It wasn't a secret like the article admits later on.
The objective is to avoid attention, not to be secret per se, though the effect can be similar.
Now CANDU reactors run on natural uranium. So they're forming metal pellets out of uranium powder. The main risk is direct chemical toxicity from the uranium, not the radiation. But for many people "nuclear fuel" might as well mean hot nuclear waste.
The mystical level of dread it inspires in some is hard to overstate. Just to avoid drama from the neighbours it's understandable they try to keep quiet.
> And aside from a license renewal snafu in 1980, the device made no waves until its existence was shared with the local newspaper—it wasn’t a secret, just unpublicized.
If someone freaks out about it, it’s because they think you’re abusing normal, run of the mill product development secrecy, whether to develop a product that shouldn’t exist or to hide a practice that is never intended to be public and is just called secret to avoid scrutiny from an interested public (who, in this hypothetical scenario, feel that they have a right to be interested — think research into dangerous pathogens next to an unprotected public aquifer).
It sounds like there is no penalty to the nuclear labs except, if you blab to the wrong person, it’s going to stir up trouble.
I guess in this case the question comes down (for me) to whether employees at this lab were asked by their managers not to tell friends and acquaintances what they worked on. Even if not with an explicit threat of harm, asking someone not to tell something is pretty much exactly what asking them to keep it a secret means.