Q+A: What's next for North Korea's nuclear arms program?

SEOUL (Reuters) - North Korea's test of a nuclear device on Monday could be the first of a series of steps by the secretive state to enhance its nuclear weapons programs.

Here are some questions and answers about what come next:

WHAT WILL HAPPEN AT NORTH KOREA'S YONGBYON NUCLEAR PLANT?

North Korea has said it is restarting the facility that separates spent fuel at its Soviet-era Yongbyon plant, which was being taken apart under a six-country disarmament-for-aid deal.

Reprocessing work can resume quickly and by the end of the year it will be able to extract at least another 8 kg of plutonium, according to Siegfried Hecker, former head of the U.S. Los Alamos nuclear weapons lab who has visited Yongbyon several times. It usually take about 6-8 kg to build a bomb.

Prior to the test, North Korea had enough plutonium for six to eight nuclear weapons. In order to produce more fissile material, it will probably soon say it plans to restore its nuclear fuel fabrication plant and reactor. Experts said it could take a year for Yongbyon to be fully operational and then the plant can produce about a bomb's worth of plutonium a year.

WHAT ABOUT MORE NUCLEAR TESTS?

Government officials said the North, which first tested a nuclear device in October 2006, may be looking at more tests soon to enhance its weapons capability. But such a move would be highly risky for Pyongyang because tests deplete its meager plutonium stockpile. Also, parts of the Yongbyon plant may be beyond repair, which means that plans to replenish its fissile material could take even longer than experts expect.

WHAT IS GOING ON IN SECRET?

North Korea is probably using data from nuclear tests to build a weapon it can eventually mount on a missile, which may take several years, or could prove too difficult for it to master, intelligence sources have said.

Experts say the North has also been working on weapons that use chemical and biological agents as well as dirty bombs where radiation is spread through conventional explosions.

WHAT ABOUT THE CLANDESTINE URANIUM ENRICHMENT PROGRAMME?

That program, long suspected by the United States as an alternative way for the North to develop a nuclear bomb, may become a bit more open. The North may say it is starting a uranium enrichment program to provide fuel for a light-water reactor it plans to build. This supposed civilian program could serve as a cover to produce highly enriched uranium for weapons because the technology for a light-water reactor is beyond the North's reach and it is likely that the reactor is too expensive for the destitute state, experts have said.

WHAT ABOUT PROLIFERATION?

The proliferation threat is real, experts said, with the United States saying the North has been aiding the likes of Syria with a nuclear weapons program.

North Korea's nuclear technology, albeit rudimentary, has become more desirable due to the test. North Korea has shown a mastery of the nuclear fuel cycle, the ability to weaponize plutonium and now set off a device estimates said could be as powerful as the U.S. atomic bomb dropped on Nagasaki in 1945.

(Editing by John Chalmers)