Do NOT ever take a magnetron apart. They contain beryllium oxide. This stuff is almost as toxic as plutonium. The magnetron is not as tough as they say. If the output cavity is damaged, the whole thing goes to the landfill.
As long as you don't muck around with the ceramic, you're fine. I doubt the toxicity is as high as plutonium.
Plutonium is what killed my father. Beryllium is what damaged my sinus. 2 micrograms per cubic meter is OSHA limit. The Air Force didn't give a flying fuck about either of us.