But it depends on the depth of the radioactive material.

VOA: special.2011.03.29

We have 266 ping-pong balls, and we need someone, hopefully you, to be some radioactive material that are going to be emitting these ping-pong balls. And when the time comes, in just a minute, I'll ask the TAs to come down and hand these out very quickly to you, so we can do this experiment.

你们有些人那天，看到我在办公室数乒乓球，我们需要几个人,希望是你,来作为放射材料，放射这些乒乓球,等会我会让助教,把这些球发给你们。

麻省理工公开课 - 化学原理课程节选

So,yes,there is a threat particularly of the use of radioactive material, although we have no specific evidence indicating any capability at this time."

VOA: standard.2009.05.01

You may also consider the factual history of the apartment building in Japan that was mistakenly constructed with some highly radioactive material, the inclusion of the radioactive construction material was not discovered until many years later, the residents were studied extensively for evidence of increased cancer.

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In 2009, Esa funded a pilot project to examine the cost and practicality of establishing a European source of material for Radioactive Power Sources (RPS).

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In fact, standards for NORM (naturally occurring radioactive material) have been observed for years.

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