Kairos Design ChallengeKick-off

Project Description

Dr. Matthew J MemmottBrigham Young University

January 24th 2020

Utah Winters…2

Why Nuclear?

• Massive Energy– 10,000,000 times chemical– 1 Uranium Pellet ( 7 gm):

• 3.5 barrels of oil• 17,000 scf natural gas• 1800 lbs coal

– Reliable• ~92% Capacity factor

– Safe– Clean – No emissions!– Medicine

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What does fission look like?4

https://www.youtube.com/watch?v=Sb9i-toCcwg

Medical Uses• Medicine• 99Mo, 131I, 133Xe, etc. – only come

from nuclear reactors!• 20M procedures a year in

US1

– Diagnostics– Cancer Treatments

• Targeted Alpha Therapy2,3

– Safe enough for kids4

– 90+% success rate– Best Isotope: 213Bi

• Only comes from 232Th

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1. http://www.world-nuclear.org/information-library/non-power-nuclear-applications/radioisotopes-research/radioisotopes-in-medicine.aspx2. Y. Li, Z. Tian, S.M. Rizvi, N. H. Bander, B.J. Allen, “In vitro and preclinical targeted alpha therapy of human prostate cancer with Bi-213 labeled J591 antibody

against the prostate specific membrane antigen”, Prostate Cancer and Prostatic Diseases, vol. 5, Issue 1, pg. 36-46, 2001.3. B. J. Allen, “Clinical Trials of Targeted Alpha Therapy for Cancer”, Reviews on Recent Clinical Trials, Vol. 3, Num. 3, pg. 185-191, September, 2008.4. N. Chevalier, N. Gross, C. Widmann, “Assessment of the chemosensitizing activity of activity of TAT-RasGAP317-326 in childhood cancers”, PLoS One, Vol.

10, Issue 3, 2015.

Targeted Alpha Therapy6

Two Nuclear Pathways

• Light Water Reactor– Modified sub reactor– Requires lots of water– Pressurized– Weapons path - Pu

• Molten Salt Reactor– No solid fuel– No high pressure– Coolant was Fl-Li-Be– No Weapons– 5-10 years operation

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Safety8

Waste9

Reduce Proliferation Risk

• Must produce (and gather) 241Pu, 239Pu, 235U, or 233U– 241Pu, 239Pu are never formed– 235U in very small amounts, rapidly fissioned– Lots of 233U, but

• 233U is mixed with 232U• 232U is active gamma emitter• Gammas ruin bombs:

– Harmful to handle– Destroy electronics

• Thorium Reactors are bad bomb makers!

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Challenges

• 50 years of catch-up– Handling– Processing– Operation

• Toxic, Rare Materials– Beryllium– Lithium– Fluorine gas (HF gas)

• Isotope production– 404 isotopes, 35 elements

• Licensing and Cost

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Utah: Center for MSR12

• Major research universities• BYU – Matthew Memmott• UofU – Mike Simpson• USU– Heng Ban

• Research • Salt handling• Chemical Separation• Isotope Separation• Materials

• Other Universities• Undergraduate Research• Internships

• Policy• Licensing

• Industries (In/Out Utah)

Kairos Power

• Interested in chemistry challenges of MSR• PB-FHR, eventually to design MSR• Solid fuel with salt cooling – slightly more

attainable in short timeframe• Operating reactor by 2030• Accidents have same chemistry as MSR• Corrosion is KEY issue!

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Mk1 PB-FHR14

Scale Drawing15

Mk1 Parameters16

Reactor Vessel (up close)17

Design Challenge – Salt Reactivity

• Why salt?– Ionic Liquid– Ion dissociation– Chemical

mechanism to prevent release (compared to strucutres)

• Downside: leaches out components!

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Problem StatementFluoride-Salt-Cooled High Temperature Reactors (FHRs) utilize stainless steels as structural alloys, and molten lithium-beryllium fluoride (flibe) as the reactor coolant. Materials reliability in the FHR is complicated due corrosion resulting from salt interactions with the containment materials. The interactions between the salt and the containment are not clear, due primarily to the separate effects that drive corrosion of the material, and the subsequent material transport throughout the primary loop of the reactor. Isolating the variables that drive this corrosion and determining their relative importance remains a challenge to design engineers.

Of particular interest is the leaching of chromium from the structural materials, and its transport throughout the primary loop of the reactor system. There are two principle driving forces for chromium transport in FHRs; electrochemical reactions based upon materials coupling, and chromium ion solubility of chromium in the salt as impacted by temperature gradients within the primary system. Corrosion in molten fluoride salts can manifest through the removal of chromium from stainless steel components, migration of the chromium in the molten salt, and retention of the chromium in graphite by forming chromium carbides. Additionally, the migration of chromium ions within the primary system is driven by the temperature dependent solubility of chromium in the salt. Leeched chromium from the structural materials (in the form of chromium fluoride) tends to dissolve in the high temperature regions of the salt where the temperature dependent chromium compound (chromium fluoride) solubility in the salt is high, and precipitate in cold regions where the chromium fluoride solubility in the salt is lower.

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Design ChallengeYour task will consist of three primary objectives, that must each be satisfied:

1) Conceptually design an experimental flow loop which is capable of both measuring the migration of chromium in the KP-FHR and to evaluate and compare the influence and impact of the two relative driving forces.

2) Using this design, develop a test matrix that would allow a nuclear reactor design team to determine the mass of chromium removed or deposited in different areas (on graphite, or in cold regions), and compare the importance of the separate corrosion mechanisms.

1) For stationary TRISO pebbles at the bottom, centerline, and top of the core, determine the mass of chromium absorbed (assuming isotropic particle absorption) and the resulting change in total neutron absorption cross section of the pebbles for a thermal neutron that results from this chromium carbide formation. Use appropriate engineering assumptions to complete the analysis. For example, you may assume that all materials in the pebbles are evenly distributed throughout the pebble volume. Any standard TRISO composition (C, SiC, and UO2) as found in common literature may be used.

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Microscopic Cross Section• Probability of interaction of neutron with matter

• 𝜎𝜎𝑖𝑖 = microscopic cross section, has units of L2

• 𝑵𝑵 = Number/atom density• 𝝆𝝆 = Mass density• 𝑵𝑵𝒂𝒂 = Avagadro’s number• 𝑨𝑨 = Atomic mass of the medium• Depends on

• Particle energy• Reaction Type

• Scattering, absorption, fission, etc.• energy-dependent macroscopic linear absorption coefficient• linear fission coefficient• linear scattering coefficient, etc.

• Medium type

𝜇𝜇𝑖𝑖 = �𝑖𝑖

= 𝑁𝑁𝜎𝜎𝑖𝑖 = 𝜎𝜎𝑖𝑖𝜌𝜌𝑁𝑁𝑎𝑎𝐴𝐴

Cross section over entire range

Cross sections for each interaction

++++= fiet σσσσσ γ

++++= pfa σσσσσ αγ

ies σσσ +=

ast σσσ +=

total cross section

absorption cross section

scattering cross section

total cross section

t = totale = elastic scattering

i = inelastic scatteringγ = radiative capture

f = fissionα= alpha (charged) particle

p = proton (charged) particle

Fast Neutron Life Cycle

• What happens to fast neutrons?

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Design Information on MK1-PB-FHR

• https://web.mit.edu/nse/pdf/researchstaff/forsberg/FHR%20Point%20Design%2014-002%20UCB.pdf

• Even more information in Liturature – Do searches for anything you need!

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Schedule

• Submit Team Members and Abstract for approval by Feb 7th

• Submit Complete Report Draft & presentation by March 16

• Finalists reported that week• March 27th Present to Kairos Panel at

Symposium

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Questions?27