It doesn't matter if you have a new design if you don't deploy it. The Fukushima plant was older than the Chernobyl plant. One could have simply decided to replace it with a newer design. In hindsight if Japan's government didn't have to pay for the Fukushima cleanup they could have done more sensible things, like update the entire nuclear fleet. It certainly would have been cheaper to tear all nuclear plants in Japan down and build new ones when you look at the cost overruns at Fukushima.