1. SYNTHESIS, STRUCTURE AND PROPERTIES OF ZIRCONIUM(IV) AND URANYL PERTECHNETATE AND PERRHENATE K. E. German, M. S. Grigoriev Institute of Physical Chemistry of RAS, Moscow, Russia

2. Tc behavior in PUREX Formation of pertechnetate complexes with zirconium(IV) and uranium(VI) is the key point of Tc behavior in PUREX reprocessing of the spent nuclear fuel: in Russia, Japan, France, USA and England (groups of F.Macasek, D.Pruett, A.Akopov, P.Baron …) As for U(VI), Volk and Belikov have shown that uranyl pertechnetate can form a dihydrate salt while crystallized from its aqueous solutions. This behavior is different from that of uranyl perchlorate forming higher hydrates (with NO coordination). –The item is technologically very important but we have NO structural support of U and Zr complex formation with TcO4

3. [(Np VI O 2 ) 2 (Tc VII O 4 ) 4. 3H 2 O] Fedoseev A., Krupa J.C., Budantseva N., Grigoriev M.S., German K.E. XXIX-Journees des actinides, Luso, Portugal, 1999 [(NpO 2 ) 2 (TcO 4 ) 4 *3H 2 O] - ribbon structure in space group P -1, Z = 2, a = 5.322(2)A, b = 13.034(4)A, c = 15.460(4)A,  = 107.08(2) ,  = 98.05(2) ,  = 93.86(2) . The ribbons formed by two structure independent Np0 2 2+ groups bonded one to another by bidentate bridging pertechnetate groups. One Np0 2 2+ group also coordinates 3 water molecules the other Np0 2 2+ has all 5 equatorial positions occupied by coordinated TcO 4 groups: four bidentate and one monodentate. The ribbons are finally bonded into a three-dimensional structure by hydrogen bond AS Np(VI) IS LESS IMPORTANT COMPARED TO Np(V) THIS RESULT WAS CONSIDERED TO BE OF MODERATE IMPORTANCE

4. Ribbon structure of neptunyl dipertechnetate sesquihydrate [(NpO 2 ) 2 (TcO 4 ) 4 *3H 2 O] n from Fedoseev A.M., Krupa J.C., Budantseva N.A., Grigoriev M.S., Guerman K.E. XXIX-Journees des actinides, Luso, Portugal, 1999 The only structure which was available for actinides and Tc!

5. Zr(TcO 4 ) 4. 4H 2 O Compound Zr(TcO 4 ) 4. 4H 2 O was prepared by reaction of ZrO(CO 3 ) with 20% HTcO4 followed by evaporation to dryness with P 2 O 5. The crystals were white colored and plate by shape. Chemical analysis supported 1:4 ratio of Zr to Tc and 4 water molecules present. The X-ray pattern for Zr(TcO4)4*4H2O is given below Indexing with modern crystallographic programs failed No isostructural compounds found

6. Some chemical properties of Zr(TcO 4 ) 4. 4H 2 O The compound Zr(TcO 4 ) 4. 4H 2 O was hygroscopic and hydrolyzed in excess water to form a new compound with smaller Zr:Tc ratio (~1:2) and partial release of HTcO 4 responsible for the red color of the formed concentrated solution. This finding strongly supports the importance of hydrolytic studies for Zr(IV) even in highly acidic solutions and complicates the question of the forth of pertechnic acid in concentrated solutions.

7. Determination of [(U VI O 2 )(Re VII O 4 ) 2. 1.5H 2 O] structure For indexing [(U VI O 2 )(Re VII O 4 ) 2. 1.5H 2 O] we have generated the theoretical X-ray powder diffraction pattern for [(Np VI O 2 ) 2 (Tc VII O 4 ) 4. 3H 2 O] and [(Np VI O 2 ) 2 (Re VII O 4 ) 4. 3H 2 O] (based on single crystal analyses and considering that Re and Tc salts should be isostructural). We obtained for [(U VI O 2 ) 2 (Re VII O 4 ) 4. 3H 2 O] the unit cell with the following parameters: a =5.324(2) Å, b = 13.073(8) Å, c = 15.495(4) Å,  = 107.27(3) ,  = 97.94(3) ,  = 94.04(2)  (sp. gr. P-1, Z = 2). So we concluded that it is completely isostructural to [(Np VI O 2 ) 2 (Re VII O 4 ) 4. 3H 2 O] and therefore its formula should be duplicated compared to that proposed by Silvestre and Freundlich thus representing two U with different coordination of TcO 4.

8. X-ray pattern analysis has shown : Complete isostructure of Uranyl and Neptunyl Pertechnetate and Perrhenate experimental simulated from experimental single crystal structure

9. Structure of [(U VI O 2 ) 2 (Re VII O 4 ) 4. 3H 2 O] As Re and Tc salts are isostuructural  Same structure should be valid for [(U VI O 2 ) 2 (Tc VII O 4 ) 4. 3H 2 O]

10. Conclusion The structural study led us to conclusion that there is strong coordination between actinide(VI) and permetallate(VII) ions in solid and concentrated solutions (some about 2-5 M by pertechnetate) where these compounds are formed from (and most probably for organic solutions in TBP). It is quite typical not only for Np(VI) with pertechnetate but also is valid for U(VI) with perrhenate and should be favorable for U(VI) with pertechnetate.