Journal of Nuclear and Radiochemical Sciences, Vol. 8, No.1, pp. 25-30, 2007

Analysis of Uranium Bearing Samples for Rare Earth and Other Elements by k0-Based
Internal Monostandard INAA Method
S. Tiwari, A. G. C. Nair, R. Acharya, A.V.R. Reddy, and A. Goswami*
Radiation Safety Systems Division, Radiochemistry Division, Bhaba Atomic Research Center, Trombay,
Mumbai – 400 085, India
Received: January 24, 2007; In Final Form: May 15, 2007
A k0-based internal monostandard instrumental neutron activation analysis (IM-INAA) method was applied for themultielement analysis in uranium bearing samples. Spectral interference correction factors in INAA due to neutron induced fission of uranium for La, Ce, Nd, Zr, Ru, and Mo as well as activation of uranium for Sm and Lu
were evaluated using elemental standards. The correction factors were validated by standard addition method in asynthetic sample containing known amount of natural uranium. For evaluating the accuracy of the IM-INAA
method, the low uranium containing SRM 1633a (coal fly ash) obtained from NIST was used. For method validation of analysis of uranium bearing sample, SRM 1633a spiked with uranium (about 0.05%) was analyzed by IMINAA method. The standardized IM-INAA method was applied to analyze uranium ore samples obtained from
Jaduguda and Bhatin mines, Jharkhand, India for multielement content including U, Th, and rare earth elements(REEs). Chondrite normalized REE patterns were plotted for obtaining Ce and Eu anomalies.

1. Introduction
Instrumental neutron activation analysis (INAA) is a nondestructive isotope specific nuclear analytical technique forsimultaneous multielement analysis at major, minor, and tracelevels. The method of INAA requires minimal sample preparation and experiences negligible matrix effect due to high penetration power of activating neutrons and the measured
γ-radiation. This technique offers high sensitivity and selectivity for the determination of concentrations of a large number of
elements including U, Th, and rare earth elements (REEs).1,2 In
fact, INAA is one of the best methods for the determination ofconcentrations of REEs, in many geological and environmental
matrices, due to their favorable nuclear properties like (n, γ)
cross section, isotopic abundances and γ-ray abundances.3-5
However, determination of REEs like La, Ce, and Nd and otherelements like Zr, Mo, and Ru by INAA in the samples containing uranium gives higher (enhanced) values due to spectralinterference from neutron induced fission of uranium.6-8 Twoother REEs namely Sm and Lu are also interfered due to γ-raysof activation product of uranium (239Np). Thus for uranium
bearing samples, appropriate corrections due to spectral interference of uranium have to be made for these elements toobtain the accurate concentration values determined by INAA.
The extent of interference (correction factors) can be determined by irradiating known amounts of uranium and elemental
standards of interest and comparing the activities formed. Bothparametric and experimental correction factors expressed as(MX /MU), microgram of the element of interest per microgramof uranium, are reported in literature for the above-mentioned
elements.6-8 In order to apply this correction, the amount of
uranium in the sample must be determined first and then multiplied by correction factor (MX/MU) which is further subtracted
from the measured amount of that element. Thus, for routine
as well as faster analysis of samples and to circumvent chemical separation of uranium, it is necessary to standardize amethod to estimate these elements by INAA along with otherelements.
*Corresponding author. E-mail: agoswami@barc.gov.in. Fax:
+91-22-25505151

Determination of concentration of elements including REEs
is carried out both by the relative and k0 methods of NAA. The
advantage of k0-method over relative one is that it uses a single
comparator (like 197Au) instead of multielement standards usedin relative method. The details of k0-method of NAA are givenin the references.9,10 Recently, we have developed a k 0 -based
internal monostandard INAA (IM-INAA) method applicablefor the analysis of different shape and size samples.11-13 Theinternal monostandard method for analysis of non-standard
geometry sample using prompt γ-ray NAA (PGNAA) was initially developed by Sueki et al.14 This method gives elemental
mass ratio with respect to the internal monostandard. A priori
knowledge of concentration of the monostandard is used toconvert the elemental concentration ratios to their absolute values. The method is geometry independent since it utilizes insitu relative detection efficiency. The in-situ detection
efficiency was determined, in our method, using γ-rays fromthe activation products of the elements present in the sample toovercome the problem of γ-ray self-attenuation in the sample.11,12 It has been applied by us for the analysis of large size
and non-standard geometry samples like certified referencematerials, alloys of nuclear cladding materials like zircaloy andstainless steel and wheat grains.11-13
In the present paper, spectral interference contribution due
to uranium fission was evaluated by determining correction
factors for La, Ce, Nd, Zr, Ru, and Mo in INAA. Elemental
standards of these elements and uranium were used to arrive at
the correction factors. In the second stage, correction factors
were validated by determining the amount of these elementsfrom the uranium sample of 25 µg spiked with known amounts
of above-mentioned elements. γ-Ray spectral interference for
Sm and Lu due to activation of uranium was also evaluatedusing pure uranium standard. IM-INAA was used to determine the relative concentrations of elements including U and
REEs in this SRM with and without addition of uranium. IMINAA of SRM 1633a spiked with uranium was used to validate
the method for uranium bearing sample, whereas analysis of
SRM 1633a only was carried out to evaluate accuracy of themethod. The element Fe was chosen as the comparator element, since its activation product (59Fe) does not get contribution from neutron induced nuclear fission of uranium and its© 2007 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 06/30/2007

26

TiwariJ. Nucl. Radiochem. Sci., Vol. 8, No. 1, 2007

certified concentration in SRM 1633a is relatively high(9.4± 0.1)% having low uncertainty (~1%).15 Its activation
product (59Fe) has a long half-life (44.5 d) which makes it suitable to be a comparator element mostly for medium and longlived activation products. The standardized method wasapplied to uranium ore samples, one each from Jaduguda andBhatin mines, Jharkhand, India for the determination of concentrations of many elements including REEs.
2. Experimental
2.1. Sample irradiation and measurement of radioactivity. Elemental standard solutions of La, Ce, Nd, Ru, Zr, andMo were prepared using either respective AR grade compounds
or pure metal foils and the standard for uranium was preparedusing U3O8 compound. Accurately weighed elemental standard
solutions containing 5 to 200 µg of elements were dried on afilter paper. Standard solutions of elements were transferred byweight onto Whatmann filter paper kept inside the polyethylene
pouches sealed from three sides. The solutions were allowed
to dry in air or under IR and then polyethylene was sealed
before sending for irradiation. These elemental standards weresealed in polyethylene along with uranium standard (about 25–
50 µg). The samples of NIST SRM 1633a, SRM spiked withuranium standard and finely ground uranium ores in the mass
range of 75–150 mg were used for irradiations. All samples
were sealed in polyethylene and irradiated for duration of 5 h
in the E8 position of Apsara reactor, Bhabha Atomic ResearchCentre, Mumbai. Similarly the uranium ore samples were coirradiated with SRM 1633a. The neutron flux at this positionis ~5×1011 cm –2 s –1. After appropriate cooling, the irradiatedsamples were assayed for γ activity using a 40% relative efficiency HPGe detector coupled to an MCA. The small size
samples (75–150 mg) and standards were counted at 10–15 cm
distances with respect to the detector to minimize any truecoincidence effect. Standard source of γ-rays, 152Eu was used
for energy calibration of the detector. The detector system hada resolution of 2.0 keV at 1332 keV peak of 60 Co source. The
γ-ray spectra were analyzed for peak area determination using
peak-fit software PHAST developed at our institute.16
2.2. Concentration calculation. When a homogeneous
sample is irradiated in a neutron flux, the ratio of mass (m) of
an element (x) to mass of the internal comparator element (y)in the sample by k0 -based IM-INAA method13 is given by,mx ((S D C) (f+Q0 (α))) y PAx (εγ) y k0,Au (y)=,my ((S D C) (f+Q0 (α))) x · PAy · (εγ) x · k0,Au (x)(1)

where PA is the net peak area under the γ peak of interest, S is
the saturation factor (1–e–λti), D is the decay factor (e–λtd), C is
the term used for correcting the decay during counting period
and is given by ((1–e–λLT)/λ), ti, td , and LT are durations of irradiation, cooling, and counting times, respectively, f is the thermal to epithermal neutron flux ratio, α is the epithermal
neutron shape factor, Q0 (α) is the α corrected Q0 value,17 whereQ 0 is the ratio of resonance integral (I0) to the 2200 ms–1 (n, γ)
cross section (σ0), εγ is the in-situ relative detection efficiency.12
The α parameter represents the non-ideal epithermal neutron
flux distribution (1/E1+α) in the irradiation position of a reactor
and it was experimentally determined by "Cd-ratio for dual
monitor" method using 197Au and 94Zr monitors.9,10 The f-value
was determined by cadmium ratio method using 197Au as themonitor.10 The thickness of cadmium foil used was 0.84 mm.
The f and α values of E8 position of Apsara reactor are
65.6±1.8 and 0.013±0.004, respectively.13 The k0,Au is a factor
for the γ-ray of the activation product of interest with respect tothe γ-ray of the activation product of the monostandard, and it
is taken from the latest compilation by De Corte and Simonits.16

The literature k0-factors are experimentally determined recommended values for use in k0 -NAA work. Theoretically the k0 factor is defined as:
k0 =M* θγσ 0M θ* γ * σ 0*,(2)where M is the atomic mass, θ is the isotopic abundance and γ
is the γ-ray abundance. The symbol "*" refers to the corresponding parameters of the comparator (e.g. 197Au).
2.3. In-situ relative efficiency detection. One of theimportant input parameters for IM-INAA is the γ-ray detection
efficiency. Use of relative efficiency is adequate to determine
the concentration ratio as seen in eq 1. While using γ-rays from
more than one radionuclide to cover the requisite energy range,
the expression for efficiency is given by,mln εR(E γ) = kj + ∑ ai (ln E γ) i ,

(3)

i=0

where εR(E γ ) is the relative detection efficiency of the γ-ray ofenergy E γ, ai’s are the coefficients of the polynomial of order m
and kj is a constant characteristic of the j-th nuclide. The radionuclides used for efficiency calibration should have two or
more γ-rays to obtain a smooth calibration plot. In our calculations a third order polynomial (m = 3) was used. The details of
in-situ detection efficiency calibration are given in References
11 and 12.
2.4. Calculation of correction factors due to fission of
uranium. Experimental correction factors due to uranium fission for La, Ce, Nd, Ru, Mo, and Zr in µg per µg of uranium
were arrived using a comparative method. The correction factor for 153Sm due to uranium fission is very less,8 so it was notdetermined in the present work. The correction factors werealso calculated theoretically as follows.8 The activities produced due to activation (Aa) and fission (Af ) in a nuclear reactor
are given by,
Aa = N(φthσ 0 + φe I0)(1–e–λti) ,(4)

Af = NU(φthσ 0 + φe I0)(1–e–λti)Yf ,(5)

where N is the number of target atoms of element of interest,
NU is the number of target atoms of 235U, since fission from 238U
is negligible in the irradiation position used, Yf is the fission
yield of the isotope of interest,8 φth is the thermal neutron flux,
φe is the epithermal neutron flux, σ0 is the thermal neutron
absorption cross section and I0 is the resonance integral for the(n, γ) reaction in eq 4 and the corresponding cross sections forneutron induced fission are given in eq 5. The relevant nuclear
data required for activation (eq 4) were taken from theReferences 17 and 18, and the data for nuclear fission (eq 5)
were taken from Reference 8. In the calculation, the experimentally determined f-value (65.6) was used instead of absolute
neutron flux values. The fission interference correction factor(mass of element per mass of uranium, MX /MU) is given by,
MX
Af
=
.
MU
Aa

(6)

Interference contribution calculation of 140La is dependent
on the cooling time due to its growth from its precursor 140Ba,
which is also a fission product. For correcting its interference,eq 6 was multiplied with the factor (e0.36Td −1), where Td is theduration of cooling in days.
3. Results and discussion
The correction factors due to uranium fission obtained for
different isotopes namely 140 La, 141Ce , 143Ce, 147 Nd, 99Mo,
99
Mo(99mTc), 95Zr, 97Zr, and 103Ru are given in Table 1. The values of correction factors reported in the table are the mean val-

Analysis of Uranium Bearing Samples for Rare Earth

J. Nucl. Radiochem. Sci., Vol. 8, No. 1, 2007

ues and unweighted standard deviations from four independent
experiments. The % uncertainties (%RSD) are 1–5%, except
for Nd (10%), which has a lower sensitivity by NAA comparedto other REEs studied. The theoretically calculated values
along with literature values7,8 are also given in Table 1.
Experimentally determined and theoretically calculated values
are in good agreement with literature values. Higher uranium
fission correction factors were observed for the nuclides namely
97
Zr, 95Zr, 99Mo(99mTc), 99Mo, and 143Ce due to higher fission
yields.8 It is to be noted that if the concentrations of the elements present in the sample are comparable to uranium concentration, correction due to neutron induced fission of uranium
will be significant. Out of these, the correction factor for La isdependent upon the cooling time as 140Ba (12.75 d) decays to140
La (1.68 d). This correction factor for 140La could be minimized by counting the sample with less decay period after irradiation (within a week) so that the cor rection due tocontribution from the decay of 140Ba would be less (within 3%).
The determined value of correction factor for 140La (Table 1) isin good agreement with the value reported by Glascock et al.8
In our work, a decay period of 6 days (correction factor 2%)
was maintained through out the work for determining concentration of La in uranium bearing samples. In the second stage,correction factor procedure was validated by determining theamount of these elements from the sample containing 25 µg of
uranium and known amounts of La, Ce, Nd, Zr, Mo, and Ru
and the results are given in Table 2. A good agreement (within±4%) between expected values and measured values validated
the method of obtaining correction factors. Characteristic γrays of the 177Lu (208.4 keV) and 153Sm (103.2 keV) have spectral interference from the 209.8 and 103.8 keV γ-rays of 239Np,

27

239

daughter product of U. Between these two nuclides, interference for Sm is more severe. γ-Ray spectral interferences were
evaluated for the γ-ray peaks of interest using intensity ratios
obtained from a neutron activated pure uranium sample. The
correction factors obtained for Sm and Lu were 1.9 and 0.3 interms of intensity ratios of 103.2 keV and 208.4 keV to 277.6
keV for 153Sm and 177Lu to 239Np, respectively.
Table 3 gives the concentration of elements determined in
the NIST SRM 1633a along with the certified values. A typical plot of relative γ-ray detection efficiency as a function ofenergy generated using neutron activated sample of SRM 1633a
is given in Figure 1. Ten selected γ-rays (in the range of 121–
2754 keV) from four activation products (Figure 1) were used
for constructing the relative efficiency curve.11,12 These peakareas were used to arrive at relative elemental concentrations
by the IM-INAA method. All the relative elemental concentrations were converted to their absolute values using the certified
concentration of Fe, which was used as the monostandard.12
The concentration values in Table 3 were arrived from four
replicate experiments and the uncertainties quoted are due tostandard deviations at ±1σ confidence limit. Since time to time
literature values are published, for comparison purpose twosuch literature values8,19 are given in this table along with NIST
certified or information values.15,20 The determined elemental
concentrations (column 3) of SRM 1633a were within 6% of
the certified values15,20 except for uranium (9.8%). However,our determined concentration of uranium 11.2±0.4 is in good
agreement with the literature value of 11.4±0.3.19 This agreement between determined values and certified ones validated
the IM-INAA method. The concentrations of elements namelyTh, La, Nd, Sm, Yb, and Lu, whose certified or information

TABLE 1: Uranium fission interference correction factors of elements in INAA
Theoreticalcorrection
factor

Ref. 7

Ref. 8(0.0027±0.0002)
× (e0.36.Td –1)

0.016

Variable*(0.0028±0.0002)
× (e0.35893.Td –1)

0.34±0.01
1.35±0.03
0.20±0.02
10.81±0.1729.50±1.10
1.34±0.05
1.47±0.03
0.145±0.002

0.28
1.33
0.22
10.6
33.5
1.71
1.71
0.14

0.27
NA
0.23
10.9
NA
NA
1.6
0.13

0.287±0.008
1.35±0.04
0.21±0.01
11.3±0.2
26.6±0.9
1.39±0.05
1.41±0.05
0.126±0.003

Element

Radionuclide

Eγ
(keV)

Experimental
correction factor

La

140

1596.5

Ce

141

145.4
293.3
531.0
724.2
355.4
739.5
140.5
497.1

La

Ce
Ce
147
Nd
95
Zr
97
Zr
99
Mo
99
Mo(99mTc)
103
Ru
143

Nd
Zr
Mo
Ru

NA - Not Available, *Cooling time dependent
TABLE 2: Validation of uranium fission correction factors by standard addition method: Estimation of elements in synthetic sample containing natural uranium (25 µg) by INAA

Element
La
Ce
Nd
Zr
Mo
Ru

Radionuclide
140

La
Ce
143
Ce
147
Nd
95
Zr
97
Zr
99
Mo
99
Mo(99mTc)
103
Ru
141

Amount(µg)
beforecorrection
(A)
5.725
13.8
39.3
53.9
455.3
919.5
59.7
63.6
60.2

Amount (µg)
due touranium
(B)
0.525
8.5
33.8
5
270.3
737.5
33.5
36.8
3.6

Amount (µg)
obtained after
correction(C =A−B)
5.2±0.1
5.3±0.2
5.5±0.2
48.9±3.9
185.0±7.4
182.0±3.6
26.2±1.026.8±0.556.6±1.6

Amount
Added
(µg)
(D)
5.04
5.52
5.52
48.6
177.5
177.5
26.3
26.3
58.5

%
difference
(C−D)
3.2
-3.9
-0.4
0.62
4.2
2.5
-0.4
1.9
-3.2

28

TiwariJ. Nucl. Radiochem. Sci., Vol. 8, No. 1, 2007

TABLE 3: Determined elemental concentrations (in mg kg–1 unless % is indicated) in NIST SRM 1633a (coal fly ash)Element

FormedisotopeEγ(keV)This work

24

Na%
K%
Sc
Cr
Ga
As
U
Th
La
Ce

Na
1368.60.180±0.006
K1524.71.97±0.03
46
Sc
889.3
39.6±0.5
51
Cr
320.1
195±4
72
Ga
834.0
60.3±2.8
76
As
559.1
143±3
239
U/239Np277.6
11.2±0.4
233
Th/233Pa
312.1
29.7±1.7
140
La
1596.578.4±0.6
141
Ce
145.4
186.2±4.6
143
Ce
293.3
182.6±4.4
147
Nd
Nd
531.0
78.4±3.0
153
Sm
Sm
103.2
15.8±0.6152EuEu
1408.04.1±0.1
169
Yb
Yb
198.0
7.40±0.92
175
Yb
396.3
7.89±0.12
177
Lu
Lu
208.4
1.27±0.04
NA- not available; ( ) information value, *Ref. 20
1042

Nuclides used:
La, 152Eu, 239Np and 24Na

Element

Relative detection efficiency

Na%
K%
Sc
Cr
Ga
As
Th
U
La
Ce (141Ce)(143Ce)
Nd
Sm

10

Eu
Yb (169Yb)(175Yb)
Lu

-4

100

E� / keV

Ref. 8

Ref. 19

NA
NA
NA
NA
NA
NA
10.3±0.3NA74.7±0.7
174±4
174±4
78±4
16.6±0.1
3.5±0.04
7.68±0.09
7.68±0.09
1.15±0.02

0.20±0.01
2.1±0.341.8±0.4
212±6
NA
177±4
11.4 ±0.3
27.5±5
94±1
184±8
184±8
79±3
14±2
3.9±0.1
9.2±0.2
9.2±0.2
1.2±0.1

TABLE 4: Determined elemental concentrations (in mg kg–1
unless % is indicated) in SRM 1633a spiked with uranium:
before and after interference correction

-3

140

NIST Certified
value[Refs. 15 and 20]
0.17±0.01
1.88±0.06
(40)
196±6
58±5.8*145±1510.2±0.8*NANA
180.0±12.6*
180.0±12.6*
NA
NA
(4)
NA
NA
NA

1000

Figure 1. In-situ relative γ-ray detection efficiency using the activation products of SRM 1633a.

values are not available in NIST catalogue, were determined in
the present case. These concentration values agree fairly withthe literature values8,19 given in Table 3. Though contributions
from uranium fission to La, Ce, and Nd are very less in thiscase since concentration of uranium is 11.2 ppm, correction
factors were applied to arrive at final concentration values.
Table 4 gives the concentrations of the elements in the SRM

SRM spiked
with uranium
0.185±0.003
1.99±0.05
39.1±0.5
203.0±9.6
59.7±2.0
148.0±1 .6
29.2±1.5493±1*
86.1±0.1(75.8±0.1)345.7±4.5(178.0±2.3)
840.4±5.8(174.7±1.2)
179.8±7.7(81.2±3.5)
38.1±2.9(16.1±1.2)
4.3±0.1
7.28±0.39
8.02±0.09
2.43±0.04(1.21±0.04)

SRM only[Table 3, column 4]0.180±0.006
1.97±0.03
39.6±0.52
195±460.3±2.8143±329.7±1.7
11.2±0.478.4±0.6
186.2±4.6
182.6±4.4
78.4±3.0
15.8±0.6
4.1±0.1
7.40±0.92
7.89±0.12
1.27±0.04( ) – interference corrected REE concentrations, *uranium
concentration in spiked sample

1633a spiked with uranium (493 mg kg–1 as the determinedvalue) as well as spectral interference corrected concentrationsof specific REEs. The uncertainties quoted in Table 4 (column
2) are due to peak fitting error and counting statistics at ±1σ
confidence limit. The amount of uranium was estimated using
the 277.6 keV γ-ray of 239Np. The experimental contributionsof γ lines from 239Np were computed and corrected to arrive at
peak areas of 208.4 keV (177Lu) and 103.2 keV (153Sm), respectively. It is seen that the values of elemental concentrations
determined using purely (n, γ) reactions are found to be unaltered (agreed within ±4%), whereas the concentrations of ele-Analysis of Uranium Bearing Samples for Rare Earthments, whose activation products have contributions fromfission and activation of uranium are enhanced. Discernableenhancement was observed for the isotopes of La, Ce, Nd, Sm,
and Lu, which have contributions from fission as well as activation of uranium. The interference corrected values of REEs
are in good agreement (within ±5%) with the results obtainedfor SRM 1633a only (Table 3).
The IM-INAA method was used to determine elemental
concentrations in two different uranium ore samples obtained
from Jaduguda and Bhatin mines. The element Fe was used as
the internal standard. The relative elemental concentrations
were converted to absolute values by determining Fe concentration using certified value of Fe in SRM 1633a. Figure 2
shows a typical γ-ray spectrum of the neutron-activated sampleof Jaduguda ore. The results of elemental concentrations for 22
elements including 8 REEs were arrived from four replicate
experiments and are given in Table 5. The uncertainties quoted
in Table 5 are the standard deviations at ±1σ confidence limit
and %RSD values are in the range of 1–6%. The concentrations of uranium determined in uranium ores from Jaduguda
and Bhatin mines were 577±11 and 463±9 mg kg–1, respectively. Since the uranium concentrations are very high, spectralinterference due to uranium was significant. Appropriate corrections (using data in Table 1) were applied to calculate theconcentration values of the REEs that are interfered by uranium fission and activation. The concentrations of REEs thus
determined were used to analyze possible REE anomaly andfractionation of light REE (LREE) and heavy REE (HREE).
The rare earth elements, La to Lu, are widely utilized as
tracers for a range of geological processes because of theirstrikingly similar electronic configurations that give rise topredictable chemical behavior along the series. Its abundanceor pattern in minerals and ores provides fundamental information on the cosmic nucleosynthesis.4,21,22 It is known that REE
patterns in geological samples are influenced by depositional
environment. They exhibit a smooth and regular variation withatomic number Z with some striking features of deviation for
Ce and/or Eu attributable to the reducing or oxidative environ-

5000
4500
4000
3500
3000
2500
2000
1500
1000
500
50000

46
147

550

40000

147

140

Nd

600

95

650

700

750

800
233

141

20000

Sc

La

Zr

Nd

30000

239

Ce

Np

850

900

950

1000

Pa
140

La

10000
0

0

50

100

150

200

250

300

350

400

450

500

Energy /keV

Figure 2. Low energy part of the γ-ray spectrum of a neutron activated uranium ore sample from Jaduguda mines.

1000
Normalised REE in SRM 1633a spiked with uranium
Normalised REE in SRM 1633a interference corrected

REESample/REEChondrite

Element
Jaduguda
BhatinNa
6836±475155±46Fe(7.1±0.3)×104(7.7±0.4)×104
Cr
202±2
200±2
Co
46.4±1.2
39.6±1.4As
1.6±0.1
2.0±0.1
Mn
223±2
228±2
K
12097±199
15599±212Sc
14.1±0.3
14.2±0.4Zn58.6±3.865.0±2.5Hf
3.7±0.1
4.35±0.2
Rb
120.4±4.8166.4±6.6
Cs
2.83±0.17
2.80±0.11Th
8.2±0.2
9.7±0.3
U
577.4±10.7
462.6±8.9
La211.2±1.8254.1±2.3
Ce337.7±10.1
434.3±17.4
Nd269.5±13.5
325.0±16.3
Dy22.2±1.0
25.4±1.3Sm14.1±0.4
20.8±0.8Eu
2.11±0.06
2.50±0.06
Yb
10.5±0.513.3±0.3
Lu
2.1±0.1
3.0±0.1
La*/Lu*10.4
8.8
La* and Lu* - Chondrite normalized valueCountsTABLE 5: Determined elemental concentration (mg kg–1)
in two uranium ore samples by IM-INAA
S.N.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

29

J. Nucl. Radiochem. Sci., Vol. 8, No. 1, 2007

100

10
La Ce -- Nd -- Sm Eu -- -- -- -- -- -- Yb Lu

Rare Earth Element
Figure 3. Chondrite normalized REE patterns in SRM 1633a (coalfly ash): spiked with uranium and uranium interference corrected.

ment at the formation stage or fractionation process.5,23 The
REE patterns are obtained by plotting chondrite normalized
REE concentration vs. Z of REE.4,5,23 The chondrite normalized REE patterns of SRM 1633a spiked with uranium sample
were obtained for both uncorrected and corrected for REE contributions due to uranium interference and the plots are given
in Figure 3. The chondrite REE concentrations in mg kg–1 aregiven in parentheses: La (0.33), Ce (0.88), Nd(0.6), Sm (0.181),
Eu (0.069), Dy (0.317), Yb (0.20), and Lu (0.034).24 The connecting lines from one REE to the other in Figure 3 are the eye
guides only. The interference corrected pattern of SRM 1633a
is in good agreement with the pattern obtained by Glascock et
al.8 except for Sm, showing the validity of the correction factors. Interference correction factor for 103.2 keV of 153Sm due
to γ-ray of 239Np (103.8 keV) was not carried out by Glascock et
al,8 which is an important correction. Similar way chondrite

30

TiwariJ. Nucl. Radiochem. Sci., Vol. 8, No. 1, 2007
1000
Jaduguda uranium ore
Bhatin uranium ore

Acknowledgements. The authors are thankful to Dr. V.K.
Manchanda, Head, RCD and Shri D.N. Sharma, Head, RSSD,BARC for their support and keen interest in this work. The
authors thank the operation crew of Apsara reactor for theirco-operations during sample irradiations.

REESample/REEChondrite

References

100

10
La Ce -- Nd -- Sm Eu -- -- Dy -- -- -- Yb Lu --Rare earth element
Figure 4. Chondrite normalized REE patterns in uranium ore samples.

normalized REE patterns, using corrected REE values, wereobtained for the two uranium ores as shown in Figure 4. The
normalized REE patterns for both the ore samples are found tobe similar. As observed in Figure 4, REE patterns of the ore
sample showed negative Ce as well as Eu anomalies, indicatinga reduced depositional environment.4,5,23 The fractionation of
LREE and HREE was obtained for the ore samples from the(La/Lu)* ratio, i.e. [(La sample /La Chondrite)/(Lu sample /Lu Chondrite)].
The magnitudes of the (La/Lu)* ratios (Table 5) were > 1 in all
the cases suggesting a high enrichment of LREE.
4. Conclusions
Correction factors for elements namely La, Ce, Nd, Zr, Mo,
and Ru for the contribution from neutron-induced fission of
uranium and for Sm and Lu due to activation of uranium in
INAA were determined and validated by standard addition
method. The k0 -based IM-INAA method was effectively used
for multielement analysis in NIST SRM 1633a, SRM 1633a
spiked with uranium and uranium ores containing uranium
concentrations in the range of 0.05–0.06%. Using this method,concentrations of 22 elements including 8 REEs in two uranium ore samples were determined. Chondrite normalized
REE patterns were used to arrive at the prevalent environment
in the ore sites. For routine analysis of uranium bearing sample
by INAA, this method is simple, does not need standards foreach element, takes care of geometrical effects since it uses insitu detection efficiency and easy to apply since no chemical
separation is required.

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