NUREG/IA-0064

GD/PE-N/725

PWR/HTWG/P(88)629(Rev)

International

Agreement Report

Analysis of Semiscale Test

S-LH-1 Using RELAP5/MOD2

Prepared by

P. C. Hall, D. R. Bull

National Power Nuclear

Barnett Way

Barnwood, Gloucester GL4 7RS

United Kingdom

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

April 1992

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

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

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

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and

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NUREG/IA-0064

GD/PE-N/725

PWR/HTWG/P(88)629(Rev)

International

Agreement Report

Analysis of Semiscale Test

S-LH-1 Using RELAP5/MOD2

Prepared by

P. C. Hall, D. R. Bull

National Power Nuclear

Barnett Way

Barnwood, Gloucester GL4 7RS

United Kingdom

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

April 1992

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 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.
GD/PE-N/725

PWR/HTWG/P(88)629(Rev)

CENTRAL ELECTRICITY GENERATING BOARD

GENERATION DEVELOPMENT AND CONSTRUCTION DIVISION

PLANT ENGINEERING DEPARTMENT

NUCLEAR PLANT BRANCH

Title: Analysis of Semiscale Test S-LH-l Using RELAP5/MOD2

Author: P. Hall and D.R. Bull, Safety Technology Section

Approved by: f Sa et~y Technology Section

Summax:y

The RELAP5/MOD2 code is being used by GDCD for calculating Small Break

Loss of Coolant Accidents (SBLOCA) and pressurised transient sequences

for the Sizewell 'B' PWR. These calculations are being carried out at

the request of the Sizewell 'B' Project Management Team.

To assist in validating RELAP5/MOD2 for the above application, the code

is being used by GDCD to model a number of small LOCA and pressurised

fault simulation experiments carried out in various integral test

facilities. The present report describes a RELAP5/MOD2 analysis of the

small LOCA test S-LH-l which was performed on the Semiscale Mod-2C

facility. S-LH-1 simulated a small LOCA caused by a break in the cold

leg pipework of an area equal to 5% of the cold leg flow area.

RELAP5/MOD2 gave reasonably accurate predictions of system thermal

hydraulic behaviour. In particular, the hydrostatic core level

depression resulting from the hold-up of water in the steam generator

tubes and pump suction legs was well predicted. A reasonable prediction

of core inventory was also obtained in the period of the test in which

the core level fell as a result of coolant boil-off.

The code did not give an accurate prediction of the liquid distribution

within the core during the uncovering phases. Consequently the fuel

temperature excursions due to uncovery were not captured by the code.

Failure to calculate the correct void fraction distribution and dryout

behaviour is believed to be due to numerical approximations in

representing the core by a small number of nodes, rather than due to

errors in the physical models and correlations used in the code.

iii
Based on the present study it is suggested that, in reactor analyses in

which the potential for core uncovery occurs, the mixture level

trajectory and peak fuel temperatures are calculated outside RELAP5 using

a code employing a fine axial mesh, using boundary conditions from the

RELAP5 analysis.

Date: February 1989

Security: This report is security classified. It may be passed to

other people by recipients on the distribution list on a

'need-to-know' basis and may not be passed outside the

recipient's own organisation without the consent of the

Safety Technology Engineer.

iv
CONTENTS

1. INTRODUCTION I

2. CODE VERSION AND INPUT MODEL I

3. INITIAL AND BOUNDARY CONDITIONS 1

4. DESCRIPTION OF TEST S-LH-1 2

5. BASE CASE CALCULATION 2

6. SENSITIVITY STUDIES 4

7. DISCUSSION AND COMPARISON WITH PREVIOUS ANALYSIS 7

8. GENERAL CODE PERFORMANCE AND CPU TIMES 8

9. CONCLUSION 9

10. REFERENCES 10

TABLES 11

FIGURES 13

V

1. INTRODUCTION

The RELAP5/MOD2 code [1] is being used by GDCD for calculating Small

Break Loss of Coolant Accidents (SBLOCA) and pressurised transient

sequences for the Sizewell 'B' PWR. These calculations are being

carried out at the request of the Sizewell 'B' Project Management

Team.

To assist in validating RELAP5/MOD2 for the above application, the

code is being used by GDCD to model a number of small LOCA and

pressurised fault simulation experiments carried out in various

integral test facilities. The present report describes a

RELAP5/MOD2 analysis of the small LOCA test S-LH-l which was

performed on the Semiscale Mod-2C facility [2, 3). S-LH-l simulated

a small LOCA caused by a break in the cold leg pipework of an area

equal to 5% of the cold leg flow area.

In addition to a detailed description of the new analysis of S-ILl-i,

comparisons are also described with earlier calculations with

RELAP5/MODl and RELAP5/MOD2, described in reference [4].

2. CODE VERSION AND INPUT MODEL

The code version used for these calculations was RELAP5/MOD2/cycle

36.05 E03. This code is a version of the standard release of INEL

cycle 36.05 containing error corrections (primarily Cray conversion

errors) implemented by UKAEA, Winfrith. In addition the horizontal

stratification model of Ardron and Bryce [5] is optionally available

in version E03. This model was used in the present calculation to

model the junction connecting the break line to the cold leg.

The RELAP5/MOD2 model was taken from reference [4]. Discharge

coefficients in the break junction were set at 0.9 for both single

and two-phase flow. The RELAP5/MOD2 model consisted of 181 volumes,

172 junctions and 256 heat structures : the noding diagram is shown

in figure 1.

Microfiche listings of code input and output have been filed under

Safety Technology Section in the Microfiche Archive at GDCD,

Barnwood. Code input is archived under BBWDQAA, at Barnwood.

3. INITIAL AND BOUNDARY CONDITIONS

As stated above, initial and boundary conditions for the present

calculations were taken from reference [4]. To establish the

required steady state conditions, a steady state calculation was

first run for 300s of problemntime. Parameters controlled to

achieve the desired steady-state were steam and feed flow and the

pump speed. A dummy time-dependent volume was connected to the top

of the pressuriser to maintain the desired steady primary pressure.

After 300s these steady-state conditions were removed, the dummy

volumes deleted and the calculations allowed to proceed for 50s

before initiating the transient.

1
Figures 2-4 show the hot leg pressure and pressuriser level, the

flows into and out of the intact loop SG separator; and the intact

loop steam generator pressure and level during the steady-state

run. These figures illustrate that a satisfactory steady-state was

achieved. The RELAP5 calculated steady-state conditions are

compared with experimental values from reference [4] in Table 1. It

can be seen that the steady-state conditions are satisfactorily

calculated, except for the intact loop steam generator secondary

side level, which had to be set artificially low to allow RELAP5 to

calculate stable operation of the steam generator. Use of a reduced

inventory is considered acceptable, since in the test S-LH-l the SG

secondary plays only a minor role in the overall primary system

energy removal.

The High Pressure Injection System (HPIS) was modelled via a table

of flow versus primary pressure. The secondary feed water flow was

modelled using a table of flow versus time, with the flow being

stopped by the activation of a trip signal. The steam generator

steam bypass valves were modelled as set to open when the

appropriate steam generator exceeded 7.2MPa. The Semiscale facility

makes extensive use of external guard heaters to reduce heat loss

from the facility to the surroundings. The time variation of power

supplied to these heaters was modelled in the RELAP5 calculation.

4. 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 a

block valve, allowing primary fluid to flow through the break

orifice to the break flow condensation system. Reactor trip was

simulated by reducing core power to decay heat levels 3.4s after the

pressuriser pressure fell to the set point level of 12.6MPa. Loss

of offsite power coincident with reactor trip was simulated in the

test. Therefore feed water was terminated and MSIV closed upon

reactor trip and the primary circulating pump also tripped. High

pressure injection was initiated 25s after reactor trip to simulate

delay in starting the emergency diesel generators.

In the S-LH-I transient break flow was initially insufficient to

remove decay power. Therefore primary pressure remained above the

secondary pressure until the intact loop pump suction pipework

cleared of liquid at 171s. A core level depression and dry out

occurred prior to pump suction clearance. After clearance a slow

core boildown began; dry out of the fuel rod simulators commenced at

about 400s and terminated at about 650s, 150s after the initiation

of accumulator injection.

5. BASE CASE CALCULATION

The calculated timing of key events is compared with data in Table 2.

The measured and calculated primary system pressure histories are

shown in Figure 5. The period of subcooled blowdown up to

approximately 50s is accurately calculated. The small overestimate

of pressure in the period 50-250s probably arises from errors in the

calculation of secondary side behaviour. Following loop seal

2
clearance, the calculated depressurisation is too rapid, suggesting

overestimation of discharge enthalpy. The accumulator injection

pressure set point is-reached at 400s in the calculation,

approximately 100s earlier than in the experiment. Measured and

calculated secondary side pressures are compared in Figure 6.

Pressures are systematically overpredicted at all times after

closure of the main steam control valves (MSIV), but the errors

appear to have only a minor influence in this test. Some

sensitivity calculations were performed with an arbitarily specified

steam leakage in the MSIV. These indicated that discrepancies

between measured and calculated secondary pressures later in this

test could be accounted for by assuming a plausible leakage area of

less than 0.16% of the full MSIV area.

Figure 7 shows a comparison of measured and calculated discharge

mass flow rates. Overall agreement is seen to be good, except in

the low quality discharge period of 50-175s. Critical flow rate is

strongly sensitive to upstream stagnation enthalpy under these

conditions, and the agreement between measured and calculated

results in the period 50-175s is therefore considered acceptable.

The calculated increase in discharge flow at 140s occurs because of

the arrival of lower quality fluid in the broken loop cold leg, as

the broken loop pump suction pipework is cleared of liquid. In the

period between loop seal clearance and accumulator injection

discharge flow rate is underestimated by about 20% (0.02kgs').

Figures 8, 9, 10 and 11 compare the measured and calculated

collapsed liquid level in the intact and broken loop SG U-tubes and

pump suction legs. Experimental data are derived from differential

pressures measurements and are therefore invalid until the

termination of forced loop flow at about 50s. It is also suspected

that experimental errors are subsequently significant, since some

measured values show a large offset late in the transient.

It can be seen in Figures 8 and 9 that RELAP5 predicts considerable

liquid hold-up in the up-side of the SC tubes in the period 120-

250s. However, the calculated hold-up is generally - lm of water

less than the measurements indicate, and is less prolonged. Figure

10 shows that the collapsed liquid levels in the intact loop pump

suction are calculated accurately, though with a time shift of about

25s. Agreement between measured and calculated collapsed liquid

levels in the broken loop pump suction (Figure 11) is relatively

poor. RELAP5 predicts that this loop'seal is the first to clear, at

180s, followed by partial refilling as the other loop seal clears.

In practice, this loop seal did not clear until - 260s, after the

broken loop SG U-tube upside had drained. The ability to predict

which loop seal clears first is of little practical importance, and

the present result is therefore considered to be acceptable.

Figure 12 compares measured and calculated collapsed liquid levels

in the reactor vessel downcomer and core. The key features of the

experimental data are the deep core level depression which recovered

at about 170s and the gradual boildown which occurred between 300s

and 530s. The first core level depression, which is caused by

hydrostatic pressure due to the build up of liquid in the upsides of

3
the SG tubes and pump suction pipework, is seen to be accurately

calculated by RELAP5. The second core level depression, caused by

boil-off of water in the core, is less accurately calculated by the

code. In addition, the calculation of an over-rapid

depressurisation rate leads to the premature activation of the

accumulators, which results in the calculated boildown being

terminated too early. These errors are discussed further below.

Measured and calculated core void fractions are shown in Figures 13

and 14 respectively. The experimental data of Figure 13 are

reproduced from figures given in reference [4]. Figure 14 shows the

axial variation of core void fractions calculated by RELAP5.

Inspection of Figure 14 shows that in the period of the hydrostatic

core uncovery, (150-200s) the calculated void fraction reaches a

maximum value of approximately 0.94 in the highest core volume, and

0.86 in the lowest. This is in marked contrast with the test, where

the void fraction reaches unity in approximately the upper two

thirds of the core, but remains at about 0.1 at the bottom of the

core. Thus, even though the calculated core collapsed liquid level

was less than the measured value, the void fraction at the top of

the core is evidently underestimated by RELAP5/MOD2.

To compare the measured and predicted core axial void fractions in

the core boildown phase (350-500s), we examine condition at t -

400s, immediately prior to the calculated time of accumulator

injection. At this time the measured and calculated collapsed

liquid levels are approximately the same. It is seen by comparing

the figures that at t - 400s, a well-defined two-phase mixture level

existed at the 250 cm elevation in the test (see Figure 13b).

However, in the RELAP5 calculation a near homogeneous two-phase

mixture is calculated to exist in the top part of the core.

Therefore, although RELAP5 adequately calculated core water/

inventory at this time, the detailed axial distribution in the core

was in error.

Figure 15 compares measured and calculated heater rod temperatures

at around the 250cm elevation (the discrepancy prior to trip arises

because the RELAP5 value is for the heater rod surface, whereas the

experimental value is measured wit*h an embedded thermocouple.

Discrepancies due to the thermocouple location-become insignificant

after trip). It is seen that RELAP5 fails to calculate either of

the experimentally observed dryouts. These discrepancies are due

primarily to the errors in the calculated core void fraction

distribution described above, and are considered further in the next

section.

6. SENSITIVITY STUDIES

The primary shortcomings of the calculation described above are

inaccuracies in the calculated pressure history, core void fraction

distribution and the failure to calculate the core dryouts.

Numerous sensitivity studies were carried out to investigate the

cause of these errors. Results are described in this section.

4
6.1 Modelling of Hydrostatic Core Uncovery

Figure 12 illustrates that the hydrostatic core level

depression occurring in the period 170s was well

calculated by RELAP5. However, although the core

collapsed liquid level was actually underpredicted,

dryout was not calculated because RELAP5 predicted

significant liquid fractions at the top of core.

Detailed investigation of calculated void fraction and

flows in the core, upper plenum and hot legs, indicated

that during this period of the hydrostatic level

depression, a small counterflow of water was predicted

to be refluxing from the hot legs into the upper plenum

and core. In the core volumes this downflow of water

maintained the void fraction below about 0.95; this was

sufficient to prevent dryout according to the CHF

correlation applied by RELAP5/MOD2 for these condition

(modified Zuber correlation). In practice such a

downflow would probably run down the wall of the core

vessel and would be unlikely to prevent dryout in the

rod bundle centre region. Loomis and Streit [4] indeed

noted that in the test, whilst some pins dried out,

others at the same elevation did not, indicating that

falling films of water were present on some rods above

the mixture level. This is consistent with the view

that a spatially non-uniform liquid distribution exists

in the core region. To try to model such liquid

distribution effects in RELAP5, the core model was

modified as illustrated in Figure 16. The core was

split into two channels. One channel represented the

outer subchannel, next to the vessel wall. (The vessel

heat structures were connected to this channel.) The

other channel represented the remaining central

subchannels (all heater rod heat structures were

connected to this channel). In initial studies

crossflow junctions were included between parallel core

channels, but recirculating flow patterns arose which

inhibited the calculation of dry out. The crossflow

junctions were therefore deleted. Finally to ensure

that no refluxing water entered the central core zone,

the core outlet junction (volume 146 to 161) was defined

as a homogeneous ('one velocity') junction.

Figure 17 compares experimental collapsed liquid levels

in the core vessel and downcomer for the basecase and

the Aensitivity calculation. It is seen that the effect

of 6e core noding change is to produce a more prolonged

core depression, with earlier clearance of the pump

suction. In spite of the increased core liquid

inventory in the hydrostatic core uncovery phase (t -

140s), the void fraction in the upper part of the core

is now calculated to reach unity (see Figure 18).

Subsequently dryout is now calculated to occur as

illustrated in Figure 19. The rate of rise of

temperatures is well calculated, but because the

calculated dryout is too prolonged, the maximum heater

rod temperature is over-predicted.

5
It is concluded that under conditions of core level

depression in which reflux condensation is taking place,

RELAP5/MOD2 may fail to predict a dryout. Care must

therefore be taken in using the code to predict peak

fuel clad temperatures in these conditions.

6.2 Modelling of Core Boildown Phase

As noted above, RELAP5/MOD2 also failed to calculate

dryout during the boildown phase of this transient (350-

500s). This appears to be due to errors in the

calculated core void distribution, and also to the

prediction of early accumulator injection.

Figure 17 shows the collapsed liquid level in the

downcomer obtained in the base case and sensitivity

calculations. The sensitivity calculation is seen to be

more accurate than the base case calculation.

The core void fraction distribution in the sensitivity

calculation is shown in Figure 18. Again these results

are in much better agreement with the test data (Fig

13b) than results for the base case calculation.

However the improvement seems mainly due to the use of

the one-velocity junction at the core outlet, which

increases the calculated liquid carry-out from the top

of the core. The agreement with test data is therefore

regarded as somewhat fortuitous.

In spite of the improved agreement with the core

collapsed liquid level and void distribution RELAP5/MOD2

still fails to predict a core dry-out during the

boildown phase, as can be seen from Figure 19.

Modifications to the level sharpener model in the code

would probably be necessary to successfully calculate

the core dry-out, given the coarse axial mesh used to

represent the core in the present analysis.

6.3 Calculation of Depressurisation. after Loop Seal Clearance

It is seen from Figure 5 that the depressurisation rate

after intact loop seal clearance is over-estimated by

RELAP5/MOD2. Consequently the onset of accumulator

injection which terminated the core boil-down phase is

predicted to be too early. Calculations were performed

to determine if errors in the calculations of break flow

and enthalpy were responsible for the errors in the

depressurisation rate.

To investigate the effect of changing the discharge flow

multiplier (CD2), a calculation was performed with the

value arbitrarily set to 0.65, (as opposed to 0.9 in the

base case). The accuracy of the calculated pressure

history was greatly improved, but the calculated core

water inventory was significantly overestimated in the

6
boildown period. It was therefore concluded that the

errors in calculated depressurisation rate cannot be

ascribed simply to uncertainties in the break flow

multiplier.

A check was .then made of the break mass flow rate

caicuiated-by RELAP5/MOD2 in the period 250 -to 450s.

Va.lues -were found to be within 10% of prediction of the

homogenous thermal equilibrium model of two-phase

.critical flow, which would be expected to provide a

reasonable ,prediction for the orifice geometry and

the.rmodynamic..conditions I'in the test. Therefore the

,:REAP 5/MOD2 .results are considered reasonable.

r .. Finally .a check was made on-the calculated enthalpy in

the~broken loop cold leg in.the.period 250-400s.- REIAP5

S: .results, indicate ,•oid .fractions in the range 0.98-1.0 in

-this period.

Experimental data based n gamma densitometer

, measurements indicate high 'void fraction at the vessel

end of -.the brokenloop cold leg.;, However, -the bottom

. - densitometer beam at the ,pump discharge end-of the

.broken cold leg reveals the-persistence of a layer of

_- .- , - .,water.throughout the-transient. This suggests that the

error in calculated depressurisation rate results from

errors in the calculated rate of entrainment of water

.•. ....... from the.broken loop pump suction-pipework into the cold

" leg, and7.breaknozzle.

-..Additional information suggesting~that the error in.

calculated depressurisation rate is related to errors in

... r .. the calculation, of broken -loop -cold leg conditions comes

fromidetailed inspection of .the -primary pressure

.: history...The experimental ;pressure history shows two

distinct.knees at - 180 and 270s as the broken and

, ?intact " looppump suctions clear. In contrast, the

-, -. calculation.-shows only a single knee.as the broken loop

pump suction clears.. - , - .. -. ..- . -

- It-was, concluded that relatively.,small errors :in the

calculated clearing behaviour of the loops seals

probably gave rise,-to the overprediction.of the

depressuripation rate. However, the data is

, ..insufficiently, detailed.to eliminate-errors in . _•., calc.ulate.d• : - .... . • -. . . ... ....- tcalculated-primary-t-secondary heat transfer, or

-me alw~rý. heat nf'e'r 'ascontributors to -the errors in . calculated pressure[4]" -- :, . .

7. DISCUSSION AND COMPARISONWITH. PREVIOUS ANALYSIS . -' . "

I.! '. 7 , -

The present.-test has _been;,analysed by.Loomis and Streit .[4] using

RELAP5/MOD2/Cycle 36.05. In common with the present study, these

authors noted the failure of-RELAP5/MOD2 to calculate dryout

correctlgy; hey alsonoted that calculated primary pressure fell

too quickly after loop seal clearance.

7
Loomis and Streit [4] found that by modifying the interphase drag

correlations in RELAP5/MOD2 to give a 90% reduction of interphase

drag in the core volumes, a reasonable prediction of the liquid

level trajectory in the core could be achieved. The present

calculations have shown that an accurate prediction of the core

axial void fraction profile can also be achieved using the

unmodified interphase drag models, providing adjustments are made to

the modelling of slip in the core outlet junction. This suggests

that errors in the void distributions are more likely to be due to

approximations used in numerical implementation of the interphase

drag correlation, than to errors in the correlations themselves. It

is believed that averaging procedures used to calculate interphase

drag in junctions, treatment of inverted void profile and the level

sharpener model, all contribute to errors in the core void

distribution found in the present base case calculation.

Loomis and Streit also recommended that the critical heat flux (CHF)

modelling in RELAP5 be modified to allow calculation of dryout in

the hydrostatic uncovering phase. They suggested that the factor

(1 - a ) appearing in the modified Zuber CHF model should be

replaced by (0.94 - ag) to ensure that dryout is calculated when the

core void fraction exceeds 0.94.

The present studies suggest that failure to calculate dryout in the

S-LH-l hydrostatic uncovering phase was not in fact due to CHF

modelling but was rather due to incorrect calculation of the liquid

distribution in the core under conditions of reflux condensation.

It is concluded that considerable care must be taken in modelling

the liquid level trajectory and core heat up behaviour in

RELAP5/MOD2 simulations in which the core is represented by a small

number of nodes. It is recommended that in reactor fault analyses

in which the potential for core uncovering occurs, the calculation

of the level trajectory and the peak fuel clad temperatures be

performed with a separate code using a fine axial mesh, taking

thermal-hydraulic boundary conditions (core liquid inventory,

pressure, inlet enthalpy, core power) from RELAP5/10D2.

8. GENERAL CODE PERFORMANCE AND CPU TIMES

The present calculations were performed on the Cray-2 computer at

AERE, Harwell. 2270s of CPU time was used, giving a CPU:real time

ratio of 2.84:1. The CPU time per timestep per mesh cell was

1.32ms. The main limitation to timestep size was the courant limit

in the broken loop pump suction pipework. The code was found to be

stable and easy to use. However, it was found necessary to reduce

the maximum timestep manually during the first 25s to avoid

calculation of premature dryout and subsequent code failure.

Using the split core input model, the CPU: real time ratio reduced

to 1.75:1, and the CPU time per mesh cell per timestep was 1.20ms.

8
9. CONCLUSIONS

1. RELAP5/MOD2 cycle 36.05 Version E03 has been used to

analyse test S-LH-I (5% cold leg break loss of coolant

accident simulation) carried out in the Semiscale PWR

test facility.

2. The code gave reasonably accurate predictions of system thermal hydraulic behaviour. In particular, the

hydrostatic core level depression resulting from the

hold-up of water in the steam generator tubes and pump

suction legs was well predicted. A reasonable

prediction of core inventory was also obtained in the

period of the test in which the core level fell as a

result of coolant boil-off.

3. RELAP5/MOD2 did not give an accurate prediction of the

liquid distribution within the core-during the

uncovering phases. Consequently the fuel temperature excursions due to uncovery were not captured by the

code. Failure to calculate the correct void fraction

distribution and dryout behaviour is believed to be due

to numerical approximations in the implementation of

interphase drag modelling and in representing the core

by a small number of nodes, rather than due to errors in

the physical models and correlations used in the code.

4. Based on the present study it is suggested that in

reactor analyses in which the potential for core

uncovering occurs, the mixture level trajectory and peak

fuel temperatures are calculated outside RELAP5 using a

code employing a fine axial mesh, using boundary

conditions from the REIAP5 analysis.

9
10. REFERENCES

2.

NUREG/CR-4312

EGG-SEMI-6813

RELAP5/MOD2 Code Manual

Volumes 1 and .2

V.H. Ransom et al

Experimental Operating

Specification for

Semiscale Mod-2C 5%

Small Break LOCA

Experiment S-LH-i

G.G. Loomis

Quick Look Report for

Semiscale Mod-2C

Experiments S-LH-l

and S-LH-2

G.G. Loomis, J.E. Streit

Result of Semiscale

Mod-2C Small Break

(5%) LOCA Experiments

S-LH-l, S-LH-2

G.G. Loomis, J.E. Streit

Dec. 1985

Feb. 1985

. 3. EGG-SEMI-6884

May 1985

4. NUREG/CR-4438

Nov. 1985

5.

6.

AEEW-R2345 Assessment of Horizontal

Stratification

Entrainment Model in

RELAP5/MOD2 ,

K.H. Ardron and--.

W.M. Bryce 1988

EGG-SEMI-5622 Post.Test RELAP5

Simulation of the

Semiscale S-UT Series

Experiments

M.T. Leonard Oct. 1981

10
TABLE 1

INITIAL CONDITIONS FOR S-LH-I

EXPERIMENT

Pressuriser pressure MPa

Core power

Core AT

kW

K

15.47 + 0.14

2014.75 + 0.15

37.65 +1.5

-0.6

395 + 14

Pressuriser liquid level

(collapsed above bottom)

Cold leg fluid temperatures

Intact loop

Broken loop

Primary flow rate

Intact loop

Broken loop

Initial Bypass flow

(% of total core flow)

cm

K

562.12 + 2

564.05 + 2

kgs -1

RELAP5

15.47

2014.75

37.30

396.1

560.9

565.68

7.13

2.35

0.92

0.•

5.8

6.09

150.0*

:43.0'

7.13

2.35

0.9

Leak rate kgs- 0.0002 1

SG secondary

SG secondary

pressure

Intact loop

Broken loop

side mass

Intact loop

Broken loop

MPa

5.72 + 0.07

6.08 + 0.07

kg

191 ± 13

43 +4.3

* Approaching limit of stable operation of steam generator by RELAP5

11 .;
TABLE 2

TIMING OF EVENTS FOR S-LH-l

EVENT

Small break valve opened

Pressuriser pressure

reaches trip level" (12.6MPa)

Pump coast-down initiated

Intact loop

Broken loop

TIME AFTER BREAK OPENS (s)

EXPERIMENT RELAP5

(BASE CALCULATION)

0.0 0.0

HPIS initiated

Intact loop

Broken loop

Pressurizer empty

Minimum core collapsed

liquid level

Pump suction clearing

Intact loop

Broken loop

Second core dryout

Accumulator injection

Intact loop

Broken loop

14.67

21.35

20.76

41.60

.40.98

33.9

172.6

171.4

262.3

412.8

503.8

501.4

16.95

21.7

21.35

43.68

43.28

55

182

203

180

406.0

407.0

12
Semiscale S-LH-1

LA)

I CAIEP OAt OS OR~ fArt

ICAt CkiS VEULICATEPS

Fiqure 1 : RELAP5 nodinq diaqram for Semiscale S-LH-1 Calculation ( Base case)
UISIOII REFEREINCE FILE STOY-STATE2:S-LII-i :I

Semiscale S-LH-1 : SLeady sLaLe

) (2] 16 ( I

15.6-

S

i

S

I.

I S.2G14.0-

14 -

i-.- -1 - -- - -.-.--- - - -- - - es- - -r-e

-0

... ........ ..... .1. .. ..... ..... ..T .. ...... ...... .. ..... ...... ... ..... ..... . .... ..... ..... ...

.31

.36

* (

.34

r

.32-

.40

P20 181

50109 ISO3 00 250

(1) CIITRI.UARG (] - -[

Figure 2 : HoL leg pressure and pressurizer level

S 300,:
VISIOtI PEFEREIICE FILE STDY-STATE2:S-LIf -1: 1

~ ;J~ 1K~ Se~isaIS-L[]-'l :'ýSL66dys C L&'

Ln

e

I4-

3L

I.....

*I !

/ I  ̧ ............. , . ... ... ........... .. ...................... . ..

... ...I,\.. .... .. '

i .. ..........

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

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

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

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

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

............................ ................ ~ ~ ~ .................. ~ ~ S~es ................

-t 7dý7

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

..... ...re.............. ............

I

8

tfLOWU 181O

5to 15 a 2a 259

I'fLOUJGOI162 - - I. tOWGO!8) .....

F i qure 3 " i'AIhcncL loop 'sLedm'' g-enerhior" separalor mass f low rales

300
[)

UISIOri PEFERENtCE FILE STDY-STAIE2:S-LH-I:1

Semiscale S-LH-1 SReady SLaLe

(21

S-~ - - --.. . ... .-- w -. 12

i. m,-. ..

0

L

ar

a

C

S

.88

1.84

a 58 10s 158 208 258 388

PG6181 01) M- C(TRLL=R43G .21

Figure 4 : InLacL loop sleam generulor pressure and collapsed liquid level
0

C-

-I"-

I.

Semiscale S-L14-I

14- .............. .... j....... 

*1 ........................ .....

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

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

.8 .... ........................ .......... ..... 2................. ...........

12k. .... ..... ........ ... ..... ................ . ...... ..... ..... ..... ..... ..... ......

..............................e .... ........... ..... ..... .................. ...........

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

.............................. ...... .. ............................. d.............. ......................

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

2

8

6

4

IOa 2a0 300 400 50s GOO 700 800

line a s )

P28101 . Pll

Figure 5 : Measured and calculaled primary pressure C Base case )
Semiscale S-LUI-I

.......... ....... ... .......... ....... ...... .. .... .... ... ............ ........... .......... ... . .... -7 ......... - .-.......- ........

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

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

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

00

.. ............. •'........... - ......... ....................................................................... ........................ ................................................ ............. -4

L -. ........... I . . ............ .. . ............. .. . ............... . ................. . . . . ....................... ............ ........... . . . . . . . . . . . . .-. . . . .. -

-e

0 108 208 308 400 O00 OO 700 800

lifre ( s

POW .......... PBG.11G _ GIIOI PISM.I17

Figure G : Measured and calculaLed secondary pressures ( Base case )
Semiscale S-LII-1

1.0-

0.2-

In

I.

3

0

Lb'a 9.4-

-I................. . ... ............ ... ................... .................

....... ......... ....................... ....... .......... ..... .......... .......... .,......... ........... s...".......

.'. ..... ..... ..... .... .. .... .. .. .. ..........

. ...... .

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

* .. ... ... ... r ... .. .... . .. .. .... .. . ...

i'. ....... • ,•,.i .... .... i--...... -:...............----...... .............. ........ :.............

-F............ • ...... A'- ........ -• ......... -:.......... .......... ". -'......... ......................

*. ...

. ... . ..

I . , :.

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

• .... ......... .... . ..... .. ."...... ••.... .., ... "• •. . ......... ..•........ ... ...

I i i : : "

i .......... ...........

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

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

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

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

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

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

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

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

..........

..........

...........

...........

...........

...........

...........

...........

...........

...........

...........

...........

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

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

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

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

...........

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

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

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

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

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

-1.0

-e.8

-6.6

-6.4

8.2- -0.2

120 308 400 Sao GOB 700

tTLOUJ3759O .... . f13DT st3RtflK

Figure 7 : Measured and calculaled break flow C Base case )

T:"',

Tine
lafffLb

NU

C)

6w8-

4W8

Semiscale S-I.II-

........... ..........-................................ ........... •.......... .......... .......... .......... ..................... .......... ..................... .* ..........

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

"." :. .....I.......... . .......... .......... ........... .......... .,..........- .......... .......... l.......... ÷............ .......... .. .......... .......... ...........

:I I I _ : "i

:*i i 4 . - ij i . "

. ,

:11 i . :: 4 

.•...-.. .......... " . ...... ........... .......... ;..........."...... i............ . ................. . ........ ....•......... -.......... ..... I.....

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

.. a...f.. I .

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

... .. l. ,.............. . ... ........ .. .......... • ........... .......... ... ...- .......... :.......... ............... : .......... I .......... 7 .......... I .......... " ..........

RELAPSM" U)C UPS 

•" ' "t " ....... . "..... ...... .......... "............ ".......... ...................... " .......... .......... '......................... "--...... ".......... .............

.. . .. = ...........

. I I . : I I

-400

8>O-

-g

a188 28e 308 480 ;OO GO8 78

CflRlnKu? .__ LIP#9?1-S7E ... CITRLUR ......... LIPM7I-S?X

Figure 8. Collopsed Liquid Levels In InLocL Loop U-Lubes

0 s88

Time I s
SEMISCRLE S-LII-I

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

I•

•;:...i5.......--- ......... " .......... i.......... i........... .......... i.......... •............i .......... .......... ".......... i.......... :......... .i.......... !......... .. , .F Ditti',[ &D[ " I " .

..... ".. .... ....I.........." .......... .......... ;.......... .. .......... •...........• ........... .......... :.......... •. .......... :.......... ;. ..........- .......... ...........

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

"- .

...... A. ............. ........... .... . ...... .

•

ide, 2 0 *4.40.e GO e e

..1 C .. .

Fi8r 9. C Lqi Lev s I B 8

• : , .... .......... •--: ... ... ." \t'- ....................... ..

CflTT•t.•Il __LOPSFHS3 -S?[ .... l:TRLUARl2 .... LOPSCBS3 -SX ....

Figure 9. Collapsed Liquid Leuels in Broken Loop U-Lube
. 1,- C

Semiscale S-L[I-I

s •- ---:-- ~..--. ......... ,.........q............. ........... ........... ...... ..... .......... ...... :'-- ............ •..... i•..........•........ .......... ......... '.. .......... - e

S W ...................... ................ . ,

I Down flb sk ~ide

.~i. . ......................... ....... ................ ........... .................... .......... ...... ..... ........... ................ ......

.. .... ............... " ...... .......... .. .. ......... ...... ... . ;.... . ................-.. . .. .... ... . .. ... . .. ...... .. . .. - ...-

!- ....... ,:...:.k ... :'~...• .......... :.... ....... . ...... ., ......... . ... .... ... ........... '..... .... '. I.....:..... i..... "...... :.... ...... i ..... "...... ..-.........

E

: .• :.L .. ... i.. .. •... " ............. L .. .• ................ ..... ....... ...... ..... ........ .. ........... .. .................. .............. ....... ......... .. ...... L....,...... _,, S ....

,...... . . . . . . ..... .. .. . .. . . . .. o.... ....... . . . .......... . :.. . . . .... :. .. .... . .. . .. . .:... .......

.............-. r,,g ""• " • • . ... ....... :... ......'................' ........... ...... .. ....... .. ... ... ..... ... ..

... ".. . ..... .... ...... " --

O ~ U l~~(ow:,.sdeIl ............. .... : ..................... ................. ...................... .. ... ......

...-. ... i ...... ... .. ... , • .. ..... ....... ... ... ..... ... i .. . .i .. .. .i -... .... :•... ............ ......... • .•......

.. ....... ....... ' Ciculaled .i1asurcd I. .. . .. .. ........ ..... .. . . ..... ...... ........... . . . . .. . . . . ... .: . . ., . ., . . . - . . •. . . .... . .. I. . . . . . . . .:. . . . .. ....... .. .......... .......... ....

S I* '1 

o ,•.i•. ... .......... . • . . 8 Cwm: both .s.4t sutIon

t..• o i... 440 SA ..... GI..... 0' o 0o !... ! 800".... • o : ,:, Il I I I iI 

CtiTRLtI'R9 DPI-S7XtlI4 CNTRLUI)RI8 DPlt14BtlG

FigureI.: Measured and calculaLed IL pump suclion collapsed liquid level
U

200-

100

Semiscale S-LH-I1

. .......... ....................... "............ ......... '........... ;.............. .......... ;........... :............ ...................... . .......... " .. ....i.......... : ...........

* *

li i I " ...........

I Ooun f Ibd 3ide

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

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

. . ..... .. .. . .......... .......... { ........... ........... .. . ........... . . ....................... o..................... .. •............. . . . . .

/- : . s..• ... ..... ...... .... ... .. .... .... I .......... • ........... .......... ...... .......... ........................ ... ............... ...................... ....................... .......... .. ..... ! .............. I... .................

rr~nwr4d

... ............ ............. ... " ............ . . ............ . . .... ....... .......................... ...........

... ...I i ...... ...... .. .... . ........... ............. .... ... ............ .:........... ... ..

If'

o .° , ..• ., ................ ............... ..... .. . . ....... .. .......... ........... .......... .........................

CalcmlotedC e1'

........... " ".. . .. ........... 1.... ...... *T ............ ......... •...................... ........... ... ...,........... ............

SI '; , -.

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

100 . 20 301 400 Goo Goo 700 Soo

-S88

-'180

-300

( 5

Ti

CHTR-LIAR13 . )DPB-S7XIGSA CMTRLUPRI4 . _ _ DPBsGSt73

Figure Me: aeasured and calculaLed BL pump sucLion collapsed liquid level

if#3
Semi5cOle S-LIH-1

20 * :200

I1 w, .................... .................. ........... : ........ ...................... .......... ............ ........... ............ ......... .......... ... ........ . . . tee

.... ... _.. . ........ .......... ... .............. . ......... ....................... ......... ............ ..

E- / (~oko~i~ror Ilquid let-elj: /,\ I\ lo'°,,'•" ',

...... ...... ...... ...... ... ........... ........... o.. ., ....... : ...... - .: ..-........ -.--... .Jo

• . 0 , .... ....... . ..... . ............. ....... . . .. .. .. . . . .., - . . ... . . .......... .... . .. ......... •........... . - 0

i i i i, "q i100

11:t :.\ • : • . ri

*- :[,1 c . * .alcula ed - ..... .. *...... . ......... .-.. L. . . ...... ......... . • ,,.X .. ...........L .,. ."..... .. ... . ......... 0"

-3001- ; ..-. •. ,J380•.

O ~~:.VesteI IIquld let-e>l~

0

, 40 .............. .... 1.................. 1:.....• ..... ........ ............. ................ ..... .....

4,, - . .......... ..... ,.. . ................... , . . . .... ....... .. .. ........... ... ............ ...................... ............... ......... ............................ .. 40

-49G ým Is bdttomor :heaLed Core:

-2M0 jm 13 bdttoI ol opuWP 5UCtion :

-138 .' 15 tdp of cote " acn Is cold le3 dentrelIe . . .. . .. .....

..I..............I..................8 ' ........ 3600 

0 100 208 300 400 SaOO GOB 708 B0O

"luis ( s

CfITRLUIR3 . LVD#29-S78 - CTRLUARI . - LV-13tl-S? -

Figure 12 : Uessel and dotwmncomer collapsed liquid leuels ( Base case )
Semiscale S-LH-1

0

0

1.1

1.0

0.9

0.8

0.7

0.8

0.5

0.4

0.3

0.2

0.1

0.0

100 125 150 175 200 225

Time after rupture (s)

250

wilik51B."

Figure 13a : Measured vessel axial void fraction distribution during the manometric depression

C

0

1 . 01

0.0 342 cm 253 cm 1¶83 cm

0.8

0.7

0.6 m

0.4

All elevations above Un

0.3 bottom of core 12 cm

0.2 ry4A~vlW

0.1 Accumulator Injec

0.0 I I

300 350 400 450 500 550

Time after rupture (C)

I i I

certainty ±.02

tlon

600 650 700

. wafese.4e

Figure 13b : Measured vessel axial void fraction distribution during core boildown

25
Semi5cale S-LI-I

UISIOD1 PEFEREIICE FILE STD-DECKJM-1H-1:2

0.8-

€

a

tU

V

t.

"5-

0.4-

0~'

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

A .... o.o~.... °.. .... i..... ...... p. .... ...... .... •...... ..... o..... . °o,........ •............ ........... ......... ................... ,. .....° ............. ......... °o.... .......

.19I1 leva t ibn aboe.eý

::~~ A .hotto,s b! coec

heated length m

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

SIPi I

........... .......... ,:.... ..... , ........................... .. ........ ............. ! .. ................. .......... .. .......... .. ........ .. ......

....... ...... .. %• i" " ...... = ' ' . . . ."•' .....

H i% .. ....... ........ ....... . -...-.•. : . .: -..- . _= .

.'. . .. ,....

... ...-- ....... -. - ....... ................... ............. .... ......... ......... k.. ......... ...... .. .. ......

:IR

. . o .~ . . . . . o .. *- .. .... .. . . . . . . . . .. . . . . . . ................ __ .o • .. .. . .. . .. . . . . , ... . . . .. . . ... . .. . .. . .

. I "',,,. . .. .... I ...

oie208 309 408 Goo GOO 700 S0o

U0IDG088 .......... WIDGIS002 ........ 83 .. IDGIS9B - V0 1S05 VOI9GI

Figure 14 :ClculaLed core void frc.ions

8

3

8

8

0

0.2

0.0-
Semiscale S-LII-I

700-

Z

:3

-4 lo

E

F0

........... ............................................. ... .......... ................................ ......... -4 ."..... .......................

.. ....."...........'............. ..... - ......... . ........... ..... .......... -.......... ;........... . / ..... -.............. ... .. ......... . ........... . .......... ' ' ""• . i''''''''' '' *I

.4 I..

...... ............... .................. .... :.. .... ..... ..,.. ....•.......... . ..... ............ ........... •........... I ........... ......... ., .. ........ ........... ........... I ........... ,........... ,............

-\ ...... .......... i ........... .. .. . ........... .. . " ............ .......... !...... ............. i .......... i i........... ...........

.... .,........... .. ...... . ......... . . . .......... .. ................ ........... ...... .......... .. ......... .......... i ......... ............ . , ........... -.......... ....... ..... ... . ... ..........

' . • • -. :. ....... . .... .. ... . .. .... .... .. . .. .... .. .. ..

....... ..... .............. . ......... ... l.t .. .. .. ... ..................... i .: . ,. ..--- ..-- .- . ...... .... • .. . . .......... ........... i .......... ... . . . ........... i. . . . .

.... • .

Ilensurelf

....... ~.............. ........ ":........ . ............ . -...... ....................... "....... -",, ... .............. "............. .. .. .. .......t ...........

.:.. . . m •.... 

I" :v "-,

. ...................... ... . ............. ...................... .... .. ... .. "............. ............ . .. .! .. .. • -'" 4 .......... - - ..-- . -......

0 180 1 200 I 300 I 400 T SOD I GO0 I 0708 800

-700

--IS

71"a3 ( S )

I'PIS608918 .- - TIPI'AS251 -

Figure 15 : Measured and calculaLed heaLer rod lemperaLures ( Base case )
ONE VELOCITY

JUNCTION

CORE INNER

ZONE,CONTAINING

HEATER RODS

CORE OUTER ZONE,

CONTAINING NO

HEATER RODS

FIG.16 RENODALISATION OFTHE CORE

28
Semiscale S-LH-I

tB0~

U

,.- -100-

a-1

i-300-

10

0

U

I

*1.,

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

.... 0 u c he .. .. .. .....

P.

N: IT

.. .... .

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

... .... ...... i ... ..

............ e/ .

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

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

I Studgj

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

Butq~

F F..

.............. .........r "..... ...........

..,.°....... ........ °..• ............

.......... °,° ..........

°.,.........•........... D............

.. °........ . .......... . ...........

?...... 

700 I 8013 0

-l1B

-- l

-- 100

--_200

-- 300

-- 400

.•0

-b"017 vv• I

0 10l 200 300 400) Goo G08 ,-.6uu

line ( s )

Cl1TRL•AR3 .- _ CITRLU•3 ........ LLO#29-578 - CHTRLVARIOI .- CHIRLUAIR ........ LU-131"-S79

Figure 17 : Comparison of vessel and douncomer collapsed liquid levels
0.i C

C,

.1

U

a

L

LA,

A

VISIOII REFEREMIE FILE COREIJ4.2:S-LUi-1:?

Semiscale S-1H-1-1

li ) ....................... ... . . ... ........ ............ ............ ..-0

.. .~. ...... ..... . . *

...... ,....

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

L'. 4 90 

,' ~."Jog

ItI 0..... 10..... . .08 4 ...... ............. .......70........

[....... 0ILIDI4R V!3G4~ILUDI4O ... ....... .............

e.8..lula ed .....or vo........d .. a ........ o ..... ...... .en.iti .it .... tudy ....... ). ......
Semiscale S-LH~-1

700,-

I.

3

*1

a

L

0

a.

2

0

ICalculat.d

.evn 25 I

... L..... ................. .......... . .... ..... ............. .. ...... ........ l .... ........ .....

S1At

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

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

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

IieasreU I I251 cm 1! evatonkr

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

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

-780

-~e8

-558

500, -Be

a 1N 200 3N 400 So8 coo 788

1EtPI4980919 .s ASi 5'2S -I

.Figure 19 : Measured and calculaLed heaLer rod LemperaLures

I 9138

TIrrt~ ( ~ I
Distribution (S - Summary only)

S

S

P.M.

B.V.

I.L.

P.D.

K.H.

P.C.

F.M.

Billam

George

Hirst

Jenkins

Ardron

Hall (6)

Evans

GDCD

GDCD

GDCD

GDCD

GDCD

GDCD

GDCD

PMT

PMT

HSD

HSD

HSD

S R. Garnsey

N.E. Buttery

S J.R.

P.R.

A.C.

Harrison

Farmer

Willetts

S E.W. Carpenter BNL

A.J. Clare BNL

M.W.E. Coney CERL

A.H. Scriven CERL

J. Putney CERL

L.F. Wilson CISD Park Street

S D.A. Ward NNC

K.T. Routledge NNC

P.A.W. Bratby NNC

S D.A. Howl

K.W. Hesketh

S M.R. Hayns

I. Brittain

I.H. Gibson

C.G. Richards

W.M. Bryce

Library G

Library B

Library C

Library M

Library S

BNFL Sprinfields

BNFL Springfields

UKAEA

UKAEA

UKAEA

UKAEA

UKAEA

Winfrith

Winfrith

Winfrith

Winfrith

Winfrith

DCD

NL

EEL

HL udbury House

32
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

(2-89) (Ag*I-Wd by NRC. Add Vol., Sup9., Rav., NRCM 1102, Ond Addendum Numb*r". If any.)

3201.32 BIBLIOGRAPHIC DATA SHEET

(See instructions on the reverse) U EG/IA-0064

2. TITLE AND SUBTITLE GD/PE-N/725

Analysis of Semiscale Test S-LH-1 Using RELAP5/MOD2 PWR/HTWG/P(88)629(Rev)

3. DATE REPORT PUBLISHED

MONTH YEAR

Apri l 1992

4. FIN OR GRANT NUMBER

A4682

5. AUTHOR(S) 6. TYPE OF REPORT

P.C. Hall, D.R. Bull

7. PERIOD COVERED (Inclusive Dates)

8. PERFORMING ORGANIZATION - NAME AND ADDRESS (lf NRC. provide Divsison, Office or Region, U.S. Nuclear Regulatory Commission. and mailing address: if contractor, provide

name and mailing addrsx)

National Power Nuclear

Barnett Way

Barnwood, Gloucester GL4 7RS

United Kingdom

9. SPONSORING ORGANIZATION - NAME AND ADDRESS oIf NRC, type °Tte as above ',if contractoro provide NRC Division, Office or Region. U.S. Nuclear Regulatory Commission,

and mailing address.)

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

10. SUPPLEMENTARY NOTES

11. ABSTRACT (200 words or less)

The RELAP5/MOD2 code is being used by GDCD for calculating Small Break Loss of Coolant Accidents (SBLOCA) and

pressurized transient sequences for the Sizewell 'B' PWR. These calculations are being carried out at the request of

Sizewell 'B' Project Management Team. To assist in validating RELAP5/MOD2 for the above application, the code is being

used by GDCD to model a number of small LOCA and pressurized fault simulation experiments carried out in various integral

test facilities. The present report describes a RELAP5/MOD2 analysis of the small LOCA test S-LH-1 which was performed

on the Semiscale Mod-2C facility. S-LH-1 simulated a small LOCA caused by a break in the cold leg pipework of an area

equal to 5% of the cold leg flow area.

12. KEY WORDS/DESCR'PTORS List words orphrases that will assist researchers In locating the report.) 13. AVAILABI LITY STATEMENT

semiscale test iinl imifirl

Test S-LH-1 14. SECURITY CLASSFICATION

RELAP5/MOD2 (This P••)

cold leg pipework (intl 'sifijd

Small Break Loss-of-Coolant Accidents (SBLOCA) (This Report)

Iwfll •q fi mc

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 12891
.THIS DOCUMENT WAS PRINTED USING RECYCLED PAPER

NUREG/IA-0064 ANALYSIS OF SEMISCALE TEST S-LH-1 USING RELAPS/MOD2 APRIL 1992

UNITED STATES

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