1. A report on the ALISIA Information Day
MOLTEN SALT REACTORS
A report on the ALISIA Information Day
Geoff Parks

2. Assessment of LIquid Salts for Innovative Applications
ALISIA (2007-8)
Assessment of LIquid Salts for Innovative Applications

3. ALISIA (2007-8) WP2 Materials – Mechanics (SKODA,EVM)
WP1 Fuel Salt Chemistry (JRC-ITU)
WP2 Materials – Mechanics (SKODA,EVM)
WP3 Reactor Physics (CNRS, EDF)
WP4 Fuel Salt Clean-up (NRI)
WP5 Design and Safety (CEA)

4. MOLTEN & LIQUID SALTS High temperature coolants
Example: fluoride salts
Liquid: clean salt
Molten: fuel dissolved in the salt
Characteristics:
Melting points between 350 and 500ºC
Boiling points > 1200ºC
Physical properties similar to water
Transparent
Slightly reactive

5. POTENTIAL APPLICATIONS
Coolant in Advanced High Temperature Reactor
Coolant in Fast Breeder Reactor
Fusion reactor blanket
Fuel/coolant in Molten Salt Reactor
Shale oil recovery

6. LIQUID SALTS Example: NaF-KF-ZrF4 Excellent coolant properties:
Heat transport properties
Heat transfer properties
Very high boiling point
Potentially meet the need for a high-temperature (>700ºC) low-pressure heat-transfer liquid

7. LIQUID SALTS Can reduce equipment size and costs
Number of 1m-diameter pipes needed to transport 1000 MW(t) with a 100ºC rise in coolant temperature
Water (PWR)
Sodium (LMR)
Helium
Liquid Salt
Pressure (MPa)
15.5
0.69
7.07
Outlet Temp (ºC)
320
540
1000
Coolant Velocity (m/s) 6 75
Source C.W. Forsberg et al., ICAPP’07)

8. MOLTEN SALT REACTORS The advantages of a very good coolant
Large thermal inertia
Access to very high temperatures
Compact reactor
The advantages of a liquid fuel
A single medium for fuel and coolant
A favourable neutron balance
Flexibility in fuel selection (U/Pu, Th/U) …

9. MOLTEN SALT REACTORS The advantages of a liquid fuel (continued)
The possibility of fuel draining (safety)
On-site fuel reprocessing
Much simpler fuel (re-)fabrication
Fuel breeding capability
In a thermal spectrum (Th/U cycle)
In a fast spectrum (Th/U and U/Pu cycles)

10. MSR HISTORY
The MSRE (Molten Salt Reactor Experiment) operated successfully from 1965 to 1969
3 fuel types: 30% enriched U, pure 233U, 239Pu
A programme to design a 1000 MWe breeder reactor using the Th/U cycle was halted in 1976
Fuel salt: 71%LiF-16%BeF2-12%ThF4-0.3%UF4

11. Fluorides are better neutronically for a thermal spectrum
MSR CROSS-SECTIONS
Fluorides are better neutronically for a thermal spectrum

12. Beryllium and Lithium-7 are good neutronically
MSR CROSS-SECTIONS
Beryllium and Lithium-7 are good neutronically

13. MSR FLUX SPECTRA

14. υ : number of neutrons emitted per fission
MSR FUEL BREEDING
Number of available neutrons per fission
υ : number of neutrons emitted per fission
α : ratio between capture and fission cross-sections

15. U/Pu only viable for fast spectrum, Th/U viable for any energy
MSR FUEL BREEDING
U/Pu only viable for fast spectrum, Th/U viable for any energy

16. MSR PERFORMANCE MEASURES
Fast
Thermal
78%LiF–21.4%ThF4–0.6%UF4
Spectrum hardening improves temperature reactivity feedback
Breeding ratio > 1 in a broad range of salt channel radius
Graphite lifetime is a limiting factor (< 5 years in a hard spectrum)
Thermal spectrum minimises initial fissile inventory (U-233)

17. FAST THORIUM MSR (TMSR-NM)
Fuel Salt:
80% LiF 20% (HN)F4
Fuel Salt Volume:
20 m3
U-233 Initial Inventory: kg
Mean Operating Temperature:
900 K
Power:
2.5 GWth (1 GWe)
Core Internal Radius:
1.25 m
Core Internal Height:
2.6 m

18. MOlten Salt Actinide Recycler Transmuter (MOSART)
Fast spectrum
Transmute Pu and MA without U-Th support
Salt with high-actinide solubility
LiF: mole %
BeF: mole %
NaF: remainder
Design parameters
2400 MWth
Homogeneous core
Fission product removal cycle 300 days
Core power density ~ 80 MW/m3

19. BOWMAN SYSTEM
Charles Bowman has proposed a thermal ADS molten salt system, primarily for transmutation

20. JAPANESE AMSB

21. JAPANESE AMSB Composed of three parts
1GeV and mA proton accelerator
Single-fluid molten fluoride target/blanket
system
Heat transfer and electric power recovery
Multi-beam funneling available

22. MSR ISSUES
Most studies have been theoretical and need experimental confirmation
The behaviour of liquid salts as working fluids is complex and not yet well understood
Experimental infrastructure (analytical and integral salt loops) is currently inadequate

23. MSR MATERIALS ISSUES
MSR success depends strongly on the compatibility of the container materials with the molten salts used in primary and secondary circuits
The high temperature, salt redox potential, radiation fluence and the neutron energy spectrum pose a serious challenge for any structural alloy
A practicable system needs salt constituents that are not appreciably reduced by available structural metals and alloys whose components (Fe, Ni and Cr) can be in near equilibrium with the salt
Products of oxidation of metals by fluoride melts are quite soluble in corroding media, so passivation is precluded, and the corrosion rate depends on other factors (oxidants, thermal gradients, salt flow rate, galvanic coupling)

24. MSR MATERIALS ISSUES
MSRs use graphite as a moderator and reflector. Need material stability against radiation-induced distortion and low permeability to salt and gas ingress.
Radiation damage can lead to formation of cracks sufficiently large for salt intrusion.
Cracks and crevices in the graphite can allow Xenon-135 gas to remain in the core where it is a strong neutron absorber and will significantly reduce the breeding ratio of the reactor.
The approach taken in the MSBR programme was to seal the graphite surface with pyrocarbon. No research has been done into lowering the permeability of graphite for MSR operation since the 1970s

25. ALISIA NEXT STAGE 3-4 year focus on a feasibility demonstration of
the TMSR-NM concept (high power, low Be content salt, core outlet T > 700°C)
WP1 System Configuration
WP2 Fuel Salt Chemistry and Properties
WP3 Fuel Salt Clean-up Technology and Scheme
WP4 Materials Compatibility and Chemistry Control
WP5 Safety