As far as I understood the whole thing, getting the bomb first led to uranium enrichment. Nuclear enrichment led to PWR and BWR for military use, notably for Rickover's submarines. Then when Ike started Atom for peace in 1955, the industry just adopted the nuclear submarines PWR - and even today PWR are the standard nuclear energy powerplant - and then we had TMI and Fukushima coolant accidents (Chernobyl was different).
Now if peaceful use of the atom come first (let's take a cool ATL: Pdf27
A blunted sickle) then the whole enrichment and PWR never happens, and perhaps better reactor types become the norm. I have a crush for the Molten Salt Reactor, which is also pretty good for space applications.
I'd like to read a TL where peaceful use of the atom come first - no Manhattan project. Even if that mean that nuclear developments are one or two decades backward when compared to OTL.
It would be to nuclear power what
alternate Apollos (think Nixonshead
Kolyma's shadow)are for space TLs: reach for the Moon happens later than 1969, but in a much more sustainable way.
Same way for nuclear matters: no Manhattan project means that civilian nuclear power come later than 1956 (perhaps a decade or two),
but with better reactors than goddam PWR.
To think the United States spent 8 trilion dollars (yes, 8000 billions) on nuclear weaponry between 1942 and 1992... imagine if all that money had flowed into making
THIS happening instead (I really have to write that TL someday) No nuclear dick -measuring contest with USSR, perhaps that country is utterly weakened by the Nazis, who ultimately lose to America, now the one and only superpower without any nuclear weapons - whatif we invest all thoat money in colonization of space)