YSK a vest cannot hold enough fissile material to yield significant damage. It is impossible.
Why ysk...certain parties are lying about this... it is PHYSICALLY IMPOSSIBLE.
A device of this nature would have such a small yield it would have a blast radius of roughly a city block. Similar to conventionals. And it's size would make the material detectable because shielding it effectively would be impossible.
A fusion device cannot be made that small.. Making a fission device that small would be dumb, detectable, expensive, and weak.