Sounds like Californium 252.
Neutron emitter used sometimes in oil industry.
Not a serious threat as a weapon unless you want to take out less than 10 people.
REALLY expensive weapon, probably over $1M
“Not a serious threat as a weapon unless you want to take out less than 10 people.”
It’s not the damage, it’s the threat. People hear “radiation” and they panic. In this case 10 grams will set off radiation detectors, which is enough.