NUREG/CR-1736
LMF-78
Comparison of Physical Chemical
Properties of Powdersand Respirable
Aerosols of Industrial Mix(~d
Uranium and Plutonium de Fuels
Prepared by A. F. Eidson
Inhalation Toxicology Research Institute
Lovelace Biomedical and Environmental
Prepared for
U.S. Nuclear Regulatory
Commission
Research Institute
NOTICE
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Available from
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and
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Springfield,Virginia 22161
NUREG/CR-1736
LMF-78
RH
Comparisonof Physical Chemical
Properties of Powdersand Respirable
Aerosols of Industrial Mixed
Uranium and Plutonium Oxide Fuels
Manuscript Completed: October 1980
Date Published: November1980
Prepared by
A. F. Eidson
Inhalation ToxicologyResearchInstitute
Lovelace Biomedicaland EnvironmentalResearchInstitute
P.O. Box 5890
Albuquerque, NM87115
Prepared for
Division
of Safeguards,
Fuel Cycle and Environmental
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory
Commission
Washington,
D.C. 20555
NRC FIN No. A1031
Research
ABSTRACT
The purpose of these studies
termining
the biological
respirable
is to delineate
fate of mixed-oxides if
aerosols was also studied.
physical
inhaled.
Four representative
and chemical factors
The similarity
important
in de-
between powders and
mixed-oxide powders were obtained from
fuel fabrication
enclosures. Aerosols of the powders were regenerated in the laboratory and
collected for analysis. Crystal structure analysis of powders and aerosols showed that material
from processes prior
from the pellet
solid
to pellet
grinding
sintering
consisted of discrete
step were in a (U,Pu)01.96
solid
PuO2 and UO2 phases while materials
Incorporation
of Pu into
solution.
with UO2 caused an increase in the Pu dissolution
rate in vitro. Infrared spectral
analysis showed that the surfaces of aerosol particles contained adsorbed CO2 and H20, suggesting
that the reduction caused by sintering
was partially
reversed at the surface. X-ray diffraction
results
solution
indicated
that analysis
spectroscopy results
indicated
of powders is sufficient
that isotopic
from steps prior
the aerosol form. Alpha
composition of aerosols from steps following
comminution could be obtained from powder analysis.
rials
to characterize
powder
An adequate estimate might be made for mate-
to powder comminution, but aerosol analysis
is preferred.
iii
TABLEOF CONTENTS
Page
ABSTRACT
..................................................................................
iii
LIST OF FIGURES............................................................................
vi
ACKNOWLEDGEMENTS
..........................................................................
vii
1.
INTRODUCTION
.........................................................................
1
2.
MATERIALSANDMETHODS
................................................................
1
2.1.
Materials
i
2.2.
Aerosol Generation .........................................................
2
2.3.
Elemental and Isotopic
2
2.4.
X-Ray Diffraction
2.5.
Infrared
2.6.
Electron Microscopy ........................................................
4
2.7.
In Vitro
4
3.
4.
..................................................................
Analysis ............................................
..........................................................
3
Spectroscopy ......................................................
Dissolution
4
.......................................................
RESULTS
...............................................................................
5
3.1.
Aerosol Characteristics
5
3.2.
Crystalline
3.3.
Infrared
Absorption ........................................................
7
3.4.
In Vitro
Dissolution
9
Properties
and Isotopic
Composition ...........................
.....................................................
5
.......................................................
DISCUSSION
...........................................................................
11
4.1.
Comparison of Powder and Aerosol Isotopic
4.2.
Surface Composition ........................................................
4.3.
Comparison of Powder and Aerosol Crystal
4.4.
Relationship
of Dissolution
Composition ......................
Properties
11
11
........................
to Aerosol Matrix ..............................
11
12
5.
BIOLOGICALCONSIDERATIONS
............................................................
12
6.
CONCLUSIONS
..........................................................................
13
7.
REFERENCES
...........................................................................
15
LIST OF FIGURES
Page
Figure 1. Transmission electron
micrograph of 750°C treated
aerosol sampled during an inhalation
Figure 2. X-ray powder diffraction
patterns
U-Pu mixed-oxide
exposure of a Rhesus monkey ...............
of A) 750% heat-treated
mixed
UO2 and PuO2 powder obtained from the ball milling process at HEDL
and B) 1750°C heat-treated (U,Pu)01.96 obtained from the pellet
grinding process at HEDL.......................................................
Figure 3.
Infrared spectrum of mixed PuO2 and UO2 powders containing organic
binders and obtained from the pellet pressing operation at B&W.................
Figure 4.
Infrared spectra of 1750°C heat-treated (U,Pu)01.96 materials from
the pellet grinding operation at HEDL; a) powder, b) aerosol ...................
Figure 5.
Infrared spectra of a) pure KBr and b) 850°C heat-treated
blending operation at B&W......................................................
Figure 6. Comparison of Pu, Am and U dissolution
PuO2 from the
rates from aerosol samples of
mixed PuO2 and UO2 containing organic binders in 2 M HNO
3 ......................
Figure 7. Comparison of Pu, Am and U dissolution
from aerosol samples of
1750°C heat-treated
(U,Pu)01.96 in 2 M HNO
3 ....................................
vi
ACKNOWLEDGEHENTS
The author wishes to acknowledge the friendly
Engineering and Development Laboratory
cock and Wilcox Companyin obtaining
cooperation
of Dr. R. C. Smith of Hanford
and Mr. ~Hke Austin and Mr. Harvy Rosenberger of the Bab-
the materials
for these studies.
The author wishes to express his appreciation to Drs. G. M. Kanapilly, R. A. Guilmette, J. A.
Mewhinney and E. J. Graeber for helpful discussions during this work and to Hr. K. Warner, Mr. P.
Palmer and Hs. B. Allmer for
technical
assistance.
The author also wishes to thank Mr. G. J.
Newton and Drs. D. L. Lundgren, D. E. Bice, B. A. Muggenburg, N. D. Stalnaker,
R. O. McClellan for reviewing
B. B. Boecker and
the manuscript and to Mr. E. Goff for preparing the illustrations.
vii
1.
INTRODUCTION
Large amounts of uranium and plutonium oxide powders are processed to produce fuel
uniform composition and size to conform to design specifications
reactor
development program. Many of the steps require
to 50 kg plutonium,
(Ref.
1,2).
worker.
in glove box enclosures and result
An accidental
considered in this
that would disperse powders or aerosols without
might include
a slow leak of particles
of
for the liquid-metal-fast-breeder
manual handling of powders, including
up
in airborne plutonium in the enclosure
leak from the enclosure might result
The type of accident
pellets
report
in an inhalation
exposure to
was assumed to be a non-castrophic
changing their
chemical properties.
through a torn glove or a rupture
release
Such releases
of a glove box releasing
the general contents.
In an accidental
ations
human exposure, valuable information
can be obtained by analysis
with different
of materials
chemical forms and process histories
atmosphere that might conceivably
be identified
powders that relate
material.
In practice,
it
worker, since such accidents
properties
of respirable
of powders collected
Objectives
important
3).
Physical
from
of similar
can then be used to predict
the biolog-
exposure.
would be obtained by analysis
is extremely difficult
sized particles
of the aerosol form of the powdered
to sample the actual aerosol
included
in powdered fuel
from a glove box where an accident
in determining
can, however,
using information
and chemical properties
are rare and cannot be anticipated.
of the studies
mixtures
of each exposure
in an accident
an accident
consider-
of actinide
I) precludes andlysis
to the metabolism of inhaled actinides
The most useful information
fuel
(Ref.
of events surrounding
programs (Ref.
consequences of an accidental
to health protection
The wide variety
The box or boxes implicated
based on a reconstruction
area and personnel monitoring
ical
occur.
related
involved.
inhaled by a
must be shown then, whether
materials
are similar
to those
occurred.
described here are to characterize
the biological
It
fate of industrial
physical
and chemical properties
mixed-oxide aerosols that might be
inhaled by a worker and to determine the degree of similarity
in properties
of powders and their
aerosols.
The studies
trial-grade
are part of an on-going program designed to assess the dose patterns
plutonium aerosols inhaled by laboratory
laboratory
produced aerosols.
Specific
process steps that are representative
cation scheme (Ref. 1) and have the potential
plutonium (Ref.
had settled
2) were selected.
on surfaces
these powders for physical
Properties
included
aerosol characteristics,
related
materials
in selected
to deposition
and dissolution
This report
materials
for release of significant
composition,
at the Hanford Engineering
of the inhaled
properties
and
from
exposures of laboratory
plutonium aerosols studied
of crystalline
and non-crystal-
characterization
of samples of mixed-oxide fuel
and Development Laboratory (HEDL) at Richland,
and at the Babcock and Wilcox (B&W) fuel fabrication
2.
fabri-
of airborne
rate.
focuses on the physical-chemical
collected
of the fuel
quantities
using
that were produced by normal operations
and retention
isotopic
of indus-
studies
glove boxes. Aerosols were regenerated
and chemical analyses and use in inhalation
animals.
line materials
Airborne
were collected
animals compared with similar
facility
at ParKs Township, PA.
MATERIALSANDMETHODS
2.1.
Materials
All
boxes and will
history
materials
be identified
(Table I).
were powders produced by normal operations
throughout this
report
that had settled
in glove
by the source, composition and temperature
Table 1. Industrial
mixed uranium and plutonium oxide fuel
for study
History of
PuO
2
Chemical
Source a composition
d
B&W
Pu02
materials
collected
Characteristics
cGSD
~,IADb (~m)
Process step
850°C
Blending
2.73±0.16
1.95±0.09
e
HEDL
UO2 + Pu02
750°C
Ball Milling
2.32±0.24
1.74±0.04
B&W
UO2 + Pu02
f+ Binders
850°C
Pellet
Pressing
1.73±0.63
2.61±0.69
HEDL
(U’Pu)01 ¯
1750°C
Pellet
Grinding
2.60±0.13
2.35±0.09
to shipment to B&W for
asampling site. All PuO2 was prepared at HEDLprior
further processing.
bActivity median aerodynamic diameter
CGeometric standard deviation
dBabcock and Wilcox Fuel Fabrication
Facility,
Parks Township, PA.
eHanford Engineering and Development Laboratory, Richland, WA.
fSterote~ and Carbowax~ binders added to facilitate
pellet pressing.
The B&WPuO2 850°C powder was blended from PuO2 lots prepared at HEDLby calcining
the plutonium oxalate salt in air at 750°C and later calcining at B&Wto 850°C to ensure uniformity
of feedstocks.
The HEDLUO2 + PuO2 750°C powder was composed of calcined PuO2 mixed
with UO
2
powder and ball milled to reduce the average particle
size. The B&WUO2 + PuO2 + Binders 850°C
powder consisted of mixed-oxide powders that were mixed with Sterotex~)and Carbowax~ binders and
pressed into fuel pellets to be sintered. The HEDL(U,Pu)OI.96 1750°C powder was produced by the
centerless grinding of the pellets sintered for several hours at 1750°C in a reducing atmosphere
(8% 2 +92% Ar) to for m a s ub-stoichiometric, mix
1.96:1.
2.2.
ed-oxide wit h an oxygen-to-metal rat
io of
Aerosol Generation
Aerosols were generated from the powders to provide exposure atmospheres as part of
concurrent
inhalation
toxicity
studies
of nuclear fuel
aerosols in laboratory
biss powder blower was used to generate aerosols directly
steps that might alter
flowing
agitated
The generator,
tribution
obtained for electron
2.3.
(Table I).
Point-to-plane
microscopy (Fig.
Elemental and Isotopic
electrostatic
on membranefilters
were dissolved
HF, evaporated to dryness and dissolved
Plutonium-236 (101 dpm) was added as a tracer
for
size dis-
samples were also
Analysis
concentrated HNO
3 solution containing
stock solutions for further analysis.
of the actinides
5) for particle
precipitator
to the
I) (Ref.
Powder specimens and aerosols collected
to separation
500-700 mg
(Ref. 4) and delivered
Exposure aerosols were sampled using cascade impactors (Ref.
determinations
containing
water bath and aerosols were produced in air
at ~ 2 Ipm. Aerosols were passed through a 85Kr deionizer
animals.
A DeVil-
from dry powders to avoid pre-treatment
the chemical form of the materials.
of powder, was placed in an ultrasonically
animals.
alpha spectroscopic
to aliquots
analysis.
in 2 M HNO
3 to form
of stock solutions
Separation
in a
prior
of Pu and Am was
Figure 1. Transmission electron micrograph of 750°C treated U-Pu mixed-oxide
during an inhalation exposure of a Rhesus monkey.
aerosol sampled
accomplished by ion exchange. Plutonium in the separated fractions
was electroplated
on stainless
steel planchettes for alpha spectroscopy (Ref. 7). The alpha energy spectrum was measured using
silicon
surface barrier
detector
processed by a multi-channel
placed i cm from the source. Signals
analyzer (Princeton
channel. Under these operating
conditions,
peak maximumwas 30 keV. The efficiencies
using standard electroplated
236pu was 76 ± 1%.
were
Gamma-TechCo.) adjusted to measure i0 keV per
the resolution
of surface
expressed as the full
barrier
detectors
sources placed I cm from the detectors.
The activities
from the detector
width at one-half
were determined to be 0.12
The chemical recovery of
of 241pu and 241Amwere determined by liquid
scintillation
counting.
A stock solution was shaken for 35 minutes with an extractant scintillation
solution (Ref. 8).
The 241pu beta activity
and 241Amalpha activity
were measured using a Packard Tri-Carb Model
scintillation
counter.
The beta counting
efficiency
a reference standard and the alpha counting efficiency
2.4.
was determined to be 31% using 3H-toluene as
was 98%.
X-Ray Diffraction
Powder specimens were prepared in a glove box enclosure by application
®
pension of the sample and acetone to a silver foil fixed to a glass microscope slide
cement. Three coatings
slide.
The slide
of a 10% cement solution
was covered with acetate fiber
an area of glass sufficient
of a suswith Duco
in acetone were applied to both sides of the
tape so that only the area to be irradiated
for mounting in an automated diffractometer
and
remained exposed. The
specimen was wiped with cotton and the swab was monitored to determine that containment was
complete. Additional
coats of cement solution
were applied
as needed. This procedure provided
complete containment for several weeks. Specimens of aerosols collected
filters
on silver
membrane
were prepared in the same way.
Specimens were analyzed using a Philips
Model APD-3501 automated powder diffrac-
tometer equipped with a copper anode X-ray tube and a graphite
crystal
monochrometer. Corrections
for systemic errors
were made using the method of Nelson and Riley (Ref. 9). Unit cell dimensions
were determined by a least squares fit of high angle (20 > 75° ) diffraction
data taken with CuKa
radiation
(h = 1.54056 A) (Ref. 10).
2.5.
Infrared
Spectroscopy
Desiccated,
spectral
grade KBr and mixed-oxide powders were mixed by grinding
a mortar and pestle
in a glove box. Specimens were pressed at 20,000 psi for 5 minutes.
particles
on membranefilters
filter
collected
using a glass plate.
infrared
during animal inhalation
A correction
for the contribution
spectrum was made using the spectrum of pure filter
spectra were measured using a Perkin-Elmer
Model 621 grating
with
Aerosol
exposures were scraped from the
of removed filter
material
material
to the
mixed with KBr. Infrared
spectrophotometer.
Samples were
stored with desiccant in sealed jars.
2.6.
Electron Microscop£
Electron
electrostatic
photomicrographs of aerosol particles
precipitator
In Vitro
2.7.
were obtained using a Hitachi
collected
by a point-to-plane
HU-IIC transmission
microscope.
Dissolution
Samples of each aerosol used in the exposure of laboratory
on membranefilters.
electron
A segment was cut from this
filter,
placed in a filter
animals were collected
sandwich assembly
(Ref. Ii) and placed in 200 ml of 2 M HNO
3 at room temperature. The solvent was not stirred.
This system retained particles
between the two filters
while allowing free diffusion
of the
solvent
and solute.
The solvent
solvent
was changed periodically
was changed every hour for the first
for 60 days as shown by data points
and americium were separated (Ref. 8) and the activities
tillation
aliquot
counting.
Uranium content
of the stock solution
elements was required
By using appropriate
102 ± 5%. All
calibrated
3.
total
was determined by measuring the fluorescence
fused in a NaF-LiF salt
of U308 dissolved
quantities
quantity
fluorescent
scinof an
of actinide
element in the sample.
uranium recovery was determined to be
Model 26-000 Fluorometer
in 2 M HNO
sample plus the quantity
of the study. The undissolved
and plotted
Plutonium
intensity
12). No separation
the
of Pu and Am (nCi) and U (ug) were determined by summing
amount of each isotope in each solvent
sandwich at the conclusion
(Ref.
measurements were made using a Jarrel-Ash
with a standard solution
of the initial
pellet
blank and standard samples, the overall
The initial
in the figures.
time,
were determined by alpha liquid
since uranium was the only significantly
fluorescence
day. Beyond this
versus time.
fraction
measured in the filter
was expressed as a percentage
Two-component exponential
equations Eq. (I)
were
used to describe the rate profiles;
% undissolved
= A e-~l t + A te-X2
I
2
where Ai = percentages of the total sample dissolved, ~i = corresponding dissolution
rate constants (hr -I) and t = elapsed time (hr). The rate profiles
were obtained from individual
data
points
fitted
by a nonlinear
least-squares
technique.
(1)
3.
RESULTS
3.1.
Aerosol Characteristics
Particle
and Isotopic
size distributions
those sampled during normal fuel
of regenerated HEDLaerosols (Table 1) were similar
fabrication
operations
graphs of aerosols regenerated in the laboratory
distribution
(Fig. 1).
with irregular
Composition
(Ref.
2).
showed particles
surfaces and shapes. All
Transmission electron
that were polydisperse
photomicrographs
microin size
showed agglomeration
Americium - 241 and 238pu, 239pu and 240pu comprised the observed gross alpha
activity
of industrial
mixed-oxide
powders and aerosols (Table 2) (Ref.
1). Both 239pu and 240pu
were known to be present but since the alpha energies of 239pu (5.16 and 5.11MeV) and 240pu
(5.17 and 5.12 MeV) differ by only 10 keV, the peaks corresponding to the two isotopes were not
resolved. The major contributors
to the total alpha activity
were from 239pu and 240pu. Lesser
activities
of 238pu and 241Am were found. Beta activity
from 241pu was observed in varying
amounts.
Table 2.
Elemental and isotopic composition of industrial
fuel powdersand aerosols
a
% Alpha Activity
B&W
Isotope
239’240pu
B&W
HEDL
PuO
2
850°C
Blending
Powder
Aerosol
74
± SD
UO2 2
+ PuO
750°C
Ball Mill
Powder
Aerosol
69
73
74
238pu
6.1 ± 0.4
17
11
11
241Am
20
15
16
15
UO
2 + PuO
2 + Binders
850°C
Pellet Pressing
Powder
Aerosol
12.3
12.0
12.1
13.1
40
43
8.8 ± 0.4
37
35
11
23
22
20.7
24.9
82
80
7.2 ± 0.3
12
Beta/Total Alpha Activity
241pub
HEDL
(U,Pu)OI.96
1750°C
Pellet Grinding
Powder
Aerosol
Ratio ± 5%
12.5
13.5
aSDis standard deviation = ± i% unless specified
b0.021MeVbeta radiation.
3.2.
Crystal
Properties
X-ray diffraction
3) showed that all
materials
patterns
of the powders and respective
were in the face-centered
Each major peak in the pattern
standard) appeared to be split
cubic form typical
aerosols (Fig.
of actinide
2 and Table
dioxides.
of HEDLUO2 + PuO2 750°C (Fig. 2a) (excluding the Ag calibration
to include a less intense peak at a slightly
greater diffraction
angle. The more intense peak of each pair corresponded to UO2 (JCPDS Card No. 5-0550) and the
less intense peak was from PuO2 (JCPDS Card No. 6-0360, Ref. 13). All diffraction
peaks were
assignable to UO2, PuO2 or Ag. The slight splitting
of each peak at diffraction
angles greater
than 60° 20 reflected the resolution
of the K~I and K~2 components of the incident X-ray beam.
I00
A
8O
6O
>1-O3
Z
L.IJ
I.-Z
I
66
58
DEGREES 28
50
42
I..iJ
>
I’- I00-
B ~U,Pu)O,,, Ag
._1
80-
m
Ag
~o~,
~o~
Ag
6O
40
20
I
O82
Figure 2.
74
66
58
DEGREES 28
50
42
X-ray powder diffraction
patterns of A) 750°C heat-treated mixed U02 and Pu02 powder
obtained from the ball milling process at HEDL, and B) 1750°C heat-treated (U,Pu)01.96
obtained from the pellet grinding process at HEDL.
Table 3. Unit cell
dimensions of industrial
mixed uranium and plutonium
dioxide
fuel
powders and
aerosols determined by X-ray diffraction
Unit cell dimensionof face-centeredcubic structure
a ± SEa (A)
o
UO
2
Material,Source
Temperature History,
Process Step
PuO2, B&W
850°C, Blending
UO2 + PuO2, HEDL
750°C, Ball
UO2 + PuO2 +
Binders, B&W
850°C, Pellet
Pressing
(U,Pu)Ol.96,
1750°C, Pellet
Grinding
HEDL
Milling
PuO
2
a° = 5.3960
~b
ao = 5.4682 ~b
(U,Pu)OI.96
c,
5.4077 ± 0.0006
°(5.4102 + 0.0004)
5.4688 ± 0.0015
(5.4742 ± 0.0003)
5.4045 ± 0.0017
(5.394 ± 0.005
5.4664 ± 0.0007
(5.4685 ± 0.0006)
5.4034 ± 0.0006
(5.403 ± 0.004
5.4667 ± 0.0007
(5.4607± 0.005
astandard Error
bjoint Committee on Powder Diffraction
Standards (JCPDS) values for the cubic unit cell
UO2, JCPDSCard No. 5-0550; PuO2, JCPDSCard No. 6-0360.
Cpowder value.
dAerosol value.
dimension,
ao:
The diffraction
pattern of the HEDL(U,Pu)01.96, 1750°C powder (Fig. 2b)
showed major diffraction
peaks corresponding to the face-centered cubic structure of actinide
dioxides
unit
even though the oxygen-to-metal
cell
result
dimension of this
of solid
solution
material
formation
ratio
of the pellet
was slightly
sub-stoichiometric.
The
did not correspond to either
(Ref.
14,15).
All
UO2 or PuO2 (Table 3) as
peaks were assigned to the (U,Pu)OI.96 solid
solution or Ag. The presence of the organic binder in the B&WUO2 + PuO2 + Binders 850°C mixture
was not observed in any diffraction
measurements.
3.3.
Infrared
Absorption
Infrared spectra of all powders included broad, intense absorption
-I
300-600 cm region that were assigned to the metal-oxygen stretching frequencies
maxima in the
of UO2 and
PuO
2
(Ref. 16). Spectra of the B&W2 + PuO2 + Bi nders, 85 0°C powder (F ig. 3) inc luded add itional
peaks in the 1000-1500 cm-I and 2600-3000 cm-I regions that were assigned to Sterotex 0 and Carbowax~ binders added to the mixed-oxide powders to facilitate
pellet pressing. Spectra of other
mixed-oxide powders were the same as Fig. 3 in the metal-oxygen stretching
region.
II
~- 40
z
~.)
.UJ
II
3000V’lSO0
1400
"l)
WAVENUMBER
(cm
I000
Figure 3. Infrared spectrum of mixed PuO2 and UO2 powders containing
tained from the pellet pressing operation at B&W.
600
organic
300
binders and ob-
Spectra of powders and aerosols were studied in the 700-4000 cm-1 region by expansion of the transmittance
scale by a factor
of 5. The spectra
of powders and aerosols of the HEDL
(U,Pu)01.96 1750°C material (Fig. 4) contained bands at 916, 1100, 1170, 1400, 1530, and 1640 -I.
Similar peaks were observed in all spectra within ±10 cm-1 of the above values except that the
~1170 cm-1 peak was not observed in the HEDLUO2 + PuO2 750°C spectrum. Bands at 1640, 1530, 1170
and II00 cm-1 corresponded to bound carbonate species in both mono- and bidentate forms (Ref. 17).
The broad band at 1400 cm-1 suggested the presence of free carbonate ions or a bound carbonate
species,
but was not assigned to a specific
was revealed
at the instrumental
sensitivity
species since it
included a contribution
from KBr that
-1
used in the Fig. 4 spectrum. The 916 cm band was
assigned to a surface layer of UO3 or U022+ in the mixture (Ref. 18). A broad band at 31003400 cm-I in the spectra of B&WPuO2 850°C and HEDLUO2 + PuO2 750°C aerosols (Fig. 5) is generally assigned to atmospheric water absorbed by KBr. The broad band was more intense than the
spectrum of pure KBr, however, and was assigned to the H20 (~3) resonance if
plutonium formulated as [(HO)n_l-O-Pu-O-(OH)n_ 1] (Ref.
to membranefilter
material.
a polymeric form
-I
19}. The 2900-3000 cm peak corresponded
Z
1800
1600
1300
-I
WAVENUMBER
)
(cm
I000
700
Figure 4. Infrared spectra of 1750°C heat-treated (U,Pu)01.96 materials from the pellet grinding
operation at HEDL; a) powder, b) aerosol. Ordinate scale expanded 5X. The 1601 -±
polystyrene absorption peak is shown separately for calibration
purposes.
,
3800
I
I
I
I
3400
3000
"l)
WAVENUMBER
(cm
2800
Figure 5. Infrared spectra of a) pure KBr and b) 850°C heat-treated
operation at B&W. Ordinate scale expanded 5X.
Pu02 from the blending
3.4.
%n Vitro
All
Dissolution
dissolution
rate curves showed biphasic profiles
(Fig.
6,7) with a rapid
initial
phase followed
by a much slower phase (Table 4). Plutonium and americium dissolved
similar
rates from all
materials.
Uranium dissolved
more rapidly
with
than Pu or Am in the aerosols
that contained PuO2 and UO2 as admixtures. The solid solution of (U,Pu)OI.96 showed unique
dissolution
properties with Pu and Am dissolution
rates greatly increased and the U dissolution
rate unchanged (Table 4). The precision
triplicate
the first
experiments.
of calculated
dissolution
half-times
was estimated from
Since the sampling frequency was one change of solvent
day of the experiment,
the limit
of precision
phase was estimated to be ± 0. i day. The precision
per hour during
of the half-time
in the rapid dissolution
half-times
of ~ 100 days was ±
of dissolution
20%(Table 4).
I00
I00 -
0
E]
n
I0
o
I0-
0
D
1.0
6
Figure 6.
I
400
I
800
HOURS
I
1200
I
1600
Comparison of Pu, Am and U dissolution
rates from aerosol samples of mixed
Pu02 and U02 containing organic
binders
in 2 M HNO
3.
i.r~
vo
Figure 7.
i
400
I
800
HOURS
i
1200
I
1600
Comparison of Pu, Am and U dissoltion
from aerosol samples of 1750°C heattreated (U,Pu)OI.96 in 2 M HNO
3.
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4. DISCUSSION
4.1.
Comparison of Powder and Aerosol Isotopic
Comparisons of isotopic
that,
in general,
compositions
compositions of powders and aerosols (Table 2) indicated
did not differ
greatly.
values for the B&WPuO2 850°C powders and aerosols,
the powder contained more 238pu and less 241Am.
Differences
Compositions
The greatest
indicating
differences
were noted in
that the aerosols generated from
between the powder and aerosol forms were attributed
to the nature of
the stage of PuO2 processing and of the different
particle
size distributions
present. In the
stages of processing, PuO2 lots each with slightly
variable history and composition are
early
blended. The range of isotopic distributions
in the blended PuO2 reflects
this variability.
Further, since this stage precedes the powder comminution steps (represented here by ball milling)
the particle
size distributions
of each PuO2 lot were retained after blending. These two factors
can combine such that an aerosol generated from a blend of Pu09 that included a lot composed of
smaller particles
with a relatively
large percentage of 238pu or 241Amor both would tend to have
increased alpha activity.
The same factors
could as well combine such that an aerosol from
blended PuO2 lots might contain a greater percentage of the less active isotopes. Differences
between compositions of powders and aerosols tended to be dampenedin later process stages in
which the average size of PuO2 particles
4.2.
in the blend were reduced.
Surface Composition
The observation of adsorbed CO2 and H20 species on industrial
mixed-oxide particles
indicated that the surfaces were different
from the interiors.
Similar observations were made for
metal oxides prepared in the laboratory (Ref. 17,19,20). Infrared bands at 1370 -I and 15 40 cm-I
have been assigned to strongly chemisorbed carboxylate species on U02.18 films (Ref. 20). Results
reported here indicated the additional
presence of carbonate species. The greater intensity
of
surface species peaks in spectra of aerosols compared to powders (Fig.
from the greater
aerosol (Fig.
specific
surface area of more finely
divided
4) was assumed to result
particles.
The presence of a UO3 or U022+ peak in the spectra of the HEDL(U,Pu)01.96 1750°C
4) indicated that the surfaces of the particles were not sub-stoichiometric.
Although the fuel pellets consisted of a solid solution of (U,Pu)01.96, the above results and the
solubility
of oxygen in uranium oxides (Ref. 16,20) suggest a partial or complete reversal (at
surface)
of the reduction
that occurred during the pellet
sintering
process. Adsorption
rates of
CO2 on uranium and plutonium oxides are very rapid and occur within ~ 3/50 sec (Ref. 21). Thus,
industrial
mixed oxide particles
accidently released from an inert atmosphere in a glove box could
adsorb carbon dioxide before inhalation
4.3.
by a worker.
Comparison of Powder and Aerosol Crystal
Properties
Powders and aerosols were shown to have the actinide
dioxide chemical form by X-ray
diffraction
(Table 3). Comparison of the calculated unit cell dimension of the B&WPuO2 850°C
sample values for powder and aerosols with the accepted value of 5.396 A indicated the presence of
Pu(IV) dioxide
but with a unit cell
pansion of the unit cell
oxalate
latter
or crystal
factor
lattice
indicated
dimension ~ 0.013 A larger
imperfect
crystal
expansion due to self
was probably the major contributor
with an alpha specific
activity
formation
than the accepted value. This exduring calcination
absorbed radiation
damage (Ref.
of plutonium
22,23).
The
since the powder is a mixture of Pu isotopes,
of = 90 mCi/g.
11
Two mixtures of PuO2 and UO2 were studied: HEDLUO2 + PuO2 750°C,
and B&WUO
2
+ PuO2 + Binders 850°C. Comparison of the lattice
parameters of UO2 in the mixtures with the
accepted value showed good agreement. The PuO2 phase was found to have lattice
constant values
from 0.007 A to 0.009 A greater than the accepted value as observed for the pure PuO2 powders
discussed above. The specific
alpha activity
of PuO2 in these mixed oxides was found to be
80 mCi/g PuO2, similar to those of the pure PuO2 powder. The slight difference between the
lattice
constants of PuO2 in the two admixtures (0.002 A) was probably the result of different
heat treatment histories (Ref. 24).
The major feature
was that although the UO2 and
PuO2 powders were intimately
mixed, they still
consisted of discrete UO2 and PuO2 particles,
while
the HEDL(U,Pu)OI.96 1750°C materials contained only one crystalline
solid solution.
The observation that the same solid solution exists in particles of respirable size is useful in the
interpretation
of the different
4.4.
Relationships
Relative
from fabrication
of the X-ray diffraction
in vitro
dissolution
of Dissolution
dissolution
steps prior
results
behavior of the solid
solution
matrix.
to Aerosol Matrix
rates of Pu, Am and U from aerosols of mixed-oxides obtained
to sintering
at 1750°C (Fig.
6,7; Table 4) indicated
that the 2
This independent UO2 dissolution
dissolved
rapidly and independently of the PuO2-AmO
2 matrix.
agreed with X-ray diffraction
results that showed these powders to be admixtures of PuO2 and
2. UO
The similarity
in Pu and Am dissolution
rates indicated that Am dissolution
was governed by the
slower dissolution
of PuO2, the major mass constituent of the matrix. This similarity
in longterm Pu and Am dissolution
generally held within the limits
of precision of the analyses.
solution
The HEDL(U,Pu)01.96, 1750°C material that had been sintered to form a solid
exhibited unique dissolution
properties.
Greater percentages of Pu and Am in this
material
were dissolved
increased.
(uranium)
turn.
in the early
These results
modified the dissolution
Thus, solid
dissolution
component and long-term dissolution
support the hypothesis
solution
rate of all
formation
rates were
that the major mass component of the matrix
other components with its
rate slightly
enhanced plutonium and americium dissolution
modified
relative
to
admixed UO2 and
2. PuO
5.
BIOLOGICALCONSIDERATIONS
The above results
described important
physical
and chemical properties
metabolism of inhaled mixed-oxide aerosols and showed that the properties
fabrication
at the source of a possible
an accidental
inhalation
release.
Isotopic
distributions
exposure must be determined to characterize
related
to potential
reflected
the stage of
of materials
involved
in
the source terms for tissue
dose calculations
based on metabolic models (Ref. 25). In addition,
the use of 241Am/Pu ratios
can be used to estimate the initial
lung burden of Pu from measurement of the 241Am gammaemissions (Ref. 26).
X-ray diffraction
tion
properties
and in vitro
of aerosols
dissolution
measurements indicated
depended on the fabrication
stage.
that crystal
and dissolu-
The metabolism of inhaled mixed-
oxide
aerosols from fabrication
steps prior to pellet sintering can be expected to reflect PuO
2
retention and translocation
rates independent of UO2 and similar to those of pure industrial
grade
PuO2. The metabolism of Pu and Am inhaled as part of a (U,Pu)1.96
to reflect the increased Pu dissolution observed in vitro.
In vitro
dissolution
used to estimate the initial
uble"
fraction
3
12
(Ref.
rate profiles
included
a rapid dissolution
solid
solution
phase. Various methods are
lung burden of an exposed worker from urinary
27 and references
cited
therein).
Dissolution
can be expected
bioassay of the "sol-
of mixed-oxides in 2 M HNO
does not necessarily compare with in vivo dissolution;
-~
upper estimate of the "soluble" fraction if the initial
assay. Furthermore,
useful
the upper limit
in estimating
obtained
within
3.
Infrared
of the soluble
the amount available
however, these experiments can provide an
lung burden were to be estimated by bio
fraction
for a chelation
of the particle
the biological
with lung tissue
feature
formation
accidental
in predicting
in the rapid early
The important
solution
therapy approach. Useful results
spectroscopy showed the presence of chemically
surfaces are important
of particles
can be
in this
study. Consideration
results
exposure of a worker, it
for biological
for analysis.
is likely
This would raise
As discussed above, isotopic
distribution
composition
in these laboratories.
considerations
was solid
forms. In the practical
case of an
the question
of the relationships
between
aerosols. Comparisons of X-ray diffraction
data for
that crystal structures for powders and aerosols were the
compositions
isotopes
in powders and aerosols were
of powders and aerosols did not differ
processing stage (Table 2). For materials
values for all
con-
that only powdered exposure materials
same in all cases. Unit cell dimensions for PuO2 and UO2 particles
not statistically
different
(p < .05).
except in the earliest
of altered
since initial
The role of the surface
phase is under investigation
of X-ray diffraction
powders and the corresponding resplrable
powders and aerosols (Table 3) indicated
surfaces of aerosol particles
fate of inhaled particles
occurs at the surface.
dissolution
altered
that was evident in both powder and aerosol
inhalation
would be available
tion,
would be
24 hours using 2 M HNO
that could not have been observed by other techniques
tact
of Pu and Am in a material
processed after
in powders and aerosols agreed within
greatly
powder comminuexperimental
precision excepting the 238pu percentage of B&WUO2 + PuO2 + Binders, 850°C materials.
The 238pu
percentage difference was minor when compared to the total Pu alpha activity,
however, and a good
estimate of the aerosol isotopic
composition
could be obtained by analysis
of the powder. The
isotopic distributions
of B&WPuO2 850°C materials (Table 2) indicated that an adequate estimate
of the aerosol might be obtained by powder analysis, but the aerosol form should be analyzed to
obtain the best estimate of an aerosol inhaled by a worker.
6.
CONCLUSIONS
In the event of an accidental
fabrication
facility,
for predictions
Crystal
tion
physical
of the biological
properties
inhalation
correlated
spectroscopy results
of the mixed-oxides involved
nuclear fuel
will
be valuable
consequences.
with in vitro
of Pu and Am when incorporated
frared
exposure of a worker in an industrial
and chemical analysis
indicated
into
a solid
dissolution
solution
that the reduction
properties
to show increased dissolu-
during the pellet
sintering
step.
In-
of mixed-oxides that occurred during pel-
let sintering was partially
reversed by CO2 and H20 adsorption such that the composition at the
surface is probably (U,Pu)O 2. In vitro dissolution
rate profiles
in 2 M HNO
3 included a rapid
early dissolution
phase that can be used to estimate an upper limit for the soluble Pu or Am
fraction
available
for chelation
assay. Comparisons of isotopic
therapy or for estimates of the initial
distributions
and crystal
aerosols showed that, in general, the information
an inhaled aerosol could be obtained by analysis
properties
lung burden based on bio-
of powders and respirable
important for predicting the biological
fate of
of powders. The one exception was the isotopic
distribution
of PuO2 from the blending step. In these cases, analysis of respirable aerosols
this material, and others from process steps prior to powder comminution, would be preferred.
of
13,14
7°
REFERENCES
i.
J. M. Selby, E. C. Watson, J. P. Corley, D. A. Waite, L. A. Carter, L. C. Schwendiman, J.
Mishima, R. K. Woodruff, T. I. McSweeneyand J. B. Burnham, "Considerations in the Assessment
of the Consequences of Effluents from Mixed-Oxide Fuel Fabrication Plants," BNWL-1697, Rev.
I, 1975.
2,
O. G. Raabe, G. J. Newton, C. J. Wilkinson, S. V. Teague and R. C. Smith, "Plutonium Aerosol
Characterization
Inside Safety Enclosures at a Demonstration Mixed-Oxide Fuel Fabrication
Facility,"
Health Phys. 35: 649-661, 1978.
3.
H.F. Schulte,
618, 1975.
4,
S. V. Teague, H. C. Yeh and G. J. Newton, "Fabriction
Devices," Health Phys. 35, 392-395, 1978.
5,
T. T. Mercer, M. I. Tillery
and G. J. Newton, "A Multi-Stage
J. Aerosol Sci. I: 9-15, 1970.
"Plutonium:
Assessment of the Occupational
Environment,"
Health Phys 29, 613-
and Use of Krypton-85 Aerosol Discharge
Low Flow Rate Cascade Impactor,"
P. E. Morrow and T. T. Mercer, "A Point-to-Plane
Electrostatic
Sampling," Am. Ind. Hy9. Assoc J. 25: 8-14, 1964.
Precipitator
for Particle
Size
7,
I. K. Kressin, "Electrodeposition
of Plutonium and Americium for High Resolution
copy," Anal. Chem. 49: 842-846, 1977.
8,
R. F. Keough and G. J. Powers, "Determination of Plutonium in Biological
tion and Liquid Scintillation
Counting," Anal. Chem. 42: 419-421, 1970.
9,
J. B. Nelson and D. P. Riley, "An Experimental Investigation
of Extrapolation
Methods in the
Derivation of Accurate Unit-Cell Dimensions of Cyrstals,"
Proc. Phys. Soc. 57, 160-177, 1945.
X-ray Diffraction
Materials
Spectros-
by Extrac-
10.
H. P. Klug and L. E. Alexander,
Wiley and Sons), 1974.
Procedures, p. 567, 2nd ed. (New York: J.
11.
J. J. Miglio, B. A. Muggenburg and A. L. Brooks, "A Rapid Method for Determining the Relative
Solubility
of Plutonium Aerosols," Health Phys, 33: 449-457, 1977.
12.
F. A. Centanni, A. M. Ross and M. A. Desesa, "Fluorometric
Chem. 28: 1651, 1956.
13.
J. A. C. Marples, "The Low Temperature Lattice Parameters of the Actinide Dioxides," in
Plutonium and Other Actinides (H. Blank and R. Lindner, Eds.) North Holland Publishing
Company, Amsterdam, pp. 353-359, 1976.
14.
R. N. R. Mulford and F. H. Ellinger,
1958.
15.
L. E. Russell, N. H. Brett, J. D. L. Harrison and J. Williams, "Observations on Phase Equilibria
and Sintering Behavior in the PuO2-UO
2 System," J. Nucl. Materials 5: 216-227, 1962.
16.
G. C. Allen, J. A. Crofts and A. J. Griffiths,
"Infrared
System," J. Nuclear Materials 62: 273-281, 1976.
17.
M. L. Hair, Infrared
204-208~ 1967.
Determination
"U02-PuO2 Solid Solutions,"
of Uranium," Anal.
J. Am. Chem. Soc. 80: 2023,
Spectroscopy of the Uranium/Oxygen
Spectroscopy in Surface Chemistry, Mercel Dekker, Inc.,
New York, pp.
15
18.
M. Tsuboi, M. Terada and Shimonouchi, "Optically
Trioxide,"
J. Chem. Phys. 36: 1301-1310, 1962.
19.
L. M. Toth and H. A. Friedman, "The IR Spectrum of Pu(IV) Polymer," J. Inorg.
807-810, 1978.
20.
C. Colmenares, "Infrared
Spectroscopic Studies of the Surface Bond of Carbon Dioxide on
Uranium," J. Phys. Chem. 78: 2117-2122, 1974.
21.
C. A. Colmenares and K. Terada "The Adsorption of Carbon Dioxide on Uranium and Plutonium
Oxides," J. Nuclear Materials 58: 336-356, 1975.
22. T. D. Chikalla and R. P. Turcotte,
Effects 19: 93-98,1973.
"Self-Radiation
Active Lattice
Vibrations
DamageIngrowth
of s-Uranium
Nucl. Chem. 40:
in 238pu02,"
Radiation
23.
R. B. Roof Jr. "The Effects of Self-lrradiation
in X-ray Analysi s 17: 348-353, 1974.
24.
R. P. Turcotte and T. D. Chikalla,
Effects 19, 99-108, 1973.
25.
ICRP72 International
Commission on Radiological
Plutonium and other Actinides,"
ICRP Publication
26.
J. Rundo, M. G. Straus, I. S. Sherman and R. Brenner, "Methods for the Assay of Plutonium In
Vivo: What are the Alternatives?"
Health Phys. 35: 851-858, 1978.
27.
A. de G. Low-Beer, "Bioassay of Plutonium," in Handbook of Experimental Pharmacology, Vol.
XXXVI, Uranium, Plutonium, Transplutonic Elements (H. C. Hodge, J. N. Stannard and J. B.
Hursch, Eds.) Springer-Verlag,
New York, pp. 593-611, 1973.
16
on the Lattice
"Annealing of Self-Radiation
of 238(80%)Pu02 III,"
Advances
Damagein 238pu02," Radiation
Protection, "The Metabolism of Compoundsof
19, Pergamon Press, New York, pp. 5-9, 1972.
NRC FORM 335
1.
U.S. NUCLEAR REGULATORY COMMISSION
(7 77)
REPORT NUMBER ~$$~gnedby
NUREG/CR-1736
LMF-78
BIBLIOGRAPHIC DATA SHEET
4. TITLE ANDSUBTITLE ~dd Volume No., if
~pr~ria~)
2. (Leave blank)
Comparison of Physical ChemicaiProperties
of Powders and
Respirable Aerosols of Industrial
Mixed Uranium and
Plutonium Oxide Fuels
3. RECIPIENT’S ACCESSIONNO.
7. AUTHOR(S}
5.
DATE REPORT COMPLETED
MONTH
A. F. Eidson
9.
I
October
PERFORMING ORGANIZATION
NAME AND MAILING
DDC)
ADDRESS (Include
Zip
Code)
YEAR
1980
DATE REPORT ISSUED
Inhalation
Toxicology Research Institute
Lovelace Biomedical and Environmental Research Institute
P.O. Box 5890
Albuquerque, NM 87115
MONTH
ovember
I~
6. (Leave blank)
8. (Leave blank)
12.
SPONSORING ORGANIZATION
NAME AND MAILING
ADDRESS Unclude
Z~p Code)
10.
Environmental Effects Research Branch
Division of Safeguards, Fuel Cycle and Environmental
Office of Nuclear Regulatory Research
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Washinqton. DC 20555
13. TYPE OF REPORT
Research
PROJECT/TASK/WORK UNIT
NO.
11. CONTRACT NO.
FIN No. AI031
PERIOD COVE RED (Inclusive
dates)
Technical
15.
SUPPLEMENTARY
NOTES
I 14. (Leave olank)
16. ABSTRACT
~00 wor~ orless) The purpose of these studies is to delineate physical and chemical factors important in determining the biological
fate of mixed-oxides if inhaled. The similarity
between powders and respirable
aerosols was also studied. Four representative
mixed-oxide
powders were obtained from fuel fabrication
enclosures. Aerosols of the powders were regenerated in the laboratory
and collected
for analysis.
Crystal structure
analysis of powders and
aerosols showed that material from processes prior to pellet sintering
consisted of discrete
Pu02 and U02 phases while materials from the pellet grinding step were in a (U,Pu)01.96 solid
solution.
Incorporation
of Pu into a solid solution with U02 caused an increase in the Pu dissolution rate in vitro.
Infrared spectral analysis showed that surfaces of aerosol particles
contained adsorbed CO2 and H20, suggesting that the reduction caused by sintering
was partially
reversed at the surface. X-ray diffraction
results indicated that analysis of powders is sufficient
to characterize
the aerosol form. Alpha spectroscopy results indicated that isotopic
composition of aerosols from steps following
powder comminution could be obtained from powder
analysis. An adequate estimate might be made for materials from steps prior to powder comminution, but aerosol analysis is preferred.
17.
KEY WORDS AND DOCUMENT ANALYSIS
~ixed oxide, aerosol; inhalation,
X-ray
diffraction,
infrared spectra, solubility,
biological
fate, industrial
nuclear fuel
fabrication
17b
IDENTIFIERS/OPEN-ENDED
AVAILABILITY
STATEMENT
]7a
DESCRIPTORS
uranium, plutonium,
inhalation
TERMS
19.
SECURITY CLASS (Th~s reDort)
20.
SECURITY CLASS /Th,sDa~l
Jnlimited
IRC FORM335 (7.’/7)
aerosols,
Unclassified
Unclassified
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zo
Zm
mO
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o
m
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