英文: A fresh six-party agreement reached last February has resulted in the admission of international nuclear inspectors and the shutdown of North Korea's Yongbyon complex, which had produced bomb-grade plutonium
-- in return for 50,000 tons of heavy fuel oil.
英文: All the more important, then, to keep a close eye on plants that produce quantities of such dangerous materials—especially where uranium is enriched and plutonium
is extracted from spent fuel.
英文: Although almost all this material, which has a 24,000-year half-life, has since disappeared (primarily through natural radioactive decay), some of the plutonium
itself underwent fission, as attested by the presence of its characteristic fission products.
中文: 这些物质半衰期为2万4000年，几乎已经全部消失（主要是经由自然的放射衰变过程），而且部份的钸本身又经过核分裂，这可由其核分裂产物为证。 更详细...
英文: By getting away with freezing just plutonium
production last time, North Korea managed to prevent inspectors from the International Atomic Energy Agency, the UN's nuclear guardian, from snooping anywhere else.
英文: Cowan described, for example, how some of the neutrons released during the fission of uranium 235 were captured by the more abundant uranium 238, which became uranium 239 and, after emitting two electrons, turned into plutonium
中文: 例如，柯文描述了某些铀235分裂所释放的中子，如何被含量更多的铀238捕捉而产生铀239，在放射出两个电子后又变成钸239。 更详细...