Safe core management with burnable absorbers in WWERs

230 Pages·2002·4.82 MB·English

IAEA-TECDOC-858
Safe core management with
burnable absorbers in WWERs
INTERNATIONAL ATOMIC ENERGY AGENCY
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The originating Sectif oothn is publie cIhaAttE ionAin was:
Nuclear Power Technology Development Section
International Atomic Energy Agency
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SAFE CORE MANAGEMENT WITH BURNABLE ABSORBERSN I WWERs
IAEA, VIENNA, 1996
IAEA-TECDOC-858
ISSN 1011-4289
© IAEA, 1996
Printed by the IAEA in Austria
January 1996
FOREWORD
In the framework of its activities on in-core fuel management and related core physics matters,
the IAEA carried out a number of Co-ordinated Research Programmes (CRPs) in the period 1987-
1994. f oMthoess te programmes conf sovisatleidd f aotiino-nc sore fuel management
programmesr of lighd tna heavy water reactors (i.e.r of PWRs, BWRs, WWERsd na PHWRs).
Operational results from selected reactors were obtained and compared with calculations.
Duringa consultants meeting ni December 1988s aw ti recommended thate ht IAEA initiatea
Co-ordinated Research Programme on Safe Core Management with Burnable Absorbers in
WWERs. The goal of the programme was to verify corresponding calculational methods and
computer codes with experiments and to contribute to the background for safety analysis and
reliable operatf igooan dolinium containing n fWuieW l ERs.
The objective of this TECDOC is to present state of the art information on burnable poisoned
fuel duringe ht CRPs i .tIb ased no experimental evidene ht cnuo denta ilization fo theoretical
models and will help achieve improvements in safety and economy of LWR cores with hexagonal
geometries.
The IAEA wishes to thank all the contributors to the CRP and the report, particularly the
participants who volunteered to prepare each chapter.
EDITORIAL NOTE
n Ipreparing this publicatior onfp ress, e hsIttA faofEf A have me ahptd apueg es froemht
original manuscripts ass ubmite thaet yudb thore shvT.i ews exprest osnne oeddc essarily reflect those
e ghotof vernments e nhotof minating Member Stae tr nheootosf minating organizations.
Throughout the text names of Member States are retained as they were when the text was
compiled.
The use of particular designations of countries or territories does not imply any judgement by
e elpehhgutatb lol isste tIh aAhsetEatur A,s ,of such countr rtioeers ritories, of their authodrintiaes
institutions or of the delimitation of their boundaries.
The mention of names of specific companies or products (whether or not indicated as registered)
t doy oinmneinasp tley nto iotinn fringe proprietary rir gose hhnbtcsoo, utnnilsad tr suaed
endorsement or recommendation on the part of the IAEA.
The authors are responsible for having obtained the necessary permission for the IAEA to
reproduce, translate or use material from sources already protected by copyrights.
CONTENTS
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7. . . . .
2. Computational methods .......................................... 11
2.1 Multigroup libraries and resonance treatment - basic library treatment ......... 15
2.2 Space-energy calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.2. ..
2.3 Buraup calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23
2.4 Sources of discrepancies in results ................................ 25
2.5 Accuracies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 26
. 3 Experimentsd na calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..13
3.1 ZR-6 critical assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13. ..
3.2 LR-0 experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . 53
3.3 Rheinsberg experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 83
4. Theoretical benchmarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 93
4.1 Hexagonal lattice (Sidorenko) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 93
4.2 Square lattice 4x4 (Maeder/Wydler) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 141
4.3 Square lattice 3x3 (Arkuszewski) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 192
5. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 219
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 223
Annex : Outline for a new Co-ordinated Research Programme . . . . . . . . . . . . . . . . . .. 233
Contributors to drafting and review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 235
. 1INTRODUCTION
The specification of the reactor core, which depends on its nuclear characteristics, is an
essential pan rint uclear safed nteayc onomic evaluations. These nuclear characteristics affeehctt
neutron behavioure n ptahouinwrtdn ,e ,re fduhiestlt rcidbyunctlieao. n Incento ievetxehts entd
burnup and the duration of the fuel cycle and hence to improve the fuel economics, lead to higher
enrichments in fissile materials and create a need to improve neutron flux distribution and
reactivity control. This need is often met by using burnable neutron absorbers, integrated in the
fuel matrix. Burnable absorbe uerasro se stdm ooth power diso trative bdcohuanoittd ar ineo in
positive moderator temperature reactivity coeffice ihbet etnagt inne hfitnu feog l cycle.
Because of its suitable nuclear properties and its relative abundance, the use of gadolinium as
burnable abse os hfaburthbe eneel inr successn fBuil W rRooo fvdsw eetcr ad dtnehasi, s practice
is now being extended for PWRs. Gadolinium burnable absorbers are not used in current
operating WWn ioE rtRudo besto,r ptime ihfzutee l cy dncealne hance operational safeentoy,
should also introduce burnable absorbersn i these reactors. Consequentlys i tia nticipated thaetht
rkononfn webeloue drdnga eble absorbers willn cgoirouwn tries operating d WthnaWtaER s
adequate tools for properly calculating local effects in hexagonal geometries should be developed
and validated.
The advantages of Gd over other burnable absorbers like B are manifold:
it can be used as integrated burnable absorber in the fuel matrix;
o tth eeuird lar -ge absorption cross-sections Gd-155, Gd-157 isotopes bt uufraons ter;
the formation of tritium is reduced if the Gd-absorber is used (decrease of the fission gas
pressure);
in order to design long fuel cycles, one can use Gd in the fresh fuel of every reload batch so
that the initial concentration of soluble boron can be maintained reasonably low and that one
wout olfndae chpter obla ep fmoo sitive moderator temperature coefficient; n taah dsiisd ed
operational safety feature;
- a high burnup of 40-50 MWd/kgU can be achieved by increasing the enrichment and
approe pd fhcrrGieotasnt hent eifnu tel; e cbhoetnc vafeuorss fe iUoon- 2o P3tu8 -239, there
wila elhb igher energy outpur etp unit massf o mined.U
Because of the above mentioned reasons, an additional CRP was initiated with the aim to
increa eshtek nowledg noer eactor fuel containing burnable absorben risW WERn si,w hich
experiments were carried out and theoretical methods for cell calculations were developed.
Twelve institutes n frceootmu ntries parte ichCix tpRii anSntPseitd. i tutes held research
contracts, three held research agreed mtnheranetes particip saoatebd servers (see Table 1A.1) .
list e wfhuilttlh addresss egisi ven else erhewtph onerrite.
The design of reactor fuel containing burnable absorbers and the corresponding in-core fuel
management require computational methods and cross section libraries with a high degree of
accuracy, in order to adequately address all safety and economy related problems. Therefore
participants started wa idthe tailed library sdeo anrctcaohl l eRcd tmW ndoaadBtae ls rousfed
PWR fuel. This enabled them to define a programme for identifying lacking data in libraries,
setting up necessary experiments and developing adequate computer programs.
In ordeo rt facilitate readine ghtr eport, Chapts aehb 2re en devote ehtd dote scriptieoht nfo
computer code evhsat ru inoseuids benchmarks.
In Chap3 tevr arious experiments perforo mcteodm e pheaxtrpe erimental results ewhitth
calculational ones are included. The experiments comprised critical experiments performed at the
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10
Table 1.1. PARPTRICC IEPHATN NTIS
Country Institute Abbre- Type of Chief Scientific Investigator
viation of involvement and co-workers
Institute
Bulgaria Institute for Nuclear INRNE Contract Ms. R. Prodanova
Red Nsenuacracleh ar Mr. K. Ivanov
Energy Mr. T. Apostolov
Cuba Higher Institute for CUBA Contract Ms. C.M. Alvarez Cardona
Nuclear Scidenncae Mr. R. Guerra Valdes
Technology . LDMopr e.z Aldama
Czech Nuclear Research NRI Contract Mr. J. Vanicek
Republic Institute Mr. J. Bardos
. MKZarl .esky
SKODA SKODA Observer Mr. N. Vacek
Finland Technical Research VTT Observer Mr. M. Anttila
Center of Finland
Germany Kraftwerks- und VEB Agreement Mr. R. Becker
Anlagenbau
Inrsütiftu t KE Observer Mr. D. Lutz
Kernenergetik
Hungary KFKI Atomic Energy AEKI Contract Mr.. I Vidovszky
Research Institute Mr. .C Maraczy
Mr. A. Kereszturi
M. GrH. egyi
India Bhabha Atomic BARC Agreement .MJVarg .annathan
Research Center Mr. P.D. Krishnani
Mr. R.P. Jain
Mr. Vinod Kumar
Mr. H.C. Gupta
Poland Institute for Atomic SWIERK Contract Ms. T. Kulikowska
Energy . BS z.scMzesna
Ms. V.B. Sadowska
Russia Russian Research RRCKI Agreement Mr. V.V. Pshenin
Center "Kurchatov Mr. A.P. Lazarenko
Institute"
Serbia Institute of Nuclear VINCA Contract Ms. N. Marinkovic
Sciences, VINCA
ZR-6 critical facility in Budapest (Hungary), new experiments performed at the LR-0 reactor in
Rez (Czech Republic) and experiments under operating conditions at the NPP Rheinsberg
(Germany). Three theoretical benchmarks and their analytical results are described in chapter 4.
A simple hexagonal Sidorenko benchmark, which ca osn isfniogstlse pd ipGnicn ecaleall .l ,
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Table 1.2. INVOLVEMENT OF THE PARTICIPATION INSTITUTES IN THE CALCULA-
TIONS AND THEORETICAL BENCHMARKS IN CHAPTERS 3 AND 4
Institute ZR-6 LR-0 Rheinsberg Hexagonal Square Arkuszewski
lattice lattice
INRNE X X X X
CUBA X X X X X X
NRI X X X X X
SKODA X X X
VTT X X X X
VEB X X X X X X
IKE X X X
AEKI X X X
BARC X X X X X
SWIERK X X X X X
RRC KI X X X X
VINCA X X X X
e n hcaastesu ntdsapnte reanmer icpbe ldlyGl wceenilotlh wd piGts ihacn whs,o t sutehBnis.
benchmark places an emphasis on Gd cross sections and Gd cell modelling because it can't reflect
various heterogeneities w ehruaicshu ally encoua npt oenrwieed r reactor fuel assembly.
Accordin ogswlqtyu are lattice benchmarks were also chos reoafnna za selie yr hfeosTiniross. t
burnup benchmark formulated by Arkuszewski which consists of a 3x3 lattice with a single Gd pin
in the centre. A Monte Carlo reference solution with ENDF/B-5 data for Gd isotopes was
available for this benchmark. The second benchmark was a more difficult one formulated by
Maeder/Wydler with two adjacent Gd pins in a 4 x 4 square array. This benchmark is now
commonly used in modern BWRs and has been analyzed by NEACRP group earlier.
Tab2 l.1eg iven aso vervie ehitw nfod ividual participate ihoit nfnos titue thcte nasi lculations
and theoretical benchmarks.
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2. COMPUTATIONAL METHODS
The analysis of benchmark tasks defined under Co-ordinated Research Programme on "Safe
Core Management with Burnable Absorbers in WWERs" has been performed in two steps: first
e htbasic parametere hst fio nvestigated lattice have been calculated a yb lattice type coded na then
the few group diffusion or transport constants have been prepared and used in subsequent
supercell or assembly calculations. Not all the tasks required the second step of calculations, but
the first step has been an inevitable part of all the benchmark tasks. Moreover, all final results
d emhepto ed ndmnnoedael st hods usn eliad ttice calculatie oshenTcso. nd n sitanectpr owduecne
discrepancies of results through the homogenization method applied within elementary cells and
group collapsing.
The benchmark tasks have been calculated by CRP participants from 10 countries using 7
different cr looadtfteis ce calculations. Tf htorheee se codes, WIMSD-4, NESd SREnSLaY-4 ST,
have been applied by more than one participating country and in some cases the tasks have been
analized in one country by two codes. The list of applied codes is given in Table 2.1. The
majority of these codes has been developed in the form of modular systems of programs with the
choice of modules needed in a particular calculation left to the user.
The KARATE, TVS and CASMO modular systems include the 2D diffusion or transport
programr obfso th hexagod nnsaaql uare geometris eatsh n mweioor dules and, thuo sna, dditional
programs hae vaehf n abbotleeynesc ni hsr mnoeaerfkdf en Co dtcaAaIsdsSk eMs n.Oa-3G
CASMO-HEX only 2-D transport modules were used although both codes have also 2-D modules
based on diffusion theory. In case of KARATE the lattice and burnup calculations are realized in
e htBETTY module ehTc. odes EXCEd LnSa UPERe hst eBasum e latice code MURLr oIfs ingle
pincell as well as supercell calculations. These calculations are done in 28 groups with the cross
section library obtained by collapsing the 69-group WIMS library with a typical spectrum for the
WWER/PWR lattice. Supercell spe eucro stacretoad llapse different region cross sectio ofntivs e
groups. HEXG/MINIXY perform the 2-D diffusion calculations in hexagonal/square geometry.
Several codes, NESSEL, WIMS, RSf YSoSWT IERK, include only mdr oldoanutftlaiecs e
cell calculations. These codes deliven rit,h eir final stee hlpat, ttice multiplicationw feaf cdtnoar
group transport and diffusion constants homogenized over an elementary cell or a chosen fragment
of the considered reactor lattice, together with required depletion data. In that case separate
two-dimensional (2D) diffusion codes have been used to get the assembly or additional supercell
data eg., rectangular and hexagonal modules of CITATION at IAE, SNAP-3D at CUBA [1],
FLEX at VEB [2], HEXAB-II-30E at INRNE [3]. The diffusion codes in hexagonal and
rectangular geometries have been needed to meet the benchmark tasks requirements.
efhotl lnoIwing anale ydhstiiss cussis omin an dtiee r fmoaps proaches relato ectddo ndaes
o ptart itcoulanr code users. However, whenever nece edshisfafteryr e,nces between different
e hsuatsm efores c eormdaee ntioned. Sie nphcrtee senPt e RbacpC hopat lpli lcstaeia r bolte
benchmark tasks, e obhnaltsy ic characteristf ipochs ysical md oadnpeapls roximations commootn
l latask erasd iscussed here eht,d etailed information relateo dt separate tasks, being leoftt
chapters devoe thdet odet scriptiof nop articular tasks.
e ahnTaf lyloastits ices wa ihthe faovy tbeu esrct nbauwa rabr oiiolteeh d t a bssaorhbe r
appropriately chosen approximations and physical modelling of the calculated system. The basic
model of a unit pincell and two types of supercell discussed below are shown in Figs. 2.1-2.3.
e theTrms 'macro dc'nseualFp ercell' usn tes hiwda s isoe atl hler chape dtreearfs ins faeod llows:
Ba y'm acro ecwuenlFd erstaa nfdr agmf oerena tctor lattice with heterogeneous internal
structure which has a repetetive nature. By a 'supercell' we understand a calculational model of a
macrocell which si assumee db ort epeated infinitely.
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