Long-term storage on land seems to be the favorite of most countries.
a) Disposal of Nuclear Waste in Space
Outer space is the most appropriate long-term storage option for high-level nuclear waste. This would ensure it's safe removal from humans regardless of the activities of nature or man on earth. Anybody accidentally stumbling upon this waste would be at a lesser risk as they would be using radioactive shielding for space travel. Delivery of the waste into space has a crippling drawback -- the rocket used to deliver the waste into space would need to provide enough power to escape the earth's gravity. This is necessary for two reasons: a) to leave the waste in orbit creates space garbage that is likely to reenter the earth's environment at some time due to collision with satellites and other orbiting waste or spacecraft; and b) the large delivery rocket would be expensive and an accident during launch could have catastrophic results. Space disposal therefore, will not be a viable option until space travel is considerably safer and less expensive.
b) Storage of Radioactive Waste in the Sea Bed
A possibility for long-term storage on the earth is burial in the seabed. The rock formations in the seabed are generally more stable than those on land reducing the risk of exposure due to seismic activity. Apart from this, there is little groundwater circulation under the seabed, reducing the possibility of radioactive material contaminating ground water available for human consumption. The greatest appeal of under sea burial is also its greatest drawback. The enormous cost and difficulty of excavating the waste would likely prevent accidental or malicious disturbing of the waste. This cost is also keeping us from burying the waste at sea.
c) Long Term Storage of Radioactive Waste on Land
Long term storage in tectonically stable rock formations on land is the most likely solution for high-level radioactive waste. The radioactive material may be vitrified1 and buried in caverns, created in a large rock formation. When use of the storage area is complete, it would be sealed again with stone. While still extremely expensive, and considerably unsafe, this is the most viable storage option currently available. Using methods that reduce the amount of radioactive waste could further enhance safety levels.
(Useful for UPSC General Studies, APPSC Group 1 Group 2 , Mains Material, Paper 1, Paper 4 Section 1 Section 2 Section 3, ROLE AND IMPACT OF SCIENCE AND TECHNOLOGY IN THE DEVELOPMENT OF INDIA, GENERAL AWARENESS WITH THE MODERN TRENDS IN LIFE SCIENCES, DEVELOPMENT & ENVIRONMENT PROBLEMS)