The application of x-ray diffraction analysis to uranium ceramics

ANALYTICA

CHIhI ICA ACTA

THE APPLICATION CERAMICS PART

OF

I. QUANTITATIVE

C. J. TOUSSAINT

I<. CONTI+,

277

X-RAY

DIFFRACTION

ANALYSIS

AND

G.

A~alylical and Mheral CCR- Ispra (Italy)

Chemistry Secfim.

(Kcccivcd

rgG6)

August 8th.

OF THE

ANALYSIS

BINARY

MIXTURE

TO

URANIUM UOa-Us08

VOS

Ewatorn,

The growth of the nuclear technology for power applications, has stimulated the evaluation of ceramics of uranium as fuel materials. These ceramics have interesting characteristics, such as good irradiation stability, high neutron utilisation and high melting point 1.2. A proper study of these materials requires analytical methods for determining their composition. Much work involving X-ray diffraction has been clone for other materials, e.g. determination of copper in bras@, metallic platinum in platinum-alumina catalysts4, retained austenite in steel@, quantitative analysis of mixed fertilisersa, but the only application to nuclear materials seems to occur in a study of a mixture of uranium carbides by ATODA et ~1.7. The present work was limited to a direct determination without use of an internal standard, because the composition was only biphasic. In this investigation the possibility of determining UOZ in USOS and vice-vevsa using the X-ray diffractometer and the Debye-Scherrer camera, was studied. EXPERIMENTAL

Afiparatus and operating conditions The apparatus used was a standard Philips diffractometer, including a proportional counter, and pulse-height discrimination. For the photographic measurements, a large Debye-Scherrer camera (diameter x14.83 mm with an entry collimator of 0.5 mm) was employed. The sample was introduced in a capillary tube with a diameter of 0.2 mm. The intensities were measured with the Siemens type A photometer and the Joyce-Loeb microdensitometer M K III B. A complete list of the equipment and instrumental conditions is given in Table I. The X-ray diffractometer analysis requires a minimum amount of 3 g of sample and the time for a single determination (excluding the grinding time) is about I h; for the Debye-Scherrer technique, the minimum sample size is only I mg and the time requirement is ca. 5 h. Saqble

@eg5avation

AND ALEXANDER*, in discussing the statistical factors to be considered for the case of quartz powders, mention that the crystallite size must be less than 5 ,u to achieve a 1% reproducibility in the intensity measurements. Therefore the * Present address : Facultc? des Sciences d’orsay. KLUG

Anal. Skim.

Acta, 37 (x967)

277-283

R.

278 TABLE

COWI’I,

G. VOS

I

hPPARh’l’US

AND

INSTI~UMlSNThl.

CONDITIONS -~--

X-IZuy

C. J. TOUSSAINT.

di//vaclometer

-___

Cu tub with Ni filter 50 1cV - 20 mA Divcrgcncc and scatter slit : I’ Receiving Slit: 0.2 mm Proportional counter Counting time : x00 Y~C Puluc-height tliscriminirtion

Debyc-Scl4errer tedkqzre

--.-~

---

Camera tliamctcr: 114.83 mm Collimator: 0.5 mm Sample capillary: 0.2 mm Jhcpouurc time: 4 h Microdcnsitomctcrb: Sicmcns type A Joyce-Loch M IC 1 II B

samples were ground in a mill (Siebteclmik-Mill) for 2 II. It was found that grinding powders under carbon tctrachloride to avoid the oxidation of UOa in UsOe was unnecessary. Mcasurcmcnts of the stoichiometry of an UOZ sample before and after grinding for 2 11 without carbon tetrachloride, gave the same value (2.130) for the ratio 0:U. This long period of grinding was used mainly because it seems to be a very cffcctive means of minimizing preferred orientation error.+. In order to reduce further any possible orientation errors and also to facilitate sample mounting, “lakeside” (a mixture of natural resins) was adclecl to the samples in an amount about 20 o/o of their weight. The samples used for the calibration curves were UOa (0: U =2.x30) and U3Oa (0: U = 2.G80) obtained from Merck. The ratio 0: U was determined by coulometry. Several diagrams for uranium oxides with different stoichiometry were recorded and did not give any notable difference in the peak intensity and peak position, between a UOS.OOOsample and a UO 3.130 sample for samples of the same origin. Nevertheless, in the case of UOZ samples obtained by electrolysis and fused UOZ samples, prepared by high-frequency heating, a Ilighcr intensity was obtained. This is probably due to the fact that in these cases mainly small single crystals are formed. A more accurate study of this point is in progress. After grinding, the particle size of the samples and of the powders used to set up calibration curves, was between 15 and 30 ,u. These powders were obtained by sieving with a series of “precision micromesh” sieves ASTM 161-160 T. Some smaller particles, with a crystallite size of 5-7 ~1 were also obtained, but the quantity was too small for practical use. The samples were packed in the rectangular sample holder. Reprodarcibility Diff~acto~teter tec/l+zle. A reproducibility test was made by preparing IO specimens of a 30% UO~-~O~/~ U308 sample of particle size 15-30 ,u, and measuring by manual counting the peak intensities of the reflections chosen as analytical lines. The ratio of the peak intensities was calculated. The average deviation of a single determination from the mean value was found to be -t_2’34. The effect of particle size on the intensity and reproducibility was . studied by taking several fractions of a UO:! sample, measuring the intensity of the (III) peak and calculating the mean standard deviation. The results are shown in Fig. I. (The observed UOZ intensities were normalized so that the highest corresponded to 100.) The observed decrease in peak intensities with increasing crystallite size for the fraction with particle size > 20 p is Anal. Chim. Acta, 37 (1967)

277-283

ANALYSIS

OF U&-U&e

MIXTURES

279

probably due partially to extinction and partially to the specimen packing density. A comparison of the reproducibility obtained with the stationary specimen and by rotating the specimen in its own plane, showed only slightly better results for the latter method. This is in disagreement with the results of DE WOLF et a1.10, who found an improvement by a factor of about 8 in their work on silicon powders (30-50 p). curve

CUrV@

1

relatih deviation

intensity UOI (111) reflection 1001

11

g

2 standard %

4 -3

-2

70

-1

t

1

20

0 Fig.

I. Kffcct

40

of particle

60

I

120 00 100 Mean particle size )A

size on intensity

nntl rcproclucibility

of the (1 IO) reflection

of UO8.

D&ye-Sclrerrer techtique. Ten photographs of the same sample (50% UOS-~OT/, UaOe) were taken, without changing the specimen for each exposure. The relative standard deviation of the ratio of the peak intensities measured with a Siemens Type A photometer, wras 4.7 %. RESULTS

Calibration curves ajtd precision The (IIO/OII) reflection of UoOe and the (III) reflection of UOz were chosen as analytical lines in this study. The (x00) reflection of &OH was not utilized, because the addition of lakeside caused an amorphous band in that region. Figure 2 shows a portion of the X-ray diffractometer pattern of a Us08 sample containing about 7% UOZ. A background measurement at 2 0 = 24O for the &OS and 2 8=30” for the UOa was subtracted from the peaks. In order to reduce instrumental and packing errors, the ratios of the intensities were compared with the weight ratios, using the diffractometer technique. For the calibration curve covering o-Io~/~ UOe in USOS, it was found that better results were obtained by directly comparing the peak intensities with the percentages. As an example, the curves for the o-go?L U308 and those for the o-Io~/~ UOQ concentration ranges using the diffractometer are given in Figs. 3 and 4 respectively. After the calibration curves had been established, the precision was checked by analysing several synthetic samples. These samples were analysed on different days; the results obtained (Table II) are considered very satisfactory. The calibration curve for O-IOO~/~UOC in &OS obtained by the Debye-Scherrer method is given in Fig. 5. Anal.

Chim. Acta. 37 (1967)

277-283

R. CONTI,

280

C. J.

TOWSSAINT.

G.

VOS

counts/see

t

Cllo~mll uaoe

h

Big. a. X-ray diffractomctcr chrrrt rccortl obtainccl from a sa~nplc of U30” containing Scanningspcccl: x/2°/min. Full Ycdc: 3 * 103C~X.

I I

5-

7%

of UOa.

UJO& uo2

t

4-

I u02 counts/set t

3-

15(

2-

1oc

5(

l-

at

2

6

uo2 % 8

curve for the dctcrmination

of UJO~ in UOa. Concentration

range: ro-go%,.

Fig. 4. Calibration curve for the dctcrminntion

of UOs in U~OU. Conccntrntion

range: o-Io~/~.

Fig.

Anal.

3, Cdibration

4

Chim. Acta,

37 (1967) 277-283

ANALYSIS TABLE

OF uo~&os

MIXTURES

281

II

COMPARISON

BRTWEBN

THEORETICAL

AND

FOUND

VALUES

DETERMINED

BY

THE

X-RAY

DIFFRACTION

?.lETHOD --

Composilion

---_----.----UDO8 : 80.0 uaoe

.: Go.0

uoa

:

8.0

uo2

:

4.0

A ucrage (%I

Found (%I

(%)

__-80.4. 79.0. 79.3 6x.5, Go.G, 61.0 7.7, 7.8

79.6 61.0

7-75

4.25

4.3, 4.2

Rcktive error (% I 1.2 0.85 I.2

1.3

6-

2./ /

-

Weight Weight

Fig. 5. Calibration curve for o-xoo”~

UO2 U,O,,

UOs in UnOewith the Dcbyc-Schcrrcr

camera.

Limit of detection For the X-ray diffractometer measurements, the minimum composition detectable, LD, may be defined as the concentration, Co, which yields an intensity of the peak height above the background equal to 3 standard deviations of the background intensity. Thus LD=

3 C$BT PT.

where P is the intensity of the peak in counts per set after the subtraction of the background, B is the intensity of the background in counts per set, T is the counting time in set, and C, the concentration of the compound which has to be determined. The limit of detection of UO2 in Us08 was calculated for a counting time of IOO set, while the intensities of the peak and background were obtained from two samples containing 1 yh UO2. The effects of some instrumental parameters on the limit of sensitivity of UO2 was studied. From the results in Table III, it can be concluded that eliminating the B filter gave only a slight increase in sensitivity. The effect of changing the divergence Anal.

Chim.

Acta.

37 (1967)

277-283

282

R. CONTI,

TABLE EFPECT

C. J. TOUSSAINT,

G. VOS

I IL OF DII~FERI3N’C

Divergence slit Sculler slit X0---I 0 IO-1 0 4O--4O

OXPERIMI~NTAL

CONDITIONS

ON THE

LIMIT

OF SRNSITIVITY

Receiving slit

Linait of detection culcduted (0/u)

0.2 mm with /I filter mm without p filter 0.2 mm with /I filter

0.057 0.053 0.025

0.2

OF uoz

IN UsOtj

and scatter slits from IO to 4” is quite remarkable. The lowest limit of detectability (ca. o.02n/o) found with the diffractometer method is much bcttcr than the limit of about IO/ using the Debyc-Schcrrer camera. 7’1~ limit of sensitivity for U:lOs in UOO was studied by using the (100) reflection, 4” divergence and scatter slits and o.z-mm receiving slit, without the /3 Ni filter; the calculated limit of detection from tllree 0.8”/0 U&S samples (pressed into if this calculated limit corresponded to the disks)was found to be 0.075~,$, To’verify practical limit, a sample containing 0.15 :I0 U&a was prepared and the limit of detection calculated; the result found was about 0.085~/~,,which is of the same order of magnitude as the calculated value. CONCLUSION

The cletermination of UOS in Us08 powders and vice-ve~su, by X-ray diffraction gives satisfactory results. The diffractometer technique should be preferred to the shorter analysis time Debye-Scherrer camera, bccaus. e of its better reproducibility, and lower limit of detection. However, the latter method is the only one which can be employed when only small quantities of samples are available. We wish to thank the European Community of Atoinic Energy (EURATOM) which gave a scllolarship to one of us (R.C.) for this work. We are grateful to Mr. DENIS for the chemical analysis, to Professor A. MICHEL for his direction of these investigations and to Mr. H. LAURENT, Director of the Analytical Chemistry Division.

An X-ray binary mixture were compared ; relative standard

diffraction method is proposed for the quantitative analysis of the UOz-U30e. Diffractometer and Debyc-Scherrer camera techniques the former is preferable whenever sufficient sample is available. The deviation was found to be I yjO.

R&SUM&

On propose une m&hode par diffraction aux rayons-X pour l’analyse quantitative de mdlanges binaires UO&JDOB. Les deux techniques, dif fractom&tre et cam&a Debye-Scherrer sont compardes. La premiQe est prdfCrable si l’on peut disposer de suffisamment d’&chantillon. La ddviation standard relative est de 1%. Anal.

Chim. Acta, 37 (1967)

277-283

ANALYSIS

OF UO~U&I

283

MI.XTURES

ZUSAMMENFASSUNG

Es wird eine R8ntgenbeugungs-Methode zur quantitativen Analyse bin5irer U&-u&pMischungen vorgeschlagen. Diffractqmeter und Debye-Scherrer-Kamera werden verglichen. Das erstere ist vorzuziehcn, wenn gcni.igend Probe verfiigbar ist. Die relative Standardabweichung betrug I ‘j&, REFERENCES J. BELLE, Uvanizttn Dioxide, U.S. Govcmment Printing Office, Wnshington, IQGI, p. Q. P. PASCAL, Noltvemr Trait& de Chimrie Midrale, Vol. 15, Masson, Pnris, 1961. S. MIRANO,H. SASUGA AND Ii.T~nucHI,Japarz sfmz~ysf.IO (13)(Ig6r) 1361. It.A. VAN NOHDSTRAND, A. J. LINCOLN AND A. CARNF,VALIS,/IWRL.C~~~~J.,~~ (cgGq) Srg. I<.LINDGRISN, Metal Prop., 87 (4) (1965) 102. J. ANDO, J, P. SMITH AND Ft. SIEYBL,J. Agv. FoodChew., 13 (2) (1965) 18G. T. ATODA, I. HIGASIH. Y. TAKAHASHI, Y. SASA AND M. KOI~A~ASHI, Sci. Papers Inst. Chetn. Res. (Tokyo), 55 (4) (rgbx). S-Ray Diffraction lJrocedures for Polycrystullim ANI) I,.A. ALEXAXWXR, 8 H. P. KLUG A morpirous Materials, W&y, New York, I gs.t, p. 42 2. Res.Lab.Rept.,H 2517, Ig.+s. 9 L.S.BIRKS,N~~~~ 10 P.M.DIZWOLP, J.M.TAYLONAND TV. PARRIS~X,J.A~~L.P~~S.,~O(~~~~). Arral.

Clrint.

Artcr,

37 (7967)

Whys. and

277-283