1 kg is the amount of fissile material, but it needs quite a lot of high explosive around it. The file you linked says 16kg, and 28 cm by 30 cm. I suspect the

1 kg is the amount of fissile material, but it needs quite a lot of high explosive around it. The file you linked says 16kg, and 28 cm by 30 cm. I suspect the soda-can sized charges you recall were conventional explosives for the small, non-nuke prototype they tried out.