ML061880471
| ML061880471 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 02/04/1981 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Sherwood G General Electric Co |
| Julian E | |
| References | |
| 50-271-OLA, ASLBP 04-832-02-OLA, RAS 11812 NEDO-24154, NEDO-24154P | |
| Download: ML061880471 (51) | |
Text
UNITED SVATES NUCLEAR REGULATORY COMMISSION 3WASM4INGTON.
- 0. C.,0&73e FEB 4 Dr. G. G. Sherwood, Manager Safety and Licensing General Electric Company 175 Curtner Avenue San Jose, California 9l14 Cear Dr. Sherwood:
SUBJECT:
ACIEPTAtICE FOR REFE.RENCIIG GEIIE.:AL ELECTRIC LICEI-NSI.%G TOPIC.L REORT 'IE;,Ct-24l.4/NEDE-241 54P The Nuclear Regulatory Cmilsslon has completed its review of the General Electric Company Licensing Topical Report NED0-24154 Volumes I and II and
,EOE-24154 Voluer IHT entitled "Qualificatlon of the Onc-.l1menslonal Core Transient Podel for Boiling Water Reactors" and the supplmerrtal infor-mation Eubaittcd by St H. Buchholz, ltiter (MFN 155-80) dated Septwber S, l19O.
This report describes the General Electric transient analysis code, ODYN.
This code is to be uied for transient analyses of the following eight transients:
A.
For Thermal Limit Evaiuation Thermally Limiting or Event Near Limiting (Tioicallv)
I.
Fee.water Controller Failure -X Maximuwm Demand
- 2.
Pressure Regulator Failure - Closed
- 3.
Generator Load Rejlction X
- 4.
- 5.
Sain Steamline Isolation Valve Closures S.
- 7.
Loss of Auxi1iary Power - All Grid Connections iii
Or. G.
. ~Shervood FE Should Nuclear Regulatory Conrnission criteria or regulations change such that our conclusions as to the acceptability of the report are invalidated, General Electric and/or the applicants referencing the topical report will be expected to revise and resubmit their respective documentation or submit justification for the continued effective applicability of the topical report without revision of their respective documentation.
Sincerely, Robert L. Tedesco, Assistant Director for Licensing Division of Licensing
Enclosure:
As Stated V/Vi
SAFETY E/ALUATION FOR ThrE GLE..qAL ELEUCTRIC TOPICAL RE.ORT QUALIFICATION OF T7E OSE-2?-ENSINHAL CORE TRAMSIENT IWDEL FOR BOILING WATTVZ REACMRS nt0-242S4 and KMSlE243,54'4 Vol=-s I, 11 End III Pg.p~amd, By Rvmitr systaw Branch, 051 F. Odar, Lsad (RES)
L. Belt.acchi
- 0. B. Fiano G. M. Hoz IAbui M. H. Mandcnca J. Voseowedo June 158O vii/viii
TABLE OF CONTENTS P=-Ce I.
SU?'ARY OF THE TOPICAL RE.ZORT1....................................
1-i A.
INTRODUCTION 1-SCOPE.
1-2 C.
$UMWARY OF -.N.ALYT---CoAL M ODOEe i-2 I1. STAFF EVALUATION..-
1 A.
REVIEW OF AHALYTICAL DEU.................................
11-2
- 1. Rzcirculation and Control Systam.......................
ii-2
- a.
Rxcirculation Loop Model..........................
11-2
- b.
Control Systm Model............................
11-6 C. Staim Separator Modal.............................
II-9
- d.
Upper Plenum, Vessel Dome and Sulkwator Moda.*..1e........................................
U-12
- 2. S-toml Line Modol.......................................
- 3.
Cz o?
Tinurml Hydr&ulics Model..........................
11-14
- a.
Drift Fi=* Model..................................
11-15
- b.
Mechanistic Boiling Modal.........................
11-L9
- 4. Core Physicz Modal 11-20
- a.
Assumptions in the Neutranics Model...............
11-20
- b.
Derivation of Equations for the One-Group, One-Dimensional, Time-Dependent Neutronic Model..........
2
- c.
CalculatIon of Input Parua2r3s...................11-23 S.
Fuel Heat Transfer Model............................
11-25 S.
St-ary of Code UncartaRintie*s..........................
11-31 a..
MargIn in &CPR Calculations.......................
Ii-1
- b.
Margin in Pressura Calculation....................
1-33
- a. QUALIFICATION OF ThE ODYIICDE............................
11-35
- 1.
Qualific.ation of Neutronicz Model - Comparison of ODYN with BWR Cori Simulator........................
11-35
- 2.
Qualification of Thermal Hydraulic Modal...............
II-3a i
ix
- 1.
SWWIRY OF TOPICAL REPORT A.
IH RODUC ION B-.et=tn April 9, 1577 and April 27, 1977, thmre turbine trip tsts wre perf,1r1ad at the Peach Botto.m, Unit 2, to examine the validity of the General ElectriC transiant analysis mat.hods and verify the cz-put-er c:des.
The fir-t scram signal whicn normally would have been initiated on the position cf the turbine stop valve, was bypassad in order to provids a transient cz-parable in severity tz the wcrot ;ransiants analyad in FSARs.
Using the transient analysis =etho0d and the REDY c*.ut~ar code usad in the licansing application3 at that time-,
General Electric made pr*-'6as't predictions of prnssurv, neutron flux and &.CPR on a best estiwmzt basis.
The neutron flux and &CPR pr'*dictians Qrv signifi-cantly nanconsc-rvativo. and nho PT-s-u1re P'n-lc-tlonS r
kno-he r~'Cz~
Vz%1t Ve.
After tha tasts General Electric performd post-tast predict.ions of pressure, neutron flux and *PR using the actual ar cwazur*d plant par=metars with best estimate modeling ass=ptions as well as the licnsing model assumptions.
The
&CPR amn the neutron flu: predictions weri again nonconservaitiv for both sets of calculations.
The pressurt peaks were pr*die-*d conservatively.
It should be noted that General Electric showed that the predictions of preMsurl and.-CPR wars conservatlve with licansing basis inputs when the first scram signul initlatsd on turbine stop valva position was not bypassed, i.e., under normal conditions.
The c*,arlsons of tha test results aMd the REDY co=*,
the licMnsing basis m=dal, cznfirmed the axist-nts of a sta*s line pressurM wave propagation phentre-enon in a turbine trip translett and tim vzarying naturv of the aial core
The *t*acy stata axial pcwver distribution is calculated by the nautronics modal.
Tha model uses cr-zss section fits Qntained frcm an analysis about cr*'-s sa-.ions for dlfflr-tn r-.itiva ccolant densities and control st.at.s and that ar-, radially averaged for each axial plane.
The fitz a,- such t.hat the axial pcwer in the one dimensicnal wadal is raquir-d t. yi-eld the saze axial behavior as in thc thr-s-diwansional SWR Core Simulat.r solution.
The steady state
.. ar*,l h-,d-auli solution ps*rits tht C31CUlati0 Of the stzaac
.tat AU IU t.mp:rature distribution.
During the transiant, the r-ci-culation and cont,-ol syst.m model c-alculat-s tho tim= derivatives.
At the iend of the time suep, the racirculation and c:om1l systam a l
,upplits the ncw =-tarnal boundary conditions to the rn-ac+ r con Fiz The riamctw cz~rv smodz calaulLa~z tha ntrw ne.utron fluM-,
th07-160- trdrzulic Para-zTis and Naul t~-tr.
It alt-o providoz r~anctor cz-,- exit quzlltyj, flow and przssura as input to th. rcirculation and contrzl systia motel.
The reirculation and cornt-ol syst'a model calculates 'the lop pressurz drop and the ra*ctmr czre modal clculates the core preszurs drop.
Those prnsura d.rps a 4-0 el ai-d.
If thay are not equal within a czrtain limit, the rtcirculation and can-trol systs, =del derivatives are modiflad and the time step calculations are npeate-d.
Tha rtcircullation sy.stem is modeled by solving the mass, energy and mownc m
cznsa.ciation equations for the staa' line, reactor vessel and recirculation lzcp
=*zone.nts which ifmludad jet pumps, recirculation pumps and associated piping.
Tae control syst.e is modoled as a series of connecud gains, filters, 1-3 Xiii
n-ju~t,-n groups ara usid.
Decay heat is woda21ad using a Siple Ex;onential dicly heat sod4l.
Tha onQt dimensional neu-tricn diff'usion paraiitars art obtained by collapsing the parwattars at-tained frcm the G-E thrt-s-i mans Iona 1 8WR Cora Simnulator (Referencz 2).
- 2.
A single active heat.d channel r2pr~sant.5 VU cone average conditions and another single clisznnel reprasants the ccru-bypass.
A five equ~ation modal re-prssenting aass and mrner-%' cznsarvation for thei liquid an~d vapor, and the mix(ti.ra mcmeztu consarvation ara used tc calculata-core t4hermal-hydraulic behavior.
- 3.
Hcat transfars U the@ azdoratar and tual t.vaparat~uras arg calculate~d usi~ng an average fuel and cladding model at each axial location of thie ccre.
Tha gan cwwnl i z an input p.arzl-t.O ti iICh P-ay VE =' e~axlZIY in t1mz.
T1he cnduatidri pavaimt.-ne saw-4 tetper-tur-dapendsnt.
A radially unifom' (flat) pcwar distribution is assumed In the fuel rods.
.c-/vi
- 11.
STAFF EEVALUA-t1OH The stua*11 evaluattion waz parfomead in threa-par=s A.
Rayiewv of the anialytical modzls in the ODYNf code and dataminati-n of uncaruianitias in tlhe czda modeling.
S.
Review of the qualification of thm code.
This ;art oll the raviefw is acocwplishad in thr-9 ar,-as:
- 1.
Ccmpariscm of specific kodals in the code with saparalts affacts t~zst data.
- 2.
C~pariscn, of irnta~pal respcnsam of Wthe codt with teintvegrzl tar.-
cdata.
- 3.
Cv~zrisoan of tho rcod8 pru~ctions-with tha pndictions of zui l ntdapadnt code; 1.21.t.
audi t cal cul ati ons.
C2.
V i~
fraOf th 0 1z2 f~t PaVY2-!re" I ni.
- e.
OvPIUrt10na-t, e'auto an PJ3i oz-irl ;,, 'a&n T1 erx cd C is usaid -I.~1t tLhe uncnrtaintizz assign~ed in tho licansing basis trans-ient.
The Lncrtaintlas of the calculations war-- 2valuatod a3 pant of the cal cul atioanal modal riview.
The amesur-a of all ezda uncert~ainties is aado in terms of.&.PVICPR ratio.
The "CPR" is an acort" for c'ritic~al powir ratio.
It is the ratio of the critical powar of 1the limfitng bundla in the carm to the power of the same bundle at the operating~ pcwmr of izflayast.
The critical power is an artificial bundle pcwar obtained by increasiNg the power analytically until the critical quality i3 reacned.
The aaalysis is paro iaz ezing the GV(L correlition.
Sincs the hydraulic an~d neiutronic psrawntars change during the transient, CPR also changas during the transient.
Thu minioiz value of the CPR is called MCR and NI-1 xVii
Rallarence 1 En has been roi~dand appnroved" by ?IRC (Reft-,enci4)
The other inputs used by th* recir-ulation 5ySte Mcodal ar-a plant specific such as dimensions r2latad to plan; geomeetry, prtsure loss coefficients, separztzr car*yjunder fracticn and jet p=p and rdcir-culation pump charataristics.
In the initial s-*ady sz*-v c:nditions Vhi jat punp drive and suction flows can be detarmined fr=e the 2quation of czntinuity anc the jet p.p "a.' ratio.
Tinis ratio is Wfined as the ratio oif the suction to tha drive flow.
lt is valid fo*r the ratad cnnditions which ar2 select-d *O cr--aspoind tz. -2t6dy stata initial operating cznditions.
Using tho*
w c-ntm equatian and the "o" rmtl, th, suction flcw and tho oc-*icn flew lots.mcfficient &n 62-t in,.
During tho t-25ont V13i rtIMo ch-IVGs3.
Thi, jot pt Suctio oan~rd dri vc fi c-t-ý (consaquently racircul-ation loop and czta Inlet flows) art calculated using the m==ntum equations ka-ping the suction flow lo-coef-ficio*t constant.
The s= of the suctlon and drive flows provide the riirculatoin loop flew and tht sum of all recirculation loop flows provide the cr-a inlet flow.
The racIrc~ulatlon systam azdals used In the ONYN and MY codes art the same.
The R!DY code (Referenca 5) has been r2vieved for ATWS analyses and tb.a rtcirculatlon systm model has been found *cceptable 2ith s5=0 lisitations (Referince 6).
Tho follctving discusses and evaluatas ths recirculation systia modsl.
This evaluation, except" for ths unczrtainties, is the samn bzth for 00DY and REDY codes.
The 11-3
co-2 flows for the transient.
This shows that t42 meent÷ equations "rn solved correcly to prndict flow transients.
Recirculation pump trip tasts3 werv also perfor7-d in Dr*s*arr2 and they were ro orted in Rafar-anc
-.A Howevvr, in these t-astz zasursd czrv flows wer higher thmn those calculatad because the acR.ual purp Inertia was higher thnan the value used in the analysis.
One of the jet p~p =deling au a=mtions is that thý region from the nczzla to the throat is considerad tz have no inmr-tia.
In ordar to validat. the transient 2=daling of the jet pup, transient j*t pue ttsts wnere c:nduC-.: at t~h
- -oss LwUding Gonerszing facility, Refa-cnet S.
In t~heze tnistz the~ jzt pum drivez flaw2 werz oscillatedi at Sveoe fr-cqu~nale a~ nd P.aesur-aznts Sadn
~i~
of th'ý gni n rin4 pF1 c i.....
r.-..,nsIip of ths dr*tve "lOm.
C.pa*'Iscn 0f1
,.o and =~del prtdictions showed good ag'remant up to 5 HM. Tihe modal did not przdict a -zrnanc2 condition in the cold tast data at 6.5 Hz; consequently, tha use of the m=del is limited to 5 Hz.
Tihis limitation arans that the code will have errors if ruclrculatien loop flow variations are sudden.
The harmonic cocpcnents of the flow variation should be lass than 5 Hz.
Another assu,*tion which has betn validated by tests is the azs=&tIon of c_-zPlSt nixing at the ccre inlet.
Tests wore performed in Hanticallo to verity this assuaption.
Cora flow distributions for thrat cors flow rates, at 2r.4, 50% and 85% of rated flai rates, war* m.asur-d for syitric opor2ZlOn o" th6e rcir=u-latIon pumps, Rafurznca 7.
Tests results Indicate that the bundle fleow rats does not vaery =or2 than 2.1% frc= that in the average II1'5
- model, thie faetwatar czntro.l mcdl and the p,-ssure rz.ulation wii:,
the MWenhanical Hydraulic Czntrrol.
We find the str-icture of those medals accaptable azr typical of the type of modeling conductad with claszical control syztea threo~r.
With r-asre*a-to the dascription of the control models, *te following models wer-evaluatad:
(a)
Valve Flew Czntrzl Systam (b)
Mcutr-Generat.or Flow Cont:ol (c)
Fe*edwatar, Flow (d)
Pf-assur*R*Uglz.r and Twrbina CUntrols (a) RaCCoU safifty Syst~ms For inptrt flg-Aals, the Valve Flow Cntiol iffoel rMca~ivos a tu.,bire governor signal, a sensed sta-azflcw signal, a filtared neutron flux signal, a recir-culaticn drive flow signal and a manual seatoint signal.
The control systam is modeled as a series of connec-ed gains, filtars, intagrator:,
and nonlinearities (limitars and function gtnerators).
The czntrzl systas output is valve position and thus flow contrl.
For input signals, the Motor-Generator Flow Control model receives a load drmand error, a astar manual or autozatic signal as well as a loop manuzl or autwoatic signal.
Tho conro,.'rl systm is Oodaled &3 a saries of gains, intagraurs, function generators, and with ac.uatzrs of a drive =oter, variable speed coupler, generalto?, and motor pt*.
The controlled variable is ricimulation drive flow.
11-7 diii
- c. St-sam Sezarator Model Ths separatzor is zocdeltd using a one di~ensional -moment=m cnnsera?-iacn equation viartas the flow in a separatcr is rotatianal and clarly multi-dimensional.
However, using srnparat-or test rasults CRaer-ancz 8), it was possible for GUneral Electric to develop an arpi-lical onm dimsnsional m
~nt equation dascribing the flow behaviocr.
Tas-%Z nI dczta~d t.at 6tho thickness and cznflguration of Wis layer of swiiiring water along saparatzr walls is indapencent of' the inlet flow (for 200,000 lb/hr < Flow < 800,000 lb/hr) bet.
dapenean't on ttme inlet quality.
The watar layvr primarily affez-.5 t~ht saf1ctlva L/A In the mczen= aquation of t-he sapar-atzr.
Due tz diffpw-'2n.-az bartgan tho donsities of stanm and wat~ar, th32 piiary inartial effsct3 arz divn to th, Iliquid.
Thea test-s of Rafe".-c3.2 rj,-~jdzda r71a~latohip betiucn the afft-tiva L/A and t~he inlet quality, and an eiclsntr.rsu drop coefficient.
General Eloctric stateas tthat ths value of prassure dr-.p czefficient.
rhas a cznztrvative bias in it.
Tha higher th~a prtzsurz drvp or the pi-essurs drop czafficient11, the higher is the value of ACPR/7CPR.
Hmmvevr, Gararal Eleczric. did not. quantify t~ha cnservztism in this zodtl in terms of L.CPV.ICPR n-lative to ac-tual plant czndithions.
Therefom-,
nio crtedlt is given tz this cznsei-vatizz.
G-aeal Elkrtrlc peroiaed sansitivity studite deamsin-; the~ 'alua oY L/A *y 30%.
This reasulted in an increasn of G-002 in LCR/ICFR:
In Crdmr tz assess if the scatter of 30% in the saparatzr L/A is suifficient, the st~aff reviewed the sa~zrfltar data in Raefrna= S.
I*1-9
"agion preadi~cs that the bulk wat-ar mass very quickly becomes subczoled, the system becomes stiff, and therefore, the pressure rises v*,-y quickly.
Since the rapid pressure rise leads to a rapid void collapse the staff concludes that the model is conservative.
However, the Peach Bottom tests also indicate that L.C?R predictions are not consaerative.
This implies that th-conservatism of the bulk water m=dal is offset by the noncznservatism somewhere else.
General Electric did not quantify the conseriatism in this part.icular model.
In view of Peach Bottom tests wher-a trade off has oc:qrred, no c.vdit for cznservatism can be given.
Wa find that the analytical othcds used in these models are ac.2pt.blz; rvvr, as stated, no cr-ndit for cwrvatism will be gi vcn.
- 2.
Steam Line M4edal The steam line is modeled assuming single phase mass and energy conservation equations which are solved using an explicit finite dif-fartncing =thcd.
The steam is assumed to behave isentropically.
The s5tam line is nodalizad int*
six segments while the bypass line is modelad using tro nodes.
Safety and relief valve flow rates ar2 treated as separate flcw branches.
Sensitivity studies wars performed by General Electric for various nu=erz of nodas for a samle test problem whertin the inlet pressure is kept cons'ant and at the cutlet turtine stop valve closura is simulated.
These sensitivity studies wer2 performed using nodal arrangements of 3,4,5,6,7,
!I-1_!
M.xvii
stiuam Ilina, "e do not expect scaam to ba superhe-at~ad.
Hanct, tha value of 1.15 is ac:zpta..ble.
We also find the calculation of uncartainty of 0.01 in &CP?/!ICPR ratio acepta.*le.
General Electric also perfrmed a sansitivity study by decreasing the loss czefficitnt by ZC%.
This was based on tha upper limit of st--amline los3 cUaiflcian'. unc'2.lin-.Y.
UeCr7i35ng the loss coafficient b Z* inCZ
-asas ths ratio of %CPR/ICPR by 0.01.
Dc-aasing the lo*ss coefficin't by 2M is a riasonabl assumtion and we find the calculation of unctrtz.inty of 0.01 in CP.*/!CPR9 due t. pr7szur2 loss caefficiants ac:zpt.able.
In cvnclusion, out r2vietd indicates that the analytical ril thod useld in zta2n line E.cdaling sind msec~ci-atd uic wlantiess areO acp4'able.
- 3. ro Therimal-Hvdraulicz Me4dal TAo-phasz mazU, aner-& an:d momentuz conservation equations war used t.
predict the behavior of the thermal--hydraulica of the czr-.
Two mass and t*o sner., cznsarvation aSustions rpreasenting each phase separately and ona 3etentum equation rapr-asanting the mixture comprised tha five equation m=ctl.
In addition to thess equations, calrrelations for 1) interfacial hmat flu=,
- 2) Z'ubor drift flux mcdal (Rzference 9), 3) ti;o-phasa pr*ssur-e drop, and 4) heat tranaofar, are used.
noIm
.inerfcial h-eaz trwifea czmrlation is brzc-d on tho u"mahnistic md*l1" presented in Referance 9.
The sal.ion oYf the heat transfer correlaticns is based an the floe regizes.
In the slngle-phase liquid region, the Oittus-loolt-Ar czrTt-lation is used. In the subkcoled and bulk 11-13 MdXi2
deentencs has batn shcwr2 in many tests (Raftei-nce 9).
The crI ft Yslocity is co~apr 64ant on the2 density differutncz bet-ve-n the phiases as well as on the flow~ regime$.
in the =cdzl used by Ganeral Electric, these parametars &-.a empirically datarzirned in the form of ezrrelations based on the test
'The cata were ozz-alned toth '"ca t~es and cnannels, and are r~pcnad in Rafeearnces3 10 tnrzugn 14.
When the vapor frzctions ob-tz-ind fren thesa parant~ars wzri used tz czalculaua pcver snapes obser7Vtd in E1ARs, soe discrepancies tior2 obzarwad.
Cons equentl y, Ganeral Electi1c 1nt-.-duczi anothar oorrelation for Co and a czncapt of neutrzn effectiva void fraction, tz provida a battsr fit wuith
.- ni~unaptrcrzh?
zpas.
E-rz;2d on PfrysiaIcoinCsid ti Ons It Is
=ttvý:le thcC u.din "il tiydaulic Is~in~j diffafint fr-co C0 fzr nautron pzower calculations.
The thremaI hydraulic C0a is based an tube geezetry wbile noutron effective C 0 is ottaincd frc actual czre geometri.
Tha value of C0a should be dilffersnt for tubas and rzd bundles because of differint vapcr fraction profilles and flow *reimei. However, in a talecozn General Electric s-tated t~hat C0a valid for thermal hydraulics gave good agreement with Atla~s dtaz and C avalid for neutron tffactive void frzcttion Save good agraemnt, with the czrt data.
Hancs, the difftrinces cannot be wqlained based on geomtrical considere-tionz alone and there is an artificial fl;% in the modal.
Ac-cording tz Refzrancs 34, this fix I$ necB2sary to czzpansata for deficiencies in lat-,ic* Phyics Mth;Od2.
xyczi
Ass='ing the sa-me uncirtinty for W1e neutron affacbiv C and itrazolating the General Elact.ic results, wa have astim*isd th=at the uncartainty of 2:
ZZ in C0 t-Sulting in 1 33% unC37-6in:y in t!e void fraction or in the void reactivity coefficiant would produce an uncirt.ainty 0 :t 0.0=3 in !CPVICR.
We prtsentad these findings in the ACS hlaring, Rayerenca 30.
in responsa et the above staff assissman:, General Elaco.;ic suzmi:-ad additional infrrfution, Riaf 2nca 31, rrequasting tha raduction of tie unczrtainty in CPR ICPR.
The primary argument was that thas untzr C"y f
c
- 2% in the value of C0 (seven timas the un:.r-.ainty of t Z_ tnhih had bmen propos.d by Geneiral Electric) Iesding to r*a ur.4tMrirrty oY Prp nimiatzly
- 31M in vt1d fr*ction was, M-plic-ble for a lr, qality aw a lu-vpar fracwton r-4ion.
Ths un*ar.;,rty becozas s.-allsr at higner qualitics.
In addition, General E*ectric sut.ittad another sansitivity study using. nautron effective C0 1.0 and not.d that this wculd ba the bounding value for ACR calculations.
General Electric also natad that the trznzient results wera takly dependent on void fractions at low qualitits in the subcooled region, Raferinc 32.
r-uviawad the nsw information sutmit-ad in R*Y rencz 21, and agre with General Ele-tric that unctrtainties in vapor fraction can be rdcu-
- iat higher qualities and that Co a 1.0 is a btunding valum for bulk bcilirn.
General Electric statad an uncert.ainty of t SEX in void reactivity czafficient at a void frzction of 70;.
This cr'tosponds p:roJsiat-sly to an unctrtainty of
- E% in void fraction.
Fur.ther 11-17
.7=iii
The zodel has been Yerified using the data obtained by S. Z. Rourani (R*eerincas 17 and IS).
These data wer-a obtained fr-o a vertica1 annular channel.
In at.r=.ining the uncar.ainty as' the car-, alation, General Electric pr-vided a sensitivity -study using a coefficient "n" in ths ccr-ialation.
The nominal value of "n' is 1.0.
For n-- 1.25, a change of 0.009 in &CPR/ICPR is obtained.
If 1.50 is azs=2d, tne c.ange in i.CPR/ICFR is 0.014.
GE states that the value of 1.25 provid23 a reasonable uncr.tainty for the m=del but does not provide any supporling evida=nc or da*ta.
We ruviewed the void fraction vs.
Wxial height curves dranm for variaus In" valuez anr find that the void fraction diffarence betran the t-curvwn 1?e1',n for n =.0 and n 0 1.5 in about 3.L in absolu-a o; IN rLative to thQ av rj.-e a'urod valu= Of the vo.id fraction in thek subczelad region.
Scam af the rod bur.dle exerimantz perloraed in the Frlgg lcp (Refer2nca 163 show 1013 (relative) scatter of the data.
in general, the scattar is 15 - 30% relative to tha averaga void fraction.
We believe : 3= sat-tar is a reasonacle estimats of uncert*.lnty.
Therefor2, we increased the uncertairty in
&CPR by a factzr of 1.67 (30/U.)
which results in t 0.023 in the uncertainty value of ACPR/ICPR for the subczoled boiling m=del.
We estimate the crmrvsponding minimue &nM maximum values of "n, to be 0.5 and 2.0 rps-ectivaly.
General Elictive is nquired tz make seanitivity studies to vrify that thesa values Cormsapcnd to : 0.023 unc2rtainty in &CPRIICPR.
¶/
Appendi% A of Vol~e 1 of 6-ha report.
This derivaticn pr-ce-ds from the tiae-damendent form of the thr*a-dimensional neutrnn diffu-ion equation for the fast ?lu" as used by the General Electric three-dimensional rsac-.r si*ulatzr (Refer-nca 2) along witn appropria:a equations for delayed neutrons.
The thr.se-dimensioanal time-depencan:
neutron flu= is reprt-sentad as a produe. of radial and axial time-dependgnt C=qponents.
Weighting functions amr naxt in-.-adu.ad to make this fact.orization unique and tz minimiza errors in the przcadur-in same sense.
The xeighting functions ar2 ta,.sn, sc:ording to ths adiabatic apprzximaticn, as the solution tz a ste-ady-stats eigenvalue pro-blem to ;e solved at. vario-us points in ti =.
In pin-act*c*
, the wmighting functions &Fre clculatad only at tim zz?:i ftr as etn DI crciwating statzs P-s Is nc-s2sEary.
This prr~reur-a ;,zzu1 ts in tho final alorta wo~d fors th* cna ronp, oru-~
dimensional, time-deendent equations along with defining equaticns for t:ha nuclaar par*m*trs that are usad.
The derivation also incluoes discussion of the average axial p;ewr distributions, initial normalization przcadures, and boundary cnditions.
Section 5 of Volume I of the report discusses the Integration of the spatial and tim variables to obtain the discra.s form of the one-grzup, one.-dimnsiaonal, tim.-dependent equations.
The procadurss used for this are straight forward.
This saction also discusses the radial woighting function and the treatmznt of the control state.
Cross saction ralated parametars ara functions of axial core heighi, contrzl state, and relative watar density.
Thozs paramt.ers are fit to quadr.tic' in the relative watar density.
'Ion*
xcvii
Our rnvi:aw of -.he calculazion of naut-mcnic input paramete-rs is based on th2 usa of NRC ravis*ed and apprzvved czaes and on cnmparisons of thrme-dimensional and ODYN st*ady-statz neutrnic analysas.
T-ne 4-proved ccdes are (1) the LattiC2 Physics MWal (NEDE-20913-P, "L.attica Physics Mathods," C. L. Martin, June 1976 and NED0-209.9, "Littica Physics Methods Verification," C. L. Martin, June 1976) and (2) the EWR C*,-a. Simula÷.r (1400-20953,
'Thr.--s-Oimans.icnal EVR Czr2 Slulator," J. A. Woolley, May 1576 and NEDO-2094-6, "BWR Simulat.r Metheds Verificztion," G. R. Park-s, May 1..76).
The steady-state calculaticns czaparid the SWR Core Simulat.r and ODYN result-for 3---,
raactivity and core averaged axial poer distributio~n,
=q-ng other things, for a nu*wi of differant rta-rzr and optraing Sc= of tho uncart-inty values used by General Electric in nspcnse to our Quest*on 12 nee*d to t r2via-d in our. judgebent.
WA believe that the Dopplar reactivity coefficient uncertainty should be increased fr= : 6 parcant to about
- 20 percant.
This increase is bastd an tho uncartainties inherint in the calculation of Uraniu-238 rasonanca absorption, the calculation of the Dancoff factor in t.he czcple. BwR lattics, the calculation of spatial weighting fact.rs, and the co:
z*ration of effective fuel tamperaturts.
This change in tho Doppldr uncertainty will have very little efftt= an the C=lcu-lataid L.CPRIICPR ratio.
We estimata that this will inci-aase tha un-artainty in &CPR/ICPR frog k 0.0015 to _ 0.002.
We believe that th scram reactivity u-n.rtainty shuld be increasnd frtcr t 4 parcint to aboe, :t 10 percant.
This incrusas is basad an tha uncart~aintles 11-23
The fuel and cladding conductivity and heat capacity aN assumed to be t:empratur'-
dependant.
A gap thickness is specified bat.-4n the fuel and the cladding and an input gap cmnductanca is used.
Axial and time variations in t.*s gap ccnduct.*2ni £y be given, but a cznst.nt vluse Is Lued for safety analyses.
The axtarnal heat tr.nsf_=r coefficient and czclant t==por2tur amn-cbtainad irom the theirmal-hydraulic portion of the code.
The heat gener-tion rzt.- in the fuel ;ellat is obtained from :he axial pzwer distribution which is det-rmined by the neutronics sepent of ODYN.
The raclial heat di3tributien in the fuel rod is assuzed tz be indapen-dnt of axial position and ihdapendent of tima.
Gmal Electric darivod the fuel h-it trans'pr mdal fr-am the gentiral 113t. f1w *:qua o~~tn. 7h.3 eqatin Iz t ifth zxis i.t7rai end axiall =nduaica auZzSV=d.
Tho ro-s~ulting, cr.lo-inozivnal, t6rzn~zivnt jo; t conduzction o-Quation is solved by the Crank-Micholizn finite-diffanrncz tachniqua.
Th3 -.zlution is pproximm*.t, but the prv:c.dure is widely prazrtia and is v7ll dacumne*ed In the open litarztura.
General El*=tric has limited its dzscription of the fuel hait. transfar modal to the for=ulation of this final aquation.
The msultin haat' cnduction equation is applled tz a single rod with a radially averaged hoat generation rate.
This red is used tz raprtsant all of the fuel rods in the reactor czro.
Becau-u axial conduction is assimad
- t. b* negligible, the &AuatIon can be solved independently" for each dicr.eata axial position in the cra.
The finita-dlffarnnce tUchnique also r-;uins a radial nodalization of the fual rod.
The nodes may ba of
.t itrav-iy size.
C-en.3ral Elm-ctric has assuaod that the fuel pellet is xli
Both of thase liziting assumptions wers considered In cur 1-avtL-of t"e gap onductanc2 values used by the ODYN code.
We havQ rvieed (Refearnce Z2) the saeczlon of the axial and time variation of gap conu*rtanca
- -o determine wh.ther the salectad values are appr=.priate for diffarent transient.s.
Geaneral Ele.-tric statad thaz the ccre. avtrags gap c:nductanca values arm calcuiat-a by GUSAP-IIi (Refere2ce 20) which is
- provad by HRC.
Ths calculatsd conduc.ainic is input for all a.ial nocas and is kapt c:nstant during the transient.
A sansitivity sudy was also parformad for the most limiting pr-assurizaticn event In wic:h tha ACFR dacr*e*azis hen =ial varying gap couc-t--c is used.
It bas zhcwn that twst of tha high pcw-r axial nodas h.MVI ihiglf~ 'hcir2 CnO?'
MIZMv rQ
- ~~oanp During 16'ho twrnsiiit, h ghr n czidu.a-nca t.111l 1-d U. fzzt27 Matt tr'ncfar fi'-cm t&o 'Fuzl tz the modor/coolan-t which ganeratas more stoat voids.
This results in lower -*,-md heat in the higher pawr ncdes.
In addition, the fastar converslin of fual u.red anery to staim voids in the core helps to mitigats the translent due to negative void reactivity fIeedbac:.
There-form, the transient with ax varying gap conductlance is less severt than that with constant gap cnnductanct.
During limiting pressurization transiants, it is exected that tha fuel gap cnuditanc2 will be higher th*n its Initial stsadystat value due to the Increa:j.io in the tharal axpannion of the fuel pellet.
As discussad about, higher ga; cznductance leads to a less Sava"s transient.
General Elsaclri ha-n*t taken cra-dit fa? this fact, beft has stated that tha us2 of conStarnt CondUc,.a=* throZughZu th, T1 anianet. =o*lpensates for uncar-II-V7 x1iii
radial 1-dePvndent heat generation rate is ex;ectsd in EWR fuels.
General Electric has acknowladged that t:he radial power distribution within the fuwi rod is not Lrniform.
Thiz is bczaus4 the plutcniLn build-up and salf-shielding of the fuel results in a radial pc-wer shape peaked.h,.,iy at the outsida of the fuel pellet.
Heat transfer from the inside of the pellat tz the cladding cc:urs by diffusion through the fuel matzrial.
When ths pcoar is pea.kal at the outide of the pellet, tha aver.ge dist*nce frgm the area a-1 *e.imum hzat generation tz the vdge of the pellet is less.
This result. in a short.er time constant than in the uniform pzwar production c*-a.
A riduction in the thermal ti=e c:nstant results In fastar feadbac.! of hcat fl=x to the =drz rtzr/coclaI nt and rtduces the eonszquencsz of the pi-assurizztion translent in t.h1 szza f1-Cnrth'at highor g c~nupa~
dzsg.
Mois a u~1niom' potnor dis-ccd~tertr/coal ant stancoi nt.
Although the usa of a unifori ratial ;in power distribution and small gap conductancz values lezad to cnmrservative sodarzt=r/czolant conditions, these assu=ptions also lead t= higher fuel t.,erzturas.
The higher fuel tperaturss, In turn, lead to Incrvasod Doppler broadening in the fuel pin w'hich is non-conservative for transient analysis.
The OOYN czde assas that all fuel at tho sme axial location In the czr2 has the sa*a t*mperature przfile.
Analyses have shown that this apprtach may t-nd tz undartatimate the Dopplgr naictivlty effacts because the fuel pins wnich have the gnatest resonanc:
capture rates are near the bundle periphary and c;erazt at hlgher avanrge tampartur-thin thzt calculated by the coda.
This ass*m*1ion Is valid only for fual asstoblias with uniform 11-29
%[v
conclude, t r
til the ODYN fual heat :. ansffr readel is a1p.-priat.2 fo? tha safstY analysis of these evnts.
Su,.nar-of Code Uncer"tainties
- a.
Margin in iCPR Calculations In su-ay,,ha stff? agrais with some of tihe code uncemainties c.lculatt.*d by General Electric. Hcaisver, some of the code unc.rtaintie.s ara lowi and tht s-.a1? riczmends higher values.
A czmcarison of the codea uncrtzinties and the corr-a.panding bounding values as r-czmmendad by Gencral Electric and the staff is pr-asantad in Table I.
Gasrtral Elrtric claims zn apac*td conszrvativa bias of 0.02 (Table 3-3, Vol,*
FI.1) in tha czlculaticn of the valu.a of ACPR/ZCPR dua tQ tho prftrme.d using dlffergnt values of gap conductancs (Q-'1, VoMlUM iI) as -xell as the c.p-ariszn of the Peach Sot==o test data wlith the ODDYN pradictions do not Indicata that such a conservatism in
&CPCR calculations
.iistz.
CUnsaquarmly, wv do not believe that the pri-tlctions have a consei-vativs bias.
Our rmvew shows that the ODYN code is a best estimate code and there is no inherent cznsarvatt3a in predictions of ACPVL/ICPR when best astimatma iriptt values art used. Consequcntly, we do not give credit for this elatlad cznsorvatism of 0.02.
General Eltctuic estlate the tfotal ciod uncarti.inty (Table 3-3, Valuma III) uzing the Pethod of linearization.
This mathod can 11-32 xlvii
estimate the autput distribution only approzimataly.
The methoo also issumas the indepandenca of the paraeteres.
The appropriateness of the linear method should be verified by r*ssponze surfaca and Monte Carlo analyses.
Hewever, as will b.* shown subsequently, the results of the st.atistical analyses prforir*ed in Volume IIl are not ac:apu.ble.
mew statistical analyses, if parforsed by Ganeral Electric, should be ba.ad on ccde uncxtz.lntis, basid on c:zparison of c:de praedi=ticns with t-.
tas-. dat-a.
ConsequEntly, we use the valut of total czct unc:mrtzinty calculazad Ircta mo=dl so-nsitivity studleo and mt=v, of linearlzaticn In det.rmining tha margin of &.CPR/ICFR in Option A (to ba prc* n'd in Staff Position) whorm statistical analysis is not ra.quirvd.
Tho totzl cada unce~a~naiy in Teble 3-3 of Violuza Ill zz pr.r C-znerzl Electric Is +/- 0.031.
azased on our r nvle wa Inc*eaz this valun t. +/- O.&44.
- b.
Martin In Pe3surv Calculations Genarml Electric has nit performod analyses to det.rmine the uncrtaintias in the calculation of pressur*.
Hence, It will be netrciszary for General Electric to perform thes-a calculations using staff reco=eanded values of the parameters listed in Table I for the Main Steam Isolztion Valve closure event.
We believe that thers is sufficient cznser/atism in the ASME vessal everpmrszure limit to permit General Eletcric to use zepi-ximats linear methods to daetrmine the uncs*tainty in the outpux.
This uncan-ainty (2a) should be add-d to tha 00Y1i calcultted prssurv.
If Geanral Electric damonstratas that, this uncertainty is veu=Y small (e.g.,
by a factor of 10 or =n) rlative to tha uncert.invy In deitarmining ASW vessel ovarpr2szure limlt, no addition of uncartzin:y to the Calculations of pressurl is n~edad.
xlix
Tho EWR Con Simulatc.r calculation of t*he criticality of first cycle and' reload BWR-results in a small bias which is taken intz ac:ount for raazivity dat2rmina:ions of cold, Aacn-frzt and hot operating condi-tions.
The
,tandard deviation of thesa criticality c-alculations is anout 0.002 in unitz of rsac-ivity.
,ha quentities tz be cO-1itar*d Tir the cora avsramged a-xial po-tr sfnape, tho scra-m r-activity, znd t;a void reactivity cnefficisnt.
Thesa neutronic paramazars we.-
salectad for c:pariscn becausa of their importancs in tMn turoina trip without bypass licansing basis transiant.
In addition, it is the
-paca tlme evaluation of thesa A
,uantities that. distinguishe. tha ODYN calculittIon fr=o a poirnt kinetics ovaluation of preszurl::ticn type The campariscn 4-1 tho czra ayergagd axial p~owar distribution, as coispuzad by tho BSUR Care Simulator and OCYN, is given by the.asponsa by GE to our qusstio 3'.
This rzzponse statas that the collapsing sch employed in the Senerztion of nuclaar parzatzete ensureas that the stzady-s~tat core averaged Wial pCOwr distributi.n and criticality comzpsud by ODYN arn identical tz the SWR Care Simulatzr result...
The response also Indicats tt, for a nmer of plant and oparating statas, The OY eor'a avre-agad axial power distribution agreed to within 0.5 percent of the rzsults c.tained with the thrtc-dimenstonal BM Cor Simulator.
The scraim rea ctivity was cflpared for thrfc Et-4 reactor operating statts. Tlic initial scram rztz (ISR), defined as the scram reactivity insertion rata during the firsit. second frceu the tine scram is initlatad, ii
Our rivie-i al the cr= arison of staidy-.tatp*a
.WRs calculated using tht on,2-dimansional ODYN code with c=lparable calculations using tha thr-ae-dimn~ional BWR Cors Simulator c:da has been perfor%,d (1) by reviewing GE results for the scram-rus-ivity and void rzactivity c*efficients and (2) by raviewIng the GE rasponsa to our raquest for additional infcization on staahr-st.at.
c.=pariscnz bat-aen the t,'
codes.
We concluda, based on our review, thaz staay-o.atit ODYM code calculation CY co"- avera~ged a.zial pcwer distributions, scram reactivity, and void rctiviity coafflcients ars either irrgccd agnw-int with or consearv-tively calculatad wi*th blspaiz ta craerabla staaadv-Itat resultz ott-Mined w~ith tht PURI Coei@ Slixrlator eoda.
- 2. is~iflefotion of tti he '
Hy-riv'flic M1tdel S*vzr1l
.=c ariszns of tha ODY(N therml hydraulic model to standard GE dzsign =mdls we per'*fr*d.
The standard GE design modal was subeittad in R.ferwcne 1 and was qcprcvsd by HRE in Rzferenca 4.
Both stmeay state and trznsient conditions wre anlyzi-d.
TIh steady stat. analysis first =zpared the thormal hydraulic character-istics (void fraction vs. axIal location) of two typicil EWR fual channels (higth and lom* pasr channel).
Tha results of this comparison show good agteesnt biemtw the rodasl.
This was eo--.pod sinca both models are veriy 3imilar.
The gk=xoim vzid fraction variation between the-sa azdls 4as a:proximataly !
for the high paver channel and about M for the low pzwzr channel.
These variations ara for tho agial locations whozre tho void rtactivity change is a-Petzd to be Most significant for iio37 liii
GOualification U-ing Intacral Tests In the past several years General Electric has undar-aksn a ta-st program to verity the analytical methods for reat.4r pressurization ransiants.
Tbe tasts of major interest f.or the rurrr*t discussion consist of four turbine trip experisent*.
Three of these tests were perforied a: Peach Bottom Unit 2 (PB-Z) in April 1577 and the rwaining ta.st was perfo~rmed a't a foreign reactor (KX2M) in June 15777.
ihese tasts prmvida the experi-mental dat.a base for verification of the ODYN code.
the test results will be sizrized in this section.
A detailed desr, iption of the PS-2 test is pneserrnd in Referenc.
22.
General E1ectric statad thwat ODYNI has ben davalop.ad fa Y first principlas ar~
I ~eiiin~.~Df 6"11oss roul ts.
Thu st-ty' azta9 thzt i n th--- ODYM e"'$a Th. ony z~inrificial *Fi., is tto ntrftm 0Ief'c-tivo void illrin hzý cczpari.ons -1ith int.gral plint tests przvide an independent check of the OOYN co4e.
The evaluation c~oncantrat.2s on the differ-ncas batwen tasst..
results and czr'sponding ODYH predictions.
The pramaters which are considerd In these cooparis:ns are steanline pressure, nactor vessel dcme pressure, carn exit prassura, and transient neutron flu;: dist-,i-bution.
These paramtars an of prlma*y iportanca in simulaticn of the prtssurization tr*nsient.
An a& rta, ODYN simulation of these pzram-at-ars would provide some verification of the assumptions for the transient models.
- a.
Peach Botom T-sts The inpri'.3 usad for this cocmzarison were best eztimata or measurnd values for the curewnt (April 1577) Peach Bottom Unit 2 EC2 condi-tions.
The thra-Peach Bott= Unit 2 (PQ-2) tastj ware conduc".d at IU-39 lv
A -.zoi~zriscn of Otha t.~tal cort pvtýor at. a function of tiza, proviass an in*-gral test of the iacrc-ant rt-acivity ?aedba:k due to scram znd =4darat.r donsity changes.
This c:xparison would also be in-dicativt of the adequa-y of the czra pr-assurs. and inlet flow calcula:ions.
The cc*arison shows that OOYN pr-adi=. the initial and fall-cff part of the turbini trip. transientz corracly but odvtep1rdltz the peak to.tal corea Ocvar 7-sponsa for all ufras tass..
It,hould ba natad that the calculatad cznsaquncas of the turbina trip t*stz ars sensitiva to scram delay time and the power fraction for pr-zot *daratr*
heating.
I1 should also be ncted that small changels in reactor opýeritin-stata cznditicns suct as, for exarnplz, cnmo prazsure, cause rlatively large changes in tho flux trran-ie*.t Mas)of t~hý harh@o, n,,-t v01.Siyo ha.:n:ir The recti-vity czmtponant displayzd for these 0711N calvilations sh w that wihen sc-.m oc:urs the pawar bur--t is quickly quenched.
This is due to the czntrnl rzd distribution and frzction for 9*a-h test.
The Ocppler roactivity co=cnant play: only a s*.ondzry role.
Tha" raactivity c=cn*n* again d2-:natrats the necassity for their ac=urate asa:=33Mnt In any calculations of those typt of Itransients.
A further indication of tho adequacy of the ODYN calculation can be ascertained by czzparing the =2re power as a function of tim at the Lacal Powar Range Pwoitor (LPfi) datectnr positions.
The miniatu-u fission detacors that coaprise this LORN systaa are distributed both ruidally and wially tithin the reactor cort.
Analysis of the PFS2 data shows that the radial variation of the neutron power with Ivii
ý- 2 Z4 -34 04 ITi I
0 2
-43 lix
?ýVb LSA IA2 I"
w IC 3
J=LGdla IN*
T2 A~ia T=ýi=
.-#3 I--4B ixi
I-
'-J DAS 0.3*1 O.d&
ale 1A.Pt and Dik&
&.3mh 5I6 A
Is Dwif O&SOz Can I o 3.10 2.21 240 viBstiIs 5 Panel% motumi~o Tisrbina TIrp CI Vroplit Ildutronu rasuor
svi&since of this hypothesis, Ga~narzl Slactric showmd that tha staaA?-
line pmzsurn calculation for the KXKI tast, twhiCh had a fincr spatial dinsh, was qulta accuratsa.
Geenaral Elactric has also polntad out tnat the st-azzline ;rsssura rasponso shape ii not as imort~ant tz tha transiant behavior as is tIhe intagratad valua ofs ths staamlina Pra-Szur2 raSponse.
Wt doc nat agr-ea antirealy with Ganaral Eleactric.
In answemr to Q-2.S in Vol=-- 1, General Electric ptrfcrated 2 sansitivity study shzwing tlhe afflact. of nzodalizaation Cdlffarsnt mo-st si7ns) and comparin~g the n'-sults with tho analytical czdal t-hich usas an-thad of crirctar.s I sti cz.
Thz diffarawc Ia i
Wplitudas In this croparizon is on the cv~izý-' of IMr 4Aille tha liff'i-trco In iacin P*aach So'tt= t~tz an ODYio is Ew Ina 14oi oc~
if arinc-as have oppositea trends.
The accuracy claimed by Central Electric ina tht MXN tast can bae dua to the adjustment of the valva opening time.
This adjustmen~t was mada by General Electric to obtaiin a betttr artwsent with the saasur-en preessurm data.
It a~ppeei that the stiael ins model does not predict the amplitudes of oscillations accurataly.
Thnis is also subst-arrz13tad by the staff audit calculations.
However, we agr-av with General Electric that the inte-griated staamline prrzsur-a response is merl inpotart in daetrmining the transient behavior than tha aomplituads of in~dividual oscillations cccu"rIng at the-S8 frequancies.
The Poach Oottco tasts inrdi cas that the doze prassurvs do not ascillatz and t~hiS is thz pruswurt to which the reactor is 3ubj*ectzsd.
Ccoparizon of tris doaz prtesaurrs indicatz that the do= pressurv calculations parfermed b* thun COYN Code Mr Co-nzzrvztivO 11-49 Ixv
Genearal Eltctric haz czncluded t~at the st-mamlins dome and vessel tharzzl hydraulic =odtls s1iwlatz the evtrall cort praSsura rise rather aall in all three axperi~ntz..
This liandz cznfidenct to the cmda pradictions throtigh the full range of pcoQr layals.
Measura-mnrtza indicata "-me oscillailons in cor2 =.it pressurm.
These oscillations have b~on attributad tz instr~ant lina 94fficts by Ganaral Elrectric.
Thia is Ccon-4brazad by thea lack of asaciazad oacillationz in ncutrzn Ylux maasurean-ts.
Tihe neutron flu= pr-a1ct.ions by tUhe ODYMi czde 'wer co-ns-rvativa
.alcivetz data.
We estimate that the peak neutron flux is higher by 34, to EV than the dztU znd the I ntz-rQl of tha nuclam pvzir (whlch is a manaure of the assotht of enirV a~nerata~d) is alto hiGKer I1 r,.hl 1
t 42: t-bun thi dntz.
H+zn~cl, thG Hut-ron flugel wmm prndlct-ad cznsiumativaly in all threa tests.
A3. a ?inal sup,~ General Electric has pre-santed a czlc~lation of
&VCFIPR far~ tast and model.
Wz revictsod the cslculational pr-czdurv and consider it a~pi-priate.
The results show that the L.CPR/ICPR for COYN pradictad transient. conditions 15 within 0.01 of thm values which wold be prdictad Irm tast cznditions; i.e., tha LCPR/ICPR values calculated u~sIng tho measured flew from jet pua.p Ap wsurtments, the saazurcrd pressurs and the mazzurad ptvwr during the
'043ts.
T1ha ODYJ transient czaditiofis Prtedicted t=t out of4 ?4wse aP7?
values cznservatively.
The di'Mrarnces arz bvtwsen -5.2.Z and 6.0: ralativt tz values calculated using "to datz (minus means nancznzervativa).
The diffarences in thest thrze tast rasults in U-52 1xVii
Thoy can only bQ r~gr-ad as best astizata or cc~urat.a pracicions.
Hancs, basaid on thes Psach Scttzm ?.ssts wt do not give any Cre~dit for tha consarvatisz in the o=dals usaid in the ODYN coce.
Tihe czaa will be ntarded as b-ast tstloatz for A.CPIR calculations and. any discrtpanvy batupa~n tha test m¶su1lts and the ecdo will be tr-zatad as an uncarta-inty or, an eriror.
Furthgr tasts,:vuld be nesced tz m-duca these uncartainti4as.
- b.
~XXM Test Ctaisan A brief si,=aaiy of the tast conditions is con-tainsed in Volu=i 11.
KMO plant hzs an unu-uzal ccnfigurztlcn, in that, it has Vxc turbines and tV,- eatz of attlinlas -it1h a ?-hat-2v line in ounch stz-line.
It p~rnsnt
-.1a special zazd3l cznrilderntions fc-;.001,1 simuilation.
A Sporial vc CWo (oyM Cffi'~ 'z~
~o t-- Simulatiz thisi rwfig-u-nation.
Alzo uniqua tz this tast cwa~risznr zs zpposad to the FE-1 czxparison is the =dallnig of turbine stop valve and bypass valve act~uations.
ftQSU7r~d tUrbine stoP valve and bypZss Valve poSitIons bet~wen initial and and of act.=tion wvrv not, available for this transient.
The stop valve behavior can be raiscn~ably estlistad fro= the opening to clazing tlza.
HIo~vC?, "Zo transient r-esponse is quits sensitive to the bypa~ss valvv behavior. The bypazz valve opening speed of the COYN nodal was adjustad until the calculated transient turbine inlet pr-zzuj gneod with szasmi'asznt.
Tihis adjustmnt was mada for only the initial bypass valve opening speed and, thamzsftxr bypass valve position was controlled based on tho plarM cnto paramiatrs.
The rwmainder of the tast.
=dodling Is similar to that of the FS-2 tzst ixix
wzmT' also attibus-t1 tz tht, iRn tr%.Aert linQ dis:
va~nc2A5 sin'C2 no oscillatl~ons wara obsarved in nu-or-n Ylux.
The cal cul atzd prsura rtspcnz-az P2!3 T-n.Ugh thE Cat~a UP to 1.8 secold. of the trzns1znt. time.
Aftr1.2i L8 acconds lbhe calculat.2d pr-25su7-a ar-2 higher ia!
thosa = ~~zuiam.
The calculatad com, =xit pr~zurmha.1 a 4.0 millisaco-nd delay bthind tha data.
Thi s was atrbutad tz the mtal ing of suam 3aarzto-r inertia.
We agmee wjith G~nmr~l Elz1-l.ic t~a
-the overall shape of the COrI axit prssun-.-*spzns2 is duplicatad wall *y the ODYN czdai.
The agn~ent bet--4-n tha calculAxted anid zea~sui-e p-our~et in tha dza ient the
,-Ltzmlin4Q is alzo marambly Good.
Theno Is no cznsafvjaisa in c~alciula-rior of priezures Lp to L&
eczn~d of t7 irisiont tinn.
The azeazurvont of noutrzn flux lndim~.s a double peak bahavicr.
This 4cuble pesak was attribartad to an zscillatizn in ccrea ;n!2ur-2 which tows thzugflt %a ba anhancmd by KXN by~oaz charac'.aristic.
Tha ODYN coda overpradictad the initial neutrtin fluxc peak by appi-c~imately 53% anid undarprvictsd~
theI sozn pek
)We aiSmdtah..
th4at.
the intea~?l cf the calciulatad nuclear power wits higher by aplexaztaly 2CM than ;he data.
Figures 7 and 8 present the co~parisans of measured arnd calcilatad a~ial neutrzn and ;ro~pt neutron fluxts rSp*&cVl Yey.
The calculatid value of ACPR/7CPR was about 9.1% cznsaIrvativa ralative to vie vzlua cmlculatod uzing wsasun-d quantities (sae Tablt 11).
l=Ci
~uan Lmn~a
'-I.
'I t-..
I0 0
(b GAS
£3:O 0.41 I
on DID e.6 6
0 C.2ts 03&
1.9ib 1.0
- D.65 ii 2.mm 3.216 9 1 Ii.re 0
MOO Tu*
ia Vulprni?
5cwoompm'
- loutron Touar
s;=2time anzglysis of core nautrnc~a and th~armal hydraulics wit~h famdback 1n t.xo dinzansions (rafir-anca 2-1).
Ine ENL-TWIGL cmd* has a nutbmr of advantages ever the 00Th czda.
TlhD calcul~ation can be perfor~sd with tzn nautrtof energy gn~ups inl tijcdlansicnal (r,:-)
cylindrical gvcoetry.
It, has the cpabaility of allcwing for five radial scr-aa zones.
Any i~o-t~ant radial tafact.s will, theraforv, be calculat.&4 by EML-TWIGL The ENL-TWIGL. code alsa has tý; disadvanta;:z m-latlvc to tha ODYN coda.
Thasa dizaaviantagas 2ar: (1) the lack os' a byp&3s flow chznnsl, and (2) the indapendanC3 of Vie Da~plmi* rzactivity with void fraction.
Weighing these 16duj= g~oan dis ataa of WIL-TWIGL. rQ1 attis to the ODIN czdo, i t is Cal JvduDt thIt 1Z'rr; wil I IFvt &ey ~tnl affeoct tho cr&MMri1son TIM cal cul ational zalbhc4 was davelezed using the Pitach Bztto= tests
-as a banc.1mrk.
Assming the ftasured po~r histzry Cpc%ýQr vs.
t1ia) in tha oi-s as input, RELAPSE calcujlat-as tht systuau thermal-hydraulic paramators and provides the 8flL-ThdIGL code with the ti..
depen~dent care inlet imundzry cznditions;, I e., pressui-a, flow and twMoratuts variations with tic*.
Then, the SHL-?rJIGI code ;erfotss the s~azz-tlma analysis of the cars ncutrcnics and thermal -hydraulics.
Tha calculated powr histary is than cocapared with tha =nasurad powar thich was Input to the REL~APSE code.
If the di~fferences are large tho czlculatsid pztir histary Is used in the RELAP38 code and the czlculationz arPr ats until tha pz~zvr hiz~.ry calculatted by the EML-TWIGL coda ii in good ag otwith the pcts iztz-y input to xx~v
4-0 0.
- 0.
2 A50.
F'ractionall"f Care ffeir3hý
IIna 1i:11 DhoGLfloo 2 Ttobh TaB01b Tendit.
1DtllI I
nU Id lo w 0 8.4
- 1.
USU II)
M-0.0 0.6 0.3 I)A BAD 0.0 0.7 F'ractlouvn-i' Core Ile-IgIa
Peach flattam Oti rt hi I T
1 Tt 2a 250.0D oil n-
-'I 1-4 I;4~
"'.U, Li 200.0 M.8DA 100.
t-5O0.
0.0 04tr 0.t s
At a me~ting an July 14, 1-972 attade by GE and our -nsultants f-z zilcul-atid ty GE with tri COYN oone a by SNL with 'the S.fl-NICL RVL.AF-3B czda3.
This T74S transient w~as 11or FS-2 at and-ci'-cycle 2 witi the ract-or at an all ro-ds cut c=ndition and with a Haling o-mr pc-ar dis£tri buti on.
The mzzt-r :ti; was iss~zed t.z c--nj from the pr-imary trip signal far this trzinslarit, i.e., t~e ;ositian of tne tur-ine s cr czrfr-..
valve.
All of the syst~ew input ;a-.aftta
- tr~e alscuj~zad a~nd values *or--sin~
The mazcur was zs3ura-tz b2 operati ng at a 104. 5 ptr~rn: of full rat~ad ;C~ and at 100 Per-ari:
of ratad czr-flowt.
inck initial calcu~lations by GEr an-s SHL diffe-iad =nsildar!bly.
The zo a fu oin t-iSre t;PlmlLe&
Lz.
by SL a-42o r 6 gpa-atar in In e~r output althougn tha initial risa and falloyf of the pzwmr waz acaut the saaa.
The INL calculat",an prad~.ada pact paove of cvmr 7 tiens t.1a initial czrt pcw~r at aL-ut 0.9 s-"azndz.
ThQ GI czlculzticn r~sultad in a peaak ;zowmr of about 4 tiozs the initial corv poe at about 1LO sacmnd.
A C2 evaluation of its calculation ruaulttd in finging two sinificant er-rors that led to a now aE calculealon.
OMMe of the errors 'wa the szaa~sllne lenrth.
It had originally bosn imput aU A~e f&mt aheasth* vaflue smluld have brien 400 fvzt.
GE also founid tptut one of Itz precaazing czdias had im~rzparly cutdfor the Dc~plar r-eaativity fkdu Variation with void fi"'aclOn.
This new Gr calculatioh osjultad in &am sevare transiant than the earliar
ine QDYIh-SCAT pradie-.ion ofl thz thrsg Psacri
- 2z-m--ansiant tzst..S and one KYM transient ta-st desonstratad a L-uncar-~ainzy of apprz~imataely 37ia of r.CPR/tC?R at a C.:nfidencs levai.
We have catnintd this using X-distribution.
Ho
.--dit wea given for coasureMant e..r:rs.
This -esults in a 2= ;.C/.IC?.R u r.ain.-y of 0.(}a for a tr.nsient vnich dgr--aas tlhe CPR f.'r-a n initial value Of 2-.30 O th.4,1 limit Of '-.CS.
Since these ta!!.i r-asent a very limitsd data base, it is liksly that: the Zz unce.,-.i-
-an be reduced signi"icrritly by the acquisition of actiticnal test data 11mr cojparisan tz code pmietioras.
Hencz, w eocn that additional int.*ral plan-t.-sts be per,"creed tz qualify the cdae with a higher cztif i do-,CU.
Thue ODYN statis:i=l analysis was performd 1y Genral Electric at cur re-uest in or-der to provide a
.mxntiti'e basis for dmterwining if the ODY0 licensing basis Contains an ac=;tatle leael of cznsarizti ssi Two quantities we~rv calculat~ad in this analysis:
the probability of tlie axevctsd &CPR exceteding
&he licmnsing basis &.?R; and the probability oi exxc-eding the thermal-hdraulic design basis (i.e., probability of exc.eding 0.2. of fuel in Soiling Transition).
Thti (DYH Coda is intanded tz be used to calculata the change in Critical Prvzr Ratio (CPR) during rapid priassurize*ton trunaients suct as the loss of load and
-Ieeda'atar c=.,ollar failure transients.
This info-mation is use, in cm-'
binatioan wi th tha General El scric Them. l Analysis asis (G"ETAB)
CR safety liiat to estýalish the oprting limit CPR.
G"TAB is a statistic:l analysis 11-71
mcciflIcztions tz Technical Specifications to damunstrata tnat -.-I sc?,zm cnrc-ari~stiicz ind~eed belong to the sa= pcpulatlon cr c~fl be rep antiac by Los sa= dist?1bution.
General Electric should also assass thia impa=c-.C tne us o bast essim.-ta distributions en pr-viclng this asszw-inca.
The tr-asimmt rosponse tz raid cvv ;-a2szura Qevtrz is depan~elnt en t." czrs avar-age -axial po--sr distribution and axizl &--masur-a distribuz-lc snc Vil.3tess sz-tngly influenc2 both "ae void and c~nt-ml rod -sc-tivity feecback.
Ganaral Slactri--c has deflinad E~;cpsur-u Inc=~ as a moasaure cof Viv a~xial C~osur-a dizzri-buticn.
EL:;sur-a Index indicz..as the tx-tant to wnic-n an actual a=lal axpzurm distribution differs f7= toe ideal, design =.ial 6@XFOzu2 distribution (Hal1ing dis-burticm).
ODYM 11 lnsins calculaticnS US'V the Haline distribution as i Ur-Ct..
G'fiQlo El V~t~-i C ?~
Uo ShM -t~h-a =nVr~V1% Zafsi L
&atac with tLhi S anczunts-ad during cp1orlia arm moma frvorable t'~4n ihe Haling distribuzion.
Thbis cznaarvatiza tieas quantitfied as pzut of the Over21l 00TH statlrtical anlyisbyincluting E£xpcsu-. Intax &r, ons of the lnu%.t varlables In wie f~spcnsz surf acz.
To establish a basis for the expec-cad distribution of £xo;sura In~dicts, CGeneral Electric praesntad data frog 11 oper-ati ng raertzrs at end of cyci a cz-ndi tions anc 1.5 data points for 5 OpeRaiG uctoZrs 3-- mid-CYCle cznditio~ns.
in rss;cnsa tz a mquest for additional data Oion served Empcsurs Ircee, Ganeral Elect.ric przvidod a aidditicnal dztz painut.
Bacauzza of the lim~tat nuooor of d7t~a p i nta and the 1 argo sctour In the data we weru led tz ques'tion the aSsi~tian thatMdata Vaa narwilly distribmuted.
The insdividual data pcinta Obuline'l ?1i=o CG erzl Electrýic W'rV subjecued ta the k~test for marmtiaIty by II-7S
analysis t..
d*=nzarori Un h
of tn margin tz the GTAB limnit~.
rhis saisticza analysis snould nct taxta c?"dit for cznsarva-ism in --n. Maling
- cwr dist7ibuticn.
it. =,y ?.aka m~clit *.or di3 lu-ticri in scram spftxd, if G-Anerzi Electric d&=-ns~tr~ts t" the distrib~ution us"d in Wis analysis is
=;I~l totn plant spa-1:i1lic casia.
Tho analysis s?2ould a~zz Ce~a~fx was tased on2 :ne plant. tast ca=a.
Ganer-al Electric =ay vuiz,) to c..nvciu-wa accitionp-1 variacle: in.ýe s i~clanzlysiz if azsswancs far c-nsari/2tism far *r2cn Spacific aZP~l~cIt1,Zn is pr!.V1cvd.
xcviijxcv~i+/-
111.
STAFF POSITION we stat.ac our position on the COYN coc=
and it~s application in Refervnca 35.
-ma following is a itatment all t~hlat position.
- 1.
ý!CPR Calculations The analysis for &.CPR must he ptrfcr-,d in ac:zrdancz w*ith iather approach A or A.
ACPR Calculatiens with Marain Penalty..
Th i zpT~~
is rcA~piszi of tha thrci. ivtxl; hlain~Ac l~
- 1.
ftffjor ACPR calculitions using the COYN &7nd the improved SCAT (Raftranca ZZ) czodas for thz tr.ansiantzs in Table III and uzzing the input pazamtars in the ranner przpzsat in pages 3-1 thrzu~h 3-4 aY NEDE-24154-P.
The sensitive ir~pu~t pra'atars ame list~ad in Table IV.
- 2.
Detarmine ICPR (cparating initial critical pctwer ratio) by adding
&.CPR caslculatad in stop I above to the GETAS safety limit.
Calculatz
&CP R/ICPR.Z
- 3.
Da-termine tho now valua of 1CPR by Adding 0.0"4 tz the value of aPRYIC?"R calculated in suop 2 above.
Apply this margin t~o Chaptnor 1.5 analysla of Uso FSARs aut~mitt-.d for OLi, a~nd Uso and to r-loads.
xcix
~. Statistical Aourpach for" Reduction of Mar--in Penaltv Santral Elcrcassessad the0 prcbability of the* &CPR during a limiting tranziaivth 3-Xecaeding the &.CPR calculatZ4 for the prjposed licensing basis tanslantm (?HEfl-2S5154-P r-asponse to question 4). Thu Ganeral Electric s-tucy
~ec~tt~dthat thl3 prttabilitvy, basa-d on operating data over saviral fuel cy1clas fr= a grcup of plantza, is Ytry loet.
Tho kay para=.zrz in the study in2 scran speed, powe~r isval, poa'er distribution, and an astimtat 01f COYN unc37-taintlas.
Tha proposed apprza-ch utlllzes tha consaria-tizz in-herunt In tht itatistlci-I d.mviaticn a? thQ actual operating ccn~iticns fro= the limiting cnnditlons £35L~d for the first thmt. pr-az;-ztesn in l1,rxngt31 Caloulations to czzensatn for potential n.Or1cr~afftlSWS fr-e thm Corti Untaminties.
The staff h~is concluded that the usa of and-of-cycle power distributionis
-'r-amu
-yli sa~veral reactzrs tz attain cr-edit for x~rgin czscrvztiesx rolative tz Haling potiar distriburtizn is mt' zzrorpriata.
Thar*a i3 no assurance that the and-of-cycle pcowr distribution cznsarvazlsu obtained frou operating reaact r history art -eprtsantativt of the and-of-cyclsezcriditians.ti~ch will e=1st for the specific czra..
We havs also czncluded that 3cram spacd data used in the GE st~atistical assassw~nt cust be prayed applicable to specific licanse and rtload.appllcations.
In ord.ar to take eraedit for consarvatism in the szrzm speed perfornance for rloads, it
=~.t be dezonztraet~d that thane is insufficient. reason to ftjact th;@ plant-specific scr=e zspeed as being wiithiin th* distribution assL~ed in thr1E stati:-tical analysis.
For CP and OL, the scramspe ci
Valui~ of apVICPR uncar-tainzy at a 9SE' czrOidanca Izvel when such~ a mduc-tion czrn ba justified by additional t~ansianm t~st data.
th tf I'a..
cnldo th~at the suatisti.-al approach~ to campansau~ for p~zarmial norzviraim I 2ac tht ODYN uncert.ainties is accaptable with2 tih following limitations.
1..
powai distributior cn =naVati~s shoul d be excluded.
- 2.
Sc-.i3 SPoed
=~S47-12aisms mus: ba doo~nstraltad to ba aplic~bll to PIZ=r sp&cific C=s05.
- 3.
Calculstlons should ba parfaimeý4 using a code uncertainty value vlAich fi5 27 o,? the 4?Pi/i7U for~ a lizitirrg t nýA'rwr t..o j~rmiit fr
=
ui altaintie, IArludinga~~
agoc~&~)
bas"d ont3 t apprvard transient tast data bast.
This results in a value o1 :t 0.06.a in LOWICP unc2r'taln-ty for a translsnt extaending over' a CPR range Of 1. 30 tz 1. 08.
- 4.
The trmnslent test dat2 b~ase must be expanftd and sutmittaed for staff riview to Justify, any reduction in the value 0f ODYN Czda uncartainty (2= valum of &CPR/ICPR at a 95% con? idenct level).
S. A nows statistical analysis conforming vith these m1ittln ust be provi ded.
Ciii
- 11.
PRES-SURE CALCUJLATIONS Calcuia'tions sho;uld be par~'orrd l0? the M1ain Stzam Isolation Value c105ura event with position switch sc-,a failure using tha values lis-.3d in Ta~ble 12 as par staff evaluation to arrive at" t1hs overall czda uncar-"inty in pressure calculation.
A44 this uncirtainty to tho ODYIN calculat:ad pruzura for t.ý1 avainz in CL, C? and Wclad a~picztion3.
if Ganaral Elmetric can dsanstratsa that this uncsrtainvy is vary small (e.g.,
by a factr oY 10 or mcr2) rilative tz "ae bias in dtarminirig ASY.E Vatssl Ovtrpm~ssurv limit, no addition of uncertainzy to the calculations of pressure is needed.
We note that thars is an errzr in Enclosure 2 of Reforance 335.
The bounding values of th~e drift flu~x parzisatrz shculd hav* been in cznz:aao-nc2 with Tabla I as per stall f val uati on.
a CV
TiAS LE IV IMPUIT PARMETERS SENSITIVE FOR THE ANALYSES CPOD scram spt--^d -
at tahc.ical speicfication liwit.
Scram satpoints -
at taclhnical spacification limits.
Pr-cucticn-eystam logic dalays - at aquipment specification limits.
Ra11af ValV4 capacities - Miniumn specified.
Raliof valva satpzini-s and ~-es~cnsa all valves at specified =p~ar? limitz of satoints and slcw,-s-specified response.
Preassurt drep fiow v&2zal tz relief valves -
nma~izue value.
Stsasmiln and vessel geometry -plant-unique values.
initial pcwmr and staw flow m atir plant cipability.
Initizl ;rmssun.,
Xaw4 ooi flow c'ai...n vzlufj2 SL+
P-~u laret czPability.
Coiri-a si--p~o distribution - cznsIsltznt waith Hnling =nýa cf gpation.
C_ tc9 cvii
- 4.
Ths trnsients listed in Table III !r-- shart '.arm licensing tzn-sients.
If tho coda is intanded to be used flar long t~m transients or dilfaerent typas of Owerprssurization transient~s such a~s ATWS, appropriata riedifications shculd be m~ade.
Cix
- 13.
Frigg Loop Prnjact, Frigg-2, AB Atcmanergi, Stociolm, Sweden, 2ý.8.
- 17.
Rouhani, S. Z., "Void Measur.en:ts in :he Region of Submcoled and Low Quality Boiling," Symposi, aon Two-Phase Flow, University of *=atr, Oevon, England, Juno 1968.
- 18.
- Rcuhani, S. Z.,
"Void Measurement.s in the Region of Subcooled and Lcw-Quality Boiling," Park II, AE-RTL-72S, Akti.boiaget Atcmenergi, Studsvik, Sweden, April, 2366.
iiEDO-2091.3-P, "Littics Physics Ae-thads," C. L. Martin, June 1578.
- 20.
"GEGAP-I1:
A Mcdel for the Prediction of Pellat-Cladding Tharmal Conduct.ancs in EWR Fuel Rods," General Electric Raport. HEOC-20201, November, 1S73.
.21.
- 0. F. Ross (NRC) lett3r t: E. 0. Fuller (GZ) dated June 2, 1:78.
.2.
E.RI F-.64, "Transient and Stability Tst.s at P2Bch Boot=c.
Atomic Pcwer Station Unit 2 at End of Cycle 2," L A. Carmichael and R. 0. Niemi, June 2-78.
- 23.
Letter froic K. W. Cook to R. L. Tedasco, MFN 3137-78, "Transmitta oil Responses to Round 2 Questions on the ODNT Transient Model," dat"d Dec. 13, 1578.
- 24.
L-ft"125 flLA P-ioarzz
~fot; Caelcul~itirn Rqpid U-111, Cor-2z..
SHL-NUREG-22011., "User's Manual for RELAP-3E-MWD 2I0:
A Reactor Systam.
Transient Code," 1977.
- 25. BNL-NUREG-24903, "Core Analysis of Peach Sotton-2 Turbine Trip Tests,"
N. S. Cbeng, 0. J. O}ia:nd, Septaser 1578.
- 27.
Memo fr-.m F. Odar to Z. R. Rasztoc-=y, "Meeting with General Electric at Brookhaven Na.ional Laborntzry," October 17, 1978.
Z.
Latter fr*m K. W. Cook of GE to Frank Sc*r*oeder of NRC, October 10, 1978 on Potential Dlffer*nces bctwetn GE and SNL Models.
- 29. Latter fro= K. W. Cook of GE to Frank Schrtde*r of NRC, October 26, 1978, on Trinsmittal of E.xposure Dependerrt Data.
- 30.
Transcript of ACRS hearings held on M?.rh 1-.4-20, 2579, Los Angeles, Cal iforia.
- 31. Uattar from K. W. Cook of GE to R. L. Tedesco, Clarification of ODYN Model Uncartaintles, MFN 123-79, dated April 30, 1979.
- 32. Lttar f er u K. W. Cock of GE to R. P. Denis&, Additional Void Fr!action Inlormazion Reustad for ODYN Review; WN~-2lS=79, August 27, 1579.
111-13 cXi