- Research and Development Staff at Oak Ridge National Laboratory (ORNL), Nov. 2013 - Dec. to 2019
- Reactor and Nuclear Systems Division
- Nuclear Data and Criticality Safety Group
- Lead of Artificial Intelligence (AI) core design for Transformational Challenge Reactor (TCR) program.
- Artificial Intelligence for Nuclear Data Strategic Development Technical Lead.
- ORNL technical oversight lead for the design and construction of the Fast Neutron Source (FNS) at the University of Tennessee, Knoxville (UT).
- ORNL representative for the collaboration on nuclear data research between the Institute for Radiological protection and Nuclear Safety (IRSN), France, and the US DOE Nuclear Criticality Safety Program (NCSP).
- Software product line owner for Sensitivity and Uncertainty Analysis for the SCALE Nuclear Systems Modeling and Simulation code system.
- Member of nuclear data team (9 research and development staff), responsible for the measurement, evaluation and validation of nuclear data for the international nuclear community, methods and code development for data applications, nuclear criticality safety analysis and reactor physics methods development.
- Lead for implementing advanced nuclear data processing capabilities into SHIFT- a massively parallel Monte Carlo neutron transport code for the US DOE Exascale Computing Project.
- Developed a coupling methodology between differential nuclear data analysis and integral benchmark experiments entirely using continuous energy formalism. Implemented under professional Software Quality Assurance (SQA) program; SCALE code system.
- Developed a statistical inference methodology for upper subcritical limit calculations based on correlated experimental data.
- Analyzed the feasibility of direct disposal of spent nuclear fuel in a geologic repository from a criticality safety standpoint.
Sobes’ research covers a broad spectrum of reactor physics. Research interests currently span four major areas from nuclear physics to reactor design. With a background in nuclear data, he continues to work on problems in the nuclear data pipeline with a particular interest in the application of Artificial Intelligence (AI)/ Machine Learning (ML) algorithms.
Further research projects look at how nuclear data enters radiation transport calculations and how reformulating the nuclear data representation can accelerate simulations of nuclear systems on modern heterogeneous computing architectures (HPC). Research in Sensitivity/Uncertainty (S/U) analysis methods continues to be of interest. Application of S/U methods to nuclear systems design coupled with AI/ML methods is a new area of research. Last but not least, the entire research portfolio is applied to the design and future operation of the Fast Neutron Source experimental facility proposed to be built on the UT campus.
Massachusetts Institute of Technology, PhD Nuclear Science and Engineering, Feb. 2011–Sept. 2013
Thesis: Coupled Differential and Integral Data Analysis for Improved Uncertainty Quantification of the Cu-63,65 Cross Section Evaluations.
Massachusetts Institute of Technology, BS Nuclear Science and Engineering, Sept. 2007–Feb. 2011
Thesis: Individual Pebble Temperature Peaking Factor due to Local Pebble Arrangement in a Pebble Bed Reactor Core.
OECD/NEA WPEC Subgroup 44, Founder, Chair, May 2017–Present
- Founding member and group coordinator of OECD/NEA Working Party on International Nuclear Data Evaluation Co-operation (WPEC) Subgroup 44 on "Investigation of Covariance Data in General Purpose Nuclear Data Libraries."
- Leading a group of 50 nuclear data experts from around the globe to provide guidance to the international community on methods for systematic and consistent evaluation of nuclear data uncertainty with the goal of having consistent and reliable confidence intervals in simulations of nuclear systems.
IAEA International Nuclear Data Evaluation Network (INDEN), Member, Oct. 2018–Present
- International Nuclear Data Evaluation Network with the purpose to coordinate the activities in different laboratories with the final goal of obtaining consistent evaluated data files that respect the differential data and perform well in integral experiments.
OECD/NEA WPEC Subgroup Membership, Member, Dec. 2015–Present
- Subgroups range in size from about 20 to 50 members representing most of the the 33 member countries of the NEA.
- Active member of:
- Subgroup 47 on "Use of Shielding Integral Benchmark Archive and Database for \\ Nuclear Data Validation."
- Subgroup 46 on "Efficient and Effective Use of Integral Experiments for Nuclear Data Validation."
- Subgroup 45 on "The Validation of Nuclear Data Libraries (VaNDaL) project."
- Subgroup 43 on "Code infrastructure to support a modern general nuclear database \\ (GND) structure."
- Past member of:
- Subgroup 39 on "Methods and approaches to provide feedback from nuclear and covariance data adjustment for improvement of nuclear data files."
- Subgroup 38 on "Beyond the ENDF format: A modern nuclear database structure."
- American Nuclear Society, National Member, Sept. 2010 - Present
- Technical Program Committee Chair for Nuclear Criticality Safety Division
- Education Committee Member for Nuclear Criticality Safety Division
Awards and Recognitions
Nuclear Criticality Safety Program Technical Program Review, Best Research Paper Award, Mar. 2017
"FY16 Progress in Resonance Evaluations of Ce and Gd for the NCSP" selected as the best research paper from the US DOE Nuclear Criticality Safety Program for Fiscal Year 2016.
2016 American Nuclear Society Annual Meeting, Best Research Paper Award, Jun. 2016
"Benchmarking of the Updated Resolved Resonance Region Evaluations of Copper" selected as the best research paper from the Data, Analysis and Operations in Nuclear Criticality Safety session.
Nuclear Criticality Safety Program Technical Program Review, Best Research Paper Award, Mar. 2016
"Improvements for the Cu-63,65 Resonance Evaluations for Criticality Safety Applications" selected as the best research paper from the US DOE Nuclear Criticality Safety Program for Fiscal Year 2015.
Nuclear Criticality Safety Program Technical Program Review, Best Research Paper Award, Mar. 2015
"Nuclear Data Adjustment with SAMMY Based on Integral Experiments" selected as the best research paper from the US DOE Nuclear Criticality Safety Program for Fiscal Year 2014.
Select Peer-Reviewed Journal Publications
Pevey, O Chvala, S. Davis, V. Sobes, et. al., "Genetic Algorithm Design of a Coupled Fast and Thermal Subcritical Assembly," Nuclear Science and Engineering (awaiting publication), (2019).
Leal, N. Leclaire, F. Fernex, V. Sobes, "Resonance Parameters and Covariance Evaluations for the Gadolinium Isotopes," Nuclear Data Sheets (submitted), (2019).
Brown, et al., "ENDF/B-VIII.0: The 8th Major Release of the Nuclear Reaction Data Library with CIELO-project Cross Sections, New Standards and Thermal Scattering Data," Nuclear Data Sheets, 148, (2018).
Arbanas, J. Feng, V. Sobes, et al., "Bayesian Optimization of Generalized Data," EPJ Nuclear Sci. Tech. 4, (2018).
Sobes, et al., "Application of the SAMINT Methodology to the New Cross-Section Evaluations of Cu-63 and Cu-65," European Physical Journal, 146, (2017).
Arbanas, V. Sobes, et al., "Generalized Reich-Moore R-matrix Approximation," European Physical Journal, 146, (2017).
Ducru, C. Josey, K. Dibert, V. Sobes, et al., "Kernel reconstruction methods for Doppler broadening cross section temperature interpolation by linear combination of reference temperatures cross sections," Journal of Computational Physics, Jan. (2017).
M.Alamaniotis, L.H. Tsoukalas, P.L. Lagari, V. Sobes, "Application of Artificial Neural Networks to Reliable Nuclear Data for Nonproliferation Modeling and Simulation," Int. J. Monit. Surveill. Technol. 4(4), (2016).
Sobes, L. Leal, G. Arbanas, B. Forget, "Resonance Parameter Adjustment Based on Integral Experiments," Nuclear Science and Engineering, 183(3), (2016).
Sobes, L. Leal, B. Forget, K. Guber, New Resolved Resonance Region Evaluations for Cu-63 and Cu-65 to Support Nuclear Criticality Safety Analyses,"Nuclear Data Sheets, 115, (2014).
Sobes, B. Forget, A. Kadak, "Individual Pebble Temperature Peaking Factor due to Local Pebble Arrangement in a Pebble Bed Reactor Core," Nuclear Engineering and Design, 241(1), (2011)
Select Peer-Reviewed Conference Publications
Pevey, O. Chvala, S. Davis, V. Sobes, et. al., "Current Progress on the Design of a Coupled Fast-Thermal Subcritical Assembly", Trans. Am. Nucl. Soc., 120, (2019).
Ducru, J. Liang, V. Sobes, et. al., "Embedded Monte CarloRandom Walk in Random Environment to propagateCross Section Uncertainty across the Boltzmann Transport," Int. Conf. on Math. & Comp. Methods App. to Nucl. Sci. & Eng., (2019).
Meyer, V. Sobes, B. Forget, "Improving Nuclear Data Library Predictability by Accounting for Temperature Effects Using Resonance Parameters," Trans. of Int. Conf. on Nucl. Crit. Safety, (2019).
Park, A. Tumulak, V. Sobes, W. S. Yang, et. al., "Development of Processing Tool to Generate Covariance of Multigroup Thermal Scattering Matrix," Trans. Am. Nucl. Soc., 120, (2019).
Tumulak, H. Park, V. Sobes, W. S. Yang, et. al., "Progress on the Development of Thermal Scattering Covariance Formats and Processing Tools," Trans. Am. Nucl. Soc., 120, (2019).
Perfetti, V. Sobes, et al., "SCALE Resonance Parameter Sensitivity Coefficient Calculations," Trans. Am. Nucl. Soc., 119, Nov. (2018).
Sobes, L. Leal, M. Falk, A Study of the Required Fidelity for the Representation of Angular Distributions of Elastic Scatting in the Resolved Resonance Region for Nuclear Criticality Safety Applications," Int. Conf. on Math. & Comp. Methods App. to Nucl. Sci. & Eng., (2017).
Alhajri, V. Sobes, C. Perfetti, B. Forget, "Calculating Resonance Parameter Sensitivity Coefficients in SCALE," Int. Conf. on Math. & Comp. Methods App. to Nucl. Sci. & Eng., (2017).
Ducru, C. Josey, K. Dibert, V. Sobes, et al., “Optimal temperature grid for accurate Doppler kernel reconstruction," Trans. Am. Nucl. Soc., 115, (2016).
Ducru, V. Sobes, B. Forget, K. Smith, "On Methods for Conversion of R-Matrix Resonance Parameters to Multi-pole Formalism - Numerics of Algebraic Conversion,” PHYSOR,(2016).
Ducru, C. Josey, V. Sobes, et al., "Doppler Broadening by Linear Combination of Reference Temperature Cross Sections," Trans. Am. Nucl. Soc., 113, (2015).
Sobes, B. Rearden, et al., "Upper Subcritical Calculations Based on Correlated Data," Trans. of Int. Conf. on Nucl. Crit. Safety, (2015).
Paramanova, V. Sobes, B. Forget, G. Kohse, "Radiative Capture Cross Section Measurement of Copper for EXFOR Database," Trans. Am. Nucl. Soc., 107, (2012).
Sobes, R. Macdonald, L. Leal, B. Forget, K. Guber, G. Kohse, "Thermal Total Cross Section Measurement for Cu-63 and Cu-65 at the MIT Reactor," Trans. Am. Nucl. Soc., 106, (2011).