Thorium

By A nonymous M IT S tudent # 3

S i nce t h e beg i n ni ng of t he nuc l e ar a ge, t he r e have been pr om i se s of am azi ng t ech no l ogy l i ke nuc l ear ca r s a nd ef f ect i ve l y un l i m i t ed bat t e r i es. A s t i m e w ent on, none of t hese r e al l y c am e t o f r ui t i o n, an d t he r um or s di ed of f f o r t he m ost par t . H ow eve r , w i t h an ar t i cl e abo ut a nuc l ear ca r pub l i sh ed as r ece nt l y as l a t e 201 3, a ce r t a i n A sg a r d i an n u cl ea r f uel h asn ’ t r ece i ve d t he sa m e t r eat m ent . T ho r i um has l ong been p r a i s ed as a m i r acl e f u el by i t s pr opone nt s, an d has a h i st o r y of m i si nf or m at i on an d su ppos ed co nsp i r acy su r r ou nd i ng i t . T ho ugh i t i s ce r t a i n l y a pow er f ul so ur c e of en er gy, and q ui t e possi b l y t he n ex t st ep i n t he r ea l m of nucl ea r ener gy, T ho r i um i s not t he per f ec t f ue l i t i s m ade out t o be.

S o w hat does t hor i um hav e go i ng f o r i t ? P r i m ar i l y, i t ’ s a va l i d n ucl ear f ue l , w e l l su i t e d f or a gr oup of r eac t or s kn ow n as m ol t e n sa l t r eact or s. T hor i um o ccu r s a l m o st ent i r e l y as t he 232 i s ot ope, w hi ch w hen i n neu t r on f l ux abso r bs a neu t r on, beco m i ng T h233, w hi c h deca ys i nt o P a233 and t hen U 2 33, a f i ss i l e i so t o pe of U r an i um . B e ca use of t h i s, T hor i um i s co ns i de r ed a “ f er t i l e” f u el . (1 ) T h i s U 2 33 ca n al so be ex t r act ed and use d as f u el ur an i um r eact or s, w hi c h c an ex pand t he l i f e t i m e of ur an i um f uel r es e r v es. O n t op of t h i s, ano t her benef i t of t he T ho r i um f uel cyc l e i s i t s w ast e pr of i l e - T ho r i um w ast e i s m uch sh or t er l i ve d t han U r a n i um w as t e - t hou gh T hor i um pr oduce s h i g her - r ad i at i on w ast e at f i r st , i t p r oduce s f ar f ew er t r ansu r an i c el em ent s, m aki ng l ong t er m wa st e st or age m uch sa f er . ( 2)

G ener a l l y, t he l eg i t i m at e benef i t s en d t he r e, b ut t her e ar e a t on of m i sco nce pt i ons about T ho r i um t hat l ea d peop l e t o t out i t as a p er f ect f ue l so u r c e . On e su ch m i sco nce pt i on has t o do w i t h U r an i um su ppl y vs T h or i um . I t i s of t en t out ed t ha t t her e i s f a r m or e T hor i um ava i l ab l e t o us t han ur an i um , but t hat i sn ’ t e nt i r e l y t r ue.

T hor i um i s ce r t a i n l y m or e c om m on i n E ar t h’ s cr ust t han U r an i um , about t h r ee t i m es as co m m on, but w hat ’ s of t en f or g ot t en i s h ow m u ch U r an i um i s i n se aw at er - a st agg er i ng

4. 5 b i l l i on t ons i s t heo r et i ca l l y obt ai nab l e, 100 00 t i m es as m uch as t her e i s T h or i um . O f co ur se , co m par ed t o m i n i ng, s eaw at er ex t r act i on i s n’ t co m m er ci al l y v i ab l e at t h e m o m ent , but t he co nce pt has been p r ove n an d t h e co st w ill li ke l y f a l l o nce a d em and e x i st s. ( 3) H ow eve r , t hi s ha l f - t r ut h of abu ndanc e i sn ’ t t he t h i ng m ost of t en pr a i se d, but r at her t he f ac t t hat T ho r i um i sn ’ t ca pab l e of nu cl ea r w eapon pr o l i f er at i o n. E x ce pt , of co ur se , t h at i t i s. T he t h ought t hat t h e T h or i um f ue l cyc l e ca n’ t be use d t o m ak e nucl e ar w eapons co m es f r o m t he f act t hat n o pl ut on i u m i so t opes ar e p r oduc ed, w hi ch i s co r r ec t , but i t i gno r es t he f act t h at U - 23 3, w hi ch i s t h e di r ec t dec ay pr o duct of P a - 233, w hi c h ca n be ch em i ca l l y se par a t ed du r i ng o per at i o n, i s a gr eat m at er i al f or m aki ng nuc l ear w eapons. I n a r e por t f r om t he H anf or d s i t e pu bl i sh e d 1966 , i t i s ex pr ess ed t hat U - 2 33 i s “ hi gh l y sa t i sf act or y as a w eapons m at er i a l ” an d i t i s eve n st a t ed t h at i f U - 2 33 w eapons w er e engi n eer e d f i r st , t her e w oul d l i ke l y hav e been no i n t er est i n sw i t c h i ng t o p l ut on i um - base d w eapons. ( 4)

A nd, of co ur s e, m any st r ong pr opone nt s don’ t t end t o m ent i on t he n egat i v es of T hor i um f uel . O ne of t hes e co ns i s t i ed ve r y t i ght l y w i t h so m et hi ng of t en co n si der e d an

ups i d e. T he s ho r t ha l f - l i f e of T hor i um w as t e c or r es po nds w i t h a h i gh r ad i oac t i v i t y e ar l y on, m ak i ng t he w as t e v er y dange r ous a t f i r s t . ( 2) B ey ond t h i s , t he r e a r e s ev e r a l engi neer i ng c ha l l en ges s t an d i ng i n t he w ay of T hor i um . A m ong t hes e c ha l l enges i s T hor i um ’ s hi gh m el t i ng p oi nt , w hi c h c an m ak e t he r aw f ue l d i f f i c u l t t o w or k w i t h. A not he r hur d l e i s m or e s pec i f i c t o M S R ’ s , w hi c h i s t hat s al t s of t en v er y c o r r os i v e, and at h i gh w or k i ng t em per at ur es t hey t e nd t o b e ev en m or e s o. R e al l y t houg h, t hes e c ha l l eng es j us t c o m e do w n t o t i m e and m oney , w hi c h s um s i t up p r et t y n i c e l y - f i gu r i ng out T ho r i um w i l l be ex pens i v e. ( 5)

S o, w hen y ou r ea l l y l ook i nt o i t , T hor i um i s n’ t ev er y t h i ng i t ’ s c r ac k ed up t o be . It’ s got s om e def i n i t e benef i t s , and m ay be w or t h get t i ng f i gu r ed o ut , but i t ’ s no m i r ac l e f u e l , and s hou l d n’ t be t al k ed abo ut as i f i t w er e. D o i ng s o s pr eads m i s c onc ept i o ns and c an l ead t o c r ac k pot c o ns p i r ac y t heor i es , w hi c h i s bad f or a l l of us .

T ec hn i c a l N ot e

1) T hor i um i s ac t u al l y f er t i l e, not f i s s i l e - i t t ec hn i c al l y i s n ot t he pr i m ar y ener gy so u r ce i n t he r e ac t or . T r ans m ut at i on t r a i ns : Th - 232 + n - > T h - 233 - > Pa - 23 3 - > U - 233 [4 ]

2) T hor i um w as t e i s hi gh l y r a di oac t i v e at f i r s t , b u t i n t he l on g t er m i s m uc h s af er t han U r an i um w as t e [ 4]

3) T hor i um i s abo ut t hr ee t i m es as abundant as ur an i um i n E ar t h’ s c r us t , b ut U r an i um i s near l y 1 0000 t i m es as abunda nt i n oc eans . [ 1] T he m os t c o m m on s our c e of T ho r i um i n t he c r us t i s m onz oni t e [ 2 ] U r an i um i n oc ean’ s i s not c ur r ent l y c om m er c i al l y v i ab l e, but t h e c onc ep t has been pr ov e n. [ 5 ]

4) T hor i um pr oduc t s a r e s u i t a bl e f or nuc l ea r w eapons . T h e r e as on t h i s pat h w as n’ t t ak en i s s i m pl y bec aus e pl ut on i um w as f ound and dev e l o ped f i r s t . [ 3]

5) T hor i um has a f a i r l y h i g h m el t i n g po i nt [ 1] , an d t he f ue l s a l t s us ed i n m ol t en s a l t r eac t or s hav e c o r r os i o n pr o b l em s t hat pos e e ngi n eer i n g c ha l l eng es . [ 6]

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[5 ] ht t ps : / / w w w . p nnl . gov / n ew s / r el e as e . as px ?i d= 45 14

[6 ] h t t p : / / w w w . v t t . f i / i nf / pdf / w o r k i ng pa pe r s / 20 08 / W 90 . pdf ( F 22 i s s t a t e d ge ner al l y , b ut i t i s di s c us s ed t hr ou gh out t h e pa per )

M I T O penCour s e W ar e ht t ps : / / oc w . m it . edu /

22. 011 N uc l e ar E ng i ne er i ng: S c i enc e, S y s t em s and S oc i et y

S pr i ng 20 20

F or i n f or m at i on about c it i ng t hes e m a t er i a l s or our T er m s o f Us e, v i s it : h ttp s ://o c w . m i t .e du/ t er m s .