 Under his leadership , General Atomics developed TRIGA , a small reactor for universities and laboratories . TRIGA used uranium <unk> hydride ( <unk> ) fuel , which has a large , prompt negative fuel temperature coefficient of reactivity . As the temperature of the core increases , the reactivity rapidly decreases . It is thus highly unlikely , though not completely impossible , for a nuclear <unk> to occur . Due to its safety and reliability , which allows it to be installed in densely populated areas , and its ability to still generate high energy for brief periods , which is particularly useful for research , it became the world 's most popular research reactor , and General Atomics sold 66 <unk> in 24 countries . The high @-@ temperature gas @-@ cooled reactor ( <unk> ) was less successful , and only two <unk> power reactors were built , both in the United States . A 40 MW demonstration unit at the Peach <unk> Nuclear <unk> Station in Pennsylvania operated successfully , but a larger 300 MW unit at the Fort St. <unk> <unk> Station in Colorado encountered technical problems . General Atomics also conducted research into thermonuclear energy , including means of <unk> <unk> plasma . Between 1962 and 1974 Creutz published six papers on the subject . 
