More context about the technology at https://en.wikipedia.org/wiki/Betavoltaic_device https://en.wikipedia.org/wiki/Betavoltaic_device which mentions "Betavolta

More context about the technology at https://en.wikipedia.org/wiki/Betavoltaic_device https://en.wikipedia.org/wiki/Betavoltaic_device which mentions "Betavoltaic nuclear batteries can be purchased commercially. Available devices include a 100 μW tritium-powered device weighing 20 grams[12]" linking to a press release at https://newatlas.com/city-labs-nanotritium-betavoltaic-battery/23720/ https://newatlas.com/city-labs-nanotritium-betavoltaic-batte... about a product from https://citylabs.net/ https://citylabs.net/ . That's only 20 years, vs. the 50 from this article. What isotope(s) are they using for 50 years? All I see is "After the decay period, the 63 isotopes turn into a stable isotope of copper", which sounds very odd. Why 63 different isotopes? What decay chain ends up with copper?