[my_first_acct]

A handy website [1] notes at least a couple of B-52 nuclear incidents. In 1961, a B-52 carrying nuclear weapons broke up in mid-air over North Carolina; the bombs did not detonate [2]. In 1966, a B-52 crashed due to a mid-air collision with a refueling tanker over Spain. In this case, the non-nuclear explosives in two of the nuclear weapons detonated, scattering radioactive material [3].

So I would not say "zero nuke detonations". And your .00001% failure rate (I didn't check your math) is not meaningful unless compared to the failure rate of other aircraft. The B-52 is impressive, but not flawless.

[1] http://www.atomicarchive.com/Almanac/Brokenarrows_static.sht...

[2] https://en.wikipedia.org/wiki/1961_Goldsboro_B-52_crash

[3] https://en.wikipedia.org/wiki/1966_Palomares_B-52_crash

[greedo]

Most people would not refer to the incident at Palomares as a "nuke detonation," since there was no nuclear detonation. No fissile reaction etc, just conventional explosives that are part of the weapons trigger. To call it a "nuke detonation" is disingenuous.