Between 1953 and 1957, the British Government conducted nine nuclear weapon tests in the north of South Australia with the support of the Australian Government. Two nuclear devices were detonated at Emu and seven at Maralinga. Most of the nuclear devices at Maralinga were detonated on 30-metre towers, though others were detonated at higher altitude or at ground level. These nuclear explosions were not the major cause of contamination at Maralinga, as the heat and energy of the fission explosions drew much of the contamination up into the atmosphere.
The major cause of contamination at Maralinga was the minor trials. The minor trials did not involve nuclear explosions. They were developmental experiments designed to investigate the performance of various components of a nuclear device. Almost all involved radioactive materials in conjunction with conventional high explosives. The British Government conducted about two hundred minor trials between 1953 and 1963. Most of the minor trials were "clean", but about twenty minor trials dispersed plutonium contamination onto the surrounding soil.
Plutonium was the major radiological contaminant at Maralinga. It was dispersed into the surrounding area through the detonation of nuclear devices and minor trials.
Plutonium is a hazard to humans inhaled, ingested, or absorbed through breaks in the skin. External exposure to plutonium does not pose a health risk, as the element emits alpha particles which do not pass through unbroken skin.
There were also small amounts of some other radiological contaminants, and uranium fragments. Uranium is not a radiological hazard, but can be toxic to humans if ingested in large enough amounts.
The British Government conducted a series of clean-up operations at Maralinga and Emu between 1963 and 1967. These clean-up operations were based on a series of assumptions now recognised to be inaccurate, and did not rehabilitate the site to the standard later recognised to be necessary for the protection of people and the environment. After the final clean-up operation, which was accepted at the time as adequate by the Australian Government, the British Government was largely released from any future liability.
In 1985, the Royal Commission into British Nuclear Tests in Australia recommended that the British Government should bear all costs for a future rehabilitation of Maralinga. In 1993, representations from the Australian Government and the traditional owners of the Maralinga lands resulted in the British Government making an ex-gratia payment of £20 million to the Australian Government. This amount was accepted as a significant contribution to the cost of the planned rehabilitation project.
In 1985, the Royal Commission into British Nuclear Tests in Australia recommended that the test sites at Maralinga and Emu be remediated to be fit for unrestricted habitation by the traditional owners. To address technical matters arising from the Royal Commission, the Australian Government established the Technical Assessment Group (TAG).
TAG comprised Australian, British and American scientists with expertise in relevant fields. A series of scientific and engineering studies was conducted, which showed that residual plutonium contamination of soil from the minor tests and the consequent risk of inhalation of contaminated dust was the predominant contributor to potential radiation dose at Maralinga. TAG assessed the level at which the risks became unacceptable for traditional owners living a semi-traditional lifestyle, taking social, economic and scientific factors into account
In 1990, the TAG Report presented the Australian Government with a range of costed options for rehabilitating the Maralinga lands. In 1991, the Australian Government, the South Australian Government, and the traditional owners, Maralinga Tjarutja, agreed upon the option later implemented, which permits unrestricted access to all but approximately 120 square km of the site. To make the whole of the site available for unrestricted access,it would have been necessary to remove a much larger area of surface soil. This option was rejected by Maralinga Tjarutja because of the environmental damage it would have caused.
As part of this agreement, the Australian Government reached a compensation settlement with Maralinga Tjarutja, which included training opportunities in the Maralinga Rehabilitation Project and the payment of $13.5 million in settlement of all claims in relation to the nuclear testing.
Rehabilitation at Maralinga consisted of two parts. The first part was removal of surface soil from the more contaminated areas. Over 350,000 cubic metres of contaminated soil and debris was removed from the surface of just over 2 square kilometres. This contaminated soil was then buried in trenches 10-15 metres deep, under a capping of at least 5 metres of clean soil. The second part was treatment of contaminated debris pits, left over from British Government efforts to clean up the site. Eleven pits were treated by in situ vitrification, a process that involved passing an electric current through electrodes in the ground to melt soil and debris and incorporate the material into a vitrified monolith (a glass/ceramic block), thereby immobilising the radiological contaminants.
Marker plinths and signs were erected to mark the location of each burial trench. A revegetation program was conducted in the areas where major earthworks were carried out. Boundary markers discouraging permanent habitation were erected where necessary.
Two atomic explosions and some minor trials were undertaken at Emu in the 1950s, 190 kilometres north-east of Maralinga. The main contamination was plutonium-infused soil near the detonation sites.
Because of the low level of contamination at Emu, no major remedial work was undertaken at the site. Access tracks were removed and a revegetation program was conducted. Boundary markers discouraging permanent habitation were erected approximately 1 km from the detonation sites.
The project maintained an excellent safety record. Strict procedures consistent with best international practice were followed throughout the project to ensure that all works were undertaken safely and that workers were protected from radiological and other hazards.
No worker received a measurable uptake of plutonium during the project.
Maralinga Tjarutja workers were employed on the project - erecting boundary marker signs around areas of restricted access, collecting native seeds for revegetation, and undertaking general hazard reduction works.
Indigenous workers were also employed by some subcontractors on the project to assist with earthworks, camp management and health physics.
The project was completed on time and within budget, for a little under $108 million in 1999 dollars.
ARPANSA inspected and monitored the remediated areas, and issued clearance certificates for the areas rehabilitated due to radiological contamination. Possible radiation doses are well below those anticipated, and the zone of restricted land use is not strictly required. The restriction on permanent occupancy within certain areas (approximately 120 square kilometres at Taranaki) is a purely precautionary measure. The risk has been reduced from 1 in 100 of developing a fatal cancer to less than 1 in 20,000.
Emu was found not to have significant contamination apart from residual radioactivity around the detonation sites and was handed back to Maralinga Tjarutja in 1996.
As well as radiological hazards, various other health and occupational safety hazards have been remediated. This included removal of asbestos, removal of concrete structures, removal of trip and fall hazards in the Maralinga Village area, repair and maintenance on Village infrastructure, roadworks, and removal and burial of vast amounts of uncontaminated general litter around the site.
The 1995 Deed of Agreement between the Australian Government and Maralinga Tjarutja included a commitment by the Australian Government to return the Maralinga site, including Maralinga Village and the airfield, to the South Australian Government for addition to the Maralinga Tjarutja freehold lands.
All parties are now working towards returning Maralinga to its traditional owners.
The Australian Government, the South Australian Government and Maralinga Tjarutja are developing a long-term Maralinga Land and Environment Management Plan. This detailed plan will require periodic radiation and physical monitoring of the site.
The National Archives of Australia 
hold a large and varied collection of documents relating to the conduct of the British nuclear tests in Australia, including at Maralinga and Emu, and on the Royal Commission into British Nuclear Tests in Australia (1984-1985).
Maralinga is not open for visits by the general public.