If I read it right, he has stopped working on a form of artificial intelligence because it could potentially (or inevitably) be used to create androids indistinguishable from humans that are carrying nuclear or biological payloads inside of them, presumably to be detonated in a densely populated area. Taking as a given, like he does, that the advancement and spread of technology are inevitable, wouldn't it still be m…
Humans don't carry nukes because fissile material is _heavy_. Add onto that the shielding to make sure the person can even carry it without becoming gravely ill very shortly into their delivery and the fact a suitcase nuke or dirty bomb has never been personally delivered is not very surprising. The ridiculous part is that making an android carry this payload doesn't change the nature of the payload. Heavy, fissile m…
What probably is quite heavy is all of the associated components that you need to make a bomb - the chemical explosives, tamper etc.
The W54, one smallest nuclear warhead anyone is admitting to making, was about 23kg - although this did have a very small yield.