Leningrad 1, in 1974, was the first RBMK reactor ever (though, like most reactors, the general principles date back further). Chernobyl 1 was 1977, so the desig

Leningrad 1, in 1974, was the first RBMK reactor ever (though, like most reactors, the general principles date back further). Chernobyl 1 was 1977, so the design was only 3 years from first online. Chernobyl 4, the one that exploded, was actually built in 1983, 12 years after Fukushima 1 (one of the 3 that melted down). Fukushima 1 was a GE BWR-3, 2 and 3 were BWR-4. These were introduced in 1965 and 1966 respectively. Both RBMK and BWR have they origins in the 50s. So, in terms of newness of the specific model, the RBMK was a little under 10 years newer than the BWR-3/4. That said, the RBMK failed due to an internal reactor design issue, the Fukushima BWRs due to reactor support system failure.