So, the question becomes whether {tlhuD} is a Klingon physicist’s jargon, or a common Klingon’s word that might, as in English, have a wider scope of meaning.

Or whether the sentence is in error. Or whether terminology has been changing since that sentence was written. Or whether the identification of tlhuD as having to do with radiation was scientifically inaccurate or imprecise. There are lots of reasons why this apparent contradiction might exist. Any speculation is done in a vacuum.

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SuStel
http://trimboli.name