NUREG/IA-0013 Intema-onal SAgreement Report RELAP5/MOD2 Calculation of OECD-LOFT Test LP-SB-03 Prepared by C. Harwood, G. Brown Central Electricity Generating Board Barnwood, Gloucester GL4 7RS United Kingdom Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Washington, DC 20555 January 1990 Prepared as part of The Agreement on Research Participation and Technical Exchange under the International Thermal-Hydraullo Code'Assessment and AppIcation Program (ICAP) Published by U.S. Nuclear Regulatory Commission
Transcript
NUREG/IA-0013
Intema-onalSAgreement Report
RELAP5/MOD2 Calculation ofOECD-LOFT Test LP-SB-03
Prepared byC. Harwood, G. Brown
Central Electricity Generating BoardBarnwood, GloucesterGL4 7RSUnited Kingdom
Office of Nuclear Regulatory ResearchU.S. Nuclear Regulatory CommissionWashington, DC 20555
January 1990
Prepared as part ofThe Agreement on Research Participation and Technical Exchangeunder the International Thermal-Hydraullo Code'Assessmentand AppIcation Program (ICAP)
Published byU.S. Nuclear Regulatory Commission
NOTICE
This report was prepared under an international cooperativeagreement for the exchange of technical information.* Neitherthe United States Government nor any agency thereof, or any oftheir employees, makes any warranty, expressed or implied, orassumes any legal liability or responsibility for any third party'suse, or the results of such use, of any information, apparatus pro-duct or process disclosed in this report, or represents that its useby such third party Would not infringe privately owned rights.
Available from
Superintendent of DocumentsU.S. Government Printing Office
P.O. Box 37082Washington, D.C. 20013-7082
and
National Technical Information ServiceSpringfield, VA 22161
NUREG/IA-0013
International'J Agreement Report
RELAP5/MOD2 Calculation ofOECD-LOFT Test LP-SB-03
Prepared byC. Harwood, G. Brown
Central Electricity Generating BoardBarnwood. GloucesterGL4 7RSUnited Kingdom
Office of Nuclear Regulatory ResearchU.S. Nuclear Regulatory CommissionWashington, DC 20555
January 1990
Prepared ats part of
The Agreement on Research Participation and TeohnlcaJ Exchangeunder the Internatlora Thermal-Hydrauufo Code Assessmentand App•atlon Program (ICAP)
Published byU.S. Nuclear Regulatory Commission
NOTICE
This report is based on work performed under the sponsorship of theUnited Kingdom Atomic Energy Authority. The information in this
report has been provided to the USNRC under the terms of the
International Code Assessment and Application Program (ICAP)
between the United States and the United Kingdom (Administrative
Agreement - WH 36047 between the United States Nuclear Regulatory
Commission and the United Kingdom Atomic Energy Authority Relating
to Collaboration in the Field of Modelling of Loss of Coolant
Accidents, February 1985). The United Kingdom has consented to the
publication of this report as a USNRC document in order to allow
the widest possible circulation among the reactor safety community.
Neither the United States Government nor the United Kingdom or any
agency thereof, or any of their employees, makes any warranty,expressed or implied, or assumes any legal liability of
responsibility for any third party's use, or the results of such
use, or any information, apparatus, product or process disclosed
in this report, or represents that its use by such third party
would not infringe privately owned rights.
Abstract: This report compares the results of the RELAP5/MOD2 analysis withexperimental measurements.
A simulation of test LP-SB-03 was previously carried out at GDCD using theRELAP5/MOD1 code. RELAP5/MOD2 was developed from RELAP5/MOD1 and containsmore sophisticated hydraulic models and constitutive relationships.Comparison of the RELAP5/MOD2 and MODI calculations show that RELAP5/MOD2performs better than RELAP5/MOD1 in a number of key areas; notably masserrors are much reduced, there is improved numerical stability, andimproved separator modelling and modelling of accumulator injection.
iii
CONTENTS
ABSTRACT iMi
CONTENTS v
SUMMARY vii
1. INTRODUCTION 1
2. INPUT DATA AND MODEL 2
3. STEADY STATE AND NULL TRANSIENT 3
4. TRANSIENT 5
4.1 DESCRIPTION OF EXPERIM1ENTAL TRANSIENT 5
4.2 RELAP5/MOD2 RESULTS 5
4.3 COMPUTING TLME 8
5. DISCUSSION 8
6. CONCLUSION 10
REFERENCES 11
TABLES 12
LIST OF FIGURES 13
FIGURES
Microfiche of computer output has been filed under Safety Technology Section inMicrofiche Archive at Barnwood.
CWl 00 IR6KEL/GBI1
V.
Summry: In order to confirm the ability of RELAP5/MODZ to describe a smallbreak LOCA sequence in a PWR type geometry, analysis of test LP-SB-03of the OECD LOFT experimental program has been carried out. Test LP-SB-03 simulated a 0.4% cold leg break in a PWR, with failure of highhead safety injection; cooldown was achieved by feed and bleed ofthe secondary side, some time after core uncovery.
This report compares the results of the RELAP5/MOD2 analysis withexperimental measurements.
A simulation of test LP-SB-03 was previously carried out at GDCDusing the RELAP5/51OD1 code. RELAP5/MOD2 was developed fromRELAP5/MODl and contains more sophisticated hydraulic models andconstitutive relationships. Comparison of the RELAP5/MOD2 and MOD1calculations show that RELAP5/MOD2 performs better than RELAP5/MODIin a number of key areas; notably mass errors are much reduced,there is improved numerical stability, and improved separatormodelling and modelling of accumulator injection.
Overall agreement with experiment obtained using RELAP5/IOD2 isexcellent, with all key phenomena correctly predicted, in the correctsequence with accurate timing. The CPU to real time ratio wasapproximately 3.5:1 on the Harwell Cray-I computer.
Results of this calculation have been submitted to the OECD LOFTprogram review group as the United Kingdom contribution to thecomparison report for test LP-SB-03.
vii
L. INTRODUCTION
Loss-of-coolant accident (LOCA) analyses for the Sizewell 'B' Pre-Operational Safety Report (POSR) are expected to be carried out mainlyusing proprietary Westinghouse computer codes. In order to assess thePOSR calculations, and develop a CEGB capability for LOCA analysis foroperating ?;Rs, GDCD is carrying out independent calculations of limitingLOCA sequences using computer codes accessible to CEGB. The assessment isbeing carried out at the request of N.T.
The RELAP5/MOD2 code [4] is presently being used by GDCD for calculatingsmall-break LOCA (SBLOCA) sequences for Sizewell 'B' [5]. RELAP5/MOD2uses a six-equation two fluid model to describe two-phase flow in thereactor primary and secondary systems. It supersedes the RELAP5/MODl code,which employed a five-equation two-phase flow model (one phase constrainedto thermal equilibrium) and used less sophisticated models for flow regimetransitions and interphase interaction terms.
To gain experience with using RELAP5/MOD2, the code was used to simulateSBLOCA test LP-SB-03 carried out in the LOFT experimental reactor [2, 3]under the OECD LOFT programme. An analysis of this experiment waspreviously carried out by GDCD using RELAP5/MODI [1].
LOFT test LP-SB-03 simulated a 0.4% cold leg break in a PWR with no high-head injection. As noted in [1] the experiment provides a severe test ofa reactor analysis code since a wide-range of complex phenomena whichoccur in a reactor SBLOCA must be simulated, including:
(1) Steam generator heat transfer in forced circulation, naturalcirculation and reflux condensation mode;
(2) Core heat transfer for uncovered core conditions;
(3) Single and two-phase critical discharge flow;
(4) Two-phase pump head degradation;
(5) Accumulator injection.
The present report discusses the RELAP5/,OD2 analysis of test LP-SB-03, indetail. The results of the present calculation have been submitted to theOECD LOFT program review group as the United Kingdom contribution to thecomparison report for test LP-SB-03.
GDCD is in the process of performing analyses of hot-leg break tests LP-SB-01 and LP-SB-02 carried out in the same series, and these will bereported subsequently.
1.
2. INPUT DATA AND MODEL
The input data were based on the INEL deck used for the pre-testprediction, and for the RELAPS/MOD. calculation reported previously (1].The modified noding scheme employed (figure 26) included a number ofchanges to ensure compatibility with RELAP5/MOD2. These changes were:-
(1) Changes to both the inlet and outlet plenum models. In (I] theinlet plenum (upper downcomer) was divided laterally and verticallyinto four volumes. For the present calculation it was remodelledas an annular downcomer in three levels, with the cold legsconnected to the central volume. The outlet plenum was changedfrom two vertically stacked cylindrical volumes to three to complywith the format of the inlet plenum. This nodalisation was adoptedto. comply with EG&G recommendations for use of RELAP5/MOD2 with thecross flow junction option [4].
(2) The connection between the cold leg and the break discharge linewas modelled as a tee using a centrally located cross flowjunction.
(3) In accordance with EG&G guidelines, junctions at the reactorpressure vessel (RPV) nozzles, the break line connection to thecold leg, and the pressuriser surge line connection to the hot legwere all treated as cross-flow junctions. In these junctions themomentum flux terms are deleted from the momentum conservationequations used to calculate junction flow.
(4) Junction Options: The MOD2 version of RELAP5 has a new optionby which the junction inlet void fraction can be corrected to allowfor flow stratification in the upstream volume. Separate modelsfor a centrally located junction; upward Oriented junction,downward oriented junction are available. In accordance with EG&Gguidelines, this option with the centrally located junction modelwas invoked for all connections between horizontal pipes.
(5) Volume Options: The new boron transport model and facility toinclude fluids other than water were not employed. Other changeswere needed in specifying initial conditions consistent with the 6equation formulation.
The calculation was perfbrmed on the Harwell Cray-I computer usingRELAP5/MOD2/CYCLE 36.01 incorporating corrections to Crayconversion errors implemented by UKAEA Winfrith. An error that wasidentified but not corrected was that the code failed to utilisethe horizontal stratification model at the junction between thebreak line and the cold leg. (see (4) above). It was discoveredthat code cycle 36.01 did not employ this model in a cross-flowjunction due to a coding error. This error has subsequently beencorrected and the horizontal stratification model is workingcorrectly in cycle 36.02. The impact of this error on the presentcalculation is thought to be small and is discussed in section 4.2
.(b).
2.
3. STEADY STATE AND NULL TRANSIENT
RELAP5 does not solve steady state equations hence the code must be run intransient mode until stable conditions are achieved. This process isaccelerated in RELAP5/A1OD2 by use of a 'steady state' option in which thethermal inertia of heat structures are set to artificially low values.The steady state option also checks for convergence of a steady state.
Key parameters were controlled using RELAP5 control variables to providethe necessary feed back, to achieve the required steady state. Parameterscontrolled in this analysis were Pressuriser Pressure, Primary Mass FlowRate, Secondary Pressure and SG downcomer water level. Calculation ofsteady state conditions is discussed below and illustrated in Figures 1-8.The experimental values at the start of the transient have been added tothe graphs, where- available, together with error bars.
Pressuriser pressure was set by attaching a fictitious RELAP5 timedependent volume to the steam space of the pressuriser. The dummy volumewas assuned. filled with saturated steam at the desired pressure (15.26HPa). Pressuriser level was not adjusted as the final value fell withinthe experimental uncertainty range. Primary pressure in the steady staterun is shown in figure 1; pressuriser level and surge line flow infigure 5.
Primary loop flow was adjusted by using a proportional/integral controller(based on loop flow error) to control pump speed. Active loop mass flowin the steady state run is shown in .figure 2; inactive loop mass flow isshown in figure 3.
Secondary side pressure (and hence primary side temperature) wascontrolled by a proportional/integral control system (based on SG Domepressure error) operating on the main steam control valve. Hot and coldleg temperatures in the steady state run are shown in figure 4.
Steam Generator downcomer collapsed liquid level was controlled byadjusting feed flow. Feed flow was set equal to steam flow plus a termproportional to the SG level error. The SG level was set higher than themeasured value, as at lower levels, steam entrainment was found to occurin the SG separator component leading to an erroneous prediction ofvoiding in the downcomer. Various steam generator parameters in thesteady state run are shown in figures 6-8.
It is seen that there is. no evidence of the oscillations in the stefmgenerator recirculation flow that appeared in the calculation of reference[1.
RELAP5/MOD2 calculated that a stable steady state was achieved at 78.9s.In order to check the stability of the converged steady state a nulltransient was run in which the steady state controls were removed andbreak flow and pump seal injection flow were set to zero. Apart from ananticipated decay in pressure due to pressuriser heat losses (thepressuriser heaters played an insignificant role in this test, and wereomitted from the model) the calculated plant state was stable. Conditionsafter 15.7s of null transient were judged acceptably close to initialexperimental conditions and the transient was initiated from this point.
3.
Table 1 shows a comparison with the initial conditions measured in theexperiment and those used in the calculation. Also shown are the initialconditions used for the RELAP5/WODI calculation reference [1]. The onlysignificant discrepancy is the water level in the SG downcomer which, asnoted above, was made artificially high in the RELAP5/MOD2 calculation inorder to avoid steam being entrained into the! lower SG downcomer.
4.
4. TRANSIENT
,4.1 DESCRIPTION OF EXPERIMA.ENTAL TRANSIENT
In the experimental data report (31 the LP-SB-03 transient isdivided into four distinct stages where different phenomena occur.These are as follows:-
(a) Rapid mass depletion phase. This is the period betweenbreak opening and pump trip at 1600s. During this phase theflow is a well mixed two phase flow and mass loss isrelatively rapid. The break does not remove sufficiententhalpy to overcome decay heat and some enthalpy isconsequently rejected via fluid discharge from the SG •ainSteam Control Value (MSCV).
(b) Boildown phase. This period occurs after pump trip at 1600s(when primary system mass is reduced to about 50%) when theremaining liquid falls to the lowest points in the circuit,the RPV and loop seals. The break flow transitions to ahigh quality steam flow, leading to a lower rate of removalof mass; however the rate of removal of enthalpy is nowsufficient to give primary depressurisation. Heat transferfrom the primary to the secondary continues to be in theforward direction because of steam leakage from the SG MSCV.The core drys out and the break is isolated during thisphase. Forward SG heat transfer is also lost.
(c) Cooldown by secondary feed and bleed. This phase began whenthe operator reintroduced SG feed and opened a SG reliefvalve at t- 5415s. This action was initiated after cladtemperature had reached 977K in the reactor core. Forwardheat transfer is restored in the SG and the primary pressurefalls rapidly.
(d) Accumulator and LPIS injection. This phase occurs after t-5800s, after primary pressure falls below the accumulatorset point. Accumulator and Low Pressure Injection System(LPIS) flow rewets the core and refills the primary system.
4.2 RELAP5/HOD2 RESULTS
Results of the transients calculations are compared with data infigures 9-25. In these plots, time zero refers to the time of.opening of the break valve. Table 2 shows the timing of key eventsin the test and in the calculation.
(a) Primary-Secondary Pressure. Primary and secondary sidepressures are plotted in figures 12 and 13. Agreement withmeasurement is seen to be very good.
5.
In the period before pump trip, calculated to occur at t-1660s the break nozzle discharges a low quality two phasemixture, resulting in a relatively low enthalpy dischargerate. Consequently, the pressure tends to rise, causingperiodic cycling of the main steam control valve (MSCV) onthe Steam Generator. The cycling of the valve is correctlypredicted by the code, though RELAP5 predicted 2 cyclesinstead of the 4 measured. (Note that in the test the MSCVfailed to completely reseat leading to an estimated leakageof 0.13 kg/s [3]. This leakage rate was simulated in theRELAP5/M!D2 analysis by using an appropriate minimum valveflow area.)
After pump trip at t- 1660s the break discharges highquality steam, leading to a steady depressurisation of theprimary and secondary systems which is well represented byRELAP5/HOD2. At about 4500s primary pressure is calculatedto fall below secondary pressure (figure 11) owing toreduced heat input from the core which began to uncover at4300s. This is in good agreement with the measurement(figures 12 and 13). There is experimental evidence thatreflux condensation continued even after primary pressurefell below secondary pressure [1]. However RELAP5/MOD2failed to predict this behaviour. The pressure levels outafter break isolation, and then falls rapidly afterinitiation of secondary side bleed and feed. (t- 5415s inexperiment, t- 5308s in RELAPS simulation). Bleed and feedwas initiated manually by the operator after peak cladtemperatures exceeded 977K. The depressurisation during thebleed and feed phase is seen to be well represented byRELAP5. Accumulator injection occurs at 5501s when the setpoint of 2.84 MPa is reached. The reduction indepressurisation rate is due to steam formation as the coreis rewetted.
(b) Break mass flow rate and Drimary inventory. The measuredand calculated break flows, and the measured and calculatedprimary inventory are shown in figures 9 and 10. Agreementis seen to be extremely good.
The sharp drop in calculated break mass flow rate at t-1660is associated with pump trip, which results in break-down offorced circulation and emptying of the cold leg pipework.The transition from two-phase conditions to high qualitysteam conditions in the cold leg causes the discharge flowto drop sharply. The magnitude of the flow rate reductionis seen to be well predicted by RELAP5/MOD2. In section 2it was indicated that a code error prevented the horizontalstratification model from being used in a cross flowjunction. This caused the break line junction to the coldleg to use average upstream conditions even when the coldleg was stratified. However, this error was consideredinsignificant as the cold leg drained rapidly after pumptrip hence the potential mass flow error was small. Thecalculated primary inventory agrees well with measurement upto 6100s after which the ECCS injection is overpredicted, asshown in figure 25.
6.
(c) Fluid Densities in Primary Pipework. Measured andpredicted fluid densities in the cold..leg.and hot legpipework and in the break discharge pipe are shown infigures 14 to 16. Agreement between measured and calculatedvalues is seen to be good. After pump trip the hot legdensity shows a sudden fall, followed by a recovery. Thisbehaviour is believed due to the fact that when forcedcirculation ceases, the fluid in the hot leg drains backinto the pressure vessel; water held up in the steamgenerator then drain3 downwards causing a partial refillingof the hot leg and loop seal downside. This behaviour isseen to be reproduced remarkably well by the RELAP5calculation (see figures 16 and 17).
(d) Clad Temneratures. Fuel cladding temperatures at theelevations corresponding to the centres of the six RELAP5core nodes are shown in figures 18 to 23. The timing ofcore uncovery is seen to be captured quite well by theRELAP5 calculation, with the rate of progress of the dryoutfront very well predicted. There is a tendency for RELAP5to over-predict heat up of fuel in the lower part of thecore and to underpredict the heat-up at the top of the core.This tendency was also.seen in the RELAP5/MODI calculationreported in [1]. It was suggested in [1] that the effectwas caused by the return of condensed water from the SG. Inthe calculation the water falls on the top core node andenhances cooling there. It is believed that in theexperiment the water ran down the core periphery and wasboiled off at the dryout front, contributing to heattransfer throughout the dry part of the core. A multiplechannel core model would probably be required to correctlyrepresent core heat transfer under these conditions.
Following feed and bleed initiation RELAP5 correctlypredicts the rewetting of the second core slab (figure 19)but over predicts the cooling of the core particularly atthe top (for similar reasons to those described above forthe high heatup rate). The code then correctly predicts asecond dryout of second core slab followed by rewetting ofthe whole core, from below, after accumulator injection.
(e) Accumulator Injection and Core Rewetting. Accumulatorinjection commenced at t- 5538s in the experiment and at t-5501s in the RELAP5 simulation. Injection was initiatedwhen the primary system pressure fell to the set-pointpressure of 2.84 MPa.
The measured and calculated accumulator flows are shown infigure 24. The calculated accumulator flow is highlyoscillatory, although the oscillations did not lead totermination of the calculation, as occurred in the analysisof [1]. The calculated mean injection flow-rate isconsiderably higher than the measured value in the laterpart of the transient. This appears to be due to an over-prediction of the rate of steam condensation in the injectedwater, which leads to a calculated primary systemdepressurisation rate which is higher than that observed.Accumulator level is shown in figure 25.
7.
4.3 COMPUTING TDIE
The total problem time simulated was 7009s. The maximum andminimum time-step sizes were 0.1 and 10- s respectively. The rateof CPU time to problem time was 3.5 on the Harwell Cray-Icomputer.
5. DISCUSSION
In this section the RELAP5/MOD2 calculation is compared with theRELAP5/XODI analysis discussed in [1]. There were seven areas identifiedin [1] where RELAPh/MODI. did not perform well. Here each area is examinedin turn to determine whether or not the new code RELAP5/XOD2 producesimproved results.
(a) Steam Generator Separator
In the RELAPh/XODI calculation in reference [1] a mass/energyconservation error occurred in the SG separator/lower separatorregion. To alleviate this problem the junction between the lowerseparator and the separator bypass was disconnected. This courseof action was not found to be necessary in the MOD2 calculation.It was found, however, that in order to maintain the desiredseparator level it was necessary to increase the downcomer levelarbitrarily, from the measured value of 3.16m, to 3.7m. Discussionwith the code developers suggests that the desired result couldalso have been achieved by adjusting loss coefficients and frictionfactors.
(b) Mass Errors
At the end of the transient the mass error was approximately 12 kgwhich is 0.87% of the minimum inventory. This is a negligibleerror and is a major improvement over the MODI calculation wheremass errors reached 100 kg.
(c) Steam Generator Level Oscillations
As in the MODI calculation, oscillations were observed in the SGlevel throughout the transient. In the MOD2 calculation, theoscillations are present but are of much reduced amplitude.
(d) Accumulator Injection
As in the RELAP5I/1ODJ calculation the accumulator injection flow-rate was calculated to be more oscillatory than measured.Eventually the oscillations caused a water property error whichled to the termination of the calculation. The RELAP5/MOD2calculation did not terminate in the accumulator injection phase.
(e) Water Distribution and Inventory
RELAP5/MOD2.predicted fluid densities well; the problem identifiedwith the RELAP5/MODl code in which water was predicted to risefaster than steam in the core outlet region, was not seen in thenew calculation. The calculated primary inventory was in excellentagreement with the experiment, and showed a marked improvement onthe MODI calculation. (see figure 9).
8.
(f) Steam.Generator Heat Transfer
As found with the MODI analysis, RELAP5/',OD2 calculated low SG heattransfer in steady state, and once again failed to predict thecomplex effects thought to be present after core dry out i.e.continued reflux condensation when primary pressure is belowsecondary pressure. It is possible that inclusion of a small nodeat the bottom of the SG riser would enable the code to model thisbehaviour. The code did however go on to predict restoration ofreflux cooling and the feed and bleed phase, reasonably well.
(g) Core Heat Transfer
As with the RELAP5/MOD1 calculation, RELAP5/MOD2 under-predicted core heat transfer after dryout and predicted a morerapid quench than measured. In section 4.2(d) it is argued that amulti-channel core representation would be required to permit thecode to adequately model these effects.
9.
6. CONCLUSIONS
This report describes a RELAP5/iOD2 calculation of LOFT test LP-SB-03,which simulated a 0.4% cold leg loss of coolant accident (LOCA) in a PWR.
RELAP5/X.OD2 calculated all the thermal-hydraulic phenomena exhibited inthe test, in the correct order and with reasonable timing. Nodiscrepancies were seen in this analysis which are expected to be ofsignificance for reactor small break LOCA calculations.
RELAP5/MOD2 performed better than the RELAP5/MODI code which waspreviously used by GDCD for analysis of this test. In particularRELAP5/MOD2 was found to be more stable and robust, with an improvednumerical solution scheme removing the mass error problems encountered inthe earlier code version.
The present calculation was submitted to the OECD LOFT program reviewgroup as the United Kingdom contribution to the code comparison report fortest LP-SB-03. It will also form part of a validation report tounderwrite use of RELAP5/MOD2 by GDCD for analysing Sizewell 'B' smallbreak LOCA sequences.
10.
REFERENCES
I . GD/PE-N/482 Post test analysis of OECD LOFTexperiment LP-SB-03 usingRELAPS/MODI. Volume 1 Analysis,Volume 2 Figures.C Harwood Feb. 1985
2. OECD LOFT-T-3603 Best estimate prediction for OECDLOFT project small cold leg breakexperiment LP-SB-03W H Grush, H Tanaka, P Marsili
Quick Look report on OECD LOFTexperiment LP-SB-03H Tanaka et al.
Feb. 1984
3. OECD LOFT-T-3604
4. NUREG/CR-4312EGG-2396
Mar. 1984
RELAP5/M0D2 Code ManualVols. 1 and 2V H Ransom et al. Apr. 1984
5. RELAP5/MOD2 input data deck forSizewell 'B'C Harwood
C~J11OO1R6KEL/GB1
11.
Table I
Comoarison of RELAP Steady Statefor MODI and MOD2 with measured Data
II Variable 'Units' Measured MOD2 2 MOD i
IIPrimary
IPressuriser pressureIPowerlIntact loop mass flowIPressuriser levelICold leg temperature[Hot leg temperature
IBreak openedIScramIPrimary coolant pump tripIStart of core heatupIBreak isolatedISG feed and bleed initiatedlAccumulator injectionICore quenchedILPISI
I Measured I MOD2 MODM [(1]time (s) time (s) time (s)
0 0 09.21 + .011 11.525 10.6
11600 +2 11660 156513800 • 50 *I 4385 380014742 T 2 15085 462715415 + 5 15308 487815558 + 3 15501 509915800 + 50 I 5650 520016785 +2 16285I II
12.
C,11001.R6KEL/GB1.
LIST OF FIGLRES
.Steady State RELAP5 Results
1.2.3.4.5.6.7.8.
Primary PressureActive loop mass flowInactive loop mass flowHot and cold leg coolant temperaturesPressuriser level and surge line flowSteam generator level and pressureSteam generator steam and feed flowSG separator steam, liquid return, and mixture inlet flows
Transient Comparison of RELAP5 with experiment
9. Primary system coolant inventory10. Break flow11. Primary and Secondary pressure (RELAP)12.13.14.15.1617.18.19.20.21.22.23.24.25.26.
Primary pressureSecondary pressureBreak line densityCold leg densityHot leg densityLoop seal downside dClad temperatureClad temperatureClad temperatureClad temperatureClad temperatureClad temperatureAccumulator flowAccumulator levelRELAP5 noding scheme
FIGuRE a LP-SB-03 RELAPS/IOD2 atoadUj st.ate .alculaton.
4945. ................ ........... ............ ............... . . . I848 ................. ................ I ..............j ................ ............................... t ................ .8........4...... "483 .......... ................ I ................ !. ......................... t...................................................! ................ !. .......... -u48iI I I ,
4 a ........ ........ ,...... ......... i ................ ............... ÷ ....... ...................... •................ ................ i ...... ......... i ....... ........ .4823- .... ..................................-.................................................... o ...
124- ................ .................................................. I ................................................................. I ................ I ................. 1
2a -1l ......... ........ I.........
2e- ................. .................
................
................
......... I ........ 4 .............. ...................... ......... Iaa
................ .................
Z JUIIW
ai2I4I) 60 BeI ISOa--
Time (a)AP
Steam generator ateam and food ftow.
FIGUE
280-1.
aI I ~LP-SD-83 RELAP541ODi2 stoadU staite catculation.OA I.................................. .... ................................. ................
.......... ...... ............ . .... .............I- t --t r -' l jr ........... ..... .............. I ........... : ............ ...... • ..... .- ..z u• .amu t .• . ....I C l..... ...........
S,..I.. ......
. ..s . R I . ....... ........... ........ ........... ............. . ....
.............. ... .... ..... .. ......... . . ........I................1*.........I..............I.................. ..... I ..... ........... ....... ........ o....I .. ......... !. o .... .... ," r ... ... ... .............. ....................... ...... ................ .i~EE L I ,,-'[ I1RELAP
,, . ..-........................! ......I..................! ............. .... ............... I. " i .............. i ....................... .....................
AC11 .l I , :
.•' ................. ............ ... Acc... . ..- 4 .. ...IR + .I / i I a
TEP23000 "" T/4114.. ......F - , le l
.................I ........... .. a................. i ..................... t.............. i.................................
Figure 2&, LOFT RELAPS nodal Izatlon for Experiment LP-SB-3.
NPAC FORM 2326 UIL WiCLIAR 049GULAYO04Y COAMIIIO4N I m1PORT NUvmiER 1A.4..ev IioC.. W VaE I . *efti
(2641i4ACM 1102.r
3201.3202 BIBLIOGRAPHIC DATA SHEET NUREG/IA-0013SEE INSTRUCTIONSOf T-E REVERIA GD/PE-N/5352 TITLE ANO SUII TITLE J LEAVE ,LANK
RELAP5/MOD2 Calculation of OECD-LOFT Test LP-SB-034 OATE REPORT COMPLETED
MONTH I YEAR
, Au*NR,,, May 1987
C. Harwood, G. Brown , 4DATiERERTIUAOJanuary 1 1990
7 PERFORMING ORGANIZATION NAME AN° MAILING AOORESS JIkN*ZV ChJ/ B, PR CTTA-TRNWORAK UNIT NUMBER
Central Electricity Generating BoardBarnett Way, Barnwood I FINORGRANTNUMERGloucester, GL4 7RSUNITED KINGDOM
SO. SPONSORING ORGANIZATION NAME ANO MAILING AOORIESS (In¢eftleA. C44 1la. TYPt OF REPORT
Office of Nuclear Regulatory ResearchU.S. Nuclear Regulatory Commission Technical ReportW a s h i n g t o n , D C 2 0 5 5 5 . PERiOOCOV E RO ,,-1 ..a -a
12 SUPPLEMENTARY NOTES
13. ASISTRqAT 170-1 WA
This report compares the results of theexperimental measurements.
RELAP5/MOD2 analysis with
A simulation of test LP-SB-03 was previously carried out at GDCD using theRELAP5/MOD1 code. RELAP5/MOD2 was developed from RELAP5/MOD1 and containsmore sophisticated hydraulic models and constitutive relationships.Comparison of the RELAP5/MOD2 and MOD1 calculations show that RELAP5/MOD2performs better than RELAP5/MOD1 in a number of key areas; notably masserrors are much reduced, there is improved numerical stability, andimproved separator modelling and modelling of accumulator injection.
I4 OOCLMINT ANALYfSIS 4 REYWOROSOASCRIPTORS IS AVAI,.AiLAiTY
RELAP5/MOD2, ICAP Program, Small Break, LOFT STATEMENT
UnlimitedII SECURITY CLASSIOICATION
6 JOE NTIFII .RASIOIN.EO TERMS G c"Tassi fiedr'crassified
II NUMBER Of PAGES
Is PRICE
UNITED STATESNUCLEAR REGULATORY COMMISSION
WASHINGTON, D.C. 20555
OFFICIAL BUSINESSPENALTY FOR PRIVATE USE, $300
SPECIAL FOURTH-CLASS RATEPOSTAGE & FEES PAIDU USNRC j
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