I've read that in the case of Paks a retrofit doesn't make sense because the entire thing is so old and needs to be rebuilt anyway.

However, hopefully, they change the plans for (stalled project) Paks 2, because that would've used the same cooling system as the first one.

I believe there was also a planned much cheaper retrofit to use pumps to increase force to necessary levels but it was scrapped.

Is it economically viable to run though? Natural draft towers or direct body of water cooling is used almost universally since it doesn't take any extra power. A large chunk of the powerplant's output would be running heat pump compressors to stop itself from exploding.