Degradation of Irradiated UO2 Fuel Thermal Conductivity Calculated by FRAPCON Model Due to Porosity Evolution at High Burn-Up

Authors: B. Roostaii, H. Kazeminejad, S. Khakshournia

Abstract:

The evolution of volume porosity previously obtained by using the existing low temperature high burn-up gaseous swelling model with progressive recrystallization for UO₂ fuel is utilized to study the degradation of irradiated UO₂ thermal conductivity calculated by the FRAPCON model of thermal conductivity. A porosity correction factor is developed based on the assumption that the fuel morphology is a three-phase type, consisting of the as-fabricated pores and pores due to intergranular bubbles whitin UO₂ matrix and solid fission products. The predicted thermal conductivity demonstrates an additional degradation of 27% due to porosity formation at burn-up levels around 120 MWd/kgU which would cause an increase in the fuel temperature accordingly. Results of the calculations are compared with available data.

Keywords: Irradiation-induced recrystallization, matrix swelling, porosity evolution, UO2 thermal conductivity.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1129041

References:

[1] J. Rest, An alternative explanation for evidence that xenon depletion, pore formation, and grain subdivision begin at different local burnups, J. Nucl. Mater., vol. 277, 2000, pp. 231-238.
[2] J. Rest, A model for the effect of the progression of irradiation-induced recrystallization from initiation to completion on swelling of UO2 and U–10Mo nuclear fuels, J. Nucl. Mater., vol. 346, 2005, pp. 226–232.
[3] J. Rest, Derivation of analytical expressions for the network dislocation density, change in lattice parameter, and for the recrystallized grain size in nuclear fuels ,J. Nucl. Mater., vol. 349, 2006, pp. 150–159.
[4] J. Rest, G. Kagana, A Physical description of fission product behavior in fuels for advanced power reactors, ANL-07/24, Argonne National Lab., 2007, pp. 21-26.
[5] J. Rest, editor: Rudy J. M. Konings, Comprehen. Nucl. Mater., vol.3, 2012, pp. 579-627.
[6] J. Spino, J. Rest, W. Goll, C. T. Walker, Matrix swelling rate and cavity volume balance of UO2 fuels at high burnup, J. Nucl. Mater., vol. 346 2005, pp. 131-144.
[7] B. Roostaii, H. Kazeminejad, S. Khakshournia, Influence of porosity formation on irradiated UO2 fuel thermal conductivity at high burnup , J. Nucl. Mater., vol. 479, 2016, pp. 374-381.
[8] P.G. Lucuta, Hj. Matzke, I.J. Hastings, A pragmatic approach to modelling thermal conductivity of irradiated UO 2 fuel: review and recommendations, J. Nucl. Mater., vol. 232, 1996, pp. 166-180.
[9] K. J. Geelhood, W.G. Luscher, FRAPCON-3.5: A Computer Code for the Calculation of Steady-State, Thermal-Mechanical Behavior of Oxide Fuel Rods for High Burnup, NUREG/CR-7022, vol. 1, 2014, pp. 84.
[10] J. Rest, The DART Dispersion Analysis Research Tool: A Mechanistic Model for Predicting Fission-Product-Induced Swelling of Aluminum Dispersion Fuels, AN L-95/36, 1995, pp. 16-20.
[11] K. Ohira and N. Itagaki, Thermal Conductivity Measurementsc of High Burnup UO2 Pellet and a Benchmark Calculation of Fuel Center Temperature, proceedings pp. 541-549. Applies to UO2., In Proc. of the ANS Topical Meet. on Light Water Reactor Fuel Performance, Portland, Oregon, 1997, pp. 541–549.
[12] DL. Hagrman, GA. Reymann, MATPRO version 11-A, Handbook of materials properties for use in the analysis of light water reactor fuel rod behavior, TREENUREC-1280, Revision 3, Adv. Inorg. Chem., 1979, pp. 485-486.
[13] Martín Lemes, Alejandro Soba, Alicia Denis, An empirical formulation to describe the evolution of the high burnup structure, J. Nucl. Engin. Tech., vol. 456, 2015, pp. 174-181.
[14] Yi Cui, Shurong Ding, Zengtao Chen, Yongzhong Huo, Modifications and applications of the mechanistic gaseous swelling model for UMo fuel, J. Nucl. Mater., vol. 457, 2015, pp. 157-164.
[15] J. Spino, A. D. Stalios, H. Santa Cruz, and D. Baron, Stereological evolution of the rim structure in PWR-fuels at prolonged irradiation: Dependencies with burnup and temperature, J. Nucl. Mater., vol. 354, 2006, pp. 66-84.
[16] C.B. Lee, .G. Bang, D.H. Kim, Y.H. Jung, Development of irradiation UO2 thermal conductivity model, IAEA-TECDOC-1233, Session 6, 2001, pp. 363-371.
[17] R. Brandt, J. Neuer, Thermal conductivity and thermal radiation properties of UO2, J. Non-Equilib. Thermodyn., vol. 1, 1976, pp. 3-23.
[18] C.T. Walker, D. Staicu, M. Sheindlin, D. Papaioannou, W. Goll, F. Sontheimer, On the thermal conductivity of UO2 nuclear fuel at a high burnup of around 100 MWd/kgHM, J. Nucl. Mater., vol. 350, 2006, pp. 19-39.