However, nuclear reactors generate 100 grams of the substance worldwide each year.

然而，每年全球各地的核反应堆都会产生100克左右这样的物质。

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Cesium-137, with a half-life of 30 years, is another dangerous substance emitted in a full-scale nuclear meltdown.

核反应堆完全熔解后，会释放出另一种危险物质铯- 137。铯- 137的半衰期为30年。

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Who is issuing this advisory following reports of people in Japan and elsewhere who are using the substance in response to radiation leaks from nuclear plants in northeastern Japan.

世卫组织发出这一建议是因为有报导说，日本和世界其它地区的民众为了应付日本东北部地区核电站的核辐射泄漏而正在使用这种物质。

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Tritium is a radioactive substance produced by the reactors from nuclear-powered submarines based at the Devonport yard.

BBC: Tritium is released from submarine reactors

Ore from the mine is processed at Jaduguda into a substance called U308 - commonly known as yellow cake - and then sent to the Nuclear Fuel Complex in the southern city of Hyderabad, where uranium fuel rods are produced.

CNN: NUCLEAR FALLOUT