A parameter study of the transient thermal response of the recent International Thermonuclear Experimental Reactor design was performed for unmitigated loss of coolant accidents (LOCAs). Inboard component temperatures and hydrogen production levels remained low for an unmitigated blanket cooling system LOCA. Adding an unmitigated LOCA of the vacuum vessel cooling system to the blanket cooling system LOCA scenario results in much higher first wall temperatures and the production of flammable and, eventually, detonatable amounts of hydrogen in the plasma chamber.