PLACA3D: A THREE-DIMENSIONAL CODE TO SIMULATE THE IRRADIATION BEHAVIOUR OF DISPERSE/MONOLITHIC NUCLEAR FUEL FOR RESEARCH AND TEST REACTORS Alejandro Soba, Alicia Denis Code & Models-CNEA Argentina IGORR 2014, Bariloche, Argentina. A little of History • DIONISIO Code 1.0: Power Reactors (1997-2007) • PLACA 2D, Disperse fuel (2002-2007) • PLACA 2D, Monolithic fuel (2002-2007) • PLACA 2D, +Gap (2002-2007) …. 2010 • DIONISIO 2.0 Re engineering of the code. As part of the same structure: PLACA 2D/3D: for Disperse/Monolithic, and try the presence of gap (at the moments in 2D) Modelling in 3D Dispersed plate type fuel Monolithic plate type fuel Models included in PLACA3D Temperature distribution: The heat diffusion equation is solved in each plate material in Cartesian coordinates T T T y , j z, j x, j Hj 0 x x y y z z j thermal conductivity j=core, gap (if present), cladding H max cos( z / le ) , j fuel Hj 0 , other material Models included in PLACA3D Stress-strain: The problem is solved in each phase assuming plane strain {e} {} {th } { sw} {} { E } { P } {} D{} D material matrix; Thermal expansion; Swelling; Elastic and plastic strain Calculation procedure The termo-mechanical equations are solved by the finite element method. Hexahedrical elements with bilinear interpolation are used. Within each FE a representative unit cell is defined. Temperature and power history are assumed uniform there. In disperse fuels the unit cell contains the particle, the interaction layer, porosity and the matrix, according to the volume proportions in the material. Fission gas release is solved by the FEM in a representative spherical grain. Interaction U-Mo / Al The growth of an interaction layer between the fissile compound U-Mo and the aluminum matrix is observed. Its presence produces a significant increase of the fuel operation temperature and swelling, which may lead to plate failure. The interaction layer growth is a diffusion controlled process, which depends on the surface-volume relation of the fuel particles with respect to the matrix. Interaction U-Mo / Al (U-Mo)Al4.4 (U-Mo)Al3 ClU/ a ClAl /a U-Mo a/l ClAl /m Ci Di n Ci r n t r r r ClU/ m layer Al l / m The concentration profiles of U(Mo) and Al obey n=0 rectangular, n=2 spherical symmetry Interaction U-Mo / Al Two moving boundary equations: Al C d a / l Al l (ClAl ) D /a l dt r U C dl / m U l Cl / m DlU dt r DlU , DlAl a / l l / m interdiffusion coefficients of U and Al in the interaction layer Interaction U-Mo / Al +Si 0 wt% Si 0.2 wt% Si 0.5 wt% Si 1 wt% Si 2 wt% Si 4 wt% Si 6 wt% Si 14 12 10 8 14 6 Ideal Case IL size 12 10 4 Numerical IL size Model of IL grow included in PLACA3D. Comparison with experiments. 2 Low Si Zone 8 6 High Burnup Zone 4 2 0 0 0 20 40 60 235 Rich Si Zone 0 Y 2 A%wtSi B(burnup) f0.75 1.625 - %wtMo6.25 exp 9600 1.96T %wtSi %wtSi %wtSi A%wtSi 0.68 exp 1.69 exp 0.024 exp 0.327 0.14 8.71E 12 B(Burnup) 0.274 exp(0.0813 * burnup) Burnup ( U) 2 4 6 8 Measured 80 10 12 14 Results (cont) E Ideal Case FUTURE & EFUTURE IRIS & IRIS.TUM RERTR3 & RERTR5 1,0 Numerical 0,8 +0.1 -0.1 vol% Al vol% Compound vol% Intermetallic 0,6 0,4 0,2 0,0 0,0 0,2 0,4 0,6 Measured 0,8 1,0 Experiment: IRISx, IRIS-TUM, FUTURE, EFUTURE, RERTR3 & RERTR5 Results (cont) 500 T (°K) 450 T sup (°K) T Central (°K) (Exp) T cen Efut 4 (Exp) T cen Efut 6 PLACA T cen Efut 4 PLACA T cen Efut 6 0 10 20 30 40 50 time (days) 60 +5% Ideal Case 500 -5% 70 80 Numerical 400 Simulation with PLACA3D of the experiment EFUTURE 400 400 500 Measured Results (cont) 20 15 Numerical Ideal Case FUTURE IRIS RERTR-3 RERTR-5 +20% -20% 10 5 0 0 5 10 Measured 15 20 Simulation with PLACA3D IL size Conclusions The results obtained with PLACA3D are in good agreement with the PIE data of the experiments FUTURE, IRIS-x, E-FUTURE and RERTR-3-4-5-6. The modular structure of PLACA3D allows testing and replacement of the models included. The inter diffusion model included in PLACA3D, that solves a double Stefan problem, gives to the code a realistic tool. The consumption of fuel particles and matrix is strongly dependent on the longitudinal position of each finite element, i.e., on the power history and the consequent temperature distribution. PLACA3D: A THREE-DIMENSIONAL CODE TO SIMULATE THE IRRADIATION BEHAVIOUR OF DISPERSE/MONOLITHIC NUCLEAR FUEL FOR RESEARCH AND TEST REACTORS Thanks you!

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