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Table 3. Experimental items at PEF<br />

Purpose<br />

Neutronics of fast sub-critical systems<br />

driven by a spallation source<br />

Demonstration of controllability of a<br />

hybrid system<br />

Validation of transmutation rate of MA<br />

and long-lived FP (LLFP)<br />

Experimental items<br />

• Power distribution in deep sub-critical systems<br />

• Effective source strength and multiplication factor<br />

• Effect of high energy particles<br />

• Feedback control by beam adjustment<br />

• System behaviour for beam trip and restart<br />

• <strong>Energy</strong> gain<br />

• MA fission rate<br />

• LLFP reaction rate in moderated region<br />

• Reactivity worth of MA and LLFP samples<br />

A typical sub-critical core configuration at the PEF is shown in Figure 4. The structure of the PEF<br />

is based on that of the FCA facility with flexible structure to carry out various experiments. The<br />

effective multiplication factor is in the range of 0.90-0.98. The maximum proton beam power and the<br />

core thermal power are limited to 10 W and 500 W, respectively, due to the heat removal limitations<br />

by forced circulation of air. In Table 4, the proton beam and core power specifications are shown for<br />

Step 1 and Step 2. Experiments at the critical state will be also carried out as the step for the precise<br />

measurement of reactivity and neutron multiplication factor.<br />

In Step 1, reactor physics experiments of the sub-critical core and demonstration of the principle<br />

of ADS are to be performed, and it may be the first demonstration of the ADS concept in the world.<br />

Table 4. Beam and power specification for sub-critical experiments at PEF<br />

Step 1<br />

Step 2<br />

Proton beam<br />

0.6 GeV, ~16nA,<br />

10 W, 25Hz pulse<br />

1.0 GeV, ~10nA,<br />

10 W, 50 Hz pulse<br />

Core thermal power<br />

~500 Wt<br />

~500 Wt<br />

Engineering Experimental Facility “EEF”: The reference target design assumes to have a<br />

hemispherical beam window made of chromium-molybdenum steel cooled by flowing lead-bismuth.<br />

One of the high priority issues is degradation of structural material in a lead-bismuth coolant at high<br />

proton and neutron fluxes and high temperatures. Design of the beam window, in particular, represents<br />

the highest technical challenge since it will suffer radiation damage, thermal stress, differential<br />

pressure load and corrosion.<br />

540

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