Opened by the Prime Minister in 2007, OPAL is one of a small number of reactors with the capacity to produce commercial quantities of radioisotopes. This capacity, combined with the open pool design, the use of low enriched uranium fuel and the wide range of applications, places OPAL amongst the best research reactors in the world.
While OPAL is the centrepiece of ANSTO's research facilities, the suite of neutron beam instruments housed next to the reactor building and operated by ANSTO’s Centre for Neutron Scattering represent a significant addition to ANSTO's research capabilities.
The role of research reactors
OPAL is one of a number of similar production facilities around the world, including the Safari-1 reactor in South Africa and the HFR reactor at Petten in the Netherlands .
These reactors play a vital role in society by functioning as 'neutron factories', producing radioisotopes for cancer detection and treatment, and neutron beams for fundamental materials research.
OPAL's operation staff cooperate with their international colleagues in sharing information and knowledge both directly through formal collaboration agreements and via various international organisations and forums.
OPAL user groups
OPAL is used by members of the scientific, medical, environmental and industrial communities, as well as Australian Universities.
While OPAL is extremely versatile, and the uses of neutron science are virtually unlimited, OPAL's main uses are:
- Irradiation of target materials to produce radioisotopes for medical and industrial applications
- Research in the field of materials science using neutron beams and associated instruments
- Analysis of minerals and samples using neutron activation techniques and delayed neutron activation techniques
- Irradiation of silicon ingots (termed Neutron Transmutation Doping or NTD) for use in the manufacture of electronic semiconductor devices.
OPAL typically operates in cycles of 30-35 days followed by a short refuelling outage to remove three spent fuel assemblies and replace them with new fuel assemblies.
During these types of outages, the OPAL team also perform maintenance and undertake a series of inspections and surveillances.
In addition, there are longer scheduled maintenance periods to enable more extensive inspections and refurbishments of the reactor.
ANSTO aims to operate the reactor for 300 days each calendar year.
The heart of the reactor is a compact core of 16 fuel assemblies arranged in a 4x4 array, with five control rods controlling the reactor power and facilitating shutdown. OPAL uses low enriched uranium fuel containing just under 20 per cent uranium-235.
In terms of security and nuclear safeguards, this is a distinct advantage over earlier research reactors, some of which required enrichment levels as high as 95 per cent uranium-235.
OPAL's fuel assemblies (core) are cooled by purified water and are surrounded by a zirconium alloy 'reflector' vessel that contains a special type of water called heavy water. The reflector vessel is positioned at the bottom of a 13-metre-deep pool of light water. The open pool design makes it easy to see and manipulate items inside the reactor pool.
The depth of the water acts as a very effective radiation shield. The heavy water maintains the nuclear reaction in the core by 'reflecting' neutrons back towards the core.