NUREG/IA-0065

~GD/PE-N/745'

PWR/HTWG/P(89)708

International

Agreement Report

Analysis of Semiscale Test

S-LH-2 Using RELAP5/MOD2

Prepared by

P. Brodie, P. C. Hall

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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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

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NUREG/IA-0065

GD/PE-N/745

PWR/HTWG/P(89)708

International

Agreement Report

Analysis of Semiscale Test

S-LH-2 Using RELAP5/MOD2

Prepared by

P. Brodie, P. C. Hall

National Power Nuclear

Barnett Way

Barnwood, Gloucester GIA 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 K'ingdom (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/745

PWR/HTWG/P(89)708

NATIONAL POWER - NUCLEAR

TECHNOLOGY DIVISION

STATION PERFORMANCE BRANCH

Title:

Author:

Summary:

Analysis of Semiscale Test S-LH-2 using RELAP5/MOD2

P. Brodie and P.C. Hall, Analytical Investigation Section

The RELAP5/MOD2 code is being used by National Power Nuclear

Technology-Division 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 and the Health and Safety Department.

To assist in validating RELAP5/MOD2 for the above

application, the code is being used to model a number of

small LOCA and pressurised fault simulation experiments

carried out in integral test facilities. The present report

describes a RELAP5/MOD2 analysis of the small LOCA test

S-LH-2 which was performed on the Semiscale Mod-2C

Facility. S-LH-2 simulated a SBLOCA caused by a break in the

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

area. S-LH-2 was identical to the earlier test S-LH-l except

for an increase in the flow area between the upper plenum and

the cold leg which resulted in the core bypass flow

increasing from 0.9% to 3.0%.

RELAP5/MOD2 gave reasonably accurate predictions of system

thermal hydraulic behaviour but failed to calculate the core

dryout which occurred due to coolant boil-off prior to

accumulator injection. The error is believed due to

combinations of errors in calculating the liquid inventory in

the core and steam generators, and incorrect modelling of the

void fraction gradient within the core.

Task No. G212

This report is security classified. It may be passed to

other people by recipients on the distribution list only on a

need to know basis, and may not be passed to persons outside

the recipient's own organisation without the consent of the

Head of Station Performance Branch.

Security:

Date August 1989.

Approved:

K.H. Ardron,

Head of Analytical Investigation Section

Mi

CONTENTS

1. INTRODUCTION

2. CODE VERSION AND INPUT MODEL

3. INITIAL AND BOUNDARY CONDITIONS

4. DESCRIPTION OF TEST S-LH-2

5. DESCRIPTION OF RELAP5/MOD2 PREDICTIONS

6. DISCUSSION COMPARISON WITH S-LH-l ANALYSIS

7. GENERAL CODE PERFORMANCE

8. CONCLUSION

9. REFERENCES 5

Tables 6

Figures 8

V

1. INTRODUCTION

The RELAP5/MOD2 code [1] is being used by National Power Nuclear Technology

Division 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 and Health and Safety Department.

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

being used to model a number of small LOCA and pressurised fault simulation

experiments carried out in integral test facilities. The present report

describes a RELAP5/MOD2 analysis of the small LOCA test S-LH-2 which was

performed on the Semiscale Mod-2C facility. S-LH-2 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. It was identical to the earlier test S-LH-I except for

an increase in the flow area between the upper plenum and the cold leg

which resulted in the core bypass flow increasing from 0.9% to 3.0%. A

RELAP5/MOD2 analysis of S-LH-l is reported in ref [2].

2. CODE VERSION AND INPUT MODEL

The code version used for these calculations was the same as used for the

ref. [2] analysis (RELAP5/MOD2/cycle 36.05 E03).

The RELAP5/MOD2 model was also the same as that used in ref [21 except for

the loss coefficient for the core bypass junction which was reduced from

2.57 to 0.125. This was found to give the correct bypass flow ratio (3%)

in the initial steady state.

3. INITIAL AND BOUNDARY CONDITIONS

The initial and boundary conditions for the present calculations were taken

from reference [3]. To establish the required steady state conditions a

steady state calculation was first run for 300s of problem time. The

control systems used to achieve steady state were identical to those used

in the S-LH-l calculations, though the steady state conditions differed

slightly from those detailed in reference [2]. After 300s the dummy

volumes and control systems were deleted. The calculation was then

allowed to proceed for 50s as a 'null transient' before the transient was

initiated, to ensure that an acceptable initial steady state had been

achieved.

Figures 1 - 3 show the hot leg pressure and pressuriser level, the flows

into and out of the intact loop steam generator (SG) separator, and the

intact loop SG pressure and level during the steady state run. These

figures indicate that a satisfactory steady state was reached. The steady

state conditions are compared with experimental data, obtained from

reference [3], in Table 1.

As with test S-LH-l the intact loop SG secondary side level had to be set

artificially low to allow RELAP5 to calculate stable operation of the SG.

All other steady state conditions were satisfactorily calculated, however.

4. DESCRIPTION OF TEST S-LH-2

The experimental transient was similar to that occurring in test S-LH-l,

which is described in detail in reference [2].

1.
Briefly, upon initiation of the transient, a block valve off the cold leg

was opened to simulate a break, core power was reduced to represent decay

heating, the feed water and main steam control valves (MSCV) closed and the

primary circulating pumps were tripped. The sequence of events is given in

Table 2. As can be seen there is much similarity with test S-LH-l.

The main difference between the S-LU-I and S-LH-2 tests was that the

manometric imbalance in the pump suction legs did not produce a liquid

level depression below the top of the heated core, prior to loop seal

clearance, and therefore no early core dry-out occurred. Early dry-out did

occur in S-LH-I. This difference was a consequence of the larger by-pass

flow in S-LH-2 which acted to prevent a differential pressure developing

between the top of the core and the cold legs.

The slow reduction in core liquid level due to coolant boil-off observed in

S-LH-I after pump suction clearance was, however, also observed in S-LH-2.

Again this resulted in a core dry-out which commenced at about 525s and was

terminated at about 620s, approximately 50s after initiation of accumulator

injection.

5. DESCRIPTION OF RELAP5/MOD2 CALCULATION

The calculated timing of key events is compared with the experimental data

in Table 2.

The measured and calculated primary system pressures are shown in Figure

4. As with the calculated S-LH-I in ref [2] the calculation is accurate up

to 50s, after which there is a small systematic over-prediction of pressure

until loop seal clearance. After loop seal clearance the calculated

depressurisation is too rapid, indicating a possible overestimation of the

break discharge enthalpy. Accumulator injection pressure set point is

reached at 500s in the calculation, approximately 75s earlier than the

experiment.

The secondary side pressures are compared in Figure 5. Secondary side

pressures are over predicted at all times after the closure of the MSCVs,

as found in the S-LH-I calculation. These errors are thought to have only

a minor effect on the calculations.

The measured and calculated break flow rates are compared in Figure 6.

Periods of underestimation (45 - 140s) and overestimation (230 - 280s) are

evident. Overall, however, as in the ref [2] analysis, the mean flow rate

through the break is reasonably accurately calculated.

Figures 7, 8, 9 and 10 compare the measured and calculated collapsed liquid

level in the intact loop and broken loop SG U-tubes and pump suction legs.

Trends in calculations and the test data are similar to those described in

ref [2].

The larger bypass flow in test S-LH-2 compared with S-LH-I resulted in

later clearance of the intact loop pump suction leg, and failure of the

broken loop pump suction leg to clear at all. RELAP5 correctly predicted

both of these effects. The late prediction of clearance of the intact loop

(250s c.f 204s) was due to errors in the calculated discharge flow rate

noted above.

In figure 11 calculated collapsed liquid levels in the downcomer and core

are compared with experimental data. (Note that the experimental data,

which are derived from pressure differential values, are invalid until the

termination of forced loop flow at about 50s).

2.
Calculations are in fairly good agreement with data and the core level

depression at about 200s, which occurs because of manometric effects is

predicted. In test S-LH-2 the increased core bypass flow resulted in a

manometric level depression which was much less severe than seen in test

S-LH-I. Consequently the severe core level depression which ocurred at

about 200s in S-LH-i did not take place in S-LH-2 and RELAP5 correctly

identified this effect. As in the simulation of test S-LH-l, accumulator

injection was calculated too early in the S-LH-2 analysis. Therefore the

minimum core inventory in the boil off phase (350s onwards) was again

noticeably overestimated.

Calculated axial variations in core void fractions are shown in figure 12.

As in the S-LU-I calculations the core dry-out that occurs in the test at

around 500s is not predicted. Again, as in the S-LH-I case, failure to

predict the dry-out appears to be due to a combination of the overprediction of the liquid inventory in the core, and the calculation of an

unrealistic core void fraction distribution.

Figure 13 compares the measured and calculated heater rod temperatures in

the core, close to the 250cm elevation. It is seen that as discussed above

RELAP5 fails to calculate the rod heat-up associated with core uncovery in

the period 525 - 610s.

6. DISCUSSION : COMPARISON WITH S-LH-i ANALYSIS

The main difference between the S-LU-I and S-LH-2 transients is the pump

suction clearing behaviour. The experimental trends in both tests are

captured surprisingly well by RELAP5/MOD2. As a result of differences in

the loop seal behaviour, the core level depression due to manometric

effects is much more severe in S-LH-l than in S-LH-2. The minimum core

inventory in the manometric depression phase is in both cases calculated

accurately by RELAP5.

In both S-LH-I and S-LH-2 the loop seal clearance was followed by a slow

coolant boil-off phase in which core uncovery and dry-out occurred. In

both cases RELAP5 failed to calculate the fuel dry out in this phase. This

discrepancy is believed due to a combination of over-prediction of the core

liquid inventory, and errors in modelling the void fraction distribution in

the core. It was noted in r-ef. [2] that calculation of the core level

trajectory in such cases is likely to be unreliable in RELAP5 simulations,

in which the core is represented by a small number of nodes. It was

recommended therein that the level trajectory calculation would be best

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

conditions from the RELAP5 calculation. Development of such a model is now

under way [4].

7. GENERAL CODE PERFORMANCE AND CPU TIMES

As with the S-LH-i analysis calculations were performed on the Cray-2

computer at the Atomic Energy Research Establishment (AERE), Harwell.

1516 seconds of CPU time were used to calculate 600 seconds of transient,

giving a CPU : Real time ratio of 2.53 : 1.

3.
8. CONCLUSIONS

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

S-LH-2 (5% cold leg break loss of coolant accident simulation) carried

out in the Semiscale PWR test facility.

2. RELAP5/MOD2 gave reasonably accurate predictions of system thermal

hydraulic behaviour but failed to calculate the core dry out which

occurred due to coolant boil off prior to accumulator injection. This

failure is believed to be due to a combination of errors in

calculating the liquid inventory in the core and steam generators, and

incorrect modelling of the void fraction gradient within the core.

3. The need for a code to calculate core mixture level trajectory, taking

boundary conditions from RELAP5/MOD2, has been confirmed.

4.
9. REFERENCES

1. NUREG/CR-4312

2. GD/PE-N/725 Report

3. NUREG/CR-4438

4. CISD/CC/N1042

RELAP5/MOD2 Code Manual

Volumes 1 and 2

V.H. Ransom et al.

Analysis of Semiscale

Test S-LH-l Using

RELAPS/MOD2

P.C. Hall and D.R. Bull

Results of Semiscale Mod-2C

Small Break (5%) LOCA

Experiments S-LH-I,

S-LH-2.

G.G. Loomis, J.E. Streit

A Quality Plan for RELPIN

G. Ahmed

December 1985

February 1989

November 1985

March 1989

C8917073GJN4/PBl 55.
TABLE 1

INITIAL CONDITIONS FOR S-LH-2

Pressuriser pressure

Core power

Core temperature rise

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)

Leak rate

SG secondary pressure

Intact loop

Broken loop

SG secondary side mass

Intact loop

Broken loop

UNITS

MPa

kW

K

cm

K

kgs"1

kgs-t

MPa

kg

EXPERIMENT

15.42

2007.09

37.17

393

561.9

564.4

7.37

1.99

3.0

0.0002

5.70

5.95

191

48.2

RELAP5

15.42

2007.09

38.4

393

560.8

563.1

7.37

1.99

3.0

0.0

5.74

6.10

150"

48.21

* Approaching limit or stable operation of steam generator by RELAP5

6.
IARI F 2

TIMING OF EVENTS FOR S-I 11-2

EVENT

Small break valve opened

Pressuriser pressure

reaches trip level (12 6MPa)

Pump coast down initialed

Intact loop

Broken loop

HPIS initiated

Intact loop

Broken loop

Pressuriser empty

Minimum core

collapsed liquid level

Pump suction clearing

Intact loop

Broken loop

Core dry out

Accumulator now initiated

Intact loop

Broken loop

TIME AFTER BREAK OPENS (.)

EXPERIMENT RELAP5

0.0 fl.fl

15 91

2065

2065

17.6

22.0

22 0

41.6

41.6

34.8

204.35

205.4

Did not clear

600

575.0

Not initialed

42.4

42.4

53.0

250

255

Did not clear

Did not dry out

500

500

0

7,
Semiscale S-LH-2 : S'eady LaLe

(11

LJS[Ol PrFEPElKIC FILE rLL T:S-IG-0 :2

.21

a

0~

12

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3

di 02 di

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IS

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+ --

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Pr . . . .................................................. ..... .. . . . . . ..................................... :...................................... ........... .............. ...:-q

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

14 .9 .- . ........................... ....................... ...... :............................. -............................... ............................. . . . . . . . . . . . . . ..: .

14 .8 - .. ........................... ............................. 1"............................ ,............................. "............................... ........................... . 7

1 4 . 7 4 . . ... ... ... .. .. .. .. ... ..... . . .. .... .... .... .... ... .. ... ... .. .. . .. ... ... .... .. .. ... ... . '. . ..... .... .. ..... ... .. . . ... ....... . . .... .. .. ... .. ... ... .. ..... .. ... .... ' .

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

4... ... . I II*- , - . . . ..... . ..... .. . ... . . .

0 $0 183 ISO 200 2Sf 3)O

Tiwe in seconds

P26181 ([I I- CtITRIIRG (2]

Figure 1:HoL leg pressure and pre55,riser level
:3

'-0

91S1r'! REFCPE!lE FILE INULLT:-U-Ll-2:2

Semisccle S-LH-2 : SLeady sLate

.................. : ------------------------------- ...................................................... .

rI.................................. ...................................................................... .......................

4 ... . .... ................... A................................................................ ................................................................ ............................ . I l

...

.I.\ 

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

.r 

: : i i ... .... ....... ... ... .......... iii l ... l ..............-...... 

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

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

......

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A . ......................... . ................................ ................................................................ i . . . . . . . . . . . . ............................... . . .

: r ... ................-.............. --- -------- - -. ... ............- ........ .........- - - - ........ ...- .........................-- ------.-. ..

--.:.......................................................... .. i.......................................................... .... I . . ............ .. . .. . ........... ........................ - -a-i---------------------------- -i---------.................... ....................... ... jo 0 00 IS0 200 25O 300

Time in seconds

rYLOWJ601R - tTLOU-IG01 .. trFLLIUG003 --

Figure 2:IL SLeam generaLor mass flow1 raLees
vISioq P[FEPEN.t FrILE RJLLT:S.3111-2:2.

Semiscale S-LH-2 : Sleady sta. e

Ill (21 S............................. •.............................. -........................................................... ..... I ......................... :........... .... ....... ... I; . .

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

......... 'nmnn.n.ný ------- 12

.. .............. ..... *............. . . . . •J "I!i •4 .... . . ................. .................. / -.... i.............................. ............................................................ ............................ ,-v . .. /.. . .

CL * -53. ... .÷ . !3 . 9..

ot

' -.... . .." .. ...................... ......... ....... .............................. ............................. • ............................ ............................. . 9

----- ........... .. ............................. ......... ..................... .................... ......... .'----7

.' " ..... .......... /...... ...... ............... .... .... .... .......................... • .............................. ............................. '...................... .... .• -.3

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

so 100 IS 15 200 2;:O 300t

Timre in seconds

PGI 11 1 - C.Mj43436 (21

Figure 3:IL SI eam genercLor pressure and collapsed liquid leuel
Semi.rcale S-LH-2

1.... .......................... .... - t

. ........... ........... . . ................................... , .......... .......................... ........... ........... .................... ........... L p

k31

l a . . . . . . . . . . . . . . . .. . . . .............. . . . . ..... ................. ....... ...... ..................... .. .. .. ........ . . . . ........ ...... ........... . .... ...... - 1

......... - ----- c

.7..

CalcvQk a

02 ::.- .. . .•........ ................ ...................... ............. ...... ... ... ....... .......... ... ....... • ............. ...... •... .......... .......................... .2 , . ....... 

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

1*1 • .. _ • . . ........... -.. -. . -.-. - . . . . . . . . . . . ....... . . ......... . . . ........ '] .... .. ...... ... . I ... -... - .......... i .......... .. ... .... ......... ..... : . . .. ... i--k

8188 208 300 4009 508 GOO 708 8300

Time in seconds

P281.1 . P111

FigUre 4:rleasured and calcula~ed primary pressure
• Semiscc'le S-LH-2

... ................. , ...... ..•..... .... ........... . ............... ...... .. .................................................... . . ......... .......... .... ....... "":~~~~~~~~~~~~~~~~~~...... ... ... '".....'......•- ! ---.........-...........-..... -:..... . .......... ... ; . .. .... .. ... ... .... ..... ......................... .. ....'............... .............. . .. ... ".. 

•-.• ~ ~ ~ ~....... ....... ............ ...i.. ... • •.S• ! .q....i... ... : - 1 

9--

2I -7....... . . . . 7 . .. . . . . . .. ...... • . . . . . . . . . .... .: .. . . .... . ... . .• . . . . . . . . . ....... •..... ;. . ...... ... .. . .. . . .,......... , . . ... ., .. ...... .

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

: 12

, .. ... • .... ... ..... ....... ..... -. . ...... ........... ;........ .. ....... . . . . . . . ; . . . . . .......... ............... ............ : .... ......... . ... .. , . .......... ......... .

. . . . . .... . . . . . . . . . . ............ .... . ... .: ............. .. ...... : ......... . .•.. ........... .... : ..... " ........... ............ " . . ..... : . ........... : ..... . -

--- - -- -- -- -

• .i. .. . . . . . . . . . . .......................... . . ........ i...... . .............. I i ....................... .......... ......... ........ ........... ........ i . . ... ..... .. i8180} 280O 280 400 SOD GOD 700 2003

Time in seconds

P's8-• ..... •GI1.G .* PGI. PS 7 ..... 

Figure S:leasured and calculcded secondlory pressueres
Semincrile S-LH-2

f

:3

5~

ii •a

'110* 2038 ~ 300 4'09 Soo3 GOO 700So

Tirre in seconds

MFLOtM7,e88 MIOTeIRRIu ___

Figure G:Meosured and calculoLed breok filor
Semiscale S-LH-2

10o .. . .. . . ... . . . . . . . . . .. . . . . .. . .. . .. . . . . . . . . . .. . . . . . . . . . . .. . . ... . .. . .. . ..... -1 0

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

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

90 ... . u.K......... ............. .... . ..... ......... .. b . . .. . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . .

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

..... .. . . .f i ~ ... .. .. ... ..... ................ .

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

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

......... .. .. .*.. . ... . . c v .D v l . . . . . . . . .. . . . . . ... . . . . . . . . . . . . . . .

' . .4; ..... .............. .. ....... ..... . . ......

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

..... .~. .~ . ... .~ . . . . . .' . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . .. . . . . . . . . .

0 too 200 288 400So 6%, 700 see

Tinve in seconds

C!1TPLVAS37 LIP.971 S7E - CMNRLLJARS29 LIP#971-S7X___

Figure 7:Col lapsed liquid level in IL U-t~Ubes
Semiscale S-I.H-2

to• ....... 1 ... ........... ............ !........... " ............ ":...................... ............ ........... !........... :..........":...... ........... .. . . . . ... .. :.. . . . ...- •

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

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(

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

. ... .. ... ....... ... o .\ c b t la w ,,. .......... ..... ..................... .ý~..

1C I ;

.. .... ...... .. . ...... .......... .......... ........... i........... i......... i.......... ........... i.......... ........... !. . ... • . ... .. ii i '

." .. . ..... .." ...... " . ... , : 3 ... . -.... '.. ... ... ..... . .. . .. . q. . .......... : ........... . . . . .." . . . . .. . . . . ..: . . . . . . . . . . . . . . . . . z

: .. i...... i .." ...... • : ''" .... i"'".... } ....... ... .....".......... :......i... ... ....... ..... ...... ...... .............

.. .... ..... ..... ... .. .. ... ............ . .......... ..... .... _ . . . . ..- -: . ._. ! '

wct2 ~~~-- -00 --------

"". . . . . . . . . . ........................ T...................... I............. . . ........... . . 1........... .................. ....................... " ......................

0 I0 200 300 • 480 We GOO 70:0 goo

Tire in seconds

(3-uIs4, . OPSS3-S-? c ~r•.M5 .. LOP-C400-S7X

Figure 8:Collapsed liquid level in' BL IJ-Libes
Semi:5cnle S-LH-2

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

IDzvq,ý Flow:A~,4~

~~~....... .... :........ ..... . . .. .

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

...... ............ ~ ~ I ... .. ................... ...... _

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

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

. ......

02r- 1r 0 0 0 o o 0 0

Ir inscod

CMPI'R9DISXt9 M1tW9DliRt

Figure 9:Meaured and CUCcIak'.Iiumkscio olape lqudIe
Semisccile S-1-1--2

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

5 9 . .. .. . .. . . .. . . -- -- - -- -- - -- --- - - - . .. .. .. .

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

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

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

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

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

L........,.. ....

'% R1 7 v S l .... .. .. .P- .... .... .................. .- .. . .

Figure................. r'e n... uot ....... e BL ... ...s c ion.. ........ i.id .o .cpsc .....
Semin:cczle S-LH-2

E

3

CO11L

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

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

.......................... ....... ....... ..................... ......., .......... ........... ......-.

LI .$j

.. .... ... ( i .. k.. .. 2. .... ........ .... A 1'0

4,/

................. ...... ....... ............. *......-.. .. . ........ .......... .

0 too 200 300 400 Soo 600 700 800

Tirre in seconds

CrNPIXRA3 .L'AD.29-S78 -__ CNT11~RUtQ . _____S

Figure 11:Vessel and doLwnComer collapsed liquid levels
VISIOtl PEVEPUiKE FILE TPM~S:3 -Ll4-:2-

Semir-iacle S-LH-2

I.-

0. -

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

S, - . . . . . . . . . . . . . . . . . . . . . . ........................... . . . . . . . . .. . . . ............... . ........ ................. --- --............... ---- ----................. . . . . . ..! ,

-- - ..(lpA: .. :

. . . . . . . . ........ ... -.-. , -- - t

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

....... . ... .. ... • ..._ .- .. .... . .' ." '. a.. . . . .. -" --- -" --- ----." • ... . . .. . .

... :. .. .. .. .. .-

-----. ----- .. - -... . ............... . . .. t . ... • ..... . .. .-... ...... -... : . .. .... .. ..... .......... .... .. ......... ............ .. : . . . . . . . .

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

"" " ........ "" .... ".................. .. 4.. ..

. 4. • .. . .. . . . ... .." . .. .... ...... ...... . . ...... .......

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

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

• -. . . . . .,"1 " .... .... .. .'-. ........... ......... --.-- --- .............. .. .. ..................................... -- ----- .-.................. --- .. ..'-- 0... 

• 100 20•0 0 o O

Time in seco~nds

VOIDG1S801 -__ UJOIDGISe82 ..... LJOTDGIS883 L. UIDGfl1304 - OIOGISROS - UJIDGflSOOGFigure 12:Calculoted core void frocLions
Semiscctle S-LH-2

i .. ....- . . .. . .. . .. .. .. . . ... . . . .

to r f e . . . . . .. . . . .. . . . .. . . . .. . . .. . . . . . . . .. .. . . . . . .. . . . . . . .. . . .. . . . .. . . .. . . . .. . . .

0 -5 - -- k 5--8o0e 

-------- :560

Co~c~AoCA 9,ý- ni,-

0 1$30 280 308 4130 Soo 600 78 8800

Tifre in seconds

TCEPt0OM918 TR~tPAS#251__

Figure 13:Measured and calculated heater rod Lemporotures
Distribution (S-Summary only)

S

S

S

S

S

S

S

E.W.Carpenter

P.D.Jenkins

K.H.Ardron

P.C.Hall (4)

P.Brodie

A.Wall

G.S.Harrison

B.Chojnowski

M.J.Whitmarsh-Everiss

R.Garnsey

N.E.Buttery

A.D.Rowe

J.R.Harrison

P.R.Farmer

M.EI-Shanawany

K.T.Routledge

J.Rippon

P.A.W.Bratby

Library

NP-N BNL

NP-N Barnwood

NP-N Barnwood

NP-N Barnwood

NP-N Barnwood

NP-N Gravesend

NP-N Wythenshawe

NP-N MEL

NP-N Barnwood

PPG

PPG

PPG

HSD

HSD

HSD

NNC

NNC

NNC

Barnwood

S

21.

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

(2-891 (Aalmad by NRC. Add Vol.,. S'Yo.. ,. NRCM 1102. and Addendum Numbers, i my.. 32o1,3202 BIBLIOGRAPHIC DATA SHEET

(See instructions on the reverse) NUREG/IA-0065

2. TITLE AND SUBTITLE I U/PE-N//4b

Analysis of Semiscale Test S-LH-2 Using RELAP5/MOD2 PWR/HTWG/P(89)708

3. DATE REPORT PUBLISHED

MONTH j YEAR

Apri I 1992

4. FIN OR GRANT NUMBER

A4682

S. AUTHOR(S) 6. TYPE OF REPORT

P. Brodie, P.C. Hall

7. PERIOD COVERED (Inclusive Dates)

B. PERFORMING ORGANIZATION - NAME AND ADDRESS (If NRC. provide Division, Office or Region, U.S. Nuclear Regulatory Commission, and mailing address, If contractor, provide

name and mailing addets.)

National Power Nuclear

Barnett Way

Barnwood, Gloucester GL4 7RS

United Kingdom

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If NRC. typ "•Same as above-, it contrator, provie NRC Division, Office or Regon U.S Nuckat Regultory Commisin

and mailing address)

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555

10. SUPPLEMENTARY NOTES

11. ABSTRACT 1200 words or less)

The RELAPS/MOD2 code is being used by National Power Nuclear Technology Division for calculating Small Break Loss of Coolant

Accidents (SBLOCA) and pressurized transient sequences for the Sizewell 'B' PWR. To assist in validating RELAP5/MOD 2 for the

above application, the code is being used to model a number of small LOCA and pressurized fault simulation experiments carried

out in integral test facilities. The present report describes a RELAP5/MOD2 analysis of the small LOCA test S-LH-2 which was

performed on the Semiscale Mod-2C Facility. S-LH-2 simulated a SBLOCA 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 behavior

but failed to calculate the core dryout which occurred due to coolant boil-off prior to accumulator injection. The error is

believed due to combinations of errors in calculating the liquid inventory in the core and steam generators, and incorrect

modelling of the void fraction gradient within the core.

12. KEY WORDS/DESCRIPTORS (List words orphrases that will assist resear•hers in locating the report.) 13. AVAI LAB LITY STATEMENT

Semiscale Test S-LH-2 tinlimitpd

RELAP5/MOD2 14. SECURITY CLASSIFCcATION

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

pressurized transient sequences wwnclassifird I

(This Report)

pnrl aq,-ifiPri

15. NUMBER OF PAGES

16. PRICE

NRC FORM 335 (2-89I
4'

THIS DOCUMENT WAS PRINTED USING RECYCLED PAPER

NUREG/IA-0065 ANALYSIS OF SEMISCALE TEST S-LH-2 USING RELAP5/MOD2 APRIL 1992

UNITED STATES

NUCLEAR REGULATORY COMMISSION

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