Composition and structure of fission product precipitates in irradiated oxide fuels: Correlation with phase studies in the Mo-Ru-Rh-Pd and BaO-UO2-ZrO2-MoO2 Systems

426

Journal of Nuclear Materials 130 (I 985) 426433 North-Holland, Amsterdam

COMPOSITION AND STRUCTURE CORRELATION

OF FISSION

WITH PHASE STUDIES

H. KLEYKAMP*,

PRODUCT

PRECIPITATES

IN THE Mo-Ru-Rh-Pd

J.O. PASCHOAL**,

IN IRRADIATED

OXIDE FUELS:

AND BaO-U02-ZrO*-Moo2

SYSTEMS

R. PEJSA+ and F. THDMMLER*

l$ernforschungszentrum Karlsruhe, * Institut fiir Material- und Festktirperforschung, Kerntechnische Betriebe / HeiBe Zellen, Postfach 3640, D-7500 Karlsruhe, Federal Republic of Germany

Composition and crystal structure of fission product precipitates in irradiated oxide fuels were studied by X-ray microanalysis and X-ray diffraction using instruments shielded for a-contamination and B-y-radiation. Pin cross-sections, fuel micro-samples from 300 urn hollow drillings and residues from the dissolution of irradiated material in HN03 were investigated. The metallic phases found are hcp c-Ru(Mo,Tc,Rh,Pd) solid solutions with broad variations in concentration of the components, bee @Mo(Tc,Ru) and fee a-Pd(Ru,Rh). The dominating ceramic precipitate is composed SrxCsy)(U,Pu,RE,Zr,Mo)03 which crystallizes in the cubic perovskite type. The MO frac:f0AB3-t-8 h se phases is related to the local oxygen potential of the fuels. The in-pile observed results agree well with phase studies in the quaternary Mo-Ru-Rh-Pd system where complete solid solubility exists between hcp Ru and the hexagonally stabilized Mo-Rh and Mo-Pd phases. Agreement is further attained with phase studies in the pseudoquaternary BaO-UOZ-ZrOpMoOz system which is characterized by a cubic perovskite phase Ba(U,Zr,Mo)03.

phases"

1. INTRODUCTION Uranium-plutonium fuel material

mixed oxides are used as

in fast breeder

number of fission

products

reactors.

is generated

burnup which change the chemical properties

radial temperature

gradients

result in oxygen-to-metal in actinide

and fission

oxygen potential O/Mratio,is

between

claddingcomponents

failure,

axial and

transport

behaviour influence

two dominant

by the

the fuel/

on the reactions products,

and in the case of cladding

formed within clusions" ruthenium,

fission

reveal that

precipitates

the fuel: The metallic

constitute

fuel, the temperature the burnup /1,2,3/.

the central

cipitates

reaction.

of molybdenum,

rhodium and palladium,

are

"white intechnetium,

and the "grey

Delegated

from Instituto

de Pesquisas

0022-3 115/85/$03.30 0 Elsevier Science Publishers (North-Holland Physics Publishing Division)

Energgticas

B.V.

in fig.1.

from the fuel region near pin with a very

which was reduced

in an unfailed

thecon-

Mo-Tc-Ru-Rh-Pd

pre-

FBR fuel pin with an

initial O/M ratio of 1.97 as a function relative

by the

Fig.2 illustrates

of the metallic

of the

fuel radius after 5% burnup. Molybdenum

oxygen potential

librium with the alloys, oxygen potential

in these alloys:

of the dioxide,

of the fuel,

its homogeneity

region.

in the metallic

precipitates

e Nucleares,

to the

(U,PU)O~+~,

The molybdenum decreases

Sao Paulo, Brazil

the

MOO*, in equi-

is comparable

**

of thesetwo

is demonstrated

void of a defected

sodium-fuel

of the fis-

in the pin and

The appearance

low oxygen potential

centration

gradients

is the least noble element

examinations product

on the composition

pheThe

and molybdenum.

the initial O/M ratio of the

The phases originate

the sodium coolant.

Post-irradiation

zirconium

types of precipitates

during opera-

the fuel, fission

sile material,

the oxides of barium,

of the phases varies consider-

and

gradients.

aparameterthatdetermines

and has a major

thatoccur

ably and depends

of the fuel,characterized

fissionproductchemical tion

during

in the fuel pins

product

plutonium,

The composition

(O/M) gradients

nomena which cause compositional

uranium,

mainly

A large

and mechanical

of the fuel. Furthermore,

contain

within

fraction by oxi-

427

H. kTiey&zmpet at. ,IFission Proust pye~~pitatesin irradiated oxide~els tials with high molybdenum very high oxygen with infinitely oxidized

was assumed

the oxide fuel matrix MO concentration

and at

and high burnups

small molybdenum

molybdenum

centration

fractions,

potentials

fractions.

The

to dissolve

in

/6/.Hence,the

ratio of the

in the alloys to the Moo2 con-

in the fuel matrix

the local oxygen potential based on the equilibrium

is an indicator

(la)

a limited Moo2 solubility

in (U,Pu)02

has been found /7/. Most of the oxidized FIGURE 1 Microstructure at the central void of a defected FBR fuel pin section (Siloe RSl-4)with precipitates

tion enters pitates

to the multi-component

replacing

and zirconium

frac-

oxide preci-

the four valency

uranium,plutonium

is

/6/:

WI alloy +[O 2 1fuel = Wo021fuel However,

of

of the fuel which

cations of

in the lattice.

This results intheequilibrium/8/:

[MO]alloy I

;

t

I

/

DFRCS-OBZO-2

-*

+['$fuel

= 'Moo210xideprecipitate

The local oxygen potential,

0

fuels at the end-of-life

state can be calculated

by use of the mass action AED

Obf

AGO,, of irradiated

law yielding

/6,8/:

= fAG"+RTln(xMo0

with mole fractions

lY /xMo'YMo) (2) 2 MO02 xi and activity coefficients

Yi' 2. PHASE STUDIES

IN THE Mo-Ru-Rh-Pd

BaO-U02-Zr02-Moo2 10

AND

SYSTEMS

The composition and the structureo.~t~lep~~ases

i 0,2

i

8

0,s

0,4

0,5 r/To

in detail onlyon

!

1

0,s

observed ~nirradiatedmaterial

0‘7

I,0

_

can be interpreted

the basis of phase studies of these

systems in laboratoryscale.Theyareconfinedtothe twoquaternary Mo-Ru-Rh-Pd/g/andBaO-U02-Zr02-

FIGURE 2 Concentration ofthemetallicMo-Tc-Ru-Rh-Pd precipitates inaFBRpin(DFR455-OB20)asafunctionof the relative fuel radius;initial O/Mratio1.97, burnup 5%. dation of this fission due to an increase

product

in unfailed

of the oxygen

pins

potential ofthe

Mo02/10/

systems at1700°C,disrepardingtechneti'um

and the oxideofplutoniucwhich of the respective

in-pile

phases.

Themeta11icsystemat1700°Cischaracterizedby theexistenceoftwoextendedmono-phasestatespaces.The hcp~ spacepermeatestheentireconcentra-

fuel with burnup.This is a resultofthefission

tion tetrabedronranging

process becauseoxygen

hexagonallystabilizedinte~ediate

bythegenerated

cannotcompletelybebonded

fission products

alloys havebeenobservedat

/2-6/.Two-phase

verylowoxygenpoten-

aremajorcomponents

theMo-RhandMo-Pdbinary

fromthe

pure hcp Ruto the

boundary

phases inboth systems.

The

fee c1 space is cut off by the Pd rich liquid.

428

H. Kleykamp et al. / Fission product precipitates in irradiated oxide fuels

The bee B space is limited apex. The occurence

of the u phase up to about

19OO'C and of the palladium

intersection

three-phase

each with the respective tetrahedron.

section

fig.4. The solid solution

pseudoternary

is illustrated

crystallizes

in

in the

surfaces

There is no

state space in the quaternary

at 17OO'C /9/. The isothermal

.

Rh-Pd system is illustrated

system

pseudoternary

Ru-Rho 5Pd0 5 section of the quaternary

.

Ba(U,Zr)03 /lo/. The isothermal

in

B+ate and eta+L, with two areas of

of the concentration four-phase

and a limited BaMo03 solubility

BaU03-BaZr03-6aMo03

rich melt above

1555'C is reason for twoprismoidal state spaces,

solubility

to the molybdenum

Mo-

Mo-Ruattice parameter

in fig.3. The hcp E

BaZrOs

BaUOs

FIGURE 4 Isothermal pseudoternary BaU03-BaZr03-BaMo03 section of the pseudoquaternary BaO-UOZ-Zr02Moo2 system at 17OOOC. cubic perovskite parameters a =419

type structure

ranging

from a=439

and with further

pm for BaZr03,

tion of the lattice

parameter

tion. The solubility

with lattice pm for BaU03 to

by BaMo03 solu-

limit of BaMo03

Zro 503 is about 5 mol % BaMo03. fractions

reduc-

in the pseudoternary

in BaUO 5

Higher BaMob3

BaU03-BaZr03-

FIGURE 3 5Pd 5 secIsothermal pseudoternary Mo-Ru-Rh em at tion of the quaternary Mo-Ru-Rh-P !* sys ?* 17000C; the lattice parameter a of the hexagonal solid solution range is included.

BaMo03 section

dueto

decomposition

of pure BaMoC3 at 138O'C

phase appears

/lo/.

This reaction

behaviour

sections

like in the corresponding

in a broad concentration

fitted lattice parameters

range. The

a within

E region are given as iso-lattice from a =270.6 pmfor

toa=

for the hcp Mo0.5Rh0.25Pd0.25

proportionationoccurs

in the condensed

doternary

in graphical

section

with complete

cannot be ex-

form of the pseu-

pure ruthenium

BaO-U02-Zr02-Moo2

at 17OO'C is characterized

state

(fig.4).

solid 3. X-RAY MICROANALYSIS

The pseudoquaternary

At

Mo6'dis-

cur-

solution.

Ba(U,Zr,Mo)03

3 Mo4'+Moot2

actlypresented

the mono-phase parameter

ves ranging 277pm

ternary

result in two perovskites.

fairly high fractions,

by a quinary BaUO3-BaZr03

system oxide solid

STUDIES

AND X-RAY DIFFRACTION

ON IRRADIATED

The objective

MATERIAL

of this paper is the correla-

tion of the phase studies

in the quaternary

Mo-

429

H. Kleykamp et al. / Fission product precipitates in irradiated oxide fuels

Ru-Rh-Pd

and BaO-U02-Zr02-Mo02systemswithcom-

position

and structure

precipitates

of the fission

observed

in irradiatedoxide

The X-ray microanalysis pin cross-sections solution

process

of irradiated

in araldite.

and polished, trasonic

shielded

from thedisstand pillar

fuels in nitric

the material

The section was

was

ground

and after decontamination

cleaning

sputtered

fuels.

was performedonfuel

and on residues

acid. Prior to the analysis embedded

drilling machine

product

by ul-

locking mechanism

with Freon TF the surface was

with a 40 nm thick gold layer. The yinstrument

wavelength

allows the quantitative

dispersive

analysis

to 2OCi (T=0.8MeVy).

on specimens

Linear crystal

up

spectro-

meters are used for the analysis ofallelements with Z>6

(carbon).

A remotely constructed

controlled

extraction

in the Hot Cells of KfK for obtain-

ing small samples

from embedded

fuel pin cross-sections The section

can be adjusted

sliding

allow identical

micrometers.

stage. The exact

microscopically

positioning

200 pm

a few

Details are given in fig.5. Hollow

for the micro-drilling inner diameters

fragments

process.

of the smallest

mm,resp.

body was embedded

in araldite

were used

1

Rapsodie

I-BM06-5

The outer and drillswerel.O

The drilled-out

forced out of the hollow-drill,

A polished

and

of the selectedsec-

machine within

drills studded with diamond

according

by the

An adjustable

carrigeandalockingmechanism

tion under the drilling

mmand0.3

scale.

FIGURE 5 View of the micro-drilling device.For taking out samples downto 300 pm diameter from irradiated fuel pin sections the adjustable slidingcarriage is reproducibly positioned under the periscope and the drilling machine, resp.

is fixed by use of a chuck in combi-

cross wire of the periscope. revolving

and polished

in the milligramme

nation with an x-y-z specimen position

device was

material

was

the cylindrical and was prepared

to the usual metallographictechniques. briquette

is presented

in fig.6 to-

gether with the results of the X-ray microanalysis in the enlarged The structural of a v-shielded were mounted stage movable

detail of the figure.

analysis

was conducted

by use

X-ray diffractometer.Thesamples

on a remotely

controlled

in x-y directions

specimen

of the surface.

FIGURE 6 Microstructure ofa drilled-out micro-sample froma FBRfuel pin section (Rapsodie I-BM06-5)composedof Ba,Sr)O fuel articles,Mo-Tc-Ru-Rh-Pdinclusions and PBa,Sr,Cs U,Pu,Zr,Mo)O3; initial O/4 ratio 1.96, burnup Ib%.

430

H. Kleykamp et al. /Fission product precipitates in irradiated oxide fuels

A curved

graphite monochromatorwith

tivity was used to suppress

the unwanted

diation emitted

from the radioactive

The X-radiation

was registrated

NaJ(T1)

scintillation

the diffractometer

high reflecy-ra-

material.

by a shielded

counter.

The details

are described

of

in /ll/.

Ru-Rho 5Pd0 5 system

.

are dependent

tial and the thermal

potential

be estimated

OF IRRADIATED

done at KfK on irra-

diated FBR, LWR and HTR fuels were evaluated for quantitative lic and ceramic

results concerning fission

The compositions

product

Rh-Pd phases of irradiated cally presented pseudoternary system

precipitates.

of the metallic

from the initial O/M ratio and the

section

of the

bee MO - hcp (RutTc)- fee (RhtPd)

in fig.7. The phases

formed during

irra-

e

defected

X

defective

P

defective

.

1.965,9

0

1.99.12

burnup

ported to the fuel surfacenear

o

1.99;

6

1.97;

13

P

1.965;

5

.

1.97i

5

.

1.96;

10

51.S6)and

highervapour

system.Ontheotherhand,

indefective

LMFERpins

a second bee firichinmo-

lybdenum.Thesetwo-phaseinclusions

havebeen

highlyrated (40kW/m)LWR

foundalsoin

/IV

system.Furthermore,AuCu3structuretype (Rh,Pd)3tx phases are formedin

(U,Pu)

pressures /I4/.

FBR and LWR pin cross-sections

parts therefrom

were dissolved

ray microanalysis

(i) fee oxide fuel par-

(ii) hcp Mo-Tc-Ru-Rh-Pd

fuels and

with those found in irradiated

mainly on the MO - [0.7(Ru+

section,

and most of the pre-

are ranged within

the hexagonal

phase field of the underlying

mono-

pseudoternary

Mo-

sections oxides

oxide hydrates

from the nitric acid

/15/. The metallic

were isolated FIGURE 7 Composition of the Mo-(Ru-Tc)-(Rh-Pd) precipitates in the inner fuel regions (rs 0.5 ro) of irradiated FBR pins with different O/M ratios and burnups projected onto the Mo-Ru-Rho 5Pd0 5 . . section at 17000C.

alloys which

(iii) fission product

which were reprecipitated solution

by X-

and by X-ray diffraction.Three

phases were observed:

are identical

or

in concentrated

nitric acid. The residues were analysed

cipitates

and in

defective LMFBRmixed

oxide fuels atverylowoxygenpartial

Tc)+0.3(Rh+Pd)]

in

uteregions,resp.,inthequaternaryMo-Ru-Rh-Pd

in %

are located

pres-

etaregion

ando-phase,resp.,isobservedwhichis

ticles;

diation

is trans-

region duringthe

sure.Thesephasescorrespondtothe

Several

l

forming a se-

rich phase which

HTR-triso fuels /I3/ and correspond to the P+f:and

(Rh+Pdl ratio;max.

two-phase

fraction.

at low oxygen potentials (end-of-life O/H ratios

Rho.5Pdo.5 O/M-

become

thequaternaryl~o-Ru-Rh-Pd

Mo-Tc-Ru-

FBR pins are graphi-

in an isothermal

O/M ratio and the

irradiation process duetothe

the metal-

of the fuels.

of the fuel, resp. (which can

cond, fee palladium

All X-ray microanalyses

conditions

lower is the molybdenum

The precipitates

MATERIAL

at 1700'C.The

on the oxygen poten-

The higher the end-of-life oxygen

burnup),the 4. RESULTS ON THE PRECIPITATES

investigated

.

compositions

type (ii) phases

or were drilled out from cross-

of irradiated

(experiments

LWR fuel (KWO), FBRmixed

DFR 455 and Rapsodie

I) and

FBR mixed carbides

(DFR 330). Compositions

and

lattice parameters

of the phases are given in

table 1. Details are explained positions

of the hexagonal

again presented pseudoternary

in /ll/.The

precipitates

in an isothermal

bee MO -hcp

com-

are

section of the

(Ru+Tc)- fee (Rh+Pd)

431

H. Kle~~~p et al. / Fission ~rod~&tprecipitates in irradiatedoxide fuels

TABLE 1 Composition and lattice parameters of the metallic hexagonal Mo-Tc-Ru-Rh-Pd precipitates in irradiated nuclear fuels. fuel

experiment

DFR 455-8A5-3 FBR oxide DFR 455-lA61-6,'7 FBR oxide Rapsodie I-BM06-5 FBR oxide FBR carbide DFR 330/l-02 KWO 7-365.67-4 LWR-U02 KWO 7-365.67-7 LWR-U02

lattice parameters (pm)

composition (wt.%)

sample

MO

residue residue drill residue residue residue

33-43 39-42 37 25 24

Tc

Ru

Rh

12-16 30-39 7-10 lo-12 27-30 7-10 21 35 4 mainly ruthenium 8 52 : 8 44

Pd

a

5-10 6-15 3

276.1 275.6 274.6 273 275.2 275.2

1"6

C

443.1 442.0 441.5 430 441.1 441.5

system whichareprojectedon theMo-Ru-Rho 5PdU 5

rences between the in-pile observations on pha-

section at 1700°C, see fig.8. The lattice para-

ses with variable Rh/Pd-ratio and the labora-

meters of the hexagonal phases observed in ir-

tory results on phases at constant Rh/Pd=I.

f

.

DFR

WA

155 - 6 AS3

KWO

There is furthermore agreement with observa-

(Rh+Pd

tions of Bramman et al. /16/ who isolated me-

LSS-lA61-6/7

Rspsadir .

.

I - BM06-5

chanically a metallic ingot from irradiated (U,

7-m

1700*c

Pu)02 and identified the hexagonal structure of the Moo~44Tco~16Ruo~33Rho~07phase by X-raydiffraction giving a =274 pm and c =445 pm. The dominating ceramic precipitateswithin the irradiated oxide fuels are composed of the oxides of uranium, plutonium and the fission products barium, strontium, cesium, zirconium, molybdenum and the rare earths, RE. Numerous studies by X-ray microanalysis revealed thecomposition (BaI,x_ySrxCsy )(U,Pu,RE,Zr,Mo)03.The rare earth fractions can be identified only at

60

10

at.%

Ru

80

(Ru*TcI

-

FIGURE 8 The hexagonal Mo-(Ru-Tc)-(Rh-Pd)precipitatesof irradiated LWR fuel and FBR mixed oxide and mixed carbide fuels in the residues after the dissolution process in nitric acid. The compositionsare projected onto the Mo-Ru-RhO,5PdO 5 section at 17000C; the lattice parameters a and c are given in table 1. radiated oxide fuels (table 1) agree well with

very high burnups. The molybdenum fraction depends on the end-of-life O/M ratio and the oxygen potential of the fuel, resp., and ranges from concentrations smaller than the detection limit (0.02%) to few weight percents molybdenum at high oxygen potentials. The compositions can be presented graphically in an isothermal section of the pseudoternary A(U,Pu,RE)03-AZr03AMoO system, A=Bal_x_ySrxCsy, x,y<< 1, which

the results of the laboratory studies on the

is projected onto the BaU03-BaZr03-BaMo03sec-

pseudoternary Mo-Ru-RhO.5PdO.5section of the

tion at 1700°C, see fig.9.The BaMo03 fractionin

quaternary system. It should be noted that a re-

the ceramic phases increases with increasing

placement of rhodium by palladium results in an

end-of-life O/M ratio and oxygen potential of

increase of the lattice parameters of the hexa-

the fuel, resp., according to the equilibriumin

gonal phases /9/, explaining the small diffe-

equation (Ib).The compositions of the ceramic

432

fuels

H. Kleykamp et al. / Fission product precipitates in irradiated oxide

was selected BoMoO, (

diffraction

lBo,Sr,CslMoO, I VFBR,

defect

o Ff3R,(O/Mlo

=1.96-

. FBR,(O/Ml,

=1.98-2.00

A HTR-triso,(OlUl,

1.97 = 2.00

for X-ray microanalysis.

The X-ray

results of the drilled-out

(fig.6) revealed structure.

a cubic perovskite

The lattice parameter

region

oxide type

was found to

be a = 433 pm for the phase with composition

iBag g(SrsCs)O,I[OJ,$uo $EO 05)Zr025103. This'result isotypic

is'in excellent

phases BaPuO,,

agreement

with the

a = 437.3 pm /17/, and

J

with BaU0.75Zr0,2503, a = 435.5 pm /lO/,see fig.10.

5. SUMMARY

1 IBa,Sr.CsllU.Pu.RE)O~)

BaUO,

Molybdenum, and palladium alloys

FIGURE 9 Composition of the (Ba,Sr,Cs)([U,Pu,REl-Zr-MO)03 precipitates of irradiated HTR and FBR fuelswith different O/M ratios projected onto the BaU03BaZrO3-BaMo03 section at 17OOOC. precipitates

are located within

phase field of the pseudoternary

the cubic mono-

fuel region near the central after 7% local burnup

in irradiated

rhodium

or two-phase

LWR, HTR and FBR oxide

fuels. The compositions

are primarily

on the oxygen

of the fuel at the end

potential

of irradiation

and on the temperature

in the fuel pins. The mono-phase cipitates -

of ceramic

ruthenium,

become two-phase

dependent

gradients

hexagonal

pre-

in the limitingcases:

BaU03-BaZr03-

BaMo03 section. An aggregation

technetium,

form mono-phase

precipitates

very low oxygen potentials num contents,

in the

of a second

void of a FBR pin

above and below

(initial O/M ratio 1.96) -

very high oxygen num contents,

result in the formation

resp.,

phase,

and high molybde-

B or o, at temperatures

1900°C, resp.;

potentials

and low molybde-

resp., and high palladium

tents result in the formation

con-

of the c1 phase

as the second phase. Part of the molybdenum oxidized

during

fraction

the irradiation

failed pins and becomes 410

t

LOO

A Ba(",.,Pu,.,RE,,,)Zr,.,,O, 1

skite type ceramic

20

component

I

situated

BaUO, -

LO BaZrOs

60

80

in mol %

100 -

FIGURE 10 Lattice parameters of the perovskite typeoxides BaPuO3 and the BaUI_xZrx03.solid solution as well as of the ceramic precipitate in the irradiated FBR fuel illustrated in fig.6.

component

of the perov-

region of the multi-

system. The mechanism

of (Ba,Sr)O precipitates

of the formation

observed

fuels is not yet completely

containing

process of un-

phases. The compositions are

in a mono-phase

composition

of the alloys is

in irradiated

understood.

A de-

of the liquid multi-component barium oxide is possible

period of the pins.

during the cooling

H. Kleykmnp et al. /Fission

On the whole

it can be stated

ment of composition, meters

that theagree-

structure

and latticepara-

of the in-pile observed

phases with the

results of the phase studies and BaO-U02-Zr02-Moo2

systems

view of the difficulties preparation

associated

and the analysis

in

with the

of irradiated

re-

actor fuel.

sistance

gratefully

of Mr. Wacker

the micro-drilling X-ray diffraction schalg

I. Johnson, C.E. Johnson, C.E. Crouthamel, C.A. Seils, J. Nucl. Mater., 48 (1973) 21

171

G. Giacchetti. C. Sari, Nucl. Technol. (1976) 62 .

/8/

H. Kleykamp,

/9/

J.O.A. Paschoal H. Kleykamp, Z. Metallk. 74 ;1983) 652

J. Nucl. Mater.

31

66 (1977) 292 F. Thtimmler,

Kernforschungszentrum /IO/ J.O.A. Paschoal Karlsruhe, repo;t KfK-3473 (1983)

ACKNOWLEDGEMENTS The authors

/6/

on the Mo-Ru-Rh-Pd is excellent

433

product precipitates in irradiated oxide fuels

acknowledge

the as-

for the construction

device,

Mr. Kohnert

measurements

of

for the

and Mr. Gott-

for the X-ray microanalysis.

/lI/ H. Kleykamp, (1984) 56

R. Pejsa, J. Nucl. Mater.

/I21 H. Kleykamp,

J. Nucl. Mater.,

124

84 (1979) 109

/I3/ R. Forthmann, H. GrUbmeier, H. Kleykamp, A. Naoumidis, Thermodyn. Nucl. Mater., Vienna, 1974, proc. symp. (1975), Vol.2 p. 147

REFERENCES

/I/

M.H. Rand, T.L. Markin, Thermodyn. Nucl. Mater., Vienna, 1967, proc. symp. (1968), p. 637

/2/

H. Holleck, H. Kleykamp, Kernforschungszentrum Karlsruhe, report KfK-1181 (1970)

/3/

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