Before revision: As a DIY project As simple betaphotovoltaic nuclear battery can be constructed from readily-available tritium vials (tritium-filled glass tubes coated with a radioluminescent phosphor) and solar cells.
After revision: A a DIY project As simple betaphotovoltaic nuclear battery can be constructed from readily-available tritium vials (tritium-filled glass tubes coated with a radioluminescent phosphor) and solar cells.