Research reactors

HIFAR reactor, now replaced by OPAL

About 280 research reactors operate round the world. Australia has one, ANSTO's OPAL, which is the only nuclear reactor in the country.

Nuclear research reactors do not generate electricity, are a fraction of the size of power reactors and are often not, as their names implies, used only for research purposes. They tend to be highly versatile, multi-use neutron producers.

They can be used, as in the case at ANSTO, to investigate properties of a wide range of materials, to irradiate silicon ingots for use in very high quality semi-conductors, and to make industrial radioisotopes and many of the radiopharmaceuticals used in nuclear medicine centres throughout Australasia and the near-Asia-Pacific region.

Making neutrons available for research

Neutrons are unrivalled for examining at atomic level both the structure and performance of materials under a wide range of conditions.

In such research, neutrons are directed from a research reactor's core down heavily shielded, precisely constructed beam lines to bombard samples, which can be examined under conditions varying from differing vacuum pressures, and high and low temperature.

These conditions can, for example, mimic a manufacturing process and deliver detailed information on obtaining best performance from components, or ingredients, and the processes in which they are used.

Neutron bombardment is also used to make radioisotopes for industry and medicine.

The most widely used nuclear medicine is technetium-99m. It begins life when a uranium-235 target is irradiated with neutrons produced in a research reactor's core.

Precise exposure makes another element, molybdenum-99, in this target. The molybdenum-99 decays, as all radioactive materials do, to become technetium-99m.

Lower power

Research reactors are small compared to power reactors whose primary function is to produce heat to generate electricity. When applying the measure of the power outputs of reactors, most research types range up to 100 megawatts thermal.

This compares with a typical power reactor's 3000 megawatts thermal. The total power output equivalent of all the world's research reactors is about the same as one power reactor. Research reactors operate at lower temperatures and use far less fuel.

A concerted international move to reducing the risk of nuclear materials proliferation has seen research reactors shifting to the use of lower levels of uranium enrichment in their fuel.

Australian experience

For most of its operating life, ANSTO's recently shut down High Flux Australian Reactor (HIFAR) used uranium-235 enriched to 60 per cent. This was eventually cut to less than 20 per cent, an amount regarded as having no value for illegal uses.

ANSTO's - and Australia's - newest research reactor, OPAL, first went critical, or achieved its first controlled nuclear chain reaction, on 8 December 2006. It became the third research reactor to operate at Lucas Heights and cost $400 million to build including a neutron beam instrument facility.

The first, HIFAR, was officially opened on Australia Day, 26 January 1958.

Built at an initial cost of $2.9 million, it provided the greater part of Australia's nuclear-based needs for just short of 50 years. It was shut down permanently on 30 January 2007.

The very small Moata reactor cost $150,000 and operated for just over 37 years, mainly for materials research. It went critical for the first time on 1 April 1961 and was shut down permanently on 1 May 1998.