Kayla J. SaxMPhil Candidate in EngineeringDepartment of Engineering, University of Cambridge

Supervised by Dr. Geoff T. Parks

Investigating the Scope for the Reduction of ADSR Accelerator Requirements Through Fuel Cycle ChoiceUniversities Nuclear Technology ForumUniversity of Huddersfield, 12 April 2011

Motivation

Motivation (Continued)

Proponents of ADSR highlight:

Proponents of ADSR highlight:

Basic ADSR Schematic

ThorEA, “Towards an Alternative Nuclear Future,” 2009

Economics of ADSRs

• Upfront capital cost of accelerator is significant.– CERN group’s Energy Amplifier accelerator

costs€160M.• A larger accelerator will require a larger

fraction of electricity produced by reactor.• Reducing accelerator requirements and

therefore cost makes ADSRs more competitive with:– Conventional reactor designs.– Other energy generation technologies.

Reducing Accelerator Requirements

• Fuel cycle choice can affect accelerator requirements.

• What does a good fuel cycle choice look like?

keff

time

1

ADSR Beam Current

• To meet the constraints of a 10 MW proton accelerator, we need k > 0.985.

Pth = 1.55 GW

k = 0.95i = 33.7 mA

k = 0.99i = 6.5 mA

Approach

• Initial Analysis:– Produce transient criticality profiles of various fuel

compositions.– Identify fuel compositions that would minimize accelerator

requirements.• Further Analysis:– Analyze fuel compositions for response to various reactor

perturbations to establish safety margin.• End goal:– Identify which fuel compositions have the potential to be

economically competitive and safe enough for commercial operation.

Initial Analysis

• Effective multiplication factor (keff):

– Neutrons produced/neutrons absorbed.

• Modification of an existing “lumped” model developed by David Coates:– Account for neutron absorption by fission

products.

Lumped Model

• 49 nuclide model.

• Simple “lumped” homogenous reactor model assuming uniform neutron flux, using average neutron cross-sections, and ignoring spatial effects.

• Boundary Conditions:

– The effects of the decay and capture mechanisms from nuclides outside of the model are not accounted for.

Actinide Evolution Pathways• The rate of change of a

nuclide population within a reactor is a function of natural decay and neutron reactions (i.e. fission, capture and (n,2n))

PuPuPuPuPuPu nnnnn 24394

),(24294

),(24194

),(24094

),(23994

),(23894

AmAmAmAm nnn 24495

),(24395

),(24295

),(24195

CmCmCm nn 24496

),(24396

),(24296

UUU nn 24092

),(23992

),(23892

)2,( nn NpNpNp nn 240

93),(239

93),(238

93

Modeled with Differential Equation

• General form:

– 49 equations are created for each of the 49 isotopes accounted for in the model.

– Fourth order Runge-Kutta numerical integration applied.

• Development of the 33 nuclide fast model described in: – Actinide Evolution and Equilibrium in Fast Thorium Reactors

David J Coates and Geoffrey T ParksAnnals of Nuclear Energy, Vol. 37, pp. 1076–1088 (2010)

lMll

kMkk

jj

iiN

N ItItIsdt

dIsItMlItMk

IsN

IsN

Accounting for Fission Product Poisoning

• Incorporates the effects of 27 fission products important to fast reactors.– Accounts for about 80% of macroscopic capture

reactions by all fission products in the equilibrium core of a large, fast reactor.

• Similar to modeling of actinides:– Uses average neutron cross-sections.

• Accounts for some decay mechanisms outside the actinide and fission product isotope set:– “Adjusted” fission product yields.

Next Steps in Initial Analysis

• Account for other parasitic effects:– Absorption by non-fuel elements.

– Leakage.

• Conduct comparative analysis of fuel compositions.

Kayla J. SaxMPhil Candidate in EngineeringDepartment of Engineering, University of Cambridge

Supervised by Dr. Geoff T. Parks

Investigating the Scope for the Reduction of ADSR Accelerator Requirements Through Fuel Cycle ChoiceUniversities Nuclear Technology ForumUniversity of Huddersfield, 12 April 2011