( This ( ( ( ( is ( ( the key ) ( to ( ( the operation ) ( of ( a ( nuclear reactor ) ) ) ) ) ) ) , ) ( because ( ( as ( ( this fission ) occurs ) ) ( , ( ( ( large amounts ) ( of ( energy ( in ( ( the form ) ( of heat ) ) ) ) ) ) ( is ( released ( which ( can ( be ( used ( to ( ( create steam ) ( to ( drive ( ( large ( steam turbines ) ) ( which ( ( in turn ) ( drive ( large ( electricity generators ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (NP (NP (DT the) (NN key)) (PP (TO to) (NP (NP (DT the) (NN operation)) (PP (IN of) (NP (DT a) (JJ nuclear) (NN reactor)))))) (, ,) (SBAR (IN because) (S (SBAR (IN as) (S (NP (DT this) (NN fission)) (VP (VBZ occurs)))) (, ,) (NP (NP (JJ large) (NNS amounts)) (PP (IN of) (NP (NP (NN energy)) (PP (IN in) (NP (NP (DT the) (NN form)) (PP (IN of) (NP (NN heat)))))))) (VP (VBZ is) (VP (VBN released) (SBAR (WHNP (WDT which)) (S (VP (MD can) (VP (VB be) (VP (VBN used) (S (VP (TO to) (VP (VB create) (NP (NN steam)) (S (VP (TO to) (VP (VB drive) (NP (NP (JJ large) (NN steam) (NNS turbines)) (SBAR (WHNP (WDT which)) (S (PP (IN in) (NP (NN turn))) (VP (VBP drive) (NP (JJ large) (NN electricity) (NNS generators)))))))))))))))))))))) (. .)))
This is the key to the operation of a nuclear reactor, because as this fission occurs, large amounts of energy in the form of heat is released which can be used to create steam to drive large steam turbines which in turn drive large electricity generators.
(ROOT (S (NP (NP (DT A) (NN turbine)) (VP (VBG using) (NP (NP (NNS tides)) (PP (IN in) (NP (DT the) (NN ocean)))))) (VP (MD can) (VP (VB create) (NP (NN electricity) (NN energy)))) (. .)))