Complex sentence: Physicist Raja Ramanna played an integral role in the research of nuclear weapons technology; he expanded and supervised the scientific research on nuclear weapons and was the first directing officer of the small team of scientists that supervised and carried out the test of the nuclear device.
Split into simpler sentences: Physicist Raja Ramanna played an integral role in the research of nuclear weapons technology; he expanded and supervised the scientific research on nuclear weapons. He was the first directing officer of the small team of scientists that supervised and carried out test of the nuclear device.