The Nuclear Waste : The Unsolvable Problem

waste.gif - 11.65 K To some extent all uses of energy affect the environment adversely. But over the centuries, waterwheels grinding grain, windmills pumping water, and animals ploughing land did little environmental damage.

The damage really began in the seventeenth century with the invention of the steam engine and mining coal to fuel it. Growing volumes of waste effluent from burning coal, and later the other fossil fuels, oil and gas, have brought us to the environmental crisis facing us today.

Now in the twentieth century forests die from acid rain, marine life is blighted by oil spills and urban populations suffer health problems from the smog created by commuter traffic.

Cleaner burning of fossil fuels could do a lot to reduce the pollution. However, we now discover that the seemingly innocuous carbon dioxide from burning vast quantities of fossil fuels has been warming our globe since the industrial revolution. Though far from the only culprit carbon dioxide is the major offender.

Uranium is a fuel that releases no carbon dioxide and so it seems a promising candidate to displace fossil fuels at least to generate electricity.

That nuclear power has serious problems is now generally acknowledged even by its advocates. However, climate change can be expected to bring great social disruption; so why not solve the problems of an energy source which emits no carbon dioxide.

The nuclear problem arousing most public concern is the disposal of radioactive waste. Wherever waste disposal sites are chosen local opposition has forced the plans to be cancelled.

Radioactive wastes are produced at all stages of the nuclear fuel cycle. The wastes are stored as liquids or solids.

When considering the nature of nuclear wastes it is helpful to see the nuclear fuel cycle as having a 'front end'' ­ production of the fuel for the nuclear reactor ­ and a 'back end' ­ storing and reprocessing the spent-fuel.

The 'Front End'

Mining

Waste discharge into the environment begins with mining uranium. Although the radioactivity of the wastes is low-level the volumes left behind at abandoned mining sites are huge.

Only about three kilograms of uranium oxide are recovered from each tonne of ore. The left-overs, looking like liquid mud and called tailings, are pumped into a tailings dam.

After mining ceases tailings dams become hills of fine sand which retain 80 per cent of the radioactivity in the ore body. Thorium-230 in the tailings decays into radium-226 which in turn decays into gaseous radon.

Before mining, these and other radioactive elements are locked into impervious rock; little of it reaches the open environment. Once mined they get into waterways and the atmosphere. Tailings are so finely ground that the radon escapes 10,000 times faster than from the ore body.

Tailings dams have a poor track record. Waterways have been polluted by radium after a sudden collapse or constant erosion. Radon gas and radioactive dust are carried downwind. Since radioactive decay will persist for over 100,000 years the hazard will be virtually without end.

Most of the world's uranium has been mined in the poor African countries of Namibia and Niger and on the remnants of land left to the indigenous people of North America. The mining sites have become radioactive wastelands bringing devastating health problems to indigenous peoples.

Until the mid-1980s Colorado Plateau in the south-west of the United States provided half the world's uranium.

The mining on the plateau is in the dry lands of the Navajo people who were promised jobs and wealth if they accepted mining. Today their lands are poisoned by dry dusty hills of tailings; winds spread radioactive dust and radon gas gets into the atmosphere. Aquatic creatures concentrate radium in the waterways up to 10,000 times.

Navajo communities fear the consequences of eating the food they grow because it has elevated levels of radioactivity. They suffer an epidemic of cancer and birth defects.

A report by the Los Alamos laboratory, a leading centre of nuclear research, says the health problems created by uranium mining may be irremediable. The report says the only solution could be "to zone the land in uranium mining and milling districts to forbid human habitation".

Australia has wastelands of its own, a legacy of mining uranium in the past. They are a portent of what could happen at Ranger and Roxby Downs after mining ceases.

Uranium ore mined at Radium Hill in South Australia was once processed into yellowcake at Port Pirie situated on the Spencers Gulf. The radioactive tailings from the operation were left to be washed away by high tides and eroded by high winds.

At Mary Kathleen in Queensland tailings, which were poorly rehabilitated with a crushed rock cover, now seep radioactive waste into underground waters.

In the Northern Territory monsoonal rains breached tailings dams of abandoned mines at Northern Hercules and Rum Jungle poisoning long stretches of the rivers below them.

Ranger mine is situated in the Kakadu National Park listed as a World Heritage. Australia is committed to protect the park's natural wonders. The mine's tailings dam, situated in the path of monsoonal floods that pour down into the park's unique wetlands, symbolises Australia's failure to live up to its commitment to protect this natural heritage.

Each wet season monsoonal downpours flood the mine; the run-off carries radioactive pollutants. The water from the around the mine, called a 'restricted release zone', is directed into retention ponds where it is meant to evaporate during hot summer months.

However ERA failed to design the ponds to cope with the rains deposited in unusually wet seasons. The company has lobbied persistently to be allowed to release this contaminated water into nearby Magela creek. The pollutants are being carried into the wetlands where they concentrate in the silt over the dry season.

Aborigines living downstream, whose food comes from hunting, fishing and gathering from the land, oppose such releases.

The Ranger Uranium Environmental Inquiry recommended the tailings be returned to the pit when mining ceases. ERA wanted the tailings to be left as a terraced hill. Inevitably as the hill eroded radioactive sands would drift into the creek. Aborigines insist they be returned to the pit. Even so pollutants will leach out infinitely faster than occurred before mining.

At Roxby mine the tailings dam could one day be the highest landform in the area. Here too evaporation was supposed to remove all the water from the dam. However, water has seeped through underlying porous limestone formations to contaminate the ground waters.

Planned rehabilitation amounts to no more than a thin covering of soil and vegetation, a poor defence against desert winds for thousands of years. As time passes the tailings will erode and creep like sand dunes across the wind-swept arid plains towards the farmlands and towns to the south.

The Reactor Fuel

The enrichment and rod fabrication plants, which transform uranium into reactor fuel, create liquid, solid and gaseous wastes with low radioactivity.

There have been innumerable accidents with nuclear cargoes carried between plants at the 'front end'. Though low in radioactivity the spillages have spread contamination far and wide.

Volatile 'hex' (uranium hexafluoride) is especially hazardous both as a chemical and for its radioactivity. Its release in a serious accident, occurring in a populated area, can have catastrophic consequences for people's health.

The 'Back-End'

Every 12 months or so a reactor is closed down in order to replace one-third of the fuel rods (about 30 tonnes) with fresh ones.

About a third of the uranium-235 in the rods is still 'unburned' but waste fission products smother the nuclear reactions just as ash does a coal fire. However, the nuclear 'ash' cannot be shaken through a grate; it can only be separated by removing the fuel rods.

Spent fuel contains 1 per cent plutonium and other transuranic elements and 3 per cent fission products. The remainder is mostly unchanged uranium-238.

Spent-fuel straight from a reactor emits fierce heat and lethal radiation and must be handled by remote control. The radioactivity of 30 tonnes of spent fuel (from one year of operation) is equivalent to 5000 tonnes of radium. It is stored in water-cooled ponds on the reactor site.

Within 15 days the radioactivity drops to about one-tenth. Thereafter it remains a slowly decaying hazardous material for thousands of years.

Most nuclear power countries have now settled for one of two strategies to deal with spent fuel :

Reprocessing

Reprocessing was first developed for the isolation of plutonium for nuclear weapons. Commercial reprocessing was developed later to provide plutonium for breeder reactors designed to produce more plutonium again than they 'burn'.

The first reprocessing plant was opened in 1963 at West Valley, New York State. Governor Rockefeller described it as a "unique operation and a symbol of imagination and foresight". Six years later the plant was too 'hot' to handle and had to close.

Two commercial reprocessing plants presently service the world's reactors. One is at Sellafield in Cumbria, Britain and the other at Cap La Hague in Normandy, France.

Reprocessing begins by chopping fuel rods into pieces and dropping them into a tank of nitric acid. A solvent is added to extract the uranium and plutonium. The acid solution containing the fission products is separated off and concentrated by evaporation. This is high-level liquid waste which is stored in cooled tanks.

The dissolved plutonium and uranium are separated from each in another solvent fractionation. The plutonium is stored in vaults as small specially shaped pieces to prevent a build-up of neutrons which could cause an explosion. The recovered uranium is depleted in uranium-235 and requires enrichment before use as a fuel.

Reprocessing plants are the source of about two-thirds of all the low-level liquid and gaseous wastes produced in the nuclear fuel cycle.

At Sellafield millions of litres of effluent carrying plutonium and other transuranic elements and fission products are discharged daily into the Irish Sea.

Plutonium has become absorbed on seabed silt which is washed on to nearby beaches making them dangerously radioactive. Ocean currents carry radioactive waste as far away as the Scandinavian coast.

Cumbrian people have more plutonium in their bones than any other people. Cesium-137 and strontium-90 in fish caught in the local waters are 200 times higher than fish taken from Atlantic waters. Local fish shops carry a notice "No Irish Sea fish sold here".

The nuclear industry had planned to operate breeder reactors commercially by the 1990s. It has failed to happen and is unlikely to do so in the foreseeable future. This removes any commercial justification for reprocessing.

Plutonium decays faster than uranium; if not used as fuel within three years it must be reprocessed to remove decay products. Some plutonium is used with uranium in 'mixed oxide' fuel in conventional reactors. However, plutonium from reprocessing is three times more costly than uranium.

Waste Disposal

Wastes are commonly classified according to their level of activity.

High-level waste

After 40 years of nuclear power there is still confusion and uncertainty about what will happen to its wastes. Not a single kilogram of high-level waste has yet been disposed of in a permanent repository. The problems are political as well as technical.

Meanwhile spent fuel continues to accumulate. Three quarters of the spent fuel so far produced is still being stored at reactor sites or in interim storage depots.

In the once through cycle spent fuel becomes the waste to be disposed of. It is envisaged that the rods will be held in cool storage up to 100 years or longer to allow heat and radiation levels to drop to manageable levels.

According Swedish nuclear authorities the rods will eventually be prepared for disposal by placing them in copper canisters about a metre diameter and four metres long. Copper powder will be poured into the space between the rods. The canisters will then be placed in a deep repository.

In the closed cycle the high-level liquid waste from reprocessing is solidified. France and Britain have plants for putting waste into glass. Japan and the United States plan to use ceramics.

The waste is first evaporated to a solid powder. A year's waste from a large reactor is reduced to about a cubic metre. This is a relatively small volume but it is horrendously lethal retaining radioactivity equivalent to as much as 10 tonnes of radium.

Glass or ceramic powder is mixed with 10 per cent of the evaporated powder, melted and poured into canisters. The canisters are to be held in cold storage until a decision is made on what will be their final resting place.

The uncertainty surrounding the ultimate fate of the solidified waste is evident in the recommendation of the British Waste Management Advisory Committee to store the solidified waste "for at least 50 years ...a decision could then be taken on whether to continue to store these wastes: deep underground, on the ocean bed or under the ocean floor".

After vigorous protest by Greenpeace in their Zodiac boats on the high seas a moratorium on ocean dumping of rasioactive waste was declared in1994. The London Dumping Convention later banned ocean dumping permanently.

Permanent Deep Disposal

The solution generally favoured by nuclear industry to get rid of its high-level waste is to bury it in geological formations of granite or basalt. Kilometre deep holes would be bored into rock, canisters lowered into them and then they would be sealed off with concrete. Or else caverns or tunnels will be dug deep into rock or salt formations.

Sweden, which decided by referendum to cease generating nuclear power by 2020, has chosen to use the 'once through' cycle. It plans to build a repository, called a 'laboratory', consisting of a tunnel, 3500 metres long and spiralling down 500 metres.

Canisters will be deposited in holes, drilled into the rock floor, and covered with bentonite powder and sand. When the tunnel is full it will be sealed off with concrete.

The copper canisters are expected to erode badly within 1400 years. By then almost all fission products will have decayed to stable elements but plutonium and other transuranics will have lost little of their activity. Effectively the only barrier against the plutonium escaping is the rock.

Says Nils-Axel Morner, a leading Swedish geologist on rock movement: "Never trust a rock". That a rock has survived a million years says nothing about its future stability...When one piece is pushed the whole thing moves".

Radioactive Rubbish

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Nuclear industry like other industry creates bulky rubbish ­ paper, plastics, gloves, clothing, equipment, tools ­ with the difference that it is radioactive.

Some of this rubbish was buried at sea until action by Greenpeace and nations with fishing interests caused the practice to be banned. Much of this radioactive rubbish has been buried in shallow land graves or sometimes in disused mines. Plutonium and other radioactive elements have migrated from these dumps into the surrounding environment.

The more highly contaminated rubbish, classed as intermediate level, is made up of the cladding on fuel rods, glove boxes for handling plutonium, sludges and other waste contaminated with long-lived transuranic elements.

Britain will bury intermediate-level waste in trenches roofed and lined with concrete. Waste, broken into bits, will be dumped into the trenches and mixed in concrete 'like currents in a cake'.

Politics of waste disposal

People naturally do not want nuclear waste on their doorstep. In 1986, the British government announced sites for dumping low-level waste. One politician from a designated area, conservative though he was, threatened that his constituents would "launch a guerilla war against the authorities".

France is held up as an example of a country where people are reconciled to nuclear power. If so it does not extend to the waste. All government attempts to test suitable rock formations at selected sites have had to be abandoned in the face of vehement public protest. The French government, like most other governments, have shelved preparations for a deep repository "until sometime next century".

The Beijer Institute, in Sweden, analysed waste disposal plans of the nuclear countries. It concluded any solution to the problem of disposing of high-level nuclear waste is 'transcientific' ­ that is beyond the bounds of science. For the safety of any waste repository, over a hundred thousand years and more, can never be proved.

The data on waste performance can only be gathered over a short timespan compared to the time wastes remain hazardous. In this respect nuclear wastes differ from other wastes.

Technical solutions, like the Synroc process, touted by the Australian Nuclear Science and Technology Organisation, have no relevance to the timeless hazard of the waste. Any scientist with a solution will not live long enough to test their 'discovery'.

Clearly the nuclear waste problem outweighs any gain from no carbon dioxide emissions. We must look to another energy source, which also emits no carbon dioxide ­ the renewable solar energies.

A National Repository

The federal government has begun studies on finding a suitable site 'for low-level and short-lived intermediate level radioactive waste'.

Overseas practice suggests that either shallow-land burial or near-surface concrete structures will be used. The waste would be paper, plastics, glass, clothing, metals, instruments and soil. The waste comes from medical practice, research and industry.

Suitable sites are being sought at Maralinga and around Cooper Pedy in South Australia, around Broken Hill in New South Wales and at Mount Wilson in Western Australia.

All governments support the concept of only one national repository but all are shy about offering to host it. Only the NT Government expressed interest but after a feasibility study it too lost interest.

Clearly community opposition to radioactive waste, even when it is low-level, being dumped in their state is the reason for politicians being so shy about hosting a national repository.

Conservation groups argue that responsibility should lie with the waste makers to care for their own waste. That would encourage them to minimise their waste making or find alternatives.

Since the repository is to be commercial those in charge will be likely to encourage waste formation and even seek to import nuclear waste to get the highest return on their investment.

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The question is can we keep accumulating and dumping radioactive wastes or should we be reconsidering the worth of nuclear power as a way of generating our electricity.

Information from the MAUM public education sheet on Nuclear Waste.
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