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4. Lead-bismuth technology<br />

Lead-bismuth is the first candidate material for liquid metal target and coolant of fuelled blanket<br />

system in ADS researched at JAERI. Advantages of the lead-bismuth utilisation are non-active<br />

material, very low capture cross-section, low melting point of 125°C and high boiling point of<br />

1 670°C, and beside coolant void reactivity become negative. But potential problems are due to the<br />

high corrosivity to most of the structural materials. At this moment the corrosive data are scarcity.<br />

Solution is how to control material performance in corrosive environment. Here, corrosivity, reaction<br />

with water, thermal-hydraulics etc. are studied by investigating some facilities utilised and researched<br />

really for lead or lead-bismuth. And, furthermore, polonium evaporation rate and bismuth resource are<br />

investigated. Main results obtained are as follow [4]:<br />

• In a refinery of Japan, there are enough employment experience for liquid Pb-Bi in period of<br />

about 17 years and not corrosion for the thermal conductive materials (1Cr-0.5Mo steel) used<br />

under the condition of natural convection with temperature around 400°C.<br />

• In Russia, extensive experience in the use as Russian submarines and in R&D during about<br />

50 years are available. And as a result, it will be able to lead approximately zero corrosion for<br />

Cr-Si materials by adjusting oxygen film with oxygen concentration control between 10 -7 to<br />

10 -5 % mass. However, the corrosion data are not enough systematically collected involving<br />

them in radiation dose field.<br />

• In liquid-dropping experiment, it is shown that interaction between water and high<br />

temperature liquid Pb-Bi is reduced steeply with rising of atmosphere pressure. But, in order<br />

to design the second circuit removal model of ADS, the interaction should be evaluated by<br />

water continuous injection experiment.<br />

• Polonium forms PbPo in Pb-Bi, and the evaporation rate become less three factor than that of<br />

Po, and furthermore, the rate decreases in the atmosphere. The effects of Po on employee and<br />

environment will not be dominant in comparison with those of fission products.<br />

• In Bi-resource, a confirmed amount will be 260 000 tonnes and an estimated amount will<br />

become ten times of the confirmed ones by including resources in Russia. This shows there<br />

are enough amounts for ADS developments.<br />

5. Experimental facilities for the ADS technology demonstration<br />

There are several technical challenges unique to the accelerator-driven transmutation system. The<br />

major areas of technology to be tested and demonstrated are sub-critical reactor physics, system<br />

operation and control, transmutation, thermal-hydraulics, and material irradiation [6,7,8].<br />

Reactor Physics Experimental Facility “PEF”: Table 3 shows the purposes and items of<br />

experiments at the PEF. Data based on the FCA experiments using a 252 Cf neutron source and a<br />

14 MeV D-T pulsed neutron source will be used in designing the PEF facility and planning the<br />

experimental program.<br />

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