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Ehud Greenspan

Professor of the Graduate School
4107 Etcheverry Hall

B.Sc. Mechanical and Nuclear Engineering, Technion, Israel, 1961
M.Sc. Nuclear Science and Engineering, Technion, Israel, 1963
Ph.D. Nuclear Science and Engineering, Cornell University, 1966

Field of Specialization: 

Nuclear Reactor Theory, Design and Analysis

Areas of Interest: 

Conception, design and analysis of advanced (primarily, Generation-IV) nuclear reactors and advanced nuclear fuel cycles. Specific objectives are: Improving the sustainability of nuclear energy by increasing the utilization of the uranium and thorium fuel resources; minimizing the amount and radiotoxicity of the nuclear waste; improving proliferation resistance of nuclear energy along with improving the safety and economics of nuclear reactors.

Current Research Focus: 

The advanced reactors and fuel cycle group is presently researching the following innovative nuclear energy systems:

Breed-and-Burn (B&B) Liquid Metal Cooled Fast Reactors

A B&B reactor is a breeder reactor that converts into fissile fuel a significant fraction of the fertile feed fuel and then fissions a significant fraction of the bred fissile fuel without fuel reprocessing. B&B reactors can offer uranium utilization that is between 50 to 120 times that of LWRs. The amount of electricity that could be generated in B&B fast reactors using the presently available depleted uranium stockpiles (nuclear “waste”) is the equivalent of between 8 to 20 centuries of the total present US demand of electricity. A couple of NEUP funded projects are presently being pursued: (1) One searches promising designs of sodium cooled fast reactor (SFR) cores made of a critical seed and a subcritical B&B blanket. Specifically, we are searching for best ways to make beneficial use of the large fraction (up to 30%) of the fission neutrons that leak out from a seed designed to effectively transmute trans-uranium elements (TRU) from LWR used nuclear fuel to drive a B&B thorium fueled blanket to generate as large a fraction of the core power as possible without exceeding the presently acceptable radiation damage level of the fuel cladding material – 200 displacements-per-atom (DPA). Results obtained so far are highly promising – the reactivity increase with burnup of the B&B blanket greatly improves the performance of the TRU transmuting seed while the excess seed neutrons enable to generate close to 50% of the core power from the blanket while fissioning 7% of the thorium without the need for reprocessing the thorium fuel. (2) The second NEUP project explores the possibility of reducing the peak radiation damage required for sustaining the breed-and-burn mode of operation in a critical B&B reactor by using innovative fuel and core designs that enable three-dimensional fuel shuffling. Whereas the minimum peak radiation damage required with 2-D shuffling exceeds 500 DPA, with 3-D shuffling it is expected to be close to 300 DPA. This may enable to reduce the time and expenses required for the development of commercial B&B reactors.

Resource-renewable BWR (RBWR) 

In an attempt to design hard spectrum BWRs to provide missions traditionally assigned to liquid metal cooled reactors – fuel sustainability or TRU transmutation with unlimited recycling, Hitachi recently developed a number of RBWR core designs. These designs feature a very tight triangular lattice and very high exit void fraction that result in an epithermal to fast neutron spectrum. These RBWR cores could fit within the pressure vessel of the already commercial Advanced Boiling Water Reactors (ABWR). Over the past few years we are collaborating with the University of Michigan and MIT in evaluating the feasibility of the Hitachi designs. This effort is being funded by Hitachi. Our evaluation resulted in concerns regarding the safety of these designs associated with the possibility of having a positive void coefficient of reactivity, a too high linear heat generation rate and insufficient safety margins. We are presently pursuing a couple of activities: (1) Collaborating with Hitachi in an attempt to resolve the discrepancy between our and their evaluations and, if necessary, to come up with revised designs the safety of which can be defended; (2) Assessing the feasibility of alternative RBWR core designs that use thorium for the primary fertile fuel instead of the depleted uranium used by Hitachi. This project is funded by NEUP. The use of thorium enables designing the RBWR cores to have negative void coefficient because the number of fission neutrons generated per neutron absorbed in 233U does not increase with the absorbed neutron energy as steeply as in case of 239Pu. As the thorium-based core design does not need to have high neutron leakage probability in order to have a negative coolant voiding reactivity effect, its active fuel length can be significantly larger than that of the depleted uranium core making it possible to greatly reduce the linear heat generation rate and increase safety margins. Results obtained so far are very encouraging. If successful, this project will open a new option for developing a sustainable nuclear energy economy that is based on the BWR technology rather than on sodium-cooled fast reactor technology.

Research projects completed within the past dozen years include: design of nuclear battery type transportable reactors for proliferation-resistant, safe and secure energy for developing countries and remote sites; study of improvement possibilities in the performance of light water reactors using hydride fuel; development of efficient approaches for transmutation of nuclear waste in molten salt and other reactors; design of highly compact fission-multiplied accelerator neutron source for medical and industrial applications; and nuclear design optimization methods development and their application.

Supported Research: 

“Fuel-Self-Sustaining Thorium Boiling Water Reactors,” funded by DOE NEUP from 10/2011 to 9/2014. Prof. Vujic is co-PI. Collaborators: University of Michigan (co-PI: Downar), MIT (co-PI: Kazimi), BNL (co-PI: Todosow)

 “Advanced Burner Reactor for TRU Transmutation with Breed & Burn Blanket for Improved Economics and Resource Utilization.” supported by DOE NEUP from 8/2012 to 8/2015. Prof. Vujic is co-PI. Collaborator: ANL (co-PI: Taiwo)

“A Pebble-Bed Breed-and-Burn Reactor”, funded by DOE NEUP from 1/2014 to 1/2016. Prof. Peterson is co-PI. Collaborator: ANL (co-PI: TK Kim)

“Technical Evaluation of the Hitachi Resource-Renewable BWR,” Supported by Hitachi on and off since 2007. In collaboration with University of Michigan (PI: Downar) and MIT (PI: Kazimi).

Selected Publications: 

S.G. Hong, E. Greenspan and Y.I. Kim, “The Encapsulated Nuclear Heat Source (ENHS) Reactor Core Design,” Nuclear Technology, 149, 22 – 48, January 2005

M. Fratoni and E. Greenspan, “Transmutation Capability of Molten Salt Reactors Fed with TRU from LWR,” Proc. Third Workshop on Advanced Reactors With Innovative Fuels - ARWIF-2005, Oak Ridge, TN, February 16-18, 2005

E. Greenspan, P. Hejzlar, H. Sekimoto, G. Toshinsky and D. Wade, "New Fuel Cycle and Fuel Management Options in Heavy Liquid Metal Cooled Reactors," Nuclear Technology, 151, 177-191, August 2005

E. Greenspan, M. Fratoni, F. Ganda, F. Ginex, D. Olander, N. Todreas, P. Diller, P. Ferroni, J. Malen, A. Romano, C. Shuffler, J. Trant, B. Petrovic and H. Garkisch, “Hydride Fuel for LWRs—Project Overview,” Nuclear Engineering and Design, 239, 1374-1405, 2009

F. Ganda and E. Greenspan, “Analysis of Reactivity Coefficients of Hydride Fuelled PWR Cores,” Nuclear Science and Engineering, 164, 1-32, January 2010

F. Ganda, J. Vujic, E. Greenspan and K.N. Leung, “Accelerator-Driven Sub-Critical Multiplier for Boron Neutron Capture Therapy,” Nuclear Technology, 172, 302-324, December 2010

M. Fratoni and E. Greenspan, “Search for Equilibrium Core Composition Methodologies for Pebble Bed Reactors,” Nuclear Science and Engineering, 166, 1-16, September 2010

M. Fratoni and E. Greenspan, “Neutronic feasibility assessment of liquid salt cooled pebble-bed reactors,” Nuclear Science and Engineering, 168, 1–22, May 2011

F. Ganda, J. Vujic and E. Greenspan, “Thorium Self Sustaining BWR Cores,” Proceedings of ICAPP’11, Nice, France, May 2-5, 2011

E. Greenspan and F. Heidet, “Energy Sustainability and Economic Stability with Breed and Burn Reactors,” Progress in Nuclear Energy, 53, 794-799, 2011

F. Heidet and E. Greenspan, “Neutron Balance Analysis for Sustainability of Breed and Burn Reactors,” Nuclear Science and Engineering, 171, 13-31, May 2012

S. Qvist and E. Greenspan, “Automated Fast Reactor Core Design using the ADOPT Code,” ICAPP-2013, Jeju Island, Korea, April 14-18, 2013

P.M. Gorman, G. Zhang, J.E. Seifried, C.R. Varela, J.L. Vujic and E. Greenspan, “The fuel-self-sustaining RBWR-Thorium core concept and parametric study results,” International Congress on the Advances in Nuclear Power Plants - ICAPP 2014, , Charlotte, North Carolina, April 6-9, 2014.

G. Zhang, A. Jolodosky, E. Greenspan and J. Vujic, “Sodium Fast Reactors with Breed-and-Burn Thorium Blanket,” Proc. of the 19th Pacific Basin Nuclear Conference (PBNC 2014), Vancouver, British Columbia, Canada, August 24-28, 2014.

S. Qvist and E. Greenspan, “An autonomous reactivity control system for fast reactor safety,” to be published in Progress in Nuclear Energy.