ANSTO's Open Pool Australian Lightwater (OPAL) reactor is a state-of-the-art 20 Megawatt reactor that uses low enriched uranium (LEU) fuel to achieve a range of research, scientific, industrial and production goals.
Opened by the Prime Minister in 2007, OPAL is one of a small number of reactors with the capacity for the commercial production of radioisotopes. This capacity, combined with the open pool design, the use of LEU fuel and the wide range of applications, places OPAL among 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 the Bragg Institute represent a significant addition to ANSTO's research capabilities. Former Minister for Industry, Innovation, Science, Research and Tertiary Education, Senator Kim Carr, described ANSTO's contribution to Australian science by saying:
"Having started out as a specialist organisation…at Lucas Heights, ANSTO is now driving innovation in nuclear science and technology right around the country. The Government is very aware of how important this work is."
OPAL is operated and maintained by the Reactor Operations group within the Nuclear Operations division.
The role of research reactors
While virtually every research reactor is unique, OPAL is one of a number of similar production facilities around the world, including the Safari-1 reactor in South Africa, the HFR reactor at Petten in the Netherlands and the NRU reactor at Chalk River in Canada. These reactors play a vital role in society by functioning as 'neutron factories', producing isotopes for several important purposes, including the production of 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, industrial and security 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 Transmission 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 two or three spent fuel elements and replace them with new fuel elements. During these types of outages, OPAL's Reactor Operations team also perform preventative and corrective maintenance.
In addition, there are longer maintenance outages (extended maintenance) to enable more extensive inspections, refurbishment and maintenance. ANSTO aims to operate the reactor for 300 days each calendar year (see schedule).
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 (weapons grade).
OPAL's fuel assemblies (core) are cooled by demineralised light water (ordinary water) and are surrounded by a zirconium alloy 'reflector' vessel that contains 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 ensures effective radiation shielding of staff working above the pool. The heavy water maintains the nuclear reaction in the core by 'reflecting' neutrons back towards the core.
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