Some possibilities:
- Not quite depleted uranium mass balance weights
- Instrument faces and needles painted with radioactive radium 'glow in the dark' paint Radium dials - Wikipedia, the free encyclopedia
- Insulation blankets, brake pads, gaskets and even polysulphide (PR1422a) tank sealant pre 1990s could all contain asbestos.
- Mercury switches, or any other mercury containing parts.
Provided the students don't start pulling apart insulation blankets, blowing the dust off panels which have been near them, or wirebrushing brake parts, I would have thought the risks were minimal. Production workers exposed to the same parts day in, day out and the dust or residue from manufacturing processes are the ones likely to be at risk. Removing engines etc, in my opinion, is far more likely to raise dust and creat a hazard than just carrying on as before.