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Good work granny - the article does look like it has good information in it. I can't verify his count of the number of devices and the total amounts of radioactive sources missing, but the rest of it all sounds about like what I'd expect given the possible situations he gives with the amount of radiation released in each case.

The article is written for the scientifically inclined layperson, which means that it's neither as technical as a true scientific journal article would be nor as non-technical as a typical newspaper article would be - perhaps at about the level of a Scientific American article. If you haven't had at least a couple of university level science courses (or at least not recently) I can see how it might be rough going.

One term that he never defines is a "curie." This is a measure of radioactivity, named after Marie Curie who was a physicist who studied radioactivity. A highly radioactive source will emit more radiation than one that's not highly radioactive. This in turn relates to how fast the radioactive source decays - if it decays quickly it emits more radiation than if it doesn't decay quickly. The scientific term for this is half-life - a longer half life means that the material will be around longer but it doesn't emit as much radioactivity.

Think of the "half-life" as being much like temperature - it measures how "hot" something is. In the case of a half-life, lower numbers are "hotter." In turn a "curie" measures how much radioactive "energy" is there, and will be the product of the "temperature" times the amount of material present - much like a "calorie" when you're talking about chemical energy. A Curie though is a LOT of radiation, it's a much "bigger" unit than a calorie, at least in terms of what you might encounter under normal conditions.

Hope that helps.