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Measurements of Ra Isotopes via MnO 2 Resin. Bill Burnett, Natasha Dimova Florida State University E. Philip Horwitz PG Research Foundation. FSU Graduate Students : Natasha Dimova Henrieta Dulaiova Ricky Peterson Benjamin Mwashote Christina Stringer. PGRF : Phil Horwitz Andy Bond - PowerPoint PPT Presentation
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Measurements of Ra Isotopes via MnO2 Resin
Bill Burnett, Natasha DimovaFlorida State University
E. Philip HorwitzPG Research Foundation
AcknowledgmentsFSU Graduate Students: Natasha Dimova Henrieta Dulaiova Ricky Peterson Benjamin Mwashote Christina StringerPGRF: Phil Horwitz Andy Bond Dan McAlster
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
MnO2 ResinDeveloped by PGRFHigh adsorption of Ra, trivalent and
tetravalent actinides (Ac, Am, Pu, Th)Preconcentration approach in batch,
column, or pump (filtration) modes
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
KD Determination
WV
AAA
Kf
foD
Ao = initial activity solution, cpmAf = final activity solution, cpmV = volume solution, mLW = weight of resin, g
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 (‰)
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
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
Gamma-Spect Analysis
React MnO2 Resin in a batch mode, let settle, decant/ centrifuge, transfer to counting vial for -spect analysis
Gamma Spectrum
226Ra peak 186 keV no U
via 214Pb + 214Bi 228Ra via 228Ac
226Ra186
214Bi609
228Ac911
228Ac338
214Pb295
214Pb352
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
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
Ra-226 via BaSO4 micro ppt
226Ra
222Rn 218Po 214Po
-Spectrometry
S. Purkl, A. Eisenhauer / Applied Radiation and Isotopes 59 (2003) 245–254
Ra-224 + daughters Natural Ra isotopes and Ra-225 tracer
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
Gas Handling System
All the necessary tubing, valves, and drying system fits easily into a small cabinet
Front Back
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.
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.
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%.
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.
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
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.
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
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
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