EG9601822

DETERMINATION OF URANIUM IN INDUSTRIAL AND ENVIRONMENTAL SAMPLES

F.H.EL-SWEIFY', M.K.SHEHATA, E.M.METWALLY, EA.A.EI-SHAZLYAND H.A.EL-NAGGAR

Nuclear Chemistry Department, Hot. Laboratory CenterAtomic Energy Authority, Post Code 13759, Cairo, Egypt

BS IRAQI

The phosphate ores used in "Abu Zaabal Fertilizer and Chemical Company" for the

production of some chemicals and fertilizers contain detectable amount of uranium. In this

study the content of uranium in samples of different products of fertilizers, gypsum and

phosphate ore has been determined using NAA and gamma ray spectroscopy of the

irradiated samples. Another method based on measuring the natural radioactivity of 238U

series for non-irradiated samples using f ^ y spectroscopy has been also used for

determining the uranium content in the mentioned samples. In the NAA method the

content of U (ppm) in the samples has been computed from the photopeak activity of the

lines : 106.1, 228.2 and 277.5 KeV of 23SNp induced in the irradiated samples and the

simultaneously irradiated uranium standard. The y-ray spectra and the decay curves are

given. In the second method the -p-ray spectra of the natural radioactivity of the samples

and uranium standard have been measured. The y-transition of energies 295.1, 351.9

KeV for 214Pb; 609.3, 768.4, 1120.3, 1238.1 KeV for 214Bi were used to determine 238U.

The uranium traces in drainage water has been also determined spectrophotometrically

using arsenazo-lll after preconcentration of uranium from the pretreated drainage water

in column packed with Chelex-100 resin. The recovery is found to be 90±5% .

12

INTRODUCTION

Traces of uranium could be determined without chemical treatment by y -spectroscopy.

The determination could also carried out after preconcentration and separation using

different chemical techniques followed by spectrophotometric determination using oftently

arsenazo-lll. Thus , traces of uranium and thorium were determined as impurities (30 ppm

and 300 ppm respectively) in tungsten by radiochemical neutron activation analysis.

The content of each element was calculated by a single comparator method after peak

identification and activity determination1. Uranium was determined in phosphate rock and

technical phosphoric acid radiometrically using y-counting and spectrophotometrically

using arsenazo-l after separation and preconcentration using solvent extraction and ion

exchange2. In samples of tiles , Uranium was analyzed by gamma spectrometry and in

addition spectrophotometrically using arsenazo-lll after separation3. Arsenazo-lll was also

used to determine uranium traces in the range of 0.2 to 10 (ppm) in Zircaloy-4 and

Zirconium sponge after separation using partition chromatography4, in phosphogypsum

after separation by solvent extraction5, in phosphate fertilizers after extraction with trioctyl

phosphine oxide*, and natural water after preconcentration on triethylaminoethyl (TEAE)

cellulose7.

EXPERIMENTAL

Natural ^-activity measurements: For Y-spectroscopic analysis of the natural radioactivity

, the samples were weighed (6.7 g) individually as well as uranium standards with known

uranium content. These standards were IEAE No.S-12, No.S-13, No.S-8, No.S-7 contain

0.014% , 0.039%, 0.14% and 0.527% of U3O8 respectively and standard NBL No. 5 of

0.11% U3O9. The samples and standards were transferred to very clean glass bottles

(20 ml capacity) . Each sample was weighed and carefully sealed for four weeks to

assure reaching secular equilibrium in the 238U decay series. The activity of 214Bi and

13

214Pb in equilibrium with their parents is assumed to represent the 23aU activity(8'10). y-

spectra for the different samples were measured using a hyperpure germanium detector

connected to a high resolution 8192 multichannel analyzer. The accumulation time for

each sample was 4 h, except for the standard curve it was 1000 Sec. The detector has

an energy resolution of 2.1243 KeV FWHM for the 1332 KeV gamma transition of *°Co.

The detector was shielded by a cylindrical lead shield with a moving cover to reduce

gamma ray background. The gamma transitions of energies 295.1, 351.9, 241.9 KeV for2UPb, 609.3, 768.4 and 1120.3 for 214Bi were used to detect and determine 23aU. The

corresponding percent intensities of these transition are 19.2, 37.1, 7.5, 46.1, 4.9 and 15

% respectively.

Irradiation; Duplicate samples of the different products of fertilizers, gypsum and

phosphate ore as well as uranium standard IEAE No.S-12 (0.014 % U3Oa i.e 118.72 ppm

U) each weighing 0.01 g were packed in thin aluminum foil and irradiated in a neutron flux

of 1012 - 1013 n.Cm'2.Sec'\ for 48h in the E-RR-1 at Inshas. After Irradiation, samples

were left to cool for about 48h. y-Spectra for the irradiated samples and uranium

standard were then measured using the same gamma ray spectrometer. The gamma

transition of energies 106.1, 228.2 and 277.5 KeV of 239Np were used to measure uranium

content in each sample.

Preconcentration of uranium in AZFC drainage water; Samples of the drainage water

of the (AZFC) each of 100 ml volume were filtered and its slight acidity (PH=2) was

neutralized with adding NajCOa 0.1 M till the pH of the solution was 8.5M. The solution

was then filtered again and completed to 1 liter with distilled water. The pretreated

solution was allowed to pass through glass columns filtered with centered glass at the

bottom. Two Kinds of column were us©d with different internal diameter 4^0.5 and 1.1

Cm. The column were packed with 0.5 or 2.0 g quantity respectively of Chelex-100 Na+

form (50-100 mesh). The columns were pretreated with 10'3M Na2Co3. The sample of

the pretreated drainage water was then allowed to pass through the column in flow rate

of 1 ml.minVCm2. The eiution was carried out using solutions of 1.2N HCI.

Spectrophotometric? determination of uranium using arsnazo-lll : The uranium content in

the eluted solution was determined spectrophotometrically using arsenazo-lll. For this

purpose standard curve was constructed. Aliquots of uranium standard solution

containing not more than 20 Ug uranium were placed in a measuring flask of 10 ml

capacity. 1 ml of 0.1 % arsenazo-lll and 0.2 ml of 103 M EDTA (for masking interfering

ions if present) solutions were add followed by pH adjustment to 2-3 with diluted HNO3

or HCI. The flask was then completed to 10 ml with distilled water shaken well and left

for 10 minutes for colourd development. The absorbance was then measured against

blank solution containing all constituents except uranium at the wave length 654 nm11.

The eluate samples were treated as in case of the standard solutions. The measurement

were carried out using spectrophotometer Shimadzu-UV-120-20.

Recovery Determination: Solutions of known uranium content 650 Ug were pretreated

as in case of the drainage water samples and allowed to pass through column of internal

diameter 4^1.1 Cm packed with 2g Chelex-100 at flow rate 1 ml.min'1. Cm"2. Uranium was

then eluted with 1.2N HCI and its contents in the effluent was determined. The percent

recovery was then calculated

RESULTS

The Y-Spectra for the natural radioactivity of the analyzed samples as well as the

uranium standard are shown \n figs.(1-5 a,b) where figs.(a) give the full y-Spectra and

figs.(b) give the expanded spectrum for regions of interest. From these spectra the area

under peak of the desired energies for the analyzed samples were computed and

compared with that of uranium standard. The uranium content in each sample is

r i

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Fig.(1) y-Spectrum for Back Ground of the Natural Radioactivity,

a) Full Spectrum, b) Expanded Spectrum for Region of Interest.

16

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fttjiE^r- 1 ^ l:-i K" (»l.'lff;;_ift 5 »l (IfP

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(b)

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Fig.(2) y-Spectrum for Natural Radioactivity of Standard UraniumIAEA No.S-12 0.014% U3Oa

a) Full Spectrum, b) Expanded Spectrum for Region of Interest.

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11+

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(b)

rvj

mo>

(a)

Fig.(3) y-Spectrum for Natural Radioactivity of Phosphate Ore.

a) Full Spectrum, b) Expanded Spectrum for Region of Interest.

18

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•̂: J

•I ' i." I

• • ,

: ' • ' : : '

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•'. :> ̂ rl •"• :"•:» C T u ; | f : •

(b)

(a)

Fig.(4) y-Spectnim for Natural Radioactivity of SSP.

a) Full Spectrum, b) Expanded Spectrum for Region of Interest.

19

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Fig.(5) Y-Spectmm for Natural Radioactivity of GSSP.

a) Full Spectrum b) Expanded Spectrum for Reaion of Interest,

2 0

computed using the following equation:

U(ppm) in standard

U (ppm) » - _ — _ - _ — _ X

Where A=Photopeak activity of 214Pb or 2UBi Y-lines in the sample and As is that of the

uranium standard. The results are shown in table (1).

To assure the accuracy of the measurements using this method, different uranium

standards were used and their Y-spectra were measured for fixed time periods (1000

Sec). These standards were IEAE No.S-12, No.S-13, No.S-8, No.S-7 and NBL No.5

cornatite contain the following percent of U3O9 : 0.014%, 0.039%, 0.14%, 0.527% and

0.110% respectively. The net area under the peaks 351.9 and 609.3 (KeV)i.e the peaks

of the highest intensities of 214Pb and 21iBi were computed and drown against the uranium

content (ppm). Fig.(6) reprsents the relationship between the area under peak and the

uranium content (ppm). The straight lines in this figure assure the accuracy of the

measurements.

The y-Spectra of the irradiated uranium standard and the analyzed samples are shown

in figs. (7-11 a.b.c.) Also here figs.(a) give the full t-spectra, figs.(b) give the expanded

spectra of region of interest. The area under the peaks 106.1, 228.2 and 277.6 (keV) for

the analyzed samples were computed and compared with the areas under the same

peaks of irradiated uranium standard , from which the uranium content in the analyzed

samples (ppm) was calculated using the previous equation. The results are summarized

in table (2).

21

Table(1): y-Transition Energies of 23eNp, The Net Area Under Peak Measured AfterDifferent Cooling Times and % of Error for Irradiated Uranium Standard and the AnalyzedSamples.

Sample

IAEAUraniumStandardNo.S-12

Phosphate

Ore

GSSP

SSP

Gypsum

Intensity

CoolingTime

7d.

9d.

13 d.

7d.

9d.

13 d.

7d.

9d.

13 d.

7 6.

9d.

13 d.

7d.

9d.

13 d.

Energy

106.1 Kev22.7

NetArea

37503

23553

7884

22566

14055

5215

18279

9019

2725

15196

7997

5235

3594

3004

1422

%Error

0.95

1.25

2.33

1.79

2.59

5.69

1.51

2.84

6.69

1.95

3.51

5.03

5.25

4.78

9.68

228.2 Kev10.7

NetArea

34681

22293

7614

22280

13837

3627

14472

8567

1673

13549

7864

3602

1266

—

592

%Error

0.76

0.96

2.01

1.33

1.77

5.07

1.46

2.32

6.57

1.59

2.38

4.73 ,

4.5

—

14.41

277.6 Kev14.2

NetArea

29235

18919

4706

18436

10949

2530

12037

7254

1405

11742

6371

2718

1816

1023

...

%Error

0.82

1.05

2.91

1.36

1.9

5.7

1.53

2.08

6.85

1.50

2.5

5.35

6.39

9.4

—

22

2 0 0 0

1500

1000

500

n

Net

-

Area

• 352.4

i

KeV

• /

+ 609.3 KeV .

yi ( i

0 1 2 3 4

U (ppm) Thousands

Fig.(6):Standard Curve for Determination of Uranium ContentUsing 2uPb and 21*Bi Transrtion Energies

352.4 and 609.3 KeV. Respectively.

The measurements were carried out after different cooling times where decay curves

were constructed for the three gamma transitions 106.1, 228.2 and 277.6 (KeV)of 239Np

induced in each sample via the nuclear reaction.

238U (n,Y) 239U - 239Np

T ia=23.5 m

All straight lines \n the decay curves flgs.(7-11)C give half life of 2.35 day corresponding

to 239Np which reveal the presence of uranium in the irradiated samples. Detection of

uranium using NAA was adopted in previous work12.

Preconcentration and determination of traces of uranium in the AZFC drainage water

was efficiently carried out. The method is based on the preconcentration of uranium on

a column packed with Chelex-100 from dilute solutions of NajCC^ (10'3M) and then

elution of uranium from the column with 1.2N HCI. After pretreating of the drainage water

with Ns^CC^ tell pH 8.5, the precipitations of hydroxides and basic carbonates of other

ions were removed by filtration. Under these conditions, uranium is present as soluble

anionic carbonate complexes13. In previous work14, uranium was found to be highly

adsorbed on Chelex-100 from dilute solutions of Na2CO3 (10 3M). This could be attributed

to the higher ability of the functional groups of Chelex-100 (iminodiacetic acid) to complex

uranyl ions than CO32' groups in dilute solutions15. Accordingly, uranium is selectively and

highly retained by the resin. Th© uranium in the drainage water determined by this

method is found to be 0.205 (ppm). This value is the average of four values. The

percent recovery of uranium is found to be 90±5%. The recovery percent is determined

by determing the uranium content in different effluents eluted from the column after

preconcentration from Ne^CC^ solutions (table 3),

* •

1

1 : -

" " !t !•

* * * * *

r î

; \COLO?

.y;if-.:

o

r:

;:iJ :

239Np

ru

coC\J

ru

( b )

CVJ

(a)

rH-; j i ; i i ) l ! 'J-: i i ' î t r t - I

; ; i ; , : . QHHH;77-$2 HE1

mo

aol-

(C)

Rg-(7) y-Spectaim for irradiated Standard Uranium ÎAEA No.S-120.014% U3O8 and Decay Curve for 239Np

a) Full Spectrum, b) Expanded Spectrum for Region of Interest,

c) Decay Curve.

noON

00 vr\

ooCb)

""'i

•yiik?

.a)

•fi—JU—lii?tiW-\ ' i f !MFE.-c: f ••-

'Iff •)'»!l;:l:-!i!'P£>1 H ( H C H * I

Fig.(fl) f-Speclai?n for .Irradiated Phosphate Ore and Decay Curve for 239Np

a) Full Spectrum, b) Expanded Spectrum for Region of Interest,

c) Decay Curve

(c)

•2

Flhi yij

• ; • '

' . " • H O

r i

r 1M L M

- r

R 0 î

f"Tr Si! r

F2EPH-;E

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nor-i

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COLOf:

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11

1

«ni

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|

230.

LA

(b)

(a)

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•â

12 r

3 :-

•0#.t

Rg.(9) y-Spectrum for Irradiated SSP and Decay Curve fo r ^Np

a) Fui! Spectrum, b) Expanded Spectrum for Region of Interest,

c) Decay Curve.

(c)

a Q -2 i4

oo

1-1

Ai ylJ

i . -

} • ;

i ' • • l ' i l Ie"

! r"-1

:.:>'iio

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?"TPHH":-

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:ETUF-

:" j :__ : i p

.- ' t* i

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'•îîi 'F' :

(01 Of.

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f! I)mi

i

II

is E H : " G r :̂ - ::i v 0 : ! HT:- AHHITTIX7;

l i l t ••t.il

( b )

(a )•C«.'.

• r~.#

(O

3 ' 3 -2

Rg.(1O) T-Spectrum for Irradiated GSSP and Decay Curve for230!

a) Fui! Spectrum, b) Expanded Spectrum for Region of Interest,

c) Decay curve.

ro

F!Hl'.ÛIJ

r "•r ;.

r-

Ï?.HH:-

K- ••'.•

PO i

F;

E::FH['

E.KH:-E

'EÜ.I?

O'.'LnF"

c,'( j- ;

: ; j . :

: : : ; • : •

'lOLOr"

03O

233Np

coOJ

( b )

(a)

•••• : •;:• " . î

f uii . -HijT-.

% HHHHr i r\\

«l iHlr: : ' :

fHHI'r• ' < . '

H 1.1 H H t i l l ^ r i i , . f i , : : . . 1 ^ . . : - . " , : ! ^ •}•}-::-

Oûû,

ÏQQQ^

2000

* <04.i

(c)

Q • 2 4. e a -a :2 -4.

Fig.(11) Y-Spectmm for irradiated Gypsum aod Decay Curve.for

a) Full Spectrum, b) Expanded-Spectrum for Region of Interest

c) Decay Curve.

239»

Table (2): -y-transition Energy of 214Pb;214Bi, the Net Area Under Peak and % of Error forUranium Standard and the Analysed Samples.

E (Kev)% Intensity

Sample

IAEAUraniumStandardNo.S-12

PhosphateOre

GSSP

SSP

NetArea

% Error

NetArea

% Error

NetArea

% Error

NetArea

% Error

295.119.2

752

6.77

417

9.26

300

14.83

227

15.28

351.937.1

1375

3.69

750

5.88

491

7.47

440

7.64

609.346.1

792

4.95

490

7.86

315

11.94

317

9.39

30

Table(3): Uranium Content in Different Effluent Eluted with HCI 1.2N from Chelex-100Column After preconcentration from Solutions of ^

Effluent No.

1

2

3

4

Volume (ml)

5

5

5

5

UraniumContent(ug/ml)

46.8

54

9.9

6.3

UraniumTotal Content

(ug)

234

270

49.5

31.5

%Recovery

36

41.54

7.62

4.85

Column 2Cm Length, 1.1 Cm Diameter, Flow rate 1 ml.Min~\Cm"2, Initial Uraniumcontent • 650 ug

31

DISCUSSION AND CONCLUSION

Data on the detection and determination of uranium in the collected samples is

obtained either by y-radiometric assay for the natural radioactivity of 23aU decay products,214Pb and 214Bi or for the y-radiation of 23CNp using neutron activation analysis or by

spectrophotometric method. The average values calculated for the uranium content in

the different samples using neutron activation analysis are generally higher than the

average values obtained from measuring the natural y-activity. The difference is not

more than 5 ppm . Moreover, the sensitivity of NNA is higher, accordingly the content

of uranium in gypsum is determined using this method only. Determination based on

measuring natural y-radioactivity is found to need longer measuring times otherwise, the

percent error of computing the net area under peak is very high. On the other hand

analysis based on measuring natural y-radioactivity avoid high exposure doses. The

average values calculated for th® uranium content (ppm) in the phosphate ore and some

products of AZFC using NAA are as follows:

Gypsum < 5, granular single superphosphate (GSSP)=50.45, single superphosphate

(SSP)=42.60 and phosphate ore used by AZFC=72.6. Whereas the average values for

uranium content(ppm) calculated from measuring the natural y-radioactivity are : 70.1 for

phosphate or®, 46.72 for GSSP and 41.16 for SSP. Th© content of uranium in each

sample was calculated using the uranium standard IAEA No.S-12 which contains 0.014

U-,O8. The amounts of uranium found are within the expected limits.

The uranium content of the AZFC drainage water (at discharge point), which is

determined spectrophotometrically after preconcentration on Chelex-100 is found to be

0.205 ± 0.02 (ppm). This value is considered to be low enough and do not add any

hazardous effect to the environment. Which is the main objective of our study.

32

ACKNOWLEDGMENT:

The IAEA is acknowledged for partiaJly supporting and financing this work through a

research contract No. EGY/6376/RB. Also, Prof. Dr. H.F.Aly is Highly acknowledged for

his sponsoring of this work.

REFERENCES

(1) K.S.Park, N.B. Kim, H.J. Woo, fCY. Leeand Y.Y.Yoon, Amer.Nucl. Soc.,88,41 (1991).

(2) F.T.Awadalla and F. Habashi, Fresenius Z. Anal. Chem.,324,33 (1986).

(3) E.A.Stadlbauer, H.Hingmann and C.Trieu.G.l.T. Glas und Instrumenten-Technik-

Fachzeitschrift fuer das iaboratorium, 29, 772 (1985).

(4) R.J.Correia, A.Weber-de-D Alessio and R.H.Zucol, 9. Scientific meeting of Argentina

Assodation of Nudear Technology, San Carlos de bariloche (Argentina) 3-7 Nov.

(1980).

(5) H.Gorecka, H.Gorecki, Talanta, 31,1115 (1984).

(6) N.Vucic and Z.llic, J. Radioanal. Nucl. Chem., 129, 113 (1989).

(7) P.Burba, Fresenius Z. Anal. Chem., 334, 357 (1989).

( 8) International Commission on Radiation Units Measurements, Measurements of Low

Level radioactivity. Westington, DC : ICRU;ICRU Report No. 22 (1972).

(9) W.Seelman - Eggebert, G.Pfennig and H.Munzel Chart of the Nuclides 4 th ed. (1974)

Gersbach & Sohn Verlag, 8 M'unchen.

(10) Environmental Measurements Laboratory, U.S. Department of Energy Report HASL-

300 Nov.(1990).

(11) A.A.Nemodruk and LP.GIukhova, J. Anal. Chem. of USSR, 18, 85 (1963).

(12) A.K. El-Shamouby, M.EI-Khosht and H.EI-Naggar, Egypt J.Phys. 16,1, 81 (1985).

(13) K.Schwochau, L. Astheimer, H.J.Schenk and J. Schmitz, KFA Report Jul-1415 April

(1977).

33

(14) F.H.EI-Sweify, R.Shabana, N.Abdel-Rahman and H.F.Aly Solvent Extr. Ion Exch.

4,3,599 (1986).

(15) C.Keller, The Chemistry of the transuranium Elements P.200 Verlag Chemie (1971).