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Thorium Molten Salt Nuclear Energy Synergetic System (THORIMS-NES)

Ritsuo Yoshioka (*1), Koshi Mitachi (*1) & Motoyasu Kinoshita(*1,2)

(*1) International Thorium Molten-Salt Forum

(*2)University of Tokyo

(*2):e-mail: ritsuo.yoshioka@nifty.ne.jp http://msr21.fc2web.com/English.htm

Contents

1) Introduction of International Thorium Molten-Salt Forum 2) THORIMS-NES (THORIum Molten-Salt Nuclear Energy Synegetic system)

3) Concept of MSR-FUJI 4) Design Results of MSR-FUJI 5) Conclusions

1. Introduction of International Thorium Molten-Salt Forum

International Thorium Molten-Salt Forum " International Thorium Molten-Salt Forum" is a Non-Profit-Organization, which was registered in 2008. First president was Dr. Kazuo Furukawa, and the members are researchers and engineers besides citizens, who are interested in the Molten Salt Reactor and related thorium cycles, both in Japan and foreign countries.

So far, we had 10 seminars in Japan and several international presentations.

Domestic seminar in 2012 London Conference in 2010

2.THORIMS-NES

K. Furukawa, K. Arakawa, L. B. Erbay, Y. Ito, Y. Kato, H. Kiyavitskaya, A. Lecocq, K. Mitachi, R. W. Moir, H. Numata, J. P. Pleasant, Y. Sato, Y. Shimazu, V. A. Simonenco, D. D. Sood, C. Urban, R. Yoshioka, “A Road Map for the Realization of Global-scale Thorium Breeding Fuel Cycle by Single Molten-fluoride Flow”, Energy Conversion and Management, vol. 49, p.1832, 2008

1) To satisfy huge energy demand, which is caused by world population and economy growth.

2) Excellent Safety (=No severe accident) 3) Flexibility in plant size (applicable to small to large plant) 4) Nuclear proliferation resistance (very small production of Pu) 5) Flexibility in fuel cycle ・Th resource: 3-4 times more abundant than U ・Utilization and incineration capability of Pu ・Incineration capability of Minor Actinides 6) Better economy

Best solution is Thorium Cycle with Molten Salt Fuel

Requirements for Future Nuclear Energy

Based on the following 3 principles. 1) Using Thorium, instead of U238 as fertile element 2) Using molten fluoride fuel, instead of solid fuel. 3) Separation of electric power station (MSR-FUJI) and fissile breeding facility (AMSB).

THORIMS-NES Concept (1/2)

Electric power station (MSR-FUJI)

Fissile breeding facility (AMSB)

Fission reaction produces large energy, but few neutrons

Spallation reaction produces many neutrons, but small energy

High energy proton 20-30 neutrons &

protons

neutron

2-3 neutrons

(THORIum Molten-Salt Nuclear Energy Synegetic system)

Composed of the following 3 facilities. 1) Electric power station (MSR-FUJI) 2) Fissile breeding facility (AMSB) 3) Chemical processing plant These 3 facilities are connected by molten fluoride.

THORIMS-NES Concept (2/2)

AMSB is similar to ADS (Accelerator Driven Systems). Before AMSB is developed, Pu from LWR spent fuel is used as initial fissile material for MSR.

THORIMS-NES Configuration

AMSB AMSB AMSB

(4 - 30 breeders)

Fertile salt** ThF4 7LiF BeF2

Target salt*

233UF4

(2 plants) (F.P.)

Radio-waste Plant (1 plant)

heavily safeguarded

[Breeding & Chemical Processing Center]

Dry Process. Plant LWR

Spent solid-fuel

Supplying# fuel salt

Dirty fuel salt*

very small MSR

small MSR

small MSR

large MSR

(in total 0.1-1 TWe)

Solid Fuel Cycle System Simple Molten-Salt Fuel Cycle

(*) 7LiF-BeF2-ThF4-233UF4 (**) 7LiF-BeF2-ThF4 (#) target salt* + additive 233UF4

[mini FUJI] [FUJI] [FUJI]

Chemical Process Plant

Regional Center

FREGAT

PuF3

MSR “FUJI” (for power generation) (Bird-eye view)

sub-critical no radiation damage easy heat removal no target/blanket shuffling Gas-curtain window multi-beam funneling available simpler chemical aspects

* Composed of three parts: * 1GeV & 200-300 mA proton accelerator * Single-fluid molten fluoride target/blanket system * Heat transfer and electric power recovery system

AMSB (for fissile production) AMSB(Accelerator Molten-Salt Breeding Facility)

3. Concept of MSR-FUJI

MSR (Molten Salt Reactor) MSR is a liquid-fuel reactor, which utilizes molten salt of fluoride containing thorium as fertile material and U or Pu as fissile material. MSR core is composed of fuel salt and graphite, and fuel salt is circulating. Heat of fuel salt is transferred to secondary salt through heat exchanger, and heat of secondary salt is transferred to steam generators. And its steam is used to generate electricity at turbine/generator.

FUJI design targets are as follows:

(1) Small plant to deploy widely in the world.

(2) Remove Continuous chemical processing to simplify.

(3) No graphite replacement within 30 years operation.

Concept of MSR-FUJI

MSR-FUJI and mini-FUJI

Model of MSR-FUJI Pilot plant :mini-FUJI

Unique Features of MSR(1/2)

1 No fuel failure. No radiation damage. No fuel fabrication.

2 No refueling. High load factor owing to continuous operation.

3 Self-sustaining is possible (Conversion Ratio = 1.0). High fuel economic performance.

4 Low excess reactivity. Few control rods is enough. Low danger of nuclear excursion accident.

5 High safety owing to negative fuel salt temperature reactivity coefficient.

6 Small production of Plutonium and Minor Actinide, owing to thorium cycle.

7 Fuel salt is chemically inert. Low vapor pressure. Low pressure operation at high temperature.

Unique Features of MSR(2/2)

8 Thermal efficiency is 44% owing to 700 deg.-C exit temperature.

9 Fuel salt is collected to drain tank, in case of primary loop break.

10 No danger of re-critical accident at drain tank, because there is no graphite moderator in drain tank.

11 Very few probability of severe accident. Passive cooling system is proposed, in case of long-term loss of electricity.

12 High proliferation resistance owing to high energy gamma radiation by U232.

13 Transmutation capability of recycled Pu and Minor Actinides.

14 Small sized MSR is preferable, but large sized one is possible.

1 Shut-down function To terminate fission reaction 2 Cooling function To prevent fuel failure in order to prevent

radioactivity release. 3 Containment function To mitigate large release of radioactivity

in case of accident

Same philosophy as current reactors (Stop, Cool and Contain)

At Fukushima accident in 2011, No.1 function was successful, but No.2 and No.3 were lost.

Three Safety Functions of MSR

Fukushima No.4 (March 2011)

1 Countermeasure for earthquake and tsunami is required same as LWR.

2 MSR is safe against loss of electricity or loss of core cooling, because fuel salt is cooled by passive system.

3 There is no fuel failure and no core meltdown in MSR. 4 There is no over-pressure by steam in MSR, because there is no

water within primary system. 5 There is no hydrogen explosion in MSR, because there is no

water nor zirconium within primary system. 6 Spent fuel salt is collected at tank, and cooled by passive system. 7 In any severe accidents, gaseous FPs are not released, because

gaseous FPs are always removed from fuel salt. And almost all other radioactivity is contained within fuel salt.

MSR is Safe against Fukushima?

(FP:Fission Product)

4. Design Results of MSR-FUJI

Ref) R. Yoshioka, K. Furukawa, Y. Kato, K. Mitachi, “Molten-Salt Reactor FUJI and Related Thorium Cycles”, Thorium Energy Conference, Mountain View, 2010.

Calculation Method Graphite Fuel path

( K. Mitachi, et al., “Reactor Characteristics of Molten Salt Reactor: An Approach of Solution Considering the Effect of Fuel Salt Flow,” J. AESJ , 2 , 3 , P.251(2003)in Japanese).

Burnup calculation : ORIGEN2 code

Critical calculation : SRAC2006 code (pin-cell calculation and RZ core calculation) Nuclear data library : JENDL3.3

Repeat as required.

Fuel salt circulation effect is small àStatic calculation is applicable. Important findings:

Electric output Thermal output Thermal efficiency

200 MWe 450 MW(th)

44.4%

Conversion ratio (average) 1.01

Core 1 Core 2 Core 3

r or Δr (m) 1.16 0.80 0.40

h or Δh (m) 1.23 0.70 0.40

Graphite volume fraction

0.61 0.73 0.55

keff

, CR

0 2000 4000 6000 8000 0.9

0.95

1

1.05

1.1

Effective Full Power Days [days]

Keff and Conversion Ratio

(Using U233-Th fuel)

(small-sized) FUJI-U3 Design

Self-sustaining is achieved.

Flux flattening and Low leakage(⇒High conversion ratio) are achieved by this design.

3-region Concept of FUJI-U3

Low High Low Kinf

Center Radial / Axial direction

K-infinify is controlled by changing Graphite volume fraction.

K-infinity.

Graphite/233U atom density ratio

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06

FUJI-U3 design range

Neutron flux

Assuming 75% capacity factor and chemical processing interval of 7.5 years, 1) Conversion Ratio = 1.0 (for 30 years average) ⇒Self sustaining is achieved. 2) No graphite replacement for 30 years. 3) Scaling FUJI (250 MWe) to 1 GWe plant, and compare with 1 GWe BWR.

For 30 years total: FUJI-U3 (1GWe) Relative to 1GWe BWR

Fissile requirement 7.8 t (★) 32% Pu production 4 kg 0.1%

MA (Np/Am/Cm) production 23 kg 4 %

★ Since CR is 1.0, the above 7.8 t fissile is discharged at the end of reactor life, and it can be used to the next reactor.

FUJI-U3 Design Results

Electric output 1,000 MWe Thermal output 2,272 MWt Electric output 1,000 MWe

Thermal efficiency 44.0% Reactor vesse1 Diameter / Height 9.9 m / 6.7 m

Power density 7.2 MWt/m3

(large-sized) Super-FUJI design

Large-sized FUJI is possible.

*: Initial condition

(Time behavior for 900 Effective Full Power Days)

Fissile inventory vs. Time

FUJI-Pu design (Using Pu-Th fuel)

If normalized to 1GWe with 1-year operation, FUJI-Pu can decrease 990 kg Pu-fissile, and produce 450 kg U-fissile.

(100MWe FUJI)

U-PWR MOX-FBR Th-MSR Thermal output(MWt) 3,423 3,000 2,250 MA loading(kg) 5,495 15,402 5,937 MA fraction(%) 0.5 5.0 6.7 MA transmutation(%) 35.7 31.6 84.7 MA transmutation（kg/y） 66.3 164.5 169.9

Transmutation of MA by Super-FUJI (MA:Minor Actinides:Np/Am/Cm)

Better transmutation in MSR.

GF=0.88

GF=0.67

GF=0.0

GF:Graphite Fraction in a pin-cell geometry.

Graphite Effect on Neutron Spectrum

GF=0.88 (MSBR) has typical thermal spectrum. GF=0 (no graphite moderator) has fast spectrum. GF=0.67 (FUJI) is in-between.

JENDL3.3

Breeding is possible for η>2

Since Eta is flat, 3 different spectrums are possible.

Eta Value (neutrons per one absorption) JENDL3.3

Thermal spectrum MSR with largest Graphite Fraction (0.88) can minimize fissile inventory.

Fast spectrum MSR (no graphite) can achieve breeding owing to higherη, but fissile concentration or fissile inventory becomes larger due to lower cross-section for fast neutrons.

FUJI design (GF=0.67) is in-between, still keeping CR=1.0.

These 3 different reactor designs may be applied for different purposes, owing to unique feature of U233-Th cycle.

Selection of Spectrum

1 Small sized FUJI and 1GWe super-FUJI have been studied. The 233U requirement for FUJI-U3 is 32% of BWR, Pu production is only 0.1% of BWR, and Minor Actinides production is only 4% of BWR.

2 FUJI can achieve self-sustaining (Conversion Ratio=1.0) with U233 fuel.

3 FUJI can start with Pu, from LWR reprocessed fuels, as shown in FUJI-Pu.

4 FUJI can transmute Minor Actinides.

5 Huge number of MSR can start by U233, produced in AMSB.

6 MSR can operate with U235, which is being studied.

Summary of FUJI Designs

Major R&D Concerns

1 Neutronic design No significant concerns about reactor physics model. But, nuclear cross-section measurements for isotopes of the 233U-Th cycle and the corresponding integral experiments are necessary.

2 Fuel chemistry No serious problems. But, the examination of detailed PuF3 solubility data in relation to other fission product ions is necessary.

3 Structural materials (Modified Hastelloy-N)

Tellurium-attack was solved by modified Hastelloy-N (1-2% Niobium added), and redox potential control. But, endurance tests should be performed in the miniFUJI pilot plant.

4 Core graphite Irradiation tests should be performed using a reactor. Further development to improve radiation growth of graphite is preferable.

5. Conclusions

Conclusions

1 MSR can satisfy future huge electricity demand.

2 MSR can solve plutonium issue and Minor Actinide issue.

3 MSR has high safety and high economy performance.

4 MSR can expand resource utilization beside uranium.

5 Huge nuclear industry is expected.

6 MSR can co-exist with current LWRs, by utilizing LWR’s spent Pu.

7 International cooperation is preferable.

Thank you for your attention! Any questions/comments?