Million Year Pollution Tude at Threat

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Great efforts are being made to cover up the legitiof the processes used in the latest plans for developing nuclear energy with a new series of Fast Breeder reactors.

The new technology alongside its huge potential benefits if properly developed, also has the potential to cause spectacular destruction.

Nuclear reactor programmes remain beseiged with: safety problems: weaknesses in reactor emergency systems; poor control over operating procedures; and the unsolved problem of the ultimate disposal of nuclear wastes have attracted particular attention.

In fact, at virtually all points during the nuclear fuel cycle (from the mining, through processing and transportation, right up to utilisation and storage of nuclear materials) there are opportunities for people to be exposed to significant radioactivity or for other hazards to arise.

HAZARDS

To understand the new problems we must look at the hazards involved in the generation of power by nuclear reactors.

The two most common nuclear fuels are a type of uranium which constitutes only 0.7% of natural uranium, and a substance called plutonium, which apart from small traces in uranium ores occurs only as a by-product in some nuclear reactors.

They are utilized in powergenerating reactors in several different ways, but the basic principle is the fission, or fragmentation, of a fissile atom.

This process is initiated when the atom is struck by and captures an atomic particle known as a neutron.

This process can be likened to the disintegration of a large liquid drop on shaking to give two medium size drops and a few tiny drops. The medium sized drops are analogous to neutrons.

These neutrons may interact with other fissle atoms to produce further fission reactions, and so the process continues (a chain reaction).

Heat produced by the fission reactions is used eventually to boil water. The resulting steam drives turbines which are linked to electricity generators.

FAST BREEDER

A fast reactor, so called because of the speed of the neutrons involved in its fission reactions, is smaller, hotter and contains more plutonium than a conventional thermal reactor.

This means that a very efficient coolant is needed.

By careful design of a fast reactor's fuel elements and by surrounding them with suitable uranium oxide elements it possible to create more plutonium than is consumed. Hence the term Fast Breeder Reactor.

Special safety hazards in the fast reactor can arise from sudden surges of extra power as the reactor core (where fission reactions occur) takes up new positions in use.

If tha ento of tammandia.

is very rapid the core could melt and the molten fuel and the liquid sodium used as a coolant interact explosively.

Thermal reactors do not show a sudden surge in power as the fuel changes position, but an accident involving a loss of coolant or failure of other means of controlling processes in the reactor core could also result in its melting.

REACTOR FAILURE The containment system (ie a pre-stressed concrete vessel around the reactor core, and the reactor building) may then be breached and radioactive substances released to the atmosphere.

A recent report from the Health and Safety Executive, who now have the responsibility of the old Nuclear Installations Inspectorate, describes an official view of a fast reactor on a semi-urban site overheats, melts and becomes partly vapourised, and its container fails.

If only one tenth of the reactor core vapourises this:

"would cause several thousand deaths within a few weeks of the accident" and some tens of thousands of cancer deaths" may occur in • an area extending for "a few hundred kilometres downwind" over the next few decades.

burial ground for contaminated reactor machinery "Land and dwellings" would be unfit for occupation "for some tens of kilometres downwind" , and farm produce at even greater distances may have to be destroyed.

The report arrogantly notes:

"in sum total, these effects, though serious, would not be insupportable by society"

Such is their contempt for workers' lives.

Reprocessing of fast reactor fuel elements involves dissolving the fuel from its cladding and separating out the plutonium, uranium and intensely radioactive fission products.

The safety hazards here centre around the handling and storage of the highly .. radioactive waste dea - e1.

plutonium.

In appropriate concentrations plutonium, like other fissile materials, can produce a spontaneous, uncontrolled, fission chain reaction; this is the property made use of in atomic bombs.

Ten accidents involving uncontrolled chain reactions are known to have occurred resulting in several workers being injured and some deaths.

Plutonium is perhaps the most toxic element known and has no antidote. Amounts as low as one millionth of a gram can be hazardous in lungs and bone.

Its toxicity results from its radioactivity and the fact that once it gains access to the body it is retained for long periods «half-life" (ie the time taken for half the atoms to lose their activity)-of some 24,400 years!

POISON

The movement of three tons of plutonium every year from British reactors to reprocessing sites has been suggested as likely should FBR's be established in Britain.

This represents 5,000,000,000,000 times the maximum permissible body burden laid down by statute in this country. A phenomenal amount of poison!

If the handling of plutonium increases as FBR's and re-processing plants are established, the chances must be that the number of accidents will also increase.

The high activity wastes of nuclear reactor programmes prevent the most enduring safety problems. The wastes are of two types; fission products and a group of elements, which includes plutonium and uranium, known as the actinides.

TANKS

At present, fission products are stored as acid solutions in cooled, stainless steel tanks.

This temporary means of storage is necessary because so little is of these wastes that no acceptable method is yet available.

Provided that they can be separated from actinides with a high degree of efficiency then converted to glass and stored in a stable geological formation, they would decay to manageable activities only after about 800 years.

PILOT

Anyway, development of the process for converting liquid wastes to glass has so far only reached the pilot plant scale.

The actinides themselves and the products of their spontaneous decay, however, remain a hazard for millions of years. There is no convincing method available for their storage or conversion to manageable substances.

Four methods for the disposal actinides are being studied present.

These are: burial in deep and stable geological formation; burial under the floor of the deep ocean; emplacement in suitably long-lived containers on the bed of the deep ocean; and irradiation in a suitable reactor to convert them to shorter lived materials.

The first method begs the question; what geological formation can be considered stable over a geologically significant period of time?

::0900 Even the Health and Safety Executive admit that the second would be difficult to achieve.

As to the third, it would be difficult to prove the integrity of the containers for millions of years, under the action of plant and animal life and the corrosive action of the sea itself, Furthermore, human operations may uncover these stores of radioactive materials.

For example, in 1962 containers holding low activity radioactive wastes were recovered by French trawlers in the English Channel!

The fourth method is also acknowledged by the Health and Safety Executive as having daunting technological difficulties, but is the most satisfactory of the ones mentioned.

DESIGNED TO LEAK

Even this, however, would yield materials that at best would remain highly dangerous for 500-800 years.

The disposal of low and moderate activity wastes also present a hazard to life. At present, solid wastes contaminated with small amounts of plutonium and other activities are dumped on the sea bed in containers designed only to protect their contents on the way to the sea bed.

They are designed to leak and are never. expected to retain their contents for more than ten years.

In 1964 a number of drums holding low activity wastes actually failed on impact with the surface of the sea.

Low activity liquid wastes from reprocessing and fuel fabrication at Windscale and Dounreay are discharged to the sea through pipelines.

In both cases the large volumes of sea water are expected to dilute the dangerous radioactivity to levels acceptable to government inspectors.

However, local concentrations of radioactive materials can still develop, especially near the dumping grounds and this may affect marine life.

In any case, dilution has not always been achieved. Radiation levels in the Celtic Sea have caused a greal deal of concern. One type had risen to 83% of permitted levels by 1975, and there has been a tenfold rise in the levels of radioactive caesium in fish between 1973 and 1975.

By a science correspondent

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tre LONDUN PRESS ¡EWISHAMN & DEPTURE

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mate worries of many workers and scientists about the safety