Thank You for the replies.
I have tried a few thing and there seems to be no change.
I destroyed and rebuilt.
Set up water plant with max filtration right next to nuclear plant. Doesn't seem to help in fact it doesn't clean 100% of the water and puts contaminated water into the system.
I have yet to try the parks.
I believe the cause was I built the nuclear plant with one elementary school in the town. I then notice a worker education tag in the nuclear window start out "safe" then turned to "unsafe" then the meltdown. I have since built a high school, now it indicates safe. So it defiantly appears your education level must be at least high school to avoid this.