fILLs

* -. NUREG/IA-0021

Intemational

Agreement Report

RELAP5/MOD2 Calculations of

OECD LOFT Test LP-SB-2

Prepared by

P. C. Hall

Central Electricity Generating Board

Generation Development & Construction Division

Barnwood, Gloucester GL4 7RS

United Kingdom

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

April 1990

Prepared as part of

The Agreement on Research Participation and Technical Exchange

under the International Thermal-Hydraulic Code Assessment

and Application Program (ICAP)

Published by

U.S. Nuclear Regulatory Commission
NOTICE

This report was prepared under an international cooperative

agreement for the exchange of technical information; Neither

the United States Government nor any agency thereof, or any of

their employees, makes any warranty, expressed or implied, or

assumes any legal liability or responsibility for any third party's

use, or the results of such use, of 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.

Available from

Superintendent of Documents

U.S. Government Printing Office

P.O. Box 37082

Washington, D.C. 20013-7082

and

National Technical Information Service

Springfield, VA 22161
NUREG/IA-0021

International

Agreement Report

RELAP5/MOD2 Calculations of

OECD LOFT Test LP-SB-2

Prepared by

P. C. Hall

Central Electricity Generating Board

Generation Development & Construction Division

Barnwood, Gloucester GL4 7RS

United Kingdom

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

April 1990

Prepared as part of

The Agreement on Research Participation and Technical Exchange

under the International Thermal-Hydraulic Code Assessment

and Application Program (ICAP)

Published by

U.S. Nuclear Regulatory Commission
NOTICE

This report is based on work performed under the sponsorship of the

United 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 th'e 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 USNRCI 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.
GD/Pt-N/606

Abstract: To help in assessing the capabilities of RELAP5/MOD2 for PWR

Fault Analysis, the code is being used by CECB to simulate

several small LOCA'and pressurised transient experiments

in the LOFT experimental reactor. The present report describes

an analysis of small LOCA test LP-SB-02, which simulated a 1%

hot leg break LOCA in a PWR; with delayed tripping of the

primary coolant pumps. This test was carried out under the

OECD LOFT Programme.

An important deficiency identified in the code is inadequate

modelling of the quality of the fluid discharged from the hot

leg into the break pipework. This gives rise to large errors

in the calculated system mass inventory. The effect of using

an improved model for vapour pull-through into the break is

described.-

A second significant code deficiency identified is the failure

to predict the occurrence of stratified flow in the hot leg at

the correct time in the test. It is believed that this error

contributed to gross errors in the loop flow conditions after

about 1300s.

Additional separate effects data necessary to resolve the code

deficiencies encountered are identified.

i.
Executive Summarv:

The RELkP5/MOD2 transient thermal-hydraulics computer code is

being used by CEGB for calculation of small break loss of

coolant accident (LOCA) sequences for Sizewell 'B'. To asist

CEGB in assessing the capabilities and status of this code, it

has been used to simulate SBLOCA test LP-SB-02 carried out in

the LOFT experimental reactor under the OECD LOFT programme.

This test simulated a 1.0% hot leg break in a PWR, with delayed

tripping of the primary coolant circulating pumps. This report

compares the results of the RELAP5/MOD2 analysis with

experimental measurements, and with published analyses using

earlier versions of RELAP5.

Overall agreement between calculated results and experimental

data was reasonably good for the first 1200s of the transient,

but was unsatisfactory at later times. The principle

deficiencies identified in the code were as follows:

(a) In common with previous analyses of Test LP-SB-02 using

RELAP5/MODI, RELAP5/MOD2 failed to predict the onset of

stratified flow in the hot leg at the correct

conditions.

(b) The test data show that fluid quality in the offtake pipe

leading to the break orifice was significantly higher t•han that in the hot leg. The RELAP5/MOD2 horizontal

stratification entrainment (HSE) model, designed to model

this effect, failed to predict the correct behaviour in

this test. A modified code version incorporatiig

improved correlations for the quality in the offtake pipe

was found to produce markedly more accurate results.

(c) Large errors in calculation of the loop flow were

encountered in the later part of the experiment. The

most likely cause of these errors is thought to be the

failure to calculate the correct flow regime in the hot

leg, noted in (a) above.

To assist in developing code models which will give improved

agreement with similar experiments, further separate effects

experimental data are desirable on the following:

(a) Transition to stratified flow in geometries resembling a

PWR hot-leg.

(b) Flow quality in a offtake pipe connected to a larger

horizontal pipe in which there is a two-phase flow with a

mass velocity of more than 1000 kg m-2s 1 .

Experiments designed to provide this information are currently

in preparation at AERE, Harwell.

ii.
TABLE OF CONTENTS

Abstract

Executive Summary ii

Contents iii

1. Introduction 1

2. Description of Test 1

3. Code Version and Input Model 1

4. Initial and Boundary Conditions 2

5. Base Case Calculation 3

6. Calculations Using Modified Code Version 4

6.1 Description of the Modified Horizontal Stratification 4

Entrainment Model.

6.2 Comparison of results of the modified code with 5

experimental data.

7. Discussion and Comparison with Previous Analyses 7

8. General Code Performance and cpu Time. 8

9. Conclusions 8

10. References 9

Table 1 - Initial Conditions for LP-SB-2 11

Table 2 - Sequence of Events for LP-SB-2 Calculation 12

Appendix 13

iii.

1. INTRODUCTION

The RELAP5/MOD2 code [E] is in use by CEGB for calculating Small-Break

Loss-of-Coolant-Accident (SBLOCA) and pressurised transient sequences

for the Sizewell 'B' PWR. RELAP5/MOD2 uses a six-equation two-fluid

model to describe two-phase flow in the reactor primary and secondary

systems. It supersedes the RELAP5/MODI code, which employed a

five-equation model (one-phase constrained to be at thermal equilibrium)

and used less sophisticated models for flow regime transitions and

interphase interaction terms.

To assist in assessing the capabilities and status of RELAP5/MOD2, the

code is being used by GDCD to simulate several small LOCA and pressurized

transient experiments carried out, in the LOFT experimental reactor under

the OECD LOFT programme (2, 3, 4]. The present report describes an

analysis of small LOCA test LP-SB-02, which was part of this test series.

Test LP-SB-02 simulated a 1% hot leg LOCA in a PWR with a delay of

approximately fifty minutes in tripping the primary coolant pumps. The

test is described in Refs. (5), [6] and [7].

Comparisons are given with earlier calculations of the same experiment

carried out with RELAP5/MODI, and described in Refs. (6], (8] and [9].

The effect of modelling changes introduced into the MOD2 code version are

highlighted.

2. DESCRIPTION OF TEST

The sequence of key events is given in Table 2. The transient is briefly

described as follows. The test was initiated by opening the break (time

zero) and isolation of the steam generator was initiated at SCRAM, l.8s

later. High Pressure Injection (HPI) flow and auxiliary feed to the

steam generator were initiated at 42s and 64s respectively. At about

600s the pump head degraded sharply and there was evidence of flow

stratification in the hot leg. However, the pumps maintained a flow

circulation round the loop up to 1290s. Because of the complex effects

of the stratified flow, the density of fluid entering the break line was

systematically lower than the density of the fluid in the hot leg for

most of this period. At about 1200s the entrance to the break line

became completely uncovered, leading to an increase in the

depressurization rate. HPI flow matched break flow at about 2300s and

pressure fell steadily to the set point of 3.16MPa when the pumps were

tripped (approximately 2900s). Pump trip caused minor changes in

differential pressure and water distribution, but had no significant

effect on break line density or break flow. The test was terminated at

6810s.

3. CODE VERSION AND INPUT MODEL

The basic code version used for this calculation was RELAP5/MOD2 cycle

36.04, with several error corrections (primarily Cray conversion errors)

implemented by UKAEA, Winfrith. The semi-implicit numerical scheme was

used throughout because code failure was found to result when use of the

nearly-implicit scheme was attempted.

The input data was based on that used in Ref [2] for the analysis of

LOFT cold leg break test LP-SB-01. Standard values of the single and

two-phase break flow multipliers, CDl and CD2 (0.93 and 0.81,

respectively) were used (e.g Ref. [10]).

1.
The noding diagram is shown in Figure 1. The model consisted of 120

volumes, 126 junctions and 125 heat structures. Junctions between the

hot leg and break line, and between the hot land cold legs and the vessel

were modelled as cross-flow junctions. This meant that relatively short

hydrodynamic-volumes were required in the hot leg and in the vessel upper

plenum and downcomer.

A microfiche listing of the code input and output has been filed under

Safety Technology Section in the Microfiche Archive at GDCD, Barnwood.

4. INITIAL A.ND BOUNDARY CONDITIONS

To establish the required steady state, a pseudo-transient calculation

was run until the problem time reached lO0s, when the code indicated that

a satisfactory steady state had been achieved. Parameters controlled to

achieve the desired steady state were steam and feed flow, and the pump

speed. A dummy time-dependent volume was attached to the top of the

pressurizer to maintain the desired steady primary pressure. After.l00s

these steady state controllers were all removed, the dummy volume

deleted, and the calculation allowed to proceed for 20s before initiating

the transient. Figures 2, 3 and 4 show the hot leg pressure, and

pressurizer level, the flows into and out of the SG separator, and the

steam generator pressure and level during the steady state run. The slow

fall in primary pressure after 100s shown in Fig. 2 is the result of heat

losses calculated from the pressurizer. These figures illustrate that a

satisfactory steady state was achieved.

The RELAP5 calculated steady state initial conditions are compared with

experimental values from Ref. [6] in Table 1. These can all be seen to

be in agreement, except for the steam generator (SG) secondary side

level, which had to be set artificially high in order to eliminate

periodic emptying and filling of the separator volume. This modification

was considered acceptable since in test LP-SB-02 the SG secondary plays

only a minor role in the overall primary system energy removal.

Boundary conditions used in the test were obtained from the EG&G data

package, Ref. [7).

The main primary circuit system (PCS) boundary condition was the High

Pressure Injection (HPI) flow. This was modelled as a table of flow

versus PCS pressure, rather than flow versus time. For the steam

generator secondary side, auxiliary feed-water flow rate was modelled

using a table of flow versus time, with flow being terminated 1800s after

trip. Also modelled was the brief opening of the steam bypass valve to

an area of 1.28.10-4m2 when SG pressure first exceeded 6.5 MPa.

As in previous analyses of SBLOCA in LOFT (e.g, [3]), it was found

necessary to model steam generator leakage in order to obtain reasonably

accurate calculations of secondary pressure. The existence of leakage

in test LP-SB-02 is confirmed by the observation of a falling liquid

level after auxiliary feed was terminated. Acceptable results were

obtained when the leakage was modelled by setting a minimum flow area for

the Main Steam Control Valve of 2.0.10"3m2 .

2.
5. BASE CASE CALCULATION

This section briefly describes comparison of the test results with

predictions obtained using the standard version of RtELAP5/MOD2, cycle

36.04. Key results are illustrated in figures 5 - 8; solid lines

represent the experimental data and broken lines represent the RELAP5

calculations.

(a) Primary pressure.

Figure 5 shows that agreement between measured and calculated

primary pressure is reasonably good until about 1200s. Also,

beyond 1900s, the depressurization rate is accurately calculated.

However, in the period 1200-1900s, there are significant errors in

the calculated depressurization rate, leading to a systematic

overprediction of pressure in the long term transient. Because of

this pressure offset, the time of pump trip is overpredicted

(approximately 4150s, rather than 2853s).

(b) Break flow rate.

Figure 6 shows the measured and calculated mass flow rate in the

break nozzle. Before about 800s, the break flow rate is

underestimated by about 15%. Subsequently it is overestimated by

up to 50%, leading to large cumulative errors in system mass

inventory. The overestimate in break flow is believed to arise

from errors in the calculated conditions in the break line, as

described in (c) below. In spite of the underestimation of system

inventory, the calculation correctly predicted that no dryout

occurred in the core.

In the early part: of the calculation, prior to 250s unrealistically

sharp steps in the break flow rate are evident. Similar behaviour

was observed in previous RELAP5 calculations of subcooled and low

quality discharge, e.g. Refs. (2, 3 and 9].

(c) Hot leg and break line density.

The hot leg density (Figure 7) is seen to be reasonably accurately

calculated until about 1400s: thereafter large errors occur.

Figure 8 shows the measured and calculated fluid density in the

break line. A large systematic overestimate is seen despite the

fact that the hot leg density is well predicted until about.1400s.

This discrepancy is believed to be responsible for the prolonged

overestimate of discharge flow rate noted in (b) above.

The results summarised above indicate reasonably accurate calculation of

the transient up to about 1200s, with increasing errors thereafter. The

primary source of the errors is evidently the failure to calculate the

correct relationship between the density in the hot leg and break line.

Similar discrepancies in the break line density were found in

RELAP5/MODl analysis of LOFT test LP-SB-02 reported in Refs. (6] and

[9]. The authors of Ref. (6] attributed the error to the effect of flow

stratification in the hot leg, which caused a preferential discharge of

vapour into the break line T-junction.

3.
Unlike RELAP5/MODI, RELAP5/HOD2 contains a special purpose model (the

horizontal stratification entrainment model) designed to correct the void

fraction donored to an off-take pipe for the effects of flow

stratification in an upstream horizontal volume. However, this model is

invoked only when the horizontal stratified flow regime is calculated to

occur in the upstream volume. For the forced circulation conditions

calculated to exist in test LP-SB-02, REI.AP5/MOD2 predicted the slug or

annular mist flow regimes to persist in the hot leg until about 2250s.

However, in the test, stratification in the hot leg began to occur at

about 600s when the pump head degraded [6]. Therefore, the RELAP5/MOD2

horizontal stratification model was not applied during the appropriate

phase of the test. In consequence results were similar to those of

Ref. [6] obtained using RELAP5/MOD1.

To investigate this effect further the test was recalculated with a

modified version of RELAP5/MOD2 containing an improved horizontal

stratification entrainment model, which is applied at high mass

velocities. Calculations with the modified code version are described in

the next section.

6. CALCULATIONS USING MODIFIED CODE VERSION

As noted in the prev ious section, a revised horizontal stratification

entrainment model has been developed and included in a modified version

of REIAP5/MOD2. This section briefly describes the model and goes on to

compare calculations performed using the modified code with the data from

test LP-SB-02.

6.1 Descrintion of the Modified Horizontal

Stratification Entrainment Model

In the standard version of REIAP5/MOD2 the void fraction at a

junction connected to a horizontal pipe containing stratified flow

is calculated from an algebraic expression involving the void

*fraction" in the donor volume, the phase velocities in the junction

and*thermodynamic and 'geometric properties.' The equation is

intended to model the effects of flow stratification and

vapour/liquid pull-through on the flow in the side branch. The

model is applied only when stratified flow is calculated in the

_donor volume: in other flow regimes the junction void fraction is

taken as the donor volume void fraction.

In the modified code version [11] the junction void fraction is

calculated from the expression:

S(1-Xj)pg "g,j/(xj Pf q Uf'j) )

where the subscript j refers to Junction properties. The junction

quality Xj is calculated from the empirical correlation given by

Smoglie [12] based on air-water test data.

This method of calculating aj is used at mass velocities in the

main pipe below 2500kg mzs-1. For mass velocities above 3000kg m"

2sl the Junction void fraction is taken simply as the donor void

fraction.+ In between'these limits linear interpolation is used.

+ The mass velocity 3000 kg m12 s"1 corresponds typically to the transition

to the dispersed flow regime, in which effects of gravitational

separation may be expected to be small.

4.
The modified code version has been found to give much improved

agreement with separate effects test data on two-phase flows in

horizontal T-junctions in which there is stratified flow in the

main pipe, [11]. However, it should be noted that no test data are

available to confirm the modelling approach when there is high mass

velocity (exceeding 1000kg m" 2 s-1 in the main pipeý Further

experiments are desirable to support the use of the.model for these

conditions.

6.2 Comparison of results of the modified code with exDerimental data

The results of the calculation with the modified code version are

presented in figures 9 - 17. Experimental data are shown as solid

lines and modified code calculations as chain-dotted lines. The

timing of key events is given in Table 2. Results are described

below:

(a) Primary pressure.

Figure 9 shows that the code modifications described above

have little influence on primary pressure until about 1000s

because the mass velocity does not fall below the 3000kg

m. 2 s"1 limit until about 800s. Thereafter the modified

horizontal stratification entrainment model has the effect of

increasing the discharge enthalpy which increases the

depressurization rate. The relatively rapid drop in pressure

which occurred in the test between 1250s and 1750s is not,

however, correctly predicted. Failure to predict this feature

leads to a delay of about 700s in the calculation of the time

of pump trip. This remaining error is discussed further

below.

(b) Break flow rate and primary system mass inventory.

It can be seen from figure 10 that modified code produces a

much improved calculation of break flow rate from 800s

onwards..

Figure 11 shows primary coolant system mass inventory. As

expected, the improvement in accuracy of the calculated break

flow leads to more accurate calculation of the system mass

inventory, particularly later in the transient.

(c) Hot leg and break line density.

The prediction of the density in the hot leg after 1500s is

considerably improved in the calculation with the modified

code (Figure. 12). This is a consequence of more accurate

calculation of the discharge flow rate. The fluctuations in

calculated density arising at about 3600s are caused by the

pump trip.

Figure 13 shows measured and calculated break line density.

As expected the modified code version gives a major

improvement beyond about 800s. Agreement with experimental

data is reasonably. good thereafter, except for the period

1250-2000s, Calculated errors in thisiperiod evidently

arise primarily from errors in the calculated liquid

inventory of the hot leg (see Figure 12).

5.
(d) Secondary pressure.

Figure 14 shows a comparison of measured and calculated

pressure in the SG secondary. Reasonable agreement is

demonstrated, but this is to a large extent due to the tuning

of the calculated leakage through the main steam control

valve, described in Section 4.

(e) Loop behaviour.

Measured and calculated coolant velocities in the-hot leg are

shown in Figure 15. Measured data are from two turbine flow

meters situated towards the top and bottom of the hot leg.

The upper meter can be seen to uncover and show increased

(steam) velocity at about 1lOOs (see ref [5]). The lower

(liquid) velocity continues to fall, indicating complete flow

stagnation at about 2000s.

The calculated results are significantly different,

indicating continuing loop flow at velocities of 4-6ms" 1

until pump trip.

A second important error is in the calculated flow regime in

the hot leg. The 3-beam gamma-densitometers in the hot leg

indicate a sharp increase in the vertical void gradient

about 600s (Ref. [6]). The existence of fully stratified

flow in the hot leg at 1l00s is confirmed by the sudden

increase in the velocity measured by the upper turbine flow

meter, see figure 5. In the calculation using the modified

code version'stratification in the hot leg was not predicted

until pump trip.

Surprisingly the observed occurrence of fully stratified flow

in the hot leg at about il00s took place at a mass velocity

of approximately 1800 kg m-2 s"1 , almost an order of magnitude

above the normally expected upper limit for the existence of

stratified flow, e.g [1].

Additional evidence indicating errors in the calculated loop

flow conditions is shown in Figure 16. This figure shows

measured "and calculated coolant densities in the loop seal,

just below the SG discharge. Virtually no water leaves the

SG beyond 1500s. In contrast, the calculated results show

very similar densities in the loop seal (Figure 16,) cold leg

(Figure 17) and the hot leg (Figure 12).

In summary, the experimental data indicate that forward flow of

liquid around the loop fell sharply after about 1300s, when most of

the-water drained from the hot and cold legs. RELAP5/MOD2

predicted a continuation of forced circulation of liquid around the

loop until the time of pump trip (3580s). Therefore, throughout

the primary coolant system, detailed flow conditions calculated by

the code were in error after about 1300s.

6.
Sensitivity calculations were carried out in an attempt to identify

the source of the error in the calculated loop flow-rate after

about 1300s. These are described in Appendix 1. The sensitivity

calculations included changes to the noding of the steam generators

and hoc legs and changes to the assumed pump characteristics. None

of the revised calculations satisfactorily reproduced the

experimental behaviour.

7. DISCUSSION AND COMPARISON UqTH PREVIOUS ANALYSES

Test LP-SB-02 has been analysed previously with the code RELAP5/MODI

[6, 8, 9]. In these calculations a significant overprediction of the

break line density was also observed. This was attributed to failure to

model the effect on the break flow of stratification in the hot leg,

since RELAP5/MODl.did not contain a Horizontal Stratification Entrainment

(HSE) model describing this effect.

The released version of RELAP5/MOD2 gives similar results to those

obtained-previously with RELAP5/MOD1, indicating that the HSE model in

RELAP5/MOD2 is ineffective in describing the flow separation observed in

this test. Considerably improved agreement is however obtained with the

code version containing the modified horizontal stratification

entrainment model. Contrasting the two models, it is concluded that the

main defects of the HSE model in the released version of the code are as

follows:-

(1) failure to model effects of flow stratification at high mass

.velocities;

(2) inaccurate calculation of fluid quality in the side branch for

stratified flow conditions.

The second major error observed in the RELAP5/MOD2 calculations was the

failure to calculate rapid reduction-in the forced circulation of liquid

after about 1300s. Similar difficulties were encountered in the earlier

RELAP5/MODl analyses, e.g [9]. Several sensitivity calculations were

performed as part of the present analysis to try to trace the source of

this error (see Appendix 1 for details). These included changes to

noding of the steam generators and hot legs, and reductions in the

assumed fully degraded pump heat characteristic. None of the additional

calculations satisfactorily reproduced the measured liquid flow

characteristics.

It is concluded that- the error is probably connected with the failure of

the code to correctly describe the flow regime in the hot legs. As

discussed in the previous section, data from the turbine flow meters and

gamma-densitometers indicates that the flow regime in the hot leg became

fully stratified at t - ll00s, whereas stratified flow was not calculated

to occur until much later (Table 2). It is likely that the error in

identifying the flow'regime leads to an overestimate of the interphase

drag forces in the hot legs; this probably causes an erroneous prediction

of continued forced circulation of liquid in the loop.

Further experiments on flow-regime transitions in representative

geometries would assist in confirming this hypothesis.

7.
8. GNEtrAL CODE PERFORMA. CE -AND CPU TIME

In the present calculations the code was found to be robust, stable and

subject .o negligible mass conservation errors. For the released code

version,.,cpu:°real time ratio was 2.76:1 on a Cray XMP computer. The

calculation with the.modified code version -ranslightly more quickly.

The cpu time per mesh cell was 6.58ms.

The cpu:real timb ratio was about three times slower than that'?

experienced in the Ref. [2] analysis of test LP-SB-01. This was: because

the higher fluid velocities in the loop, which arose as a result .of

delayed pump trip, led to the computational time steps being limited by

the Material Couran: Limit (MCL). The MCL restriction occurred in the

shortest volumes, 104 and 184, which are used for the modelling of Tees'

with the cross-flow Junction option and have a length to diameter ratio

of unity in accordance with EG&G guidelines [12]. To investigate the

need for restricting the length of these volumes, a sensitivity study was

carried out in which the length of volumes 104 and 184 was increased by a

factor of about 2.5. This change 'resulted in an increase in execution

speed-of x 1.8, yet the results were effectively identical. This

observation indicates that the guideline for modelling Tees which

requires the use of very short volumes may be unnecessarily restrictive

when using the semi-implicit numericalintegration scheme in

RELAP5/MOD2.•

1. This report has describe'd.the results of a EAP5/MOD2 . calculation

of OECD LOFT Test LP-SB-02; which simulated a 1% equivalent area

hot leg loss of coolant accident with delayed trippingof.the

primary coolant pumps.

2. Overallagreement between calculated results and experimental data

was reasonably good for the first 1200s of the transient, but was

unsatisfactory at later times. .The principle deficiencies

identified in the code we're as follows:."

(a) In common withprevious 'analyses of Test LP-SB-02 using

REIAP5/MODI, RELAP5/MOD2 failed-tdpredict the onset of

,.stratified flow in the hot leg at the correct conditions.

(b) The test data show that fluid quality in the offtake pipe,...

leading to the break orifice was iignificantly higher than

that in the hot leg. The RELAP5/MOD2 horizontal

stratification entrainment (HSE) model, designed to model

this effect, failed to predict the correct behaviour in this

test. A modified code version incorporating 'improved .

correlations for the quality in the offtake pipe was found

to produce markedly more accurate results.

(c) Large errors in calculation of the loop flow were encountered

in the later part of the experiment. The most'likely cause

of these errors'is'thought to be the failure to calculate the

correct flow regimein the'hot leg, noted in (a) above.

3. To assist'in developing code models which will give improved

agreement with similar experiments, further separate effects

experimental data are desirable on the following:

8.
(a) Transition to stratified flow in geometries resembling a PWR

hot-leg.

(b) Flow quality in an offtake pipe connected to a larger

horizontal pipe in which there is a two-phase flow with a

mass velocity of more than 1000 kg m- 2 s".

Experiments designed to provide this information are currently in

preparation at AERE, Harwell.

10. R

1. NUREG/CR-4312

2. GD/PE-N/544

3. GD/PE-N/535

4. GD/PE-N/597 Draft

PWR/HTWG/P(87)497

5. OECD LOFT-T-3304

RELAP5/MOD2 Code Manual

Volumes I and 2

V.H. Ransom et al.

RELAP5/MOD2 Calculations of

the OECD LOFT Test LP-SB-01.

P.C. Hall and G. Brown.

RELAPS/MOD2 Calculation

of OECD LOFT Test*LP-SB-3.

C. Harwood, G.Brown

RELAP5/MOD2 Calculation of

OECD LOFT Test LP-FW-0O.

M.G. Croxford and C. Harwood.

Dec. 1985

November 1986

April 1986

May 1987.

Quick-Look report on

OECD LOFT experimeht

LP-SB-2.

S.M. Modro. August 1983

6. OECD LOFT-T-3205

7. OECD-LOFT

Experiment LP-SB-2

8. PWR/LCSG/P(83)58

Experimental analysis

and Summary report on

OECD LOFT nuclear

experiments LP-SB-1 and

LP-SB-2.

S.M. Modro etal.

Tape Descriptions and

Supplementary Information:

EG&G (Idaho) Inc.

Blind Calculations of

LP-SB-l and LP-SB-2 Using

RELAP5/MOD1/C19/WIN 001'.

C.G. Richards.

RELAP5/MOD1 Calculations

of the OECD LOFT LP-SB-1 & 2

Small Hot-Leg Break

Experiments.

A.J. Clare.

May 1984

1983

1983

9. *TPRD/B/0679/NS5

July 1985

9.
10. OECD LOFT-T-3303

11.

Best Estimate Prediction

for OECD LOFT Experiment

LP-SB-2.

T.H. Chen, S.M. Modro.

Assessment of Horizontal

Statification Entrainment

Model in RELAP5/MOD2.

Unpublished CEGB Report.

K.H. Ardron and W.M. Bryce.

Notes of RELAP5/MOD2

Workshop, Wurenlingen,

Switzerland.

EG&G (Idaho) Inc.

June 1983

Unpublished CEGB

report.

August 1987

12. 1985.

10.
Initial Conditions for LP.SB-02

Experiment REIAP5*

Cold Leg Temp. (K)

Mass Flow Rate (kg/s)

Core Temp Rise (K)

S.C. Secondary

Liquid Level (m)

Pressure (MPa)

Mass Flow (kg/s)

Pressuriser

Pressure (MPa)

Liq. Level (m)

Core Power (<M)

HPI Temp. (K)

557.2±1.5

480.0±3.2

18.6±1.7

3.13±0.1

5.60±. 05

26.70±0.8

15.08±0.16

1.109±.003

49.1±1.2

306±7

559.2

480.1

18.9

3.70

5.61

25.66

15.06

1.135

49.1

306

* End of Null Transient.

11.
Secuence of Events for LP-SB-02 Calculation

Time After Break Open (s)

Event III II

I Experiment I RELAP5/MOD2 I Modified

S I I• Code

________________________________1_______ 1 I_ ________ _ _ _ _ _ _

Small-Break Valve Opened

Reactor Scrammed

Main Feed-water Shut Offý

Main Steam Control.Valve Started to

close

Main Steam Control Valve Fully Close,

Pressurizer Liquid Level Below Botto:

HPIS Flow Initiated

Subcooled Blowdown Ended (break line

fluid reached saturation)

Auxiliary Feed-water Initiated

Onset of Stratification in Hot Leg

Stagnation of Liquid Flow in Loop

Primary System Pressure Became Less

than Secondary System Pressure

Auxiliary Feed-water Shut Off

HPIS Flow Rate Exceeded Break Flow

Rate

Primary Coolant Pumps Tripped

Calculation Termination

d

m

*1

.1

LI

II

I.

I.

0

1.8±.05

1.8±.02

2.8±0 .2

14.8±0.2

36.4±0.2

42.4±0.2

50.2±1.0

63.8+0.2

600

1290

1290±45

1864.0±0.2

2284±200

2852.8±0.2

0

4.27

4.27

5.28

20

38

43.7

53

66.3

-2250

pump trip

2650

1866

>4000 +

4152*

4000

0

4.27

4.27

5.28

I 20s

I38

43.7

53

66.3

pump trip

pump trip

2320

1866

1-2500 +

3580

4000

* Approx. value, based on preliminary calculation.

+ Time of minimum primary system inventory.

12.
APENDIX

. DescriDtion of Sensitivity Studies

The objective 6f-this'Appendix is to summarise the results of a number of

.'sensitivity calculations performed in an attempt to establish the cause

.of, the.failure of RELAP5 to predict the rapid riduction"in water flow in

the loop after about-1300.

The first possibility to be considered was that water was being

erroneously entrained into the Steam Generator (SG) either as a result of

overestimates in interfacial friction or because of failure to account

for separation in the hot leg/SG inlet elbow.

In calculating the interfacial drag at a jun tion, RELAP5/MOD2 averages

the values of drag derived in the adjacent volumes. It is therefore

possible for the averaging process to suppress the effect of a volume in

;which low interphase drag is calculated, if high interphase drag is

calculated in.both upstream and downstream adjacent volumes. Because the

SG' inlet plenum has :a large cross-sectional area relative to the two

adjoining volumes, it was considered possible that interphase drag within

the plenum was effectively-overestimated. To eliminate this possibility,

a sensitivity calculation was performed in which the SG inlet plenum in

the RELAP5 input model was split into two vertically stacked volumes. As

expected, the interfacial'drag at the newly created internal Junction was

lower than in the other junctions., and a noticeable amount of water was.

calculated to accumulate in the SG inlet plenum. However, this

•accumulation had only a transitory effect on.water flow into. the SG...:.

- :t tubes, and led to no long term improvement in the accuracy of the

calculation of liquid flow rate.

A second more speculative attempt to eliminate water. flow into the SG

tubes was made by invoking, the modified horizontal.stratification offtake model developed for the hot leg/break line at the junction between

the horizontal and inclined sections of the. hot, leg .This.again-caused,

sli-ght accumulation of water in the hot leg,'but produced no long term

improvement in calculated loop flow.

Finally, the pump"'degraded head data wai modified to reflect data

uncertainties. Figure Al shows the measured pump.differential. pressure,

compared with the value calculated using the modified version of the code

(chain-dotted line). This indicates that the calculation overestimates

theldata somewhat; To assess the sensitivity of the system to errors in

S... calculated pump differential pressure, a calculation as'perfoilmed in"

which'the fully .degraded pump head was reduced by about 30%. The

calculation began at 600s, continuing until '2500s. Results are also

shown on Fig. Al (broken line). Agreement with 'measurements is very good

in the critical period around 1300 - 1500s when loop water flow actually

ceased.

13.
The effect on calculated loop flow rates. is illustrated in Figure A2,

which shows measured velocities at the top and bottom of the hot leg

alongside liquid and vapour velocities arising from the two calculations

mentioned above. The effect of reducing the fully degraded pump

performance is to bring the calculated steam velocity into reasonable

agreement with measured values (top of hot leg) for long periods. In

spite of this, the water velocity does not fall to zero as measured, and

the erroneous calculation of circulation of a near homogeneous two-phase

mixture experienced in the previous calculations was maintained.

In this sensitivity analysis there were periods during which the hot leg

steam velocity (Fig. A2) and hot leg mixture density (Fig. A3) were

calculated correctly (750-1 4 00s, 2000-2500s). Nevertheless, the code

continued to calculate water flow along the hot leg and up the SG tubes.

This implies that the failure to predict cessation of loop flow was

probably due more to weaknesses in interphase drag calculation in the hot

leg/SG inlet than to errors in the assumed pump characteristics.

14.
"11P

IT- u

t"

U, z00XZP

r-0

'100

r'-

,--

I-'

"O0I

CO

I-

(-4

r-o

KEY.

12S COMPONENT

6 2 COMPONENT

PUMP

. BRANCH WITH JUNCTIONS

222 JUNCTION OR VALVE

HEAT STRUCTURE

-* CROSS flOW iIINIflTMN

STEAM GENERATOR

PRESSURIZER

.IS ...... 

. .... ..... TIO...

SiS

BREAK

REACTOR

VESSEL

17S

350

6_0

0o~

U'
LP-SB-02 STEAOY STATE

C" (2]

-I

3-1

£

U

2

W1

0,

U

B.

.1-------.................. .... ......

................. ................. ... . . .

.~~~ ~ ~ .. ..... ..... .... .............. .................. .............. ..............

146 La Nru

i .l it ............... ............ ..... ....... .......

:3 1.............................V 0 1 1 1 ...... .............. .................... ........

1.16

1.14

.12

3

.89

.06

1.04

5.m

111E IS)

6 20 4G s oS

P16661 Ell CIIT1LU.12 (21 -

Fictu•c) 2 HOT LEG PRESSURE AtMl PRESSURIZER LEUEL

int t20

T
LP-SB-82 STEADY STATE

................. ................ ............................ ....... -.j6

fo

0

J

i. IL,

Se .... .. ........... .. ........ .... . I58

flIGeim eEmu~tu FL&.j2

..... ..................................................... ........... ... .................

L ...... S-rcnnu rLou.

4 ., .4 . 4 1~

.0 20 40 Ge to * INe i 120

rTi (s,

111"OWU 0I861 t flLOIJ -"1.0tJ5688 -

fiGUIC3 STEAM GENERATOR SEPARATOR M1iSS FLOU RATES
LP-SB-02 STERDY STATE

hi

*1

hi

U.

6r

ru1t1 s

P-52 (11 - .. cntLualR l21 -

FIC&UCe + STEAM GEIERATOR PRESSURE AMI1 LEUIL
(L

0.

I.,

w

9L

RELnPS'rlOD2 CnLCULATION OF LOFT TE5'~ LP -SB-02

14 .1 ............ ......................... .................. ............ 

....... ................

1......... ..... .4.* 1

... .. . .. .. ... ... . .. .... . .... .. .. . ... ... .... .. . .

----------

0 Goo 10es 1500o 2•tl•B 0

iTs r "t"WXo

DATn C.DE

PE-PC-0I3 pl-oslP I

FIGURE : ME AESURED AND CALCULATED PREI'RY PRESSURES

me8 40011

UiflE (5)
RELflF'S/MOD2 CIILC[JLfI[IJM OF LOFT IESI LP-913-1-2

I ......................... . . . . . . ........ ........................................................................... ... . .. . . . . ........ . .. . .. . . .. .. . . . . . ... I

.l . ..................... ....................... .......................... '...................... ................................................ ................................................. II9

6 . ....................... ....................... ...................... ......................... I ....................... ....................... ....................... 4........................ .g

lx

42- .. . ... 

....-....... ............. ... .. 7... ................... . :

(Ia ..... Or .. ...... ..... .... ... ... ... ... ... ... ... ... ... ... ... ... .. ........... ................ i . . . . . . .......... ................................................

TEST . S T (.)

I.........I* ' a -IN

DAT C• D

,. * S *

8-. . 16 ! F ! 

* -- _ . , _ S

I . . . .

ZJ ,, ! " " I , I r, r , 'w ' "

hi I-u . IiI

TEST STAIOARo TilE (5)

VR-PC-S93 - tFLffOUJiOIB ....

FIGURE..6 : MqEASURED riD CAiLCULAITED BREAK FLOU RAITE
RELf1PS'f02- CflLCIJLAlrIONrl LOF turf ir - 1 P -SB --O

.. .. .... .. .... . -------

.. . . . . . . .. . . . . . . .. . . . . ... .. . . . . .. . . . . ... ..... ....

............................................ .........

.. .... . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .

.. . . . . .. . .. . . ... . . . . . . . .. .. . .

T - 1 1 -................

. .............. . ..... ........

.. . .. . . .. .. ... . . .. .. .. . .. . . .. . . .. . . ... . . . .. .. . . .. . . . .. . . . .... .. . . . . . . ..

.. .. . ... . . .. .... . ... .. . . . . .. . .. . . . . . . .. . . .. .. . . . . . . . .. . .. . . . . .. . .. . . ... . . . . .. . .

. .... . . . . . .. . . ... . .. . . .. . . .. . . .. . . .. . . .. . . . . . .. . . .. . . .. . . .. . . . ....... ...... ....... ...

.. . . . . .. . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .

(n 4 4 0.... 0. .................... 0....... . .. . . . .......... . .... ..... .... ... .................... I

tit

------------

............. .............. .. . .. ......... .. ......... ....... .. ... ..... ....... .. .. ... ........ ..................

SooJ 18 1098 2880 Mg8 3088 X008 40IO

DE-K'-265 -Pmt"i600t

FIGURE 7 : MEflSURED ArID CALCULnTED 1-JOT LEG DENISITIES
Z:

ltt

No9-

1e8-

109.

RELor'S'rOD2 (:O)L(:IJLflr[Orl OF LOFT iE51' IP-St3-F)

..... . .. . .. . .. . ... . .. . . . ... . . .. . . . . .

..... .. .. . . .. . .. .. . . . . . ... . ...... .. ..

.. . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .

.*.. . . . . . . . ... . . . . .. .. . . . . . . . . . . . .. . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . ... . . . . .. . . . . . . . . . . . . . .

...............................

............ .......................... ...........

...._ _.........I... .. .. ..... ............

.......................... ........... ....... .......................... .... .................

off"

..711,3

GMIt

(S')

0O see ~ 1000 Isue 2W MR,•uuu

TEST STItIOARO CDE

ODTA

DE-PC-S048 - RIIo1021 -----

FIGURE 8 : MEASURED OND CALCULATED BREAK LINE DENSITIES

3580O

Tlf1
RELAPS/MOD2 CALCULAT[ON OF LOFT TEST LP-SB-02

141 ..................

.......................

.......................

12- .............................................

.....................

....................... ?;........ t........•...... ....................... ........................

..........o........ .. o°. ........... .oooo~o ..o . o... ............. ............

. . .

... ........" S................ •............ ..I............

........................

........................

........................ 1-42

-16

-14

....... . . ...... . ..........J - 1 8

a. 8-1

62

Ia_

.................... ....

... . . . . . . . . . . -.. . . . ...

.. .......... ........ ... ..

.. ..... . .

-................. -. ......................... .... e

.......... ... .. ........

........................

.. .. ........

........................

.......................

------------

.......................

--..... .. . .. .. .. .. . .. .. .. .. .. . .. .. .. .. . .. .. .. .. .. . .. .. .. .. . .. .. ... ... . .. .. .. .. . .. .. .. .. .. . .. .. .. ..1

I I I I I I I

0 Goo too@ .1909 2900 Kilo9 3800

ttvirrr SnMnRD Two

Qcm COBE DnAT

PIMOI ..... 1,16941 PE-PC-W9~l

F IGURE 9 : MfASIJ'RED ANID CAlLCULA TED PR[MnRY PRESSURES

3i89 4000

TUC (5)
RELIHIS'rOD2. ;r(ILCU~nrT[N Or LOFT IEST LP 758-@02

a

JI.

cr'..

1ý-4-

.. ..... ......... .. W. ,

.. . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . .T .. . . . . . . . . . . . . . . . . . . . . .

.... .. ... ... ...... . . .. . .... . .. . .. . .. ... . .. . .. . .. . .. . .... . .. . .. . .. .. . .. ... . .. .. .. . .. . .. . .. .4 . .. . .. . .. . .. .

16

........................

.....................

a

...................

........................

............................................... .......................

............................................. . ......................

............. .................... .......................

........ . ...........

.............. .. ..... 

. .i ..

.6

-4

Il-I I - ti

naOrIED

COD~E

: n 1888

SCODER

1508 20Mg I 2sooi 3889 1~90

TEST

onm

410M

MEr (s)

1FlOWUJ1t33 ... _. tfLOUJA8398 . FR-PC-!93

FIGURE "0 : MEASURED AND :CALCULATED BREAK FLOU RATES
RELnPS/MOD2 CALCULATIOMI OF LOFT TEST LP-SB-02

low-

.. ........... ...........

.......... .:...........

. ... ..-- .... .... ..

...................... T................................

.......... .. .......... .. ........ ...I..........

.............. .....................................

............ ............ .... .I.......... ....

........ ...... ........... ... .......

i

........ .. ...

-4906

lee,

|

I_ - i I I *

e eeIBMe Isee 98 258 3m8 3566 40M8

mrcam MEruw - ros

CMER1C R? CMTPVW7 mss

FIGURE 11 : HZASIJRED AVio cniLC1JIA1TED PRIMARY COOtANT. SYSTEM MOSS INVJENTORY.

r VI (s)
REt-l)P5'rlOtX CALCIJLATPIO OF LO]FT l(1[:rL'K30.

*. . .........

...-.......... ...... ..... ............

....................... ........................ .o

.. . . . . . . . .. . . ... . . . . . . .. . . . .

.. . . . . . . . . . . . . . . . . . . . . . . .1.. . . . . . . . . . . .. . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . . .

.. . . . . . . . . .. . . . . . . . . . . . .4 . . . . . . . . . .

... .. .... .......... .0

hi

.. ........ . .................... . ..................

....... . ............ . ......... ............ .. ...... ....... .........

-------

- - - - - - -

MODIFIED STAflWA4O Ttsr IE S CODE CtODED~

R14OIeeet ...... RnHaIeeI ---- OE-PC-M8

FIGURE 12 : MIEASUJRED AND CALCULATED HOT LEG DENSITIES
RELAPS'r-OD2 CflLCJLATIO1 O1F I-OFT TEST LP-!38-02

8110

-me

Go"

seeJoe

200.

v ........................... ........ ......... ...................... .......................................... ............. .......................

... .... ... . .. ... V ... .. ... ... .. .. ... .. ... . .. .: .. .. ... . .. . .. .. .

", a

............... ":.. .............. . . .

................... ""....... .............. • ""......... ......... .... ............ ". ................................. --...............- .. ..... ...... I....

.. .. .. . . . . .'-.. . . . ..... . ............

...

S.•

: -a-

........... ... ....... ........ I ......... _ _ _ _ _ _ _ _ _ _ _ _ _ _

-I i i i

siloi

-711"

-5$',

E CS)

U

a see 1809

H0Ioi ED, STAflOA00

COOE COD~E

R111elt2t .. R1108281 ---

FIGURE-/3

10S 288 258 80

TEST

DAM

DE-PC-,84o

MEASURED AMID CALCULATED BREnK L[I'IE DENSITIES

4r

TI1
RELAPS'MOD2 CALCIJLATIOti OF LOFT. TE-sr LP-SB4J02

be

a.

, . 2: |-'

., ................... ....................... .... ....... ............. ............ ..... . ....-....... ._... .........

I2

4 . . .. ... ... .. 2 . .. ". "

n I

3. ...................... ..... -................. . • ..... ........ ....................... ...... .................

tn

............. °°°°°o °o°............-°.......... ........................ °°°° .. . .. .. °.........•.............

• -2-

I 2 .. . 1 +"

42 . . . . . , -•. . . . . . . . . . . ..I '". . . . . . . . . ..- 2.. ,'. . . . . . . . .. 2. I -. - - . . . . . . .

• ............ .......... ............................

.. . . . .. . . .. .. .. . .. ... ... : .. ..........

g. .... . t ....... ....... ....

-..... 

............................. ....

.. .... .............. •................ ... . .. •...... •..... ............

...... * ............. .e .... .... ....

* • I

I ........ .. ................ -'.......................I

-4

2080 If841 ~ 

mrroSrnwlFwe TEST T ItyL cow COD DAM

P5281 ...... P538W PE-SGS-881 -

FIGURE J1/ : MEASURED ANID CALCULATED SECONIDARY PRESSURES.

IJ

(S)
. RELArPS/MOD2 CALCULfATION OF LOFT TEST LP-SB-02 USING MODI[FIED CODE

Ar

12-

18-

S

.. .. ... ..

i""..."....... "........

... o..... ........

°... ...........

1 o

......................

...... .... .... .........T• o

..........- ........... ..

...............

........................

........................

12

...................... 18

CnuLctA TElD 3cEI.

.°

d •J= ................... J

........... ... J.. .. .. . v I.

........................

...... ........... I.....m ..... .... .ý -l-*.l~l*I...... w tq........

V. -- "lu.--0

..... + ...... .... ~ty .- ...... - -I. !t:1 ....... . "':............... ... ....... ......

t I_ ITi 4N . ... .......

..................

I.

•i•...................

..........

I'

-6

-4

A I

-............... ................ .. ....... .. . ....... .. .. - 1

-~.............. ................... ..

- -...................... I. .................. ;-4 ..... ;--............ ....................... I. .......... ....... -;... ................ ....... -- .............. .. .;

:.. +. . .+ .+: .i. -

S 2988

2s

FIGURE 15 : t1E9SURED iND CAlLCULATED COOLANT IEL(ICITIES I" 110T LEG
RELIIIPS/'l10D2 ClOJLfLA[Oll OF LOFT lEST LP-SB -02

I .

CA" -.. ....... . .......................... -... ............................................... -- . -. 

s . .. I • . . ,

74M . -...... .......... . 4 . . ......... .................. ............... ...... .............. .-- ... ................... ............................................ .... .... .......1

I . .. . . . . . . . . ,...... . . . . . .....

~lL ,.i I I ! i

..... .,. 8.- _,t' V.. ',

... ... .. ... ... ... . .. . . . i . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .t I . . . . . . . . .• ~ •

"rli.-"i "3 -di -... I

I.,

N

E

r

hi

0

~88

188

a

.... . .... ........ °.**°o .o .. °, ...... .. ° 0.. ..... •...... .. ;. . ......

... NZ.... ........

....................... ............ ..................................

........ .......

............. ...........

.......................

..................... *1228

.I ! w Id ....................................... ... ;~*ool*e ....................... I....................... ....................... I

I i I I p I

6

S1)WOI1

CODE

RnIKIII2

W01FCED •TEST

ewe DAlTA

..... I 180 ..... !IE-pc-Ms31

FIGURE lb : VEASURED ANID CALCULATED LOOP SEAL DENSITIES

Iq88

rTM: (S I
RELA1PS/MOD2 (:ALCJLAYTtIO OF Loi-r IEST LP-S[3-02

........... 

... ... ...... ..........................

se ...... .. ........... . ............. ........... .... .. ............. .... ........ . . ............. so"~

......... .w ........... ......... ............. ... ........ ..." .. ... ...... ...... "

kl0 -- - -

...... .... ... ....... ... .

.. ........... ........ ............. .. ..

see8 1000 IsUB 2088 2so8 360880 4000

tWOIF IEO STnnOWD TEST TIM (S)

CODE CODE DAM~f

R1117Q .... RHO 1502 - -- O E41-1C0B5 _

FIGURE 17 : MEASURED AIND CALCULATED COLD LEG DEINS[TIES
4134

0.

w

in

Ile

(L

A

Id

IL

REL(IPS/MOD2 (CflLCIJLAT([I]PI OF LOFT rEST LP-SB-0,? USING MJD[F[ED CODI)E

. ...................... ....................... .......... .............. ...................... ....................... ........................... : ............. : ......... •...................... ,,olJ

......................... ............... ........ :-.......... ...................................... ........................................ -...... ....................... -0

... ......... ..... . ................ :....................... ... .... ...................... ; .. •.. I............................................ ....................... . .. .................................................... ...................... ,0

.. ............. .. ..... .. .. . . . . .. ... . . . ... ........................ . . ... L.................. .... ......................... •......................

.. . . . . . . . . . •. . ... . . .. ... ... . .. . . . . . . .... . . . . . .. .. . . . . .. .. .. . . . . .. . . . . .. . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . m

....................... :........... .. • .................... "•............ ...................... 1 ....................... : ....................... : ...................... .dl

.44............

....................... ............................... ......... :7 .....

....................... i....................... "...................... •-...................... ................ ... ............. i..................... -.." ' ' I Ix I

see ION I1soo 2e0M 2S90 3N041 3580 41041

ws r TIME (S)

tL4)0

13

11241r(110 PUtIP IATA STIWI4WD PI'I DATA DATAl

FIGURE 01 : MEAlSURED AN1D CAL.CULATED PUMP DIFFERENITEIAL PR[ESSUJRES
RELflI'S/HOo2 CflLCULflTIOri OFr LOFT TEST LP-SB3-0 USflING "I(DW lED COD)E

12-

......................

d

I..

'4

.. .V .......... ......... " .. ..... ... I .................... ..- .-..- ........ ... .....

:i- -- - " ."

... Re ... .ISJlO ............. " .Mi. ................ ..

I ~ ..........

.. ... ................................................. ................ :..ti ..._ .. -

........... ......

I t

sirrnnio rum onm

. . .. ...... .t. .. . .. . . .. .. o

-42

4.-

EXP[Rtmnrn. D~m

. ... . . .......... ...

-4

REOL

m I................. ..... I R• • LLILI DO i•J "A

............ ............ ...........

....................... ........................ ....................... ....................... .......................

~1~~~~~

a I IoI tIsg 1 2589 iS 4t386

FIGURE A2 : MEAISURED ANID CALCULATED COOLnMT UEI.OCITIES IH HOT LEG
RELAn5'lol)D2 CflLIJulr[Ilrl OF LOFT TEST LP-SB-02 'lJSTlll MIODIFfE() CI)DE

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FIUE01- EAUE Ot ALUAE HtLE DIISTE
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

(2.89) (Ast( 0

gnd by NRC. Add Vol.. Supp.. Rev..

NRCM 102, and Addendum Numbers. It onvy.

3201.3702 BIBLIOGRAPHIC DATA SHEET NUREG/^A-0021

(See instructions on the rs• reGD/e] •o;GD/PE- ;s,•c;o,• , ,h N/606 ( ( Rev )

2. TITLE AND SUBTITLE

RELAP5/MOD2 Calculations of OECD LOFT Test LP-SB-2 3. DATE REPORTPUBLISHED

MONTH YEAR

April 1990

4. FIN OR GRANT NUMBER

A6827

5. AUTHOR(S) 6. TYPE OF REPORT

Technical

P. C. Hall 7. PERIOD COVERED inclusje aDres)

B. PERFORMING ORGANIZATION - NAME AND ADDRESS (fi NRC. provide b',siono Office or Region, U. S Nuclear Regulatory Commission, and mailing address; if contractor, provide

nwsne and mailing address.)

Central Electricity Generating Board

Generation Development & Construction Division

Barnwood, Gloucester GL4 7RS

United Kingdom

9. SPONSO RING ORGAN IZATION - NAM E AND ADD RESS Ifi NRC, type -Smeý as above" * If contractor, pro•/de NRC Division, Office or Reqlon, U.1 Nuclear Regulatory Commission,

and mailing addres)

Office of Nuclear Regulatory Research

U. S. Nuclear Regulatory Commission

Washington, DC 20555

10. SUPPLEMENTARY NOTES

11. ABSTRACT 1200 words or kls

To help. in assessing the capabilities of RELAP5/tI0D2 for-PWR Fault Analysis, the

code is being used. by CEGB to simulate several small LOCA and pressurized transient

experiments in the LOFT experimental reactor. The present report describes an

analysis of small LOCA test LP-SB-02, which simulated a 1% hot leg break LOCA in a

PIR, with delayed tripping of'the primary coolant pumps. This test was carried

out under the OECD LOFT Program.

12. KEY WORDSIDESCR!PTORS (List words or phrass that wilt assist researchers in locating the report.) 13. AVAILABILITY STAT EMENT

I lnIimi tpd OECD LOFT 14. SE CURITY CLASIFICATION

RELAP5/MOD2 (rtis Page)

LOCA IIncl assii fipd

(This Reportl

Unclassified

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 (269|




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PERMIT No. G-67