A single ARC reactor will use 40% of the world's annual production of beryllium.
The power density of an ARC reactor will be around 0.5 MW/m^3. In comparison, the power density of a PWR reactor vessel is 20 MW/m^3.
Replacing the entire inner vessel once a year would be an operational nightmare. For one thing, it ensures the building the reactor is in will have to be very large, with very large secondary bays where the intensely radioactive material of a spent reactor vessel can be moved and disassembled (generating radioactive fragments and dust).
Boron, however, is more easily concentrated (in evaporites). Beryllium is found in pegmatites, which are less common. The estimated resource (not reserve) of Be is 100,000 tons (USGS). This would be enough for ARC reactors supplying just 1% of current world primary energy demand. The estimated world resource of boron is in excess of 1 billion tons.
The power density of an ARC reactor will be around 0.5 MW/m^3. In comparison, the power density of a PWR reactor vessel is 20 MW/m^3.
Replacing the entire inner vessel once a year would be an operational nightmare. For one thing, it ensures the building the reactor is in will have to be very large, with very large secondary bays where the intensely radioactive material of a spent reactor vessel can be moved and disassembled (generating radioactive fragments and dust).