북한핵 방사성 핵종-포집-무슨 일이 벌어지나? > 자유

	자료사진

South Korean scientists failed to detect critical radioactive gas from air samples collected over the East Sea that could have proven whether North Korea used an enriched uranium device for its third nuclear test.

Using helicopters, the Navy collected air samples for 12 hours after the underground nuclear weapons test Tuesday, with winds blowing from the north, to try to catch any radioactive leakage from the nuclear test site in Punggye-ri, the northeastern tip of North Korea.

They brought the samples to the Korea Institute of Nuclear Safety, a state-run institute, for analysis.

The smoking gun they were looking for was a radioactive material called xenon. The types and amounts of xenon isotopes can demonstrate whether the North tested a plutonium- fueled device, as for its first two tests, or a uranium-fueled device.

When the North conducted its second nuclear test in 2009, the South’s scientists failed to detect any leaked gases.

Footage recently broadcast on the North’s official Korean Central Television showed that the tunnel at the Punggye-ri test site was designed like the one used in the 2009 test. In an effort to block leakage of radioactive materials from the underground test, the winding tunnel leading underground had 10 doors.

After the test Tuesday, Pyongyang announced it had succeeded in producing “miniaturized, lighter” nuclear bombs. Concern is rising that if true, the North is closer to being able to place a nuclear bomb small and light enough on its long-range ballistic rocket Unha-3, which reportedly can reach U.S. territory. Scientists say the smaller and lighter weapon would be fueled by uranium.

But the South Korean military and the National Intelligence Service publicly said the North has not developed those capabilities based on the size of the artificial earthquake set off by the nuclear test, which they said was a magnitude of 4.9.

The government says the explosive force of the device tested Tuesday was about six or seven kilotons of TNT bombs. The Defense Ministry said a normal nuclear bomb has a strength of at least 10 kilotons, like the one dropped on Hiroshima during World War II, which was 10 to 15 kilotons.

However, the Federal Institute for Geosciences and Natural Resources (BGR), a state-run geology research institute of Germany, estimated the explosive power of Tuesday’s test at 40 kilotons, nearly three times the strength of the Hiroshima bomb.

The German institute added that the Korean government tries to minimize its estimates of North Korea’s nuclear capabilities for political reasons.

A researcher at a state-run institute told the JoongAng Ilbo on the condition of anonymity that North Korea could have already deployed nuclear weapons on its bases.

“North Korea has recently unveiled a mobile launch pad for intermediate-range ballistic missiles,” the researcher said. “We view this launch pad as being capable of loading a nuclear weapon as well. North Korea has always unveiled its weapons after it deployed them on actual bases.”

A North Korean defector who claimed he was involved with development of military weapons for the regime said, “Although I haven’t seen any missiles loaded with a nuclear bomb, I’ve heard that the military has deployed a nuclear missile.”

The ruling Workers’ Party mouthpiece Rodong Sinmun also threatened in an editorial yesterday that North Korea might develop intercontinental ballistic missiles (ICBMs).

It said that the forces of imperialism possess nuclear weapons and ICBMs, and so could North Korea.

The editorial said that nuclear armaments were “the heaviest punishment against imperialism.”

The National Assembly of South Korea adopted a bipartisan resolution that denounced North Korea’s third nuclear test during a plenary session yesterday.

The resolution called the test “a grave provocative act” and said, “The North should take all responsibility for anything that happens next.”

It also demanded Pyongyang abandon its nuclear program and return to the Nuclear Non-Proliferation Treaty that the regime abandoned in 1993.

However, all six lawmakers of the opposition Unified Progressive Party, which has been criticized for a pro-North stance, refused to agree to the resolution and called for “a resolution through dialogue.”


By Kim Hee-jin, Jeong Yong-soo [heejin@joongang.co.kr]

한글 관련 기사

北핵실험 핵종 '제논' 포집 실패 이유 알고보니

북한의 핵실험 이후 포집된 시료에서 방사성 핵종이 검출되지 않은 것으로 14일 확인됐다.

전문가들은 정부가 포집 자체에 실패했으며 처음부터 방사성 핵종이 검출될 가능성은 제로에 가깝다고 분석했다.

핵폭발시 암반 균열 등을 통해 외부로 유출되는 제논과 크립톤은 공기보다 가벼워 남한쪽으로 하강할 확률이 희박하고 시간도 이틀이나 지났기 때문이다.

방사성 핵종 가운데 제논과 크립톤 등 방사능 물질이 포착되면 핵실험 증거로 간주한다. 특히 사용후 핵연료 재처리 때에도 발생하는 크립톤보다 제논이 더 결정적 증거로 활용된다.

서균렬 서울대 원자핵공학과 교수는 "공기보다 가벼운 제논과 크립톤이 휴전선을 넘어 남쪽으로 하강할 확률은 제로에 가깝다"며 "게다가 정부가 공중이 아닌 땅에서 포집을 하고 있는 상황에서 제논이나 크립톤이 검출될 리 만무하다"고 말했다.

또한 제논의 양이 절반으로 줄어드는 반감기가 9시간으로 짧아 핵실험이 이뤄진지 이틀이 지난 현재 검출될 가능성은 더욱 희박하다.

동해 공해상에는 미군 대기분석 특수정찰기인 WC-135W가 투입됐지만 이 또한 방사능 핵종을 탐지하지 못했다.

제논이나 크립톤이 검출되지는 않았지만 북한이 핵실험을 한 것은 확실하다고 전문가들은 말한다.

서 교수는 "TNT 7000톤 정도의 폭발력은 핵폭탄 밖에 없다"며 "북한이 핵실험을 한 것은 확실하다"고 말했다.

설령 북한의 핵실험으로 제논이 우리나라까지 넘어오더라도 인체에는 무해하다.

원자력 업계 관계자는 "제논은 불활성기체이기 때문에 다른 물체와 반응을 잘 하지 않고 몸에 들어오더라도 곧바로 배출된다"며 "감기 바이러스보다 덜 위험하다고 보면 된다"고 설명했다.

원자력안전위원회는 이번주 주말까지 포집과 분석 작업을 모두 마무리할 예정이다.

환경방사능감시 범위를 확대해 해수, 어류, 빗물 등에 대해 이뤄지고 있는 시료분석도 이번주까지 마무리한다. 공기 중에서 제논이 검출되지 않은 이상 해수, 빗물 등에서도 제논이 검출되지 않을 것으로 보인다.