Since 1986 IRI has had to generate 10 per cent of its income from commercial
sources. One of these is the Dutch gemstone trader Van der Zalm, who was
in search of an irradiation facility that could colour topaz.

Topaz, which has the formula (Al2SiO4(F,OH)2) (the fluorine and hydroxyl
groups are interchangeable) occurs in a wide range of colours, from colourless
and yellow through orange and brown to violet and blue. Blue topaz is the
most popular and the most rare. People have known since the end of the 1950s
that colourless and yellow topaz can be turned into various shades of blue
by irradiation. To produce so-called Sky Blue, white topaz is irradiated
with electron beams. IRT of San Diego, is the world leader in electron beam
irradiation of topaz for this purpose.

But to obtain a darker shade of blue, so-called London Blue topaz, the
stone must be irradiated with neutrons – which requires a nuclear reactor.
Researchers still do not know exactly what happens to the gems during neutron
irradiation. They suspect that the fast neutrons make silicon-30 into silicon-31
and that this isotope degrades in turn within two hours into phosphorus-31.
This impurity in the crystal structure creates the blue colour. But there
must be an additional mechanism, because London Blue can also be produced
with intensive gamma radiation from cobalt-60. However, with the cobalt-60
method the gems have to be stored for up to four years to make sure the
radiation has dissipated, compared with between 2 and 12 months for neutron
irradiation.

A few other nuclear research reactors produce London Blue topaz as a
sideline, but the Dutch IRI is optimistic that demand for irradiated gems
will increase, especially in Europe.

The IRI is also looking into the possibilities of irradiating diamonds,
to produce green, brown, yellow, pink or black ones. This would be more
profitable: the institute charges about 1.30 guilders per carat for topaz,
and for diamonds this figure could be as much as 40 guilders per carat.

This year an experiment will investigate whether the contamination can
be kept safely in the hot spots by vitrifying the soil. The experiment will
be carried out by Grontmij, an engineering consultancy firm.

The soil will be vitrified using electricity. Copper electrodes will
be rammed up to 10 metres into the ground. Soil by itself does not conduct
electricity, so graphite conductors will be placed between the electrodes
to heat up the soil. A voltage of 4000 volts will be put between the electrodes.
Within a week or so the temperature of the soil should rise to 2000 Degree
C, making the soil melt into a kind of artificial magma. Organic contaminants
such as dioxin are broken down into harmless substances through oxidation
at temperatures above 1000 Degree C. While the soil is heated up, the gases
that surface are collected and cleaned.

After a week the electrodes, which will cover an area of 25 square metres,
will be pulled out of the soil, which will then be left to cool down for
about a year. During this period a form of glass should develop that is
similar to the natural mineral that develops when lava cools quickly.

This process destroys 99.99 per cent of organic substances. More than
90 per cent of the inorganic material – mainly heavy metals – will be immobilised
in the glass, according to experiments in the US.

The vitrified soil will be left on site, together with the less contaminated
soil. Vitrifying leads to a reduction of volume, which should make the surface
sink by a metre or more – enough to put on clean topsoil. The contaminated
area will eventually be made into a park.

About 200,000 tonnes of soil will be vitrified, out of a total of around
5 million tonnes of contaminated soil. Vitrification is expensive. The whole
operation will cost about Pounds sterling 80 million.

Vitrification was first developed in the US as a technique for immobilising
nuclear waste. A few years ago the idea was adapted in the US for treating
contaminated soil. According to Esther Soczo from the Dutch National Institute
for the Environment, Diemerzeedijk will be the first location in the world
where vitrification will be used outside laboratory conditions.

The traditional solution would be merely to isolate the site with screens
rammed into the soil. This would cost about Pounds sterling 32 million.
Alternatively, the polluted soil could be burnt in a waste incinerator –
but there is too much contaminated soil, and its handling would require
so many safety precautions that the task would be almost impossible.