( It ( ( ( decays ( via ( ( ( alpha and ) beta ) emission ) ) ) ( through ( ( a series ) ( of ( ( ( short-lived progeny ) ( , ( ( ( ( 218 Po ) , ) 214 ) Pb ) ) ) ( , ( ( ( ( 214 Bi ) , ) 214 ) ( Po ( to ( ( a ( ( moderately long-lived ) ( ( -LRB- ( ( 21 years ) -RRB- ) ) isotope ) ) ) ( of lead ) ) ) ) ) ) ) ) ) ) ) ; ) )
(ROOT (S (NP (PRP It)) (VP (VBZ decays) (PP (IN via) (NP (ADJP (NN alpha) (CC and) (NN beta)) (NN emission))) (PP (IN through) (NP (NP (DT a) (NN series)) (PP (IN of) (NP (NP (NP (JJ short-lived) (NN progeny)) (PRN (, ,) (NP (CD 218)) (ADJP (JJ Po)) (, ,) (NP (CD 214)) (ADJP (JJ Pb)))) (PRN (, ,) (NP (CD 214)) (ADJP (JJ Bi)) (, ,) (NP (CD 214)) (ADJP (JJ Po) (PP (TO to) (NP (NP (DT a) (ADJP (RB moderately) (JJ long-lived)) (PRN (-LRB- -LRB-) (NP (CD 21) (NNS years)) (-RRB- -RRB-)) (NN isotope)) (PP (IN of) (NP (NN lead)))))))))))) (: ;)))
It decays via alpha and beta emission through a series of short-lived progeny, 218 Po, 214 Pb, 214 Bi, 214 Po to a moderately long-lived (21 years) isotope of lead;
(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)))))) (. .)))