Table Of ContentXA9847839-J7-V
IAEA-TECDOC-1036
Advances in
fuel pellet technology
for improved performance
at high burnup
Proceedin agT fose chnical Committee meeting
held in Tokyo, Japan, 28 October- 1 November 1996
INTERNATIONAL ATOMIC ENERGY AGENCY
The originating Section of this publication in the IAEA was:
Nuclear Fuel Cycle and Materials Section
International Atomic Energy Agency
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00P1 .xOoB.
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ADVANCN EFSIU EL PELLET TECHNOLROOGFY
IMPROVED PERFORMANT CHAEIG H BURNUP
IAEA, VIENNA, 1998
IAEA-TECDOC-1036
ISSN 1011^289
©IAEA, 1998
Printed by the IAEA in Austria
August 1998
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FOREWORD
e nhuctl enn amIri a fsnieyald o ,thers, improved perfon rimmaa psnoicrte ant econmomiaic
Improved fuel fabre imncoaet aif sonroians is eiphnetgr formanf nocue clear fn uriee lactor plants
These focal points, fuel fabrication and performance, were widely covered by the Technical
Committee Meeting on Advances in Fuel Pellet Technology for Improved Performance at High
Burnup
In connection with improving performanca ere, liable estimaf fotue el behaviour constituteas
basic demr aosnfad fety based calculatior ondfse, sign p ruofrfupe dol nsaeass sessments Close
observatiof onf ut aehl igh burnus ipn ecessa ortyi mproe vhstea fety cod dnecasa pabilitifeos
predicting fuel behavioun bir oth normd anaabl normal conditions
The IAEs arAhe cently compleo twCedto -ordinated Research Programmes (CehRTP nso)
Development fo Computer Models rof Fuel Element Behaviourn i Water Reactors,n o dna Fuel
Modelt lEianxg tended Burnup Through these CR tbPie scame evidenta no tohe besatdtt aa tihwnere
data on fuel behaviour at high burnup Data related to thermal behaviour, fission gas release and
po ectlllae dt mechanical interaction were oe dbThptneartcieanhs eentdn iacteadl Committee
Meetin nAog dvancen Fis uel Pellet Technolor goIfym proved Performanct aHe igh Burnup which
was recom ehImnttee nyrdnbeadt ional Working Gn roFouup el Performd anTnaecceh nology
(IWGFPT)
The 34 papers from 10 countries were grouped into 6 sessions The first two sessions covered
fuel fabricatif oX bd oOffnanou OudUateeMdhl l it idSvn4 eeca ssdo snvioaen e r3tehsh tde rmal
behaviour of both types of fuel. The remaining two sessions dealt with fission gas release and the
mechanical aspecf pot elleo ctt lad interaction
The IAEA wishes to thank the Japan Atomic Research Institute and the Nuclear Power
Engineering Corporationf o Japanr of hostinge ht meetie hnt llapg dna articipantsr of their
contributiono ttsh is publica ethiIoTAnE A officer respon ehostir brgolafen iz eahmtti eofoen ting
MCw ePhaDhas tniv tfoiosmf ioN onu clee aFhr utPe dol wnCaJ e ey srhM Pcatlmee fneout
division compiledd nac ompleted this publication
2
EDITORIAL NOTE
In preparing this publicatior nof press, e hstIt AafofEf A have me ahptd paue ges froemht
original manuscripts as submitted by the authors. The views expressed do not necessarily reflect
those hte fo IAEAe ht, governmene thts fo nominating Member Statee hts ro nominating
organizations.
Througe htheotxut t namf oMes ember S etarreatetas is nathede y were swae twhheetxn t
compiled.
The use of particular designations of countries or territories does not imply any judgement by
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institutions or of the delimitation of their boundaries.
The menf toinoaf n mospees cific compr aonpireos duct tso inn(dwisc hraeaotthede r
registered) dt ooiy mneinnspa tley ntio oitnn fringe proprietary rigr sohe hntcbsoo , utnlids trusead
n aendorsementr o recommendatione ht pno art of eht IAEA.
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reproduce, translate or use material from sources already protected by copyrights.
CONTENTS
Summary.....................................................................................................................................1
FUEL FABRICATION — UO FUEL, UO AND ADDITIVES (Session 1)
2 2
Characteristicf osf uel pellet with addd Sniat iliA.v. f.eo. .......................................................9..
T. Matsuda. Y, Yuasa. ,S Kobayashi. M, Toba
Niobia-do OpfueUedl manufacturing experient caBe ritish Nuclear Fuels Ltd...................9..1..
2
G. Marsh, G.A. Wood, C.P. Perkins
New U0 fuel studies................................................................................................................. 27
2
. DhePha. uLCdetm ,aign .aLCna ,il. lMAoto ,c .eEGllmini ,net
On the sintering kinetics in UO ................................................................................................. 41
2
. AMaryakjsof
Grain size distribution ni seeded large grain size U0 ...............................................................94
2
G.A. Wood, C.P. Perkins
FUEL FABRICATION — GADOLINIA AND MOX FUEL (Session 2)
A stude hytU fo O/GdjC^ composite fuel................................................................................3.6
. DBalestrieri
Effect of particle size and oxygen potential on UO /Gd O pellet sintering.............................. 73
2 2 3
T. Nishida, R. Yuda
Development of duplex type MOX-Gd O fuel for water reactors............................................ 85
2 3
M. Koto, S. Kohno, K. Kamimura
DevelopmenX tOM mfo anufacturing technologyn i BNFL.....................................................39
P.G. Buchan, D.J. Powe. lJEl, dwards
Develo XpfmOueMel n pntise llet fabrication technology: Indian experience....................3..0..1.
H.S. Kama. MStha ,jumdar, D.S.C. Purusthotham
FUEL THERMAL BEHAVIOUR— T HERMAL CONDUCTIVITY
DEGRADATION OF UO FUEL (Session 3)
2
Thermal conductivity determinationr oifsr radiated fuel ..........................................................115
T.L. Shaw, J.C. Carrol, R.A. Gomme
Thermal diffusivity of high burnup UO pellet......................................................................... 127
2
/. Nakamura, M. Uchida, H. Uetsuka, T.Furuta
Thermal diffusivity measurements of irradiated UO pellets.................................................... 139
2
M. H. iAMrami. a,YWyaa ,kash. NiTmoam ,. aHHtaa . y,KMasihtai ,mura
e ehTffecf oitrs radiae ththti oenornm al conductivitf hoy igh bum OfuuUpe l..................9.4.1..
2
K. Bakker, R.J.M. Konings
Microsrructure and fracture toughness characterization of irradiated PWR
fuels in the burnup range of 40-67 GWd/tM...................................................................161
J. Sp. MiCnoo ,quere. lBDlea ,ron
Examinatiof nos ub-grain formation nhi igh burn uOfuUpe l usine hEgt BSP method .......7.7.1.
2
. B5engtsson
An attempt to simulate the porosity buildup in the rim at high bumup.................................... 185
D. Baro. BHn, ermitte, J.P. Piron
Development of a thermal conductivity correlation for the pellet rim region and its
appli ecahantt aioolytn f sboies haviof huoir gh bumup fuel...........................................205
Byung-Ho Lee, Yang-Hyun Koo, Dong-Seong Sohn
FUEL THERMAL BEHAVIOU— RT HERMAL CONDUCTIVITY
DEGRADATIOF GONA DOLINIA XDFOUOMEP DLEND A( Sessio)n4
Thermal propertiesd nai rradiation behavioud Gr ffo uel..........................................................219
Y. Kosaka, S. Dot, K. Yamate
Thermal conductivity measurementsn o (U,M)O pellets ......................................................233
2+X
M. Amaya, M. Hirai
Chemical formf o fission productsn i high burnup fuels...........................................................245
R.P.C. Schram, R.J.M. Konings
FISSIOS NARG ELEASE (Session)5
Influencing and optimizing fuel pellet parameters for achievement of extended bumup.........257
A. V. Medvedev, J.K. Bibilashvili, O. V. Milovanov, S.M. Bogatyr
The roe hplt efoe ln lof emiistr sio sanrge leaset ae xtended burnup ........................................267
. RManzel. M,C oquerelle
Irradiatf iUooOn e ThAt N fnuOeilXs device ......................................................................277
2+X
. DhePha. uCLdat . D,iGlleo. lEte G,tmtei. ,nMAeot ,cellin
BNFL assessme fmnot ethof daost taining high bX ufurOneMul.p. ........................................289
C. Brow. HW n.eK, sket. DhPI, almer
Fission gas release and pellet microstrucrure change of high burnup BWR fuel...................... 297
N. Itagaki, K. Ohira, K. Tsuda, G. Fischer, T. Ota
e Sthettac fthoe nology review..................................................................................................311
/. Spino
PELLET-CLAD MECHANICAL INTERACTION (Session)6
Examinatif oWon ER-440 fuel microstrucd tcunorame posia tbi onuinr nup
interf v4oa2 l-63 MWd/kgU............................................................................................325
A. Smirnov, A. Petuhov, B. Kanashov
Post irradiation examination experience of hollow pellets for PWRs.......................................339
H. Uchida, S. Uehara, A. Oe, S. Matsumoto
Structural change ehWts ni ER-1000 oxide fuel after irradiation ...........................................353
V.N. Golovanov, V.I. Kuzmin, A. V. Smirnov
Chemical stabilitd pyna hysical propertief soc aesium uranates...............................................363
J.P. Berton, D. Baron, M. Coquerelle
The formation process of pellet-cladding bonding layer in high bumup BWR fuels ..............377
K. Nogita, K. Une
Development of a microindentation technique to determine the fuel
mechanical behaviour at high bumup..............................................................................391
. DBaron,. S Ledercq,. J Spino .,S Taheri
In-reactor performance of prototype SBR MOX fuel...............................................................399
C. Brown. JM, ulle. DnPI, almer
High temperature mechanical tests performed on doped fuels .................................................409
C. Dugay, A. Mocellin, Ph. Dehaudt, M. Sladkoff
Lif sPot articipants ....................................................................................................................421
SUMMARY
1. INTRODUCTION
e Thte fcoh nmTichiaae l Committee Meetin nAog dvancn eFis uel Pellet Technology
for Improved Performance at High Burnup was to present an overview and a synthesis on
advances made in pellet design and technology during recent years.
Sixty-six participants f 7rco1omu nd trniinaetse rnational organizations attenedhetd
presentd aptniaonanes l d4 ips3acpu esesrhsio Tpnrs e.sented were grouped in6 stoe ssions
covering fuel fabricad toniouant come from high burnf u obOfpou Uethl (additivr eons ot)
2
and MOX. w de eSrreneaev le2saeh sdttli eonooadpt n Of1msa Ube rfnoict atd iMnoanO X.
2
Sessions 3 and 4 covered the thermal behaviour of both types of fuel. The remaining two
sessions dealt with fission gas release and the mechanical aspect of pellet to clad interaction.
The technical discussions were conducted in four panels under the headings Fuel Fabrication,
Fuel Thermal Behaviour, Fiss siRaoGne lead Psnaee llet-Clad Mechanical Interaction.
It is too early to reach conclusions about advanced fuels compared to conventional UO
2
0 yf3eu aeolr tsa w h 0 wie shsr2haieit tcohtsfhh rou yl ting experie emnhcTaei .n findinfogs
this meete itrnhn aa sgaig p t rfieotea t wndueamnta bf oerer lato ehtdi gh burnup additional
data about characteristics and behaviour are still missing. Research and development is still
required, especially irradiation teso tcts heck fuel performanct ahe igh e bcbua orrtrn eiuerapd
out.
The technical discussions are summarized here.
2. FUEL FABRICATION
2.1. UO
2
As the fission gas release rate increases with the burnup, the structural influence on this
topic wille b studied. Some tests fo different grain size fabricatione ra reported.
It is necessary to obtain more knowledge on the structural evolution related to the
additives which should hav aeh armful eedhftfi fenfocue t fhsitis ofsoni on gases.
The creep rats ieim epohI otnCb rtlePoty hanr o napsfvtia tirioa tumurbe, e tcherTre. ep
rate coue ilbmd provy rebed duce ignhrgta in sizA es.m all graine oh ust ittzsaei dea adrneaa
large grain size insidee b hcetos uet lbmd ethod. Howeve gehrrta, in size only affe echcrttes ep
rate whe mehnt echae nghitrs amsii n boundary diffusion, i.e esht.t ress lis ow. Consequently,
it si clear thae httm ain future research workn o fuel fabrication woulde b relatee hdtg ot rain
size.
2.2. UO +Additives
2
s i tIdifficuy alsd ott efinitively which additivese ra availabled nau seful. Niobia doped
fuel experience exhibits a reliability to promote grain. Other additives are promising (Al, Si).
Manufacturing reliability dna quality control coulde b improvedy b additives.
Additional information about irradiation behaviour of doped UO fuels is necessary to come
toa conclusion aboue htbt enefi ftoa dditions sa(d oping n)of issios nagr eleasd enPa CI.
2.3. Burnable absorber
Gadolinia doped fuel is already used commercially. No new fuel, as composite fuel or
duplex fus erile ,quired tod, opaSoyw. er generation f erphootmi soned fuel inwiteinat ead
approach consis etahitnb ngsi encf ode egrada etthihto feonr mal conductivd irnteya tentiofon
fission gas.
In this case, composr iotde uplex fuels sn hiaon uneblodv ative solution. Duplex fuel
f ionct oeeuro bealtdvs toid gadolinia contame mX ihfnuaOtaen ltnu.iMofian c tfuore
2
Irradiatiof odn efect rods will induca ed egrade ahcttoi ofmonp osr iotde uplex fuel
because there is a dissolution of gadolinia by water. Some studies on a new material like (Zr,
Gd)0 would lead to avoiding this phenomenon of dissolution.
XOM2.4 .
Pu homogeneity is a current aspect of MOX manufacturing. Homogeneity means fine
dispersion of Pu, and reprocessing aspects must also be taken into account with regard to this
local Pu content. Homogeneity is expected to be better for fission gas release which would be
an important specific behaviour of MOX fuel. Regardless of the fission gas release,
homogeneity could improve.
Todaye h,Mt IMAS process peller toC OCA-process pellet providea similar fissiosnag
release rate at 45 GWd/t. Linear power at the 3rd or 4th cycle seems to be the major parameter
rega erdhfs iitnasrsgge iloen ase rate. Experimental irradiation with rods, including
thermocouples, could be performed with an accelerated evolution of parameters.
Advanced MOX fuels are required in a second stage while the main result will be
essential for advanced UO fuels.
2
3. FUEL THERMAL BEHAVIOUR
3.1. Thermal conductivity - reliability of data available
Reasonable agreement exists betw edeheattn a obtained from in-pile fuel temperature
measurements at Halden and that obtained from out-of-pile post irradiation measurements of
Thermal Diffusivir dnyaS pecific Heat- which indicatee hsrt eliabilie htta yfov ailable data.
However, more data are required in the following areas:
(a) Effects of stoichiometry on specific heat
(b) Measurement of thermal conductivity of the RIM zone
(c) Measurement of thermal conductivity of Go^Oj fuels
(d) Measurement of thermal conductivity under conditions relevant to transients and RIA
(e) Examination of effects of additives under RIA conditions.
2
Attempts should be made to collect the data available on fuel thermal properties in the
forma fo database.A benchmarking exercised na error analysis would havee b ot carriedtuo
ine ht laboratories where these measurementse ra made.
3.2. Microstructurai changes
e onceho nteamtd dIp doe liedtimhatotnn e atpnbo otarsoe sity measuremenat, thseire
neo etidd ene thlioftyc atif oofni ssion product ga esheeTlse.c tron backscatter technique
seemo ots ffea pr ossible solution; however, dae M rzrtaeaIo Rqn ueehi.rt endi
3.3. Fuel performance modelling
The m eovdreaerlys e svheanf ltutso hieotes irvtme al conductivity unseod , %e.g5 .
thermal conductivityn acg ive risea ovt ariation ni fissions agr eleasef o betweed nna1 4 0%.
The question of microcracking and its impact on thermal conductivity was raised. It
appears that much of the degradation of this property is influenced not only by
"microcracking", but by the structural evolution of the fuel as RIM and porosity which can
have an effect on gas behaviour.
3.4. Chemical fof rfomis sion products
Informatione ht no chemistryt a fuel clads i pag important ni terms pag fo conductivity.
However, little work appears to be focused in this area. The importance of the volatile fission
products I, Te and Cs with respect to SCC was pointed out. Work has been done on this topic
t umbore FaDttenEtd eioah on fds trpofnuce e eocga bol utivltde nI UT j oyinbtly
performance.
The RTM zone might have a major impact on the performance of fuel, particularly under
transients and/or RIA conditions.
4. FISSION GAS RELEASE
e dheptee e nf dhibdsrif sseTatctonh ucwortseoe ssptehid oc l%d te1mp erroatfure
io s nkrf taewiecnolgugedrraT savs lee s. were shown displaying this depene fdihresnTtcy .
one is Vitanza's curve. The second one is Manzel's curve, which is derived from data given in
this meeting, but was first given at the last ANS topical meeting on LWR fuel performance
held at Avignion, in April 1991. It was noted that the threshold temperature for 1% integral
gas release is higher in the former curve than in the latter one in the high burnup region.
This work continues at Halden now, but the threshold temperature does not drop to the
extent of temperature difference shown in Manzel's curve in the high burnup region. Based on
the data recently obtaint Haeda eltdhhernte ,shold tee mmhopts ettr.aat u0re5 d ryobps
e dhiTfference bo cewutwrt veeehesnt results f erfoham etcM ht tta hnnaizt el curevhet ,
degradation of the thermal conductivity of the fuel has not been taken into account.
Contribution of the RIM to FGR at high burnup is not clearly identified. More experimental
datae ra needed ni order ot settle different interpretations.A comparison between commercial
LX OWfMu dnae ROlU fissios nagr elease versus burnup, grain siz denal inear heat rating
2
was beginning. CEA experiments on UO fuels exhibit a reduced fission gas release in
2+X
