Alright someone help me out. I'm looking up radiation measurements and the online information is all over the place; one says a lethal does is 5 Sv while another says 1000 is radiation sickness.
xkcd posted what appears to be an excellent chart explaining radiation doses: http://xkcd.com/radiation/
A radiologist friend of mine confirms that 5+ Sv is generally considered a fatal dose (assuming you trust her) Her guess is that whatever source said that 1,000 Sv results in radiation sickness probably meant 1,000 mSv, which = 1 Sv.
According to my calculations, it would take ~ 3 weeks of living in the final place where they got out, 1.5km from the plant, to be at a statistically significant higher risk for cancer.
It would take almost 8 months of living at that close proximity to suffer from mild radiation sickness (headache, increased risk of infection).
A few more months, and you will begin to die. Nausea, and fatigue are more symptoms. Even if you the leave zone, there's still a 10% chance that you'll drop dead within a month.
If you're made of steel, and you're somehow still alive after two and a half years, you will be hairless and permanently sterile.
My calculations don't indicate at which point you turn into a ghoul.