Enabling Load Following Capability in MSRs

Leadership: Kathryn D. Huff, Caleb S. Brooks, Brent J. Heuser, Tomasz Kozlowski, James F. StubbinsContributors: Zhen Li, Mehmet Turkmen, Alvin Lee, Jiaqi Chen, Hoon Lee, Andrei RykhlevskiiResource Team: Melissa Rose, Lou Qualls, Matt Jessee

February, 25, 2021

MSR fission gas removal

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Flexible operation and longer lifetimes may improve cost-competitiveness of MSRs.

Removing fission gases such as xenon may enable ramp rates comparable to peaking natural gas generators.

Xenon removal may also increase fuel efficiency & lifetimes.

But online fission product removal technology needs development.

Project Objectives

MSR fission gas removal

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Flexible operation and longer lifetimes may improve cost-competitiveness of Molten Salt Reactors.

Removing fission gases such as xenon may enable ramp rates comparable to peaking natural gas generators.

Xenon removal may also increase fuel efficiency & lifetimes.

But online fission product removal technology needs development.

MSR fission gas removal

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Project Objectives

MSR fission gas removal

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● 5 Faculty● 2 Postdoctoral Scholars● 4 PhD Students

4 Tasks mirror expertise in:● two-phase flow, ● reactor multi-physics, ● fuel cycle simulation,● and nuclear materials.

Resource Team : ● ANL (Melissa Rose) ● ORNL (Lou Qualls, Matt Jessee)● INL (HPC support)

Team

MSR Fission Gas Removal

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Project Accomplishments and/or Future Plans

We demonstrated that xenon fission gas removal:

- improves MSR safety when rapidly load following

- is necessary for some (particularly thermal) MSRs to safely load follow,

- is not necessary for other (fast spectrum) MSRs to load follow,

- and dramatically improves fuel utilization in all MSRs, regardless of spectrum.

Required removal efficiency for ±20% capacity/min ramp rate depends on the particular reactor, its operations, and fuel salt type, an appropriately efficient sparger and entrainment separator can be achieved with targeted design.

After a lifetime of operation at εXe= 53.6%, load follow is attempted at EOL. Above shows keff during multiple load follow transients for various total Xe removal efficiency (εXe) over time after shutdown.

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Project Accomplishments and/or Future Plans

Fuel cycle and multiphysics analysis identified key safety considerations.

- Failure of the gas entrainment separator could introduce positive reactivity to the reactor core.

- Accordingly power reduction maneuvers should be undertaken in anticipation of a gas sparging operation.

Also, in the TAP reactor, stable vortices can form in the salt in the lower plenum. Implications for in-core moderator structures are relevant to all molten salt reactor designs. Unit cell channel (left) showing the maximum temperature location; 45° cross

section view near the Kelvin-Helmholtz (KH) instability region (right)

Water-based validation experiments.

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Project Accomplishments and/or Future Plans

CFD modeling and simulation validated with laser PIV imaging from experiments have demonstrated:

- Separation efficiency decreases as bubble diameter decreases.

- Separation efficiency increases as the gas flow rate increases.

- Model result confidence is high for small bubbles with coalescence.

Prof. Brooks team took videos of water-based and high temperature salt bubbling phenomena. The high quality videos of two-phase flow in high temperature FLiNaK may be the first of their kind.

Profiles from simulation and experiment.

MSR Fission Gas Removal

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Project Accomplishments and/or Future Plans

Experiments with FLiNaK, from ORNL and ANL, are being performed at high temperatures (500C) in a glovebox at UIUC. The salt from both sources was analyzed at ANL and UIUC.

Measurements of Xe and Kr release inform the other tasks toward sparger design.

FLiNaK at 550 C in UIUC glove box.O2: ~200-600 ppmH2O: ~4-8 ppm

FLiNaK at 500 C in pressure vessel.

MSR Fission Gas Removal

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Industry engagement:○ TransAtomic Power ceased

operations.○ Reactor-agnostic multiphysics

capabilities valuable to many vendors.

T2M Successes○ Demonstration of software

capabilities for additional MSR concepts.

○ Lab and industry collaborations on relevant MSR applications.

○ Capabilities relevant to other DOE programs.

Technology-to-Market

MSR Fission Gas Removal

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The Resource Team structure was effective, efficient, and essential to our success!

Feedback

Hofstadter’s Law always applies.

It always takes longer than you expect,even when you take into account Hofstadter's Law.

ANL Thermo-Physics Property Lab glove boxes A, B, and C. These are argon-flooded for salt handling (<10ppm oxygen, <0.5ppm water).Source: Flickr, Argonne National Lab.