Th232 and U238

U233 and Pu239

U233 and Pu238

None of these

to maintain constant pressure in primary circuit under varying load

to Supply high pressure steam

to increase pressure of water in primary circuit

to provide subcooled water at high pressure

light or heavy water

molten lead

carbon dioxide

freon

natural uranium

molten lead

any form of uranium

thorium

control temperature

control radioactive pollution

control absorption of neutron

control fuel consumption