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Eleodor Nichita
PhD

Associate Professor

Faculty of Energy Systems and Nuclear Science

Developing advanced computational models for nuclear reactor safety analysis and radiation dosimetry



  • PhD - Nuclear Engineering Georgia Institute of Technology, USA
  • MS - Health Physics Georgia Institute of Technology, USA
  • MS - Medical Physics McMaster University, Hamilton, Ontario
  • BS - Engineering Physics University of Bucharest, Romania

Designing a Computer Code to Calculate the Committed Dose Equivalent to Internal Organs Following the Injection of a Radiopharmaceutical

Saint John, New Brunswick May 31, 2015

35th Annual Conference of the Canadian Nuclear Society

Temperature Distribution Inside Fresh-Fuel Pins of Pressure-Tube SCWR

Helsinki, Finland March 15, 2015

7th International Symposium on Supercritical Water-Cooled Reactors

Axial Power and Coolant-Temperature Profiles for a Non-Re-entrant PT-SCWR Fuel Channel

Helsinki, Finland May 15, 2015

7th International Symposium on Supercritical Water-Cooled Reactors

Progress Towards an Accurate Lattice-Homogenization Technique for Pressure Tube Supercritical Water-Cooled Reactor Neutronic Calculations

Kyoto, Japan September 28, 2014

PHYSOR 2014 International Conference the Role of Reactor Physics Toward a Sustainable Future

Preliminary Evaluation of Coolant Void Reactivity of a Re-entrant Channel Pressure Tube Supercritical Water-Cooled Reactor

Kyoto, Japan September 28, 2014

PHYSOR 2014 International Conference on the Role of Reactor Physics Toward a Sustainable Future

Preliminary Space-Time Kinetics Simulation of a Coolant Voiding-Induced Transient for a Supercritical Water-Cooled Reactor with Re-entrant Fuel Channels

Vancouver, British Columbia August 24, 2014

19th Pacific Basin Nuclear Conference

Preliminary Comparison of Transport Codes Applied to a Second-Generation PT-SCWR Lattice

Niagara Falls, Ontario April 27, 2014

Canada-China Conference on Advanced Reactor Development 2014

Preliminary Serpent Calculations for a PT-SCWR Lattice

Berkeley, California November 6, 2013

SERPENT User Group Meeting

Preliminary Study of Dynamic Properties of a Th-Pu Pressure-Tube Supercritical Water-Cooled Reactor

Shenzhen, Guangdong, China March 3, 2013

The 6th International Symposium on Supercritical Water-Cooled Reactors

Uncertainties in Kinetics Parameters of Natural-Uranium-Fuelled CANDU Cores Introduced by Lattice Homogenization and Group Condensation

Ottawa, Ontario October 14, 2012

24th Nuclear Simulation Symposium

Burnup-Dependent Effect of Lattice-Level Homogenization and Group Condensation on Calculated Kinetics Parameters for CANDU-Type Lattices

Published in Nuclear Engineering and Design May 1, 2015
E.Nichita, D.Serghiuta & S.Podobed

Modern analysis of nuclear reactor transients uses space-time reactor kinetics methods. In the Canadian nuclear industry, safety analysis calculations use almost exclusively the Improved Quasistatic (IQS) flux factorization method. The IQS method, like all methods based on flux factorization, relies on calculating effective point kinetics parameters, which dominate the time behaviour of the flux, using adjoint-weighted integrals. The accuracy of the adjoint representation influences the accuracy of the effective kinetics parameters. Routine full core calculations are not performed using detailed models and transport theory, but rather using a cell-homogenized model and two-group diffusion theory. This work evaluates the effect of homogenization and group condensation at different burnups, for three fuel types: natural-uranium (NU) fuel, low-void reactivity (LVR) fuel and Advanced CANDU Reactor (ACR) fuel.

View more - Burnup-Dependent Effect of Lattice-Level Homogenization and Group Condensation on Calculated Kinetics Parameters for CANDU-Type Lattices

Moderator Displacers for Reducing Coolant Void Reactivity in CANDU Reactors: A Scoping Study

Published in Nuclear Technology October 13, 2016
R. Farkas & E. Nichita

When the coolant is voided in the lattice of a Canada deuterium uranium (CANDU) reactor, the net reactivity change is positive, due primarily to the fact that the coolant and moderator are separated and the coolant volume is much smaller than the moderator volume. The modest loss in moderation occurring when coolant is lost is not sufficient to offset the positive reactivity contributions of increased fast fission rate and reduced epithermal absorption. A way to achieve a negative net reactivity effect on coolant voiding is to increase the importance of moderation in the coolant by decreasing the moderator-to-coolant volume ratio. This work proposes reducing the moderator-to-coolant volume ratio in existing CANDU reactors by packing the moderator with displacers in the shape of hollow spheres in a close-packed pattern.

View more - Moderator Displacers for Reducing Coolant Void Reactivity in CANDU Reactors: A Scoping Study

Effect of Lattice-Level Homogenization and Group Condensation on Calculated Kinetics Parameters of a Natural-Uranium-Fueled Equilibrium CANDU Core

Published in Nuclear Science and Engineering October 2, 2013
Eleodor Nichita

Modern analysis of nuclear reactor transients uses space-time reactor kinetics methods. In the Canadian nuclear industry, safety analysis calculations use almost exclusively the improved quasi-static (IQS) flux factorization method. The IQS method, like all methods based on flux factorization, relies on calculating effective point-kinetics parameters, which dominate the time behaviour of the flux, using adjoint-weighted integrals. The accuracy of the adjoint representation influences the accuracy of the effective kinetics parameters. Routine full-core calculations are not performed using detailed models and transport theory, but rather using a cell-homogenized model and two-group diffusion theory. This work evaluates the effect of homogenization and group condensation on the calculated effective kinetics parameters of an equilibrium CANDU core.

View more - Effect of Lattice-Level Homogenization and Group Condensation on Calculated Kinetics Parameters of a Natural-Uranium-Fueled Equilibrium CANDU Core

Best Paper Award

American Nuclear Society January 1, 2007

Awarded at the American Nuclear Society Winter Conference in Washington DC.

Improved CANDU-Core Homogenization and Benchmark Models

NSERC Collaborative Research and Development Grant April 1, 2014

For CANDU reactors to continue to be an important contributor to the Ontario energy supply they have to satisfy ever-increasing economic and safety demands. The broad objective of this work is twofold: to develop a new, more accurate, method for calculating the neutron power distribution in a nuclear reactor by using advanced homogenization methods, and to develop detailed CANDU-specific benchmark problems to test the newly developed method, as well as other methods and codes in current use in the Canadian nuclear industry.

Study of Kinetics Characteristics of a Pressure-Tube Supercritical Water Reactor

NSERC Collaborative Research and Development Grant January 1, 2011

In order to analyze the safety attributes of the Pressure-Tube, Supercritical Water-Cooled Reactor, and design its control and safety systems, its kinetic characteristics must be assessed. This project is studying the four aspects related to the kinetics of PT-SWCR and aims to contribute to the design and analysis of the PT-SCWR Generation IV advanced reactor concept in Canada.

Professional Engineers Ontario

Canadian Nuclear Society

American Nuclear Society

Canadian Organization of Medical Physicists

American Association of Physicists in Medicine

Alpha Nu Sigma, Nuclear Science and Engineering Honour Society

  • Introduction to Nuclear Physics (NUCL 2500U)
    An introduction to nuclear and reactor physics. Topics include: elements of relativity, radioactivity, alpha, beta and gamma decay; binding energy, interaction of radiation with matter; neutron cross sections, neutron scattering and absorption; fission; fusion; neutron density and flux, neutron diffusion, diffusion equation; neutron multiplication factor and reactivity, reactor equation, four and six factor formulae, neutron flux distribution, flux flattening, nuclear energy and applications of radioisotopes in various fields.
  • Reactor Kinetics (NUCL 3820U)
    An introduction to the basic principles of nuclear reactor kinetics and nuclear reactor control. Topics include: neutron cycle; reactor period; prompt and delayed neutrons; source neutron effects; sub-critical, critical and supercritical reactor; point reactor model; thermal power and neutron power; fission product poisoning; Xenon override capability; fresh and equilibrium fuel characteristics; reactivity effects of temperature changes and coolant voiding; reactivity control; approach to critical; reactor stability; spatial flux and power distribution. Reactor simulators will be used to illustrate the key principles being taught.
  • Medical Imaging (RADI 3200U)
    The physical principles of imaging techniques with medical applications will be covered. It will be shown how the different physical phenomena can be manipulated to generate clinically relevant images. The following imaging modalities will be presented: Ultrasound, Planar X-ray, Computed Tomography, Single-Photon Emission Tomography, Positron Emission Tomography and Magnetic Resonance Imaging. General image characteristics and basic image processing techniques will also be covered. Topics in wave physics, interaction of radiation with matter and medical radioisotope production will be covered as needed.
  • Introduction to Nuclear Concepts for Engineers and Scientists (NUCL 5060U)
    The course is a fast introduction to atomic, nuclear and reactor physics for graduate students without an adequate background in these areas. Topics covered include nuclear structure, radioactivity, interaction of radiation with matter, neutron flux, neutron diffusion, nuclear reactors and reactor kinetics.
  • Modelling and Simulation Tools for Reactor Physics (Special Topics) (NUCL 5005U)
    The course covers material in an emerging area or in a subject not covered in regular offerings. This course may be taken more than once, provided the subject matter is substantially different.