 One of the major application of this actinide chemistry has been in the nuclear fuel cycle. As I have mentioned in the previous lecture, how this separation science is important in the front end of the nuclear fuel cycle, where the uranium separation is done from the least weaker using the DAPEX or the AMEX processes. And in the back end of the nuclear fuel cycle also the purex process is very, very important. Now, I give a brief overview of the nuclear fuel cycle here. So, actually it is coming from the mines we have the uranium ore and it is coming this is first we have the mining and then the milling and where we have the uranium product is there. The milling plant it goes to the fuel fabrication wherever required enrichment is done. In other cases directly also natural uranium can be used as a fuel. And this fuel goes to the nuclear reactor and after a particular period of time the fuel is removed from the nuclear reactor which is called now the spent nuclear fuel or SNF. The SNF is kept for storage. This one is a storage facility under water. And after a few years time when the radioactivity has become significantly lesser then the spent nuclear fuel is used for the nuclear fuel reprocessing. After reprocessing there is a waste management step in the nuclear fuel cycle where some of the valuable radio nucleates are separated before vitrification of the radioactive waste. There is another fuel cycle which is called the open fuel cycle where this reprocessing is not done and the spent nuclear fuel is directly stored in different parts. It can be directly stored in huge tanks as solution from and also this spent nuclear fuel can be vitrified and kept in the repositories. So, these are the basic strategy for the open fuel cycle or the closed fuel cycle. In case of the closed fuel cycle after the hand fuel reprocessing the recovered uranium and plutonium are again given to the fuel fabrication which is in turn given to the nuclear reactor and that is how the nuclear fuel cycle operates. Now, whatever is coming from the nuclear fuel reprocessing plant that we call as the raffinate and it contains mostly the fission products and also the trans plutonium elements that is americium, curium etc and neptunium which is one of the major minor actinide element this also is going for the vitrification. Now, vitrification means this fission product as well as the activation products are converted to their oxides and glass form is made and that glass should be kept under deep geological repository for a number of years. However, the problem is that some of these minor actinides like neptunium 237 they are a very long half-life and this has to be monitored that means these glass blocks has to be monitored for a very long period of time that is millions of years and also there is a question mark on the integrity of these waste blocks over such a long period of time due to natural calamities like earthquakes or volcanic eruption and also deformation by heat under the repository conditions. So, because of that there is a strategy called partitioning and transmutation or termed as the P and T which is actually tested at different laboratories of in different countries for to separate out the long-lived minor actinides and it is called as minor actinides this is mostly actinides like neptunium americium and curium major amount of these actinides are called as minor actinides and other actinides which we call as the major actinides are plutonium and uranium which are any of separated by the complex process. Now, this partitioning and transmutation as two steps one is called the actinide partitioning where the minor actinides are separated from the raffinate which is concentrated to be termed as high level waste this high level waste it contains more than 97 percent of the radioactivity which are involved in this nuclear fuel reprocessing and this high level waste is the major stores of this minor actinide and also the efficient products like CJ-137 and Strontium-90 which give lot of dose to the working personnel. So, the strategy is to separate the minor actinides and also that of the efficient products like cesium and strontium are shown here in the schematic that is how this man drain problem or the dose to the working personnel can be minimized and these actinides which are separated they have the advantage that is that as the figure is given here see the as a function of time up to a million years relative radio toxicity is plotted here if you do not have this nuclear reactor or the nuclear energy program then the dose is actually which is the background which is from the uranium ore only and if you do not have this actinide partitioning and whatever activity is coming starting from the initial period of this and nuclear fuel you have a very high level of radio toxicity that is around 10 to the power 4 and over the period of time it will decrease but to come to the background level of the uranium ore it will take nearly 10 to the power 6 years but if you go for this partitioning that is you separate the minor actinide that is neptunium curium and americium from the high level waste then this radio toxicity can fall relatively faster and in about 1000 years you will have this radio toxicity coming to that of the background level that is that of the uranium ore so now this minor actinide partitioning has been one of the challenging topics and little different labs are working on this the americans started research into the minor actinide partitioning using several phosphorus based compounds most prominent of them is called the cmpo structure is given here which is full form is carbonyl methyl phosphine oxide and subsequently they have developed a process called the true x process this process name is true x process that is trans uranium extraction true x process subsequently the friends people they have developed a extractant which are called the malonamides or tetraalkyl malonamides one example is given here that of the dmdb tdma or dimethyl dibutyl tetradesyl malonamide this is falling in the same class of malonamide extractants and the french people have developed the process called the diamax process which is a diamide extraction process which is very very popular in the european indian laboratories however these processes are not yet used for the waste management of the minor actinide at the same time these chinese people they have tried trpo or tri alkyl phosphine oxide the commercial reagent which is available is the cyanx 923 and the structure of this extractant is given here there are is the alkyl group this has been used for the actinide partitioning from nitric acid media and the japanese people have also used another extractant which is called the dilpa or the dye iso dehyde phosphoric acid and finally another japanese group has come up with an extractant called the dye glycolamide or the dga and the structure of this is given here is a tetraoptile dye glycolamide or to dga or tolga so by far this tolga has been the one of the most efficient extractant for the actinide partitioning so i will be just briefly mentioning about these different processes first is the 2x process which i mentioned for the cmpo structure of cmpo is given here the extractant used is 0.2 molar but as it forms third phase with the dilvate and also on the nitric acid concentrations which is prevailing in the high level waste that is 3 to 4 molars so tpp has been used as a phase modifier and 1.2 to 1.4 molar tpp has been used along with the 0.2 molar cmpo as the 2x solvent the diluent in this case is the paraphenic hydrocarbon the extraction drain is plutonium 4 plus is extracted higher than that of the uranil which is higher than that of the americium 3 plus nevertheless the extraction of americium is significantly high you get a distribution ratio of around 25 to 30 using the solvent mentioned above that is a 2x solvent and this solvent extracts not only americium 3 plus it also extracts the trivalent lanthanide ions because this extractant cannot distinguish between the trivalent actinides and lanthanides and then there is a process called set fix with the solvent extraction of trivalent f elements intra-group separation in the cmpo complex and system where dTPA sodium nitrate has been used for the selective stripping of the actinide ions that is the trivalent actinide ions. So, the set fix is used in conjunction with the 2x process for a direct separation of the trivalent actinides from the lanthanides. Now, we will be coming to the trivalent actinide lanthanide separation in a more detailed dialogue subsequently in this lecture. The disadvantage of this 2x process or the cmpo process with our phosphorus base extractants are used that is both cmpo as well as tbp they are containing phosphorus so that is how they will be leading to large volume of solid waste production and also there are stripping issues that means it is not so easy to strip the trivalent actinides. So, subsequently researchers have developed a buffer medium which is used for the stripping of the trivalent actinides, but the hexavalent actinide like uranil ion is stripped very comfortably by sodium carbonate solution and plutonium 4 plus is stripped by the oxalic acid medium. So, that is how there is no problem so far the stripping of the tetravalent and the trivalent actinide ion, but trivalent actinide ion there is some problem stripping within the cmpo extraction system. Similar to the cmpo extraction system this phosphinoxide there is a trialkyl phosphinoxide process under TRPO process has been developed at China. Here this again complex thing group is the phosphoryl group similar to that of the cmpo, but the cyanx 923 which is commercial available and also is a cheap extractant compared to cmpo it has the problem that you cannot carry out the extraction from the actual high level waste condition that is 3 to 4 molar nitric acid. So, what has to be done is that the feed has to be diluted to tune in the extraction of the actinides from the high level waste. So, the disadvantage is that you need to dilute the feed which is resulting in lot of waste volume and also if the nitric acid concentration is little higher then extraction of the trivalent metal ions is yes. Nevertheless the extraction of tetravalent and exhalant actinide ions is not a problem the high nitric acid concentration because this trialkyl phosphinoxides they are very strong extractant of the tetravalent as well as exhalant actinide. Another process as I mentioned by the Japanese group is the phosphoric acid based extractant it is called the DITPA process or the isodesyl phosphoric acid the structure of the extractant is given here. So, again this forms third phase so that is why the mixture of DITPA and TBP is used and the high level waste acidity has to be brought down to around 0.5 molar otherwise the extraction is not very efficient. In this case also the feed has to be denitrated otherwise the waste volume will be very very large that trivalent actinides and trivalent lanthanides can be separated in from the DITPA extract using DTPA as the complexing agent and the plutonium is stripped by the oxalic acid and uraniline by sodium carbonate. CMPO process or the 2x process the TRPO process and the DITPA process all these three processes are having phosphorous based extractants and that is why there is a problem of solid waste generation and in view of this the CHON type of ligand has been used by the Prince research groups and that is how this dynamics process was evolved. So, they are used as I already mentioned the malonamides or the tetra alkyl malonamides so which are actually alternative to the 2x process and very very efficient. But the major problem with the dynamics process is the third phase formation at higher nitric acid concentrations acid itself forms third phase and also the larger concentration of the extractant is required to carry out the extraction of it. So, finally, as I mentioned this di-glycolamide is considered the most promising extractant out of all these extractants. So, TODCA or Todga has been tested and a comparative evaluation of Todga Sinex 923 which is used in the TRPO process, DMDB TDME, TDMF which is used in the damage process and CMPO plus TDP which is used in the 2x process has been given in the left hand side figure where the distribution ratio of americium as a function of nitric acid concentration is given the diluent for all cases is n-todeca and as you can see with the 0.1 molar Todga the extraction of americium has been most efficient compared to the other three types of extractants and as you can see here in case of the Sinex 923. The extraction of americium becomes very very less with increasing nitric acid concentration. Now, when we go for this Todga type of extractant DGA type of extractants, the extraction mechanism is relatively unusual we can say as compared to that of the all previous extractants I have discussed that is CMPO, TRPO, diamide and also didpa in which case the extraction train follows that of the ionic potential of the metal ions that is plutonium 4 is extracted higher than that of uranium 6 which is in turn extracted higher than that of americium 3 plus. In all cases americium 3 plus extraction has been for the lowest out of these three metal ions and in case of Todga we will find that this extraction trend has become different that is americium 3 plus extraction has become more than that of plutonium 4 plus which in turn has been more than that of uranium ion. The relative extraction profiles of these metal ions is given in the right hand side figure and see here this americium extraction is much much higher than that of plutonium extraction presented by the red line and also this trigeland lanthanide extraction that is the european ion extraction is marginally larger than that of americium extraction and plutonium extraction is less than that on the other hand the uranium extraction is significantly lower which is shown here and the fission products like storm and cesium are very very poorly extracted which is not shown in this figure. Now once this actinides are partisan that is separated from the high level waste what we get in the product is the lanthanides that is the trivalent lanthanides and the trivalent actinides. So, along with americium 3 curium 3 we have a whole lot of trivalent lanthanides which are also extracted and this trivalent actinides and lanthanide separation is therefore one of the very very important steps in the radioactive waste management program this as I have already mentioned that before vitrification we have to do the partisaning and transmutation if we have to bring down the surveillance period from millions of years to around 1000 years or so. So, for that lanthanide actinide separation has to be done now why lanthanide actinide separation has to be done as already mentioned in the previous slides thus this lanthanide extraction is comparable to that of actinides that is the trivalent actinides and lanthanides have very large neutron absorption cross sections. So, that is how this when you are using this actinides for burning in a reactor. So, this lanthanides will be acting as neutron poisons and they will be bringing down the efficiency of the reactors. Also, as I have given here this table in the right hand side and see some of the lanthanide isotopes their cross section is given in barns you see that they are very very high neutron absorption cross sections. So, they act as neutron poisons and they decrease the reactor efficiency also if the lanthanides are not separated from the actinides. So, if you carry out the vitrification of the radioactive waste then lanthanides they form separate phase during vitrification and they complicate the vitrification process. Also lanthanides have a significantly larger volume than that of the actinides by saying larger volume in what I mean is the amount of lanthanides produced in the nuclear fission is much much more than the amount of minor actinides like aniseum and curium which are formed by the nutrient capture reactions. It may be about 1000 times higher we get the lanthanides from the fission. So, that is how if you lanthanides are separated from the trivalent actinides then the waste volume can be brought down very very significantly. That means, in a very small volume we can contain the radioactive waste trivalent lanthanides are removed from the radioactive waste. The trivalent actinides can also be used like amnesium 3 can be used for the transmutation or heterogeneous recycling that is how we can disintegrate these trivalent actinides. Now, the processes which are used for the lanthanide actinide separation I have already discussed the Tramex process where there are tertiary amine extraction that is tertiary amine is used for the extraction of the americium and curium in the trivalent state from strong chloride medium that is around 11 molar lithium chloride and that is how the separation is done. The trivalent actinides are extracted to much larger extent than that of the trivalent lanthanides. There is also another process called the Talspeak process. I mentioned about this Talspeak process I will be mentioning in the next slide. Also, there are processes like TrueSpeak which is coupled to the TrueX process, reverse Talspeak and all state processes which I am not going to discuss here but I will be giving details of the Talspeak process where aminopoly carboxylates are used for the complexation of the trivalent actinides. So, in this case the trivalent lanthanides are there in the organic phase and trivalent actinides are brought into the active space by selective complexation with aminopoly carboxylate ligands. This is again the application of the actinide complexation what we have studied using the multipotent carboxylic acid ligands. There are also nitrogen donor extractants for this lanthanide actinide separations and there are processes called Sanex of the selective actinide extraction, Sanex. So, there are several Sanex processes, Sanex 1, 2, 3 which use nitrogen donor ligands that is the aromatic hetero polycyclic ligands are used and also there is another process called the Sanex 4 which is based on the sulfur donor ligands which is a diethiophosphonate type of ligand. Then there is also there is something called a regular Sanex or R-Sanex. Once is Sanex or a once cycle Sanex which I am not going to discuss here which uses aromatic hetero polycyclic and there is another one called innovative Sanex process where aromatic hetero polycyclic ligands are used which are acoust soluble. So, I will be briefly mentioning about these processes which have been studied by the European Union and also other countries including India. So, first I come to the Talspeak process. So, here the extractant is HDESP which is Di2 ethylhexyl phosphoric acid as I mentioned in the DAPEX process and we have the solution of this HDESP and the complexing medium which is that is the aqueous medium is 0.05 molar DTPA this is the amino polycarboxylic acid that is diethylene triamine pentacetic acid and one molar lactate that is the one molar lactic acid at pH 3 to 3.5. The separation factor of European and Amershiam the ratio of their distribution ratio values is around 19 which is obtained in case of the Talspeak process. This has originated in the United States of America and has been other countries also have carried out lot of research in the Talspeak process. This is a species of this whatever is shown here from ESI-MS this species has been shown here where the complexes of the trivalent lanthanides has been shown here with the HDESP extractant and also this Amershiam they form the complexes with the amino carboxylic ligands. As I have already mentioned during the complexation lectures depending on the type of this carboxylic acid extractants this log beta value of the actinides can be fine tuned as per the requirement so that you get benefit during the complexation. So here you can see that this acetate is given here and compared to that nitrilyl triacetic acid and EDTA ethylene diamine tetrastate and also DTPM is the diethylene triamine pentacetic acid. So DTPM forms a very strong complex with the trivalent actinides with the laboratory constant much higher than that of the trivalent lanthanide ions you can see here this value is given for the neodymium here and that of the trivalent actinide here. So you see this value for DTPM which is much higher for the trivalent amershiam than that of the neodymium that is how the separation is done. Now the limitation of this tall peak process is there is a requirement of buffer because we need to work in the pH range that is pH 3 to 3.5. There is a process difficulty that is a large amount of secondary waste generation then in partitioning of lactate in the organic phase which has a very slow phase transport kinetics and this interactions are quite complex and complicated and poor selectivity over the early lanthanides whatever we have shown it is for europium amershiam or neodymium amershiam or since these figures I have shown but if it is a early lanthanides then there is a selectivity not as good as reported here. Then coming to the soft donor ligands whether those having sulfur or the nitrogen donors as I mentioned in the beginning of our this actinide complex chemistry that some of these trivalent actinides they in fact act as soft metal ions. So that means when we consider soft soft interaction and the basis of the HSAB concept or the hard soft acid based concept then they should be forming stronger complexes with the soft donor ligands there will be some covalent interactions. So that is how the soft donor ligands are used for this complexation with trivalent actinides. I have given example of some soft donor extractants that is the cyanx 301 structure is given here. This is a dikyophosphonic acid with two sulfurs which can be binding with the trivalent actinide and also there is another laboratory synthesized sulfur based ligand which is this bis chloro phenyl derivative of this cyanx 301 and this has given a separation factor beyond 10 to the power 3. The major problem of the sulfur donor ligands are their stability because the sulfur can get exchanged or degraded and you get the oxygenated products in those cases. So the stability of this extractant is one of the big problem when you are using the sulfur donor extractant. On the other hand, this nitrogen donor extractants which are mentioned here for the cyanx 1 process that is a selective actinide extraction process 1 that the top ingredient is the extractant used here and the separation factor between trivalent actinide and trivalent lanthanide that is amyretium 3 and europium 3 distribution ratio values is less than 10. When we have this separate this cyanx 2 extractant this extractant whatever shown here structure which again a heteropolycyclic extractant which is a nitrogen donors three nitrogen donors are there and it has a separation factor of around 10th and subsequently around 1999 there was a report in which this BTP type of extractant has been reported with the suppression factor greater than 100. So, but the major problem with all these nitrogen donor ligands is that this they are poor solubility in common organic diluents like endodicam which are used in the nuclear fuel cycle. So, you have to use very complicated solvent combinations for this separation using this nitrogen donor extractants. That is how in the last decade or so, there has been development to have a aqueous soluble heterocyclic compounds like one is shown here that is SO3 pH BTP this BTP is the extractant which is shown here. This is the R BTP that the alkyl group is termed as R here and this is the reagent which is used actually for the separation of lanthanides and actinides where this BTP derivative is a sulfonated BTP which is aqueous soluble and this process is called as the innovative sanics process where the suppression factor is reported to be greater than 1000. Now, after this trivalent actinides are separated from this trivalent lanthanides, then this amyricium can be burned in the reactor by the hydrogenous recycling, but always amyricium is associated with curium. So, recently there is a strategy which is evolving is the amyricium and curium separation. Now, why amyricium curium separation is required because some of the isotopes of curium like 242 and 244 curium they have high neutron and heat emission. So, it can complicate the fabrication of nuclear fuel. The separation can decrease the waste lifetime and also the radio toxicity if the curium can be separated and also this can decrease the long term waste heat power and shares repository resources. After this curium is separated from the amyricium, then this amyricium along with plutonium and uranium can be used in a heterogeneous recycling in reactors together they can be used as a fuel. Now, the strategy is that we can separate using specially designed complexing agents. One complexing agent is called TP-AEN, it is a complicated name, but I will read out it is a N N N N prime N prime tetrakis 6-carboxy pyridinyl methyl ethylene diamine and the structure is given here. So, this is the extractant which has been synthesized by the French research groups and they have used it for the separation of trivalent curium and trivalent amyricium. Usually the amyricium curium separation factor is around maybe 1.1 1.2 by any process you try to do it, but by this specially designed complexing agent they have found that the separation factor between curium and amyricium can be as high as 3.7. There are some reports very recently the Russian group they have developed a extractant which can give a separation factor as high as 7, but this is very very recent testing is going on in Moscow State University, but this method which has been reported by the French group also is quite good for cutting out separation of curium and amyricium. There is another way to separate amyricium and curium where amyricium 3 is oxidized electrically to the plus 6 state by a electrochemical method followed by a TBP extraction as I have already mentioned several times. These active meal ions are extracted to a much much larger extent than that of the amyricium 3 plus ion. So, that is how amyricium 3 plus this oxidized to the amyricil ion that is AMO2 2 plus ion by electrochemical method then it can be extracted selectively by the process which is called the cesan process. So, this is a newly developed process which is called cesan process which is selectively it can separate amyricium. Now, this is just given a flow sheet of this amyricium curium separation method where polka has been used as the extractant in the organic phase and TPAN has been used as the complexing agent. They have seen that this separation factor of around 3.7 to 4 can be obtained when you have 2.5 millimolar of TPAN in pH 1. Amyricium can be recovered from that and curium stripping can be done. This is part of this project of the European Union which is called the success project. Thank you very much.