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Extensive pilot plant studies of the continuous, mercury-catalyzed nitric acid dissolution of uranium-aluminum alloy materials similar to possible reactor fuel elements were carried out. Marked dfierences were observed in the dissolution rates of cast and wrought alloys. Optimum feed-acid concentrations varied with the type of alloy. At constant acid feed conditions dissolving rates vaned approximately with the cube root of catalyst concentration up to a limiting concentration. The metal dissolving rate was proportional to the 0.8 power of the nitric acid feed rate. A general empirical correlation was developed.Nuclear react.or fucls arc periodically processed to sep:ir:ite the fissiotia hlc material froni :illoying elcnients and froni fission pmduct.a \vliicli may "poison" t.lie retictor if they :ire not removed. Many reactors use uraniiitii-:ilumiiiuni-allo~ fuel elcnients of various compositions and shapes, the spent fuels Iking processcd hy batchwise mcrcury-rata1yzec.l tlissolution in nitric acid follo\veil by separation cJf uranium froni aluminum ant1 fisaiuti products by solvent. extniction. I t w i s anticipated that operating simplifications could he achieved by continuoits, as opposed to l)atch, dissolution. Consequently, estensive pilot plant studies of thc continuous dissolution of uraniumalumiiiuni alloys containing up to about 10 wt. yc uranium wcrc undertaken. Data atid eorrel:it.ions arc given for the portion of these investigations pertaining to the important proccss re1:itionships in contiiiuoua dissolution.OFF GAS NO..NO. METAL FEED R Kg TEST EQUIPMENT AND MATERIALSTlir colitiiiunus tliasolver uacd in the experiinerit:il work w i g a td1 %in. I.D. type-3.17 stninlws stcd pipe with :i rooliiig scctioii :it. ttic top. This ovc*rhend cooliiig sert.ion and a down-draft. condriistrr of standard design w r e used to vondenw the steani in t.he o 8 -g :~~ riairig from ttic dissolver solution. The ucid fcwl wris cont-ixiuourly stnun he:itcd 1.0 near-hiiliiiK tempc.ratuwa: t.hc product w i s w t c r cooled and tlicii (sollwted in :I st:iililew steel drum pl:ic.cd on s platform si-alc!. The. : i d fced rntc W:LS controlled with :L rotahctcr rind metinired I)y liquid-levc4 readings on the frctl t:riik. Inet.runientntion for measuring the ked and product spcc?itic grnvitirs arid tenilrrst.urcs 3t variou9 locat.ions was uvailablc.The reavtor fuel materid t.o he dissolved was simul:itcd by usirig cylintiric*:il ~U K S ubout 1% in. in dinmekr rind 8 in. long. AltlrougIi riot rcprrwnttrtive of M.T.R.-type furl plates. in tlint the surface-to-volume ratio of such h r s is much lower th:rn that of pl:rtcs, this forni of mntcrisl \\'as H convenient. arid rconomical choice!. Extruded 2s alumirium-bar Rtoek tirid cnsl a i d extruded urariium-uluminun~-alloq. slugs sere ueed in thcs experimental work. The slugs wcre loaded periodically through : i pair of gate vulves loc:rtecl at the t.op of the disBoIver. GENERAL CONCEPTSA kclienxitic c1i:igr:im of the continuous dissolver and t.he iriiportant ausiliary equipment i...