1.   The pebble-bed reactor would be cooled with helium gas rather than water, the coolant used in most existing nuclear reactors.

2.   The nuclear plant dips its feet in these same waters, which it uses to cool the reactors.

3.   The pebble-bed reactor would be cooled by helium, in contrast to the water-cooled reactors now used in the United States.

4.   To cool the reactor without slowing the neutrons, the Fast Flux Test Facility used sodium, a metal, in a molten form.

5.   But he denied news reports that radioactive materials seeped into water used to cool the reactor and said the problem could not have led to a major accident.

6.   But the danger of working with plutonium and the difficulty of cooling the reactor have convinced most countries to scrap their breeder reactor plans.

7.   Conventional reactors can be cooled with water, but plutonium requires a more corrosive material such as sodium to draw off heat.

8.   Conventional reactors can be cooled with water, but plutonium requires a more effective material to draw off heat.

9.   Conventional reactors can be cooled with water, but plutonium requires a more corrosive material to draw off heat.

10.   He described the plant as stable but said the alert would last several hours overnight as the shutoff reactor is cooled.