Dog-Bone Studies In U-Mo-Zry-4 Miniplates Fabrication Process CNEA developments in U-Mo-Zry-4
IGORR Conference - 17 -21 November 2014 - Bariloche, Argentina Dog-Bone Studies In U-Mo-Zry-4 Miniplates Fabrication Process CNEA developments in U-Mo-Zry-4 miniplates and plates co-rolling control M. LÓPEZ1, F.R. GRIBALDO2, E.N. OLIVAR2, B. PICCHETTI1 , H. TABOADA1 1Gerencia del Ciclo de Combustible Nuclear, CAC, CNEA 2Departamento de Ensayos No Destructivos y Estructurales, CAC, CNEA Avenida General Paz 1499 - Argentina INTRODUCTION Smaller Dog Bone Thinner interdifussion layer Bigger Dog Bone Thicker interdifussion layer INTRODUCTION Low compressive stress High compressive stress 371-2394 MPa 4372-29152 MPa INTRODUCTION Low compressive stress High compressive stress 371-2394 MPa 4372-29152 MPa INTRODUCTION Low compressive stress High compressive stress 371-2394 MPa 4372-29152 MPa Smaller Dog Bone Thinner interdifussion layer Bigger Dog Bone Thicker interdifussion layer INTRODUCTION Three different experiments were tested: • co-rolling process with constant reductions (0.25 mm) • co-rolling process with constant percentage reduction (5%) • co-rolling process with a decrease reduction method (from 15% to 5%) MATERIALS & METHODS MATERIALS & METHODS Picture and frame process Coupons are cut with linear precision saw Fuel core is covered with zircalloy-4 Polish up to cloth with diamond paste UMo alloys provided by INL Assemble and TIG welding Depleted Uranium Co-rolling at 650 ºC Figure 1: Zry-4 frame and sheets. MATERIALS & METHODS 1 Reduction Steps Temperature Compressive Stress 0.25 mm 2 3 5% 15% x3 10% x2 7% x2 5% x13 20 650 ºC 371-2394 MPa Table 1: co-rolling conditions for each sample. RESULTS RESULTS: 0,25 mm reduction 4 16 8 20 12 Figure 2: X-Ray images obtained for selected steps of the co-rolling process of sample 1. RESULTS: 0,25 mm reduction 12 20 Figure 3: X-Ray images obtained for steps 12 and 20 of the co-rolling process of sample 1. RESULTS: 0,25 mm reduction Left Centre Figure 4: SEM images obtained for sample 1 of centre and edges. Mag: 200x. Right RESULTS: 0,25 mm reduction Thickness difference between centre and edges (%) Step Reduction Accumulate Reduction Core Reduction 4 3.38 % 14.19 % - 8 3.21 % 29.25 % - 12 5.72 % 45.18 % - 16 6.98 % 61.30 % - 6% - 5% - 20 16.0 % 75.31 % ~66 % 48% - 33% 57% - 56% GV Method Difference is not considerable SEM Method - - Table 2: Dog-Bone obtained for sample 1 by comparison of the center and edges Grey Value; is also shown in this table the core thickness, measured on the SEM image. RESULTS: 5% reduction 3 10 15 6 11 18 9 13 20 Figure 5: X-Ray images obtained for selected steps of the co-rolling process of sample 2. RESULTS: 5% reduction 11 20 Figure 6: X-Ray images obtained for steps 11 and 20 of the co-rolling process of sample 2. RESULTS: 5% reduction Left Centre Figure 7: SEM images obtained for sample 2 of center and edges. Mag: 200x. Right RESULTS: 5% reduction Thickness difference between centre and edges (%) Step Reduction Accumulate Reduction Core Reduction 3 4.70 % 13.22 % - - 6 1.73% 25.88 % - - 9 3.06 % 35.01 % - - 10 6.59 % 39.29 % - 11 4.60 % 42.09 % - 13 4.38 % 47.11 % - 15 3.31 % 51.02 % - - 18 5.04 % 57.91 % - - 20 2.25 % 59.59 % ~61 % 15% - 1% GV Method Difference is not considerable SEM Method - Table 3: Dog-Bone obtained for sample 2 by comparison of the center and edges Grey Value; is also shown in this table the core thickness, measured on the SEM image. RESULTS: Decreasing reductions 21 Figure 8: X-Ray image obtained for sample 3, of the final co-rolling step. RESULTS: Decreasing reductions Left Centre Figure 9: SEM images obtained for sample 3 of center and edges Mag: 90x. Right RESULTS: Decreasing reductions Thickness difference between centre and edges (%) Step Reduction Accumulate Reduction Core Reduction GV Method SEM Method 21 2.05 % 75.72% ~73% 12% - 10% 65% - 73% Table 4: Dog-Bone obtained for sample 3 by comparison of the center and edges Grey Value; is also shown in this table the core thickness, measured on the SEM image. RESULTS: Comparison 170 120 Sample 1 Sample 2 165 110 160 100 155 Grey Value Grey Value 90 80 70 135 medio min max 50 40 1400 1600 1800 2000 2200 2400 2600 2800 190 180 170 160 GV medio GV min GV max 1400 1600 1400 1500 1600 1700 1800 1900 2000 2100 Figure 10: Grey Value vs. x (horizontal shifting on the core) for each sample. 200 140 1200 1300 X (pixels) Sample 3 150 medio min max 130 X (pixels) Grey Value 145 140 60 210 150 1800 2000 2200 X (pixels) 2400 2600 2800 THEORETICAL CALCULATION THEORETICAL CALCULATION From the point of view of fabrication it is desirable to have a relationship linking the deformation rate and strength shield of each material at co-rolling temperature to assess final dimensions of plate and core without stopping each co-rolling step for X-ray checking. THEORETICAL CALCULATION a p * Lp a p * R ( R 2 e0 e f 2 ) 2 a p * R(e0 e f ) Taking into account the acting forces: e e R R 2 Figure 11: Acting forces during rolling process scheme e R 1 ap: plate width Lp: plate lenght e0, ef: initial and final thickness ∆e: e0 - ef THEORETICAL CALCULATION Rolling Force . R.en F .a. R.en .1 en1 en _ Strengh shield _ .en .a. R.en .1 e e n 1 n THEORETICAL CALCULATION Rolling Force . R.en F .a. R.en .1 en1 en _ Rolling Surface _ .en .a. R.en .1 e e n 1 n THEORETICAL CALCULATION Rolling Force . R.en F .a. R.en .1 en1 en _ _ .en .a. R.en .1 e e n 1 n Variable factor involving the friction parameter between the piece and the rollers, and the pre and post thickness THEORETICAL CALCULATION Rolling Force . R.en F .a. R.en .1 en1 en _ _ .en .a. R.en .1 e e n 1 n e R THEORETICAL CALCULATION Rolling Force . R.en F .a. R.en .1 en1 en _ Applied Power P F .vt ; vt Lp. Lp.2 _ .en .a. R.en .1 e e n 1 n THEORETICAL CALCULATION Rolling Force . R.en F .a. R.en .1 en1 en _ _ .en .a. R.en .1 e e n 1 n Applied Power P F .vt ; vt Lp. Lp.2 .en P 2 .a.R.en .1 e e n 1 n _ THEORETICAL CALCULATION Rolling Force . R.en F .a. R.en .1 en1 en _ _ .en .a. R.en .1 e e n 1 n Applied Power P F .vt ; vt Lp. Lp.2 .en P 2 .a.R.en .1 e e n 1 n _ 1 n P 2 .a.R.en .1 1 n _ en n en 1 THEORETICAL CALCULATION Cancelling common factors and taking into account en possible values it stands: en en en en U Mo U Mo Zry 4 Zry 4 Zry 4 U Mo e e e e Zry 4 0 f U Mo 0 f THEORETICAL CALCULATION Essay (1) Miniplate thickness difference (mm) (2) (3)=0.5*[(1)-(2)] (3)/(2) Core thickness Cover thickness Difference ratio difference (mm) difference (mm) 1 4,48 0,636 1,922 3,024 2 4,55 0,592 1,979 3,343 3 4,826 0,72 2,053 2,853 4 4,83 0,713 2,059 2,889 5 4,6 0,65 1,975 3,037 6 5,13 0,661 2,234 3,379 7 4,96 ST. DEVIATION: 0,731 0,218 2,114 AVERAGE: 2,892 3,060 Table 5: Experimental miniplate thickness and estimated core thicknes for each corolled miniplate. en1 en Zry4 e0 e f Zry4 en1 en U Mo e0 e f U Mo 3.06 0.22 THEORETICAL CALCULATION e MP F e MP F F 1 e0 eF Zry4 ... e e e 1 F i 1 i U Mo 0 ef MP F eF U Mo MP 0 e F 1 MP i 1 i 0 U Mo 0 F U Mo MP F e MP F 1 F i 1 i 1 f 3.06 0.22 1 e e U Mo 0 U Mo 2e0 eF e MP F e e e e 2e e MP F 0 e MP 0 1 F i 1 i 7.56 F e 1 0 U Mo eF U Mo e MP F 1 F i 1 i 6.68 1 DISCUSSION DISCUSSION • When reductions are under 5% the core thickness stays homogeneous during the co-rolling process. A disadvantage of this is that the process requires more steps to reach the desire thickness. • A new co-rolling protocol was developed in order to minimize both the Dog Bone and the number of steps. A commitment between these characteristics is obtained with decreasing percent reductions. The results obtained for this protocol shows that the final dimensions of the plate, the core thickness in particular, are not optimum for irradiation. • It can be concluded that the co-rolling process can be done with constant percent reductions: up to a 5% reduction or less are suggested. • Based on theoretical calculation, given the final product specification for both phases (and so for the miniplate) it is possible to reconstruct initial (and at any stage) length and thickness if co-rolling strategy εn is provided. Thank You! Marisol López – marlopez@cnea.gov.ar Bianca Picchetti – picchetti@cnea.gov.ar Horacio Taboada – taboada@cnea.gov.ar Fernando Gribaldo Emilio Olivar
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