A chain reaction is a sequence of reactions where a reactive product or by- product causes additional reactions to take place. In a chain reaction, positive Chemical chain reactions · Detailed example: the · Nuclear chain reactions. chain reaction: in chemistry and physics, process yielding products that initiate further processes of the same kind, a self-sustaining sequence. Define chain reaction: a series of events in which each event causes the next one: a series of events caused by one — chain reaction in a sentence. WORD OF THE DAY. The process can also be used to detect radiation that initiates the process, as the passage of a single particles can amplified to large discharges. More fell on top of her, causing a chain reaction that toppled hundreds. If each neutron releases two more neutrons, then the number of fissions doubles each generation. Lawrence Berkeley National Laboratory: See chain reaction defined for English-language learners See chain reaction defined for kids. How a Group of Cambridge Scientists Won the International Race to Split the Atom by Brian Cathcart Related Sites Moments of Discovery: More about chain reaction 4 References found in Britannica Articles. Fill your plate with these surprising food words. Most chemical chain reactions have very reactive intermediates called free radicals. An avalanche breakdown process can happen in semiconductors, which in some ways conduct electricity analogously to a mildly ionized gas. Look up chain reaction in Wiktionary, the free dictionary.