Measurements of Ra Isotopes via MnO 2 Resin
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Measurements of Ra Isotopes via MnO2 Resin
Bill Burnett, Natasha DimovaFlorida State University
E. Philip HorwitzPG Research Foundation
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AcknowledgmentsFSU Graduate Students: Natasha Dimova Henrieta Dulaiova Ricky Peterson Benjamin Mwashote Christina StringerPGRF: Phil Horwitz Andy Bond Dan McAlster
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IsotopeIsotope DirectDirectParentParent
Half-Half-lifelife
Decay Decay ModeMode
EnergyEnergyMeVMeV
223223RaRa 227227ThTh 11.4 d11.4 d 5.615.615.725.72
224224RaRa 228228ThTh 3.66 d3.66 d 5.695.69226226RaRa 230230ThTh 1600 y1600 y 4.784.78228228RaRa 232232ThTh 5.75 y5.75 y 0.0460.046
Natural Radium Isotopes
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MnO2 ResinDeveloped by PGRFHigh adsorption of Ra, trivalent and
tetravalent actinides (Ac, Am, Pu, Th)Preconcentration approach in batch,
column, or pump (filtration) modes
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Adsorption vs. pH• pH = variable• Resin = 25 mg• Solution = 10
mL• Reaction time
= 90 min
The optimum pH for adsorption of Ra2+ is from 4 to 8 – nearly all natural waters fall into this range.
Moon et al. / Applied Radiation & Isotopes 59 (2003) 255-262
0 2 4 6 8 10 12 14
0
20
40
60
80
100
120
Ads
orpt
ion
Yiel
d of
133 B
a (%
)
pH
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KD Determination
WV
AAA
Kf
foD
Ao = initial activity solution, cpmAf = final activity solution, cpmV = volume solution, mLW = weight of resin, g
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KD and Kinetics, pH = 7
Floridan Aquifer groundwater ~40-200 mg/L (0.04-0.2 o/oo)
Moon et al. / Applied Radiation & Isotopes 59 (2003) 255-262
-20 0 20 40 60 80 100 120 140 160
200
400
600
800
1000
1200
pH=7,25mg MnO
2 resin
10 mL solution
133 Ba
Act
ivity
(CPM
-NaI
)
Time (min)
0.0 0.2 3.5 35.0
Kd=2.8x104
Salinity (‰)
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50
60
70
80
90
100
110
0 200 400 600 800 1000
Volume of Solution (mL)
% R
ecov
ery
1.0 g0.5 g0.1 g
Percent Recovery
lnsin
sin100covRe%soreD
reDVMK
MKery
KD = 2.8 x 104 mL/g
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Possible Analytical Uses1. Drinking water analysis of Ra-226
and Ra-228 via preconcentration and -spectrometry (well detector best)
2. Preconcentration of Ra isotopes and analysis of -emitters via -spect
3. Automated analysis of -emitting Ra isotopes via a radon-in-air analyzer
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Gamma-Spect Analysis
React MnO2 Resin in a batch mode, let settle, decant/ centrifuge, transfer to counting vial for -spect analysis
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Gamma Spectrum
226Ra peak 186 keV no U
via 214Pb + 214Bi 228Ra via 228Ac
226Ra186
214Bi609
228Ac911
228Ac338
214Pb295
214Pb352
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MDA Gamma Spect ~100-cc Ge well
detector 2-liter volume 295+352+609
keV assumes 50% equilibrium (4-day ingrowth)
volintensityeffT2.22TB4.66 2.71 (pCi/L)MDA
0
1
2
3
4
5
6
7
8
0 500 1000 1500 2000
Count Time (min)
MD
A (p
Ci/L
)
186 keV
338 keV
295+352+609 keV
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Alpha Spectrometric Analysis
2
1 2
Rinse 2M HCl1
2
DiphonixI
1
2
Load sample in 2M HCl
•Collect•Ba-133 yield•Hold >30 hrs.
Process Actinide Elements
Rinse 2M HCl1 M HEDPA
1
2
Load sample in 2M HCl
Elute 228Ac into plastic vial; add cocktail, count
via LSC
MnO2 Resin
Dissolve in 2 M HCl
Centrifuge
1
DiphonixII
3
3
1 2
ppt BaSO4133Ba yield
223,224,226Ra via-spectrometry
3
50-100 mesh7 cm; 0.7 mm id
100-200 mesh2.5 cm; 0.7 mm id
2
1 2
Rinse 2M HCl1
2
DiphonixI
1
2
Load sample in 2M HCl
•Collect•Ba-133 yield•Hold >30 hrs.
Process Actinide Elements
Rinse 2M HCl1 M HEDPA
11
22
Load sample in 2M HCl
Elute 228Ac into plastic vial; add cocktail, count
via LSC
MnO2 Resin
Dissolve in 2 M HCl
Centrifuge
1
DiphonixII
3
3
1 211 2
ppt BaSO4133Ba yield
223,224,226Ra via-spectrometry
3
50-100 mesh7 cm; 0.7 mm id
100-200 mesh2.5 cm; 0.7 mm id
Nour et al., in press
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Ra-226 via BaSO4 micro ppt
226Ra
222Rn 218Po 214Po
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-Spectrometry
S. Purkl, A. Eisenhauer / Applied Radiation and Isotopes 59 (2003) 245–254
Ra-224 + daughters Natural Ra isotopes and Ra-225 tracer
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Automated Measurements
inout (pump)
inner
outer
drying tube
RAD-7dryi
ng tu
be “DRYSTIK”
sample
0
2000
4000
6000
8000
2000 4000 6000 8000 10000
Energy (keV)
Cou
nts
218Po
214Po
0
2000
4000
6000
8000
2000 4000 6000 8000 10000
Energy (keV)
Cou
nts
218Po
214Po
A B
C= stopcockx
x
x
x
x
filter
moisture
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Gas Handling System
All the necessary tubing, valves, and drying system fits easily into a small cabinet
Front Back
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Loading the Sample
Fresh water samples can be processed either by gravity flow or by pumping at rates up to 300 mL/min without any loss of Ra.
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Connecting Sample to RAD-7
The sample, inside the same cartridge used for processing the sample, is hooked up to a radon-in-air analyzer.
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Validating Standard Ra Activity
Our standards are made by passing NIST-traceable Ra-226 solution standards through the MnO2 Resin. Any Ra remaining is measured by Rn emanation. Results confirm retention >96%.
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Setting Standard Ingrowth
The standards are re-set for ingrowth by passing helium through the cartridge to ensure no Rn-222 is present at t=0. A small amount of water is then added to enhance Rn emanation.
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Suggested Protocol1. Load sample on resin, measure Ra-
224, close stopcocks, allow ~5 days ingrowth for Ra-226
2. Attach to RAD-7 manifold, purge RAD-7, pump air through cartridge/RAD-7 for 5 minutes, close valves
3. Count for a few 15-min cycles for quick analysis (Po-218) or several hours for more sensitive analysis (Po-218 + Po-214)
4. Calculate results
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Results: Ra-224 Counting
Time (hours)0 100 200 300 400 500
224 R
a (c
pm)
0
2
4
6
8
10
y = 9.5 x e-0.00793x
t1/2 = 3.64 days
Water sample passed through MnO2 Resin and 220Rn counted periodically over many days produced the correct half-life for 224Ra.
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Results: Ra-226 (222Rn Ingrowth)
Several standards prepared with NIST 226Ra solution. Theoretical line drawn with decay constant for 222Rn.
Ingrowth (hrs.)0 50 100 150 200 250 300 350 400
cpm
0
50
100
150
200
250
300
y = 280(1-e-0.00752x)T1/2 = 3.84 days
ch A+C
ch A
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226Ra MDAs: Auto Counting1 liter 2
liters
MDAs calculated assuming 96% yield, typical blanks for A and C channels, and an equilibrium fraction of 0.5 (4 days ingrowth)
0
1
2
3
4
5
0 250 500 750 1000
Count Time (min)
MD
A (p
Ci/L
)
ch A
ch A+C
0
1
2
3
4
5
0 250 500 750 1000
Count Time (min)M
DA
(pC
i/L)
ch A
ch A+C
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Summary MnO2 Resin is an excellent adsorber
of Ra from natural waters May be used for preconcentration to
combine with traditional techniques (e.g., -spect, -spect)
Interfacing with a RAD-7 Radon analyzer allows determination of 224Ra and 226Ra without chemical separations