Radiation damage in nuclear materials

Nuclear Instruments & Methods in Physics Research S .Cfl,,i’B

1. Introduction The slowing-down, hcnec the clcctronic and nuclear stopping. of high cncrgy heavy ions with ma\s numbers bctwcon about 75 and 160. and cncrgics of aboul 70 to 100 MoV. the fission products, is the main SOIIIKC of cncrgy in nuclear reactors for large scale olcctricity production. which covers up to 75”; of the total clectricity produced in some countries. Additional radiz tion cffccts occur in nuclear matcri&i due to fast neutrons and due to rxiioactivc decay. The main fcaturcs and the basic principles of radiation damage in ceramic nuclear fuels (and other crystalline i~is~~i~~~~~rs) wcrc trcatcd by the proscnt author in an invited paper at the 1st Confcrencc on Radiation Effects in Insul;~tars, REI-I [I]. Later. at REI-I, the prcscnt author contributed ;I second invited paper to the topic of radialion cffccts in nuclear materials [2] which scrvcd also as an introduction to a workshop on radiation effects in nuclear waste materials. contained in the proceedings of REI-4 [3]. In addition. a rcccnt rrcvieu [4] on scif-radixtion cffccta in xtinidc compounds covcrs the prcscnt knowlcdgc of fh~ conscquc’nccs 01 chemical propcrtics of tu-decay on physical xxi (actinicic-containing) nuclear matcriais. Bcc;tuse of the present papa is r;lthcr thcsc previous articles. short

and

concentrates

on summarizing in nuclcx

the

new

cffccts

since REI-3,

in the past four years. Bel’orc

hcncc

new results

arc treated,

the diffcrcnt

damaging

some sources

in-

mutcrials gained

sights on radiation

fundamental in nuclear

thcsc

aspccl materials

of arc

and 4omc propertics of the nuclear materials dealt with in the prexnt paper arc given. summarized.

Studying damage cffccts in the rather complex nuclear materials scrvcs a twofold purpose: thcrc is the aspect of technological needs and of demands of liccnsinp authorities, but thcrc is also the challenge of tcsting and applying models and mcchnnismc devclopcd in \tudics of damage cffccts in simpler systems. The aim is to untlcr~tand the formation. accumulation and thcrmal rccovcry of damage, and the effects on physical and chemical

propcrtics

sources

occurring

reactor,

of ii atorugc

of a repository Since

in

of the large variety fhc

cnvironmcnt

facility

of spent

;I nucicar

nuclear

fuel

and

for nuclc~tr w;tstc. is ;I ~(~tltrjbuli(~~i

thi5 manuscript

cncc dcalinp

of damage

of

with

arc nonmctais.

incubators.

the materials

and prcdominantiy

fects in struclural

(metallic)

oxides.

nucicar

lo ;I crtnfcrtrcatcd

here

Danwgc

matarinls

cf-

such ;IS

diffcrcnt steels and zirconium ~rlloys will not bc dealt with. Rather. the ceramic nuclear fuels and matrices for solidification of liquid high lcvcl radioactive waslc (k1L.W) will bc trcalcd. The most frcqucntly used ccramic

nuclear

high melting

fuel ix UC),. point,

nonstctichictmetr~,

a tluoritc-type

ouidc

with

;t

T,, = 3150 K. and ;I Iargo range ot cstcnding

from

ahout

UC)i.,,i

to

is the fuci of today‘s clcctricity p]-o~i~I~in~ light and heavy water reactors. A mixed ctxidc (U. PufO, is also used to sonic cntcnt. The monocarhidcs anii mononitridcs of U and Pu. hence UC, UN. CU. Pu)C and CU. Pu)N arc rcl;tcd as so-called advanced fuels for liquid metal-cooled hrccdcr rcaclors (LMFBRs) operated with fast ncuUO> ,i at

trans.

- 7700 K. UO,

These

materials

arc of the NaCI-structure

have also very high melting

points,

and

e.g. q,, = 27X0 K for

UC and q,, = 3035 K for UN [S]. Most damage cffccts

in all these fuel materials cess. The second large class nuclear

area

are

arc due to the fission

and thus

pro-

of oxides of interest for

matrices

solidification

in the

damage Finally,

the

tailor-made optimized

for

ceptablc

glass

the latter

the

rates

molten

losses

against

least.

resulting

SO,,

IO-IS

AI,O,, The

many

against

wt.55 itself

rcproccssing).

More

about

30

about

For

specific

generation cal

assembly

“synthetic nantly)

of

Ba-hollanditc

thcsc

tivc

Table

[h],

studied

of

the

to understand

damage effects incorporated

the increase

ion

the

beams

slowing

down

of

recoil

atoms

of

Three

materials

damage.

(iii)

fission.

and

for

0.0005

to 0.001

;I

CaTiO,.

CaZrTi,O,.

all

sources.

flowevcr.

order

of magnitude

pnrametcr

arc

cffccts.

arc due to radioacclcmcnts,

crcasc

increase

by only

age by the inbetwccn. cadcs

wcrc

-

100

Defect

(with

100

high

in UO,

energy

all

cu-particle

by

)

kcV

recoil

annealing local

of about one damage (in-

(csscntially

daughter the

is

damage

damage (lattice

and fission

in

about

saturation) three

is ;I diffcrcnce

a-decay

indi-

bctwccn (or

between I ‘:;

and the producing

by e.g. O.OS!;;,

sources for

rcfs. alone,

damage.

paramctcr

0. I dpa, again

-

due

(see

cy-particles

keV

Measurable

- 0. I$; ). with

in

an exam-

used

and a maximum there

to

and vacancies iseillus-

damage

dpa,

at about

-

in lattice

three

rcachcd

As

parameter

sources

of

the

changes

(i) damage due to c-particles

atoms

[I .2]

for

normalized

different.

due to cu-decay, hence

recoil

if

the resulting

of intcrstitials dnmagc

confcrcnccs is decisive

Even

of the lattice

details):

damage

REI

source

can bc very

l’ormation

starts

materials

radioactive

properties

second is

at previous

per atom (dpa),

A typi-

(prcdomi-

radiation

physical

heavy

and

1ILW

pcrovskitc

and similar

the

cncrgctic

damage.

catcd by a change

are tested.

consisting

displacements

(ii)

from

matrices

and zirconolitc

i.c.

and of the

radiation

[1.7.X] for

(fission

products

as potential

minerals,

sources.

ion implan-

with

damage sources for nuclear

of

trative.

HLW.

elements

effects

to the

some MgO, wt.5

incorporate

components

materials.

decay

to

BaAI.Ti,,O,,,

also

or

due

and waste matrices.

fuels

the type of the damage

plc.

wt.‘!:

rcvicw [?I.

ceramics

SYNROC titanatc

individual

thcrcforc

streams. some

ccramics

rock”, of three

These In

waste

matrices,

the

last not

40~50

waste

HLW can bc found in the previous

damage

It has been shown that

cast

of

and,

and corrosion

details

Cs),

elements

and IO-15

has been done using

nuclear

products

2. Radiation

corrosion

typically

of self-heating

being the ease to simulate

main

of

studying

viscosity

materials.

product

wt.(% Na,O.

contains

as

furnace

TiO,,

actinides

motivation

atoms

When

for

access to the

X-20

CaO-and

some

recoil

stability, attack

have all to bc optimized.

contain

both

the decay of actinidcs.

tcmpcraturc.

cffccts

much work

with

ac-

water

different

tation

techniques,

crystalliration

B-O,,

heavy

conscqucnces

fission

having

and

glass

products

HLW

products,

melting

damage

to the

decay are to bc considered.

arc

as diverse

propcrtics

the

Fc20,.

water

(of e.g. the fission

resistance

The

against

the

the glasses

and good long-time

molten

incorporating

waste,

fabrication

of ground

glass,

bctwccn

Hcncc.

rcsistancc

Thcrcforc,

cvaporativc of

scale

properties

cvcnt

repository.

purpose.

large

including

the unlikely in

their

cffccts.

to the radioactive

of radioac-

tive waste. HLW, originating from the rcproccssing of spent nuclear fuels. is generally vitrified for safe storage in a deep dry geological formation, a repository. The matrices used arc complex borosilicatc glasses for

predominantly

the cu-decay (c.g. U in the decay of Pu).

atoms) very

tcmpcraturcs)

of

damfalling

dcnze the

as-

fission

I

Properties

of different

damage xurccs

in UO,

Energy

R:mgc

Fraction

[keV]

[pm1

nucleal stopping

Median

Number

of defects

formed N

i

light

fission product Median

of

Y.5000

Y

= 0.03

30000

heavy

fission product u-particle

alone

h7000

7

= 0.05

60000

= 5000

= I2

= 0.01

= 200 = 1200

Recoil atom of a-decay

= Y5

= 0.075

= 0.‘)

30

= 0.015

= O.YS

Ion implantation (40 keV Xe) Neutrons

have u large mean free path ( = I cm). The maximum energy E,,,,,, ol a I MeV

= 20 keV. This primary

knock-on

= 500 neutron

imparted

atom, pka. creates an isolated small cascade with ahout 250 defects.

on ;I U-atom

in UO,

is

b and y-decay cause very

few isolated atomic defects.

1. FUNDAMENTAL

ASPECTS

dE/dR eV/S 1500

1000

v. - logcm/s

able basic information materials

[1.2,5]. Also.

cnvironmcnts

therefore rather

not

was published this

will

of the oxides, the operating temperatures

of US

itrc

in high-radia-

(U.

[ 131. WC will

previous

bc discussed here. Due to the low thermal conductivity

bcforc

summary

effects of materials

repeat

;I summary

insights

cffccts in nuclear

by the author

very rcccntly a workshop

experts on radiation tion

on radiation

has been summarized

hcrc

knowlcdgc,

but

bc given on new results

:md

gained in the past four years since REI-1

rather Pu)O,

high;

can diffuse

Despite

the

bccomc :imorphous has shown

ing-channeling is the fuel of

nuclear power stations.

is a ceramic of the tluoritc

structure

It

shows

fission high

;I very

good radiation

and it is prcscntly darnkigc Icvcls.

employ

UO,

isostructural

under

up to very

radiation UO,

in UO,.

much less

propcrtics dcfccts

processes

(5 to 6’:

that ;uc not specific

tics (rclativc

thus introducing

10 to 12%~ impuri-

to the mct;4 sublattice).

For metal-cooled

reactors operating with frost neutrons

and using ;I mixed

oxide with typically

-0 3 % Pu, hence (U,,,Pu,,,)Oz.

to 20 at.%

ilrc easily achicvcd. The

burnup

cffccts involved arc rather well understood

up

chcmic:kl

and will not

In

than the nonmetal

atoms

crcatcd dcfccts and

is thcrcl’orc

:md wcrc:

[IS]. The mobil-

r:ltc-controlling

of technological

interest,

for such

creep, etc. In previous work

:md recovery in UO,.

propertics

for ;I given sublattice

wcrc l’ol-

lowed as probes for damage (chkmges in lattice paramctcr. thermal trast,

or clcctric;tl

the RBS-chnnncling

conductivity. tcchniquc

tivcly dcfccts (displaced U-atoms) tice. Fig. 2 shows

1

U -defects

study

[Id].

and also

;Lrc well understood

as grain growth, sintcring, on damage ingrowth

is

backscattcr-

sublatticc

in another rcvicw

ity of mct;rl

5000; up to 5 or 6 :rt.“+ of the metal atoms :lrc fission burnup),

single crys-

the metal atoms (U,

mobile

many kinetic

of up to

(U)

N). The behavior of thermally

recently summarized

not

defect rccovcry

Rutherford

in the mct:il

reactors

and achieve dpa lcvcls

c.g.

dots

tcchniquc was used to selcctivcly

effects

the diffusion

UO1

work with UO, The

(and also in UN).

Pu) ;lrc (0,

of

[I]). In the past four years,

that instantaneous

a few percent

light-water-cooled

as such, or mixed with PuO,

pellets.

pcrl’ormancc

used in reactors

The

It

with a high mclt-

ing point CT,,,= 3150 K) and is used us sintcred

damage Icvcls,

(see ref.

cxtcnsivc ion impl:~ntation

[2].

of such fuels

temperatures

out of the oxide matrix.

high

very important

today’s electricity-producing

central

may exceed 2000°C thus that many of these

impurities

tnls

As mcntioncd above, the ceramic UO,

the

results

etc.). In con-

mcilsurcs

sclcc-

in the metal subk~t-

on dam:lgc ingrowth

during

I

in UO, KInchin-Pease value - 250

0

1; log dose,

Fig. 2. Displacement temperature

efficiency

(number

of displaced

as a function of the implantation

CJ-atoms per incoming dose anti for two difterent

40 keV

ions/cm*

ion 01‘ Kr, TC or C‘s implanted

orientations

of UOz

single crystals

I. FUNDAMENTAL

at room

[ 141. ASPECTS

, ion implantation of diffcrcnt clcments (occurring iis fission products of technological interat) into UO, single crystals of diffcrcnt orientations. Damage calculations on the basis of primary dcfcct production due to nuclear energy deposition largely ovcrcstimatc the lattice disorder: The value of 250 U-defects predicted by the theory of Kinchin-Pcasc [Ih] is not cvcn ohscrvcd for the lowest doses indicating that defect rccovcry in the collision cascade is very effective and that dcfcct recombination processes play the main role in the formation of the damage structure remaining after implantation at room tcmpcraturc. The number of surviving U-defects dccrcasa with incrcasing dose to a value of less than one: U-defect per bombarding ion, hcncc only some 0.25”C of the defects formed survive. The dccrcasing number of surviving defects does. of course. not imply that less damage is formed at higher doses. This is shown in the inset of fig. 2: the total number of surviving dcfccts approaches a saturation value. This value is rather low: it explains the good radiation stability of UO,. and is in marked contrast to the cast of formation of mctamict (amorphous) phases by radiation in many of the waste ceramics (see below). This stability of UO1 is prcdictcd by the available models huscd on structural arguments and/or on thcrmodynamical and bonding propertics, as discussed in detail in ref. [I], and was. in fact, already postulated and demon~tratcd in the first work repel-ting mctamictization to occur during ion bombardmcnt in some anisotropic oxides such as AllO,, TX), and U,O, [l7]. Fig. 2 shows also that instantancous defect recovery is oricnt~ttion-dcpcndcnt: Defect recombination in the mixed and rather dense (I 11) direction is less pronounced than in the (IOO) dircction wlhich has ;I larger atomic spacing and separate rows of 0- and U-atoms. Another so far open question was any possible mobility of U-dcfccts below room tcmpcraturc. Thcrmally crcatcd dcfccts in UO , arc oxygen vacancies and intcrstitials at 2 concentration of - 2 X IO ‘I at 1400°C and to ;I lcsscr extent uranium vacancies U, ( - IO “I) whcrcas practically no U-intcrstitials arc formed ( < U, can. howcvcr. bc IO “) [IX]. Uranium intcrstitials. formed by radiation. Thcorctical calculations on dcfcct encrgics in UO1 have yicldcd ;L high migration cncrgy uranium of X.8 cV for U,, and had actually predicted intcrstitials to be Icss mobile than uranium vacancies [IO]. In the abscncc of any tailor-made cxpcrimcnts. it was not possible so far to establish 21unique consistent relation hetwcen dcfccts (0,. 0,. U,, U,.) and observed rccovcry stages of damaged or qucnchcd UO,. This gap w’as filled recently with an in situ ion implantation _ Rutherford backscattcring - channeling experiment at 5 K and subsequent in situ annealing of the spccimen up to room temperature. followed by furnace anneals up to high tcmpcraturcs [Xl. Fig. 3 show the

.‘.’

,

,

,

,

r

rare gaslmplonled uo2

L--I

,

_L__L__.

200

100

results:

thcrc

fccts. ;I

new one below

600

800

1000 c ,, lemperolure,L

rccovcry stages for U-deroom tcmpcraturc and ;I known stage at (in this cast) - X00 K. It is gcncrally agreed that this latter stage is due to U, migration. It is. as cxpcctcd, dcpcndcnt on the damage level [?()I. being at higher dose Icvcls. shifted to higher tcmperaturcs. The stage below room tempcraturc mu\1 then bc due to U,-mobility. The substage at - 77 K can bc cxplaincd as recombination of cloe Frcnkcl pairs and - I IO K as rclcasc of U, from shallow traps. the one at As cxpcctcd, the stage below room tempcraturc and the one at high tcmpcraturcs comprise - MC; of the dcfccts each. Additional recovery stages known from c.g. rccovcry of changes in clcctrical rcsistivity or lattice paramctcr changes c;111 il()w safely be attributed to dcfccts in the oxygen sublatticc. The results complctc our knowlcdgc on lattice dcfccts in UO1 and thy also help to explain the rather high

diffusion

arc two

LOfl

main

cocfficicnts

11”; for

r~idiation-cnh~lnccd

U (or Pu) diffusion during fission: as shown in REI-4 [?I. fission rate-dependent largely athermal, tcmpcraturc indcpcndcnt values of 11”’ - IO I” cm’ s ’ wcrc observed even at the lowat temperatures used ( 100°C). The mobility of U, away from the ccntcr of the fission spike. due to the biasing force of the hydrostatic pressures formed within the spike can now bc used to explain the obscrvcd values. Another interesting aspect of U02 fuel pcrformancc‘ is ;I phcnomcnon occurring at (average) burnups ahovc about 35 GWd/tU (- 5,Y fissions in the metal sublatticc). is formed IO0 to 200 burnup tion

At

such

in the fuel

high

)*rn (e.g. ref.

is largely

of neutrons

burnups.

pcllcts

[21]).

increased leading

with

21 porous

a typical

In this

outer

region.

due to a rcsonancc to ;I local

high

ring

thickness the

01 local

absorp-

concentration

of Pu. Thcreforc, a high concentration of damage and of fission products including the fission gases Kr and Xc are formed in this “rim” zone. At the same time. a high port&y

is found in this zrmo, together

with a very

1 pm. Instead of the usual grain growth which is well known to occur in LJO, at clcvated lcrnp~rat~lre and which is well understood. WC dcat with a “q~in ,s~i~~~~,~sj~~iz pwcess’“. With 3 starting grain sizr of typically If) pm, this means that the individual as-produced grains arc “-divided” into about 1000 new small grainsThe resulting structure is shown in fig. 4a and can conveniently be described as “cauliflower structure” [ZI]. This technologically and scicntifically intcrcsting phenomenon is prcscntly studied in differing lab~)r~lt(~r~es,but the exact m~eh~~nisrn, the kinetics and the cxlent of its formation are still not small grain size of

<

known. The obvious parameters arc damage lcvcl (burnup and fission rate), amount of insoluble fissian products (Kr, Xc, I. Rb, ts, Tc. etc.), local tempcraturc, Pu-cnntcnt and oxygen potential (tocal O/Mratio). These parameters are not indcp~nd~nt: as cxample, Pu-fission is more oxidizing than U-fission. since more non-oxide forming fissirm products (c.g. Ru, Pd) arc formed in the fission elf Pu whercns tJ-fission lcads tct a higher products

~~)n~~ntrat~~~n 0f

(e.g.

Zr).

On

the

oxygen is known to migrate ent

existing

migrate

in the

0xidc

other

forming hand.

the

up the tcmperaturc

operating

fuel,

hcncc

fissittn cxcws gradi-

it should

away from the rim zone. Space dots not allow

to discuss this question

in more detail.

only given to illustrate

the potential

basic studies tm radiation

cffcrts.

The cxnmplc

is

and uscfuln~ss of

as a separate

cffcct

Fig. 4. SEM micrographs of (aI tke typicat “cauliflower“ structure of the outer porous zone in high hurnup LJO, [21] and of &I ion-i~piante~i UO, (S x

lOih

Xe-inns/cm’

at 300 keV. annealed

to S00”C in fOfCO1).

I. FUNDAMENTAL

ASPECTS

mcasuremcnt ackicvc

with

a hcttcr

problem.

well

insight

As shown

confcrcncc

controlled

in another

[ 121. high damage

tions can lcild in UO, the impurities

paramctcrs

into ;1 cttmplcx

ct)t~t~~~~~lti(~nttt this

and impurity

tics and self-intcrstitials.

thus also crating

with almost dcfcct-froc

wails).

Rutl~~rf~)rd

this

ii?]

large

tation

giving

Joscs

;I I* hctcro-

interconnected

t~~~cks~~Itt~rii1~ channeling

apparent

tions of Cs. Tc and r&t

substitutional

XL> wcrc found at high

the

01

also of clusters of VDWII-

gcncous froth“ In

conccntra-

to a kind of self-organiz;~tic,n

(and probably

invcstigatictn

to

tcchnrtiogicnl

first

indication

fr:icirnplx-

of cohcrcnt

pr~~ipit~t~(~l~ of s&id rare gases and volatile

Clcmcnts

in UOZ_ The

tcmpcr:r-

csistancc

of s&l

,Ye at room

turcs implies the cxistancc of high Itat1 prcssurcs Ctjrdcr of 10 kbar) that could conccivahly ing and/or

fracturing

first phcnomcnon tion dcmity

is compatible

obscrvcd

micrclscopy around the latter at

potential

tcmpcraturcs

pktnted

arcas

and

clcc-

110,

(cstimatcd1

single

~~-iinpl~~nt~~t~~)n to

inp channcling

conditions

investigation

on polycrystallinc

UO,

an-

oxygen

backscattcr-

[ 121.Similar

cxpcrimcnts

the obhcrvation

of :I

being clcnvagc

b~~rn~~~~rd~d layer due to

by the Xc-precipitates. in detail

These

dose in fig. 5) at the intcrfacc and undamaged

in Xc-implnntcd

mechanism

and frztcturing of the damaged suits wiJ1 bc dcscribcd

a

~~)rr~sp(~~ld~il~ to

occurring

the probable

Evidently,

can hc &taincd

Rutherford

confirmed

subdivision

builtup

crystal.

subdivision”

those of the above-mentioned

the pressure

[22].

in scanning

fuel in the rim region (fig.

of a UOZ

sirrtcred LJO,,

electron

shows the ~rnpl~int~d and the unim-

similar “cry&i

of grain

The

UOZ

of high dose Xc-implanted

the figure

snmcwhat

type

transmission

in high burnup

of oJ~~r~itin~ UO,

4b). This

by

in rcccnt

buhhlcs

of the matrix.

with the high disloca-

ph~n~~rncn(~n is cvidcnccd

tram microscopy ncalud

load to loop punctnr-

(or cloavagc)

rc-

panying

transmission

elcctmn

the damugcd

microscopy

m&~~sur~rncnts of the dcpcndencc cncrgy of the probing irregular

clscwhcrc.

between

parts of the UN single crystal. Accom-

Hc-ions

clusters and indicate

izcd disl~)c~ti(~n network

(TEM)

of channoiing

show the formation

bctwccn

damaged

axl

reactors Pu)N

and

the

js~)structu~ll

is tested as advanced,

liquid c&c

metal-cooled on radiation

(~~~l-structllr~)

second-generatiorl

fast power

reactors.

Since then,

more

cxtensivc

valuable

Rutherford

both low tcmp~r~turc

infornl~tior~

entire with

damaged increasing

damage

peaks within

wcrc observed. form

insulators

at

tCr~lp~riltUrC

oscr the

and also is

or TV s~rni~~~ndu~t~)rs, no ions

as shown in fig. 5, “‘interface

at channel

away

from

the

nr. 440 for the highest

bonding,

b~)rnb~rd~d

data show

n~i~r~~ti(~li of zone

intcl the

undamaged

crystal occurs, even at 77 K. This mobility

is probably

biased

due to damage

by the buildup

of stress gradients

formation.

As with UO,,

this obscrvn-

tion yields an caplanation

for the rather

high D’“-WI-

ucs for fissi~)n-~nhiln~~d

diffusion

stitiats. U,) were mobile

the range of the implanted

Rather,

(c.g.

to CIO,.

U-dcfccts

its metal-like

damage

dcch~~nnclin~

dose. In contrast

to other

with

and section 3.1). Additional

to product

and at room

that in l!N

channcfing

Iayer the thickness of which incrcascd

contrast

peaks”

177 K)

[5].

was c>btaincd.

hackscattering

c~~nt~nously increasing

knowl-

fuels avail-

in a monograph

study [23f using Kr- and Xc-ions showed

CU. fuel for

The

cffccts in thcsc advanced

able up to 1086 is summarized An

as fuel for space

virgin

by the stress buildup

bctwocn these two regions. The accumulated rn(~n(~njtr~~~~is considered

of

the f~~rrn~~tiorlof a local-

rcgiorrs of the crystal produced ~r~lniunl

and on the

pcraturc,

and

pr(~n~unccd

defect

in UN

in UN

hetwocn

mcnts of the damaged

in UO,.

intcr-

77 K and room tcm-

r~c(~rnbin~til~tl than

(sco ref. [Z]

U dcfccts (plobably

was cvun more

Annealing

cxpcri-

crystals showed two important recovery stages located at Wl and t3Off K. At tlrc first stage, tr~~nsf~~rrn~t~~ns of defect ciustcrs occurs leading to stress rclcxc in the distorted layer. At the second one, the clusters dissociate giving rise to the formation of dislocation lines and loops, as obscrvcd in TEM.

(‘onfirming

cvidcncc

in France

obtained

and studying clcctron WV.

ingrowth

irradiation

Variation

nation ohxtrrm

and annealing of damage under

(ix.

the

E,,

(actually

dir&ion

v;tkx

to rccovcr

tcmpcraturc

About

65%

to tire

half of thee

dcfccts

stages bcltrw

room

wcrc rccovcrcd txlow

to rccomhination

to Ui-mobility.

thus confirming

of LJ Frenkcl

320

pairs and

and cxtcnding the above

study.

As with

UO,,

these investigations

fccts in LJN have significanlfy stand fission

Problems

length

and open questions

formations

rcfated

Also,

waste forms fcrencc having

the long-tam

unlikely

gfuss with

the ground

wtttcr;

hcncc.

may not apply tct thcsc conditions.

in fracture

time,

2). One of the

possibly

the leach

produced gtasscs Icnching,

Icach rates.

tain&

The conclusions

hcyond

solution

clsc,

:malysis

the which

wcrc

-“‘Cm

formation

for

MCC

to perform weight

as “a pmr

regarded

Both

types of

have since hccn done on three

waste glasses containing French

[2S] con-

reporting

of actual gtass dissoIution”.

measurements

section

of defining

rccommcnd;rtion to just

forma-

(xc

was that

of the workshop

in addition

loss mc:isurcmcnts indicator

were all invcstigatcd

(see ref.

glass SON

[25]

typic31

to accelcratc damage

dnsc

r;ttc

h81817LlC2A2ZI,

7ti-hX and the German

14. radi-

due to possible

open questions

at

leaching

and the question of hubhle

tion due to ionization

cffccts). the

product

GP 9X/12

incrcasc in leach rates or dissolution with

damage

level

(including

fig. 7); the data for solution gls\sses showed MCC‘

the sarnc

analysis trend

were

76-h8 glass in fig. 7. The

cctrrcspnnds

to storage

times of

trf glass comptrNix, not shown for the trthcr

as that total > IO’

given

damage

for

in

of damage

niqucs

[2x].

fracture

hchavic~r lcvcl,

lengths

toughness

K,,

cxplrrincd

to

quenched-in

Kr

and possibly

mechanism,

&servcd

&tm-

irrcrc;rscs This

probably

by bubble

K,,.

Cm-doped

in hardness

(2 to 3 X IIP

to

atoms This

wcrc also

the rare gases

glasses showed

at rather

bc-

due

formation.

in

in glasses i~~ll-i~n~~~nt~d with

dccrc~c

In

most

and the incr~~sc

or SC 1291. The

3tl%

increasing

significant

by up to 100%. hc

tcch-

formation

stresses along the path of the recoil

of the tx-decay iattcr

with

to very

in fracture

indentation

of crack

dccrcascd

haviour

is

was invcstigntcd

using

the probabilities

corresponding

atso ;t

low &rmagc

Icvcls

cu-dccays/‘m’i.

addition,

density

damage

accumulation

glasses.

The

density

and volume

changes due to

wcrc

measured

chkmgcs

could

with hc

all

fitted

three tcr the

relation

I - exp( --AD}).

A(r =A( where

(a-decays/g).

the

Both

and the crnck age Icvcls,

the

reached With

the

as ;i function

two

years idcpcnd-

ing on type and ~~~n~~ntr~it~~~n of’ the waste!.

same gfassrs,

The

US version

used. Figs. h and 7 show the complete absence of any ncnts

16

of the damaged

Ttrcrcfore,

K,,. cffccts

toughness

1I

water

volume changes. stored energy, changes in hardness olytic decomposition

12

Con-

ground

at a iatcr

iand known) for freshly

typical

10

of high-level

of

by the int~r~et~(~n

8

cumulativedose,102’ a- decays/m3

Confcr-

at :I CEC

cvcnt

nccess to the tcpository

be dctcrmincd

rates

stability

6

dry

wcrc discussed the REI-4

was rcccntly summarized

1

to incor-

waste in deep

held during

/%I]. In !hc

fo radiation

glasses tailor-m&c

(rcpositorics)

in a workshop

cncc [25].

cf-

to hcttcr undcr-

poratc and safely store radioactive geological

ol’ radiation

h&cd

damage in this nuclear fuel.

cffccts in the horosilicate

will

parnllci

was dCtC?I-ITlillCd to bc

in three

IQ, attrihutcd RBS

E,,. For a low symmc-

cncrgics,

the (3.b.Z)

for U-dcfccts.

shown

W;IS rcccntly

of the cicctron cncrgy allows detcrmi-

bcitm),

37 & I cV

wcrc

results

with cncrgies hctwccn (I.3 and 2.5

of displaccmcnt

try orientation

of thcsc

1241 using the same single crystals

ap is the change in density

saturation tr~aliy the

,4 level

damaged

glass

SON

is then and

B

by each

the is the

tu-decay.

681817LtCZA2Zf.

I%)

density

at the dose II change

fraction

of

at the

the

As an cxampfc,

glass for

.4 = lt.SS 5 O.fiSc,%

SYNROC

or. with

new results

reported

cccdines.

for

Cm-dnpcd

;md

the

tanates CaZrTi,O, possibility

;md GdlTi,O,

to obtain

in these pro-

it?n-jn~pi~Ir~t~~~ ti[.31.X?]. As ;I third

information

on radiation

cffccts,

so-cz~llcd natural

anvlogucs :11-cused, i.c. naturally

curring

minerals

with

known

tempcraturc-time

tent ol’ 1J ;md/ctr Th over

long

cffccts

times

:I known

history)

imd :I corMin

ref.

[-ii)]).

The

;rhovcl for

in thcsc ccztmics.

thcsc m;lterials wcrc ohscrvcd

tl,l7]f.

large volume changes.

Volume

at satur;ltion

incrcascs

(ustmlly

of

up

to

:lt or slightly (c.g. ref.

quite in contrast to the very sm;ill volume changes

of WMC

glasses. The

r:tdi;ition

~~rn~)rphi~~tti~~n resulted creased

t’racturc

Other lion

for-

phases is cx-

;~hovc the ~ORC lcvcl causing mctamictization) [Xl).

many

The

mctdcfs (e.g. r&.

r:rthcr

swell.

SYNROC.

amttrphous

pccted h;~scd on the existing

W

wcrc

mct:unictiza-

damngc lcvcls with

of r;ldi~rtion-inclucecf

All

damngc

glasses

In addition.

tion w;is cthscrvcd at higher

and it is ctmncetcd with

same

waste

of thesu ccr;tmics. irgain including m;ltion

;I

con-

which have accumulated damage

(e.g.

its muntioncd

mc;tsurcd

oc-

age (and prcfcr;My

totlghrtcssos

qli~rltiti~s hchavior.

induced swclfing

in higher hut

like stored etc. wcrc

:irtd

fcach rates and inhardness.

dccrczxd

crier-gy. the rccrystalliza-

alstt mcasurcd

on ;i larger

number of such ceramics. The degree of understanding ahovc r;id&ion and R = (0.005 * 0.005) X IO- ” g. oorrcsponding

to a

the mcchrtnisms

plc, the contribution

to this

oatcs

length and 4 nm diamctcr.

accurate enough to diffcrcntiate

Some glasses swelled (< fl.h%

in

satisf;lctory

and some gl;lsscs contr:lctcd

dose, though ~111to :I very small cfcgrcc

dcnsify).

While

cxpfanation,

thcrc

is nff

the results

glasses indicated th;lt the porosity

crtmplctcly

ttn the Cm-doped

r~rn~iinin~

after glass

is mcnticmcd [Ml,

placcmcnt incrcascd

may bc dccisivc. Glasses with some r~~~~inin~

phous,

portrsily

(c.g. ‘2%) tcndcd to contrnct.

radiation

;tdvcrse radiation

cl’fccts wcrc found in thcsc horosili-

catc waste glasses doped with wcrc

small.

no

no significant

obscrvcd, and the fracture nologically positive

“‘Cm:

volume ch;mges

change in leach rate wits toughness

incrcascd, :I tcch-

stability

technically

As cxpfained in the introduction, studied

its possible

waste

ceramics XC also

m&rices.

Thcrc

arc some

~ontrjbuti(~~~s to this rcscarch field in the prcscnt ceedings (c.g. rcfs. [30,3l]f summarized with

“‘Cm

tion

cffccts

implantation

and other rcccnt results

in ref. [X].

Both

doping with

has been used cxtcnsivcly in

;f large

ceramics including

pro-

fc:rsiblc

number

SYNROC

and

to study radia~~ndid~It~

solutions

waste

sludges iX].

despite

its of

[27.34].

l&r

stttragc

have been dcvclopcd

Kiirlsruhc

ceramic matrix ;md bentonitc,

During

(INEL

an

(2 mixture product

heating ;ff IiWC,

the waste

and mullite particles.

at alu-

of corun-

KAB

tr~~nsur~n~~~n~ wastes

7X) wx and wxstc

the ceramic ritw AI,Si,O,,

Thcsc

“3”Pu to accclcr:ltc damage formation.

which

were

doped

Even ;tt :I

storage time of tlfJ to 10’ years, no adcffcct on the ceramic waste form w3s noted.

(simulatcdf vcrsc

There

w;is no variation

in the matrix,

stimts

or microstructure.

The

;IS e.g. for

Wwcvcr.

safe waste

hccn used to pro-

egrecing results.

;ft

:tnd taking advantage of the

of ceramics

l’ormcd Al,(I),

uncapsulatcs

-

tcstcd up to high damage lcvols [Xl:

used to incorpttrittc

with

dis-

cnhanccmcnts

I), and ion

(see section

has also successfully

duce damage, usually with

of

“‘Pu

ztrc

silicate

kaolinitc

material

individtml

which

similar

c.g. SYNROC

Kernforschungszcntrum dum,

within

UOI

shows

thcsc probicms propcrtics

minium

ovcrlup of displz~oemcnt

directly

hcing -

leach rates its dots,

positive

:lro

ceramics which do not bccomc amor-

;m extlmplc

avoiding

results

bctwccn amcrrphiza-

2 ph~n[~I~~~n[~n also observed

Icaching,

and successfully

damage cffcct.

cxperimcntal

cascades. A r~~~~~in~n~ prctbtcm is that of

high doses with

melting

In summary,

The

tion being caused by multiple cascades;, or occurring

on complex sili-

volume

d;imagc volume of e.g. the sh;lpc of ;1 cylinder of 15 nm

with increasing

of the

effects is well advanced. As an cx>#m-

formrmcc

is obvious: whcrcas

its lattice con-

reason for the good pcrin other w;1stc mzltriccs,

the actinides occur in homogcncous distribution, or enriched in some major structural cotnponcnts. the KAB 78 ceramic matrix experiences practically only ionization damage (f!- and -y-rays, and some cu-partic14 whereas all the displacement damage due ttt the heavy recoil atoms of the cu-decay is formed in the cncapsulatcd waste particles. This is a ~~)nvincing application of basic research on radiation effects (relative affects of S, and S,,) to a technological prohlcm.

[Ill J.P. Heuer, MSc thesis. University

of California

at Davis.

[ISI

Dept. Mech. Eng. (lYH7). A. Turos, Hj. Matzke and 0. Meyer. these Proceedings (6th Int. Conf. on Radiation Effects in Insulators, Weimar. Germany, 1YYlf Nucl. Instr. and Meth. Bh5 (I’)921 315. W.J. Weber, L.K. Mansur, F.W. C’linard. Jr. and D.M. Parkin. J. Nucl. Mater. IX4 (iYY11 I. 1Ij. Matzke and A. Turos, Nucl. Instr. and Meth. B46 (1090) I 17. and unpublished results. IIj. Matzke. J. Chcm. Sec.. Faraday Trans. Xh (IYYO)

4. Summary

[I61

1343. (3.11.Kinchin

The present paper summarizes the progress achieved in the past years in the field of radiation cffccts in nonmetallic nuclear materials, essentially the ceramic nuclear fuels UO, and UN as well as ceramics and glasses for s~~lidifi~at~~~n of high lcvcl radioactive waste. Roth the fundamental mechanisms and the technological implications of radiation effects are known and unterstood to a large dcgrce. For instance. low temperature experiments with UO, and UN have rccently filled the gaps in our knowledge on the behavior of uranium intcrstitials and have helped to understand the important phenomenon of fission-enhanced diffusion in thcsc fuels. Similarly, open questions on radiation cffccts in waste matrices were answered. Carefully planned basic investigations as separate cffcct studies have thus significantly helped in the technologically important complex field of radiation effects in nuclear materials.

[I71 [1X1

References

[II Hj. Matzke. Radiat. t:i

[41

IS1

[id

[71 Ml WI 1101

Eff. 64 (1982) 3. tlj. Matzke. Nucl. Instr. and Meth. B32 (10%) 453. P. Thevenard, A. Perez. J. Davenas and 1Ij. Matzke (eds.). Proc. 4th Int. Conf. on Radiation Effects in Insulators, Nucl. Instr. and Meth. B32 (19x8). J. Fuger and Hj. Matzke, in: Handbook ctf Physics and Chemistry of Actinides. vol. 6. chap. 14 (Else&r. Amsterdam. IYY1J. Hj. Matzke. Science of Advanced LMFBR Fuels. a Mon~~&~lph on Solid State Physics, Chemistry and Technology of Carbides, Nitrides and Carbol~itrides of Uranium and Plutonium (N(~rth-Holland* Amsterdam, 1YXh) p. 740. A.E. Ringwood. Safe Disposal of High Level Nuclear Waste: A New Strategy (Austral. Nat. Univ. Press, Canberra. 197X). W.J. Weher, J. Nucl. Mater. 98 (1981) 206. N. Nakae, A. Harada. T. Kirihara and S. Naau, J. Nucl. Mater. 71 (1978) 314. W.J. Weher and F.P. Roberts. Nucl. Technol. 60 (1YX3) 178. A. Manara, P.N. Gibson and M. Antonini. in: Scientific Basis for Nuclear Waste Management V, ed. W. Lutze (N(~rth-~~(~lland. 19X2) p. 34Y.

11’1

iI31 iI41

[191 [to] El1 ml

[231

and R.S. Pease, Rep. Progr. Phys. IX (IYSS) I. Hj. Matzke and J.L. Whitton. Can. J. Phys. 44 (IYbh) YYS. Hj. Matzke. Chalk River. Canada. report AECL-2585 (1066). R.A. Jackson, AD. Murray, J.11. I-larding and C.R.A. Catktw. Phiios. Msg. 53 (lYX6) 27. H.j. Matzke. 0. Meyer and A. Toros. Radiat. Eff. Def. Solids. in print. Hj. Matzke, Ii. Blank. M. Coquerelle, I.L.F. Ray. C. Ronchi and C.T. Walker. J. Nucl. Mater. 166 (19X0) 165. I.L.F. Ray, I-I. Thiele and Hj. Mattke. Proc. NATO ARW Fundamental Properties of Inert Gases in Solids. Bonas. France IYYO (Kluwer. 1YYl) in print. and unpuhlished results. A. Turos. S. Fritz and Hj. Matzke, Phys. Rev. B42 (IWO)

Y&-i .i. Morillo. T.N. Le and G. Jaskierowics,

Ann. Chimie: Science des Materiaux (IVY 1.14-6, in print. [‘51 Hj. Matzke ted.). Proc. 4th Int. Conf. on Radiation Effects in Insulators, Section IX Nucl. Instr. and Meth. B32 ( l9HR) 453-S 17. l2hl E. Vernaz. A. Loida. G. Malow. J.A.C. Marpies and Hj. Matzke. Proc. 3rd Europ. Comm. Conf. on Radioactive Waste Management and Disposal. Luxembourg, IYYI (CEC. Brussels) in print. results. WI Hj. Mutzke. unpublished in: Indentation Tech[2X1 Hj. Matzke and E.H. Toscano. niques, eds. Hj. Matzke and E.H. Toscano. Europ. Appl. Res. Reports - Nucl. Sci. Technol. 7 (1YYO) 1403. 1291 R. Dal Maschio, Hj. Matzke and G. Della Mea. ibid. p, 13X9, and unpublished results. [301 R.C. Ewing and L.M. Wang, and L.M. Wang and R.C. Ewing, these Proceedings (6th Int. Conf. on Radiation Effects in Insulators. Weimar, Germany, 1901) Nucl. Instr. and Meth. Bh5 (19Y2f 3lY. Ufl W.J. Weher, N.J. Hess and G.D. Maupin. these Proceedings (6th Int. Conf. on Radiation Effects in Insulators. Weimar. Germany, 1991) Nucl. Instr. and Meth. Bh5 (1992) 102. [32] W.J. Wrbrr and Hj. Matzke. Radiat. Eff. 9X (19X6) 93. [33] W.J. Weber, these Proceedings (6th Int. Conf. on Radiation Effects in Insulators, Weimar. Germany. IYYI) Nucl. Instr. and Meth. BhS (lYY2) XX. [341 A.G. Solomah and Hj. Matzke. Proc. MRS Conf. Scientific Basis for Nuclear Waste Management. Berlin. IYXX. Mat. Res. Sot. Symp. Proc. 127 f1YXY) 241. t.151 A. Loida and G. Schubert. Euratom Report. CEC. EUR11030 DE. Lu~~nlb~~~lrg (IYXH). E41

I. FUNDAMENTAL

ASPECTS