Designed by Dr Homi Bhabha, India's three-stage nuclear programme is built around its large thorium reserves. Stage 1 runs Pressurised Heavy Water Reactors on natural uranium, producing plutonium. Stage 2 uses plutonium in Fast Breeder Reactors to convert thorium into uranium-233. Stage 3 will use uranium-233 to run closed, self-sustaining thorium cycle. India advanced the second stage on April 6.