Science Energy Nuclear Waste

Imagine a thin sheet made of a beta-emitter, and a thin sheet of copper, with a thin, wide carbon mesh in between as an insulator. put another carbon mesh on top of this "sandwich" and roll it up. It would look like a carbon-mesh swiss roll, but it would be basically a battery that would be as long-lasting and powervul as the half-life and energy-level of your beta-emitter. Nickel-63 has a half-life of 100 years, but it has a maximum energy level of only 0.067 Mev. That's not going to do at all. Doing some digging, I found that the two best beta-emitter sources would be either Strontium-90 with a half-life of 29 years and an energy level of 0.546 Mev, or Technetium-99 with a half-life of 212, 000 years and an energy level of 0.292 Mev. Of course, studying uses of these sources led me to stumble onto Paul Brown's work, so I knew someone else had a similar notion. He used Strontium-90 which produced MORE than enough energy, but its half-life would be within most anyone's lifetime. Using Technetium-99, a battery could be made, that if as efficient as Paul Brown's battery, would produce perhaps 2/3 the power, but would practically never run out. Direct conversion of beta radiation to electricity is possible, as proven my the Cornell students, so why not harness it? Cliff notes: instead of a conventional sandwich, try a "wrap", and focus on beta particle