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lead cooling (see Fig. 5). Alternatively, gas cooling is investigated as well to enable choices when it
comes to a decision how to proceed in the far term future.
Table 2: Design choices taken for EFIT and XT-ADS
XT-ADS EFIT
Coolant Pb-Bi Pure
Gas)
Lead (backup:
Primary System Integrated Integrated
Power 70 MWth ~ 400 MWth
Core Inlet/Outlet Temp 300°/ 400 o C 400°/ 480 0 C
Target Unit interface Windowless Windowless
Target Unit geometry Off-center Centered
Fuel MOX (except for a few MA (Pu, Am)O2 + MgO (or
Fuel Assemblies)
Mo)
Av. Fuel Power density 700 W/cm³ 150 to 200 W/cm³
Fuel pin spacers Grids Grids
Fuel Assembly type Wrapper Wrapper
FA cross section Hexagonal Hexagonal
Fuel loading Bottom Top
Nominal coolant Forced with mechanical pumps Forced with mechanical
circulation
pumps
Primary coolant circulation
for DHR
Natural circulation Natural circulation
Secondary coolant Low pressure boiling water Superheated water cycle
Accelerator LINAC (power: 2 ~ 5 MW) LINAC (power: ~ 12
MW)
Beam Ingress (1) Top Top
(1) Proton beam specifications of these designs are considered for the so called HPPA (High-Power
Proton Accelerators) with a proton energy ranging from 600 MeV for the XT-ADS with a maximum
bean intensity of up to 4 mA up to the range of 800 to 1000 MeV for the EFIT design with a
maximum beam intensity of up to 20 mA. The recommended proton beam should possess a CWbased
time structure with additional short and well defined (sharp edge) beam interruptions of
about 100 to 200 �s with a repetition frequency in the order of 1 Hz. These beam holes, shutting
down the neutron power source from time to time, should enable continuous and accurate on-line
measurements and monitoring of the reactor sub-criticality. The beam should have a power stability
of 2% and a 10 % beam size stability on the target etc. (see [5]).
The windowless target is the reference solution for the EFIT and the XT-ADS design. In this target
design the proton beam impinges directly on the redirected LBE flow in the lower part of the beam
tube at core centre (spallation zone). Cooling of the target is achieved by forced convection inside
the target unit.
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