Modeling and experiment of fission products release and interaction with coolant for defective fuel in Light Water Reactor (LWR) Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Sha Xue, B. S. Graduate Program in Nuclear Engineering The Ohio State University 2017 Thesis Committee: Jinsuo Zhang, Advisor Marat Khafizov, Co-advisor Copyright by Sha Xue 2017 Abstract During the normal operation of light water reactor, fuel defects can reside on fuel cladding from various reason such as fuel-pellet mechanical interaction, the hydriding of the Zr clad, the grid fritting from the assembly support, the warp wire fritting with the clad and also the stress corrosion cracking (SCC). The formation of defects on fuel cladding will result water ingression to the gap and react with nuclear fuel and the cladding inner surface. The interaction of water and nuclear fuel will affect the fuel thermal properties and deteriorate the cladding by hydriding and change of oxygen potential in the fuel. The change of fuel thermal properties will decrease the thermal conductivity, lead the decrease of heat transfer coefficient which may increase the fuel melting risk. The volatile fission products and fission gas will release to the coolant through cladding defects and increase the coolant activity and the defective nuclear fuel becomes a fission product source term when reactor is under normal operation. Experimental and modeling are applied to understand the behavior of a defective fuel pin. The experimental part focuses on the dissolution test of rare earth fission products in simulated LWR coolant chemistry and the diffusion coefficient measurement of cesium iodide in simulated LWR coolant chemistry using Nuclear Magnetic Resonance (NMR) technique. Rare earth fission products significantly contribute the residual heat and large quantity of radioactivity after the core shut down or in severe accident, therefore, their ii dissolution kinetic parameters in LWR are important to reactor safety and the understanding the source terms. The solubility test of rare earth fission product species (La2O3, Nd2O3 and CeO2) in simulate LWR coolant water (1000 ppm H3BO3 and 2 ppm LiOH) under different temperatures (room temperature 23 oC, 40 oC, 60 oC and 80 oC), results show that Neodymium oxide has the largest solubility in boric acid water and cerium oxide has the lowest solubility, the addition of boric acid will significantly increase the solubility of rare earth oxide in boric acid water. The diffusion coefficient of cesium iodide in boric acid water is measured using NMR technique. The NMR Diffusion-Ordered Spectroscopy (DOSY) measurement of Cs+ in simulated LWR coolant chemistry shows the self-diffusion coefficient of Cs+ is about 3.04 × 10-11 m2/s, and shows little dependence on Cs+ concentration in the solution. The measured data is about 100 times smaller than Cs+ in free water, different solution composition, temperature difference, pH difference and also the measurement method difference may cause the difference. The cesium transport and diffusion through the fuel matrix based on a fuel oxidation model is established. MOOSE/BISON code developed by Idaho National Laboratory is used to develop the cesium release model, the oxidation model results from the developed model agree with the results in reference which validate the model development using MOOSE/BISON. The cesium release model shows the time dependent cesium release after fuel defects reside on the fuel cladding, the radioactivity release to the coolant will be significant in the long term operation. The releasing of Cs into the coolant is significant iii when the fuel-water contact area is about 5%. And the releasing of Cs into the coolant will be significant when the diffusion coefficient of Cs in the fuel matrix increases 10 times. iv Dedication Dedicated to the students at The Ohio State University v Acknowledgments I would like to first thank Prof. Zhang to offer me an opportunity to work with him in OSU. He always passes his wisdom to me during my study and research, and supports my study. I’d like to thank Prof. Khafizov and Prof. Smidts’s help to my research and guidance. I’d like to thank Boyuan Li always helping me in life and study. I’d like to thank Yixing Shen, he offers lots of help to my academic study. Furthermore I’d like to express my gratitude to Dr. Wentao Zhou, Xiang Li, Yafei Wang, Jeremy Isler, Nik Shay, Evan Wu, Dr. Yi Xie, Dr. Shaoqiang Guo, this accomplishment would not have been possible without them. Finally, thanks all of you again, my life becomes more colorful and meaningful because your appearance in my life. vi Vita 2012……………….....................B.S. Nuclear Engineering, Xi’an Jiaotong University 2012 to 2015………………….. Research assistant in Institute of Nuclear Energy Safety Technology, Chinese Academy of Sciences 2015 to present………………… Graduate Research Associate, Nuclear Engineering Program, The Ohio State University Fields of Study Major Field: Nuclear Engineering vii Table of Contents Abstract ............................................................................................................................... ii Dedication ........................................................................................................................... v Acknowledgments.............................................................................................................. vi Vita .................................................................................................................................... vii List of Tables ...................................................................................................................... x List of Figures .................................................................................................................... xi Chapter 1. Introduction ................................................................................................... 1 1.1 Review of the fission products speciation and their chemical states in UO2 fuel. 6 1.2 Nuclear fission products speciation...................................................................... 7 1.2.1 Fission products speciation and chemical states in oxide fuels. ................... 8 1.2.2 Volatile fission products species ................................................................. 10 1.2.3 High volatile fission products ..................................................................... 11 1.2.4 Semi-volatile fission products species ........................................................ 15 1.2.5 Low volatile fission products including the lanthanides and the metallic precipitates: Y, La, Ce, Pr, Nd, Pm, Sm, Zr, Tc, Ru, Nb. ......................................... 18 1.3 Jacobian-free Newton-Krylov (JFNK) methods ................................................ 22 viii 1.4 Experimental of fission product in simulated LWR coolant chemistry ............. 26 Chapter 2. Fundamental data measurement of fission product .................................... 28 2.1 Solubility measurement of lanthanide oxide (La2O3, CeO2, Nd2O3) ................. 29 2.1.1 Experimental procedures for solubility measurement of lanthanide oxide (La2O3, CeO2, Nd2O3) ............................................................................................... 31 2.1.2 Result of solubility measurement................................................................ 35 2.2 Diffusion coefficient measurement of cesium iodide (CsI) in simulated LWR coolant chemistry using NMR technique. ..................................................................... 41 2.2.1 Experimental of diffusion coefficient measurement. .................................. 44 2.2.2 Diffusion coefficient data analysis.............................................................. 45 Chapter 3. Cesium release model development............................................................ 51 3.1 Model development-fuel oxidation .................................................................... 54 3.2 Hydrogen transport in fuel cracks ...................................................................... 57 3.3 Heat generation and conduction in the fuel and clad ......................................... 59 3.4 Cesium release from the defective fuel .............................................................. 64 3.5 BISON Kernel development. ............................................................................. 68 3.6 Model validation and cesium release result ....................................................... 71 Chapter 4. Summary ..................................................................................................... 83 References ......................................................................................................................... 87 ix List of Tables Table 1 Inventories of the main fission products and actinides in oxide fuel and their expected segregation tendencies [13] ................................................................................. 9 Table 2 Solubility of RE oxides in Boric acid water in different temperatures ................ 37 Table 3 Solubility measurement of RE oxides in Boric acid water in different temperatures (1000 ppm boric acid and 2 ppm lithium hydroxide) ....................................................... 40 Table 4 Concentration verification for La and Nd ...........................................................