ydinkehän
Ydinkehän is a term that can refer to a couple of related concepts. In a general sense, it translates to "nuclear chain" or "nuclear reaction" in Finnish. This refers to the process where neutrons released from one nuclear fission cause subsequent fissions in a process that can sustain itself. The key elements for a ydinkehän to occur are fissile material and a sufficient quantity, known as critical mass, along with a moderator to slow down the neutrons.
More specifically, the term ydinkehän is often used in the context of nuclear reactors. Here, a controlled
Conversely, an uncontrolled ydinkehän is the principle behind nuclear weapons. In this scenario, the chain reaction