How much sunlight will degrade the Super Takumar 50mm f/1.4 lens color?

I’ve heard that the radioactivness of the Takumar lenses can be degraded by UV light, is there a specific amount of exposure to the sun that I would have to be worried about in a single day or over a week or so?

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u/R-Cursedcomentes — 22 days ago

Bought a Pentax H1a for $15 USD at a flee market!

It came with a Super-Takamur 50mm f/1.4 lens which contains radioactive Thorium which is neat. Doing some work because the mirror sticks up often but not always, otherwise looks very good! Also got a 8mm Canon Cine Canonet 8 for $2usd and works perfectly as far as I can see, just need double 8 film and a battery for the built in light meter!

u/R-Cursedcomentes — 22 days ago