2011) 1( 24المجلد مجلة ابن الھیثم للعلوم الصرفة والتطبیقیة السداسيمن الیورانیوم تراكیز عالیة أستخالص وفصله عن نواتج االنشطار الالعضویة المشعع 2010 نیسان 1 :استلم البحث في 2010أیلول 27: قبل البحث في حمادي صالح الدین جاسم میاء ، كلیة العلوم ، جامعة دیالىقسم الكی الخالصة ( ارـــعن نواتـج االنشط) سداسي التكافؤ(تم في هذا البحث دراسة استخالص تراكیز عالیة من الیورانیوم المشعع تضت ، وقد أق )منظومات الخلط والفصل( باستخدام تقنیة الجریان المتعاكس متعدد المراحل )باعثات كاما عالیة الشدة ضرورات العمل بهذه التقنیة تصمیم منهج تدفق عملیات مناسب یضمن استرداد كل كمیات الیورانیوم الداخلة الى منظومة ان كثرة المتغیرات الداخلة في بلوغ .الفصل وتقلیل الكمیات المفقودة منها في مسالك النفایات النوویة الى أدنى ما یمكن ستدعي استخدام البرامجیات الخاصة بالحسابات النظریة المعروفة في هذا المجال وتحدیدا التصمیم المناسب لهذا المنهج ، ی وقد اجریت العدید من التجارب النظریة التي تمخضت عن اختیار الظروف التشغیلیة المثلى SEPHIS codeبرنامج سفس بقت الحقا میدانیا ، وكانت النتائج العملیة المستحصلة قد عززت بالف عل أفضلیة المنهج الذي اختیر من الحسابات والتي ط . النظریة وم السداسي المشعشع ،نواتج األنشطار الالعضویة یالیوران:الكلمات المفتاحیة IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 Recovery of High Concentration Hexavallent Irradiated Uranium From Inorganic Fission Products Received in : 1 April 2010 Accepte d in : 27 September 2010 S.A. Jassim Departme nt of Chemistry ,College of Science , Unive rsity of Diala Abstract In this study , extraction of irradiated high concentration hexavallent uranium from fission p roducts ( high gamma radiation ) was carried out using multistages countercurrent continuous technique (mixer setller) , employing this technique requires a design ing flow sheet that recover all the amounts of uranium and to minimize its losses in the nuclear wast e st reams. Due to the several p arameters required to reach this design, SEPHIS p rogram which is one of the famous code in this field were used to select the op timum conditions through many theoretical runs , finally the exp erimental r esults give a good assurance in SEPHIS r esults and its optimum conditions. Introduction Irradiation of uranium in nuclear reactor p roduces many inorganic short and long lived isotop es such as 131 I, 140 La, 141 Ce , 144 Pr , 95 Zr, 95 Nb , 137 Cs, 90 Sr and 91 Y in addition to other several isotop es .Uranium ions in aqueous solution can give very comp lex sp ecies because of its several oxidation st ates. The Latimer diagr am for uranium in acidic medium is[1]: It shows t hat p entavalent state is unst able and should disp rop ortionate to tetravalent and hexavalent . Uranium (I V) ions can easi ly be oxidized to t he hexavalent state , which is the most st able oxidation st ate of uranium in acidic solution[2] , so reaction of uranium(IV) oxide with nitrate results in the formation of urany l nitrates UO2(NO3)2 , in this formula , the nitrate groups are bidentate , binding this salt with TBP gives uranium with 8 coordinate , this imp ortant p rop erty lies in its high solubility in a range of organic solvents.[3,4,5] IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 The extraction of hexavalent uranium from some inorganic sp ecies in nitric acid media by tributy l p hosp hate (TBP)/kerosene has been st udied p reviously , TBP is highly selective for hexavalent uranium, and p rovides excellent decontamination from most radioactive inorganic imp urities .The equilibrium constant of t he extraction reaction of uranium by TBP: UO2 + 2 + 2NO −3 + 2TBP UO2(NO3)2 · 2TBP Dist ribution ratio (Du) of uranium ( which means [U]org/[U]aq )increases with t he increase of both uranium and nitric acid concentration to reach the ma ximu m at 5 M HNO3, The decrease of uranium concentration in the organic p hase after this maximu m can b e exp lained by the fact that nitric acid will co mpete with UO2(NO3)2 , to form HNO3•TBP, and HNO3• 2TBP. [6,7,8,9,10] . In industry , sep aration and extraction of metals requir es sp ecial techn ique called “multistage countercurrent continuous p rocesses”. In the multistage p rocesses, the aqueous raffinate from one extraction unit is fed to the next unit as the aqueous feed, while the organic p hase is moved in the opp osite direction. Hence in this way even if the sep aration between two metals in each st age is small, the overall sy st em can have a higher decontamination factor [8]. Due to several p arameters influence the extraction p rocess such as uranium concentration, nitric acid concentration, number of st age, TBP concentration and flow rates of organic and aqueous feed solutions , it is very imp ortant t o design flow sheet of main p rocess to reach the optimum conditions required for successful separation. To do t hat , it is necessary to start with computer aided p rocess flowsheet calculations .One of the most imp ortant comp uter code in ur anium reprocessing is SEPHIS (solvent extraction p rocess having interacting solute) code developed at Oak Ridge National Laboratory . The SEPHIS code p redicts the equilibrium distribution of uranium , p lutonium (IV) , nitric acid and water between aqueous p hase containin g these comp onents and an organic p hase containing TBP at any concentration[9]. SEPHIS - gu ide f low sheet op timization studies and thus minimizes the amount of exp erimentation required to establish a particular set of op erating conditions[10,11]. Decontamination of irradiated uranium fro m fission products is one of real op timization of flow sheet and this is carried out due to selection of suitable solvent/feed ratio , low ratio will lead to higher saturation of the solvent with uranium and p ossibly maximize decontamination of p roduct st reams[12,13]. Experime ntal 1- Reagents *Nitric acid to p repare different concentration solutions ( 3.75 , 1.5 , 0.03 M ). *Organic solvent , T ributy l phosp hate (TBP) , diluted in oderless kerosene (30%TBP/kerosene). *Urany l nitrate to p repare 170g/l uranium in 3.75M nitric acid. 2- Equi pments: *Two mixer sett lers battery ( 16 stage for each), one for extraction and the second for st ripping , hy draulic equilibrium have been carried out for both units with the same solutions flow rates and concentration of nitric acid as summarized in fig. 1 * four metering p ump s for feeding solution through 4 st reams ( organic , feed , scrub , and st rip ). *two glove bo xes to p revent any contamination from uranium solution. IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 3- Mesurments. a-De termination of uranium Two methods were chosen for the determination of uraniu m namely sp ectrop hotometric method and Davis & Gray method [14]. Sp ectrop hotometric method was used for the determination of uranium at m icro gram/aliquot level . This method is based on se lective extraction of ur anium as tetrap ropy lammonium –uranyl trinitrate comp lex and co lour dev elop ing with dibenzoy l methane .The absorbance was measured at 415nm. Davis & Gray method was used for the determination of uranium at gram/ aliquot level ,this method is based on the reduction of uranium (VI) to uranium (IV) in a concentrated p hosp horic acid solution containin g sulp hamic acid. The excess of f errous is subsequently oxidized by nitric acid in the p resence of M o(VI) cataly st . After adding sulfamic acid and diluting the mixture with water, the determination to be comp leted by titration with standard p otassium dichromate solution using M etrohm p otentiometer by incremental addition. b- De termination of fissi on products Fission p roducts activity were measured usin g GeLi detector of 97 cm 3 active vo lume and 4096-multichannel analyser , Camac ADC-type 9060 linked with HP-computer (Princeton- Gamma Tech , Germany ). 4- SEPHIS program model for theoretical st udy to select t he optimum conditions flow sheet , using p c. computers to carry out this job. Equip ments have been supp lied from chemistry research center in Tuwaitha. Results and Discussion Theoretically , 24 SEPHIS calcu lations run were carried out , the results (as summarized in table –1) indicate the followin g: 1 - I n t h e e xt r act io n u n it , t h e lo s s o f u r an i u m in aq . w as t e is s o lar g e ( ar o u n d 44.1g/l ) when the ratio of org./feed flow rate equals 600/440 ( run-1) , but when keep ing all other input p arameters intact , this amount should decrease gradually to (21g/l) when the ratio been 600/360 (run 1-5). It can b e also concluded that t he follow runs (6-10) consistence with this idea. 2- Run (11-19),reduces scrubbing solution (1.5M Nitric acid for all runs as shown in table-1) from 120 to 100 ml/hr results in a decr eased the uranium in aq.waste , and this means that t he IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 ratio between org./scrub is also important t o imp rove the extraction process . 3- In st ripp ing unit ( different acidity of nitric acid were used as summarized in table-1) , when or g. /st rip r ati o equ als 1 ( ru n 1- 16 ) , p oo r st ripp in g o f u r anium w as not ice d , and unaccep table amount were lost in the organic wast e , increasing this ratio (run 17-19) will imp rove r ecovery of ur anium in the p roduct and low ering its loss es in the o r g. wast e . 4- Reducing st rip acidity ( run 20-22) will imp rove the condition of or g. wast e and on ly trace amount of ur aniu m will app ear in this st ream, whi le run 23 shows bad extraction du e to increasin g or g. /feed ratio relative to t he previous run. 5- Finally , the goal of this theoretical st udy is to reach the optimum p arameters , and the final run ( 24) clear ly demonst rate that this run reflects t he optimum conditions due to ultra trace amo u nts of u r aniu m in o r g. and aq . wa st e w h ich equ als 1 0 - 12 g/l in b oth st r eams . Exp erimentally , (fig -1) shows the app lication of optimum condition (results from theoretical calcu lations) in laboratory ,simulation solutions were p rep ared by adding differ ent isotop es gamma radiation emitt er to 170g/l uranium solution , the lost of uranium in the aq. and org. wast e is so small and acceptable in such exp eriment and the difference b etween theoretical and exp erimental results is due to the fluctuation of solution p ump s flow rate which altered the ratio of streams , so it is very necessary to obtain the best results from SEPHIS calculation and ap p lied them in lab. to give reasonable and acceptable exp erimental results . On t he other hand , working near saturation of the solvent with uranium ( below Saturation not over) will give good decontamin ation factor of uranium fro m fission p roducts, and no gamma sp ecies were detectable , neither in product nor in or g. wast e and all of them (f ission sp ecies) flow t oward aq.waste Re ferences 1.Beck ett , M . A. and Platt ,W.G ( 2006) the p eriodic table at glan ce, b lackwell p ublishin g Ltd.,UK.( books.google. com),99. 2. Vo gel ,A. and Svehla,G. (1996) , Vo gel's qualitative inorganic analy sis , 7 th Ed. , (books.goo gle. com) , 347. 3- Cotton ,F.A. and Wilkinson ,G. (1967),Advanced Inor ganic Ch emistry , 2 nd Ed., John Wiley and Sons,UK.,1102 4 - Cott on , S. (2 00 6) Lanth an ide and A cti n ide Ch emist ry , Jo hn Wiley and Sons UK . IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 (books.goo gle. com),179 5- Wiberg, E. ; Wiberg,N. and Holleman , A.F. (2001), Inorganic Chemist ry , Academic p ress (California)(books.goo gle.com),1713 6- STAS, J. ; Dahdou ,A. and Sh lewit , H. (2005) ,Periodica Polytechnica Chemical En gineering, 49(1): 3–18 7- Alibrahim ,M . and Shlewit ,H. (2007) ,Periodica Poly technica Chemical En gineering, 51(2): 57-60. 8- Venkatesan,K.A. ; Sukumaran, V. ; Ant ony ,M .P. and Srinivasan,T.G. (2008) , J.of Nucl. and Rad.Sci., 9(2): 37-39. 9-John, J. M cKetta, and William A. Cunnin gham, (1984) Ency . of chemical processing and desi gn ,volume-21:. 10- Wright ,A.D. (2008) A t hesis submitted in p artial fulfillment, of the requirements for the,M aster of Science Degr ee in Chemistry , University of Nevada, Las Vegas 11- D eP aoli ,D. (2 00 8) M o deling and Si mulat ion o f Nu clear Fu el R ecycling Sy st ems, Oak Ridge National Laboratory . 12- Collins,E. D.; Benk er,D. E. ; Bond,W. D. ; Camp bell D. O. and Sp encer,B. B. (2008) Oak Ridge National Laboratory , TN 37831-6176. 13-M . C. Thomp son, ;M . A. Norato, ;G. F. Kessinger,; R. A. Pierce, ;T. S. Rudisill and J. D. Johnson, (2002), Savannah Riv er Comp any, WSRC-TR-2002-00444, 30. 14-Davis W. and Gray W. 1946, Talanta 2:1203. IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 Table(1): S EPHIS Code Calculations Run no. [H + ] st rip [H + ] feed [H + ] scru b Flow rate ml/hr Feed org. scrub st rip % U. Recover y U. g/l AQ.wast e U. g/l Org.wast e 1 0.1 4 1.5 440 600 120 600 64.3 44.5 6.89 2 0.1 4 1.5 420 600 120 600 67.38 39 6.89 3 0.1 4 1.5 400 600 120 600 70.73 33.7 6.89 4 0.1 4 1.5 380 600 120 600 74.4 27.6 6.89 5 0.1 4 1.5 360 600 120 600 78.4 21.0 6.6 6 0.1 4 1.5 400 620 120 620 73.1 29.4 6.23 7 0.1 4 1.5 400 640 120 640 76.4 24.99 6.85 8 0.1 4 1.5 400 660 120 660 79.3 20.7 6.9 9 0.1 4 1.5 400 680 120 680 82 16 6.9 10 0.1 4 1.5 400 700 120 700 85.7 11.6 6.9 11 0.1 4 1.5 400 620 100 620 76 26 6.18 12 0.1 4 1.5 400 640 100 640 79 22.1 6.87 13 0.1 4 1.5 400 660 100 660 82 17.4 6.94 14 0.1 4 1.5 400 680 100 680 84.9 12.7 6.94 15 0.1 4 1.5 400 700 100 700 87.88 8 6.94 16 0.1 4 1.5 400 750 100 750 92.5 2*10 -11 6.42 17 0.1 4 1.5 400 750 100 775 94.7 2*10 -11 5.44 18 0.1 4 1.5 400 750 100 800 97.6 2*10 -11 3.33 19 0.1 4 1.5 400 750 100 825 97.6 2*10 -11 2.5 20 0.06 4 1.5 360 700 120 800 ≥98.5 2.4*10 -11 2.6*10 -5 21 0.05 4 1.5 360 700 120 800 ≥98.5 2.4*10 -11 3*10 -6 22 0.04 4 1.5 360 700 120 800 ≥98.5 2.4*10 -11 3*10 -8 23 0.03 4 1.5 380 700 120 800 96.3 5.2 1.6*10 -10 24 0.03 4 1.5 360 750 120 850 ≥ 98.5 5.2*10 -12 6.2*10 -12 IBN AL- HAITHAM J. FOR PURE & APPL. S CI. VOL. 24 (1) 2011 Feed scrub Strip Org. Product Aq.waste Org..wast e U g/l 170.47 ------------- ------------- ------------- - 70.54 0.011 0.011 %TBP- kerosen e ------------- - ----------- ------------- 30% ------------- - --------------- - %30 HNO3- M 3.75 1.5 0.03 ----------- 0.26 --------------- --------------- - Gama dp s 2.8*10 6 -------------- - ------------- - ------------- - Nill All Gama Nill Flow rate ml/hr 360 120 750 850 ----------- ----------- -------------- Fig.(1) : Experime ntal Run at Ste ady S tate Usi ng Extraction and S tripping Units Org.Feed scrub strip Aq.waste Product Org. waste 16 9 1 1 11 1 32 17 Stripping unit Extraction unit