You only need 12 per row if you share the heat pipe line. That lets you feed them off a single offshore pump and doesn't require a power pump on the output, and also matches neatly with 20 turbines per row. You can even go down to 11 per row if you don't mind losing a couple of percent of maximum sustained generation in very large setups. This setup tessellates at 14 reactors (and 20 rows), so your heat output for the 2x row is 4480n - 160 MW, and your heat consumption is 4400n MW.
4480n - 4400n = 160 -> 80n = 160 -> n = 2. You only start losing capacity at all after 56 reactors, and beyond that it will tend towards a loss of ~1.8% to the peak sustained generation.