Transcript Radioanalytical Chemistry in Emergency Preparedness

Determination of actinides in emergency
preparedness using Diphonix or Actinide resin
in combination with gamma spectrometry
Ulrika Nygren and Daniela Stricklin
Ulrika Nygren, June 2002
Emergency Preparedness
• To protect the Swedish population from exposure to
ionising radiation produced in the decay of
radioactive nuclides
– Fallout from nuclear power plant accidents
– Fallout from nuclear weapons explosions
– Terrorism
• Designated laboratory for the Swedish Radiation
Protection Authority (SSI)
Ulrika Nygren, June 2002
Transfer of radioactive debris to the environment
radioactive cloud
Radioactive Cloud
inhalation
inhalation
drydeposition
deposition
dry
wet
wet
deposition
deposition
transfer:
transfer:
vegetationtoto
vegetation
forest
floor
forest
floor
uptake
rootroot
uptake
reindeer
plant
plant
production
production
reindeer
animal
animal
production
fish
production
external
radiation
fish
external
radiation
migration
migration
Fast determination of fall-out composition critical
Ulrika Nygren, June 2002
Mobile Measurement Techniques
Primarily determination of
deposited gamma emitting
fission products – actinides and
pure beta emitters not determined
Measurement
Vehicle
HPGe, NaI for
thyroid
measurements
Backpack
NaI-detector,
GPS
Fieldgamma
Spectrometry
HPGe
Ulrika Nygren, June 2002
Standard radioanalytical procedure for actinide determination at FOI
- identification of time consuming procedures
Dry, homogenise
Soil
LiB-fusion
Water
Wet ashing
Vegetation
Si-removal
Oxalate precipitation
UTEVA
U
TRU
Pu
Electrodep. and
α-spectrometry
Am (Cm)
Ulrika Nygren, June 2002
Determination of actinides by the use of actinide
specific resins and low-energy gamma spectrometry
– fast preconcentration and partial separation of the
actinides
– good spectral resolution provides qualitative and
quantitative information
– geometry well suited for gamma spectrometry,
facilitates calibration
Issues?
– sensitivity
– retention of actinides on resin
Ulrika Nygren, June 2002
Analytical procedure – emergency preparedness
LiB-fusion
soil
1100°C, 10 min
5% HNO3, 20 min
water
Microwave digestion
HNO3 and H2O2, 15 min
vegetation
Adjustment of acid
concentration
Surry with resin
0.7 g, 1 h.
Low-energy
γ-spectrometry
Digestion of
extractant
Extraction
chromatography
Elektrodep. and
α-spectrometry
Ulrika Nygren, June 2002
Retention of nuclides from rainwater on
Actinide resin
No Acid
pH 1.5
5% Nitric Acid
100
80
60
40
20
0
Am-241
Cd-109
Co-57
Ce-139
Sn-113
Sr-85
Cs-137
Mn-54
Y-88
Zn-65
Co-60
Ulrika Nygren, June 2002
Retention of nuclides from rainwater on
Diphonix
No Acid
pH 1.5
5% Nitric Acid
100
80
60
40
20
0
Am-241
Cd-109
Co-57
Ce-139
Sn-113
Sr-85
Cs-137
Mn-54
Y-88
Zn-65
Co-60
Ulrika Nygren, June 2002
Retention of nuclides from vegetation on
Actinide resin
100
99.24
5% Nitric Acid
79.02
% Retention
80
75.48
74.63
60
40
20
2.57
6.78
0.19
4.73
0.12
0.31
0.14
Zn-65
Co-60
0
Am-241 Cd-109
Co-57
Ce-139 Sn-113
Sr-85
Cs-137
Mn-54
Y-88
Ulrika Nygren, June 2002
Separation of 241Am from soil
The sample-solutions were adjusted to
1M HF and 0.125M AA prior to the
addition of the resins
100
97.40
91.50
% Retention
80
95.81
71.76
2.5% Nitric Acid
60
5% Nitric Acid
40
20
0
Actinide Resin
Diphonix
Ulrika Nygren, June 2002
Detection limits for
241Am
Minimum detectable
activity concentration
Sample
amount
Limiting Activity
2
Concentration
Rainwater (Bq / l)
0.6
200 ml
3.7x10
Vegetation (Bq / kg)
65
2g
3.7x105
Soil (Bq / kg)
130
1g
1.3x10
5
4
1
Based on 100 min counting time and 95% conf. interval according to L. A. Currie, Anal. Chem.,
40 (1968)
N. Green, ”An evaluation of rapid methods of radionuclide analysis for use in the aftermath of
an accident”, Sci. Total Environ., 130/131 (1993)
2
Ulrika Nygren, June 2002
Time of analysis
Total analysis time for 1 sample (h)
Conventional
Lowenergy-
method
methods1
24
3
24
3.5
24
4
Rainwater
Vegetation
Soil
Total analysis time for 6 samples
Conventional
Lowenergy-
method
methods1
29
11
31
11.5
34
12
The analysis times are based on a counting time of 100 min
1
N. Green, G. Ham, S. Shaw, Rapid Radioactivity Measurements in Emergency and
Routine Situations, Proceedings, NPL, Teddington, UK, (1997)
Ulrika Nygren, June 2002
Theoretical detection limits for other actinides
- complete retention on resin assumed
Nuclide
Energy
Intensity
Theoretical Detection Limits
(keV)
%
Water (Bq/l)
Grass (Bq/kg)
Soil (Bq/kg)
234U
53.1
10.4
1.5
150
300
235U
185.7
54
0.44
44
88
238U
48.0
0.075
210
21000
43000
239Np
103.7
24
0.7
70
140
237Np
86.5
13.1
1.5
150
290
241Am
59.5
36.3
0.65
65
130
238Pu
43.5
0.038
410
41000
83000
239Pu
51.6
0.021
820
82000
160000
240Pu
45.2
0.045
350
35000
71000
241Pu
98.4
0.0022
7500
750000
1500000
242Cm
44.0
0.033
490
49000
99000
244Cm
42.8
0.025
610
61000
120000
Based on 100 min counting time and 95% conf. interval according to L. A. Currie, Anal. Chem., 40 (1968)
Ulrika Nygren, June 2002
Destruction of resin/extractant for further separation
and analysis
•
•
•
•
Actinide resin
Removal of extractant with
actinides from resin by
isopropanol
Evaporation till dryness in
Ni-crucible
Fusion with Na2O2 (550ºC,
10 min)
Leaching of melt by H2O
followed by dilute HNO3
•
•
•
•
Diphonix
30 ml HNO3 (conc.) added
to resin and evaporated to
near dryness at 200ºC
10 ml H2O2, ev. to near
dryness
15 ml H2O2 and 0.35 g
FeSO4*7H2O, ev. to near
dryness
6 ml H2O2, ev. to dryness
Ulrika Nygren, June 2002
Chemical yields in alpha spectrometric analysis
Destruction of extractant:
•Fentons reagent for Diphonix
100
•Na2O2 fusion for Actinide
resin
90
80
70
yield (%)
60
Diphonix
50
Actinide resin
40
30
20
10
0
U
Pu
Am
Ulrika Nygren, June 2002
Determination of actinides by the use of actinidespecific resins and low-energy gamma spectrometryConclusions
• The method shows good capacity for the separation and determination of
241Am in water, vegetation and soil
• Analysis time is dramatically reduced compared to conventional methods
• The method provides sufficient sensitivity for the determination of
several actinide-nuclides in emergency preparedness
• The retention of 241Am is good on both resins, although the Actinide
resin is somewhat more selective and provides higher retention at higher
acid concentrations
• Possible to process resins for further analysis based on e.g. alpha
spectrometry
D. L. Stricklin, Å. Tjärnhage, U. Nygren, J. Radioanal. Nucl. Chem., 251 (2002) 69
Ulrika Nygren, June 2002