Yes it does mean bitter. However I don't think the two are events can be compared because wormwood is supposed to make 1/3 of the water's bitter. To say that Chernobyl even made .013 % of the waters bittter or unusable would be an overestimation. There is a lot of water on the earth.
It was only 20 years ago that Reactor 4 at Chernobyl in the then USSR melted down, releasing radioactivity for thousands of miles. It has also been pointed out to me that the name "Chernobyl" means "bitter" in Ukrainian. If this is true, then what about the star in Revelation (8:13?) called called "wormwood" which fell to earth and turned 1/3 of the waters to wormwood (bitterness)?