FOR THOSE Europeans in need of a drink after the first bout of nuclear
war, Denmark looks like being the best place to head for. Whatever the strength
of the tipple required, water will be the main ingredient and Danish water
seems bound to be the safest around. Radioactive material from nuclear fallout
would quickly contaminate stretches of open water, such as rivers, streams,
lakes and artificial reservoirs. In most of Europe, these sources meet much
of the
demand for water, around three-quarters of it in Britain and Ireland,
Spain, Portugal and Greece. In Denmark, they provide just 1 per cent of
the water supply. The Danes receive most of their water from natural reservoirs
below ground, from pockets in fissured rock to deep aquifers sealed by layers
of semipermeable minerals. Radioactive particles cannot easily reach these
ground-water sources. As fallout breaks into the food chains that provide
milk, cheese, fruit, vegetables, meat and eggs, there may not be much that
is safe to eat anywhere; in Denmark, however, there should be enough to
drink for a while.
This wry analysis comes from Derek Miller, the assistant director for
environmental standards at WRc Medmenham, a British company based in Buckinghamshire.
Until April this year, the organisation was known as the Water Research
Centre, a research association with members drawn from government and industry.
With the government about to privatise the water industry in England and
Wales, the organisation saw a management buyout as the only way to maintain
its neutrality and independence. The Water Research Centre provided advice,
expertise and a shoulder to cry on for Britain鈥檚 water industry; the new
firm still does much the same job, says Miller. Speaking in Glasgow last
month at an international conference on 鈥榃ater Resource Consequences of
a Nuclear Event鈥�, organised by the Institution of Civil Engineers, Miller
was voicing the industry鈥檚 confusion and concerns at the lack of information
about what to do if water supplies become contaminated, whether through
war or as the result of an accident at a nuclear power station.
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The main radioactive elements involved are isotopes of iodine, strontium,
caesium and ruthenium. Iodine accumulates in the thyroid gland; strontium,
which is chemically similar to calcium, is readily absorbed through the
walls of the intestines and collects in the bones; while caesium is chemically
similar to potassium, and is distributed throughout the body. Ruthenium
appears to have no chemical analogue with a biological function. Radioactive
iodine is a serious hazard only immediately after a nuclear event; the isotope
decays quickly (it has a half-life of about eight days) and the thyroid
gland can be saturated with safe iodine, taken in tablet form, so that it
does not accumulate any more of the chemical. Isotopes of strontium and
caesium are too widely distributed throughout the body for tablets to help
in controlling their accumulation; and, like ruthenium, their isotopes decay
slowly (their half-lives range from about 40 days to more than 30 years).
Miller is concerned that the industry has little idea of how effective
its methods for cleansing water will be: 鈥楥omprehensive studies have not
been carried out to measure the effectiveness of treatment for removing
those radionuclides typically released from accidents involving nuclear
reactors.鈥� He says measures are in hand to improve the situation but that
there is still a long way to go.
For a start, there are too many guidelines with widely varying recommendations
on how radioactive water can be, and still be safe to drink. International
authorities, such as the World Health Organization, the International Atomic
Energy Agency and the International Commission on Radiological Protection,
all provide different advice; and many countries draw up their own national
standards. 鈥楾he public might well be confused by the existence of so many
limits,鈥� says Miller. 鈥楾here is likely to be difficulty in understanding
why they vary by almost seven orders of magnitude, even though a scientific
basis can be put forward for this range.鈥� Fortuitously for Britain, the
National Radiological Protection Board had reviewed all the contemporary
advice available and published its own guidelines in March 1986, one month
before the accident at Chernobyl. In the absence of a unified directive
from the European Commission, these guidelines formed the basis of the NRPB鈥檚
advice to the public not to drink rainwater continuously in the week following
the arrival of the Chernobyl cloud over Britain.
Three years later, the European Commission has just produced a regulation
covering the levels of radioactive contamination allowed in foodstuffs,
including drinking water. After Chernobyl, a team of experts had recommended
limits which, when exceeded, would trigger controls on the consumption of
food and water after a nuclear incident. The team originally examined 19
radionuclides and five classes of foodstuffs, but in an effort to produce
a guide that was relatively simple to apply, it restricted its recommendations
to just three radionuclides and four classes of foodstuffs. After much debate
and consultation involving the Council of Ministers, the Economic and Social
Committee and the European Parliament, the commission then drew up a new
set of values.
According to George Fraser, principal administrator for nuclear safety
and civil protection in the commission鈥檚 environment directorate, the changes
result from a combination of factors, not all of a scientific nature. For
dairy produce and other major foodstuffs, including drinking water, the
commission reduced the recommendations of the experts generally by a factor
of four 鈥榯o take account of values applied outside of the Community and
to maintain public confidence鈥�. Furthermore, says Fraser, the official values
will be temporary ones that come into force during an emergency and then
only 鈥榯o provide an orderly basis for trade to continue in the period immediately
following an accident鈥�. This means that they will apply only to water reaching
the consumer in bottled or canned form. The results, says Miller, could
be bizarre: he foresees the commission withdrawing bottled water from sale
because its radioactivity exceeds the emergency limit, but refusing to advise
water authorities to cut off mains supplies even though water from the tap
is more radioactive.
Miller also notes that treating contaminated waste water and sewage
could be a problem because of the build-up of radioactivity in the sludge,
which would put plant operators at significant risk. 鈥楨ven at the relatively
low levels of activity encountered in raw waters following Chernobyl, sludges
in a number of European states became sufficiently active to require special
attention before disposal,鈥� he says.
Since Chernobyl, radioactive contamination of water supplies has dominated
the thoughts of scientists and engineers working in the water industry.
It has especially concerned those in Europe, which was most affected by
fallout from Chernobyl, leading them to look more closely at what happens
when rain brings a cloud of radioactive elements down to the ground. The
industry was totally unprepared for what happened; many staff were not even
familiar with the units of measurement of radioactivity, let alone with
methods of monitoring the contamination and purifying irradiated water at
its treatment works. Strict laws, policed by specialised teams of pollution
inspectors, control what the industry had perceived as the main threat of
contamination: effluent discharged from nuclear power stations or other
sites where nuclear processes are going on.
As it turns out, the levels of contamination of water supplies recorded
across Europe, and North America, appear to have been very low. Radioactive
elements in the cloud dispersed naturally as the fallout spread away from
Chernobyl; and rivers and reservoirs, which collected the contaminated rainwater
as it ran off land, diluted them further or, where they had become bound
to organic matter, let them sink to their beds as sediment. Even in the
Ukraine, close to the power station, Soviet engineers say they did not have
to interrupt water supplies to Kiev, the republic鈥檚 capital. This apparent
lack of contamination has produced two sharply conflicting conclusions.
The nuclear lobby emphasises the extreme unlikeliness of another Chernobyl
and the insignificant effect of fallout on water supplies even if there
were. Environmentalists say that it is wiser to take precautions and that
the influence of radioactivity on water supplies should not be dismissed
so lightly.
The National Nuclear Corporation, a subsidiary of GEC, Britain鈥檚 largest
electrical engineering company, designs and builds civil and military nuclear
reactors, mainly in Britain. According to Derek Smith, its director of engineering,
the probability of an uncontrolled release of radioactivity from a reactor
is about once in a million years; even then, he says, the discharge would
be small compared with that released from Chernobyl. At that level of risk,
says Miller, 鈥榠t is doubtful whether water suppliers require comprehensive
contingency plans at all鈥�. The statistics, however, do not convince everyone,
he adds. Three incidents in the past 30 years have 鈥榬aised some question
marks鈥�, he says, recalling the accidents at Windscale in 1957, Three Mile
Island in 1979 and Chernobyl in 1986.
Water suppliers should still feel reassured, insists Heinz Hansen, a
scientist in the health physics department of Denmark鈥檚 Riso National Laboratory.
He has been studying water鈥檚 vulnerability to fallout by comparing the contamination
of drinking water in Denmark, which comes predominantly from sources deep
below ground, with that of the rest of the food chain. His analysis is based
on the effects of fallout between 1962 and 1987 from the nuclear-weapon
tests and during 1986 and 1987 following the Chernobyl accident.
In all cases, the levels of contamination were well below the maximum
limits for safe consumption. He found that the two isotopes he studied in
the weapons fallout, strontium-90 and caesium-137, contaminated mostly grain.
Strontium-90 also affected dairy products, fruit and vegetables; caesium-137
affected these foods much less than it did meat and eggs. But the influence
of the radionuclides on water was barely detectable. Hansen found that only
0.1 per cent of the total contamination from strontium-90 in the diet of
an average Dane over the 25 years was due to drinking water; for caesium-137
it was 0.01 per cent.
In the Chernobyl fallout, Hansen discovered that the isotope he studied,
caesium-137, contaminated mostly dairy products and grain; to a lesser extent,
it affected meat, eggs, fruit and vegetables. He found that fish would be
responsible for about 8 per cent of the total contamination in an average
diet over the two years but that drinking water could be blamed for only
0.1 per cent of it. He admits that the sun was shining when the Chernobyl
cloud passed over Denmark: 鈥業t didn鈥檛 rain as it did in Sweden.鈥� Nevertheless,
he concludes, water obtained from ground beneath deep glacial deposits,
as it is in Denmark, 鈥榠s nearly totally protected from any contamination
by nuclear fallout. In a relative sense, this would apply even in the event
of a nuclear war.鈥�
Hansen extended his research to compare the water on the mainland of
Denmark with that on the Faeroes, a group of small islands in the North
Atlantic between Scotland and Iceland. The work showed that Faeroese drinking
water, which comes from surface streams, was responsible for 3 per cent
of the contamination of an average diet. This is about 30 times the influence
of water on the mainland, 鈥榶et still of relatively minor importance鈥�, says
Hansen. He complains that, despite the evidence, the Danish government is
under pressure to 鈥榙o something鈥� to protect water supplies from radioactive
contamination when 鈥榯here鈥檚 no need鈥�. He blames environmentalists, and the
media, for causing undue concern about radioactivity that has led the public
to demand more than is necessary to safeguard water supplies; he says the
environmentalists, not the nuclear industry, should pay for the measures
to reduce risks to levels that he feels are extravagantly low.
Levels of risk associated with the uncontrolled release of radiation
trouble Miller, not because they are too high or too low but because they
are inconsistent with levels of risk demanded for other potential hazards.
The International Commission on Radiological Protection stipulates that
the safe annual dose of radiation averaged over the lifetime of an ordinary
member of the public, as opposed to someone who works in the nuclear industry,
is 1 millisievert. The ICRP limit puts a population of 100 000 people at
risk of developing 116 more cancers than it would naturally expect to suffer.
This, says Miller, is a hundred times as great as the risk deemed acceptable
from chemical carcinogens in drinking water. The World Health Organization
decrees the toughest limits on radioactive contamination, but even these
present 5.8 times the risk of the values that the organisation adopts for
chemicals, he notes. 鈥業n comparison with other risks in life these are small
but it does point to some disparity in approach.鈥�
The confusion over standards and levels of risk concerns David Aspinwall,
a project manager with Yorkshire Water, one of the 10 regional authorities
which collects, treats and supplies water in England and Wales. He describes
the absence of a unified code as a 鈥榶awning gap鈥�. Aspinwall also feels that
the industry does not know enough about the problems and costs involved
in cleaning water that has been contaminated with radioactive particles.
Solubility in water is a subject of major importance, he says: 鈥業t is the
soluble isotopes that prove to be the most difficult to remove by standard
water-treatment processes.鈥�
Unknown pathways
The subject that most concerns environmental scientists is the way the
radionuclides contaminate water in the first place. Nobody fully understands
even how organic contaminants, such as nitrates, migrate in underground
aquifers; but this has not deterred the International Council of Scientific
Unions from establishing a project to examine the biogeochemical pathways
of artificial radionuclides. Work began in June last year under the auspices
of the Scientific Committee on Problems of the Environment, a standing committee
of the ICSU. The SCOPE unit at the University of Essex, led by Frederick
Warner, is coordinating the three-year project. The unit staged a workshop
earlier this year when 32 scientists from 10 countries were able to review
their work in the light of the Chernobyl accident. One of the main conclusions
was that the mathematical models developed to simulate the transport of
radionuclides still fall short of the accuracy needed to predict levels
of contamination with confidence.
As water engineers consider whether to plan for some future radiological
emergency, they might reflect on the constraints that their colleagues in
France face. Agence de Bassin Seine Normandie, the French regional authority
which supplies Paris with its drinking water, recently simulated the effect
on its operations of an accident at the Nogent nuclear power station, which
sits on the banks of the River Seine upstream of the capital. The authority
discovered that there would be few problems: it would have to stop extracting
water from the river for eight days but could make up the shortfall from
alternative supplies.
At the Glasgow conference, delegates criticised the simulation because
they felt it did not assume the most pessimistic scenario. Dominique Leguy,
an engineer with the authority, admitted that the simulation represented
a comparatively modest accident, but that it still depended on a combination
of incidents that is likely to occur only once in a thousand years. He later
added that the water authority has to rely on information for its simulations
from Electricite de France, which runs the nuclear power stations that provide
70 per cent of the electricity generated in the country. EDF gives the authority
an idea of how much radioactive material can escape during an uncontrolled
release and the likely composition of the fallout.
The authority once tried to do without EDF. In 1984, it began to simulate
the consequences of a much worse accident involving the Nogent power station:
the authority assumed that all the radioactive contents of the core escaped.
The results were passed to the government just before Chernobyl; they were
never published. According to Leguy, the government and EDF decided the
scenario was too outlandish.
Further reading: Water Resource Consequences of a Nuclear Event, from
Linda Schabedly, Thomas Telford Publications, 1 Heron Quay, London E14 9XF,
England. The Effect of a Nuclear Attack upon the Water Services of the United
Kingdom, from Engineers for Nuclear Disarmament, 1 Oatlands Park, Linlithgow,
West Lothian EH49 6AS, Scotland. The first SCOPE-RADPATH workshop of Biogeochemical
Pathways of Artificial Radionuclides, from SCOPE unit, Department of Chemistry
and Biological Chemistry, University of Essex, Wivenhoe Park, Colchester
CO4 3SQ, England. Purity of the Water Supply 鈥� A Briefing Document, The
Royal Society, 6 Carlton House Terrace, London SW1Y 5AG, England.
鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
Radionuclides Milk Other Drinking products
foodstuffs* water 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
Isotopes of iodine and strontium, notably iodine-131 and 500
3000 400 strontium-90 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
Isotopes of plutonium and its derivatives, notably plutonium-239 and americium-241
20 80 10 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
All others with a half-life greater than 10 days, notably caesium-134 and
caesium-137 4000 5000 8000 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
*Values for minor foodstuffs (less than 10 kilograms eaten per year) are
10 times those for 鈥極ther foodstuffs鈥� 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
Radionuclides Food for Dairy Other Liquids babies
products foodstuffs under 6 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
Isotopes of strontium, notably strontium-90 75 125
750 125 Isotopes of iodine, 50 500 200
500 notably iodine-131 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
Isotopes of plutonium, and its derivatives, 1 20
80 20 notably plutonium-239 and americium-241 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
half-life greater All others with a than 10 400
1000 1250 1000 days, notably caesium-134 and caesium-137 鈥斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌斺赌�
* * *
Water supplies survive Chernobyl leak
IN DECIDING how far it should go to protect water supplies from the
possibility of radioactive contamination, the water industry has at its
disposal details of how Soviet engineers coped immediately after the Chernobyl
accident, when the priority was to safeguard supplies to Kiev, where nearly
three million people live.
The city depends on three independent sources, two rivers and a network
of aquifers. The engineers decided that one of the rivers risked serious
contamination but, fortunately, its supply could be made up from the other
two sources. They also calculated that if the other river became too contaminated,
the aquifers alone could meet at least half of the city鈥檚 demand. This flexibility,
though, is not typical of most networks that supply water.
Nicholai Tsarik, chief engineer of the water supply and sewerage administration
for Kiev, says that the concentration of radionuclides in the city鈥檚 drinking
water never exceeded permissible limits, which are more stringent than those
of the West. Soviet scientists measured the greatest contamination of the
water in the month following the accident, when the concentration of radionuclides
increased a thousandfold to about 370 becquerels per litre (the becquerel
is a measure of the activity of a radioactive material in terms of the number
of nuclei decaying per second).
This is one-seventh of the maximum level permitted for one month, and
half of the maximum level permitted for a period of three months; over a
year, the average concentration of radionuclides should not exceed 220 becquerels
per litre. Within one year, the concentration of radionuclides in the water
had reduced to almost the same level it was before the accident, according
to Tsarik.
The water authority spent 30 million roubles (about Pounds sterling
30 million) on the emergency. The sum was higher than it needed to be, as
many of the provisions turned out to be unnecessary. When the emergency
began, says Tsarik, the authority had no idea how bad the contamination
would be: 鈥榃e expected worse and it was better to be on the safe side.鈥�
For example, the Soviet engineers introduced special chemical filters to
decontaminate the waste water and sewage. They used activated carbon to
remove isotopes of iodine and zeolites to remove those of strontium and
caesium: both catalysts were good at removing isotopes of ruthenium.
A less pleasant surprise was the state of the sludge left over at the
end of the treatment of the waste: it featured a number of peculiarities,
recalls Tsarik. Barely one month after the accident, there were many filamentous
organisms and large amoebae; other microorganisms were deformed and scientists
found that more of them had beating hair-like protrusions, or cilia. It
was eight months before the composition of the sludge returned to normal.