Most of the respondents to your comment focused on the bananas themselves as being the issue, but they are actually missing the point somewhat. Bananas do have more potassium and are more radioactive than other fruit, but actually, its the "putting them inside you" which is the much larger issue. The inverse square law applies to all forms of radiation and you've effectively reduced that to 0 by ingesting the thing which is radioactive. So instead of absorbing a small fraction of the total radiation emitted by the thing over time, you are exposed to ALL of the radiation emitted by the thing over time. Not to mention any radiation given off the plates is not even going to be able to penetrate your skin or clothes; whereas the banana is already inside you.