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European governments are devising a cut-price solution for monitoring
radiation leaks from the ageing reactors of the former communist bloc. Over
the next few months, suppliers of radiation monitoring systems will be asked
to tender for a ‘gamma curtain’ to surround these nuclear power plants.

This move to install a Europe-wide radiation monitoring system marks
a major shift in policy by Western European governments. Following the accident
at Chernobyl in April 1986, the European Community backed the idea of bringing
Eastern Europe’s nuclear power plants up to Western safety standards. A
programme that could cost up to 17 billion Ecu. Some funding for such work
is available from the European Commission’s Technical Assistance to the
Commonwealth of Independent States (TACIS) fund, set up to provide aid
for nuclear safety, distribution and public sector projects in the former
Soviet Union. However, the TACIS budget for nuclear safety amounts only
to 100 million Ecu, which means that the European Community countries would
be footing most of the bill.

The installation of a gamma curtain – a dense net of radiation monitors
strategically placed to pick up radiation leaks from the ageing reactors
– is a much cheaper option, which should cost no more than 26 million Ecu.
Although the gamma curtain does not address the underlying problem of some
reactors being ‘unsafe’ – it will warn Eastern and Western European countries
of a major disaster within minutes.

Initially, the monitoring system will be tested at two nuclear power
plants in Ukraine and Belarus. The aim is to get this pilot system running
by August next year, and if successful, the complete curtain will be installed
over the next five years. Once in place, it will be possible to detect
rises in the level of background gamma radiation. Some radiation is ‘normal’,
for example, in Minsk, the capital of Belarus, between 0.15 and 2 microsieverts
per hour is regularly detected. In Western Europe typical background radiation
levels vary between 0.05 and 0 microsieverts, with the level rising to 0.3
microsieverts in areas with lots of granite.

Several Western European countries, including Britain and Germany, have
already started to install monitoring systems at a local level. Britain
began installing the first phase of its system – called Rimnet (Radioactive
Incident Monitoring Network) – in 1988. Supplied by Siemens-Plessey, this
included 92 gamma dose rate monitors located all over the Britain. The monitors
send hourly readings to a central database collating the monitoring data,
held at the Department of the Environment in London, with a backup database
centre in Poole, Dorset. The second phase of Rimnet, scheduled for completion
later this year includes the addition of a software system capable of predicting
the path of a radiation plume, and showing this path on a computer generated
map. A technical coordination centre has also been set up at a DoE office
in London. Staff at this centre will liaise with other government departments
and disseminate information to the media, if a radiation plume is detected.

A larger system is in operation in Germany. The German IMIS monitoring
system uses more than 2000 sensors, measuring gamma dose rate as well as
alpha and beta radiation. Data from these sensors is sent to a central database
at the German Environment Ministry (BMU) in Bonn, which is available to
58 state offices and four federal government environmental agencies.

The BMU is one of the main supporters of a much wider gamma curtain.
In addition to the German IMIS system, the BMU is already funding pilot
early warning systems in the Czech and Slovak republics, and in Russia –
at a cost of £398 406 each. The Czech and Slovak systems are installed,
with 20 monitors around two nuclear power plants (one in each republic)
and databases in Prague and Bratislava. The Russian pilot systems will monitor
the most critical reactors at Smolensk, Novovoronezh and Kursk. Data will
be sent via satellite to a database in Moscow, and onwards via another satellite
link, to Germany, where it will be input into the IMIS database.

The BMU is also working with the European Commission on the more comprehensive
gamma curtain concept covering the whole of the Commonwealth of Independent
States and Central Europe. Last year, the Commission approved TACIS funding
for a feasibility study of radiation monitoring in Belarus and Ukraine.
Ukraine has five nuclear plants, including the one at Chernobyl. The others
are at Zaporozhye, Khmelnitskiy and Rovno. There are also the Kursk and
Novovoronezh plants just across the border in Russia. Belarus has no nuclear
power plants on its own territory but it is ringed by plants in neighbouring
states.

Local procedures for radiation monitoring do exist, but they rely on
hand-held monitors, which are often up to twenty years old. At 9 am, readings
of temperature, rainfall, wind speed and direction and gamma dose rate count
are relayed to a central computer centre in Minsk or Kiev, usually from
a phone in the local post office, but sometimes by telegraph.

Automatic reaction

With the introduction of the gamma curtain, this manual approach will
be replaced with strategically placed automatic sensors. In Britain, it
is usual to have between 8 and 10 gamma dose rate sensors on the boundary
fence around a nuclear power plant. However, Illya Lukhtariov, a Russian
radiation expert, suggests that for the CIS project there should be between
50 and 60 gamma dose rate sensors placed at varying heights and distances
around the perimeter of each plant.

Lukhtariov points out that radiation plumes which break out from a nuclear
plant in the event of a leak can travel vertically or horizontally. Vertical
plumes can rise quickly – well out of the reach of ground-based sensors
– and travel long distances before they are detected. Some may even rise
to the top of the inversion layer in the atmosphere, and wait there until
rain clouds form before the radiation falls to the ground. In the Chernobyl
accident, two plumes did just that. One travelled almost 200 kilometres
to the town of Gomel in Belarus, before it fell as radioactive rain. Another
travelled all the way to Black Sea, around 800 kilometres away. Horizontal
plumes can be extremely narrow – as little as a few metres across – and
may slip between the sensors.

PA Consulting Group, the British management consultancy that carried
out the preliminary study for the gamma curtain, put forward a scheme based
on Luktariov’s advice. However, the idea of having 60 sensors around each
plant was deemed ‘grandiose’ and impractical so the pilot project will use
fewer sensors, placed in three bands around the reactor. Between five and
eight sensors will be put on the roof of the reactor, while the second band
of some 10 sensors will be 1 kilometre from the plant, and the third band
of between 10 and 20 sensors will be anywhere between 10 and 30 kilometres
away.

Other types of sensors will also be placed in strategic positions near
the reactors. Gamma dose rate sensors only indicate radiation increases
over and above the existing background radiation, they don’t give information
on the ‘type’ of radiation, which can be very useful for identifying the
seriousness of a leak. The presence of iodine-131, for example, would indicate
a serious accident in the reactor core, and civilian authorities would need
to take swift action, such as evacuating the area.

These specialised sensors typically use a dust filter to collect a sample
and measure levels of alpha and beta radiation over a time period of an
hour. If the level exceeds a pre-set limit – 50 millibequerrels per cubic
metre per hour for alpha particles and 100 millibequerrels per cubic metre
per hour for beta – they will raise the alarm. In the gamma curtain such
sensors will be placed on the side of a reactor nearest to a population
centre.

The team from PA is also looking at using nucleid specific sensors,
which can give even more precise information about the radionucleids present
in a radiation sample. Nucleid specific sensors, are an advanced form of
gamma spectrometer, which operate at -196 °C. Until recently these sensors
were limited to laboratory use where liquid nitrogen could be used for cooling.
But EG&G, an electronics firm based in Boston, Massachusetts has developed
an advanced electrical cooling system which makes the sensors more portable.

Information from these sensors can be transferred to the company’s automatic
analysis system, which runs on standard personal computers. This can analyse
100 different nucleids and detect radiation levels of less than 50 millibequerrels
per cubic metre. EG&G’s system is expensive, however, with a price tag
of more than £60 000 per unit. The high cost – compared with an average
of £3000 for a gamma dose rate sensor or even £20 000 for
an alpha/beta or iodine sensor – means it can only have limited use in
the gamma curtain, for example, downwind from a reactor near a town.

Companies will be invited to tender for the pilot system in Ukraine
and Belarus next month. If the system goes well, TACIS will be asked to
approve the 22 million Ecu funding – a relatively small price to pay for
public reassurance and safety.