Determinación Espectográfica de Boro y Silicio en

J. E. N. 269
Sp ISSN 0081-3397
Determinación espectográfica de Boro y Silicio
en Tetrafluoruro de Uranio: Estudio de las
reacciones químicas que tienen lugar en el
cráter del electrodo al utilizar ZnO
como supresor de la excitación del Uranio.
por
Fernando A. Alduán
Carlos Capdevila
Miguel Roca
JUNTA DE ENERGÍA NUCLEAR
MADRID , 1 9 7 3
Toda correspondencia en relación con este trabajo debe dirigirse al Servicio de Documentación Biblioteca
y Publicaciones, Junta de Energía Nuclear, Ciudad Universitaria, Madrid-3, ESPAÑA,
Las solicitudes de ejemplares deben dirigirse a
este mismo Servicio.
Se autoriza la reproducción de los resúmenes analíticos que aparecen en esta publicación.
Este trabajo se ha recibido para su impresión en
Junio de 1973.
Depósito legal n2 M-21936-1973
1.
INTRODUCTTON
For the spectrographic determination of impurity elements in
UF , samples are usually converted into U 0 through pyrohydrolysis.
By employing this conversión procedure, tne ordinary carrier distillation methods of uranium analysis can be used (1). The procedure
is not feasible, however, for impurity elements which form highly
volatile fluorides such as boron and silicon, that are lost during
the pyrolitic transformation. Methods of direct spectrographic
analysis of UF either with no carrier (2) or with Al 0 to suppress
the volatilization of uranium (3) have been described in the literature. In the former case the exposure is made until a white fiare
of uranium appears in the are. With this method we have obtained a
poor reproducibility for silicon because uranium spectrum appears
before silicon is completely volatilized. In the latter method the
limit of detection of boron is 0.5 ppm. Since in our case a lower
limit was necessary (0.2 ppm), a number of materials were considered
to delay uranium volatilization and imp'rove sensitivity.
In a previous work (4) the mixture Ga 0 - Y O
led to a limit
of detection of 0.3 PP^i boron, the interference by the Ga 2500.2 A
on the B 2497.7 A line prevenís a lower limit. In order to overeóme
this, a mixture AgCl - Y O
was also considered, but a high uranium
background was obtained. With the use of ZnO the volatilization
times of both boron and silicon remain practically unchanged (about
10 seconds), while the volatilization of uranium is delayed and the
uranium intensity becomes lower (Figure 1 ) . In this communication
we describe the results obtained with this uranium spectrum suppressor and the investigation of the thermochemical reactions oceurring
in the electrode cráter and accounting for the delay in the uranium
volatilization.
2.
EXPERIMENTAL
The apparatus and operating parameters used in this study are
listed in Table 1. In order to ascertain which is the best concentration of ZnO to provide the highest sensitivity, the intensity
ratios of line to background in the range 10-50% ZnO were obtained
(Table 2 ) . A UF sample containing 0.3 ppm B and 15 ppm Si was
employed. Since for silicon the lowest limit of detection was not
necessary, it can be concluded from Table 2 that the optimum ZnO
concentration is 35%.
Standards were prepared by adding Johnson Matthey spectroscopically puré oxides of the impurity elements to high purity UF.. The
volatilization-excitation curves of boron and silicon with these
synthetic standards are similar to those obtained with natural sam-
•2-
ples, showing that the volatilization process is the same in both
cases.
DC are currents lower than 10 A delay the excitation of uranium,
but also decrease the intensities of the impurity element lines, so
that sensitivities are not improved and reproducibilities become
unsatisfactory.
Figure 2 shows the working curves o£ both elements. The detection limits are 0.1 ppm boron and 5 ppm silicon, the latter caused
by residual impurity in the UF matrix. With a sample containing
0,3 ppm boron and 15 ppm silicon, the standard deviations obtained
by 20 repetitive measurements are _+ 9.9% and +_ 9.6%, respectively.
3.
STTJDY OF THE REACTIONS IN THE ELECTRODE CAVITY
A research was undertaken with the aim o£ gaining some insight
concerning the reactions in the anode cavity, accounting for the
delay in the volatilization of uranium when ZnO is added.
The volatilization-excitation curves o£ uranium in UF and of
uranium and zinc in the mixture UF -35% ZnO were obtained (Fig. 3
and 4 ) . An A.R.L. Production Control Quantometer was employed
(rj 4472.3 A and Zn 3345.0 A lines). The charges were 65 mg of
UF and 100 mg of UF -35% ZnO. As it can be seen, uranium in UF
starts volatilizing at 6 seconds and at about 200 seconds is enti_
rely volatilized. With the addition of ZnO, uranium volatilization is delayed, intensity is lower and the curve shows a minimum
at about 180 seconds and then increases again and reaches a higher
valué than in the first stage of the curve. The minimum coincides
with the depletion of zinc.
X-ray powder patterns were obtained after DC are excitation
times of 5, 10 and 20 seconds. A 12046 B/3 Philips Norelco instrument with nickel-filtered copper radiation (35 KV, 15 mA, 5
hours) was employed. In the case of UF samples, only its
spacings were obtained while with UF -35% ZnO samples, a mixture
of UF , U0 and ZnO was identified. It was also found a line
with a "d" spacing of 1.74 A belonging to an unidentified compound. The intensity of this line increases with time, while
the intensity of UF lines decreases, Following this it can be
assumed that in the presence of ZnO, UF is converted into U0
and an unidentified compound.
In order to investigate in more detail the reactions oceurring
in the electrode cavity, the volatilization-excitation curves of
uranium and zinc in U Ofi-35% ZnO and ü 0.-39% ZnF mixtureswere
obtained (Fig. 3 and 4 ) . The latter mixture provides approximate_
ly the same fluorine and zinc concenrrations as the UF -35% ZnO
mixture. As it can be seen, volatilization of uranium in the
U 0n-Zn0 mixture begins at about 130 seconds when zinc is just
completely depleted. With the U 0 -ZnF mixture, except for an
initial peale probably caused by the momentary formation of UF,,
curves are similar to those obtained with the UF -35% ZnO mixture.
The X-ray powder pattern of the cráter residue after a 20 second
DC are excitation of the U 0 -39% ZnF mixture is similar to that
obtained with the UF -35% ZnO mixture, including the 1.74 A line.
With both mixtures the patterns after a 120 second excitation
indicate a high UO concentration, some ZnO and the 1.74 A line,
although weaker than in the 20 second pattern, while the UF
lines are not found. After the whole volatilization of zinc (200
seconds), when the volatilization of uranium reaches the highest
-4-
intensity, the X-ray powder patterns show thát for both mixtures the
cráter residue contains a high concentration o£ UO and U 0
the
1.74 A line being absent. Finally from the X-ray powder patterns
of the U Og-35% ZnO mixture after excitation periods o£ 90 and 170
seconds- corresponding to before and after the zinc depletion, respectively - it is shown that the electrode residue contains UO and
ZnO, and U 0 0 0 and UO., respectively, while the 1.74 A line does not
Jo
¿
appear.
The chemical determination of the fluorine concentrations in the
electrode residue after 0, 20, 120, and 200 second DC are excitations
of the UF -35% ZnO mixture gives valúes of 15, 14, 6 and <0.1%, res
pectively.
•5-
4.
CONCLUSIÓN
From the above, it may be concluded that the compound with
the 1.74 A line is only formed in the presence of fluorine, uranium
and zinc, The apparent absence of other "d" valúes corresponding
to this compoLind may be due to overlapping of lines of other subs—
tances present in the samples. Since after a 120 second excitation
of the UF^-35% ZnO mixture, the fluorine content in the electrode
cráter is '6% and the UF spacings are not present, it is apparent
that the 1.74 A line substance is formed by fluorine, uranium and
zinc. This assertion is supported by the presence of the UF lines
in the X-ray powder pattern of a UO -UF mixture containing 6%
fluorine.
To sum up briefly, the uranium volatilization delay in the UF
after the addition of ZnO, that enables the determination of boron
and silicon with both good sensitivity and precisión, can be
explained as a consequence of the formation of UO and a fluorine,
uranium and zinc compound in the electrode cavity, both less volatile than UF . This allows t.
the uranium intensity in the uranium
volatilization curve to be lo
lower and the complete uranium volatili
zation to take a longer time.
REFERENCES.
1.
Scribner, B.F., Mullin, H.R.: J. Res. Nati. Bur. Std. 37, 379
(1946),
2.
National Lead Company of Ohio, Ed., Analytical Chemistry
Manual of the Feed Materials Production Center, Report TID7022, Vol. II, December 1964.
3.
Podobnik, B., Spenko, M,: Anal. Chim. Acta. 34, 294 (1966).
4.
Capdevila, C., Roca, M., Alvarez, F.: Anales Real Soc. Españ,
Fís. Quím, (Madrid), Ser.B, 63, 289 (1967).
-6-
TABLE
I
Apparatus and excitation parameters
Electrodes:
Scribner type (Ultra Carbón 1990 and 1992).
Analytical gap:
4 mm
Charge:
100 mg tamped and pierced with a venting tool.
Excitation unit:
Jarrell-Ash Varisource, DC are 10 A.
Spectrograph:
Hilger Littrow automatic large, quartz optics.
Illumination:
Are image focused on slit by 64 mm focal length
lens.
Wavelength range:
2200 - 2800 %.
Slit:
22 u wide and 1 mm high.
Preburn:
None.
Exposure:
10 sec,
Emulsión:
Kodak S.A. No. 1 .
Developer:
Kodak D-19b, 21° C, 4 min.
Fixer:
Kodak F-5, 21° C, 4 min.
Píate calibration:
Two-step method, iron are exposure.
Microphotometer:
Jarrell-Ash digital comparator densitometer.
Analytical lines:
B 2497.7 X
Si 2435.2 X
TABLE II
Variation of the intensity ratio o£ line to background
Concentration of ZnO (%)
10
18
25
35
50
B
1 .1
1 .3
1 .7
2.3
2.1
Si
1 .2
1 .4
1 .9
2.5
2.7
Element
o
Fig,
o
10
15
20
TIME(SECONDS).
1» - Volatilization-excitation curves for boron,
aiiicon and uranium.
BORON
0,1
0,2
0,5
\
2
5
!
ID
2. - Working curves.
—
^
¡
20
.
Fig.
j
CONCENTRATIOIM
IN PPM
T~1i
50
Ii
i T~T
100
o
-o
O
•£
o
-8 OoÜJ
-h-
O
a
tí
O
\
o
a)
Vi
3
a
o
y
1
,\
\
N
+
O
\
i
\
w\
M
i
ñ
o
0
>
00
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CD
A1ISN31NI
90
0
10 20
Fig.
30
40
50
/S
60 / 120 130 1>4o 1 5 0 1 6 0 1 7 0 1¿0 190 2(
TIME (SECONDS)
4. - Volatilization-excitation curves for zinc.
J . E . N . 269
J.E.N. 269
Junla de fnergfa Netlear, División de Química Analítica, Hadtid.
"Determinación espectrografica de box*o y silicio
en tetrafluoru.ro de uranio: Estudio de las reacciones
químicas que tienen lugar en el cráter del electrodo
al utilizar ZnO como supresor de la excitación del
uranio",
A. Al [LAN, F . ; C A I I I V I I A , C ; ROCA, M. ( 1 9 / J ) / p p . 'i l i g s .
Si ba desarrollarlo un miioi'o di di le m i nación di tra¿as di bote y s i l i t i o n i
lunla di frurcía Nuclear, Pivisión de Qi íntica Analítica, Madrid.
" D e t e r m i n a c i ó n e s p e c t v o g r a f i c a de b o r o y s i l i c i o
en t e t r a f l u o r u r o de u r a n i o : E s t u d i o de l a s r e a c c i o n e s
q u í m i c a s que tienen l u g a r en e l c r á t e r d e l e l e c t r o d o
al utilizar 1 ZnO como s u p r e s o r de l a e x c i t a c i ó n d e l
u r ani o " .
A. AIDUAN, [".; CAPFfVILA, C ; ROCA, H . ( 1 9 / ¡ J 7 p o . A f i g s .
Si h a d c e a n o l l a n o m móloc'o di d i Le rmí n a c i ó n di l r a / a c d i b o i o y s i l i c i o en
L t r a d i i o i n i o di m a n i ó , nn i l qiM si M i l L a óxido dt cinc paro o i s m i n i i r la
l e l i a l Inorní o di u i v n i o , en i l qi'i s1 i l i l i
v i J 1 a L i 1 i ación u\ 1 iitanin y c o n s i q i i r
volaLl 1 L o c i ó n ct I uranio y ccn'igí i r sui c ibilidc'd> < i ](vaciar. Si han isltidiado
c! ri^-i bi 1 i (jotk <= t k . a d a s . Si han i H u d i a d c
l a " u a L í i o p . s l t imuq¡ ímiccr cu i Si i r i d u a n t n i l c r á l u
di 1 i ' l i c l r o d o
di.ranli
las i i a i t i o r i s
a ÓMUO di e l nc [ a t a disminuir l a
l i tinGqi,ínticas qui si p r o d e i n m i l cráb r di 1 electrodo
duanli
I J di tcar o* ilt a r t o , di di.c'i i'ndusi que dan lugar a l a formación de IIÜT V I.'. • I I
la descarna di arce, dcducii'ndo> qui dan I ,gar a la foimaciór db UÜp y di nn
I ompiíi
(ompiislu di f l i ' u r , uranio / c i n i , arabo1 minos
l o di 11'oí, ni diiio / C Í I R , ambos im ñus . o l a l i l i s qm i l l i l r a l l
ur ro
r|i ui m í o .
J.E.N. 269
J . E . N . 269
' u n í a di I iii i g í a N i . c l i a i , D i v i s i ó n di Qi í m i c i A n a l í t i c a , M d i l r k 1 .
"Determinación espectrográiica de boro y cilicio
en tetrailuoruro de uranio: Estudio de las reacciones
químicas que tienen lugar en el cráter del electrodo
,il utilizar ZnO como supresor de Ja excitación del
uranio",
A. Al 1)1/N, L ; (ArriVILA, L ; ROrA, H. 119/ I / <,(. k \hr~.
Q
'• l i t di J i i o l l d d u up nú'I oí'u di d> h rininación di l i a u . di boi r y
11 I r j f I ior it o di ir J I I Í O , i p i I q i
üliiili
c
i
t i I i<.a oxide di c i n i p u • d i min i r 11
ti >on i n 1 ii tnio / cen • yu i t si n >i bí l i i k i ' t " i l i n d a . Si li m i nuli i
i m i l.
nula di I nei gía Nucli w, Di,irión ai Q íniio Analítica, Madrid.
" D e t e r m i n a c i ó n e&pec t r o g r j fie a de b o r o y s i l i c i o
en t e t r a i l u o r u r o de u r a n i o : E s t u d i o de l a s r e a c c i o n e s
q u í m i c a s que tienen l u g a r en el c r á t e r d e l e l e c t r o d o
al u t i l i z a r ZnO como s u p r e s o r dt la e x c i t a c i ó n d e l
uranio".
A . A l CUAN, I . ; C A P D I V I ' A , C ; ROCA, M . ( I ' l 7
Si l u d í
iluio ui
i i i iiiiooi
i tiiiuq m i n a qi't i ptml n n M I I H I ' I I » ! I i l i c i ' i i'i K I '
I i k "i i i o
i ii i i, i 1 f i ( i i ni li i' q ii i i ii i I n u i I i lur II u i un i! ni I '
i'i ¡<
I i lili ii H 11 ' I 'i I , i i i l u
111 l , illbu 'II i u ni l¡ 1 I
i) i i I I I ¡ 11 I 01 iii
1
o l á l i l i s qiu i l l i I r a f l loruro
de uranio.
tirrifliioi
olalili
I \
l u il
>,i
t r i u , n >1 q11 °i
u i o n di I ni ni ¡ o
> 111 u n í
1 i1
/
. k fiqt.
J I r o l lado m mi lodo dr ik I. i ininat 101 ri I r i . a
' • 11 j i , í m i c t
11 , 1 1
1 011 1 qi U
i|i
h i1 1 1 n i 1 "
'lili
i nc i b i I t i ' u 1
1 ni Lth'ti
J< boi o ,
iliiioui
i o<ulo r'i cinc p >> •"• i b ' i n i n i i i I d
• '1 n'a . Si han 1 "tinliado
n 1 n 1 I ' ' i t i r di 1 1 h t h udo d i n CÍn' •
q 1 1 an 1 m a l
1 l a 1011n.u1011 ti
ii i
d i l ; , 1J1 ' n
te i i a l I lor i re
J.E.N. 269
J.E.N. 269
Junla do Lnergía Nuclear, División de Quínica
Junta de Lnc-rqía Nuclear, División de Química Analítica, Madrid
Analítica, Madrid
"Spectrographic determination oí boron and sili-
"Spectrographic determination oí boron and sili-
con in uranium tetrafluoride: Study of the chemical
con in uranium tetrafluoride: Study of the chemical
reactions in the electrode cavity when ZnO is used
reactions in the electrode cavity when ZnO is used
as a uranium excitation
as a uranium excitation
suppressor"
suppressor11
A. ALDLAN, C ; CAPDLVILA, C ; ROW, M. (1973) 7 p p . k licjs.
A. AIUUAN, í".; CAfOCVILA, C ; ROCA, H. (1973) 7 p p . h f i g s .
A im Ihod has bien dovelcped í o r de termining traces of boron and silicon in
tiranium tclrdfluorido. Use i s maclt oí zinc oxidi lo decrcase Ihc v o l a l i l k a t i o r
of uranium E.nd achiivo high s o n s i l i i ñ l i e s . fhu llicrmochemical rcactions. which
oct'n in Ihc ánodo caví ly durinc Ihti arcing proass ha ve buen invosligated.
UUo and a uranium, zinc and fluorinp tompound, bolh I o SÍ. v o l a l i l e Ihan uranium
IptraFluoride, are forntfd.
A im.th.od lias boen developcd for detormininc traces of boron and silicon i n
uranium lolrafluoride. Use i s made of zinc oxide lo decrcase I he v o l a t i l i / a l i o n
of uranium and achieve high sensi Li\1 Lies. The thormcchemical rcactions uhicb
oceur in Ihe ánodo cavíly durinq the arcinq procest ha» o been investigaied.
Uüp and a uranium, zinc and fluorinp compound, bolh less vola t i le than uranium
lelralluoride, aro forniod.
J.E.N. 269
J.E.N. 269
lunla di fnergía N i d o a r , División dr Químicr Analítica, ñair'ui
"Spectrographic determination oí boron and silicon in uranium tetrafluoride: Study oi the chemical
reactions in the electrode cavity when ZnO is used
as a uranium excitation suppressor"
A. AHIJAN, L ; CATDfVItA, C ; RUCA, H , t l 9 " M 7 p i . i f i g . .
A melhod lias been d e u l o f i d
f o r dclctniininc
I r o i t ? o l toron _nd s i l i c o n i n
' raniíim l e l í d f l l o r i r i i . U&i i s madi of z i n c oí i di
i o í uranium and acliii M high s u i s i l i v i t i e s .
l o di (r» ast Ihe v o l a t i l i / a l i o n
Di. Un rmocbt mi cal r e a c l i o n s which
c
Junla de fnerqía Nuclear, División de Química
Analítica, Madrid
"Spectrographic determination oí boron and silicon in uranium tetrafluoride: Study oí the chemical
reactions in the electrode cavity when ZnO is used
as a uranium excitation
suppressor"
A. ALCLAN, ! \ ; CAI'DIVILA, C ; ROCA, M. (197 0 7 p p . 'i f i g s .
¡
A m e l h o d bjfí b e e n d i . < l o p i d f o r d c l e r i p i n i n g I r a c a s o f boi on a n d s i l i c o n i n
i i r e n i u m U t r a í L o i i d e . Usi i s made o f i n i o x i d e l o d t c r e a s i i h c v o l a l i l i z a l i o n
'oí u r a n i u m a n d a c h i l é h i g h s m s i l i v i l i i t .
Ihi I h i r m o t h i m ; c a l r t a r l i o r 0 i»hich
oceur i n Un anotk ( a i l > durinq Ihe a i c i n g pi oci s ha i- been invi s t i q a l c d .
loccur i n Un anoi'r c a v i l v dui inq Ihi aicincj p r u d ~° ha be n i n v c s l i q a L d .
UO2 onrl i iii'inium, zinc atul f h ' o r i m 1 Lompound, bolh ] i s \ o l a l i k
Uü^, and a uranium, / i r t e and l l u o r i n i
t i I r a l I mi i d i , ai 1 formod.
Ihan uraniim
I'I I r a l l u o r i d c , are formed.
coiri.oind, bolh k t
volalik
than uraniiii