BUDAPEST UNIVERSITY OF TECHNOLOGY AND ECONOMICS
Faculty of Natural Sciences
Institute of Nuclear Techniques
Use of UTEVA for the separation of Th, U, Np and Pu
N. Vajda, Zs. Molnár, Sz. Osváth
EiChrom Users’ Group Meeting
7 June 2002
Address: H-1111 Budapest XI., Mûegyetem rakpart 9/11, R building, III/317.
Mailing address: H-1521 Budapest
Phone: (36-1)4632523, (36-1)4631254; Fax: (36-1)4631954
Major goals of separation
- nuclides to be analysed:237Np, 239,240Pu, 238Pu, 241Pu,
238
U, 235U, 234U, 232Th, 230Th, 228Th
SPECTROMETRIES
- simultaneous determination of Np & Pu & U & Th (& Am,Cm)
( and  emitting nuclides of U fuel cycle)
CHROMATOGRAPHY
- relatively simple separation scheme consuming less labour and time
than the traditional ion exchange procedures
EXTRACTION CHROMATOGRAPHY
- high sensitivity to measure environmental levels
HIGH SELECTIVITY
Why UTEVA? Why not other extractants of higher
distribution ratios?
UTEVA retains all the listed actinides.
The separation can be improved by the presence of iron.
Which loading and elution media?
Which oxidation states?
Which stripping sequence?
Basic steps of chromatographic separation
- retention of U&Th&Np&Pu on UTEVA from 8M HNO3
in presence of Fe(NO3)3 as "salting out" agent
- stripping of Pu(III) while tetravalent nuclides are retained -I-/9M HCl
- stripping of Th(IV) and Np(IV) - 4MHCl
- stripping of U in the absence of complexing agent - 0.1M HCl
Why Fe(NO3)3 as salting out agent?
Samples usually contain iron that
- is difficult to remove,
- can be utilized for preconcentration as Fe(OH)2
- is a good salting out agent.
2/15.
Basic steps of the combined analytical procedure
- simultaneous preconcentration of U&TRU by coprecipitation
- retention of U&Np&Pu&Th on UTEVA
followed by their sequential elution
- preconcentration and separation of Am&Cm using TRU
-  source preparation by micro coprecipitation
providing further purification of the sources
-  source preparation by dissolving the a source in LSC
-  spectrometry by means of isotope dilution technique
-  spectrometry using LSC
-  spectrometry to determine Np yield
3/15.
Studies about Np retention on UTEVA
Different oxidation states of Np were adjusted:
Np(IV) - iodide in HCl
Np(V) - NaNO2
Np(VI)- BrO3- or MnO4Np(IV-VI)- no adjustment
Models: equilibrium studies to determine Kd
kinetic studies
elution chromatographic studies to realize separations
4/15.
Determination of distribution coefficients
Retention of Np on UTEVA from nitric acid
contact time: 1 minute
Distribution coeffitient (1/g)
100,00
10,00
Np (IV-VI)
Np (IV-VI)+Fe
Np (VI)
Np (VI)+Fe
1,00
0,10
0
2
4
6
8
10
Nitric acid concentration (M)
Retention of Np on UTEVA from HCl
contact time: 1 minute
140
Distribution coeffitient (1/g)
120
100
80
60
40
20
0
0
2
4
6
8
10
Hydrochloric acid concentration (M)
5/15.
Higher distribution ratios can be achieved from HCl acid
but Np retention is suppressed by Fe complexes as it is
revealed by the kinetic studies.
Retention of Np on UTEVA from
9M HCl
1
0,9
Retained ratio of Np [-]
0,8
0,7
0,6
H: Np(IV-VI)
I:Np(IV-VI)
0,5
J: Np(IV)
0,4
0,3
0,2
0,1
0
0
50
100
150
200
250
300
Tim e[m in]
Retention of Np on UTEVA from
9M HCl in presence of FeCl 3
1
0,9
Retained ratio of Np [-]
0,8
0,7
0,6
K: Np(IV), Fe(II)
L:Np(V), Fe(III)
0,5
M: Np(IV-VI),Al
0,4
0,3
0,2
0,1
0
0
50
100
150
200
250
300
Tim e[m in]
It is likely that Np exists as tetravalent complex in 9M HCl.
6/15.
The retention of Np in all oxidation states is improved by
the presence of iron(III) nitrate salting out agent in 8M
HNO3. It is likely that Np prevails as penta and hexavalent
nuclide in concentrated nitric acid.
Retention of Np on UTEVA from
8M HNO3
1
0,9
Retained ratio of Np [-]
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0
0
50
100
150
200
250
300
A:Np(IV-VI)
B:Np(V)
Tim e [m in]
C:Np(VI)
Retention of Np on UTEVA from
8M HNO3 in presence of Fe(III)-nitrate
1
0,9
Retained ratio of Np [-]
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0
0
50
100
150
Tim e [m in]
200
250
300
F:Np(VI),Fe
E:Np(V),Fe
D:Np(IV-VI),Fe
7/15.
Elution chromatographic studies
Columns were prepared from 0,5g of soaked UTEVA,
column length was 34 mm.
Elution sequence:
1st load
2nd elution: with the same solution as during loading
3rd elution: 8 M HNO3 and/or 9M HCl
4th Pu strip: 0.1M NH4I/9M HCl
5th Np/Th strip: 4M HCl
6th U strip: 0.1M HCl
Separations in 9M HCl
Only possible if no Fe is present in the load solution.
In this case, Np probably as Np(IV) is well separated from
the matrix and other actinides except Th.
To determine the mechanism of the process tests were
performed from the same load solution paralell with anion
exchange resin (Bio Rad AG 1x8) column of the same size. It
was supposed that only tetravalent Np is retained on the ion
exchanger.
8/15.
Retention of Np on UTEVA
from HCl
1,20
1,00
% eluted
0,80
0,60
0,40
0,20
0,00
1 load
2 elution
3 elution
4 Np strip
5 Np strip
6 U strip
7 U strip
UTEVA
Fraction
Retention of Np on anion exchange resin
from HCl
1,20
0,80
0,60
0,40
0,20
resin
7 U strip
6 U strip
5 Np strip
4 Np strip
3 elution
2 elution
0,00
1 load
% eluted
1,00
Fraction
9/15.
Separation of actinides from HCl can be performed in
special samples of low Fe content:
e.g. separation and analysis of actinides from irradiated
uranium
Separation of actinides on UTEVA
load and eluent: 9M HCl,
Pu strip: 0.1 M NH4I/9M HCl,
Np strip: 4M HCl, U strip:0.1M HCl
1
0,9
0,7
0,6
0,5
0,4
232U
0,3
239Np
0,2
0,1
239,240Pu
Isotope
6 U strip
5 Np strip
228Th
4 Pu strip
2-3 eluent
0
1 load
Eluted ratio
0,8
Eluent fractions
10/15.
Separations in 8M nitric acid
Without oxidation state adjustment Np exists in different
forms, appearing in 2 elution peaks in the chromatogram:
Retention of Np(IV-VI) on UTEVA from 8M HNO 3/Fe
without oxidation state adjustment
0,350
0,300
0,200
0,150
0,100
0,050
7 U strip
7 U strip
6 Np strip
5 Np strip
4 Pu strip
4 Pu strip
4 Pu strip
3 elution
2 elution
2 elution
2 elution
0,000
1 load
% eluted
0,250
Fraction
11/15.
Hexavalent Np is prepared by boiling with KBrO3 or
KMnO4 in 1M HNO3
Pentavalent Np is prepared by the addition of NaNO2.
To study the retention mechanism aliquots of the load
solution were passed through UTEVA and Bio Rad AG 1*8
columns.
Retention of Np on UTEVA from
8M HNO3/Fe/NO2-
100,00%
90,00%
80,00%
% eluted
70,00%
60,00%
50,00%
40,00%
30,00%
20,00%
10,00%
10 UTEVA
9 U strip
8 U strip
7 Np strip
6 Np strip
5 Pu strip
4 Pu strip
3 elution
2 elution
1 load
0,00%
Fraction
Retention of Np on anion exchange resin
from 8M HNO3/Fe/NO250,00%
30,00%
20,00%
10,00%
10 resin
9 U strip
8 U strip
7 Np strip
6 Np strip
5 Pu strip
4 Pu strip
3 elution
2 elution
0,00%
1 load
% eluted
40,00%
Fraction
12/15.
Np is retained by the UTEVA as pentavalent and
hexavalent complexes while tetravalent is preferred by the
anion exchangers.
The behaviour of Pu, U and Np was tested under the same
conditions as that of Np.
100 ml of load solutions were prepared supposing that
samples cannot be dissolved in small amounts of solutions.
Pu, Th/Np and U strip solutions were analysed for all
nuclides by preparing alpha sources -under reductive
conditions- using NdF3 for micro-coprecipitation.
Actinide separation on UTEVA from 8M HNO3/Fe3+/NO2-
100
90
80
60
50
40
30
20
10
U
0
Nuclide
U strip 5 ml
15
Pu
Pu strip 15 ml
13
eluate 10 ml
11
Th
load 10 ml
9
load 10 ml
7
load 10 ml
5
Np
load 10 ml
3
load 10 ml
1
% eluted
70
Fraction
13/15.
Flow chart of the procedure
Sample: soil,sediment,water, radioactive waste
Tracers:232U-228U,236Pu,243Am-239Np
Acid destruction:HNO3,HF,HCl
Dissolution:1M HNO3+H3BO3
Filtration
Fe(OH)2 coprecipitation
Dissolution: 1M HNO3
Adjustments:
- oxid.state: KBrO3 or NaNO2
- acidity: 8M HNO3
-salting out: Fe(NO3)3
UTEVA
extraction chromatography
effluent
Pu strip
Am+Cm separation:  source
Ca oxalate
preparation:
TRU
Pu/NdF3
 spectrometry
TEVA
 source
 source
preparation:
Pu/LSC
LSC
Th,Np strip
U strip
oxidation
 source
preparation:
Th/NdF3
 spectrometry
 source
preparation:
U/NdF3
 spectrometry
 source
preparation:
Np/NdF3
 spectrometry
14/15.
Analysis of standard reference materials
Modelling environmental samples
Unfortunatelly, there are no SRMs for 237Np.
Radionuclide
239,240
238
Pu
Pu
238
U
234
U
237
Np
Measured value
"Reference value"
Yield Act.conc.

Confidence interval
%
Bq/kg
Bq/kg
Bq/kg
IAEA-135: sediment from Sellafield *
69
189,8
3,3
205-225.8
44,2
1,6
41.6-45
66
18,95
0,67
27-36.5
17,11
0,62
20.9-32
80
0,32
0,07
0,883
IAEA-368: sediment from Mururoa *
239,240
Pu
92
28,59
0,44
29-34
238
Pu
8,35
0,33
7.6-8.9
238
U
58
27,7
0,57
25-33
234
U
32,7
0,63
21.5-44.8
237
Np
100
<0.58
0,013
IAEA-384: sediment from Fangataufa
239,240
Pu
52
94,4
6,2
105,4-108,9
238
Pu
33,8
3
38,1-39,6
238
U
61
31,52
1,4
31,41-33,33
234
U
30,25
1,3
34,2-43,5
*valence state adjustment with bromate
**valence state adjustment with nitrite
Bold values: reference value; others: information ones
15/15.