Energy consumption of reverse osmosis is about 4kWh/t. The byproduct is a ton of brine. Sea water contains about 3ppb Uranium, so our brine contains 6mg of U per ton of fresh water produced.

A 1GW nuclear power station consumes about 1t of U per year and produces about 8000GWh of electricity in that time. So we need about 1mg/8kWh. We got 12 times that much.

So, it sort of works out. Of course, this assumes a breeder reactor and I pretended that brine is purified uranium. If breeders are commercialized, it might be worth looking into this. Right now, it isn't.