what is radioactive waste and why is it stored underground
Check these sites.
http://en.wikipedia.org/wiki/Radioactive_waste
http://www.radwaste.org/storage.htm
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.
but why is it stored underground is it because it is harmfull to people
Be sure you read and understand ALL of what Drwls wrote. He answers your question.
Radioactive waste refers to materials that contain radioactive substances, which are byproducts of various human activities such as nuclear power generation, medical treatments, industrial applications, or research. These materials emit ionizing radiation, which can be harmful to living organisms and the environment if not managed properly.
One common method of storing radioactive waste is underground repositories. This approach offers several advantages:
1. Shielding: Underground storage provides natural shielding from the surrounding rocks and soil. The layers of earth act as a barrier, reducing the exposure of radiation to people and the environment.
2. Containment: Deep geological repositories are typically located in stable rock formations, such as deep underground salt deposits or granite formations. These geological formations have low water permeability, reducing the risk of leakage and preventing the waste from interacting with groundwater.
3. Isolation: The main purpose of storing radioactive waste underground is to isolate it from the biosphere for an extended period. The intention is to prevent human exposure to radiation during the waste's long-lived radioactive decay process, which can extend for thousands of years.
To determine the suitability of a site for radioactive waste storage, extensive geological studies are conducted to assess factors like the stability of the rock formations, hydrogeology (movement of water underground), and the absence of faults or fractures that could potentially facilitate the migration of radioactive materials.
It's important to note that the choice of storage method ultimately depends on the specific characteristics of the waste, the level of radioactivity, and the regulations and policies of each country. The goal is always to ensure long-term safety and protect the environment and future generations from potential harm.