Scientific & Technical Development for Nuclear Nonproliferation                
2.52.0UO2 (pellet type, 75% T.D.)

Oxide electrowinning(Pyrochemical process)Washing
Milling

Molten salt

5 fractions (μm)(1) 1000〜630(2) 630〜400(3) 400〜250 Mixing(4) 250〜100(5) 100〜+Oxygen getterλ / Wm-1K-1

After mixing feed
into a cleadding＋

MOX deposit

UO2 compacts containing U(with melting of U)

MOX granulate−1.51.0
UO2 compacts containing U(without melting of U)

UO2 compacts
0.5
Vibro-packing

0.0
800

900

Screening

1000

1100

1200

1300

1400

T/K
    
After melting Plutonium (Pu) and Uranium (U) chloride in hightemperature crucible, Pu and U are oxidized and precipitatedon electrodes by electrowinning into MOX granulate. A “Vipacfuel pin” is filled with high density fuel by vibro-packing. Thismethod is cheaper than existing pellet fuel methods because ofthe compact facility and simple fuel fabrication process.
Additionally it is more practical because the easy operation canbe done remotely, for less radiation exposure during fuelfabrication.

     

In vipac fuels for FBR, a fuel restructuring phenomena similar
to the ones seen in pellet type fuels occurs in high temperature
regions during irradiation. However, in the low temperature
regions below 1300K, such as the peripheral area of the fuel,no effective restructuring would occur, and granular fuelcompact morphology remains as fabricated. The thermal
conductivities of those regions are lower than pellet type fuels
due to the morphology. However, adding some U particles togranular fuel compacts improves thermal conductivity of thevipac fuel, thus moderating the temperature of the vipac fuel.

                                                                                                                                            JAEA R&D Review 2006

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