( ( Nuclear ( power reactors ) ) ( ( use ( ( controlled ( nuclear fission ) ) ( in ( a ( chain reaction ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Nuclear) (NN power) (NNS reactors)) (VP (VBP use) (NP (NP (VBN controlled) (JJ nuclear) (NN fission)) (PP (IN in) (NP (DT a) (NN chain) (NN reaction))))) (. .)))
Nuclear power reactors use controlled nuclear fission in a chain reaction.
(ROOT (S (NP (NNP Control) (NNS rods)) (VP (VBP play) (NP (NP (DT an) (JJ important) (NN role)) (PP (IN in) (NP (NP (DT the) (NN modulation)) (PP (IN of) (NP (DT the) (JJ nuclear) (NN chain) (NN reaction))))))) (. .)))