Its purpose is not to shield radioactive emissions but to prevent the release of radioactive dust and other materials, and to keep out rainwater, which could carry contaminants into the water table.

它的作用不是用来遮挡放射性排放而是阻止放射性烟尘和其它物质的释放，以及遮挡雨水以防止雨水携带污染物流入地下水。

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Days after signing a deal to cut U.S.and Russian nuclear arsenals, President Obama hopes to strengthen global resolve to safeguard nuclear stockpiles and keep radioactive materials out of the hands of terrorist groups and rogue states.

VOA: standard.2010.04.11

Tuesday's explosion at the No. 2 reactor in the Fukushima complex, 150 miles north of Tokyo, for the first time raised the possibility that the key containment structure of the unit, which protects the reactor vessel and keeps dangerous radioactive materials from leaking out, had been damaged.

WSJ: Japan's Nuclear Crisis Escalates

Rather, as a consequence of injecting water and sand into the shale formation to crack the rocks so gas and oil will flow, massive amounts of waste water comes back to the surface with significant amounts of contaminants as a result of leaching out salt, heavy metals and trace amounts of radioactive materials from the rock formation itself.

FORBES: U.S. Energy Independence - So Close, Yet So Far

Just to be clear, what we sent out were these pods, and these pods measure deposition of radioactive materials on the ground.

WHITEHOUSE: Press Briefing