Out of irritation with that list, I've added the SSRs for each of the plants, because it's otherwise a little tricky to make sense. Out of 11 total plant sites, 7 were in the Russian SSR, 3 were in the Ukrainian SSR, and 1 was in the Armenian SSR. In terms of built or planned reactors, assuming that list is exhaustive, out of the 40 total, 26 were in the Russian SSR, 12 were in the Ukrainian SSR, and 2 were in the Armenian SSR.

That list, though, is not exhaustive — it's missing a lot of other reactors in other Soviet republics (and the Warsaw Pact states). (I've added one, but there are more. There are also many errors in dates. Expect it to be updated pretty soon...) In general though, I think it is pretty clear even from the above that you're looking at a pattern that was more or less the bulk of nuclear power being in the Russian SSR, about half of that number in the Ukrainian SSR, and then a power plant here and there for other SSRs. Here's a map, from Sonja Schmid's Producing Power: The Pre-Chernobyl History of the Soviet Nuclear Industry (MIT Press, 2015).

I suspect that you would find that matches up pretty well with the industrial output by SSR by the period in which these were planned and commissioned (1970s-1980s). The planning for nuclear reactor sites in the USSR was done (like most things) in a highly centralized way around projected economic/industrial demands (five year plans, etc.). Schmid doesn't go into much detail on this aspect; she says just that:

Nuclear power plants were sited according to a set of criteria that included proximity to a metropolitan area with high energy demand, great distance from fossil fuel resources, a significant reservoir of water for cooling, existing infrastructure (roads, transmission lines, etc.), and the availability of large contingents of construction workers.

She emphasizes, though, that internal bureaucratic forces were also at work: the two ministries involved in nuclear power (Minenergo, which ran all Soviet energy plants no matter what type, and Sredmash, which was in charge of nuclear reactor design and nuclear weapons development) both pushed nuclear power as an important way to modernize the Soviet economy in the 1960s and 1970s, and the head of Minenergo, Petr Neporozhnii, was apparently quite good at advocating for the construction of nuclear plants above other types. He persistently pointed towards increased energy demands, and to the fact that Soviet nuclear power plants were comparable in cost to fossil fuel per kilowatt hour, and that they allowed the assignment of workers away from fossil fuel-related activities (like coal mining) to other sectors. Key to this plan was the cheapness of some of the reactor designs, like the ill-fated RBMK, which was designed for exactly this sort of situation (making massive, centralized, relatively cheaply produced nuclear power plants that were comparatively easy to construct and could use local labor to do so).

It's hard for me to tell from Schmid whether she thinks Neporozhnii was essentially a bullshitter in this respect; reading between the lines, it sounds like he was essentially consolidating his own importance and power in this way, and that they may have been constructing for construction's sake. But either way, I don't think there's anything particularly special about Ukraine here — it was the #2 Soviet republic for industry and manufacturing, so it's not surprising that it got a lot of plants as part of their general electricity scheme.