Development of whole CORe Thermal Hydraulic analysis code CORTH Pan JunJie, Tang QiFen, Chai XiaoMing, Lu Wei, Liu Dong

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1 Deveopment of whoe CORe Therma Hydrauc anayss code CORTH Pan JunJe, Tang QFen, Cha XaoMng, Lu We, Lu Dong cence and technoogy on reactor system desgn technoogy, Nucear Power Insttute of Chna, Chengdu, 6004, Chna Nucear Power Insttute of Chna, Chengdu, 603, Chna Abstract ubchanne program s the man too for the core therma hydrauc anayss. By dvdng the core nto a seres of connected or dsconnected channes, the sub channe program can cacuate the enthapy fed and the fow fed of the core, and further cacuate the core DNBR.The whoe CORe Therma Hydrauc anayss program CORTH V.5 s based on CORTH V.0.Through the code core matrx agorthm optmzaton and parae method,corth V.5 s used to anayze the subchanne of the arge scae mode, descrbng the dstrbuton of therma parameters of 3D core and gve detaed feedback parameters for fue and Neutron knetcs code.the paper shows that CORTH v.5 Wth a hgh computatona effcency, and gve the correct cacuaton resuts. I. INTRODUCTION ubchanne program s the man too for the core therma hydrauc anayss. By dvdng the core nto a seres of connected or dsconnected channes, the sub channe program can cacuate the enthapy fed and the fow fed of the core, and further cacuate the core DNBR. Wth the mpementaton of the reactor core neutron dynamcs program to pn-by-pn cacuaton, the subchanne program aso needs to reach the same grd to provde the cooant feedback parameters. 4 cacuate departure from nuceate bong rato(dnbr wth core temperature fed and fow fed dstrbuton. The core modue of the software s the conservaton equaton souton. II. DECRIPTION OF THE ACTUAL WORK CORe Therma Hydrauc anayss program(corth V.0 s deveopment by Nucear Power Insttute of Chna (NPIC wth tota copyrght. The whoe CORe Therma Hydrauc anayss program CORTH V.5 s based on CORTH V.0.Through the code core matrx agorthm optmzaton and parae method,corth V.5 s used to anayze the subchanne of the arge scae mode, descrbng the dstrbuton of therma parameters of 3D core and gve detaed feedback parameters for fue and Neutron knetcs code..oftware Process and Basc Mode oftware Process The cacuaton process of the V.5 CORTH software s shown n Fgure : read data by user nput, generate the correspondng subchanne geometrc data; generate ook up tabe, ncude physca propertes, sp rato, vod fracton tabe; 3 The frst order upwnd dscretzaton s performed for the conservaton equatons of each sub channe, and the conservaton equatons of the whoe core are obtaned, The fed dstrbuton of the core s obtaned by sovng the matrx; Fg.. CORTH V.5 Process Basc Mode Energy conservaton equaton of mxed enthapy (H ( G H k q g H k L Mass conservaton equaton ( G k kr Axa momentum conservaton equaton t ( H H g 0 k ( (

2 P G gv ( G v z z f ~ kc G ( G G DE z k ( v G vkgk L Rada momentum conservaton equaton P g f ~ G g ( g v ( gv G y DE y z (3 (4.torage optmzaton and acceeraton numerca souton torage optmzaton The coeffcent matrx of the whoe core channes conservaton equaton system can be stored usng the Compressed parse Row(CR format, through the three One-dmensona array, the frst array s used for storage a nonzero vaue n the coeffcent matrx n turn; the second array s used for storage the coumns of the nonzero vaue ; the ast array s used for storage the frst nonzero array for each row. CR versus drect memory comparson s shown n fg.. Fg.. CR versus drect memory comparson acceeraton numerca souton Accordng to the characterstcs of the coeffcent matrx, we many use the generazed mnma resdua agorthm(gmre wth pretreatment agorthm to mprove the speed of the matrx. The target after pretreatment of matrx egenvaue dstrbuton n the compex pane as sma as possbe wthn the regon, commony used wth ncompete LU decomposton, ILU0 agorthm, the prncpe of the coeffcent matrx A s decomposed nto upper and ower tranguar matrx, and A respectvey wth the upper and ower tranguar part have the same non zero structure. Due to the dagona domnance of the coeffcent matrx, can be used to dea wth the bock JACOBI. GMRE agorthm s proposed by Y aad and chutz 3, startng from the Garekn prncpe, take the Kryov subspace. The comparson of effcency of dfferent numerca soutons used to souton conservaton matrx s shown n fg.3. It shows that usng GMRE to sove conservaton matrx wth arge-scae has hgher effcency. Fg. 3.Comparson of Effcency of Dfferent Numerca outons 3.Paraezaton method Parae Processng s a computatona method n a computer system that can execute two or more processes at the same tme. Parae processng can work on dfferent aspects of the same program at the same tme. The man purpose of parae processng s to save arge and compex probem sovng tme. To use parae processng, you frst need to paraeze the program, that s, the work w be aocated to dfferent parts of the process (thread. Ths report uses a dstrbuted memory regon decomposton paraesm. The method of doman decomposton s to dvde the whoe core nto a number of mutuay ndependent computng regons. The transverse nfuence of the regon s reazed by the subchannes adjacent to the regon. Regona decomposton needs to sove the cacuaton of regona dvson, the regon adjacent to the subchanne ocaton, the regona fxed pont communcaton, regona cacuaton process desgn and other ssues. Ths area s dvded by the nterface, and prepare the modue to generate subchanne geometry nformaton and coupng reatonshp n the subchanne data and generatng regon adjacent subchanne nformaton, then accordng to the adjacent subchanne to determne the communcaton between regons. The core parae area dvson d shown n Fg. 4, for a core comprsng 77 fue assembes, the regon s dvded nto 8 regons by a graphca nterface, The data transfer between regons s performed by the subchanne wth the most outer rng.

3 Fg. 4. Core Parae Area Dvson 4.Computatona effcency Ths paper compares the foowng methods: Gaussan, GMRE, ILU0 + GMRE, PGMRE, Regona decomposton. The resut show that Regona decomposton has the best computatona effcency and especay sutabe for arge quantum channe probem. Cacuaton resuts of the software ncudes 3 parts: the man parameters of the reactor core, ncudng pressure drop, specfc enthapy, mass fow rate; the parameters of DNBR, ncudng mnmum DNBR vaue and ts poston; core output temperature. It can be seen from the resuts, CORTH V.5 and FLICA cacuated the man parameters and mnmum DNBR bascay the same; the DNBR, specfc enthapy, press drop and the heght of MDNB of the hottest channe aso Aso very cose. The maxmum error of mass fow rate s.6%. Man parameters and mnmum DNBR Tabe Ⅲ. The man cacuaton resuts Vadaton CORTH FLICA err,% MDNBR MDNBR Axa heght same (cm MDNBR ubchanne 3 3 same Outet enthapy (kj/kg Dp (Mpa parameters of the hottest channe Tabe I. Case Descrpton ca se Num of Axa noda ubchann e Inet G (m 3 /h Inet Temperatur e ( Outet press (bar Tabe Ⅱ Computatona tme comparson code CORTH CORT CORT CORTH CORTH H H storage drect CR CR CR CR mode Numerca gaussan gaussa GMRE PGMRE Parae souton emna ton n em naton (one core case / case / case 3 / case 4 / oftware verfcaton Exampes Ths exampe s the core of /4 computng, n whch FLICA 4 and CORTH used subchanne dvson typca, ncudng 4 sub channes. To cacuate the DNBR, FC reaton s seected n the exampe. Cacuaton resut anayss

4 Fg. 6.core temperature dstrbuton wth channe mxng Fg. 5. The hottest channe axa parameter of ACP00 core 6.Anayss of the whoe reactor core The power of ths paper comes from the NGMC fue rod eve power dstrbuton, whch s dvded nto 5 sectons n the axa drecton. Fg. 6 s the detaed temperature dstrbuton of the core wth channe cross mxng and Fg. 7 s the detaed temperature dstrbuton of the core wthout channe cross mxng ( s the core of the core and for the core outet. It can be seen that the cross mxng between the channes makes the core temperature dstrbuton more unform. III. REULT Fg. 7. core temperature dstrbuton wthout channe mxng The whoe core subchanne software CORTH v.5 s based on CORTH V.0 software. Through the code core matrx agorthm optmzaton and parae method, CORTH V.5 s used to anayze the subchanne of the arge scae mode, descrbng the dstrbuton of therma parameters of 3D core and gve detaed feedback parameters for fue and Neutron knetcs code. The paper

5 shows that CORTH v.5 Wth a hgh computatona effcency, and gve the correct cacuaton resuts. IV. CONCLUION The deveopment of the software CORTH v.5 provdes a effectve too for the core therma hydrauc anayss. Through the whoe core anayss may provde a hgher safety margn, and more accurate cacuaton of the core coupng. NOMENCLATURE t =tme =densty H =specfc enthapy =fow area z =noda axa ength =ength g =transverse mass veocty L =ength of between subchanne kr =mxng heat dffuson coeffcent q =surface heat fux G = manstream mass fow rate P =pressure gv =gravty acceeraton v =specfc voume f =frcton coeffcent kc =resstance coeffcent DE =hydrauc dameter =mxng vscosty coeffcent =current subchanne k = adjacent subchanne REFERENCE Nachtga N M, Reddy C, Trefethen L N, how fast are nonsymmetrc matrx teratons, IAM J.Matrx Ana.App.3(99, Nachtga N M, Reche L, Trefethen L N, A hybrd GMRE agorthm for nonsymmetrc near systems, IAM J.Matrx Ana.App.3(99, Y. aad, M.H. chutz. GMRE: A generazed mnma resdua agorthm for sovng nonsymmetrc near systems, IAM J.c. tat. Comput, 7( Raymond P, pnder B, Lenan R. Pressurzed Water Reactor Therma-Hydrauc Core Anayss wth the FLICA Computer Code. Nucear Engneerng and Desgn. 990, 4: