Purification ritual?
Also found: a CD player playing the song "Wash Like an Egyptian"
A washing machine would be a close stand in for a nuke in size and weight.
Not having a stand in could invalidate the test, because the person/agent might sneak out of the cargo box in port and get away via a method or route that would be impossible for an agent shlepping a 150 pound bulky washing machine (or nuke).