Wonder why the failure rate on clandestine U-235 weapons programs?

The USA, Libya, Brazil, Argentina, South Africa and Iran went the U-235 path. The USA was the only success story, and they had a backup Pu-239 program anyway that produced Fat Man not long after Trinity.

North Korea, Israel, France, the USSR, India and Pakistan went the Pu-239 route, and succeeded.

(Britain and China's programs omitted as not clandestine, more as junior partners of the USA and USSR programs).

(Iraq's program I haven't listed as so much of what we "know" about it was deliberate lies)

Do you think isotopic enrichment is just a harder engineering challenge than breeding and separation?

Or is there some common characteristic of the regimes or their capabilities that drives both technology choice and subsequent failure?

#uranium #nuclear #weapons #war #geopolitics