@article{wormald_hawari_2022, title={Modeling fission spikes in nuclear fuel using a multigroup model of electronic energy transport}, volume={566}, ISSN={["1873-4820"]}, DOI={10.1016/j.jnucmat.2022.153797}, abstractNote={In fission based nuclear reactors the fuel is subject to an intense neutron environment that drives the fission chain reaction. Due to this process fission fragments are created with energies reaching 1 MeV/amu that lose energy primarily through inelastic interactions with the electronic structure producing electronic excitations . Subsequently, these excitations thermalize through electron-phonon interactions resulting in the formation of a high temperature thermal spike and associated pressure spike. This process promotes atomic mobility that is expected to evolve lattice defects, including the annealing of latent ion tracks. In this work, a multigroup model for electron energy transport is developed and applied to molecular dynamics simulations in the LAMMPS code to examine fission energy deposition and fission effects in nuclear fuel. This technique utilizes MCNP Monte Carlo electron transport calculations to determine the initial injection of fission energy. To provide a more predictive approach than semi-empirical two-temperature models, the electron-phonon interactions are defined to include multiphonon energy transfer as a function of atomic and electron temperature, and are evaluated from electronic structure calculations using the VASP density functional theory code and PHONON lattice dynamics code. Application of this model to fission energy deposition in uranium dioxide predicts ion track formation and fission enhanced atomic mobility behavior within reasonable agreement of experimental trends. Furthermore, simulations of fission fragment interactions with latent ion tracks demonstrate an annealing effect due to this enhanced mobility.}, journal={JOURNAL OF NUCLEAR MATERIALS}, author={Wormald, J. L. and Hawari, A. I.}, year={2022}, month={Aug} }
 @article{wormald_hawari_zerkle_2020, title={Impact of magnetic structure and thermal effects on vibrational excitations and neutron scattering in uranium mononitride}, volume={143}, ISSN={["0306-4549"]}, DOI={10.1016/j.anucene.2020.107447}, abstractNote={Uranium mononitride (UN) is a nuclear fuel material of interest in the design of advanced reactors. Phonon spectra and dispersion relations of UN in its anti-ferromagnetic and paramagnetic structures were calculated using ab initio lattice dynamics. Subsequently, the dynamic structure factors of uranium and nitrogen in UN were generated in the incoherent approximation using the phonon expansion method for inclusion in the US National ENDF/B-VIII.0 database of neutron thermal scattering law evaluations. Phonons from spin polarized density functional theory simulations demonstrate good agreement with inelastic neutron scattering measurements; however, phonons from non-spin polarized simulations deviate from experiment, indicating a previously unexplored impact of magnetism on the vibrational characteristics. An oscillatory behavior due to multi-phonon scattering, previously observed in neutron scattering experiments at low temperatures, was captured in the dynamic structure factor. Moreover, calculated dynamic structure factors at 296 K and 1200 K demonstrate that the oscillatory behavior is present at elevated temperatures.}, journal={ANNALS OF NUCLEAR ENERGY}, author={Wormald, J. L. and Hawari, A. and Zerkle, M. L.}, year={2020}, month={Aug} }
 @article{wormald_hawari_2015, title={Examination of the impact of electron-phonon coupling on fission enhanced diffusion in uranium dioxide using classical molecular dynamics}, volume={30}, ISSN={["2044-5326"]}, DOI={10.1557/jmr.2014.405}, abstractNote={Abstract}, number={9}, journal={JOURNAL OF MATERIALS RESEARCH}, author={Wormald, Jonathan L. and Hawari, Ayman I.}, year={2015}, month={May}, pages={1485–1494} }
 @inproceedings{wormald_hawari_2014, title={Exploring fission enhanced diffusion of uranium in uranium dioxide using classical molecular dynamics simulations}, DOI={10.1002/9781118889879.ch21}, abstractNote={Chapter 21 Exploring Fission Enhanced Diffusion of Uranium in Uranium Dioxide Using Classical Molecular Dynamics Simulations J. L. Wormald, J. L. WormaldSearch for more papers by this authorA. I. Hawari, A. I. HawariSearch for more papers by this author J. L. Wormald, J. L. WormaldSearch for more papers by this authorA. I. Hawari, A. I. HawariSearch for more papers by this author TMS, TMSSearch for more papers by this author Book Author(s): TMS, TMSSearch for more papers by this author First published: 24 January 2014 https://doi.org/10.1002/9781118889879.ch21 AboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onEmailFacebookTwitterLinkedInRedditWechat Summary This chapter contains sections titled: Introduction Methodology Results and Discussion Conclusion References Hj. Matzke, "Radiation Effects in Nuclear Fuels," Radiation Effects in Solids, ed. Kurt E. Sickafus, Eugene A. Kotomin, and Blas P. Uberuaga ed. (Berlin, Germany: Springer 2007), 401-420. Google Scholar Hj. Matzke, "Radiation damage in crystalline insulators, oxides and ceramic nuclear fuels," Radiation Effects, 64 (1-4) (1982), 3–33. 10.1080/00337578208222984 CASWeb of Science®Google Scholar A. Höh, and Hj. Matzke, "Fission-enhanced self-diffusion of uranium in UO2 and UC," J. Nucl. Mat., 48 (2) (1973), 157–164. 10.1016/0022-3115(73)90150-5 Web of Science®Google Scholar Hj. Matzke, "Radiation enhanced diffusion in UO2 and (U,Pu)O2," Radiation Effects, 75 (1-4) (1983), 317–325. 10.1080/00337578308224715 CASWeb of Science®Google Scholar J.F. Ziegler, M.D. Ziegler, and J. P. Biersack, "SRIM: The stopping and range of ions in matter (2010)," Nucl. Instrum. Meth. Phys. Res. B, Beam Interact. Mater. At., 268 (11-12) (2010), 1818–1823. 10.1016/j.nimb.2010.02.091 CASWeb of Science®Google Scholar D.K. Avasthi, and G.K. Mehta, Swift Heavy Ions for Materials Engineering and Nanostructuring (New Delhi, India: Capital Publishing Company, Springer 2011), 47-64. Google Scholar J.M. Harp, "Examination of Noble Fission Gas Diffusion in Uranium Dioxide Using Atomistic Simulation" (Ph.D. thesis, North Carolina State University, 2010), 39-41, 67-95. Google Scholar S.J. Plimpton, "Fast parallel algorithms for short-range molecular dynamics", J. Comp. Phys 117 (1995) 1-19. http://lammps.sandia.gov. 10.1006/jcph.1995.1039 CASWeb of Science®Google Scholar S.J. Plimpton, R. Pollock, M. Stevens, "Particle-mesh ewald and rRESPA for parallel molecular dynamics simulations," in Proc. of the Eighth SIAM Conference on Parallel Processing for Scientific Computing, Minneapolis, MN (1997). http://lammps.sandia.gov. Google Scholar I.M. Lifshitz, M.I. Kaganov, and L.V. Taratanov, "On the theory of radiation-induced changes in metals," J. Nucl. Energy A, 12 (1960), 69–78. Google Scholar M. Toulemonde, E. Paumier, and C. Dufour, "Thermal spike model in the electronic stopping power regime," Radiat. Eff. Defects Solids, 126 (1-4) (1993), 201–206. 10.1080/10420159308219709 CASWeb of Science®Google Scholar M. Toulemonde et al, "Transient thermal process in heavy ion irradiation of crystalline inorganic insulators," Nucl. Instr. and Meth. in Phys. Res. B, 166-167 (2000), 903–912. 10.1016/S0168-583X(99)00799-5 CASWeb of Science®Google Scholar M. R. P. Waligorski, R. N. Hamm, and R. Katz, "The radial distribution of dose around the path of a heavy ion in liquid water," Nucl. Tracks Meas. 11 (6) (1986), 309–319. 10.1016/1359-0189(86)90057-9 CASGoogle Scholar M. Toulemonde et al, "Experimental phenomena and thermal spike model description of ion tracks in amporphisable inorganic insulators," Matematisk-Fysiske Meddelelser 52 (2006), 263–292. Web of Science®Google Scholar T. Wiss et al, "Radiation damage in UO2 by swift heavy ions," Nucl. Instr. and Meth. in Phys. Res. B, 122 (3) (1997), 583–588. 10.1016/S0168-583X(96)00754-9 CASWeb of Science®Google Scholar A. Caro, and M. Victoria, "Ion-electron interaction in molecular dynamics cascades," Phys. Rev. B, 40 (5) (1989), 2287–2291. 10.1103/PhysRevA.40.2287 CASWeb of Science®Google Scholar D. M. Duffy, A.M. Rutherford, "Including the effects of electronic stopping and electron-ion interactions in radiation damage simulations," J. Phys. Condens. Matter, 19 (1) (2007). 10.1088/0953-8984/19/1/016207 CASWeb of Science®Google Scholar TMS 2014 Supplemental Proceedings ReferencesRelatedInformation}, booktitle={TMS 2014 Supplemental Proceedings}, author={Wormald, J. L. and Hawari, A. I.}, year={2014}, pages={155–162} }