"These devices are an important addition in the fight against the spread of weapons of mass destruction," said spokesman Noel Colpin.
"Container transport is an easy target for terrorism. One hundred million containers travel around the world each year, so this is a global problem. But with this initiative, we can attack the dangers," he said.
Shipping is used to move about 75 percent of European Union exports and imports, in terms of volume, or around 45 percent in terms of value.
A further 40 of the radiation detection devices are due to be put into service at the port -- the second biggest in Europe and fourth biggest world-wide -- by July next year.
The US-designed system will automatically scan cargo containers on shore.
The costs of the equipment, the training of staff and maintenance of the machines for three years -- estimated at 40 million dollars (31.8 million euros) -- are being met by the United States.
Belgium will pay for the extra 100 or so staff needed and some tax costs, the spokesman said, adding that the machines would not slow the port's operations down.
Similar devices have been or are being installed in the Netherlands, Britain, Canada, Greece, Spain and Singapore, but the project at Antwerp is the biggest US undertaking so far outside the United States.

Copyright AFP (Agence France-Presse), 2006