Liquid Fueled Reactors: Molten Salt Reactor Technology · •MSR Unfavorable economics factors (compared to PWR): –While low pressure, must have containment to protect from external

Liquid Fueled Reactors:

Molten Salt Reactor

Technology

Dr. Jess C. Gehin Lead, Reactor Technology R&D Integration Reactor and Nuclear Systems Division [email protected], 865-576-5093 Thorium Energy Conference 2011 City College of New York October 10, 2011

mailto:[email protected]

2 Managed by UT-Battelle for the U.S. Department of Energy Liquid Fueled Reactors: Molten Salt Reactor Technology

Presentation Outline

• Motivations for the use of liquid Fuels

• The three primary ORNL MSR concepts

• Performance aspects of the ORNL MSR concepts

• Experience with MSRs at ORNL (ARE, MSRE)

• New Technologies for Commercial Deployment

• Current related research and development


Motivations for Liquid Fuels

• Liquid fuels seem novel today, but as will be described in the following slides, they were not seen as being unusual in the early days of nuclear energy

• Liquid fuel uniquely allows: – Elimination of fuel fabrication processes (rather they become fuel material

preparation processes)

– Can eliminate heat transfer issues as the fuel material also serves as the coolant and therefore support high power densities

– Supports online fueling/defueling operations by pumping rather than mechanical means

– Allows on-line fuel reprocessing (although this is not required) • This is important for optimizing the use of thorium as in thermal breeders

– Potential for passive safety

• As a result, fluid-fueled reactors had a significant development effort from the 1940s to the 1970s.


Two very different schools of reactor design have

emerged since the first reactors were built. One approach,

exemplified by solid fuel reactors, holds that a reactor is

basically a mechanical plant; the ultimate rationalization is

to be sought in simplifying the heat transfer machinery.

The other approach, exemplified by liquid fuel reactors,

holds that a reactor is basically a chemical plant; the

ultimate rationalization is to be sought in simplifying the

handling and reprocessing of fuel.

At the Oak Ridge National Laboratory we have chosen to

explore the second approach to reactor development.

R.C. Briant & Alvin Weinberg, “Molten Fluorides as Power Reactor Fuels,”

Nuc. Sci. Eng, 2, 797-803 (1957).


1959 Task Force and Down Selection

• In 1959 the three fluid-fueled reactor concepts were being developed were reviewed by an AEC expert task force – Aqueous Homogenous Reactor (ORNL) – Liquid Metal Fuel Reactor (BNL)

– Molten Salt Reactor (ORNL)

• This task force ultimately resulted in the down selection to the MSR as the primary fluid-fueled reactor concept (TID-8507):

The molten salt reactor has the highest probability of achieving technical feasibility. This is largely due to the use of a solution fuel (as contrasted to a slurry fuel in the LMFR and the AHR), and the availability of a suitable container material (INOR-8)


Molten Salt Reactors Were Among the

First Successful Reactor

Demonstrations

• Molten Salt Reactors were being developed at the same time as the AHR at ORNL and the Liquid-Metal Reactor at BNL

• The first MSR was developed to support the Aircraft Nuclear Propulsion program – Initial reactor the Air Craft Reactor Experiment

provided initial technology push

– Proposed to overcome issues with solid fueled reactors at high temperatures (e.g. positive reactivity coefficient from Xenon)

– Very early demonstration of technology, operated for 100 MWh over nine days in November 1954

– Considered successful, but did have issues with leaking radioactive gases

• ANP ended in 1961, but civilian program had already been launched.

Aircraft Reactor Experiment


ORNL Matured Thorium-Fueled- MSRs

Through The Development of Three

Distinct Concepts

Single Fluid MSBR

• Mixes fissile/fertile into single salt

• Complex salt processing

• Simpler core design

• Reference MSBR concept at end of program

Two-Fluid MSBR

• Fertile/Fissile salts separate

• Simpler salt processing

• More complex core design

• Modular Design

• Ultimately dropped by ORNL

Denatured MSR

• Developed in response to mid-70s proliferation concerns

• Once-through design (no processing)

• Keeps uranium in LEU form

• Requires LEU uranium support


Mature Two-Fluid MSBR Design (1967)

Provided Graphite Element and Core

Design


Two Fluid Reactor Core Layout


1 2 3 4

Shared Salt Processing System

The Two-Fluid Reactor had a Modular

Design (4 modules x 250 MWe = 1 GWe)


The “Plumbing Problem” Resulted in

ORNL Moving to a Single Fluid

Concept

• The two-fluid design required internal blankets, which created a “plumbing problem”

• Maintaining the coolant flow channels and returns resulted in a complex design

– Note that graphite shrinks and swells during irradiation

• Developments in the late „60s provide a way to separate the fission products from thorium

• Alternative designs have been proposed to address this and advanced materials may also provide an answer. So the two-fluid system may be of interest in the future.


The Single Fluid Design (1972) was

the ORNL Reference MSBR at the end

of the MSR Program


The Single Fluid Salt Processing Has

Several Separation Steps

Uranium

Separation

Rare Earth

Thorium Sep From

Protactinium/Uranium

Pa Decay/U

Separation

Rare Earth

Separation

Gaseous Fission

Products/Nobel Metals


The Chemistry of the Separations

Processes Dictates FP/Actinide

Removal Rates

The Salt/Thorium Discard Is A Key Parameter in

Determining Thorium Utilization. The discard is

required for materials that cannot be separated

from the salt and thorium


A Recent Assessment of the MSBR

Performance Parameters

• A number of performance parameters have been evaluated for the MSR based on the historical MSBR concepts that are well documented in:

– ORNL-4528 – Two fluid MSBR

– ORNL-4541 – Single fluid MSBR

– ORNL/TM-7207 – Denatured Molten Salt Reactor

• These are vintage 1970 (1980 in case of DMSR) designs

• We have no reasonably complete “modern” MSR concept design and performance evaluation

• One would expect that with advancements that the performance would be better than 1970‟s version, but that remains to be proven.


Summary of Key MSBR Parameters

These values from MSBR design report (ORNL-4541) (note that at the

time it was assumed that the capacity factor would be 80%)


The DMSR Was Developed to Address

Proliferation Concerns of the 1970s

• Online processing is not performed (other than Kr, Xe gas removal and noble metal plate out)

• Enriched Uranium (19.75%) for startup and as feed material (to make up for limited processing)

• Operated as “once-through” system

• Lower reactor power density (no graphite replacement)

• Fueling

– Thorium added only at initial loading

– Enriched uranium added as required to maintain criticality

– U-238 added as needed to maintain denatured state

• U-238 > (6 * U-233 )+(4 * U-235 )


Summary of Key DMSR Performance

Parameters


MSRs Provide Excellent Resource

Utilization

Fission consumes ~1 tonne of fuel/GWe-yr. So

11 tonnes/GWe-yr represents a 10% utilization

of thorium. This value is primarily driven by the

salt processing, not fuel burnup.


The MSBR Project Provided Cost

Estimates along with a PWR “Yard

Stick”


Nuclear Reactor Cost Escalation Must

Account for Inflation + Other Factors

• Standard cost escalation approaches have been applied to the MSR and PWR costs from the 1972 design report.

• Escalation of 1970‟s PWR to 2010 results in a capital cost of $1350/kWe

• The inflation adjusted cost is a factor of three lower than the current nominal PWR cost of $4000/kWe

• Factors other than inflation have lead to cost increases

– Examples: Schedule, regulatory, quality, financing, ES&H, security

– Many factors that did not exist in 1970)

• Therefore, you cannot simply apply standard escalation


There are Several Qualitative

Comparisons that can be made to PWRs

• MSR favorable economics factors (compared to PWR): – High temperature can provide higher conversion efficiency

– Lower operating pressure reduces metal thicknesses, fab costs, transportation costs,

– Modular fabrication/manufacturing approaches

• MSR Unfavorable economics factors (compared to PWR): – While low pressure, must have containment to protect from external events

– Includes radiochemical plant, drain tanks, off-gas system

– Requires additional materials (graphite, high purity Li-7)

– 1970s estimate had low value of indirect costs (35%) compared with current practice (quality, regulatory, certification, etc.)

• We do not have a good estimate for MSR capital costs, but taking these considerations into account it appears to be similar to that of PWR (nominal value is $4,000/kWe), similar to original assessment

• The resulting estimate of levelized cost of electricity is expected to be comparable to that from PWR


The Successful Operation of Two MSRs at

ORNL Provided “Proof of Principle”

• Two MSRs successfully operated – ARE (9 days of operation at high temperature)

– Molten Salt Reactor Experiment (MSRE, 5 years of operation)

– A third was essentially constructed, but not operated (Air Craft Reactor Test)

• MSRE highly successful experiment involving operation of a molten salt reactor with attributes that are similar to a power reactor – Established a “proof of principle” with good operating record

– Operated on U-235 and U-233

– Identified issues for R&D program (e.g. Tritium, Tellurium attack of INOR)

– However, was not a complete demonstration (no thorium used in MSRE, no fission product removal, no power conversion system)

• ORNL proposed follow-on programs to lead to a commercial MSBR – Molten Salt Breeder Experiment and a Demonstration Reactor

ORNL MSRE


There are several new technologies that

must be introduced for deployment of

Commercial MSRs

• >5 wt%U-235 LEU fuel (needed for startup)

• U-233 as the fissile material

• The use of thorium

• Salt processing system (possibly online during operation)

• Development and deployment of a new Li-7 enrichment capability

• High temperature operation (potentially with a Brayton power conversion system)

• Off-gas handling and storage system


Salt-Cooled Reactors Use Common

Technologies as MSRs

• DOE Advanced Reactor Concepts is supporting R&D on Fluoride-Salt-Cooled High Temperature Reactors (FHRs)

• Uses solid fuel (high temperature TRISO fuel) with liquid salt coolant (FLiBe)

• Leverages past development work on MSRs regarding salt, components, and materials

• Concepts under development (large and small) and salt loop being established at ORNL

125 MWe SmAHTR Integral Salt-Cooled Reactor


Summary of Key Points

• Liquid fueled MSRs provide an innovative means to effectively utilize thorium.

• MSRs demonstrate excellent performance in terms of resource utilization (10% Th Consumption with Historical Designs) and low TRU production.

• Economics are uncertain, but based on ORNL MSBR experience costs appear to be comparable to LWRs.

• Several concepts developed by ORNL, but no modern MSR design is available. Developing such a design is important to establishing and improving performance and cost.

• Experimental systems showed promising performance – further R&D needed to move to engineering and commercial scale


For More information I suggest the

following…

• Murray W. Rosenthal, An Account of Oak Ridge Laboratory’s Thirteen Nuclear Reactors, Oak Ridge National Laboratory, ORNL/TM-2009/181, December 2009.

• R. C. Robertson, et al., Two-Fluid Molten-Salt Breeder Reactor Design Study, Oak Ridge National Laboratory, ORNL-4528 (1970).

• R. C. Robertson, et al., Conceptual Design Study of a Single-Fluid Molten-Salt Breeder Reactor, Oak Ridge National Laboratory, ORNL-4541 (1971).

• J. R. Engel, et al., Conceptual Design Characteristics of a Denatured Molten-Salt Reactor with Once-Through Fueling, Oak Ridge National Laboratory, ORNL/TM-7207 (1980).

• David E. Shropshire, GNEP Economic Analysis Working group; Global Nuclear Energy Partnership Economic Tools, Algorithms, and Methodologies Report; INL/EXT-09-15483; May 2009.

• D. E. Shropshire, K.A. Williams, et al; Advanced Fuel Cycle Cost Basis; INL/EXT-07-12107; December 2009

• U.S. AEC, Report of the Fluid Fuel Reactors Task Force to the Division of Reactor Development, TID-8507, February 1959.

• S. R. Greene, et al, Pre-Cconceptional Design of a Fluoride-Salt Cooled Small Modular Advanced High Temperature Reactor (SmAHTR), Oak Ridge National Laboratory, ORNL/TM-2010/199 (2010)

• http://www.ornl.gov/fhr - ORNL FHR webpage (currently with information from FHR workshop)

http://www.ornl.gov/fhr


Questions?

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Liquid Fueled Reactors: Molten Salt Reactor Technology · •MSR Unfavorable economics factors (compared to PWR): –While low pressure, must have containment to protect from external