The device in your image is most likely a Southern Scientific Pedestrian Radiation Portal Monitor. I'm only unsure of the bottom, darker protruding part, the rest looks exactly like the only image the producer released up to the position of the screws (or whatever the dark spots are).
The machine is used to detect traces of gamma and neutron radiation, which may be a result of nuclear weapons.
It's a bit better to see the device installed in this image.
The devices have been in use for quite a time. There even haven been several papers published such as this one in the medical journal The Lancet about setting those devices off after certain medical tests.