMC, Les Renardires Research Center, 77818 Moret sur Loing, France 2
EDF/SEPTEN, 12-14 avenue Dutrievoz, 69628 Villeurbanne Cedex, France 3
EDF/CEIDRE, 2 rue Ampre, 93206 - Saint-Denis Cedex 01 Keywords: Stress Corrosion Cracking, weld metal 182, primary water, cyclic loading Abstract Introduction PWSCC (Primary Water Stress Corrosion Cracking) of nickel PWSCC (Primary Water Stress Corrosion Cracking) of nickel based weld metal 182 is now a major issue in Pressurised Water based weld metal 182 is now a major issue in Pressurised Water Reactors, since significant cracking was observed in several welds Reactors, since significant cracking was observed in several welds of the primary circuit in some countries. Many questions arise of the primary circuit in several countries. Despite important R&D about the stress (or strain) threshold for initiation and on the crack efforts to determine the influence of the main parameters which growth rates of SCC, with significant differences depending on could affect PWSCC of alloy 182, many questions arose about the the orientation of the loading axis with regard to the dendrites. stress- (and strain-) threshold for initiation and on the crack The stress threshold for initiation was determined at the level of growth rates of SCC, with significant differences depending on 350 MPa with constant load tests on as-welded material. This the orientation of the loading axis with regard to the dendrites.
threshold was not significantly modified by a ripple loading at Moreover, because crack growth rates are sometimes extensively 360°C. The strain threshold for initiation, determined by determined using periodic unloading reloading procedures, a interrupted SSRTs for various elongations, was found to range comparison was proposed for CGRs obtained with this kind of between 1.25 and 1.5%. loading with respect CGRs values deduced from a pure static Preliminary data of crack growth rates (CGRs) at 325°C provided loading, depending on the orientation of specimens.
a dependence on (K-9)0.4 for the average values of the CGRmax. This contributing paper presents the status of EDF R&D program The strongly oriented microstructure led to faster (x 2 to 3) CGRs on the initiation and propagation of SCC in weld metal 182, with in the direction of the dendrites. The influence of a trapezoidal a particular emphasize on the influence of the loading mode.
loading (R = 0.7, 2.8 10-4 Hz) on CGRs depended on the orientation : no significant modification was found with respect to Materials a pure static loading in the direction TL perpendicular to the dendrites, but some significant increase (x 5 to 7) could be Two welds (D545 and D1054) in alloy 182 were investigated in observed in the direction of the dendrites TS. A stress relief the as-welded conditions : they were realized by two different treatment (610°C) could lower the CGRs by a factor 2 to 3.5 with manufacturers with SMAW process, using the same batch of respect to the as-welded condition. The results are discussed with electrodes (Soudonel CQ5, diameter 4 mm) to fill a V-shape (10°)
regard to available data from literature and compared to the mould (width 50 mm at the bottom, thickness 35 mm, length 350 background on alloy 600 : the chemical composition of the weld mm) made of alloy 600. The welding conditions were 110 A, 19 metal could lead to some variability (factor 3) in the CGRs (4 volts, temperature between weld deposition higher than 128°C.
welds with significantly different chemical compositions). The resulting weld metal consisted in a pile-up of 15 layers with 7 Tests are scheduled to account for the influences of temperature beads.
and composition of the weld metal on the stress threshold and on The chemical compositions and mechanical properties met the the crack velocities. RCC-M requirements.
Table I. Chemical composition and mechanical properties of weld metals 182 C Si Mn Ni Cr Ti Nb + Ta Fe YS20 UTS20 YS350 (MPa) (MPa) (MPa)
Requir d 0.10 d1 5.0 to ! 59 13 to 17 d1 > 1.8 6 to 10 t 250 t 550 > 190 AWS 0,6 9.5 5.11-76 max D545 0.029 0.42 7.55 bal. 14.8 0.08 2.13 7.35 395 657 353 D1054 0.026 0.35 6.20 bal 15.0 0.05 2.00 6.90 386 627 347 United States Nuclear Regulatory Commission Official Hearing Exhibit In the Matter of: Entergy Nuclear Operations, Inc.
(Indian Point Nuclear Generating Units 2 and 3)
ASLBP #: 07-858-03-LR-BD01 Docket #: 05000247 l 05000286 Exhibit #: RIV000140-00-BD01 Identified: 11/5/2015 557 Admitted: 11/5/2015 Withdrawn:
Rejected: Stricken:
Other:
Experimental procedure Tests and specimens Initiation tests. The tests were mainly performed to determine the stress and strain thresholds for SCC, they included :
x Constant load tests in order to assess a threshold stress on tensile specimens with a diameter of 4 mm and a gauge length of 25 mm. Most of the results obtained on weld D545 were previously reported in [1,2].
x Constant extension rate tests (SSRTs, 5 10-8 s-1) on tensile specimens with a diameter of 4 mm and a gauge length of 85 mm, cut in the weld D1054. They were interrupted after various elongations in order to provide a threshold strain, most suitable for application to components in plants.
x Periodic unloading-reloading at R = 0.9 every hour (frequency 2.8 10-4 Hz), on tensile specimens with a diameter of 4 mm and a gauge length of 25 mm, cut in the weld D545. They have allowed to assess the influence of a ripple load near the stress threshold defined by the previous constant load tests.
Propagation tests. The tests were performed firstly to determine Figure 2. Autoclave for SSRTs at 360°C the influence of the main mechanical and metallurgical parameters Constant load and ripple load tests were performed in a static on the CGRs, secondly to assess any influence of a periodic autoclave placed in the load line of a creep machine. The load was unloading-reloading procedure (R = 0.7, frequency 2.8 10-4 Hz, applied by dead weights to reach the maximum stress level (350 hold time 57 min) on the CGRs, with regard to the CGRs or 380 MPa), a part (10%) of the load was applied by a volume of measured with a pure static loading. CT specimens from both water admitted in a tank installed on the dead weights, at regular welds were used, thickness 15 mm, pre-cracked by fatigue in air intervals with a constant flow rate in order to reach the desired at Kfmax less than 15 MPam. They were cut in the welds trapezoidal loading (rising time 90 s, hold time 57 mn).
according to the TL orientation (fatigue pre-crack perpendicular to dendrites in a plane containing the axis of the dendrites) and the TS orientation (fatigue pre-crack in the direction of the axis of the dendrites, see Figure 1). They have allowed one to assess the influence of the orientation on the CGRs. The results were compared to previous results obtained both on CT, DCB and WOL specimens [2,5].
Figure 1. Orientation of the CT specimens in the welds Environment and facilities Figure 3. Facility for SCC tests with constant load or periodic The basic environment contained 1000 ppm B as boric acid and 2 unloading-reloading ppm Li as LiOH,H2O, with 30 cc/kg of hydrogen. The control of Propagation tests. They were performed at 325°C in an autoclave hydrogen depended on the facility and the temperature. equipped with a load line containing 4 CT specimens, mounted on Initiation tests. They were conducted in static autoclaves at a creep machine in which the load was applied by using dead 360°C, as shown in Figure 2 and Figure 3. The SSRT facility was weights (static loading) or an air-jack (trapezoidal loading, rising described with details in [3] (Figure 2), deaeration was performed time 90 s, hold time 57 mn), Figure 4. The autoclave was by evaporation of 20% of the water volume at 125°C, then constantly fed in primary water with a Cormet loop to ensure the hydrogen was introduced and controlled by a AgPd thimble at required water chemistry (conductivity and oxygen control) and 360°C. hydrogen was monitored by an Orbisphere sensor to meet a content of 30 cc/kg.
558
was noted for 1.5% elongation (Figure 5). It meant that the threshold strain ranged between 1.25 and 1.5%, which was roughly consistent with the threshold stress (350 MPa), due to the extremely severe SSRTs. For these reasons, this threshold appeared slightly lower than the value of 2% determined from capsules tests in [1].
Figure 4. Facility for SCC CGRs measurements with constant load or periodic unloading-reloading Figure 5. SC crack after an interrupted SSRT at 1.5% elongation at 360°C (weld D 1054)
Evaluation of the crack depth Influence of a ripple loading on Vth. Finally, the influence of a ripple loading (R = 0.9, 2.8 10-4 Hz) on the stress threshold was Initiation tests. During the test, a LVDT sensor allowed a record investigated at 360°C on weld metal D545. At the maximum of the elongation of the load line. The crack extension was stress of 380 MPa, a significant crack occurred after 7372 h under assessed by examination of fracture surface (optical and/or a ripple loading but the result on a pure static loading at 380 MPa scanning electron microscope). For unbroken specimen, the was not available at that time. At the maximum stress of 350 MPa, examination of the surface was realized optically. a rupture occurred by SCC after 14034 h under a ripple loading Propagation tests. The true extension of the crack was performed (Figure 6). This result was very similar to the reference result on the fracture surface (optical and/or scanning electron obtained with a pure static loading at 350 MPa (13700 h). Despite microscope), along the longest crack branch in the case of the limited number of available results, a ripple loading did not macrobranching) : it has provided maximum value ('amax), and seem to induce a significant influence on the stress threshold of mean value ('amean) of the crack depth, in the latter case after alloy 182. A definitive conclusion will be drawn with regard to measurement on 15 equally-distributed points of the crack front. the influence of a ripple loading at the end of the test at 380 MPa.
The crack growth rate (CGRmax or CGRmean) was deduced from the crack depth and from the duration of the test (generally 1300 h to 2000 h).
Results Initiation of SCC Threshold stress Vth. From previous constant load tests performed at 350°C on tensile specimens (EDF and CEA) and capsules (Framatome ANP) [1], it was deduced that for reasonable durations of tests, the stress threshold Vth for PWSCC of alloy 182 was near 350 MPa. Since that time, this assumption was reinforced by a rupture by SCC observed after 23771 h at 350 MPa on weld metal D 545 at 350°C [4]. Assuming an activation energy of 185 kJ/mol, it corresponded to a time for failure next to Figure 6. Fracture surface of specimen in weld metal D 1054 after 13700 h at 360°C, which will be the reference result in the a ripple loading at R = 0.9, 2.8 10-4 Hz at 360°C followings.
Strain threshold. In order to improve the use of such data for plant Propagation of SCC components, the threshold strain was investigated on both welds using interrupted SSRTs (5 10-8 s-1). Preliminary tests on weld Fracture surface examination. Fracture surface of PWSCC on metal D545 have demonstrated that no cracking occurred after a weld metal 182 appeared intergranular / interdendritic. The crack (plastic) elongation of 0.9%and a rupture by SCC was noted for front was uneven and a strong macro-branching at 30-45° was an elongation ranging between 3.4% and 4.9%. Complementary observed for the TL-orientation (Figure 7), while the crack front data were obtained on weld metal D1054, without any cracking was most regular and the crack propagated roughly in the plane of for 1.0 and 1.25% elongation, while a very significant cracking 559
the fatigue pre-crack for the TS-orientation (the direction of the axis of the dendrites), Figure 8.
Figure 8. SCC at 325°C : fracture surface in the TS orientation (specimen 1471-TS1, D1054 AW, 22.9 MPam, R = 0.7)
Figure 7. SCC at 325°C : fracture surface in the TL orientation (specimen TL9, D1054 AW, 41.4 MPam, R = 0.7) x CGRs measured between 310°C and 330°C were considered and re-calculated at 325°C using an activation Re-assessment of previous results : da/dt versus K. Previous CGR energy of 130 kJ/mol. This could be a reason for the data obtained by EDF, CEA and ETH-Zürich [5] with a static typical behaviour of the 3 CEA results within a narrow loading were reassessed on weld metal D545, in the TL range of K values (2 values at 330°C and one value at orientation : 310°C).
x different loading modes have been applied (constant load The mean curve for the maximum values of CGR of weld D545 as (CT) or constant deflection (WOL or DCB)). a function of the initial value of K became :
Consequently, the initial K values were re-calculated (da/d)max = 0.5114.(K-9)0.42 taking into account the anisothermal stress relaxation using K values ranging between 18 and 41 MPam (Figure 9).
between 20°C and 325°C for constant deflection tests, This K-dependence was not so far from the law reported in the roughly 18%. case of alloy 600, with the exponent between 0.3 and 0.5, see [6].
Significant data are required to better define the curve at low K values.
D54 5 & D1 054 - AW - TL - s tatic 10,00 D545 : CGRmax325 = 0,5114(K-9)^0,42 1,00 CGRmax325 (E-10 m/s ETH D545 AW TL EDF D545 AW TL CEA D545 AW TL CGRmax325 D545 AW TL EDF D1054 AW TL 0,10 0,01 0 10 20 30 40 50 60 K (MPa.m0.5)
Figure 9. Mean curve of the max. CGRs as a function of K on alloy 182 (weld D545) in the TL orientation at 325°C The new results obtained in the TL orientation with weld D1054 present results demonstrated that the orientation induced were in close agreement with these data (Figure 9) and significant changes in CGRs. The CGRs measured in the TS demonstrated a good reproducibility for tests performed at the orientation were generally higher than in the TL orientation : 2 same K-value. With the available data, the proposed law for times for D545 with a static loading, 2.5 to 3 times for D1054 PWSCC of 182 was : (da/d)max = D(material).(K-9)0.4. with a trapezoidal loading at R = 0.7.
Influence of the orientation. Though true crack lengths have been Influence of a trapezoidal loading (R = 0.7). The influence of a considered in the case of macro-branching (TL) or straight trapezoidal loading on the CGRs was examined on both welds in propagation in the direction of the axis of dendrites (TS), the the TL and TS orientations.
560
On weld D545, the data from Westinghouse [7] obtained with a the CGRs obtained with a trapezoidal loading in the TS trapezoidal loading (R = 0.7) were compared to the above- orientation were 5 to 7 times higher than the reference (TL) curve mentioned reference curve for a static loading, in the TL in static loading (Figure 10).
orientation. It could be concluded that no significant influence of .
the loading procedure was observed in the TL orientation, while D545, Static / dynamic 1 0,0 0 C GRm ax 32 5 = 0 ,5 11 4(K -9) ^0 ,4 2 1,0 0 CGR ma x3 25 (E-10 m/s)
We st A W TS R = 0.7 We st A W TL R = 0 .7 C GRma x3 25 AW TL s ta tic 0,1 0 0,0 1 0 10 20 30 40 K (M Pa.m 0.5)
Figure 10. CGRs on weld D545 : comparison between static and trapezoidal loadings On weld D1054, the CGRs were also very similar in static and in trapezoidal loading from [7] and from the present paper in the trapezoidal loading in the TL orientation, slightly higher than for TS orientation, would be in good agreement (those from [7]
weld D545 (Figure 11). By contrast, CGRs measured under a were the highest). Finally, it seemed that the influence of trapezoidal loading with the TS orientation were 3 to 5 times trapezoidal versus static loading on the SCC CGRs of alloy 182 higher than those deduced from the reference (TL) curve. depended on the orientation : no significant influence in the TL Unfortunately, the data for the TS orientation with a pure static orientation, but a detrimental factor 2 to 7 could be observed loading was not yet available, but it could be expected from the with the TS orientation.
available CGRs on the two (similar) welds that data with a 10 D 1054-TS D1054-TL 1
CGR ma x325 (E-10 m/s)
D545 AW TL static D545-TL D1054 AW TS R 0,7 D1054 AW TL R 0 ,7 D1054 AW TL static 0 ,1 0,01 0 10 20 30 40 50 60 K (MPa.m0.5)
Figure 11. CGRs on weld D1054 : comparison between static and trapezoidal loadings Influence of the stress relief treatment. The CGRs obtained at 325°C with welds D545 under a static loading and D1054 under Discussion a trapezoidal loading in the stress-relief condition (610°C-20 h) were 2 times lower than the CGRs measured in the as-welded Some comparisons could be realized with available data in condition (at the limit of the scatterband for reproducibility but relation to the influence of some major parameters on PWSCC always in the lowest part). of alloy 182.
561
set of international average values from different welds, at 75%
Comparison of da/dt versus K curves between laboratories of the cumulative distribution ((da/dt)ave325 = 1.5 10-12.K1.6), with static or trapezoidal loadings. By contrast, the proposed The K-dependence of CGRs was investigated by several reference curve in this paper has assumed a KISCC value of 9 laboratories. The Figure 12 compares the da/dt versus K MPam, and the proposed law ((da/d)max = 0.5114.(K-9)0.42 for curves proposed by EPRI and the preliminary reference curve welds D545 or D1054) for a pure static loading was rather proposed in this paper. It should be remind that EPRI-MRP 115 similar to the law proposed for alloy 600 [6].
curve, with assumed KISCC = 0, was obtained as the best fit for a 10 D 1054-TS R 0,7 Rhingals curve :
-23 9,3 K < 25 : CGRmax325 = 7,22 10 K
-10 D1054-TL K > 25 : CGRmax325 = 6 10 1 D545 EDF AW TL static EDF on D545-TL CGRmax325 (E-10 m/s)
D1054 AW TS R 0,7 CGRmax325 = 0,5114(K-9)0,42 D1054 AW TL R 0,7 D1054 AW TL static EPRI MRP 115 132 JNES AW TS static Studsvik lab data [8]
Ringhals field data [8]
Ringhals curve TS 0,1 EPRI MRP 115 CGRave325 = 1,5 10-12 K1,6 0,01 0 10 20 30 40 50 60 K (MPa.m0.5)
Figure 12. Reference curves for weld metal 182 by EPRI, Ringhals and EDF from laboratory. Comparison with JNES results The Ringhals curve in the TS orientation presented a part with a was observed for weld metal 182 in the TL orientation while a dependence on K9.3 at K lower than 25 MPam, and a plateau significant increase could be noted with a trapezoidal loading in regime at 6 10-10 m/s at K values higher than 25.1 MPam, the most sensitive (TS) orientation.
which was consistent with EDF values on weld metal D1054 in JNES data obtained in the TS orientation at 325°C (calculated the same (TS) orientation and with a trapezoidal loading. The from 340°C) under a pure static loading ranged between EPRI results they obtained in laboratory under a static loading and and EDF curves, they referred to a law similar to (K-9)1.16, from the field [8] were in close agreement with the curve Figure 12, [11].
suggested by EDF.
Influence of the chemical composition of the weld Trapezoidal loading versus static loading In this paper, two weld metals from the same batch of electrodes It should be noted that the data generated in this paper on weld and deposited in similar processes by two different D1054 in the TS orientation with a trapezoidal loading were manufacturers have provided very similar data, as expected.
slightly higher than the EPRI-curve which should account for However, the scatter on CGR results appeared to be somewhat this kind of loading. The differences in the shape and the level of larger on weld D545 than on weld D1054. This difference could EPRI and EDF curves could be the consequence of the come from laboratory-to-laboratory test procedures, since weld differences in the loading procedures. It should be noted that D545 has been tested by 3 different laboratories and weld Tsutsumi et al [9] did not recommend the use of a trapezoidal D1054 by EDF only. On weld D545, the scatter was mainly loading to measure CGRs on weld metal 132, unless hold times observed within the K-range of 15-25 MPam, in which the higher than 105 s would be used or unless pre-cracking of the influence of K on CGRs was significant, while EDF has specimen at the beginning of the test. investigated a broader range of K (20-42 MPam) on weld This kind of conclusion was still brought on alloy 600 in D1054, for which the influence of K was the lowest.
primary water : no change in CGRs was observed on very Besides, some CGRs measured at 330°C by CEA on 3 other susceptible heats, while a significant increase of CGRs under a welds in alloy 182 with C contents ranging from 0.022% to trapezoidal loading with respect to a static loading could be 0.089%, and Si contents from 0.27% to 0.79% were found to be noted for heats with a low susceptibility to SCC [10]. Finally, it somewhat similar : calculated values of the CGRmax at 325°C was not possible to explain the reason why no similar influence were 1.4 to 1.5 10-10 m/s for high or low C low Si weld, 1.8 to 562
2.35 10-10 m/s for the high C high Si weld, and 0.75 to 4.5 10-10 m/s on weld D545 [5]. References Finally, weld to weld variability led to a factor 3 on the CGRs for the same TL orientation. 1 C. Amzallag et al, Stress Corrosion Life Assessment of 182 and 82 Welds used in PWR Components (10th International Influence of the stress relief-treatment Conference on Environmental Degradation in Nuclear Power Systems - Water Reactors, South Lake Tahoe (NV), august CGRs measured on weld metal D545 or D1054 in the SR 2001) conditions were generally 2 to 3.5 times lower than in the AW conditions in most of the laboratories (EDF, CEA, ETH-Zürich) 2 C. Amzallag et al, Stress Corrosion Life Experience of 182 at 320-330°C, just above the limit for significance according to and 82 welds in French PWRs (Contribution of Materials the reproducibility factor of 2 for this kind of tests. This slight Investigation to the Resolution of Problems Encountered on beneficial effect of SR treatment at 610°C could not be Pressurized Water Reactors, Fontevraud V, France, September explained by any significant change in the microstructure or 2002) density of dislocations [12] but could rely on some contribution of residual stresses to the true K level in the case of the AW 3 Francois Vaillant, Chedly Braham, Jean-Marie Gras, condition. It should be noted that a significant beneficial effect << Etude de la corrosion sous contrainte en milieu primaire des of SR was noted by [13] at 290°C (factor 3 to 10 in the TL alliages X-750 et X-750 modifié 19% de chrome laide de orientation). lessai de traction lente. Influence du traitement thermique >>,
For comparison, some significant beneficial influence of the SR (EDF report HT-45/PV D 736A), january 1990) treatment was observed on the resistance to the initiation of SCC in the case of highly susceptible materials (high C, high Si), the [4] << La corrosion sous contrainte des alliages de nickel dans effect was limited in the case of materials with the lowest leau haute température >>, F. Vaillant et al Editors, Reference susceptibility to SCC [1]. book, (EDF report HT-29/04/077/A, 2005)
Finally, the root causes of the major beneficial influence of SR treatment in plants rely partly on the reduction in the residual stresses which could reach 50% of the initial stresses and, in the
- 5. S. Le Hong et al, Measurements of Stress Corrosion Cracking Growth Rates in Weld Alloys 182 in Primary Water of case of initiation, on a possible recristallization of the surface PWR (10th International Conference of Environmental cold worked layer. The intrinsic influence of SR treatment on Degradation of Materials in Nuclear Power Systems - Water the initiation of SCC is low on specimens with low C and Si.
Reactors, South Lake Tahoe (NV), august 2001)
Conclusion 6 F. VAILLANT et al, Crack Growth Rates in Thick The initiation and growth of PWSCC of alloy 182 were Materials of Alloy 600 and Weld Metals of Alloy 182 in investigated with regard to the influence of the loading Laboratory Primary Water. Comparison with Field Experience parameters. (Contribution of Materials Investigation to the Resolution of The stress threshold for initiation of SCC at 360°C was found Problems Encountered on Pressurized Water Reactors, close to 350 MPa in constant load tests. With the limited Fontevraud V, France, September 2002, pp 107-116) available data, it seemed that a ripple loading did not modify this value. The strain threshold was determined by interrupted 7. John Hickling, << Materials Reliability Program. Crack SSRTs : SCC occurred for an elongation between 1.25 and Growth Rates for Evaluating Primary Water Stress Corrosion 1.5%. Cracking (PWSCC) of Alloy 82, 182 and 132 welds (MRP-Preliminary data of crack growth rates (CGR) at 325°C provided 115) (EPRI report 1006696, November 2004) a dependence on (K-9)0.4 for the average values of the CGRmax.
The strongly oriented microstructure led to faster (x 2 to 3) 8 A. Jenssen et al, A Swedish Perspective on PWSCC of Alloy CGRs in the direction of the dendrites (TS) than in the 182 (2005 International PWSCC of Alloy 600 Conference and perpendicular direction (TL). The influence on the CGRs of a Exhibit Show, Hyatt Regency Tamaya Resort, Santa Ana Pueblo trapezoidal loading (R = 0.7, 2.8 10-4 Hz) with regard to a pure (NM), 7-10 March 2005) static loading depended on the orientation : no significant modification in the direction perpendicular to the dendrites (TL), 9 K. Tsutsumi et al, SCC Growth Rate of Nickel based Alloy but some significant increase (x 2 to 7) could be observed in the 132 Weld Metal in PWR Primary Water (11th International direction of the dendrites (TS). A stress relief treatment (610°C) Conference on Environmental Degradation in Nuclear Power could lower the CGRs by a factor 2 to 3.5 with respect to the as- Systems - Water Reactors, Stevenson (WA), august 2003) welded condition. The chemical composition of the weld metal could lead to some variability in the CGRs (factor 3). 10. F. Vaillant et al, Influence of a Cyclic Loading on Crack Work is still in progress to assess the influence of temperature Growth Rates of Alloy 600 in Primary Environment : An and chemical composition of the weld on the stress threshold for Overview (11th International Conference of Environmental the initiation of SCC. For propagation, the influence of low Degradation of Materials in Nuclear Power Systems - Water values of K (less than 20 MPam) on the da/dt versus K Reactors, Stevenson (WA), august 2003) curve, temperature, stress relief treatment and chemical composition of the weld metal will be investigated. 11 Y. Yamamoto et al (JNES), Outline of Evaluation Technology for SCC Growth of Ni Base Alloys (NiSCC)
Project in Japan and Current Results in PWR Environment 563
(2005 International PWSCC of Alloy 600 Conference and Exhibit Show, Hyatt Regency Tamaya Resort, Santa Ana Pueblo (NM), 7-10 March 2005) 12 C. Cayron et al, << Etude par microscopie électronique en transmission de la microstructure de différentes nuances dalliages déposés 182 >> (Technical report CEA DTEN N° 127/2001) 13 Ruth Magdowski, Markus O. Speidel, << Stress Corrosion Crack Growth of Various Materials Exposed to Simulated PWR Water>> (Technical report ETH-Zürich, contract ND 3367-RE, april 1997) 564
Session Name: Ni-Based Alloys - I, II Session Day/Time: Thursday 8/18, 8am - noon Influence of a Cyclic Loading on the Initiation and Propagation of PWSCC in Weld Metal 182 Presenter: Thierry Couvant Name of Person Asking Question: John Hickling Affiliation of Person Asking Question: EPRI Question: You mentioned the extensive macrobranching in the T-L samples. Did you find any difference in the extent of this crack branching between specimens under static constant load and those exposed with periodic unloading?
Response: We didnt notice any difference. Additional examinations could be performed to precise this point.
Name of Person Asking Question: Jun Peng Affiliation of Person Asking Question: Babcock & Wilcox Company Question: Whereby do you check the effects of a spike in cyclic loading on da/dt (Crack Growth Rate)?
Response: No we dont.
565