Use of a Direct Current Glow Discharge Mass Spectrometer for the Chemical Characterization of Samples of Nuclear Concern*

Journal of Analytical Atomic Spectrometry

MARIA BETTI

European Commission, Joint Research Centre, Institute for Transuranium Elements, P. 0. Box 2340, 0-761 25 Karlsruhe, Germany

Direct current GDMS has been applied to conducting and non-conducting nuclear samples, namely, different types of nuclear fuels, cladding materials and nuclear-waste glasses. For the non-conducting oxide-based nuclear samples the relative sensitivity factors (RSFs), applied for quantitative analysis, are affected by the oxygen content in the matrix. For these samples the effect of 'getter metals,' such as tantalum and titanium as binder material, has been investigated and the results compared with those obtained using silver as the host matrix. Moreover, when tantalum was used as a secondary cathode, it was found to behave as a getter of oxygen. For the quantitative analysis of nuclear-waste glasses the use of matrix specific RSFs was necessary. Comparisons with RSFs obtained from other workers are made. Metallic alloys were analysed using several analytical techniques. The GDMS results obtained applying RSFs from the major metallic element uranium were in agreement with those from independent techniques, such as titration, thermal ionization MS and ICP-MS.

Keywords: Glow discharge mass spectrometry; nuclear samples; trace elements; major elements

In the field of nuclear research and technology, the chemical characterization of different types of fuels, cladding materials, nuclear-waste glasses and smuggled nuclear samples, from the point of view of trace, major and minor elements as well as from their isotopic composition, is of great importance. These materials can be analysed using several techniques based on nuclear and non-nuclear methods that can be, to a varying degree, tedious and time consuming. In the past few years non- nuclear methods based on MS have become predominant for the characterization of samples of nuclear concern. The appli- cation of ICP-MS has been widely in~estigatedl-~ for fission products and actinide determination as well as thermal ioniz- ation MS (TIMS) for the routine analysis of isotopes in liquid samples4 Glow discharge MS (GDMS) has found extensive application for trace element determination in a variety of conducting and non-conducting solid^^-^ and has also been used for the chemical characterization of samples of nuclear c ~ n c e r n . ~ - ' ~ In this application GDMS provides information on the chemical composition of the material much faster than other techniques, presenting an opportunity to change fuel production procedures, modify reactor operations or to recog- nize smuggled materials in a short period of time.

In the last four years, after the installation in this laboratory of a dc high-resolution GDMS in a glovebox,13 a great deal of experience has been acquired in the use of GDMS for the chemical characterization of samples of nuclear concern. More than 400 samples have been measured for their elemental and isotopic compositions. Among these can be numbered

* Presented at the 1996 Winter Conference on Plasma Spectrochemistry, Fort Lauderdale, FL, USA, January 8-13, 1996.

plutonium and uranium oxide specimens, mixed uranium and plutonium oxide (MOX) and metallic fuels, simulated high burn-up nuclear fuels (Simfuel), zircaloy cladding materials, nuclear-waste glasses and smuggled nuclear materials.

In the present paper some examples of the analysis of conducting and non-conducting samples of nuclear concern by a dc GDMS method are given. In particular, the problem of the analysis of non-conducting nuclear samples and the use of the most appropriate relative sensitivity factors (RSFs) for quantitative analysis of conducting and non-conducting samples are discussed. Figures of merits for the methods developed to handle different types of samples are also given and comparisons of the GDMS results with those obtained from other techniques, such as titration, TIMS and ICP-MS are made.

EXPERIMENTAL

Instrumentation

The mass spectrometer used in the present investigation was a VG 9000 GDMS instrument (Winsford, UK) modified as described p r e v i o ~ s l y ~ ~ to handle radioactive samples in a glovebox. It consists of a dc G D ion source coupled to a double-focusing mass spectrometer of reverse ( Nier-Johnson) geometry. This configuration provides high transmission (>75%) and sensitivity whilst operating at a high m/z reso- lution of 5000 with 10% valley definition. A m/z resolution up to 8000 full width at half maximum can be reached, although for higher throughput a resolution of 3000 was generally employed. Ion detection is accomplished by a dual detection system consisting of a Faraday cup for the measurement of a large ion current (typically A) and a transverse mounted Daly detector for the measurement of a small ion currents. The system provides a dynamic range of 10'. The GD was supported by high-purity argon that was additionally purified by an on-line active-metal getter system at 400°C. In addition, the discharge cell was cryo-cooled with liquid nitro- gen to about -130°C to reduce the background resulting from residual gases.143 l5

The discharge current and the voltage varied, depending on the type of sample examined, in the range of 1-2 kV by 1-2 mA with a typical value of 1.2 kV for a current of 1.5 mA. The pressure of the ion-source chamber was 8 x Torr (1 Torr = 133.322 Pa) whereas the pressure inside the discharge cell was between 0.2 and 1 Torr.

Samples Analysed

NBL95-6 (USA), Morille and Chantarelle (CEA, Paris, France) uranium oxide reference material, NIST SRM 3601-Zircaloy-4 (NIST, Gaithersburg, MD, USA) and Zircaloy-17265 (A. D. Mackay, Red Hook, NY, USA) and well characterized16 nuclear-waste glasses obtained from the unit of applied physics of this Institute were used. Non-certified

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plutonium dioxide was analysed by other techniques to provide reference concentration values. Most of the materials had non- conducting properties. The samples for analysis were received as powdered, rods and flat specimens. Powdered samples were prepared by compacting 500 mg of material into a disc 13 mm in diameter and 2 mm thick, using an hydraulic press (3630X, Spex, Edison, NJ, USA). In some cases, before compacting, the sample was mixed with silver powder [99.9999%0 (6N), Wagener, Stuttgart, Germany], titanium powder (99.9%, Johnson-Matthey, Royston, UK) or tantalum powder (99.9%0, Johnson-Matthey) to a mass ratio of 1 + 3. The contribution of the imputities from the binder matrices and the secondary cathode was measured and a blank value always subtracted for each sample analysed. A load of 8 tonnes was generally applied for 5 min. For non-conducting samples obtained as a pellet or compacted without the addition of binders, a second- ary cathode of tantalum with an aperture of 5 mm was used during the analysis. Some samples obtained from the fuel production department of this Institute were washed with acetone to remove grease and then rinsed in water and dilute nitric acid. All samples were pre-sputtered before the analysis for periods of 5-20 min with a current of 2 mA.

Relative Sensitivity Factors

Semi-quantitative data can be obtained by GDMS analysis, even when reference materials are not available. A simple comparison of the element signal intensity of the analyte with the element sensitivity of a reference element, defined as the ratio between the signal intensity and the elemental concen- tration, gives results with an accuracy of about 30%.17 However, in many cases, and in particular in the field of nuclear research, full quantitative analysis is required. Quantitative analysis of unknown samples is usually performed by applying RSFs to the measured ion beam ratios. Since RSF values exhibit some variation with the discharge conditions, matrix type and instrumental configuration, for full quantitat- ive analysis it is common to obtain experimental RSF values under the conditions to be employed in the analysis of the unknown samples. This procedure requires reasonable matrix matching and assumes reproducible sample-to-sample plasma conditions, which can be difficult to achieve. In ideal cases, RSFs are obtained by the analysis of a reference material as close as possible in composition and behaviour in the GD to the unknown sample.

The RSFs are defined as the ratio of the elemental sensitivity of an analyte element A to the elemental sensitivity of a reference element R. Thus:

where I and C are the signal intensity and the concentration of the analyte and the reference element, respectively.

Once the mass spectral interferences are resolved from the analytical signal and the blank contribution subtracted, the RSF represents the slope of a calibration curve passing through the origin.

For the anaylsis of alloys by dc GDMS, it has been shown that RSF values do not change (within experimental error) from matrix to matrix.18 These results can be interpreted as indicating that for conducting samples, such as alloys, the influence of cathodic sputtering on the RSF is not significant and the variation of the RSF mainly results from the relative ionization efficiencies. This could also be the case for metallic nuclear alloys.

On the other hand, quantitative analysis of non-conducting materials requires the development of matrix-specific RSF values to obtain results with the highest a c c ~ r a c y . l ~ - ~ ~ This could also be the case for non-conducting nuclear samples particularly those which are oxide based. I,n Table 1 the results

Table 1 Quantitative analysis of the Morille reference sample based on the RSFs obtained for the Chantarelle reference sample (CLg g- f SD)

Element

lo7Ag

llB 'Be

44Ca

2 7 ~ 1

209~i

"'Cd 59c~

GDMS value 10.2f 1.04

8 7 f 4 3.5 f 1.2 3.8 f0.3

20.9 f 1.4 9 4 f 7 5.0 & 0.3

11.1 f0.68 101.6 f 4 52.1 f 3.3

207.2 L 8.4 10.4 f 0.4 19.4f 1.3 29.3 f 1.07 144 f 8.7 142 f 3.3 103 f 7.2 93 -t 4.6

20.8 k 2.3 48.6 f 6.2

47 f 1.1 106 f 9 10228 64f7

Certified value

10.4& 1.6 9 9 f 6

3.8 f 1.6 3.4 -t 0.6

24.4 k 1.9 9 3 f 8

4.9 k 0.7 9.8&2 9 9 f 2

50.2 f 1 21 1.6 k 6.5

9.4f 1 19.3 f 1.5 24.5 f0.5 147 f 5 147 f 3 101 5 3 100 & 8

18.5 f 5.6 49.2 f 2.6 48.7 f 2.8 100f9

98.6 f 5.5 59.9 & 4.1

Bias (%)*

1.9 1.2 7.8

-11.7 14.3 - 1.0

2.0 - 13.3 - 2.6 - 3.8

2.0 - 10.6 - 0.5 - 19.6

2.0 3.4

- 1.9 7.0

- 12.4 1.26 3.5

- 6.0 - 3.4 - 6.8

* Bias (%)=(certified value - GDMS value)/certified value x 100.

obtained for the quantitative analysis of the reference uranium oxide sample Morille, based on the RSFs calculated using the other reference uranium oxide reference sample, Chantarelle, are reported.

RESULTS AND DISCUSSION

Non-conducting Nuclear Samples

Some advantages of GDMS compared with other solid-state analytical devices are the intense, steady beam of ions with a narrow energy distribution produced from the low-pressure discharge, and the physical separation of the atomization and the ionization steps of the sample material in the discharge. However, the main restricting parameter is the conductivity of the samples. To overcome this drawback the use of an rf discharge source has been investigated by a number of work- ers,22-26 but unfortunately these sources are not yet commer- cially available. For dc discharges, two methods are applied for the analysis of non-conducting materials. For flat samples a 'secondary ~ a t h o d e ' ~ ~ - ~ ' placed directly in front of the non- conducting sample surface is used to meet the requirement of conductivity. The second approach, used for powdered samples, consists in mixing the sample with a pure conducting host matrix in an appropriate ratio to obtain sufficient conductivity for a n a l y ~ i s . ~ ~ ~ ~ '

Oxide-based samples

In Table 2 a list is given of the oxide-based nuclear samples analysed so far at this Institute. As can be seen, the percentage of oxygen ranges from about 12 to 18% m/m. Oxygen is a major matrix element and this causes problems. Discharge processes, such as sputter atomization and collision-induced dissociation, release the oxygen from the oxides. Once released into the G D plasma, it influences the analytical signal by quenching excitation and ionization agents, such as high- energy electrons and metastable argon atoms, and by forming oxide complexes with the analytical species.32 Moreover, in GDMS, problems also arise from the presence of polyatomic oxides that create spectral interferences and give lower analyt-

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Table 2 Non-conducting oxide-based nuclear samples. Composition given in % mjm for each element

Oxygen content

15.2 11.8 11.8 11.8 14.9 13.8 13.2 17.9 13.8

Uranium content

99.8 88.2

49.3 61.8 73.8 82.3

46.1 -

Plutonium Cerium Neptunium content content content

-

88.2 38.9 23.3 12.4 4.5

35 35

ical sensitivity. 'Getter metals' such as titanium or tantalum bond strongly with oxygen and reduce the oxygen available to form oxides with the analytes or to quench metastable argon atoms.33

Use o fa host matrix. Pure silver, tantalum and titanium were used as host matrices to obtain conducting samples for the analysis. Since a comparison with the use of the secondary cathode was planned, only flat samples were investigated. Uranium dioxide and plutonium dioxide powder were mixed with the three binders in a ratio of 1 +3. The intensities of the signals of the U + and UO', Pu+ and PuO+ ions were considered.

In Fig. 1 the ratios U+:UO+ and Pu':PuO+ obtained with different binder material are shown. As can be seen, in the case of titanium and tantalum, which bind the oxygen stronger than silver (it getters little or no oxygen), fewer UO+ and PuO+ ions are formed than in the case of silver. For some selected trace elements of nuclear interest, such as boron, lithium, cadmium and gallium, the RSFs for the three binders were evaluated. The materials used in this case consisted of samples analysed by ICP-MS and ICP-AES and the respective

7 I

Ti Ta Ta sec.cat.

Fig. 1 U+:UO+ and Pu+:PuO+ intensity ratios from oxide-based nuclear samples obtained with different binder materials and a tanta- lum secondary cathode; m/z values measured were 238, 254, 239 and 255

concentrations found by these techniques were equal to 1.5, 2.0, 5.0 and 3.0. The m/z values used for the measurements were 11, 7, 114 and 69 at an m/z resolution of 3500. As seen from Table 3 the RSFs are dependent on the host matrix, and in the case of the use of silver, higher RSFs are obtained. This can be explained by the fact that the oxygen in the plasma is not gettered by the silver and more of the uranium and plutonium in the plasma are there as oxide species than when a gettering agent is used as the binder. This reduces the number of metal ions in the plasma available for ionization.

Use of a secondary cathode. The specimens listed in Table 2 were generally provided as pellets and owing to their radioac- tivity and to avoid cross-contamination, it was considered inappropriate to grind them to a powder. Hence, the use of a secondary cathode for these samples was exploited. Tantalum was chosen as the material for the secondary cathode and it was found that its property as a getter for oxygen could also be taken advantage of. Thus, for uranium and plutonium dioxides, the U':UO+ and Pu+:PuO+ ratios obtained with a tantalum secondary cathode were of the same order of magni- tude as those obtained with tantalum and titanium binders (see Fig. 1).

All of the samples in Table 2 were examined using a second- ary cathode of tantalum. In Fig. 2 the ratios U+:UO+ and Pu+:PuO+ are reported as a function of the oxygen content in the samples. As can be seen, with increasing oxygen content the formation of the UO+ and PuO' increases, relative to U + and Pu', even though part of the oxygen is gettered by the tantalum cathode. A separate investigation, currently in pro- gress in this laboratory, indicates that the material of the secondary cathode is of primary importance as far as the formation of the actinide oxides in the G D is concerned. As far as the samples reported in Table 2 are concerned, having the same oxygen content of 13.8% m/m, but different chemical composition, the same intensity ratios were found, indicating the predominant effect of the oxygen as a main constituent. The RSFs obtained for several trace elements are plotted as a function of the oxygen content in Fig. 3. As can be seen, the tendency is to obtain increasingly higher RSF values as the oxygen content rises. As the maximum standard deviation

Table 3 RSFs values for uranium and plutonium dioxide using different metals as host matrices (with respect to uranium and plutonium)

Host matrix Secondary cathode

Ti Ta Ta

Element UOZ l lB 1.25

'Li 2.0 1 f 0.30

f 0.23

k0.30

f0.15

'I4Cd 1.97

69Ga 1.58

PuO*

1.33 f 0.25 1.98 f 0.30 2.00 & 0.28 1.63 - f0.13

UO, 0.98 & 0.20 1.12 f0.13 0.87 + 0.20

fO.10 c 9 5

PUO,

1.04 k 0.30 1.08 f 0.20 0.90 & 0.25 0.98 - +0.12

uo2 0.97 k 0.20 1.15 f 0.28 0.90 f 0.28 0.95 *0.12

PUO,

1.05 f 0.20 1.12 f 0.25 0.88 k 0.25 0.95 k0.13

UOZ 0.98 f 0.30 1.13 f 0.20 0.90 + 0.25 c98 fO.10

PUO,

0.98 f 0.28 1.10 + 0.20

& 0.28 1.02 kO.10

c93

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11 12 13 14 IS 16 17 18

Oxygen content (% mlm)

Fig. 2 U+:UO+ and Puf:PuO+ intensity ratios from oxide-based nuclear samples analysed with a tantalum secondary cathode as a function of the oxygen sample content; m/z values measured were 238, 254. 239 and 255

3.5 T 17.8 % m/m oxygen

2.5 3.01L 0 15.2 % mlrn oxygen

13.8 % mlm oxygen

- 5 11.8 % mlrn oxygen 9 2.0 u. 2 1.5

1 .o

0.5

n " Sr Y Zr Mo Ru Rh Pd Ba La Ce Nd

Trace elements

Fig. 3 RSF values for some trace elements in uranium and plutonium dioxide samples as a function of the oxygen content. Measurements performed using a tantalum secondary cathode

obtained in the RSFs determination wask0.2, it can be said that only in the cases of Nd, Ba, Ru, Y and Mo are the RSFs more or less unaffected by the concentration of oxygen in the material. However, a clear correlation has not yet been found, and more investigations still need to be performed.

Simfuels

Simfuels are simulated high burn-up UOz based nuclear fuels and replicate the chemical state and microstructure of irradiated fuels. These samples are also oxide based, and are considered here in the group of non-conducting samples. Two of these materials of different chemical composition (rep-

Table 4 Simfuel composition: comparison of GDMS results with those

resenting different burn-ups, 3 and 6%) have been analysed by using a tantalum secondary cathode. The quantitative analysis has been made on the basis of the RSFs obtained from really fresh oxide-based fuels with the same oxygen content. In Table 4 the results obtained are compared with those reported by other workers34 for the same materials. As can be seen, the GDMS results are in good agreement with those obtained from ICP-AES and those calculated with the Origen code,34 indicating that accurate GDMS results can be obtained using RSFs from a matrix of the same composition.

Nuclear-waste glasses

The possibility of analysing glass samples by GDMS using a secondary cathode of tantalum has already been rep~r ted .~ ' The same procedure has been applied to the analysis of vitrified nuclear-wastes. RSFs have been obtained using two nuclear- waste glasses.16 They consisted of special tailor-made borosilic- ate glasses whose composition is reported in Table 5. In Table 6 the RSFs obtained are reported and compared with those available in the literature2' having the same base elements in the matrix. In this case poor agreement was found. Considering other RSF data available in the l i t e r a t ~ r e , ~ , ~ ~ . ~ ~ a lack of values for fission product elements has been found. Clearly, for the quantitative analysis of nuclear-waste glasses, matrix specific RSFs are required.

Conducting Nuclear Samples

Metallic alloys

The alloys discussed here consisted of two matrices, the major component of which was uranium, as seen from Table 7. For semi-quantitative analysis concentrations were calculated from the signal intensity of the analyte using the element sensitivity for uranium; the accuracy was not very good. The results were improved by applying the RSFs obtained for pure uranium metal. The RSF values obtained in uranium metal, with respect to uranium were as follows: 52Cr, 0.88 0.05; 56Fe, 0.58 & 0.05; 60Ni, 1.25 f 0.10; "Zr, 1.06 f 0.05; 146Nd, 0.39 f 0.03; and 239Pu, 0.99 f 0.08. Since no uranium metal certified sample was avail- able, uranium specimens from different origins were dissolved and quantitatively analysed by ICP-MS and ICP-AES. Three specimens of UZrNd and several of UPuZr were examined and the concentration values obtained for Nd, Zr and Pu were found to be in agreement with the theoretical composition concentration values. Accuracies of better than 10% and precisions of better than 5% were obtained in runs consisting of ten measurements. Owing to the fabrication method of the alloys investigated, these figures of merit were expected. Several specimens were analysed by other analytical techniques. For

cited in ref. 34. Composition given in wt % m/m.

Sample A, burn-up 3% Sample B, burn-up 6%

Compound

BaC03 Ce02 La203 MOO, SrO

ZrO, Rh203 PdO

Nd203

y2°3

R u O ~

GDMS

0.13 0.26 0.10 0.33 0.07 0.04 0.34 0.03 0.15 0.34 0.44

ICP-AES*

0.11 0.23 0.09 0.28 0.06 0.03 0.23 0.02 0.14 0.30 0.41

Origen code*

0.15 0.29 0.1 1 0.36 0.07 0.04 0.34 0.03 0.15 0.36 0.46

GDMS

0.30 0.53 0.20 0.70 0.12 0.06 0.60 0.03 0.44 0.75 0.90

ICP-AES*

0.39 0.53 0.15 0.64 0.12 0.07 0.58 0.03 0.37 0.69 0.87

Origen code* 0.3 1 0.53 0.19 0.73 0.11 0.06 0.60 0.03 0.44 0.76 0.9 1

*From ref. 34.

858 Journal of Analytical Atomic Spectrometry, September 1996, Vol. 11

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Table 5 Composition YO m/m of the two nuclear-waste glasses (from ref. 16)

Constituent

SiO,

B203 Na,O CaO MgO ZnO TiO, LiO,

p 2 0 5 ZrO, NiO

SrO

MOO, MnO,

A1203

Fe203

Cr203

y2°3

Sample 1

45.48 4.91

14.02 9.86 4.04

2.50

1.98 2.91 0.28 2.65 0.42 0.51 0.33 0.20 1.70 0.25

-

-

Sample 2

48.32 2.25

10.68 14.89 3.45 1.84

3.97

0.28

1.95 0.1 1

0.38 0.23 2.02 0.51

-

-

-

-

Constituent

4 2 0 2 CdO SnO,

TeO, BaO

Sb203

La203

Ce203

Pr203

Sm203

Gd203

Nd203 Rb,O cs ,o RuO,

PdO Tho, UO,

Rh203

Sample 1

0.03 0.03 0.02 0.0 1 0.23 0.60 0.56 0.93 0.44 0.31 0.03 1.59 0.13 1.29 0.46 0.12 0.33 0.33 0.52

Sample 2 -

-

0.02

0.25 0.71 0.58 1.18 0.56 0.39 0.06 1.87 0.17 1 .oo 0.84 0.15 0.55

0.80

-

-

Table 6 RSFs for nuclear waste glasses with respect to silicon. Discharge voltage 1 kV with a corresponding current of 2 mA

Element

Si B A1 Na Mg Ca Ti Ba Ce Cr

This work

1 .oo 0.66 f 0.08 0.19f 0.07 0.40 f 0.05 0.78 L 0.07 0.24 f. 0.04 0.14f.0.08 0.23 f. 0.02 0.08 f 0.02 0.12f0.01

From ref. 27

1 .om 0.381 0.621 1.05 1 0.953 0.502 0.345 1.621 - -

Element

c s Eu Gd La Nd Ni Mn Mo Pd Pr

This work From ref. 27

0.52 f 0.08 5.96 f 0.15 0.03 f 0.01 0.04 f 0.01 0.04 f 0.01 -

0.20 f 0.04 0.914 1.24 & 0.15 0.878 0.19f0.02 -

0.09 f 0.02 -

0.04 f 0.01

-

-

-

-

-

Element

Rb Rh Ru Sm Sr Te Y Zr P U

This work From ref. 27

6.59 f0.20 2.720 17.68f0.20 - 28.02 & 0.2 -

0.04+0.01 - 0.20 f 0.03 0.854 0.36f0.02 - 0.03+0.01 -

29.46 & 0.2 -

0.28f0.05 -

0.02 & 0.0 1 0.282

Table7 Composition (YO m/m) of the two metallic nuclear alloys investigated

~~~

Alloy Um/m Zrm/m Ndm/m Pum/m

UNdZr 81 9 10 UPuZr 71 10

-

19 -

instance, titration was used for the determination of the total concentrations of uranium and plutonium and TIMS and ICP-MS, both combined with isotopic dilution analysis, were employed for the determination of the zirconium and neodym- ium contents. In Table 8 the ratios between the concentrations obtained by these techniques and GDMS analysis are given. As can be seen, the ratio was close to one, indicating good agreement between the GDMS concentration and the concen- tration measured with the other techniques. GDMS can there-

Table8 Ratios of the concentrations of the constituents of UZrNd and UPuZr alloys obtained from titration, TIMS and ICP-MS with the concentrations obtained from GDMS

TITR*:GDMS

1 1.03 1.06 2 1.03 1.01 3 0.99 0.99 4 0.98 1.01 5 1.03 0.98 6 0.99 - 7 1.04 -

8 1.03 -

9 0.99 -

10 1.00 -

Sample U Pu T1MS:GDMS ICP-MS:GDMS U Pu Zr Nd

1.00 1.02 1.01 -

1.01 1.00 0.99 -

0.99 1.03 1.03 -

1.03 1.04 1.02 - 1.00 0.98 0.98 -

1.00 - 1.02 1.02 - 0.98 1.03 - 1.04 1.02 - 1 .oo 1.02 - 1 .oo

* TITR = titration.

fore be used to determine the chemical composition of these alloys using RSFs obtained for pure uranium metal matrix.

For the determination of certain trace elements in the UZrNd and UPuZr alloys, RSFs obtained for uranium metal matrices were employed. The results obtained using this approach were in good agreement with those obtained from ICP-MS (see Table 9).

Zircaloy cladding materials

GDMS has also been used by other workers for the anaylsis of zirconium alloy^.^ In the present investigations, RSFs were obtained using two standard materials. The data are reported in Table 10 and compared with values in the literature.’ Quantitative analysis of zircaloy cladding material was per- formed on the basis of the RSFs (see Table 10) obtained in this laboratory for uranium metal previously measured by ICP-MS. The same specimens analysed by ICP-MS gave results in agreement with those obtained by GDMS. In Table 11 two examples are given. The RSFs were monitored over a period of 6 months and no significant variations were found.

CONCLUSIONS

GDMS can be successfully applied to the characterization of material of nuclear concern. Alloys of UPuZr and UZrNd and zircaloy cladding materials were analysed for main constituents and trace components. The RSFs used, obtained from the major component in the metallic form or from reference samples, were found to be in agreement with values reported in the literature. However, for more complex metallic alloy matrices, e.g., those containing minor actinides and REEs, investigations to calculate more precise and specific matrix

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Table 9 Trace element analysis of UZrNd specimens: comparison between results from ICP-MS and GDMS; n= 10

GDMS ICP-MS

Element Cr Fe Ni

Concentration/

25 145 77

Pi% g-' RSDl(%)

1.2 3 4

Concentration/

28 130 80

P8 g-' RSD (Yo) 2

2.5 3

Table 10 RSFs obtained for some elements in a Zircaloy matrix compared with literature values

RSF

Element

56Fe 19Sn

52Cr 60Ni

"*Hf 2 7 ~ 1

This work Reference values*

1.5-2.3 1.9 4.3-5.7 4.2 3.3-4.2 4.1 2.0-3.4 3.5 1.5-2.5 2.0 0.8-1.2 1 .o

*From ref. 9.

Table11 m/m) for two Zircaloy samples

Comparison between ICP-MS and GDMS results (in %

Sample 1 Sample 2

Element ICP-MS GDMS ICP-MS GDMS

Sn 1.06 0.996 1.25 1.27 Fe 0.227 0.297 0.212 0.226 Cr 0.101 0.099 0.094 0.093 Ni 0.0020 0.00 18 0.0030 0.0033

RSFs in order to improve the accuracy of the GDMS results are in progress. Of major interest are oxide-based non- conducting samples. It was found that the oxygen content of the sample matrix plays an important role in the analytical determinations of trace elements. The use of a getter metal, such as tantalum and titanium has been compared with the employement of silver. From the comparison of the RSFs obtained for some trace elements, it would appear that the use of titanium or tantalum gives a better sensitivity. Tantalum has also been tested as a secondary cathode. In the case of nuclear samples, because of their radioactivity, the use of a secondary cathode eliminates having to grind samples that are received as pellets and the risks of cross-contamination. Initial results have shown that tantalum acts as a getter also when used as a secondary cathode. For the analysis of nuclear-waste glasses by GDMS it was necessary to obtain matrix specific RSFs.

REFERENCES

Garcia Alonso, J. I., Thoby-Schultzendorff, D., Giovanonne, B., Koch, L., and Wiesmann, H., J. Anal. At . Spectrom., 1993, 8, 673. Crain, J. S., and Gallimore, D. L., Appl. Spectrosc., 1992, 46, 547. Garcia Alonso, J. I., Sena, F., Arbor&, Ph., Betti, M., and Koch, L., J. Anal. At . Spectrom., 1995, 10, 381. Stoffel, J. J., Wacker, J. F., Kelley, J. M., Bond, L. A., Kiddy, R. A., and Brauer, F. P., Appl. Spectrosc., 1994, 48, 1326. King, F. L., and Harrison, W. W., Mass Spectrom. Rev., 1990, 9, 285. Winchester, M. R., Duckworth, D. C., Marcus, R. K., in Glow Discharge Spectroscopies, R. K. Marcus, R. K., ed., Plenum Press, New York, 1990, ch. 7.

7

8

9 10

11

12

13

14

15

16 17

18

19

20

21

22 23

24

25 26

27

28

29

30

31

32

33 34

35

36

Duckworth, D. C., Barshick, C. M., and Smith, D. H., J. Anal. At . Spectrom., 1993, 8, 875. Barshick, C. M., Duckworth, D. C., and Smith, D. H., J. Am. SOC. Mass Spectrom., 1993, 4, 47. Robinson, K., and Hall, E. F. H., J. Met., 1987, 39, 14. Betti, M., Rasmussen, G., and Koch, L., presented at the Winter Conference on Plasma Spectrometry, San Diego, USA, 8-13 January, 1994. Betti, M., Applications of Glow Discharge Mass Spectrometry for the Direct Analysis of Non-conducting Nuclear Materials, EUR 16152 EN, 1995. Betti, M., Ray, I. L. F., Stalios, A., Walker, C. T., and Koch, L., presented at the International Nuclear Smuggling Forensic Analysis Conference, Lawrence Livermore National Laboratory, Livermore, CA, USA, 7-9 November 1995. Betti, M., Rasmussen, G., Hiernaut, T., Koch, L., Milton, D. M. P, and Hutton, R. C., J. Anal. At . Spectrom., 1994, 9, 385. Ohorodnik, S. K., and Harrison, W. W., Anal. Chem., 1993, 65, 2542. Ohorodnik, S. K., de Gendt, S., Tong, S. L., and Harrison, W. W., J. Anal. At . Spectrom., 1993, 8, 859. Matzke, Hj., and Vernaz, E., J. Nucl. Muter., 1993, 201, 295. Sanderson, N. E., Hall, E., Clark, J., Charalambous, P., and Hall, D., Mikrochim. Acta ( W e n ) , 1987, 1, 275. Vieth, W., and Huneke, J. C., Spectrochim. Acta, Part B, 1991, 46, 137. Woo, J. C., Jakubowski, N., and Stuewer, D., J. Anal. At . Spectrom., 1993, 8, 881. De Gendt, S., Schelles, W., Van Grieken, R., and Muller, V., J. Anal. At . Spectrom., 1995, 10, 681. Teng, J., Barshick, C. M., Duckworth, D. C., Morton, S. J., Smith, D. H., and King, F. L., Appl. Spectrosc., 1995, 49, 1361. Duckworth, D. C., and Marcus, R. K., Anal. Chem., 1989,61,1879. Duckworth, D. C., Donohue, D. L., Smith, D. H., Lewis, T. A., and Marcus, R. K., Anal. Chem., 1993, 65, 935. Shick, C. R., Raith, A., and Marcus, R. K., J. Anal. At . Spectrom., 1993, 8, 1043. Marcus, R. K., J. Anal. At . Spectrom., 1993, 8, 935. De Gendt, S., Van Grieken, R. E., Ohorodnik, S. K., and Harrison, W. W., Anal. Chem., 1995, 67, 1026. Milton, D., and Hutton, J. C., Spectrochim. Acta, Part B, 1993, 48, 39. Schelles, W., De Gendt, S., Muller, V., and Van Grieken, R., Appl. Spectrosc., 1995, 49, 939. Betti, M., Giannarelli, S., Hiernaut, T., Rasmussen, G., and Koch, L., Fresenius' J. Anal. Chem., 1996, 355, 642. Winchester, M. R., and Marcus, R. K., Appl. Spectrosc., 1988, 42, 941. Tong, S. L., and Harrison, W. W., Spectrochim. Acta, Part B, 1993, 48, 1237. Velazco, J. C., Kolts, J. H., and Setser, J. W., J. Chem. Phys., 1978,69,4357. Mei, Y., and Harrison, W. W., Anal. Chem., 1993, 65, 337. Lucuta, P. G., Verrall, R. A., Matzke, Hj., and Palmer, B. J., J. Nucl. Muter., 1991, 178, 48. Shimamura, T., Takahashi, T., Honda, M., and Nagai, H., J. Anal. At . Spectrom., 1993, 8, 453. Mykytiuk, A. P., Semeniuk, P., and Berman, S. , Spectrochim. Acta Rev., 1990, 13, 1.

Paper 6/00400H Received January 18, 1996

Accepted May 7, 1996

860 Journal of Analytical Atomic Spectrometry, September 1 !)96, Vol. 11

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