( ( ( 137 Cs ) ( -LRB- ( ( half-life ( 30 years ) ) -RRB- ) ) ) ( ( became ( ( the ( first ( long-lived isotope ) ) ) ( related ( to ( ( nuclear ( fallout intensively ) ) ( studied ( in ( aquatic organisms ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP 137) (NNP Cs)) (PRN (-LRB- -LRB-) (NP (NP (NN half-life)) (NP (CD 30) (NNS years))) (-RRB- -RRB-))) (VP (VBD became) (NP (NP (DT the) (JJ first) (JJ long-lived) (NN isotope)) (VP (VBN related) (PP (TO to) (NP (NP (JJ nuclear) (NN fallout) (NNS intensively)) (VP (VBN studied) (PP (IN in) (NP (JJ aquatic) (NNS organisms))))))))) (. .)))
137 Cs (half-life 30 years) became the first long-lived isotope related to nuclear fallout intensively studied in aquatic organisms.
(ROOT (S (NP (DT The) (JJ long-lived) (NNS isotopes)) (VP (VBP require) (NP (NP (NNS thousands)) (PP (IN of) (NP (NP (NNS years)) (PP (TO to) (NP (NN decay)))))) (PP (TO to) (NP (NP (DT a) (JJ safe) (NN level)) (PP (IN in) (NP (DT a) (JJ nuclear) (NN reactor)))))) (. .)))