The container, which was transported from Port Kembla in Wollongong, south of Sydney, will be stored at ANSTO until a National Radioactive Waste Management Facility is operational.

ANSTO's group executive for nuclear operations and nuclear medicine, Pamela Naidoo-Ameglio, said as part of international treaties, countries are required to take responsibility for the disposal of any nuclear waste they produce.

Ms Naidoo-Ameglio was tight-lipped about what might happen if the waste were to get into the environment.

"There is no credible risk of that happening," she told the media.

On Saturday, bystanders looked on as a nuclear waste ship docked in Port Kembla, carrying reprocessed radioactive waste.

The bright blue ship was an unusual sight in the port as full scale police operation was carried out to make sure it was safely docked.

Police jet skis, helicopter and boats accompanied the ship into the Port. Police officers lined the port banks.

Roads were closed on Saturday night and into the early hours of Sunday morning.

The waste was unloaded and transported during a police operation overnight to the Australian Nuclear Science and Technology Organisation (ANSTO)'s interim waste storage facility in Lucas Heights.

The waste - encased in molten glass, canisters and steel casks - left the United Kingdom on January 20 on a specialist nuclear vessel, bound for Port Kembla.

A shipment of the waste, which stems from Australia's production of nuclear medicine and other products, docked at the port about 11.30am on Saturday.

There was a large land, air and sea police presence at the port including PolAIr, maritime police officers on jet ski and in large and inflatable vessels, as well as officers on the ground, ensuring the safe entry of the ship.

A small crowd of people gathered to watch the ship dock, with some fisherman surprised at police presence.

Live Traffic reported the police operation saw major roads closed between Port Kembla and Lucas Heights for an "oversize vehicle movement".

Closures were in place on the northbound lanes of the M1 Princes Motorway between West Wollongong and Waterfall, up Mount Ousley from 11:30pm and 4am.

Southbound traffic on the M1 was unaffected.

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Motorists were diverted northbound along Memorial Drive through to Bulli Pass, then Princes Highway to Waterfall.

Heathcote Road from Heathcote to Lucas Heights, and New Illawarra Road between Lucas Heights and Menai were closed between 1am and 4am on Sunday.

ANSTO's group executive of nuclear operations and nuclear medicine, Pamela Naidoo-Ameglio this week said significant expertise would be involved in the transportation of the waste.

"The transport and storage cask involved is so well shielded that you could stand near it for 25 hours in order to get the same radiation dose as a 9-hour flight to Singapore," Ms Naidoo-Ameglio said.

"It is a feat of engineering that is made from forged steel, and could withstand a drop of 9 metres, temperatures of 800 degrees Celsius or even a jet plane strike."

About 85 per cent of the nuclear waste produced at ANSTO stems from medicine production.

Australia does not have the ability to reprocess spent fuel rods from nuclear operations, so they are sent to facilities overseas where any uranium is stripped and recycled, and the remaining waste is processed.

"Australia does not shy away from our responsibility to safely deal with the by-products that enable the significant benefits from our nuclear program," Ms Naidoo-Ameglio said.

Following treatment and reprocessing in the United Kingdom, the material will be temporarily held at ANSTO's Lucas Heights campus until a National Radioactive Waste Management Facility is built.

"International best practice is that radioactive waste should be stored in a single facility, and we welcome the Federal Government's recent strong steps to site and build that facility," Ms Naidoo-Ameglio said.

ANSTO's last repatriation effort in 2015 saw the waste safely brought into Port Kembla and transported to Lucas Heights.