Your point about "nuclear reactor" is well taken, but, ultimately, not really relevant. No amount of explanation makes a joke funny to someone who doesn't "get it." Further, many coordinate bilinguals never get this feeling, simply because they're coordinates. Compound bilinguals do get it, and find it impossible to explain.
And here I am, once again, trying to explain a joke to someone who doesn't get it.
(Please note - that last was an analogy. This isn't a joke, it is real that there are some terms that just don't translate, even when you expand your translation into an explanation. Some things need to be experienced, and cannot be appreciated from logic and reason alone.)