Andrei Sakharov's study group at FIAN in 1948 came up with a second concept which was adding a shell of natural, unenriched uranium around the deuterium would increase the deuterium concentration at the uranium-deuterium boundary and the overall yield of the device, because the natural uranium would capture neutrons and itself fission as part of the thermonuclear reaction.
Kelompok penelitian Andrei Sakharov di FIAN pada 1948 mendapatkan konsep kedua yang mana menambahkan satu kulit uranium tak kaya alami di sekitar deuterium akan meningkatkan konsentrasi deuterium di perbatasan uranium-deuterium dan hasil keseluruhan alat, karena uranium alami akan menangkap neutron and itself fission as part of the thermonuclear reaction.