1.   It had once captured condensation dripping from ventilation and cooling systems around a graphite research reactor and the main reactor at the laboratory, Ms. Rowe said.

2.   Last year North Korea said it wanted to obtain a modern light-water nuclear reactor from abroad to replace its graphite reactors now in operation or under construction.

3.   Nor would the North need to complete its new graphite reactor, a threat because it would generate plutonium once it is up and running.

4.   North Korea, meanwhile, is demanding a new light-water nuclear reactor to replace its current graphite reactors.

5.   Such a reactor is somewhat less vulnerable to misuse than the graphite reactor North Korea now has.

6.   The new reactors would make it more difficult for the North to extract plutonium for bombs than it is with its current graphite reactors.

7.   The water in the tank was first noticed in December, she said, during inspections near the graphite reactor.

8.   Washington favors such a change because light-water technology yields less plutonium than graphite reactors.

9.   At issue are negotiations over replacement light-water reactors to substitute for the stilled five-megawatt graphite reactor suspected of producing fuel for nuclear weapons.

10.   Bilibino is a graphite reactor that has been specially designed for use in areas of high seismic activity such as often occurs in the Russian Far East.