Science Notes Dangerous Legacy Of Splitting The Atom

Press, Volume C, Issue 29504, 4 May 1961, Page 20

Science Notes Dangerous Legacy Of Splitting The Atom

[By

RITCHIE CALDER]

Getting rid of atomic garbage is one of the world’s greatest sanitary worries. The “garbage-men” who do the worrying are not those who come round and empty our ash-cans but the top brains of nuclear science and the leaders of public health everywhere, and the garbage which concerns them is the inescapable legacy of the splitting of the atom.

Most people are aware of this garbage in the shape of the fallout of atomic bomb tests which can pollute the air we breathe, the food we eat, and the liquids we drink, constituting a threat not only to ourselves and our children but to unborn generations. But scientific, as well as public, concern has trans-

ferred itself to the peaceful uses of atomic energy as well. It makes people nervous about having power reactors in their neighbourhood, or having nuclear-powered ships in their harbours, or nuclearairliners flying overhead. Yet, provided we do not have fallout .oh the scale which we once had, the present amount of atomic garbage, and its disposal, is an expensive item but not a dangerous one. The difficulties lie in the future when we may have atomic power stations everywhere. It has been estimated that by 2000 A.D. the amount of atomic waste, much of it highly dangerous, will be about 120 tons a day. Compare that with radium, the natural radioactive element, of which only 51b existed in the whole world before the artificial splitting of the atom. That is why conferences on waste disposal are becoming as frequent as Saints’ Days. They bring together physicists, chemists, biologists, ecologists, geologists, oceanographers, meteorologists and astronomers. And at a colloquium which I attended some months ago at the University of Chicago, we had lawyers as well. They have discussed everything: can you risk running atomic sewage, containing low-level, practically safe, radiation, into the sea, as the British do into the Irish Sea? By any careful measurement of the effects on the fish and seaweed and so forth, the answer would appear to be "yes”; but the ecologists—the scientists who study the balance of nature—have their doubts. No-one fully understands the food-cycle in the sea and the scientists are worried lest the radioactivity concentrated by lower organisms should eventually get into the sea-food we ourselves eat. Can you dump high-level waste—dangerous, long-lived radio-active elements into the depths of the ocean, and. if so, how deep? Six and a half miles (enough to drown Everest) seem safe enough. But it has been shown that, even in trenches that deep, the interchange between the bottom waters and the surface may take less than five years, so that long-lived radioactive elements could rise to the fishing levels. Then how about firing the atomic ashcans into space, safely beyond our atmosphere? But what if the rocket fails and plummets back to earth? 65 Million Gallons The approved method of dealing with really dangerous wastes is to put them in stainless steel tanks. In these vast kettles the radioactive liquids go on boiling like a witch's brew with the heat which the elements themselves generate. In the United States, at the present time, there are 65 million gallons of atomic sewage bubbling in such cauldrons, and it costs 2i dollars a gallon to provide such storage. This adds up to 162,500,000 gallons, and by any currency valuation it means that it has already cost more to bury the living atom than it costs to entomb the dead pharaohs in the Pyramids.

Multiply that figure several times in terms of the possible world production of waste in the next 50 years and, apart from the expense, you can imagine the vast burial grounds alienated from human use for ever. Yes, for ever. For example, plutonium, which may exist in such waste, has a half-life of 24,000 years. This means that in that time, half the number of present plutonium atoms will have split. In the 24,000 years beyond that, half of what remained will have split, and in the succeeding 24,000 years, half of the quarter, and so on. Salt Mines Sandwiches People were beginning to despair of ever finding a reassuring answer. But at the University of Chicago colloquium Dr. E. G. Struxness, of the Health Physics Division of Oak Ridge National Laboratory, came up with several pretty convincing proposals, mainly on underground burial. One was for using old oil wells. That, subject to many geological reservations, is possible. Even more so, is the use of the galleries of deep of the generated heat, the disposal of solid wastes is salt mines. In these, in spite of immediate practicability. Liquids are more difficult because of the chemical interaction with the salt, but with further research even that eventually may be feasible. And there are plenty of disused saltmines in the world. The most ingenious method, however, is one which has been tried successfully at Oak Ridge—putting radioactive "jam” in a geological "sandwich.” Technically, it is called “hydraulic fracturing.” The geologists established the structure of the underground formations at Oak Ridge and chose * thick shale stratum which conveniently (for the experiment) outcropped on a hill. The scientists then drilled down to 300 feet and fitted a tube 3J inches in diameter. They mixed the liquid waste with portland cement and pumped the mixture down at a pressure of 3001 b a square inch, and at a rate of 26.000 gallons an hour. After four hours’ pumping, the liquid came

squirting out of the hillside. This was experimentally very gratifying (although in eventual practice undesirable) because it showed that the pressure had fractured the shale along a horizontal face (like splitting a lump of coal) and that the liquid had spread over an area 200 feet wide and 400 feet long. Very delicate measurements showed that the mixture-under-pressure had lifted the ground a fraction of an inch. Solid Sheet When the radioactive concrete set, it formed a solid sjheet an eighth of an inch tjhick securely sandwiched in in an impermeable bed of Shale. Even the earthquakes which have been known to occur in the area would not dangerously dislodge it. They sank another drilling to a depth of 1500 feet into the same shale formation and successfully repeated the experiment. Then they filled up the tube half-way and injected the mixture at 750 feet, again successfully. This showed that the shale could be laterally fractured at any depth and that even dangerous radioactive wastes could be safely cemented into the ground. This suggests that, in the future, similar rock formations should be chosen as the sites for nuclear separation plants, because it is in the chemical extraction of fissile fuels that the dangerous wastes are produced—not at the nuclear power-stations.— (U.N.E.5.C.0.)