Question

what is radioactive waste and why is it stored underground

Answer 1

Check these sites.

http://en.wikipedia.org/wiki/Radioactive_waste

http://www.radwaste.org/storage.htm

Answer 2

There are many kinds of radioactive waste: high-level, low level, mixed, and transuranic. All contain radioactive material that emits a high enough level of alpha, beta or gamma rays to be hazardous to humans who spend too much time in the vicinity, or if the material seeps into rivers or ground water. Some types such as "transuranic" are sometimes stored below ground in salt mines and some, such as "high-level" reactor waste, are stored in containers above ground for continuous monitoring until a permanent storage facility can be approved.

Answer 3

but why is it stored underground is it because it is harmfull to people

Answer 4

Be sure you read and understand ALL of what Drwls wrote. He answers your question.