The large-scale training demonstration is taking place at Brackenbury Sports Centre in Felixstowe and will run from 9am until 5pm on Tuesday.
It will bring together emergency services and partner organisations to test how they would respond to a radiological incident, including the operation of decontamination facilities.
Locals are being urged not to be alarmed by the activity, with organisers stressing that the exercise is only a training demonstration and not a real emergency.
No radioactive materials will be used, there is no risk to the public and no action is required.
It will take place at Brackenbury Sports Centre (Image: Archant)
People in the area may notice emergency service vehicles, partner agency personnel, temporary structures and staff wearing protective clothing as part of the exercise.
Temporary traffic management measures are also in place.
Quintons Lane has been closed at its junction with High Road East, while temporary traffic signals are operating outside the sports centre.
The cycle lane on High Road East has been suspended, with pedestrians directed by signage and cyclists asked to dismount while passing through the area.
The exercise forms part of regular training coordinated by the Suffolk Resilience Forum to ensure agencies are prepared to work together effectively should a real radiological incident ever occur.