Project Subjects
Development of Metal Fuel Cycle Technology for Practical Application
Background and Objective
CRIEPI has been developing an innovative fast reactor fuel cycle – metal fuel cycle – where a uraniumplutonium alloy is used as fuel (metal fuel) and metallurgical processes are adopted for reprocessing (pyroprocess) and fuel-fabrication (Fig. 1). The metal fuel cycle has many advantages: high fuel burnup capability andinherent reactor safety due to high thermal conductivity of metal fuel; high proliferation-resistance due to theinseparability of plutonium in pyroprocess technology; less environmental burden due to recovery and transmutation of long-lived minor actinides (MA: Neptunium, Americium and Curium); and high cost performance of thewhole system. Global interests are focused on these distinctive features. In the United States and Asian counties
such as South Korea, China and India, the metal fuel cycle is selected as the commercial candidates of fast reactorcycle. In Japan, fuel cycle utilizing oxide fuel and aqueous reprocessing has been selected as the main concept forthe commercialization. The metal fuel cycle is determined to be a long term option because it has a potential to besuperior to the main concept but less domestic experience. The current issues in the metal fuel cycle development
are fuel irradiation tests, pyroprocessing tests with irradiated fuel, and the accumulation of demonstration data byconducting engineering-scale equipment development.

Main results
1. Irradiation tests of MA-bearing metal fuel in the fast reactor Phénix
In order to demonstrate the irradiation performance of MA -bearing metal fuel, the MA -bearing metal
fuel pins (Fig. 2) were irradiated to 100,000 MWd/t burnup in the French reactor Phénix. The fuel pins irradiatedto 25,000 MWd/t burnup, at which the fuel swelling is signiﬁcant, were examined in collaboration with Joint
Research Center - Institute for Transuranium (JRC-ITU). The examination results suggested that up to 25,000
MWd/t the irradiation performance of the MA-bearing metal fuel is equivalent to that of the MA-free metal fuel.
2. Development of engineering-scale pyroprocess equipment*
High cost performance of the pyroprocess can be attained even at a small-scale plant of a few tons peryear (t/y) capacities, which is not the case with the aqueous process. A high capacity pyroprocess plant is realized
by a parallel installation of the process equipment. The demonstration of an engineering-scale equipment of a
few t/y capacities is, therefore, a key step toward the commercialization of the pyroprocess. For the demonstration, the main process apparatuses – reduction to metal, electroreﬁning, and fuel casting – equivalent to ~1 t/ycapacity were designed and manufactured (Fig. 3). Repeated recycle tests with uranium will demonstrate theirperformances in the next year.
3. Demonstration of actinide recovery from irradiated oxide fuel by pyroprocess method
By using a pyroprocess method, uranium, plutonium and minor actinide alloys were successfully recovered from irradiated mixed oxide fuel for light water reactors (Fig. 4) in collaboration with JRC-ITU. This is theﬁrst demonstration of MA recovery, which leads to a reduction of the environmental burden of radioactive waste.

*Part of this work is the results of “Development of metal fuel cycle technology for closing FBR fuel cycle” entrusted toCRIEPI by the Ministry of Education, Culture, Sports, Science and Technology (MEXT)

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(1)

(3)

(2)

Fig. 1 Metal fuel cycle and light water reactor cycle.
Metal fuel cycle for a fast reactor is closely combined to current light water reactor cycle via
pyroprocess technologies. The main results 1, 2 and 3 correspond to the technologies (1), (2) and(3) in the ﬁgure.
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U-19Pu-10Zr
U-19Pu-10Zr
containing ≤ 5 wt.% MA

Bond sodium
U-19Pu-10Zr
Composition in wt.%
Cladding outer diameter = 6.55 mm

Fig. 2 MA-bearing metal fuel pin irradiated in the fast reactor Phénix.

(a)(b)

U

Fig. 3 Engineering-scale experimental apparatuses(a) Electrochemical reduction apparatus for conversion of oxide fuelto metals, (b) Electroreﬁning apparatus for recovery of uranium fromreduced metals.
These apparatuses enable us to demonstrate the throughput and reliability of the pyroprocess at a larger scale toward realization of theengineering-scale pyroprocess tests with irradiated fuel.

Fig. 4 Uranium metal recovered from
irradiated oxide fuel.
Uranium metal showing characteristic dendritic morphology was recovered onto theiron rod on the right hand from the reduced
oxide fuel in the crucible on the left hand.

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