The Pacific Ocean was contaminated down to Hawaii after Fukushima. On the other hand, Chernobyl caused massive atmospheric conmamination in Eurasia. Fortunately tech was in place and dangerous clouds were mostly brought down in Bryansk region. Good for Poland, winds blew to the East. 
You cannot directly compare the magnitude and severety of consequences, but you can compare organisation and effectiveness of countermeasures. The Soviet Union in this was far more advanced country than modern Japan.