Full text of DOI:10.1557/mrs2001.180

www.mrs.org/publications/bulletin
in glass and ceramics1–5 and review publi-
cations that include valuable information
on plutonium glasses.6 The plutonium re-
maining in the radioactive HLW resulting
from defense-waste reprocessing and com-
mercial HLW worldwide is minimal and
leads to concentrations in the waste form
of below 0.05 wt%. But in many cases,
higher concentrations were studied at the
laboratory scale as surrogates for all acti-
nides and to investigate the effects of high
radiation on the matrices. In 1994, 14 of
the 20 countries participating in the inter-
national experience on radioactive-waste
Plutonium in
Crystalline
Ceramics
7
management selected glass as a waste
form for geologic disposal. These glassy
waste forms have been produced on a large
scale for over three decades in Europe
(the Marcoule and La Hague facilities in
France, the Pamela facilities in Belgium
and Germany), China, India, Japan, Russia,
and in the United States (the Defense Waste
Processing Facility and the West Valley
Demonstration Project), leading to the
processing of thousands of metric tons of
HLW glass. Ceramic forms have also been
fabricated for over a decade on a commer-
cial scale. The Synroc Demonstration Plant,
constructed at Lucas Heights, Australia,
was commissioned in 1987 and utilizes hot-
pressing to consolidate Synroc, a dense,
multiphase titanate-based waste form,
from simulated reprocessed liquid HLW
using the Purex* process.
andGlasses
Isabelle Muller and William J. Weber
This article is a short qualitative summary
The need for stability over a very long
period, relative to the half-life of 239Pu or
other long-lived actinides in high-level
waste (HLW) is the essential driver of many
compositional studies involving structural
refinement, such as determining plutonium
site valences and coordination, measuring
the stability of the matrix under the effect
of irradiation, and assessing its alterability
under conditions expected in a geologic
repository for waste disposal.
of a chapter in the forthcoming book Advances
in Plutonium Chemistry: 1967–2000, edited
by Darleane Hoffman for the Amarillo National
ResearchCenter. Theauthors’intent here is to give
an overview of the history and science of pluto-
nium in ceramics and glasses, and they refer
readers to the chapter for more technical details.
Introduction
The investigation of plutonium in glasses
(amorphous ceramics lacking long-range
order), in crystalline ceramics, and in com-
posite materials composed of multiple crys-
talline or glass and crystalline phases, relies
on multidisciplinary studies of physics,
chemistry, and materials science. It involves
the study of the plutonium atoms in mate-
rials with only short-range periodicity, as
in glasses, to materials with long-range
periodicity, as in crystals. The materials
studied over the past 30 years include
simple binary crystals, used to investigate
the electronic structure of plutonium, to
complex glasses and ceramics selected not
only for the safety and durability that they
provide for the immobilization of nuclear
waste and plutonium, but also for the
high flexibility they offer in composition.
The lack of long-range order at the atomic
level in glasses permits the inclusion of
a broad range of waste elements, but it
renders more difficult the interpretation of
data from many commonly used experi-
mental techniques. Regardless of the chal-
lenge, much of the research conducted in
this field over the past few decades has
been motivated by the use of plutonium
as a surrogate for all nuclear-waste actinides
or on its own in immobilization studies,
in order to develop a durable glass or ce-
ramic matrix that can resist leaching and
mobilization of the plutonium on a geo-
logic time scale.
This article will present a review of the
glass and ceramic systems in which pluto-
nium can be dissolved and the flexibility
of these materials in retaining various
grades of plutonium, which often cannot
be purified without great expense and
difficulty. Since glass-matrix and ceramic
materials often differ in their composition
and technique of preparation, they are
presented in separate and parallel sec-
tions, as is done in the book chapter being
summarized.
With the end of the Cold War, new pro-
grams involving the management and
disposition of weapons-grade plutonium
have emerged. Specifically, as a result of
the Strategic Arms Reduction Treaties and
agreements made by presidents of the
United States and Russia (START I, 1991,
and START II, 1993), tens of thousands of
nuclear weapons are being retired in both
countries. These disarmament activities
are expected to produce a surplus of more
than 50 metric tons, pure and impure, of
weapons-grade plutonium in each coun-
try, along with hundreds of tons of highly
enriched uranium (HEU).According to the
National Academy of Sciences, this result-
ing plutonium inventory represents “...a
clear and present danger to national and
international security.”8
The current international effort associated
with the immobilization of excess weapons
plutonium and plutonium residues within
the nuclear-weapons complexes has re-
sulted in pilot-scale and industrial facili-
ties for plutonium immobilization located
around the world. These facilities are cur-
rently processing or are in the testing phase
for the processing of significant quantities
of plutonium that may be incorporated
into glasses or ceramics. The pouring of
one such test glass at Savannah River is
pictured in Figure 1.
To address the problem of how best to
manage the surplus plutonium from dis-
armament activities, the United States has
adopted a two-part strategy. The almost
20 metric tons of impure plutonium in the
form of scrap, residues, and so on, will
Historical Aspects
Ceramic materials have been considered
as viable waste forms for the disposal of
commercial high-level nuclear-waste solu-
tions in solid form since the 1970s, leading
to many published studies on plutonium
*Purex stands for plutonium-uranium extrac-
tion; a diagram can be found at http://
www.ieer.org/ensec/no-2/purex.html.
698
MRS BULLETIN/SEPTEMBER 2001

Plutonium in Crystalline Ceramics and Glasses
evaluating disposition options for the
management of excess plutonium result-
ing from nuclear-disarmament activities.
They concluded that “the two most prom-
ising alternatives for achieving these aims
(long-term plutonium disposition) are:
fabrication and use as fuel, without
reprocessing, in existing or modified nu-
clear reactors; or vitrification in combina-
tion with high-level radioactive waste.” A
third possibility, involving burial of plu-
tonium in deep boreholes, was also men-
tioned for possible future consideration.
As a result of the NAS study, a concen-
trated effort began in the 1990s. This effort
focused on the investigation and assess-
ment of the recommendations made by
the NAS and, more specifically, considera-
tion of the various reactor options and the
vitrification immobilization recommen-
dation. The effort on immobilization was
later expanded to include initial screening
of over 70 potential solidification matrices
in addition to glass. Ceramic forms, both
glassy and crystalline, emerged as the lead-
ing solidification matrices, and no “show-
stoppers” indicating the matrix to be too
leachable or sensitive to radiation damage
were identified for either the glassy or
crystalline forms. An independent review
team further concluded that “the two forms
and their processes are similar in many
ways,” and both glassy and crystalline
forms were able to satisfy existing crite-
ria.15 Some of the noncrystalline ceramic
systems were similar to the borosilicate
glass compositions currently in worldwide
use for immobilizing high-level radioactive
wastes. The glass systems considered are
borosilicates, soda-alumino phosphates,
lanthanide silicates, and alkali-tin silicates
(Table I). Various crystalline assemblages
in crystalline ceramics were also tailored
so that they could incorporate plutonium
effectively. Some of the ceramic phases of
interest have been zircon and zirconolite,
pyrochlore, perovskite and titanite, mona-
zite, and apatite (Table II). In either glass or
ceramic, plutonium is uniformly distrib-
uted and an integral part of the material’s
structure. Both glassy and crystalline ce-
ramic systems are able to achieve the de-
sired results of immobilization of plutonium
into highly durable waste-form products
that would make reclaiming and reuse of
the plutonium for military purposes dif-
ficult. Of these systems, the crystalline ce-
ramic forms were determined to have more
advantages in processing and product
performance.9 In the following sections,
the important features of these vitreous
and crystalline materials, along with rele-
vant considerations, observations, and re-
sults, are described.
Figure 1. Laboratory pouring of Pu-borosilicate glass at Savannah River. (Courtesy of
D. Karraker.)
be immobilized into a crystalline ceramic
matrix, and the more than 30 metric tons
of relatively pure plutonium will either be
made into a mixed-oxide (MOX) fuel for
nuclear reactors or immobilized into crys-
talline ceramic forms. While both glassy
and crystalline ceramic matrices have been
studied for the immobilization of pluto-
nium, the currently preferred immobili-
zation medium in the United States is a
titanate-based ceramic under development.9
At this time, the preferred methodology
for final disposition in a U.S. government
repository is a “can-in-canister” process,10–13
where plutonium ceramic cans are placed
in HLW glass canisters. Similarly, two
Russian options are considered:14 either
homogeneous glass or ceramic composi-
tions with an internal radiation barrier
using induction melting, or can-in-canister
glass or ceramic compositions with an
external radiation barrier using induction
melting.
In January of 1994, the Committee on
International Security and Arms Control
of the National Academy of Sciences (NAS)
published the results and recommenda-
tions8 of an extensive multiyear study
MRS BULLETIN/SEPTEMBER 2001
699

Plutonium in Crystalline Ceramics and Glasses
Table I:Summary of Various Formulations of Glasses Containing Plutonium (wt%).
Reference: [16]
Glass ID:
[17]
[17]
UK
[17]
[17]
[3] [4]
[18] [19] [20] [21]
[22] [23,24] [23,24] [25] [26, 27] [28]
France
Germany Belgium
SON58 189/209 VG98/3
78/7
Al2O3
0.1
19
0–5
1
5
6.0 4.8 3.8 9–9.5
7.0 7.6 7.8 4–5
19
2.2
8.9
2.6
4
18.6
0.16
B2O3
BaO
19–20
11–22
10
11
6
9
4
10.4
12.7
13
0.2 0.2
2.0 1.2 1.2
10.0 12.5 11.7
0–2
4
3.6
CaO
Fe2O3
Gd2O3
K2O
2
1
0.02
0.08
0.6
2.7
16
4.7
11
18.1
7.6
11
3.8
7.7
3
4
3.5 3.6
1.5
0.24
0.14
La2O3
Li2O
9–23
4
6
8
4
4.9 4.4 4.3
0.7 1.4 1.3
3.9
9.2
3.4
9.0
4
5
MgO
Na2O
Nd2O3
P2O5
PbO
0.4
22
9–10
9.4
44
21 11–13 9.1 8.6 7.6
12.0 23.4
0.43
11.4
48
2
66.3 55.00
11–13
SiO2
45–47
41–51
42
58 67–75 50.6 49.6 49 26–35 25.8
6–18
45.4
42.8
42
Sm2O3
SnO
0.06
2.2
2.1
3.1
4.9
0.9
6
1.8
2.2
TiO2
3.5
5
7a
0.6
ZnO
ZrO2
0.7
3b
0.9 0.1–0.2
1.2
5
0.47
1.4
Others
PuO2
19–23
23
9.7
16
28
0.5
1
ϳ3
ϳ3
ϳ3
ϳ3
ϳ3
ϳ1
7
1.0 4–7c 2–7c 6.9 and 11.4 to
15c
16
ϳ8.5 10 and
22
ϳ1
25 as Pu3+
a Formulated by substitution from Na2O and SiO .
2
b as U3O8.
c The authors give “as-batched compositions,”but optical observation indicates that the solubility of plutonium is exceeded—the glass includes crystals.
radiation.43,44 In the specific case of excess
Plutonium in Ceramics
TableII: Potential Plutonium or
andComposites
weapons plutonium in the United States,
the disposition of the plutonium may be
done through incorporation into MOX
nuclear fuel or into nonfertile (i.e., inert-
matrix) fuel for burning in reactors, or by
incorporation into ceramics for eventual
disposal in a geologic repository.45,46 Simi-
larly, the increasing worldwide inventory
of plutonium generated by commercial
nuclear-power production has initiated in-
terest into the potential use of inert-matrix
fuel to burn plutonium and other acti-
nides, such as americium, without pro-
ducing additional fissile material.47–52
Actinide-Bearing Phases.
There have been two principal motivat-
ing factors over the past three decades for
the interest in studies of plutonium in ce-
ramics and composites. The first is related
to developing fundamental scientific knowl-
edge of radiation damage or the electronic
and nuclear properties of plutonium in
a wide range of solids. Such knowledge
can be obtained by studying self-radiation
effects from ␣ decay29–35 or by using elec-
tron paramagnetic resonance (EPR)36–39 and
optical spectroscopy techniques.40 The sec-
ond factor is driven by the proposed use
and stability of crystalline host phases
for the immobilization of actinides from
nuclear waste generated by the reprocess-
ing of spent commercial nuclear fuels or
from the production of nuclear-weapons
StructureType
Oxides
fluorite
Composition
ThO2; UO2; PuO2
pyrochlore
zirconolite
perovskite
zirconia, ceria
A2B2X6Y;RE2Ti2O7; Gd2Ti2O7
CaZrTi O7
2
CaTiO3
ZrO2; CeO2
Silicates
zircon
apatite
ZrSiO4
Ca4ϪxRE6ϩx(SiO4)6O1ϩ0.5x
titanite
CaTi(SiO )O
4
Much of the basic research regarding
plutonium in ceramics has been focused
on using 238Pu to study self-radiation ef-
fects due to ␣-decay events and both 239Pu
and 242Pu in EPR studies. The short half-
life of 238Pu, 87.7 years,53 allows sufficient
␣-decay events (radiation effects) to occur
in reasonable laboratory time frames (sev-
eral years), compared with 239Pu, which has
a half-life of approximately 24,000 years.53
Basic studies of radiation effects using
short-lived actinides such as 238Pu have
Phosphates
monazite
apatite
CePO4, LaPO4
Ca10ϪyREy(SiO4)y(PO4)6ϪyF2
NaZr2(PO4)3
sodium
41– 43
zirconium
phosphate
(NZP)
materials.
Recently, issues related to the disposition
of excess weapons plutonium and pluto-
nium residues from weapons production
have prompted renewed interest into plu-
tonium incorporation into crystal struc-
tures, solubility limits, and the effects of
thorium
Th4(PO4)4P2O7
phosphate
diphosphate
700
MRS BULLETIN/SEPTEMBER 2001

Plutonium in Crystalline Ceramics and Glasses
several unique advantages. If the actinide
is uniformly distributed, self-radiation from
ꢀ decay produces bulk property changes,
something that is usually obtainable only
by neutron irradiation. Furthermore, the
self-irradiation effects are produced by
charged particles (ꢀ particles and recoil
nuclei) of well-defined energies, rather
than from the spectrum of recoil energies
that is produced under neutron irradia-
tion. Such well-defined energies make it
easier to interpret and model observed
behavior. One of the objectives of studies
using short-lived actinides is to make
comparisons to natural mineral analogues
in order (1) to develop an understanding
of ꢀ-decay damage over geologic time
periods, (2) to develop scientifically based
predictive models for geologic age dating,
and (3) to assess the performance of nuclear
waste forms.
Figure 3. Stable configurations for incorporations of plutonium in zircon (ZrSiO4):
(a) Pu4ꢁ substituted on a Zr4ꢁ site, and (b) Pu3ꢁ as a defect cluster consisting of two Pu3ꢁ
substitutions on near-neighbor Zr4ꢁ sites and a neighboring charge-compensating oxygen
vacancy. (Courtesy of R.E. Williford, Pacific Northwest National Laboratory.)
Applied research on plutonium in crys-
talline ceramics has included studies of
self-radiation effects in 238Pu-doped Synroc
and its constituent phases.54,55 Self-radiation
effects have also been studied in a 238Pu-
doped celsian glass ceramic,56 which was
another multiphase waste proposed early
on. The reported radiation-induced swelling
in these materials is shown in Figure 2.
Other applied research has focused on the
use of 239Pu in single-phase ceramics pro-
posed for the immobilization of waste ac-
tinides and excess weapons Pu. One such
ceramic proposed for plutonium immobi-
lization is zircon (ZrSiO4),42 where Pu4ꢁ
can be readily accommodated by substitu-
tion on the Zr4ꢁ site,58 as illustrated in Fig-
ure 3a. Under a reducing atmosphere,
where Pu3ꢁ is the preferred valence state,
the most stable configuration for Pu3ꢁ
accommodation is as a defect cluster con-
sisting of two Pu3ꢁ substitutions on near-
neighbor Zr4ꢁ sites and a neighboring
As in the case for zircon, plutonium and
other actinides can be accommodated on
the Zr site in stabilized ZrO2, which is
a candidate material to use as an inert
matrix for plutonium burnup in a reactor
or accelerator-based neutron source.47–49,52
Some of the first tests of ZrO2-PuO2 as a
nuclear-fuel material, however, were per-
formed in the early 1960s at the Hanford
Site in Washington state.59
intermediates. As presented in the hypo-
thetical borosilicate glass structure in Fig-
ure 4, the network is primarily formed of
the chains of borate and silicate poly-
hedrons. Lithium, sodium, and calcium
are typical glass modifiers that will create
nonbridging oxygens in the network and
also provide the charge balance in the
vicinity of the plutonium-oxygen poly-
hedrons. Because glasses that contain sig-
nificant amounts of uranium and rare-earth
elements have been prepared for at least a
century (so-called Anna yellow, containing
uranium, and various colors of Löffler rare-
earth glasses from the Bohemian glass
plant, 1900s–1930s), glass-matrix network
structures could be expected to incorpo-
rate actinides, including impure as well as
pure plutonium. The dissolution of acti-
nides, and also of many minor components,
has been demonstrated in both americium/
curium and plutonium vitrification.70,71
Based on glass structures as well as bond-
ing energies, an empirical correlation has
been made between Pu-based glasses and
other radioactive-waste glass systems.72,73
The correlation is summarized in Figure 5,
which focuses on the small fraction of the
ternary diagram (glass formers, modifiers,
intermediates) where the glasses used in
the nuclear industry are found. The com-
positional ternary diagram illustrates the
relationship between plutonium glasses
that have been proposed as waste forms in
the United States and various HLW glasses
from around the world. Superimposed on
the figure is a transuranic (TRU) waste-
glass composition. A commonality exists
between the many different radioactive
waste-glass systems (including actinide
glasses), based on radioactive waste-glass
compositions and the structural role com-
ponents play in a glass. The glass formers
Plutonium in Glasses
Over the past 40 years, an enormous
amount of work has been conducted world-
wide at national laboratories, in academia,
and by industry on developing vitrifica-
tion technologies for the immobilization
of a variety of potentially hazardous mate-
rials. At a 1996 international workshop,60
the status of industrial experience was
presented by Belgium, China, France, Japan,
Russia, the United Kingdom, and the
United States. Building on this experience,
existing vitrification technologies, proce-
dures, equipment and facilities, and solidi-
fication matrices were examined for possible
use in vitrifying uranium, plutonium, and
a variety of other actinides (including
curium, americium, and neptunium).61–67
Because glasses have a random network
structure (three-dimensional [SiO4] tetra-
hedron for silicate and chain structure for
phosphate where only three corners of a
[PO4] are cross-linked), they can incorpo-
rate a wide range of chemical elements.68,69
For HLW glasses, borosilicate compositions
that include 30–40 different elements (and
in fact, significant variations in the amounts
of these components) are used routinely.
Such compositions produce a highly du-
rable glass product. Most elements play
one of three basic roles in glass structures:
network formers, network modifiers, and
ꢂꢂ
charge-compensating oxygen vacancy, VO,
as illustrated in Figure 3b.57
Figure 2. Macroscopic swelling in
238Pu-doped Synroc54 and 238Pu-doped
glass ceramic.57
MRS BULLETIN/SEPTEMBER 2001
701

Plutonium in Crystalline Ceramics and Glasses
ment that they do not exert a directional
effect. The actinides, as with other “hard”
polyvalent ions like Al and Zr, attract a
shield of negative ions to achieve a charge
balance that makes plutonium a potential
glass network intermediate, as illustrated
in Figure 4.
The valence of actinides in glasses has
been determined by optical-absorption
spectroscopy, extended x-ray absorption
fine structure (EXAFS) spectroscopy, and
x-ray absorption near edge structure
(XANES) spectroscopy. In addition, the
valence state of actinides can be reliably
determined through examining their bond-
ing properties using x-ray photoemission
spectroscopy. All of these methods identi-
fied the normal valence state of plutonium
in a borosilicate glass matrix as Pu(IV) and
generally at a high coordination number
of 6–8. In the melts prepared under flow-
ing oxygen, no valence higher than Pu(IV)
could be obtained, but in a reducing at-
mosphere of flowing CO/CO2 or excess
graphite, plutonium could be reduced to
Pu(III).
As with ceramics, the ꢀ decay of pluto-
nium can lead to some changes in structure
and a potential degradation of properties
in glass systems. Self-radiation effects have
been studied in a wide range of relevant
glass compositions containing 238Pu.76 Be-
cause of the already random structure of
these glasses, the effects of self-radiation
are generally small at the ambient tempera-
tures expected over the decay time for
plutonium. This is illustrated in Figure 6,
where the maximum volume expansions or
compactions from self-radiation damage
are only of the order of 1%. Under condi-
tions of elevated temperatures, such as in
the presence of fission products, data on
radiation effects are limited. In this situa-
tion, the combined effects of radiation
damage and the high mobility of defects
and ions in the glasses could lead to even
less degradation because of annealing
processes; however, increased degradation
due to phase separation may also occur.
Figure 4. Hypothetical borosilicate glass structure; primarily formed of chains of borate
and silicate polyhedrons. Lithium, sodium, and calcium glass modifiers create nonbridging
oxygens in the network and provide charge balance in the vicinity of the plutonium-oxygen
polyhedrons. (Courtesy of D. McKeown.)
occupy 60–85 wt% of the structure as well as
up to 25 wt% intermediates, and 15–40 wt%
are modifiers.
There have been a variety of glass sys-
tems studied for the immobilization of
actinides, including plutonium. Among
these systems are borosilicate compositions,
lanthanide silicates, and iron phosphate
systems.26 The latter two glass systems were
expected to have a high degree of compati-
bility with actinide oxides and have been
found to produce actinide glass products
that can be more durable than the HLW
glass compositions currently in production.
In fact, a lanthanide silicate is currently
used in the Savannah River Am/Cm
vitrification75 and a sodium alumino phos-
phate has been selected as a waste form in
Russia.14
The ability to include significant amounts
of plutonium in glass systems was demon-
strated more than 20 years ago. For ex-
ample, 7 wt% PuO2 was dissolved into a
HLW borosilicate glass composition,19 and
the solubility of PuO2 in the German GP98
glass was determined to be 4.4 wt%.74 More
recently, even higher plutonium loadings
have been demonstrated on a laboratory
scale for selected systems26 (see Table I).
Others have succeeded in dissolving over
11 wt% PuO2 in lanthanide silicate glasses
using several PuO2 source materials, but
the maximum loadings have not yet been
determined.22 Feng et al.25 investigated the
possibility of including plutonium at a
much higher concentration (at least 25 wt%
PuO2) when melted under reducing con-
ditions. Hence, plutonium can be included
in many glass systems. The optimum
amount may not be determined solely by
solubility considerations, but by criticality
constraints and by the effect, if any, of Pu
content on durability.
Long-Term Disposition
Chemical durability and resistance to
self-radiation damage are the most impor-
tant technical performance properties of a
radioactive waste form. Leaching provides
a physical measure of how well the glass
or ceramic structure can incorporate radio-
nuclides and retain them in its matrix if
exposed to water in a repository setting.
Resistance to self-radiation damage deter-
mines how rapidly the structure and
properties of either a ceramic or glass will
degrade due to the effects of ionization
and elastic nuclear collisions from the
ꢀ particles and recoil nuclei released by
Several factors influence the valence and
coordination of actinides in glasses: the
stability of a particular valence state, the
oxidation–reduction potential of the melt,
the size of the actinide ion relative to the
site it occupies, and the coordination af-
forded by the crystal lattice in the glass. In
common with other “hard” polyvalent ions,
there is no preferred directional bonding
of plutonium. The 5f orbitals are suffi-
ciently shielded from the ionic environ-
702
MRS BULLETIN/SEPTEMBER 2001

Plutonium in Crystalline Ceramics and Glasses
Figure 5. Compositional ternary diagram displaying high-level waste (HLW), transuranic (TRU), and Pu glasses; the coordinates given at the apex
of the striped triangle give the position in the (glass former, glass modifier, intermediate) larger ternary diagram. (After References 72 and 73.)
terization Center in the United States
(MCC1), the soxhlet test used in Europe,
the MCC3 test using powdered samples,
and more recently the Product Consis-
tency Test (PCT) developed at Savannah
River. The temperature of testing is most
frequently 90ꢃC, but can range from room
temperature to 200ꢃC. The essential role
played by the formulation of the glass is
taken into account in expressing leaching
“as normalized” by dividing the concen-
tration measured in the leachate for any
given component by its fraction in the
glass. The normalized release of the com-
ponent is therefore expressed as a concen-
tration normalized to its content in the
glass (g/l). For elements that are highly
soluble and leach congruently, such as
boron, lithium, and sodium, the normal-
ized concentration truly reflects the glass
durability. Other elements will display
their “percolating” role, that is, the capa-
bility to slow the loss of the more mobile
alkali elements and boron. The variation
in size of the glass samples tested and the
volume of leachant used are also corrected
by dividing the normalized concentration
by the ratio of the surface area of glass ex-
posed to the solution volume (S/V, in
ꢄ1
m ). In this case, the leaching is expressed
in g/m2, as presented in Figure 7. Leach-
ing periods of a few days at 90–100ꢃC in
deionized water have been used. It is clear
that plutonium glasses and ceramics are
more durable than most familiar commer-
cial glass systems and that plutonium is
better retained in the glass and ceramics
than in the other components. This is pri-
marily due to the fact that the plutonium
diffusion coefficient in glass is extremely
Figure 6. Macroscopic volume changes
in several 238Pu-doped simulated
nuclear-waste glasses.57,77
ꢄ18
ꢄ1
low (10 cm2 s ). Second, the leaching
of plutonium becomes less congruent
with increasing temperature or decreasing
leachate-renewal frequency. Better under-
standing of plutonium leaching behavior
was attained by varying both the tempera-
ture (room temperature to 100ꢃC) and the
water-renewal rate (static, various renewal
rate and soxhlet reflux).78
the decay of plutonium incorporated in
the atomic structure.
For leach testing, many institutions
worldwide have developed different pro-
tocols; it is often difficult to compare the
diverse data presented in the literature.
The most commonly used tests include
those developed by the Material Charac-
The degradation effects of self-radiation
damage from Pu decay in most of the crys-
talline phases of interest and for many dif-
MRS BULLETIN/SEPTEMBER 2001
703

Plutonium in Crystalline Ceramics and Glasses
Acknowledgments
The authors wish to express their ap-
preciation to Lou Vance of the Australian
Nuclear Science and Technology Organi-
zation in Menal (Sydney), Australia, and
G. Wicks and D. Karraker of the Westing-
house Savannah River Co., Aiken, South
Carolina, for their collaboration in the writ-
ing of the original book chapter from which
this article was extracted. William J. Weber
was supported by the Division of Ma-
terials Science and Engineering, Office of
Basic Energy Sciences, U.S. Department of
Energy, during preparation of this article.
References
1. N. Jacquet-Francillon, R. Bonniaud, and C.
Sombret, Radiochim. Acta 25 (1978) p. 231.
2. R.A. Bonniaud, N.R. Jacquet-Francillon, and
C.G. Sombret, in Scientific Basis for Nuclear Waste
Management II, Vol. 15, edited by D.G. Brookins
(Elsevier Science, 1983) p. 183.
3. D.G. Karraker, J. Am. Ceram. Soc. 65 (1982)
p. 53.
4. D.J. Lam, B.W. Veal, and A.P. Paulikas, in X-Ray
Photoemission Spectroscopy (XPS) Study of Uranium,
Neptunium, and Plutonium Oxides in Silicates-
Based Glasses (ACS Symp. Ser. 216), edited by
W.T. Carnall and G.R. Choppin (American
Chemical Society, Washington, DC, 1983) p. 145.
5. W.J. Weber and F.P. Roberts, Nucl. Technol. 60
(1983) p. 178.
6. W. Lutze and R. Ewing, eds., Radioactive Waste
Forms for the Future (North-Holland Press,
Amsterdam, 1988).
7. High-Level Waste Borosilicate Glass: A Com-
pendium of Corrosion Characteristics, Vol. 1, DOE-
EM-0177 (U.S. Department of Energy, Office of
Waste Management, 1994).
8. National Academy of Sciences, W.K.H.
Panofsky (Study Chair), “Management and
Disposition of Excess Weapons Plutonium,”
Committee on International Security and Arms
Control (National Academy Press, Washington,
DC, 1994).
9. S.G. Cochran, W.H. Dunlop, T.A. Edmunds,
L.M. MaClean, and T.H. Gould, Fissile Material
Disposition Program—Final Immobilization Form
Assessment and Recommendation, UCRL-ID-
128705 (1997).
10. L. Gray and T.H. Gould, Immobilization
Technology Down-Selection Radiation Barrier Ap-
proach, UCRL-ID-127320 (1997).
11. N.H. Kuehn, Can-in-Canister Immobilization
Demonstration, WSRC-MS-96-0072 (Westinghouse
Savannah River Co., Aiken, SC, 1996).
12. N.H. Kuehn, Can-in-Canister Cold Demon-
stration in DWPF, WSRC-TR-96-0226 (Westing-
house Savannah River Co., Aiken, SC, 1996).
13. D.T. Rankin and T.H. Gould, “Plutonium
Immobilization Program: Can-in-Canister,” pre-
sented at the 101st American Ceramic Society
Meeting, Indianapolis, IN, 1999.
14. Joint U.S./Russian Plutonium Disposition
Study, Appendices to the Immobilization Alter-
native, Westinghouse Savannah River Co. Report
WSRC-TR-96-0043, Rev. 5, August 15, 1996 (U.S.
Department of Energy, Washington, DC, 1996).
15. Y.I. Matyunin and L.J. Jardine, Investigations
of Plutonium Immobilization into the Vitreous Com-
Figure 7. Normalized leaching of silicon, boron, and plutonium from various glasses.
ferent glasses are fairly well known. Largely
because of multiple uses (and sponsors)
for ceramics in high-radiation environments
and the continual support of fundamental
research, an atomic-level understanding of
dynamic self-radiation damage processes
in ceramics is emerging that provides pre-
dictive models of performance under all
disposition scenarios, as illustrated in Fig-
ure 8 for crystalline phases, Gd2Ti2O7 and
ZrSiO4, proposed for the immobilization
of plutonium. Similar understanding and
models could be developed for glasses.
One of the more exciting outcomes from
the fundamental research has been the
recent discovery79,80 of a chemically du-
Figure 8. Relative radiation damage
rable, radiation-resistant class of ceramics
(i.e., radiation-induced amorphous
(gadolinium zirconate pyrochlores) that
can readily accommodate plutonium and
fraction) as a function of cumulative
ꢀ-decay events and equivalent storage
other actinides yet remain structurally
unaffected by self-radiation damage for
millennia, as illustrated in Figure 8. This
discovery has been recognized by the U.S.
Department of Energy as one of the top
101 discoveries within the Office of Science
during the past 25 years.81 Application
of this breakthrough technology could
eliminate issues involving the degrada-
tion of ceramic waste forms due to self-
radiation effects.
times for Gd2Ti2O7, ZrSiO4, and
Gd2Zr2O7 containing 10 wt% 239Pu. The
radiation resistance of Gd2Zr2O7 was
discovered by a team of researchers
led by the University of Michigan
and Pacific Northwest National
Laboratory,79,80 which has been
recognized by the U.S. Department
of Energy as one of the top 101
discoveries during the past 25 years
within the Office of Science.81
Conclusion
cans of a plutonium ceramic suspended
in canisters of HLW glass produced at
Savannah River. In Australia, the govern-
ment has decided to use in situ vitrifica-
tion (ISV) to stabilize the plutonium in the
most contaminated pits of the Maralinga
nuclear-weapons test range.82
Two final examples will be cited to at-
test to how glasses and ceramics provide
industrial solutions to the global problems
of plutonium proliferation and environ-
mental contamination. In the United States,
plutonium will be disposed of in small
704
MRS BULLETIN/SEPTEMBER 2001

Plutonium in Crystalline Ceramics and Glasses
positions, Lawrence Livermore National Labo-
ratory Preprint UCRL-JC-130180, Rev. 1 (1998).
16. R.A. Bonniaud, N.R. Jacquet-Francillon, and
C.G. Sombret, in Proc. Int. Symp. on the Scientific
Basis for Nuclear Waste Management (Plenum
Press, New York, 1980) p.117.
(8) (1986) p.1181.
Academic Publishers, Chur, Switzerland, 1980)
p.341.
34. W.J. Weber, J.Mater. Res. 5 (1990) p.2687.
35. W.J. Weber, J. Am. Ceram. Soc. 76 (1993)
p. 1729.
57. J.A.C. Marples, J.T. Dalton, A.R. Hall,
A. Hough, K.A. Boult, G. Malow, V. Beran,
J. Borchardt, W. Lutze, H. Matiske, N. Jacquet-
Francillon, F. Laude, A. Magnier, E. Vernaz,
W. Heirmerl, and G. Schutz-Lembach, Nucl.
Instrum. Methods Phys. Res., Sect. B 32 (1988)
p.480.
36. M.M. Abraham, L.A. Boatner, C.B. Finch,
and R.W. Reynolds, Phys. Rev. B 3 (1971) p. 2864.
37. W. Kolbe, N. Edelstein, C.B. Finch, and
M.M. Abraham, J. Chem. Phys. 60 (1974) p. 607.
38. L.A. Boatner and M.M. Abraham, Rep. Prog.
Phys. 41 (1978) p. 87.
17. J.A.C. Marples, J.T. Dalton, A.H. Hall,
A. Hough, K.A. Boult, G. Malow, V. Beran,
J. Borchardt, W. Lutze, and H. Matiske,
N. Jacquet-Francillon, F. Laude, A. Magnier,
E. Vernaz, C. Sombret, W. Heimerl, and
G. Schutz-Lembach, Eur. Appl. Res. Rept.-Nucl.
Sci. Technol. 3 (3) (1981) p.395.
58. R.E. Williford, B.D. Begg, W.J. Weber, and
N.J. Hess, J. Nucl. Mater. 278 (2000) p.207.
59. M. Freshley and D. Carroll, Trans. Am. Nucl.
Soc. 6 (1963) p. 348.
39. W.K. Kot, N.M. Edelstein, M.M. Abraham,
and L.A. Boatner, Phys. Rev. B 47 (1993) p.3412.
40. I.S. Poirot, W.K. Kot, N.M. Edelstein, M.M.
Abraham, C.B. Finch, and L.A. Boatner, Phys.
Rev. B 39 (1989) p. 6388.
18. N.J. Hess, W.J. Weber, and S.D. Conradson,
J. Nucl. Mater. 254 (1998) p. 175.
60. National Academy of Sciences, “Glass as a
Waste Form and Vitrification Technology: Sum-
mary of an International Workshop,” Board on
Radioactive Waste Management (National
Academy Press, Washington, DC, 1996).
61. J.E. Marra, M.A. Baich, A.P. Fellinger, B.J.
Hardy, T.M. Jones, C.B. Miller, D.H. Miller, D.K.
Peeler, T.K. Snyder, M.E. Stone, J.C. Whitehouse,
and D.C. Witt, in Environmental Issues and Waste
Management Technologies in the Ceramic and Nu-
clear Industries IV, Vol. 90, edited by J.C. Marra
and G.T. Chandler (1999) p. 391.
19. M.J. Plodinec, Development of Glass Composi-
tions for Immobilization of SRP Waste, DP-1517,
Savannah River Site (1979).
41. Hj. Matzke, Nucl. Instrum. Methods Phys.
Res., Sect. B 32 (1988) p. 455.
42. R.C. Ewing, W. Lutze, and W.J. Weber,
J.Mater. Res. 10 (1995) p. 243.
20. J.K. Bates, J.W. Emery, J.C. Hoh, and T.R.
Johnson,Ceram. Trans. 61 (1995) p.447.
43. W.J. Weber, R.C. Ewing, C.R.A. Catlow,
T. Diaz de la Rubia, L.W. Hobbs, C. Kinoshita,
Hj. Matzke, A.T. Motta, M. Nastasi, E.K.H. Salje,
E.R. Vance, and S.J. Zinkle, J. Mater. Res. 13
(1998) p.1434.
21. N.E. Bibler, W.G. Ramsey, T.F. Meaker, and
J.M. Pareizs, in Scientific Basis for Nuclear Waste
Management XIX, edited by W.M. Murphy and
D.A. Knecht (Mater. Res. Soc. Symp. Proc. 412,
Pittsburgh, 1996) p. 65.
44. R.C. Ewing, W.J. Weber, and W. Lutze, in
Disposal of Weapons Plutonium, edited by E.R.
Merz and C.E. Walter (Kluwer Academic Pub-
lishers, Dordrecht, 1996) p. 65.
22. J.D. Vienna, D.L. Alexander, H. Li, M.J.
Schweiger, D.K. Peeler, and T.F. Meaker, Pluto-
nium Dioxide Dissolution in Glass, PNNL-113446
(Pacific Northwest National Laboratory, 1996).
23. J.K. Bates, A.J.G. Ellison, J.W. Emery, and
J.C. Hoh, in Scientific Basis for Nuclear Waste
Management XIX, edited by W.M. Murphy and
D.A. Knecht (Mater. Res. Soc. Symp. Proc. 412,
Pittsburgh, 1996) p. 57.
62. G.G. Wicks, “Advantages and Limitations
of Disposing of Pu in Glass,” presented to the
Committee on International Security and Arms
Control, National Academy of Sciences, Wash-
ington, DC, WSRC-MS-93-149, Westinghouse
Savannah River Co. (1993).
45. U.S. Department of Energy Record of Decision
for the Storage and Disposition of Weapons Usable
Fissile Materials, Programmatic Environmental
Impact Statement (U.S. Department of Energy,
Washington, DC, January 1997).
63. G.G. Wicks, M.J. Plodinec, and J.M. McKibben,
“Leveraging of Resources for Vitrification of
Plutonium,” presented to the Immobilization
Task Team on Plutonium Disposition, Aiken,
SC, 1994.
46. Strategic Plan, Storage and Disposition of
Weapons Usable Fissile Materials (U.S. Department
of Energy, Washington, DC, August 1997).
47. Hj. Matzke and J.van Geel, Radwaste Mag. 3
(2) (1996) p. 71.
24. C.J. Mertz, A.J. Bakel, J.K. Bates, D.B. Cham-
berlain, J.A. Fortner, J.M. Hanchar, and S.F.
Wolf, Ceram. Trans. 87 (1998) p. 211.
64. G.G. Wicks, J.M. McKibben, M.J. Plodinec,
and W.G. Ramsey, in Disposal of Weapon Pluto-
nium, Disarmament Technologies,Vol. 4, edited by
E.R. Merz and C.E. Walter (Kluwer Academic
Publishers, Dordrecht, 1996).
25. X. Feng, H. Li, L.L.D.L. Li, J.G. Darab,
M.J. Schweiger, J.D. Vienna, B.C. Bunker,
P.G.Allen, J.J. Bucher, I.M. Craig, N.M. Edelson,
D.K. Shuh, R.C. Ewing, L.M. Wang, and
E.R. Vance, in Environmental Issues and Waste
Management Technologies in the Ceramic and Nu-
clear Industries IV, Vol. 93, edited by J.C. Marra
and G.T. Chandler (American Ceramic Society,
Westerville, OH, 1999) p. 409.
48. V.M. Oversby, C.C. McPheeters, C. Degueldre,
and J.M. Paratte, J. Nucl. Mater. 245 (1997) p.17.
49. C. Degueldre, U. Kasemeyer, F. Botta, and
G. Ledergerber, in Scientific Basis for Nuclear
Waste Management XIX, edited by W.M. Murphy
and D.A. Knecht (Mater. Res. Soc. Symp. Proc.
412, Pittsburgh, 1996) p. 15.
65. K.M. Marshall, J.C. Marra, J.T. Coughlin,
T.B. Calloway, R.F. Schumacher, J.R. Zamecnik,
and J.M. Pareizs, “Development of the Pluto-
nium Oxide Vitrification System,” Waste Man-
agement ’98, March 1–5, Tucson AZ, in Proc.
American Nuclear Society, Session 65, presentation
No. 6, in CD-ROM only (American Nuclear
Society, La Grange Park, IL, 1998).
50. C. Degueldre and J.M. Paratte, J. Nucl.
Mater. 274 (1999) p.1.
26. W.G. Ramsey, N.E. Bibler, and T.F. Meaker,
“Compositions and Durabilities of Glasses for
Immobilization of Plutonium and Uranium,”
Waste Management ‘95, “HLW, LLW, Mixed
Wastes and Environmental Restoration-Working
51. P.G. Boczar, M.J.N. Gagnon, P.S.W. Chan,
R.J. Ellis, R.A. Verrall, and A.R. Dastur, Can.
Nucl. Soc. Bull. 18 (1) (1997) p.2.
66. K.M. Marshall, J.C. Marra, J.T. Coughlin,
T.B. Calloway, R.F. Schumacher, J.R. Zamecnik,
and J.M. Pareizs, in Proc. Third Topical Meeting
on DOE Spent Nuclear Fuel and Fissile Materials
Management,Vol. 1 (American Nuclear Society,
La Grange Park, IL, 1998) p. 388.
52. K.E. Sickafus, R.J. Hanrahan Jr., K.J.
McClellan, J.N. Mitchell, C.J. Wetteland, D.P.
Butte, P., Chodak, K.B. Ramsey, T.H. Blair, K.
Chidester, Hj. Matzke, K. Yasuda, R.A. Verrall,
and N. Yu, Am. Ceram. Soc. Bull. 78 (1999) p.69.
53. E. Browne, J.M. Dairiki, and R.E. Doebler, in
Table of Isotopes, 7th ed., edited by C.M. Lederer
and V.S. Sherley (John Wiley & Sons, New York,
1978) p. 1457.
Towards
record 23,828 (1995).
a Clearer Environment,” CD-ROM
27. T.F. Meaker, W.G. Ramsey, J.M. Pareizs,
D.G. Karraker, and D.E. Day, Ceram. Trans. 72
(1996) p. 409.
67. R.F. Schumacher, W.G. Ramsey, F.M. Johnson,
T.M. Jones, D.H. Miller, and B.J. Hardy, Ceram.
Trans. 87 (1998) p.3.
28. V.V. Kushnikov, Yu.I. Matyunin, T.V. Smelova,
and A.V. Demin, in Scientific Basis for Nuclear
Waste Management XX, edited by W.J. Gray and
I.R. Triay (Mater. Res. Soc. Symp. Proc. 465,
Pittsburgh, PA, 1997) p. 55.
68. A. Paul, Chemistry of Glasses, 2nd ed.
(Chapman & Hall, London, New York, 1990).
69. W. Vogel, Glass Chemistry, 2nd ed. (transla-
tion of the German 3rd ed.) (Springer-Verlag,
Berlin, 1994).
54. K.A. Boult, J.T. Dalton, J.P. Evans, A.R. Hall,
A.J. Inns, J.A.C. Marples, and E.L. Paige, The
Preparation of Fully Active Synroc and Its Radia-
tion Stability—Final Report, October 1988, AERE-
R-13318 (Harwell Laboratory, Harwell, UK, 1988).
55. E. Vernaz, A. Loida, G. Malow, J.A.C.
Marples, and Hj. Matzke, in Proc. 3rd EC Conf.
on Radioactive Waste Management and Disposal,
edited by L. Cecille (Elsevier, London, 1991)
p.302.
29. T.D. Chikalla and R.P. Turcotte, Radiat. Eff.
19 (1973) p. 93.
30. F.W. Clinard Jr., L.W. Hobbs, C.C. Land,
D.E. Peterson, D.L. Rohr, and R.B. Roof, J.Nucl.
Mater. 105 (1982) p.248.
70. D.K. Peeler and T.F. Meaker, Results of an
Intra-Laboratory Study of Glass Formulation for the
Immobilization of Excess Plutonium, SRT-PUM-
97-0017 (Westinghouse Savannah River Co.,
Aiken, SC, 1997).
31. F.W. Clinard Jr., D.E. Peterson, and D.L.
Rohr, J. Nucl. Mater. 126 (1984) p. 245.
32. F.W. Clinard Jr., D.L. Rohr, and R.B. Roof,
Nucl. Instrum. Methods Phys. Res., Sect. B1 (1984)
p.581.
71. D.K. Peeler (personal communications).
72. G.G. Wicks, W.D. Rankin, and S.L. Gore, in
Scientific Basis for Nuclear Waste Management
VIII, edited by C.M. Jantzen, J.A. Stone, and
56. G. Malow, J.A.C. Marples, and C. Sombret,
in Radioactive Waste Management and Disposal,
edited by R. Simon and S. Orlowski (Harwood
33. F.W. Clinard Jr., Am. Ceram. Soc. Bull. 65
MRS BULLETIN/SEPTEMBER 2001
705

Plutonium in Crystalline Ceramics and Glasses
R.C. Ewing (Mater. Res. Soc. Symp. Proc. 44,
Pittsburgh, 1985) p. 171.
73. W.G. Ramsey and G.G. Wicks, Ceram. Trans.
9 (1990) p. 257.
76. W.J. Weber, R.C. Ewing, C.A. Angell, G.W.
J. Mater. Res. 14 (1999) p. 4470.
80. W.J. Weber and R.C. Ewing, Science 289 (2000)
p. 2051.
81. “Decades of Discovery” Home Page, U.S. De-
partment of Energy, http://www.sc.doe.gov/
feature_articles_2001/June/Decades/index.html
(accessed August 2001).
Arnold, A.N. Cormack, J.M. Delaye, D.L.
Griscom, L.W. Hobbs, A. Navrotsky, D.L. Price,
A.M. Stoneham, and M.C. Weinberg, J. Mater.
Res. 12 (1997) p. 1946.
74. C.T. Walker and U. Riege, in Ceramics in
Nuclear Waste Management, CONF-790420, ed-
ited by T.D. Chikalla and J.E. Mendel (1979)
p. 198.
75. A.P. Fellinger, M.A. Baich, B.J. Hardy, G.T.
Jannik, T.M. Jones, J.E. Marra, C.B. Miller, D.H.
Miller, D.K. Peeler, T.K. Snyder, M.E. Stone, and
D.C. Witt, in Scientific Basis for Nuclear Waste
Management XXII, edited by D.J. Wronkiewicz
and J.H. Lee (Mater. Res. Soc. Symp. Proc. 556,
Warrendale, PA, 1999) p. 367.
77. W.J. Weber, N.J. Hess, S.D. Conradson, and
J.D. Vienna, Plutonium Futures—The Science,
Conf. LA-13338-C (Los Alamos National Labo-
ratory, Los Alamos, NM, 1997) p. 25.
78. E.Y. Vernaz and N. Godon, in Scientific Basis
for Nuclear Waste Management XV, edited by
C. Sombret (Mater. Res. Soc. Symp. Proc. 257,
Pittsburgh, 1992) p. 37.
82. P.J. McGlinn, K.P. Hart, R.A. Day, J.R. Harris,
J.A. Weir, and L.E. Thompson, in Scientific Basis
for Nuclear Waste Management XXI, edited by
I.G. McKinley and C. McCombie (Mater. Res.
Soc. Symp. Proc. 506, Warrendale, PA, 1998)
p. 239.
ꢀ
79. S.X. Wang, B.D. Begg, L.M. Wang, R.C.
Ewing, W.J. Weber, and K.V. Govidan Kutty,
706
MRS BULLETIN/SEPTEMBER 2001
www.mrs.org/publications/bulletin