Pieroni, N.

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Februar 1976Institut für Angewandte SystemanalyseKFI< 2257ArgerlltiU1111-G(!l!rm~ti1 C«lltnlpelratöOml (Q)~1l f~~~ CW~~®Optimizilltioll1IFoII' thra Nucletilll!' POWefi' P~3:]nt Atm~ha[ßllJlm-lIIp C[ß~lCu~ati(Q)m~ ftnlf th® AtllJl~h«ll NIlJl~i®Sl~' f?![)Jwm'RffJl~ctowN. Pieroni/GESELLSCHAFTFÜRKERNFORSCHUNG IVI.B.H.I<ARLSRUHEAls Manuskript vervielfältigtFür diesen Bericht behalten wir uns alle Rechte vorGESELLSCHAFT FÜR KERNFORSCHUNG M. B. H.KARLSRUHEKERNFORSCHUNGS ZENTRUM KARLSRUHEInstitut für Angewandte SystemanalyseArgentine-German Cooperationon Fuel Cycle OptimizationFor the Nuclear Power Plant AtuchaBurn-up Calculations for theAtucha Nuclear Power Reactor~Nestor Pieroni +)KFK-2257+) Delegate from Comision Nacional de Energia At6mica, ArgentinaGesellschaft für Kernforschung m.b.H., KarlsruheP r e f aceA basic agreement on cooperation in scientific research andtechnological development was signed between the governmentsof the Federal Republic of Germany and of the Republic ofArgentina on March 31 st, 1969.Within the frame work of this basic agreement a specialcooperation agreement for the peaceful uses of nuclearenergy between the Comision Nacional de Energia Atomica(CNEA) and the Gesellschaft für Kernforschung (GfK) cameinto effect on July 29 th, 1971.Under these cooperation agreements it was decided in 1974to study, among other items, the possibilities to increasethe discharge burn-up values of the fuel elements of thenuclear power plant Atucha. Work related to this projectwhich was performed in 1974 is contained in a progressreport KFK-2133 issued in July 1975.Due to technical reasons, documentation of the burn-upcalculations performed by Mr. Pieroni in 1974 was delayedand therefore could not be included in KFK-2133. Resultsof this work are now presented in this report.Hans-Jürgen ZechJanuary 1976Abbrandrechnungen für das Kernkraftwerk Atucha.Z usa mme n f ass u n 9Die physikalischen Eigenschaften des Kerns während des Abbrandes desSchwerwasser-Kernkraftwerkes Atucha werden untersucht. Das Zellrech-nungsprogramm HAMMER und das Abbrandprogramm CITATION werden angewen-det.Zwei Fälle werden studiert: 1) Ein Natururankern, der im Gleichgewichteinen Entladeabbrand von ca. 7.0 MWD/kg erreicht; 2) Ein 1% homogenangereicherter Urankern, der im Gleichgewicht einen Entladeabbrand vonca. 15.0 MWD/kg erreicht. Die Ergebnisse zeigen die Anwendbarkeit desProgrammsystems für die Studie zur Optimierung des Brennstoffzyklusdes Atucha-Reaktors.A b s t r a c tThe physica1 characteristics during the burnup of the core of theAtucha heavy water power reactor are investigated. The 1attice programHAMMER and the dep1etion program CITATION are app1ied.Two cases are studied: 1) a natural uranium core, which provides adischarge burnup of approximate1y 7.0 MWD/kg; and 2) a 1% ho~ogeneous1yenriched uranium core, which provides a discharge burnup of approximately15.0 MWD/kg. The results support the use of the program system for thestudy of the fuel cyc1e optimization of the Atucha reactor.-1-1. INTRODUCTIONIn order to increase the burnup of the natural uranium heavy-waterAtucha power reactor several possibilities are envisaged: homogeneousand heterogeneous uranium enrichment, homogeneous and heterogeneousplutonium recycling, and possibly others.The possibilities mentioned require to be investigated as regardstheir technical feasibility as weil as their economic aspects. Theadvantage of adopting one or the other possibility can be deternlinedin accordance with the requirements of the nuclear power pro gram.A reliable calculation procedure is needed so as to perform aninvestigation of the physical characteristics for the different possi-bilities. A generalized fuel cycle program system, available at Karlsruhe,has been applied to the case of the Atucha reactor. This system includesthe HAMMER program /1/ for the lattice calculations, and the CITATION program/2/for the composite reactor calculations. The mass balances·obtained fromCITATION can be used in the CINCAS-II program /3/ to calculate the fuelcontribution to the total electrical generating costs.In the present study the program system has been appli.ed to the caseof the Atucha reactor with natural uranium core -which is the referencecase- and to the case of a 1 % homogeneously enriched uranium core.11. LATTICE CALCULATIONS11.1 Atucha lattice cellThe heterogeneous Atucha reactor lattice is described by the multi-group transport theory lattice program HAMMER /1/. The multigroup homogeneizedcross sections from the lattice program are condensed to produce a set offour-group cross sections with upper energies: 10 MeV - 1.05 MeV - 9.12 KeVand 0.625 eV. The four-group microscopic cross sections are transferred toan input library for the composite reactor calculation.-2-A cross-sectiona1 view of the Atucha fue1 bund1e is shown in Fig. 1.Details of compositions and dimensions of the Atucha reactor, providedby the Kernkraftwerk Union (KWU) /4/ are given in the appendix. In Tab1e Ithe 1attice geometry and compositions used in the present ca1cu1ationsare given.11.2 Ce11 ca1cu1ation resu1tsThe results obtained with the HAMMER program for the natural uraniumce1l are shown in Tab1e 11. For comparison, the corresponding va1uesobtained by KWU with their own program CIRTHE are also given /4/. It canbe seen that good agreement between both ca1culations is obtained.The concentrations corresponding to the different degrees of burnupare app1ied in the HAMMER program to obtain the variation of the infinitemu1tip1ication factor as a function of burnup. It can be seen in Fig. 2that for the natural uranium case, the infinite mu1tip1ication factor issma11er than unity for burnup va1ues greater than 4.2 MwD/Kg. This valuecan be considered as the maximum burnup obtainable from the first fue1elements to be discharged from the initial core.The parameters corresponding to the 1 % enriehed uranium ce11 areshown in Tab1e 111, and in Fig. 3 the variation of the infinite mu1ti-plieation faetor as a funetion of burnup is given. In this ease thisfaetor is smaller than unity for burnup values greater than 7.1 MwD/Kg.111. REACTOR BURNUP CALCULATIONS111.1 Atueha geometrie meshThe finite-differenee diffusion theory program CITATION /2/ is apDliE~dto salve the depletion problem with elaborate refuelinR treatm~nt fOTmulti-cycle analysis.-3-A eross-seetional view of the Atueha reaetor geometrie mesh is shownin Fig. 4. The ea1eulations are performed for a three-dimensional hexa-gonal geometry. Individual fue1 elements are represented by eorrespondingzones. This detai1ed representation of the reaetor geometry requireseorresponding1y 10ng eomputation times. A typiea1 time step in the mu1ti-eye1e analysis requires approximate1y 2.4 min CPU time.In order to investigate the aeeuraey obtainab1e with a two-dimensiona1hexagonal geometry representation, a para1e11 ea1eu1ation has been intended.But the version of the CITATION program avai1ab1e at Kar1sruhe, ca11ed:CITATION ISSUE DATE 07/01/71did not work correet1y for this geometry Ist. The 1atest version of CITATION,ca11ed: CITATION - REVISION 2 (JIDY 1971) - SUPPLEMENT 2 (MARCH 1972)is presently being ineorporated and tested, and it is expected that thediffieulties mentioned will be overcome.111.2 Influence of isotope eoncentrationsFigs. 2 and 3 give the effeet on the infinite multiplieation faetordue to the different isotope coneentrations. The corresponding cross seetionsare also affeeted by the variations of the isotope concentrations. For thepresent study it is relevant to know to what extent the reaetor burnupealeulations are influeneed by the variations in the mieroseopie input data.To investigate this effeet, aseries of reaetor burnup ealeulations areperformed with different mieroseopie eross-seetion data. For the naturaluranium ease, the eross-seetion da ta are obtained from ea1culations withthe HAMMER program of cells with isotope concentrations corresponding toburnup values ranging from 0 to 7.2 MwD/Kg. In all cases the maximum variationin the reactor burnup value was smal1er than 2 %. Therefore for the naturaluranium case the mieroseopie data eorresponding to the fresh cell hasbeen adopted.For the enriched uranium ease a simi1ar investigation is made in theburnup range from 0 to 18.0 MwD/Kg. The microscopic data set corresponding-4-to a cell with a burnup of 9.6 MwD/Kg has been seleeted. With this dataset the maximum variation in the reaetor burnup value is smaller than 5 i..111.3 Results for the natural uranium easeFig. 5 shows the variation of the effeetive multiplieation faetor asa function of full power days (fpd) of operation after starting with afresh eore without fuel management manipulations.The variation of the eoncentrations of the plutonium isotopes and ofthe 235U isotope in a fuel element as a funetion of burnup is shown in Fig. 6.A fuel management program is developed in order to obtain the equi-librium core condition. Due to the detailed reactor mesh adopted, theburnup of every individual fuel element can be determined and the eorres-ponding thermodynamics requirements (see appendix) can be verified.Aceordingly, a convenient fuel management manipulation can be found tooptimize the obtainable burnup. A fuel management scheme results withfresh fuel elements being introdueed in an intermediate region in the eore.After reaching a burnup of approximately 2.0 MwD/Kg the fuel elements aremoved to the central region of the core. There they obtain a burnup ofapproximately 6.0 MwD/Kg before being moved to the outer region of the core,from where they are later diseharged. With this -shortly deseribed- fuelmanagement scheme, which requires replacement or shifting of approximatelyone fuel element every full power day, the equilibrium eore eondition isobtained after approximately 950 fpd.Fig. 7 shows the power shape faetor for every fuel element after 950 fpd.In Fig. 8 the corresponding burnup distribution, normalized to the centralzone, is shown. The discharge burnup is approximately 7.0 MwD/Kg, and theaverage burnup of the eore is approximately 4.0 MwD/Kg. These values agreewith the corresponding ones obtained by KWU.-5-111.4 Results for the I % homogeneously enriched uranium caseFig. 9 shows the variation of the effective multiplication factoras a function of time after starting with a fresh core without fuel mana-gement operations. The concentrations of the plutonium isotopes and ofthe 235U isotope in the I % enriched uranium element as a function ofburnup are shown in Fig. 10.A similar fuel management scheme as in the natural uranium case isapplied to obtain the equilibrium core condition. In the enriched uraniumcase the fuel elements must have a burnup of approximately 6.0 MwD/Kgbefore they are moved to the central region of the core. One fuel elementmust be replaced or shifted every 2.2 days, approximately. The equilibriumcore condition is obtained after approximately 600 fpd of operation.Fig. II shows the power shape factor and Fig. 12 the burnup distribu-tion in the core after 1000 fpd. In the equilibrium core condition thedischarge burnup is approximately 15.0 MwD/Kg, and the average core burnupis approximately 9.0 MwD/Kg.IV. CONCLUSIONSThe results of the physical calculations performed with the generalizedfuel cycle program system available at Karlsruhe agree with the known valuescorresponding to the Atucha reactor with a natural uranium core.The results for the I % homogeneously enriched uranium core also agreein the range expected according to previous approachs.This confirms the reliability of the program system for the burnupanalysis of a heavy water reactor.In particular, the present study supports the confidence in the use ofthis program system to investigate other possibilities of improving thefuel cycle of the Atucha reactor.-6-Table IAtucha lattice callRegion 1r= 5.585cmRegion 2d =15.70 cmIsotope Average concentration ( at/b.cm)Natural uranium case I % enriched uranium case~ 238u 7.368 E-03 1'.347 E-0323SU 5.284 E-OS 7./-+21 E-OSRegion I< 0 3.200 E-02 3.200 E-02T=770oC"Zry" 6.263 E-03 6.263 E-03D 3.424 E-02 3.424 E-02... H 8.582 E-05 8.582 E-05Region 2 D 6.613 E-02 6.613 E-02T=227oC~H 1.658 E-04 1.658 E-040 3.315 E-02 3.315 E-02-7-Table IINATURAL URANIUM caseCell Parameters / Clean Hot CriticalPARAMETER CIRTHE HAMMERETATH 1.2495 1.2573F 0.9563 0.9855ETATH~F 1.1922 1.2391L2 2.5826 E+02 2.4416 E+02DTH 1.0044 0.8928EaTH 0.3889 E-02 0.3657 E-02;> EfTH 0.4859 E-02 0.4531 E-02P 0.8924 0.8456AGE 1.3541 E+02 1.0436 E+02KQ:) 1.0919 1.0947KEFF 1.0457 1.0526ABS (238U)0.4050 0.4116PROD (235 U)ABS (235T]) 0.4886 0.4851PROD (235U)E 1.0218 1.0443-8-Table UI1 % ENRICHED URANIUM caseCell Parameters / Clean Hot CriticalET&rH 1.4180F 0.9874ETATH* F 1.4000L2 2.1269 E + 02DTn 0.8928LaTH 0.4196 E - 02~ EfTH 0.5877 E - 02P 0.8404AGE 1.0417 E + 02KQ? 1.2337ABS (238U)0.3224PROD (235u)PROD (238u)0.01721PROD (235u)ARS (235u)0.4862PROD (235u)t 1.0571-9-Supporting rod~ Fuel rods~-11.17cm--------"Fig. 1 Cross Sectional View of Fuel Rod Bundle-1(1-N.QlI.LCl.:::JCL-:::J0)-.-0CID0+J0)U~C- :::J"C LLLn~ 0:oE -- 1fI--Cl. Q) 0:::J UC L..L- 0:::J E +J-..t CD U::J J:.-e0 cL-::::> .Q+J0 0L- U::J c........ö~Z :::J« 2I Q)U :+.=:J c~-.-c-I201816148 10 12Burnup [MWd I kg ]6420.81.01.21.3 i I I i i i ii i i i iI0.91.18~Fig.3 ATUCHA Enriched Uranium CeH :Infinite Multiplication Factor as a Function of Burnup-12 -xZones 1 to 51: FuelZone 52 : ReflectorFig.4 Cross Sectional View of the Geometrie Meshfor the ATUCHA Reador Calculationl061.05l04l03-- ICI '".x II-1.02....,I1.0110 20 30 40 50Time [ FPD J60 70 80 90Fig.5 Natural Uranium Case :Effective Multiplication Foctor os a Function of Time-14-98Pu239Pu 21..032Pu 21..1 j~:-d:::::::::::i:::::::==:=!====JI=-=:::i:L=-=-=-~:LI-=-=-=-=~I-=-=-=-=~I _L. 5 6 7 8 9 10Burnup [ MWd / kg 17236~d+-'c 5::>Cl..lI::-~Cl4Fig.6 ATUCHA Natural Uranium Fuel :Isotope Concentration os a Function of Burnup-15-xFig. 7 Natural Uranium Case :Power Shape Factor (Equilibrium Core )xFig.8 Natural Uranium Case :Burnup Distri bution Normal ized to theCentral Zone (Equilibrium Core)--I.l.x1.21.11.0 ' , I I , I I I I , I I I I I I I J , I ,'-Il10 50 100Time [FPD]150 200Fig.9 1% Homogeneous Enriched Uronium CoseEffective Multiplicotion Foctor os 0 Function of Time-18-10 .----,-----,.--...,-------,---.,...-----,---,----,---,----,8620Pu 21.0PuPu 2398 10 12Burnup [ MWd / kg l52379c::.....d.-.....Fig.10 ATUCHA 1% Enr iched Uronium FuelIsotope Concentrotion os 0 Function of Burnup-19-0.40@1.73 @) @@ @1.62 @ S @@ @) .@)@ @) @) @@ @ @ @@ @) @ @1.46 @) @ @1.62 @ @ @1.81 ~ . @1.72 @ @0.82 @0.39Fig.11 1% Homogeneous Enriched Uranium Case :Power Shape Factor (Equilibrium Core )x-2()'-xFig.12 1% Homogeneous Enriched Uranium Case :Burnup Distribution Normalized to theCentral Zone (Equilibrium Core )-21-AppendixData list AtuchaF~EL Natural uranium dioxideEffective densityPellet radiusMean temperature9.9 g/cm30.54 cm770 oeARRANGEMENT OF FUEL RODS1 central rod6 rods in a circle, radius 1.60 cm12 tI " " tI " 3. 04 cm17 " It " " " 4.52 cmThe outer circle also includes a supporting tube made of Zry-4 withan internal radius of 0.475 cm, wall thickness of 0.12 cm and6.55 g/cm3 density.eLADDING TUBE Zry-4Density 6.55 g/cm3Inner radius 0.54 cmEffective wall thickness 0.06 cmeOOLANT D20 with 0.25 %weight H20Mean temperature 288 oeCALANDRIADensityInner radius'liry_4-22-5.41 cmEffective wall thicknessMODERATORMean temperature0.175 cmLattice pitch 27.2 cm (trigonal arrangement)Effective core heightEffective core radius530 cm227.15 cmReflector thickness: axial upper partaxial lower partradial45.5 cm46.5 cm24.05 cmPower limi ta tions: maximum power per channel Q~7.2 Mwmaximum linear power q' ~ 500 w/cmmean linear power q' ~ 216.5 w/cmmacroscopic form factor F = F d * F . 1 ~ 2.07ra ax~a-23-References1. J.E. Suich and H.C. Honeck: "The HAMMER System", DP-1064 (1967).2. T.B. Fow1er, D.R. Vondy and G.W. Cunningham: "Nuc1ear Reactor CoreAnalysis Code: CITATION" , ORNL-1M-2496 (Rev. 2), (1971).3. LW. Craig and W.W. Brandfon: "Nuc1ear Fue1 Management", PowerEngineering~, 38 (1971).4. H. Raum, Kernkraftwerk Union AG, Erlangen, private communication.5. H. Bogensberger and H.-J. Zech, Gesellschaft fuer Kernforschung m.b.H.,Kar1sruhe, private communication.ACKNOWLEDGEMENfSThe present report reviews some of the initial efforts performed inthe frame of the Argentine-German joint work on the fuel cycle optimizationof the Atucha nuclear power reactor.The Gesellschaft fuer Kernforschung m.b.H.provided finantial supportfor my stay in Karlsruhe as weIl as for the extensive use of the computationalfacilities required by this work.I would like to acknowledge the assistance provided by Prof. Dr. H. Lauethrough the International Office of the Karlsruhe Center. I would also liketo thank Prof. Dr. W. Haefele for providing me with a place at his Instituteof Applied Systemtechnique and Reactorphysics (IASR) , and to Dr. P. Mc Grathfor his help.I would like to acknowledge the contributions from members of the Kern-kraftwerk Union AG, in particular from DP. F. Dusch, Dr. H. MoldaschI andDI. H. Raum, who provided information and helpful discussions.Finally I would like to mention the generous assistance provided bymany persons of the IASR during the nice period I spent at the KarlsruheCenter.

Argentine-German Cooperation on Fuel Cycle Optimization for the Nuclear Power Plant Atucha. Burnp-up Calculations for the Atucha Nuclear Power Reactor

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Argentine-German Cooperation on Fuel Cycle Optimization for the Nuclear Power Plant Atucha. Burnp-up Calculations for the Atucha Nuclear Power Reactor

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