# Presentation: 226809

## Minor Actinides Partitioning

- European research efforts in separation chemistry
- Claude Musikas
- (March 2006)

## Laboratories involved

- CEA-DEN: Commissariat à l’énergie atomique (France-Marcoule)
- CEA-DSM: Commissariat à l’énergie atomique (France - Saclay)
- UREAD: Univ.of Reading (U. K.-Reading)
- CTU: Chalmers Univ. of  Techn. (Sweden-Göteborg)
- ITU: Transuranium Institute, JRC (Germany-Karlsruhe)
- FSK-INE: Forschungszentrum Karlsruhe,GmbH, Institut für nukleare entsorgung (Germany-Karlsruhe)
- FSK-ISR: Fors.zent.,Institut für Sicherheitsforschung und reaktortechnik (Germany-Jülich)
- ENEA: Ente per le nuove tecnologie (Italy-Saluggia)
- PoliMi: Politecnico di Milano (Italy-Milano)
- CIEMAT: Centro de investigationes energéticas medioambiantales y tecnologicas (Spain -Madrid)
- UAM: Univer. Autonoma de Madrid (Spain-Madrid)

## Aim of the program

-  It applies to the back end of the nuclear fuels cycle  with  reprocessing , as a complement to the PUREX process.
-  It  will improve the safety of the nuclear waste storage.
-  The minor actinides (long half life) are separated and
-     will be transmuted by fission or spallation into lower
-     half life isotopes.
- —The potential radio toxicity of  the nuclear reactors
-    spent fuels as a function of time for different waste management options are  shown below.

## Slide 4

## Chemical problems of partitioning

- - Remove more than 99% of the actinides from the high level waste. (U (VI) , Np (VI,V), Pu( VI, IV) , Am(III), Cm(III)) .
- - U (VI) , Pu( VI, IV) are small amounts lost in the raffinate of the Purex process.
- - Np is more or less concentrated in the high level waste depending of the peculiar flow sheet used in the PUREX process.
-       Np(V) follows the fission products
-       Np(VI,IV) follow U or Pu and can be recovered from these flux.
- Am(III) and Cm(III)  remain  quantitatively with the FP in the first cycle.
- - ***The amounts of actinides are small compared with the amounts of fission products and a successful separation process must discard the large majority of non-actinide.***

## Separation of the actinides from the HLW(1)

- _Choice of the feed solutions_
-  -  The extraction of the minor actinides can be
-  implemented at two places in the PUREX process:
-         a: After the first cycle of separation of U + Pu
-              from the FP (HLR feed).
-          b: After the concentration - denitration steps of
-              the HLR (HLC feed).
-  - The main differences between these two options are:
-     Treatment of a smaller volumes in option b, by a
-     factor of around ten, but the process must be
-     designed to handle more concentrated solutions.

## Separation of the actinides from the HLW(2)

_**Choice of the extractant**_**.**
-     - Many extractants such as:
-      R                                                     H     H                               H     H
-         \                                                       \   /                                    \   /
* *R’P=O                                          R     C       R                      R     C       R’
-         /                                                   \   /    \   /                            \   /   \   /
-      R”                                                     P      P                               P     C     R’’
-                                                              /  \\    // \                            /  \\    // \   /
-                                                            R’  O   O  R’                    R’   O  O   NR”
- Phosphine oxide                      Diphosphine oxide          Carbamoyl phosphine oxide
-                                                                                                                       *  *
- were proposed all  over  the world these two past
-  decades to  extract the trivalent actinide or lanthanide from various effluents.

## Separation of the actinides from the HLW(3)

- For the European and  national French programs the extractant choice  was
-                               R’’    H
-                                  \   /
-                   R             C              R
-                      \          /    \            /             Substituted malonamides
-                      N C      C   N
-                      /         \\     //         \
-                   R’          O   O          R’
- These last years were devoted to select the substituents and  to  investigate the properties and the behavior of these new molecules when they are used in real processes such as the separation of  actinides from  genuine effluents Basically the advantages of the diamides were:
-  #  Non spurious degradation products
-  # Completely incinerable molecules, easy to synthesize
-  # Good adequacy with the separation problem:  extraction of the actinide + lanthanide nitrates and possibility to leave  most of the foreign metals in  the effluent which can be vitrified.

## Separation of the actinides from the HLW(4)

- _Selection of the diamide_
- _90 diamides_ have been synthesized and tested for minor actinide separations , two of them were selected for detailed investigations and this lecture  is focused on these two molecules.
-                      _The criteria of selection were the following_:
- - **Sufficient solubility in one aliphatic hydrocarbon TPH**
- (tetrapropyhydrogéné) which is used in the French PUREX plants.
-                              R     H
-                                  \  /
-                   H             C              H        *N,N’ **H** disubstituted malonamides*
*                     **\          /    \            /         rejected according to this *
-                      N  C      C  N
-                      /        \\     //         \
-                   R’         O    O          R’

## Separation of the actinides from the HLW(5)

- - **High distribution ratios between aqueous nitric acid and TPH.**
-      For that at least 20 C atomes must be present in the molecule.
**Sufficiently high Am(III) distribution ratios from 3-4 N HNO****3****  and low distribution ratios at lower acidities.**
- For that the pentaalkyl malonamides  (R’’H) are interesting because of the large values of the slopes: log  D Am(III) vs  log (HNO**3**)
-                  R’’   H                 *At acidity around 0.1 N HNO****3**** ; Am(III) *
*                            **\   /                   distribution ratios are close to 0.01*
-   CH3            C            CH3
-        \           /    \          /         *To extract sufficiently the trivalent actinide*
-        N    C     C  N          *it is necessary to have two CH****3*** as N
-        /          \\     //         \         *substituents**.*
-     R’           O   O          R’

## Separation of the actinides from the HLW(6)

- _Am(III) extraction (following)_
-     For the same number of carbons and the same aqueous nitric acid concentration  the extraction of Am(III) increases with:
-    #  the substitution of one H by a hydrocarbon chain R” in the  central CH**2** malonic group.
-    #  the number of carbons in R’’
-     #  the presence of one ether oxygen in position 3 in R’’
- So two molecules were selected for  the counter current separation tests in mixer-settler or in centrifugal extractors banks; and for the hydrolytic and radiolytic stability investigations.

## Separation of the actinides from the HLW(7)

-   C**14**H**29**   H                                                C**6**H13OC2H**4**    H
-              \  /                                                                      \  /
- CH3       C              CH3                                   CH3         C           CH3
-    \         /   \            /                                           \          /    \          /
-    N  C     C   N                                             N  C      C   N
-   /         \\     //         \                                             /        \\      //         \
- C**4**H**9**    O    O          C**4**H**9**                               C**8**H**17**      O   O          C**8**H**17**
-             _ __(DMDBTDMA_)     (27C)                  _(DMDOHEMA_)     (29 C)
- N,N’-dimethyldibutyltetradecyl           N,N’-dimethyldioctyltetradecyl
-               malonamide                             hexyloxyethyl  malonamide

## Separation of the actinides from the HLW(8)

**Distribution ratios of Eu(III) and Am(III) between the two malonamides**
**                                                            ****0.65M in TPH**
-                                   **DMDBTDMA           DMDOHEMA            C****HNO3**
-        DEu                  2.02                            3.4                     2.96
-        DAm                   4.58                           6.96                   2.96
-        DCm                                                    4.37                    2.96
-        DNd                                                    5.43                      2.96
-         DEu               0.012                         0.015                      0.5
-         DAm               0.019                          0.024                      0.5

## Separation of the actinides from the HLW(9)

-                              **Third phases boundaries**
-  As for many extractants the complexes formed  by malonamides with HNO**3** or the metals have a concentration limit in TPH , above which a second organic phase appears.
-  This phenomena must be avoided in solvent extraction counter currents processes and the merit of one solvent (extractant +   diluent) is dependent of the value of the third phase boundary.
-  For practical separations the charge limit in lanthanide is essential and governs the choice of the flow sheets.
- Measured values of phases boundaries are gathered in the tables below:

## Separation of the actinides from the HLW(10)

- Third phases boundaries for 0.65M extractant in TPH at 25°C
-                                                       DMDBTDMA           DMDOHEMA
- HNO3 aq (mol.l-1)                     4.9                             5.38
- Nd(III)org                                    0.041                         0.11
- HNO3 aq (mol.l-1)                         4                                3
- Nd(III)org                                      0.28                         0.11
- HNO3 aq (mol.l-1)                         0                                3
- U(VI)org                                      0.045
- HNO3 aq (mol.l-1)                       4

## Separation of the actinides from the HLW(11)

-                       **Hydrolytic and radiolytic degradation**.
-      The solvent hydrolysis and radiolysis have three deleterious effects on the processes:
-  a: the decrease of the extractant concentration
-   b: formation of products which could induce non desirable effects.
-     For example : the formation of strongly acidic organo  phosphorus  molecules by hydrolysis of  the neutral organophosphorus extractants such as (TBP, CMPO...). which  precludes the back extraction of metals
-   c: The formation of degradation products with surfactants properties which lowers the interfacial tension and  preclude easy phases  disengagements.

## Separation of the actinides from the HLW(12)

- Long duration hydrolysis tests of 0.69M DMDOHEMA were performed at 45°C in the presence of aqueous 3N HNO**3** .
-  The hydrolytic products identified in the solvent were very similar to those found after radiolysis:
- Various aliphatic carboxylic acids:  RCOOH
- Amide acid: CH3C8H17NCOCH(C6H13OC2H4)COOH
-  Secondary amine: CH3C8H17N
- Nitrosamine:  CH3C8H17NNO
- Monoamides :   RCH3NCOCH2R’

## Separation of the actinides from the HLW(13)

## Separation of the actinides from the HLW(14)Radiolysis

## Separation of the actinides from the HLW(15)Solvent regenerationAll the products formed in diamides degradation degrease the metals distribution ratios Most products are acidic and can be removed by alkaline washing with NaOH or Na2CO3 Some of the neutral products can be removed by acidic washing(amines)After this treatment and addition of diamide to compensate the losses one found that the properties of the solvent are regenerated.  One estimates that the solvent needs a regeneration cycle only after six or seven cycles in the continuous process. The neutral  organophosphorus extractants must be regenerated at each extraction-back extraction cycle.

## Separation of the actinides from the HLW(16)

- _Tests for the partitioning of  actinides using genuine PUREX first cycle effluents (HLR)._
- Most of the tests were carried out with DMDBTDMA .
- The co extraction  problems have been solved by adding completely incinerable complexants:
- H**2**C**2**O**4** and HEDTA in the aqueous phase.
-    The flow-sheets were optimized to separate quantitatively Fe(III), Zr(IV), Mo(VI), Ru, and Pd  which have a non negligible  affinity for the diamides solvents.
- The feed solutions were the HLR of a first cycle PUREX  treatment.

## Slide 22

## Element    Feed                        Recovery %    

-                ( ppm )             Raffinate       Ac/Ln     org. out
- ____________________________________________
- Y              32                      86                 14            0
- Sr              61                    100                  0            0
- Mo           304                   100                   0            0
-  Zr            140                  100                   0            0
-  Tc               7                     24                  62          14
-  Ru            141                   96                   3           1
-  Pd            207                  100                  0           0
-  Cs            553                  100                  0           0
- ____________________________________________
-  La             160                    0.19              99.8        0.01
-  Ce            283                    0.13               99.85     0.02
-  Nd            450                    0.15              99.85        0
-  Sm           138                     0.44              99.56        0
-  Eu             26                  < 1.63               98.34     0.03
-  U             203                    0.07               25.17    74.76
-  Np               4                   36.45              62.49      1.06
-  Pu                8                   1.18                98.34       0.47
- Am           550                    0.04               99.96       0
- Cm              46                < 0.32             >99.68       0

## Separation of the actinides from the HLW(19)

-                        _Tests with genuine HLC_
- The HLC are obtained by *concentration + denitration** of the *HLR.
- It* *has been checked that negligible amounts of actinides and lanthanides are lost in these two operations.
-     The precipitate formed at concentration contains mostly Mo and Zr and some Platinoids.
-  The volume reduction is about a factor 10 and 14.

## Separation of the actinides from the HLW(20)

-              _Tests with genuine HLC_

## 
    Element    Feed                        Recovery %    
               ( ppm )             Raffinate       Ac/Ln          org. out
Y              187                    1.2              98.8                0        
Sr              113                    100                0                0
 Mo            568                   99.3                0.6           0.1     
 Zr               98                   100                  0                0
 Tc              88                      0                    2              98
 Ru            938                   92                    6              1.1
 Pd           1014                  98.8                 0.9           0.3   
Cs            2915                  100                  0                0
 La            937                    0                 99.9             0.1
  Eu           131                  0.4                99.6             0.02
       U             207                   0.1               3.5              96.4
 Np           22                       2                  49              49
 Pu            48                   3.5                  26              70.1
Am          3570                0.005               99.7             0.3
Cm           213                 0.01                99.9              0

The back extraction of U, Pu and Np has not been achieved quantitatively.

-     Element    Feed                        Recovery %
-                ( ppm )             Raffinate       Ac/Ln          org. out
- Y              187                    1.2              98.8                0
- Sr              113                    100                0                0
-  Mo            568                   99.3                0.6           0.1
-  Zr               98                   100                  0                0
-  Tc              88                      0                    2              98
-  Ru            938                   92                    6              1.1
-  Pd           1014                  98.8                 0.9           0.3
- Cs            2915                  100                  0                0
-  La            937                    0                 99.9             0.1
-   Eu           131                  0.4                99.6             0.02
-        U             207                   0.1               3.5              96.4
-  Np           22                       2                  49              49
-  Pu            48                   3.5                  26              70.1
- Am          3570                0.005               99.7             0.3
- Cm           213                 0.01                99.9              0
- The back extraction of U, Pu and Np has not been achieved quantitatively.

## Separation of the actinides from the HLW(22)

- _Conclusions for DIAMEX_.
-   It is the more mature of the processes proposed in this European Program.
-  The separation problems of : Fe(III), Mo(VI), Zr(IV), Ru and Pd are solved.
-   The back extraction of Pu(IV) and U(VI)
-      These goals were not taken into account in the tests  already achieved ;  but as U(VI) and  Pu(IV) can be back extracted at acidity lower than 0.5N, no  difficulties are foreseen.
-   The behavior of Np and Tc . The importance of these problems depends of the PUREX process flow sheets used before the partitioning.
-      Gains for routing Np and Tc in the PUREX process could be used to solve these problems.
-  The solvent regeneration investigations just began and may be new problems will appear during the systematic operations which will include several recycles of the spent solvent.
**The demonstration of the possible use of DIAMEX for removing the actinides from the  HLC is the most recent  important step to make  the minor   actinide partitioning more economically acceptable.**

## Trivalent actinide-lanthanide group separation(1)

- For long time it was accepted that trivalent actinides and lanthanides form complexes  with very similar stability, the small differences being due to the small changes of their ionic radius.
- In the eighties it has been demonstrated that this assertion was only truth for the oxygen donors ligands  but not for the nitrogen or sulfur (less electronegative) donors with  which the actinides form stronger complexes.
-  It has been also shown that the affinity differences can be observed only in complexes in which the distance metal sulfur or nitrogen donor is the lower.
- This indicates that the origin of the group selectivity is the slightly stronger covalency,for the actinides.

## Trivalent actinide-lanthanide group separation (2)

- _Research of nitrogen and sulfur donors extractants suitable for process applications_.
- The separation of  the trivalent actinides - trivalent lanthanides will be performed after the Diamex process which yields a solution 0.5N in HNO**3** .
- Extractants which are able to extract selectively the actinides from this medium were researched.
-      Many lanthanides isotopes have large section capture for neutrons and the decontamination factors  of the actinide must be rather important.
- _Nitrogen donors: TPTZ and  substituted TPTZ_

## Trivalent actinide-lanthanide group separation (3)

- TPTZ is not able to extract Am(III) from nitrate solutions and it must be used with a lipophylic acid which can form a synergistic complex.
-      This is the case for the carboxylic acids.
- The pH of extraction decreases with the pK**a** of the acid. The general reaction for the extraction being:
- M**3+** + TPTZ+ 3 (RCOOH)**2 ** =>M(TPTZ)R**3**(RH)**3** + 3H+
- Many acids were investigated but most often C**9**H**18**BrCOOH
- The best results with the TPTZ family was obtained with the tris tertiobutyl TPTZ which did not show any aqueous solubility. Separation factors are close to 15 and HNO**3** around 0.15N can be used to carry out counter current separations.
-  Acidities as high as 0.5N cannot be used the D **Am(III)** becoming too low.

## Trivalent actinide-lanthanide group separation (4)

- _BTP (bis triazines pyridines) and  substituted BTP_
- These nitrogen donors were the surprise of the last years . They have the formula
-                                   H
-                                   
-                         H       C         H
-                            \    //    \     /
-          R                 C          C                   R
-             \                                          /
-              CN      C          C       N C                    pK**a**  BTP  <  pK**a** TPTZ
-             //        \\   /    \\      /     \   //         \\
-      RC           C         N         C            CR
-             \          /                         \            /
-             N  =  N                             N =  N
- - These ligands  are able to extract Am(III) and Cm(III) from 1N nitric acid as nitrates without the addition of a second acidic extractant and that for 10-2 M solutions

## Trivalent actinide-lanthanide group separation(5)

- The separation factors  SAm-Eu can be as high as 1000
-  The probable species in the organic phase are M(BTP)3(NO3)3
- Two molecules have been tested for the separation of the trivalent actinides - lanthanides coming from the  separation of the actinides of a genuine HLR treated by the Diamex process.

## Slide 33

## Trivalent actinide-lanthanide group separation(7)

- In spite of the high separation factors measured in tube tests (~1000) the process does not fulfill its promises.
-       Several factors contributes to the poor performances:
-   a) slow kinetics of extraction and back extraction.
-       The addition of DMDOEHMA in the organic phase accelerates the inter phase transfers.
-   b) rapid degradation of the extractant by hydrolysis and radiolysis and loss of extracting power.
-     The calculate results fit the experimental ones if the concentration of
-       n-PrBTP was 0.032M instead of 0.04M.
-  The two BTP tested cannot be used for applications  and other molecules are to day under investigation.
- The analysis by NMR of the hydrolytic degradation showed that the first attack on the molecule occurs on the CH**2** of the propyl groups which are rapidly transformed into CH.

## Trivalent actinide-lanthanide group separation(8)

- _Conclusion for the nitrogen donors_
-  Compared with the sulfur donors and more with the organophosphorus sulfur donors the nitrogen donors have the following advantages:
- complete incinerability
- degradation products, still unknown but chance to find non spurious products such as the oganophosphorus acids which are better extractants than the original organophosphorus sulfur donors( dithiophosphoric acid  => monothiophosphoric acid).
- So the trivalent actinide lanthanide group separation which is the second step of the partitioning is less advanced than the DIAMEX process, because less successful counter current separations have been performed.
- The very new and attractive properties of the BTP mobilized the research task forces to the detriment of the more classical TPTZ or other polypyridines ligands of which the chemistry and stability is better known.. For practical applications the BTP have two major drawbacks: slow kinetics of extraction and chemical and radiolytical instability.
- One BTP without these disadvantages is souhaitable and researched.

## Trivalent actinide-lanthanide group separation(9)

- _Selection of sulfur donors extractants_
-  Many ligands with sulfur as donor atom were tested for their extracting properties towards the trivalent f block elements group separation; but most were poorer extractants than  the bis(2-etylhexyl) dithio phosphoric acid , the first sulfur donor investigated in the eighties and able to separate the trivalent actinides from the lanthanides.
-  New thio organophosphorus molecules showed the more promising results.Two improvements were found:
- a) better chemical stability than the dithiophosphoric and dithiophosphinic acids
-         b) lower pKa. to extract Am(III) at lower pH and to be able to carry out the actinides- lanthanides group separation after the DIAMEX process back extraction which end up with 0.5N HNO**3** solutions.
- The molecule selected is :
-    ClH**4**C**6**     SH
-              \    /
-                 P                        di(chlorophenyl)dithiophosphinic acid) HDCPDTP
-          /   \ \
-     ClH**4**C**6**     S

## Trivalent actinide-lanthanide group separation(10)

-  _**Extraction  reactions**_
-  It has been shown that the actinide - lanthanide group separation is better achieved if  one oxygen donor organophosphorus neutral extractant is added to the organic phase.
- The extraction reaction of Am , Cm and the lanthanides into a mixture of HDCPDTP and TEHP (tris 2-ethylhexyl phosphate) has been  investigated
- The dimerization constant of HDCPDTP has been determined by 1H NMR and allowed to assert the role of the dimer and the monomer in the extraction reaction
- The number of DCPDTP- and TEHP in the organic complex were then obtained by slope analysis.
- Am(DCPDTP)3TEHP , Cm(DCPDTP)3TEHP
- M(DCPDTP)3(TEHP)2 for  La, Ce, Pr, Nd and Sm
- M(DCPDTP)3(TEHP)3  for Sm, Eu, Gd, Tb,Dy,Ho,Er, Yb and Lu

## Trivalent actinide-lanthanide group separation(11)

- That list shows a competition between the sulfur (DCTDTP-) and the oxygen donors (TEHP) depending of the metal.
- The stronger ionic interaction occurs with the heavier lanthanides.
- TheTEHP oxygen donors are able to push the DCPDTP-
- For the actinides the covalent interaction with the sulfur is stronger and only one TEHP can enter the inner coordination sphere.
-  The stronger sulfur - metal interaction for the actinides has been observed also in the _EXAFS spectra_ of the organic phases where the _signals intensity ratio_ _S=>M/O=>M_ are much stronger for Cm than for Eu.
-      So the EXAFS confirms the higher covalent interactions between the sulfur donors and the actinides.

## Trivalent actinide-lanthanide group separation(12)

- _Process applications for trivalent 5f-4f block elements separations._
- - A test designed for trivalent actinides lanthanides group separation has been carried out in a bank of 24 centrifugal contactors.
- The feed was a DIAMEX product simulated solution spiked with radioactive traces of actinides and lanthanides.
- The flow sheet and the composition of the fluxes are given on the block diagram below.

## Slide 40

## Trivalent actinide-lanthanide group separation(13)

- Am was correctly extracted 99.8% and back extracted.
- However in spite of very high Ac/Ln separation factors still 2% of the lanthanides remain into the Am solution. The scrub section was not efficient.
- 20% of the Cm was lost in the raffinate

## Am(III)-Cm(III) separations (1)

- Another interesting properties of the sulfur donors is the unusual high Am-Cm separation factors.
- With the synergistic mixture  0.4 M organophosphorus sulfur donor (DCPDTP) and 0.15 M TEHP in  the diluent 20%  isooctane - 80% t- butylbenzene. The Am-Cm separation factor varies from 13 to 6.5  as the HNO3 aqueous concentration increases  from 0.05 to 0.5N.
- These separation factor values are sufficient to achieved good separation in counter current processes and one attempt has been carried out .

## Am(III) –Cm(III) separation in mixer-settler batterry flow sheet

## Am(III)-Cm(III) separations (3)

- _Process applications for trivalent Am-Cm separation._
- The results are summarized in the table below and are compared with the expected quantities from calculations.
- Recovery yields               Am(III)                 Cm(III)
-    % of feed
- __________________________________________
- Raffinate                       0.05(0.13)              34.3 (93.6)
- Product                        99.8 (99.9)                4.75(6.39)
- Spent Solvent            0.154( 0.0033)      <det. (6.4x10**-6**)
- _____________________________________________
- The Cm(III) balance was very poor , only 39%

## Hydrolytic and radiolytic stability of  (Clphen)2PSSH

-   It has been found that the main degradation products of (Clphen)2PSSH are :
-            (Clphen)2PSOH and (Clphen)2POOH
- These two products are stronger extractants than   (Clphen)2PSSH and can not separate trivalent actinide from lanthanide.
- The hydrolytic stability of 0.5M (Clphen)2PSSH in toluene and in the presence of 2N HNO**3** , at room temperature,  can be seen on the following figure

## Slide 46

## Conclusions for the sulfur donors

- If  a process for actinide lanthanide group separation is possible with nitrogen donors,  the sulfur donors look less interesting from the point of view of radioactive waste coming from the solvent. Also, the extractant’s degradation products are unfavorable for the lanthanides back-extraction .They must be removed often.
- As for nitrogen donors the investigation of sulfur donors as actinide complexing agents brought a new view of the 5f block elements chemistry.
-  The high separation factors Am(III)-Ln(III) are (~104)remarkable, seen for the first time and are due to subtle phenomena in coordination chemistry.

## General conclusions

-  The goals of this work were to evaluate the possibility and the difficulty of actinides partitioning before transmutation as a nuclear waste management option.
-  The different options of waste management must be presented to the French Parliament in 2006 and if the state of experts opinion before and after this research for the chemistry of partitioning is compared one go from dubious to favorable because of the progress accomplished.
- The actinide-lanthanide group separations and the Am(III) - Cm(III) separations with soft donors ligands have not yet be demonstrated in continuous processes in spite of the extraordinary separation factors found in test tubes.
- For Am-Cm separation the possibility of Am(III) oxidation often proposed in the past is realistic.
- These  two later separations  are less costly than the actinides separations; because of the lower volumes of liquids involved.