OPAL capabilities
ANSTO's neutron guide hall adjacent to
the reactor will eventually house
ten instruments
With its many capabilities, OPAL accommodates a broad range of needs for Australian medical, industrial, scientific and mining communities.
OPAL utilisation facilities are sub-divided into:
- Neutron beam research; and
- Irradiation for radioisotope production, neutron activation analysis and delayed neutron activation analysis of materials, and silicon ingot doping for the semiconductor industry.
Neutron beam research
OPAL is specially designed to sustain neutron scattering related research, with three different sources supplying neutrons of varying energy ranges:
- Cold neutron source (CNS): provides very low energy (low velocity) neutrons with long wavelengths for neutron scattering. Using a CNS allows researchers to study the structure and properties of materials such as plastics, ceramics, magnetic materials, pores in rocks and biological materials at the nanoscale (one billionth of a metre).
- Thermal neutron source: provides medium range energy neutrons in an energy range comparable to room temperatures. Thermal neutrons are used to peer inside metallic objects such as aircraft and engine components and to investigate the atomic and magnetic structure of materials including minerals, pharmaceuticals, cement and superconductors.
- Hot neutron source: although not yet available, there is a further provision for a future option to provide a hot neutron source with temperatures around 10000C. Hot (high velocity) neutrons can be used to study the structure and behaviour of glass and glass-like materials, liquids and the molecular interactions in materials for the energy industry (including hydrogen storage materials).
Cold neutron source
Scientist inspects the guide
positioning in Quokka
In order to slow down neutrons produced in the core, there is a device called the CNS that is installed in the reflector vessel surrounding the reactor core. The CNS uses liquid deuterium (an isotope of hydrogen) as a moderator and operates at very low temperatures (about -2500C). The CNS moderator is cooled by helium vapour circulating through a heat exchanger and in an outer cooling jacket.
With this device, neutrons are 'moderated' to lower energies (i.e. slowed down): the neutrons have around three times less energy than in the thermal guides. The cold neutron source is located as near as practical to the peak in the thermal neutron flux (~50 cm from the core, centre to centre).
Neutron guides
Neutron guides carry the neutrons from the reactor core towards the neutron guide hall instruments, which can be as far as 40 metres away from the core. The neutron beams are used by scientists to conduct neutron research.
At present, OPAL has two thermal and two cold neutron guides extending into the neutron guide hall. There is capacity for further expansion, including potential for a second neutron guide hall on the south side of the reactor building. Neutron super-mirrors in the guides transport, bend and focus the neutron beams. Neutrons are reflected off the surfaces of these mirrors, which are made by sputtering layers of nickel and titanium onto a surface. As neutrons are scarce, the guides are operated under vacuum: there are 10 billion more air molecules than neutrons in a cubic centimetre of a guide.
The neutron guides begin 1.5 metres from the reactor core and continue through beam shutters until the outer perimeter of the reactor. These neutron guides are 50 mm wide and between 50 mm and 300 mm high. The guides are very slightly curved between the reactor face and the exit of the guide bunker, to beyond line-of-site, reducing contaminating radiation.
Irradiation facilities
OPAL has the following irradiation facilities:
- General purpose irradiation facilities
- Bulk irradiation facilities, used for the irradiation of uranium plates to produce Molybdenum-99 and the irradiation of other materials such as Iodine-131
- Large volume irradiation facilities, used for irradiating silicon
- Neutron activation and delayed neutron activation facilities, used for determining the content of samples and the amount of uranium in samples, respectively
The irradiation facilities are contained in various tubes within the reflector vessel that access neutron fluxes of varying wavelengths as required for the material being irradiated and its end purpose. For example, the large volume irradiation facilities used for irradiating silicon are located around the outer part of the reflector vessel (further from the core) because a lower flux is required for transmutation doping.
The irradiation facilities are supported by extensive pre- and post-irradiation handling stations in the reactor service pool, and a number of hot cells that shield personnel from radioactive material. However, no processing of irradiated material takes place within the OPAL facility. Instead, there is a pneumatic shuttle system between OPAL and the radiopharmaceutical processing centre operated by ANSTO Health.