On the other hand, a prio3'i criteria have been reported recently (Huang and Varma 1981a) applying the fast pseudofirst-order reacnon model (model If) in a nonadiabatic gas-liquid CSTR to provide necessary and sufficient conditions among physico-chemical parameters which assure unique and multiple steady states, and also the asymptotic stability of the steady states. It is believed that these a priori criteria can be derived only by assuming the pseudo-first-order reaction in the "fast" reaction regime (i. e . , the fast pseudo-first-order reaction model). Therefore, the use of' the fast pseudo-first-order reaction model is justifiable not only because of the fair agreement between the multiplicity regions predicted by this model and the second-order reaction model, but also because of its capability to lead to a priori criteria, as shown by the analyticity of the uniqueness and multiplicity regions presented in this work.Thus, it is recommended that the fast pseudo-first-order reaction model (model If) be always applied first to give an idea of the multiplicity regions of second-order reactions; if specific operational conditions are close to regions of multiplicity predicted by this model, then a fine tuning can be done to identify the possibility precisely by using the pseudo-first-order reaction model (model 1) and the full second-order reaction model (model 2)-in that order. Although both models 1 and 2 use trial-and-error, the computational effort is significantly lower for model 1.
DISCLAIMERPortions of this document may be illegible in electronic image products. Images are produced from the best available original document. NOTICEThis r e p o r t was prepared a s a n account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontract o r s , o r their employees, makes any warranty, express o r implied, o r assumes any legal liability o r responsibility for the accuracy, completeness o r usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately-owned rights. A c e n t r i f u g a l c o n t a c t o r of novel d e s i g n h a s been developed f o r t h e s o l v e n t e x t r a c t i o n p r o c e s s i n g of n u c l e a r f u e l s . The n o v e l a s p e c t i s t h a t t h e aqueous and o r g a n i c s o l u t i o n s are f e d d i r e c t l y i n t o t h e annulus between t h e hollow 4-in.-dia r o t o r and t h e c a s i n g and are mixed by s k i n f r i c t i o n as t h e y flow downward. This d e s i g n e l i m i n a t e s t h e mixing chamber, mixing p a d d l e , and i n j e c t i o n n o z z l e employed i n t h e c e n t r i f u g a l c o n t a c t o r d e s i g n developed a t t h e A E C ' s Savannah River (SR) P l a n t . High throughp u t i s achieved by t h e h i g h length-to-diameter (L/D) r a t i o combined w i t h high o p e r a t i n g speed ( t o 3500 rpm).S e p a r a t i n g c a p a c i t i e s w i t h s y n t h e t i c Purex-type s o l u t i o n s [ i . e . , 0.5M n i t r i c a c i d and 30% t r i b u t y l phosphate (TBP) i n n -d o d e c a n e d i l u e n t ] ranged from about 5 gpm a t 2000 rpm t o about 15 gpm a t 3500 rpm. E s s e n t i a l l y 100% s t a g e e f f i c i e n c y w a s demonstrated i n e x t r a c t i o n and s t r i p p i n g tests w i t h uranium as t h e s o l u t e . Mechanical performance w a s very good througho u t t h e tests.
Annular c e n t r i f u g a l c o n t a c t o r s s u i t a b l e f o r l a b o r a t o r y use i n s o l v e n t e x t r a c t i o n work have been designed and t e s t e d f o r b o t h h y d r a u l i c performance and m a s s -t r a n s f e r e f f i c i e n c y . The 2-cm c o n t a c t o r s have nominal flow r a t e s of 80 mL/min and m a s s -t r a n s f e r e f f i c i e n c i e s of a t l e a s t 85% a s measured by t h e e x t r a c t i o n of uranium. These c o n t a c t o r s work w e l l f o r organicto-aqueous (O/A) flow r a t i o s g r e a t e r than 0.8. M u l t i s t a g e u n i t s a l l o w proposed flow s h e e t s t o be t e s t e d on a c o n t i n u o u s b a s i s i n t h e l a b o r a t o r y .Scale-up t o l a r g e r p l a n t -s i z e u n i t s i s s t r a i g h tforward.
Solvent extraction IFuelreprocessinglCentrifugal contactors! Ruthenium jZirconiumThe contactor was also tested for application to the Civex and Thorex processes. SummaryA miniature short-residence-time centrifugal solvent extraction contactor and an eight-stage laboratory minibank of centrifugal contactors were used for testing the possibility of utilizing kinetic effects for improving the Separation of uranium from ruthenium and zirconium in the Purex process. Results of these tests showed that a small improvement found in ruthenium and zirconium decontamination in single-stage solvent extraction tests was lost in the multistage extraction tests -in fact, the extent of Saturation of the solvent by uranium, rather than the stage residence time, controlled the extent of ruthenium and zirconium extraction. In applying the centrifugal contactor to the Purex process, the primary advantages would be less radiolytic damage to the solvent, high throughput, reduced solvent inventory, and rapid attainment of steady-state operating conditions. The multistage mini contactor was also tested to determine the suitability of short-residence-time contactors for use with the Civex and Thorex processes and was found to be compatible with the requirements of these processes.
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