How to properly dispose Radioactive Wastes?

Only the process of natural decay which requires hundreds of thousands or even millions of years reduces the radioactivity of nuclear wastes.

There is no physical, chemical or biological process which can reduce this span of time. All we can do is to store the radio-active material at some remote place away from the biosphere for a million years – task which is too difficult for the mankind. High level irradiated wastes also produce a lot of heat and hence have to cooled to avoid explosion of the cask or the containers in which they are kept.

Ever since the beginning of nuclear age a number of options have been put forth for the isolation of radio-active wastes from the biosphere some of which may be summed up as follows:

1. Burial under Antarctica Ice-cap:

A leakage could be catastrophic. With temperature changes ice could melt disturbing the burials. Abandoned.

2. Burial under sea bed:

The radio-activity may leak out in the surrounding waters and from there to other places. Abandoned.

3. Disposal in space outside earth’s gravitational field:

A single launch failure could introduce the radio-activity in the atmosphere from where it can contaminate the entire planet. Abandoned.

4. Disposal deep underground surface:

This involves difficulties arising due to ground j water flows and uncertain geology which may cause tectonic disturbances, volcanic ac-1 trinity etc. Moreover human intrusion over such long periods of time may not be ruled out. I However, this proposal has been followed till date.

5. Burial in specially constructed buildings under human care:

The proposal involves too much dependence on human care which may not be possible for such long periods of time as required.

6. Reprocessing of nuclear wastes:

Chemical separation of uranium and plutonium from nuclear wastes reduces the radio-activity by about 3% but increases the volume of wastes j almost 150 times. Hence, abandoned.

7. Transmutation to isotopes with shorter half-lives:

Bombardment by neutrons may convert isotopes with long half lives into isotopes with shorter half-lives. However, there are many technical uncertainties in the process which can be dangerous as well. The method is, anyway, enormously expensive. It is already under active study.

At present much of the scientific opinion is in favor of burying the high level irradiated wastes deep inside earth’s crust. However, an important factor in such burials is underground water table which feeds a number of fresh water deposes and rivers on earth’s surface. Tectonic movements of rocks and volcanic activity may also disturb these burials.

The United States Government’s Dep’t of Energy has proposed two such deep burial sites-1 the projects which may be considered as representing the best of human efforts. One at Nevada’s Yucca Mountains and another, called Waste Isolation Pilot Plant (WIPP), in South-eastern New Mexico.

The Pilot Plant at New Mexico has burial rooms 600 metres deep amidst salt formations under which there is a large reservoir of saline water (the brine). Under the brine runs a ground water aquifer which feeds a branch of river, Rio Grande. The brine constantly seeps through walls of repository. It can easily damage the steel containers and create radio-active slurry.

The heat produced by wastes could cause an explosion and leakage will follow which could contaminate the under­ground fresh water aquifer. At Yucca Mountain Nevada, whose rock formations are crises-crossed by at least 30 seismic faults deep burial is proposed at a depth of about 300 metres, immediately below which there is a fresh water aquifer.

If, due to seismic activity or tectonic movements or volcanic activity, this water comes in contact with the nuclear wastes the heat generated could produce enough steam to blow off the plug at the top of the tunnel. Or else the radio-active material shall contaminate the ground water aquifer which feeds many hot springs in the Death Valley of Nevada, USA.

Thus mankind’s enormous knowledge bows low before the challenge of isolating nuclear wastes from the biosphere for periods long enough to convert them into a harmless state. It is note­worthy here to remember that there was no English Channel only 7000 years ago, that volcanoes abounded in what is now Central France barely 10,000 years ago and that Sahara desert was a fertile land only 5000 years ago. In a world of such a rapid change it appears almost impossible to find a safe, inviolable and permanent resting place for the nuclear wastes for periods as long as hundreds of thousands or millions of years.