Based on the two-reactor design by @FilthyMonkey (https://factorioprints.com/view/-M4DR_tmCVxzIIxQqvLG) this is a four reactor plant that will produce 1.5GW of power without wasting fuel, by buffering steam in Huge Storage Tanks. I'm pasting the [updated] description of the two-reactor plan created by @FilthyMonkey:
I have updated one of my older reactor designs to Krastorio 2 standards. This [four] reactor plant will produce [1500]+MW of power and is completely lossless no matter what your power draw. It will daintily sip on fuel cells while storing the excess as steam, only reloading when the steam is low. [It does require logistics bots.]
The nuclear ratios in Krastorio 2 are vastly different from vanilla, so old designs won't work correctly. In particular, the base heat of the reactors is far higher, heat exchangers are far more powerful (and water hungry) and steam turbines are higher power.
Make sure that each of the [seven] water inputs has its own separate pipe and separate offshore pump. If you try to combine pumps/pipes you will end up with insufficient water.
To start the plant, first hook it to your existing power grid so that the inserters have power. Then manually load exactly one fuel cell into each reactor. The rest will happen on its own.
This plant should provide you with ample and efficient power to propel you into the late game, when higher tech options become available.
[Updated - the two heat exchangers on the end weren't connected, doh!]