Alright, Yahoo is complete trash. So here's some info for starters:
This would not be an explosion. They used the word "explosion" a lot. This is physically impossible. It would be a criticality accident--Essentially, much of the remaining fissible material would rapidly react with itself and produce tons of heat and radiation. The "explosion" at Chernobyl was not a nuclear explosion, as none of the material used in traditional reactors is refined enough to cause a nuclear explosion. It was a steam explosion from the coolant/turbine water.
Next, there is almost no risk to anyone at all. If a criticality accident occurs, no one will be near it. The event will superheat the air around it and melt the surface beneath it some. It will release a large amount of radiation into the air around; some of it will be contained by the shelter, and some will be dispersed into the surrounding environment. Given the decades that have passed and the half-life of the remaining fissible material, it would be a fraction of the radiation released in total from the original event and a large majority won't even reach beyond the Chernobyl site itself, let alone outside of Exclusion Zone, thanks to the safety pre-cautions.
If a criticality accident occurred, I would be shocked if studies would even link potential deaths to it in the follow decades as long as safety precautions are taken. Environmental impacts would be fairly limited as well--Not as low as some criticality accidents from test reactors and such, but in a grand scheme of things it wouldn't, I think, impact the ecological recovery of the Exclusion Zone too much.