Impact of Technology Characteristics on Transition to a Fast Reactor Fleet - PowerPoint Presentation

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Impact of Technology Characteristics on Transition to a Fast Reactor Fleet

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Argonne National LaboratoryTechnical Lead for Transition Analysis Studies for the Systems Analysis and Integration Campaign

3rd Technical Workshop on Fuel Cycle SimulationParis, France, July 9-11, 2018

EDWARD Hoffman

Bo Feng

Argonne National Laboratory

Ben Betzler, Eva Davidson, & Andy WOrrall

Oak Ridge

National

Laboratory

Overview

IntroductionStudy objectiveRepresentative SFR and MSR systems

Modeling MethodologyDescribe simplified modeling approachResults

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Study Objective

The focus of this study is on technology characteristics that are likely to be impacted by the choice of SFR or MSR

Specifically those characteristics that will have the biggest impact on the supply of and demand for fissile materialInform R&D and design choices to enable a more efficient deployment of a large fleet of fast reactors under different scenariosInform on the characteristics that will lead one technology to perform better than another and not try and predict which technology will ultimately perform better

Assess our current understanding in this area

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Fuel Cycle choice

Fast Breeder Reactors Continuously Recycling U/TRU (EG24)

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Low enriched uranium (LEU) used as need

Recycled fast reactor material utilized as soon as available

Assume only constraint is a minimum recycle time (theoretical performance)

Fast Reactors

Liquid-Fueled Molten Salt Reactor (MSR)

Solid-Fueled Sodium-Cooled Reactor (SFR)

Recycle Time

MSR - ~0 (longer times will look like SFRs)

SFR – collocated (2-3

yrs

) or centralized (7+ years)

Breeding – Breakeven through maximum practical

LEU

As Needed

Fast Reactor Fleet

Discharged

Recycle

Recycled

Modeling and Performance Measures

Because the study is focused on the impact of differences in technology characteristics and not detailed dynamic behavior of a specific scenario about the future, the modeling can be simplified

Used the DYMOND code to model a few scenariosActed as benchmark for a spreadsheet model used for rapidly modeling many scenariosBoth were useful in calibrating user input for the other modelThe performance measure chosen was how much natural uranium (NU) and enrichment (SWU) is required

No cost info, both should have similar waste without detailed designs, etc.

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Spreadsheet Modeling

MSR and SFR deployed with required startup inventory (fissile material needed at or very near deployment of new capacity)

Initially only source of fissile material is LEUMSR and SFR breeding ratio is minimum to be reactivity breakeven or higher

No additional fissile required after first fuel is recycledBreeding accounts for fissile quality difference: U-235 vs TRU (Pu-239

)For the SFR, operating under the same conditions approximately 1.3 – 1.4 atoms of U-235 is equivalent to 1.0 atoms of Pu-239

The LEU system can have a fissile breeding ratio well below 1.0, but produce sufficient Pu-239 to have the same reactivity in the recycled fuelThe LEU fuel will have significantly higher fissile (U-235) concentration than the steady-state fissile (primarily Pu-239) concentration

Material is recycled as soon as assumed possibleMSR is self-sufficient immediately (zero recycle time)

SFR requires additional fuel reloads determined by the minimum recycle timeFor excess breeding scenarios, the system automatically balances once no more LEU is required

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Spreadsheet Modeling

In order to explain the underlying behavior during transition, several examples of the fissile material flow are show for single units operating independently

IFR: SFR with a 2 year recycle time such as an Integral Fast ReactorSFR - Central: SFR with a 7 year recycle time such as a system with centralized recyclingMSR (

y.yx): MSR that requires y.y times as much inventory at startup as and SFRExamples include 1.5, 2.5, and 3.5. Further study suggest that this range for well-designed commercial MSRs and SFRs ranges from 0.4 to 2.2

The spreadsheet integrates this behavior into a single system to calculate the equivalent fissile mass balanceFor reactivity breakeven systems with no constraints on recycling other than the minimum recycle time, this gives the exact answer since they are all effectively independent units (no net flow of fissile between units)

Single Unit Examples

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Basic Fissile Material Flow

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Pu-239

eq

fissile (t/

GWe

)

Pu-239

eq

fissile (t/

GWe

)

Pu-239

eq

fissile (t/

GWe

)

Pu-239

eq

fissile (t/

GWe)

Integral Demand for a Single Unit

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For breakeven systems,

MSR: all fissile demand filled

at startup

SFR: additional fissile demand

filled for reloads based on minimum recycle timeFor breeder systems,

MSR: Excess available immediatelySFR: No excess available untilminimum recycle timeSimple constraints applied so there

is no need for complex dynamic

modeling

Also no interest in cycle by cycle

or other dynamic behavior, but

approximate integral behavior

Breakeven

Breeder

Pu-239

eq

fissile (t/

GWe

)

Pu-239 eq

fissile (t/GWe)

Results

These parametric calculations revealed 3 key technology characteristics that impact front-end requirements

Startup fissile inventory, which includes all the fissile material in and out of the core for the MSR systemsRecycle time, which determines the amount of material and timing for the SFR systems with the MSR effectively being a zero recycle time system

Net breeding rate of fissile material, which account for system losses, isotopic evolution, etc. on a reactivity equivalent basisEach of these have many important underlying design characteristic such as power density, thermal efficiency, and others that combine to produce these key characteristics

Given these uncertainties in the key characteristics that affect transition performance, it would be misleading to draw any general conclusions from the direct comparison of a few examples of specific SFR and MSR

designsAdditionally, the performance is sensitive to the assumptions about the future used in the particular transition scenario

The approach to inform on this was to calculate the Equal Performance Line (EPL) for a range of scenariosAbove the EPL, the SFR performs better and below the MSR does

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Equal Performance Line

SFR and MSR both breakeven, expand to 100 GWe in 20 years

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Equal Performance Line

SFR and MSR both breakeven, expand to 100 GWe in 20 years

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Equal Performance Line

Three cases: SFR and MSR both breakeven, SFR and MSR max Breeding, and SFR max breeding/MSR moderate breeding

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Summary

By using the dynamic systems tools as a benchmark, developed a simplified spreadsheet to run a large number of cases to study a very large design space efficientlyIdentified the most important features under a wide range of conditions

Identified where uncertainty in the current designs is most important to front end requirements to transition to a large fleetThe current range of designs being considered for MSRs and SFRs leads to a wide band of uncertainty in relative performanceSFR systems with high power densities, high breeding rates, and short recycle times are needed to minimize front end requirements for transition

MSR systems with high power densities, high breeding rates, and small fissile inventories outside of the core are needed to minimize front end requirements for transition

A simple method was developed to generate a series of curves that can compare the relative performance of MSR and SFR systemsEasily expandable to systems with more complex constraints

Requires significantly more time to model and calculate EPL

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Thank you for your attention!

ehoffman@anl.gov

Equal Performance Line

Three cases: 40 year transition

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Equal Performance Line

Three cases: 40 year transition with 2% sustained growth

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Equal Performance Line

Three cases: 20 year transition with high burnup SFR fuel

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