NUREG/IA-0093

International'

Agreement Report

RELAP5/M\OD3 Assessment for

Calculation of Safety and

Relief Valve Discharge

Piping Hydrodynamic. Loads

Prepared by

E. J. Stubbe, L. VanHoenacker, R. Otero

TRACTEBEL

Avenue Ariane 7

B-1200 Brussels

Belgium

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-0001

February 1994

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

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by such third party Would not infringe privately owned rights.

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U.S. Government Printing Office

P.O. Box 37082

Washington, D.C. 20013-7082

and

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For %ale h,, the U.S. (hniernicni Printing Officc

Supcrintendent oflD~munients. NljiiI Stop: SSOP. Wji~hington. DC 204tt2-932H

ISBN 0-16-043119-0
NUREG/IA.-0093

International

Agreement Report

RELAP5IM\OD3 Assessment for

Calculation of Safety and

Relief Valve Discharge

Piping Hydrodynamic Loads

Prepared by E. J. Stubbe, L WnHoenacker, R. Otero

TRACTEBEL

Avenue Ariane 7

B-1200 Brussels

Belgium

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Washington, DC 20555-000

February 1994

Prepared as parn of

The Agreement on Research Participation and Itchnical Exchange

under the International Thermal-Hydraulic Code Assessment

and Application Program (ICAP)

Published by

U.S. Nuclear Regulatory Commission
NOTICE

This report documents work performed under the sponsorship of the Tractionel of

Belgium. The information in this report has been provided to the USNRC under

the terms of an information exchange agreement between the United States and

Belgium (Technical Exchange and Cooperation Arrangement Between the United

States Nuclear Regulatory Conmmission and the Tractionel of Belgium in the field

of reactor safety research and development, April 1985). Belgium has consented

to the publication of this report as a USNRC document in order that it may

receive the widest possible circulation among the reactor safety conmmunity.

Neither the United States Government nor Belgium 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.
JPD/5N1 7

RELAP 5/MOD 3 ASSESSMENT FOR CALCULATION OF

SAFETY AND RELIEF VALVE DISCHARGE PIPING

HYDRODYNAMIC LOADS

TABLE OF CONTENTS

Page

ABSTRACT ........................................................................... 1

EXECUTIVE SUMMARY ........................................................... 2

1. Introduction....................................................................... 4

2. Objectives........................................................................ 5

3. Basic data :EPRI / CE test facility description.............................. 6

4. Relap 5 simulation of the EPRI/CE experiments.......................... 8

5. Mechanical loads determination........................................... 15

6. Analysis and results........................................................... 16

6.1. Test 917 (Crosby hot water loop seal discharge) ............................ 16

6.1.1. Results with the original MODI model (CASE 0) ........................ 16

6.1.2. Results with bundle interphase friction (CASES 1 and 8) ............... 15

6.1.3. Sensitivity to the horizontal stratification option at junctions (CASE 2) ... 16

6.1.4. Sensitivity to the abrupt area change model at expansion (CASE 6).....19

6.1.5. Effeact of heat slab modeling (CASE 7) ................................. 19

6.1.6. .Effect of vertical orientation of segment 2 (CASE 4)..................... 19

6.1.7. Results of a fully choked solution downstream the valve (CASE 9) .....20

6.1.8. One velocity solution in RELAP 5iM0D3 (CASE 10) .................... 20

7. Run statistics................................................................... 21

8. Conclusions ................................................................... 22

9. References.....................................................................2ý4

10. Attachment: microfilm (CASE 4)

RELAP 5/MOD3

JPD/5N17 1

This report presents an assessment study for the use of the code RELAP 51M0D3/5M5 in

the calculation of transient hydrodynamic loads on safety and relief discharge pipes.

Its predecessor, RELAP 5/MOD!, was found adequate for this kind of calculations by

EPRI. The hydrodynamic loads are very important for the discharge piping design

because of the fast opening of the valves and the presence of liquid in the upstream loop

seals.

The code results are compared to experimental load measurements performed at the

Combustion Engineering Laboratory in Windsor (US.A.). Those measurements were

part of the PWR Valve Test Program undertaken by EPRI after the TMI-2 accident.

This particular kind of transients challenges the applicability of the following code

models

- Two-phase choked discharge

- Interphase drag in conditions with large density gradients

- Heat transfer to metalic stuctures in fast changing conditions

- Two-phase flow at abrupt expansions.

The code applicability to this kind of transients is investigated. Some sensitivity

analyses to different code and model options are performed. Finally, the suitability of

the code and some modeling guidelines are discussed.

RELAP 5/MOD3
JPD/5N1 72 2

EXECUTIVE S5UMMARY

In 1979, following TMI, the US Nuclear Regulatory Commission (USNRC) recommended

utilities operating nuclear power plants to develop a program in order to test the

performance of the valves which were used in the reactor primary coolant system. The

program was undertaken by EPRI as requested by those utilities.

The objectives of the EPRI Safety and Relief Valve Test Program were the following

- To test the full scale operability of a set of valves representative of those to be

utilized in PWRs over the full range of fluid conditions under which they were

expected to operate.

- To establish a basis to evaluate discharge piping configurations and supports.

From all the loads considered in discharge piping design, the transient hydrodynamic

loads are particularly important for safety and relief valve discharge piping since the

opening time of the safety valves is very fast and can induce large hydrodynamidc forces

on the downstream piping, especially when water solid loop seals are present. An

accurate solution of the dynamic evolution of the fluid inside the piping is required in

order to evaluate the hydrodynamic loads.

The safety valves were tested at the Combustion Engineering experimental facility at

Windsor, U.S.A. The discharge piping at that facility consisted on 4 pipe segments.

Loads were measured at the supports of those segments that were made as stiff as

possible so as to reflect directly the transient fluid loads.

RELAP 5/MODI was selected by EPRI to verify its application to calculation of the

transient hydrodynamic loads. The RELAP 5/MOD1 results were satisfactorily

compared to the measured data. The structural effects were considered by processing of

the RELAP 5/MOD1 predicted loads with a dynamic analysis structural model.

The goal of this report is to repeat the validation performed on RELAP 5/MOD] over

its updated and improved version RELAP 5/MOD3. The changes introduced in this

latter version (mainly the addition of a 6th field equation and improvements in the

empirical closure relations as compared to MODI) could eventually modify the results

of the former validation. The objectives of this validation process can be summarized

as follows'

- Assess RiELAP 5/MOD3 for predicting safety and relief valve discharge piping

hydrodynamdc loads

- Propose modelization guidelines

- Highlight the impact that the different physical models in the RELAP 5

versions have on the piping load results.

RELAP 5IMOD3
JPD/SN 173 3

From all the tests performed at the Combustion Engineering laboratory the ones

involving loop seal discharges have been chosen to benchmark RELAP 5/MOD3. The

reasons (or that choice are the following

- liquid loop seal discharge induces the largest loads on the piping supports

- the discharge of a liquid slug through a valve and its attached pipes is a very

fast two-phase process that challenges the applicability limits of the code.

Neither code changes nor result postprocessing have been performed in order to

evaluate the induced loads (the code does not calculate them). The loads have been

calculated with the appropriate control blocks available in RELAJ' 5 put together with

the aid of TROPIC, the TRACTEBEL's preprocessor code for RELAP.

The conclusions that have been obtained In the assessment process for RELAP 5/MOD3

are

1. -The effect of heat transfer to the pipe heat structures need not be modeled for a

correct evaluation of liquid discharge loads. This was also true for

RELAP 5/MOD1 but not for RELAP 5/MOD2.

2.- RELAP 5/MOD3 underestimates the coupling between the liquid and vapour

phases giving a lower liquid slug velocity than in the experiments. Although the

maximum loads are quite comparable to measurements, they are delayed in time.

3. - The inclusion of a transition zone between subcooled and two phase choked flow in

RELAP 51M0D3 produces a characteristic two-bump flow that is reflected on the

loads of the downstream piping.

4. - Some recommendations are to be added to the RELAP 5/MOD1 modelization

guidelines. A proper orientation of pipe segments (horizontal Or vertical) and a 2

velocity solution at the valve junction should be considered.

5. - RELAP 5/MOD3 can be considered acceptable to evaluate the hydraulic forces

following a discharge from safety or relief valves, when above options are used

and a suitable safety margin is added for design of the piping support.

RELAP 51M0D3
JPD/5N17 4

1. Introduction

In 1979, following TM!, the US Nuclear Regulatory Commission (USNRC) recommended

utilitics operating nuclear power plants to develope a program to test the performance

of the valves which were used in the reactor primary coolant system (ref. 1). The

program was undertaken by EPRI as requested by those utilities.

The objectives of the EPRI PWR Safety and Relief Valve Test Program were twofold.

On one hand the full scale operability of those valves was to be tested over the full

range of fluid conditions under which they were expected to operate. On the other

hand, a basis to evaluate discharge piping configuration and supports was to be

established (ref. 2).

Several loads are considered in discharge piping design :deadweight, seismic, thermal

expansion, pressure and transient hydrodynamic loading. The last one is particularly

important for S/RV discharge piping since the opening time of safety valves is very

fast and can induce large hydrodynamic forces on the downstream piping, especially when loop seals are present. For the calculation of these transient hydrodynamidc loads

EPRI selected two codes SOLA-NET (EPRI version of SOLA-LOOP code developed at

LASL) and RELAP5/MODI. The application of those codes to the calculation of

hydrodynamic discharge loads was compared to experimental data (refs 3 and 4).

These references showed the capacity of those codes to calculate the discharge induced

loads and to provide appropriate input data to the structural analysis codes.

The purpose of this report is to assess the potential of RELAP 5/MOD3/5M5 (ref. 5) for

evaluating discharge piping hydrodynamnic loads. First, the main objectives of this

study are presented followed by a brief description of the EPRI /CombustionEngineering (CE) experimental facility at Windsor. The RELAP 5 model for the

experiment is described next, as well as the method to compute induced loads. The

results of the study are shown as well as a sensitivity analysis on the most relevant

parameters. Finally the conclusions and guidelines for the code options are summarized.

RELAP 5/MOD3
JPD/5N1 75 5

2. Objectives

As RELAP 5/MOD3 can~ be considered as an updated version of MODI, it is of interest to

demonstrate its applicability to the transients that the first version was validated for.

It is of particular interest to illustrate the impact of the addition of a 6th field

equation and improvements in the empirical closure equations on the calculated

hydrodynamic loads and to gauge the sentivity of the valve opening time and the loop

seal temperature on the induced forces on the downstream piping. The objectives of this

report can be summarized as follows

1- Assess the potential of RELAP-5/MOD-3 to predict safety and relief valve

discharge piping hydrodynamic loads

2- Propose modelization guidelines for this kind of transients and analysis

3- Highlight the impact that the different physical models in the RELAP 5 versions

have on the piping load results.

The results of this assessment process for RELAP5/MOD3 will be presented in next

paragraphs. It must be pointed out that no structural analysis results are given in this

report. The EPRI/CE test rig wasioriginally designed as stiff as possible to allow for a

direct comparison between load measurements and the loads computed with RELAP 5.

The hydraulic snubber supports originally installed were replaced by solid links to

achieve that purpose. However, load oscillations were measured on the supports

resulting from an incomplete rigidity of the structures. This dynamidc load response can

be obtained by a structural analysis code with fluid conditions supplied by RELAP 5.

The maximum load values that are given by the structural codes are also different from

the thermal hydraulic code results. From this point of view the results that are

presented in this report should be considered as partially valid, provided no structural

analysis is done.

RELAP 5/MOD3
JPD/5N 17 6

3. Basic data : EPRI / CE test facility description

The selected safety valves (Crosby, Dresser and Target Rock), representative of the

valves used in most of the plants, were tested at the Combustion-Engineering's Kreising

Development Laboratory in Windsor, Connecticut (U.S.A.). The Major components of the

system are shown in Fig. 3.1. Tank 2 was fed by steam from the boiler of the Laboratory

and served as the driver vessel by expansion or evaporation of the fluid inside it. The

smaller accumulator (tank 1) served as a surge vessel and played the role of the PWR

pressurizer. Fig. 3.1. shows two inlets configurations to the valve :short vertical inlet

and long loop seal configuration. Simulations in this report are done on the latter (i.e.,

loop seal). Outlet piping was divided in four segments (Table 3.1.): horizontal, vertical

downwards with an area increase at its middle part, long horizontal and short vertical

upwards discharging into the atmosphere (Fig. 3.2). Load data are measured for each

of these segments provided the pipe supports were made as stiff as possible so as to

reflect directly the transient fluid loads. To achieve this goal ("limit the peak

dynamic response amplification to 1.1. of the hydraulic forcing fonction peak value",

ref. 2, Vol. 2) extremely rigid supports were designed. The snubbers that originally

supported the discharge piping were replaced by solid links. The pipe oscillation in its

perpendicular direction was restricted by springs. The pipe deadweight was supported

by spring hangers. All those springs were conveniently adjusted in the hot experiment

conditions. Fluid temperature and pressure were measured at the inlet and downstream

the valve. Flow rate was measured by a venturi nozzle at the outlet of tank 1. Different

test valve parameters were measured, including the valve stem position. A summary of

the main characteristics of the instruments is presented in Table 3.2. A detailed and

complete description of the EPRI/CE test facility can be found in volume 2 of ref. 2.

Discharge of fluid through the test valves was made at different upstream conditions

from pure steam to subcooled liquid, as well as hot and cold water loop seal followed by

steam discharge. Transients in this report refer to all the water loop seal discharge

cases available :two cases for the Crosby valve (tests 917 and 908) and one case for the

Dresser valve (test 1017). These tests have been chosen because they are representative

of the normal plant conditions and because they give place to the largest loads. A brief

description of these tests follows.

Test number 917 consisted on a hot water loop seal discharge through a Crosby valve.

The slug temperature ranged from 150*C up to 350*C, the saturation temperature at

Tank 1 pressure. The mass of the liquid contained in the loop seal was approximately of

9 kg. Test number 908 was repeated on the same configuration of test 917, but an orifice

plate was installed at the end of the discharge pipe. The conditions of the slug were

different to test a cold water loop seal discharge temperature from 40 0C up to 3500C).

Test number 1017, over the Dresser valve, had a configuration similar to test 917 (slight

changes due to midnor differences in valve dimensions) and slug temperature identical to

the one of test 908 (cold water loop seal discharge).

RELAP 51M0D3
TO ATM

S-1 0 S-7

UITHOUT LOOP SEAL

F- TEST VALVE

6" OR

8"SCH. 40

WITH LOOP SEAL

TESTVALVEX

SW-2

(-RUPTURE DISC.

ASSEMBLY

SCH. 80

Figure 3.1. EPRI/CE Test Loop Schemiatic
PT09

z

18.00 36.00

103.92

-90 *'*'

82. S0

Leg enrd

PT Pressure

F Force

LS Outside Wall Temperature

TE Fluid Temperature

644.3.1

441,42

-121.84

(-121.46) I

PTIO -139.46

Fx

Fy Fy

Figure 3.2. Dimensions and measurement locations for the Crosby valve tests
JPD/5N1 7 .7

TABLE 3.1.: DISCHARGE PIPING GEOMETRIC PARAMETERS

SEGMENT SCHEDULE AREA (m2) LENGHT (in) INCLINATION

1 6"SCH 40 0.0186364 1.6764 HORIZONTAL

2 6" SCH 40 0.0186364 1.8288 VERTICAL

DOWN

2 12" SCH 80 .0.0655710 4.572 VERTICAL

DOWN

3 12" SCH 80 0.0655710 13.228 HORIZONTAL

4 12"SCH 80 0.0655710 0.4572 VERTICAL UP

TABLE 3.2.: SUMMARY OF INSTRUMENT CHARACTERISTICS

PARAMETER TYPE TRANSDUCER SYSTEM FREQUENCY SCALE RANGE

ACCURACY (% RESPONSE

full scale)

FORCE Strain Gage ± 0.5 400 ±445 kN

Load Cells

PRESSURE Strain Gage ±0.27 >1000 0-3500 psia

Diaphragm

TEMPERATURE k Thermocouples or ±2.29C 10 or lower 0-430*C

Platinum RTD

POSITION Linear Variable

Differential

Transformers (LVDT) ± 0.25 250

RELAP 51M0D3
JPD/5N17 a

4. Relap 5 simulation of the EPRI/CE experiments

Modeling guidelines developed for RELAP 5/MODI application to calculation of

hydrodynamic loads were assumed as a starting point. Those guidelines can be taken as

more or less generic for any finite difference code applied to this kind of computation

and can be summarized as follows

- control volumes should have a length between 0.5 and 1.0 feet (0.1 to 0.30 m) to

prevent numerical diffusion.

- time step must be limited. externally since RELAP 5 overrides material Courant

limidt in some volumes

- no-choking option should be selected downstream the valve

- heat transfer to the pipe walls must be considered for properly determination of

loads

- cold water (< 100*0

C loop seal cases, should be initialized with the loop seal water

distributed isenihalpycally in the first control volumes downstream of the Valve

(due to valve leakage prior to fast opening).

Figure 4.1. shows the nodalization diagram of the experimental facility for

RELAP 5/MOD3. The model has been built with TROPIC, the TRACTEBELS RELAP

Object-Oriented Preprocessing Interactive Code (ref. 6). Tank 1 was represented by a

"time dependent volume" for simulating upstream fluid conditions as a function of time.

The safety valve was modeled by a "servo valve" component with a linear area

opening characteristic. Piping network downstream the valve was modeled using "pipe" components for straight lenghts of pipe and "single volumes" components for

elbows. Dimensions and code options correspond to the RELAP 5/MOD1 model (ref. 4).

Tables 4.1. and 4.2. present the geometric data and component options for the upstream

and downstream piping parts respectively. Table 4.3. shows the heat structure data.

Two minor changes had to be done to the original RELAP 5/MOD1 model to avoid

program errors. Valve discharge junction originally taken as homogeneous (one

velocity) had to be turned into nonhomogeneous solution. Time dependent volume

representing the atmosphere was changed into a single volume modelization to avoid

an error related to heat transfer coefficient evaluation.

Code changes described in ref. 4 have not been included in RELAP 5/MOD3. Loads are

calculated making use of the control systems available within RELAP. The method for

load determination and its implementation are described in the next paragraph.

RELAP 51M0D3
TRACTEBEL

RELAPSMlOD2 HYDRO LOADS

CE LOOPS TEST 1 917

JANUARY/ 1999

*Load -

Segm~ent 1

~J-~ Ulvaren

029

i* Load - Segment 2

Legend

singl vol Load - ( 927 -

J ppeSegment 4r

Ih IDU .... Load -

-~ single Jun.Semn3

ZJ heat slab

valve ****... ...** .*****. .. ..

* 

.*. ....

Crosy~lTROPIC 1.0

Figure 4.1. TROPIC representation or RELAP nodalization
Table 4. 1.

UPSTREAM PIPING GEOMETRIC DATA (CROSBY TESTS)

Component Volume or

Number Junction Number

Component

Type

Lenght

(ft/rn)

Area

(ft2 /mr2)

Forward Loss

Coefficient

Reverse Loss Junction Flags or

Coefficient Volume Flags

Comments

001

002

003

004

005

V 1

J 1

V 1

J11

TMDP VOL

SNCLIUN

SNGLVOL

SNGLJUN

V 1-9 PIPE

2

3

4

5

6

7

8

J 1

V 1

20.0/6.096 25.0/2.3226

-- 0.2532/0.0235231

5.0/1-524 0.2532/0.0235231

0.1308/0.0121517

1.0/0.3048 0.1308/0.0121517

-- 0.1308/0.0121517

0.1308/0.0121517

-. 0.1308/0.0121517

-- 0.1308/0.0121517

-- 0.1308/0.0121517

-- 0.1308/0.0121517

-- 0.1308/0.0121517

0.1308/0.0121517

0.0204/0.0018952

1.0/0.3048 0.0204/0.0018952

0.04

0.0

0.0

0.195

0.0

0.195

0.0

0.195

0.0

0.0195

0.0

1.0

0.0

0.0

0.195

0.0

0.195

0.0

0.195

0.0

0.195

0.0

11

00000

01

00100

00

00000

00000

00000

00000

00000

00000

00000

00000

00100

10

Accumulator

Nozzle

Venturi

Reducer 8-in. x

6-in.,

Loop seal

piping

Valve in

Valve

006

007

SNGLJUJN

SNGLVOL

RELAP 5JM0D3
Table 4.2.

DOWNSTREAM PIPING GEOMETRIC DATA (CROSBY TESTS)

Component Volume or

Number Junction Number

Component

Type

Lenght

(ft/rn)

Area

(ft 2 /m2)

Forward Loss Reverse Loss Junction Flags or Comments

Coefficient Coefficient Volume Flags

008

009

010

Oil

012

013

014

015

016

017

)I

V-1-3

J 1-2

11

V 1-8

J 1-7

JIi

V I

J 1

V 1-12

il1-I1

JI

VI1

V 2

J1

ji

VALVE

PIPE

SNGLJUN

PIPE

SNGLJUN

SNGLVOL

SNGLJUN

PIPE

SNGLJUN

PIPE

SNGLJUN

-0.02D4/0.00189522

0.50/0.1524 0.2006/0.0186364

0.2006/0.0186364

-0.2006/0.0186364

0.50/0.1524 0.2006/0.0186364

-0.2006/0.0186364

O .200/0.0186364

0.50/00.1524 0.2006/0.0186364

-0.2006/0.0186364

0.50/0.1524 0.2006/0.0186364

-0.2006/0.01 86364

-0.2006/0.0186364

0.50/0.1524 0.2006/0.0186364

050/0.1524 0.7058/0.0655710

-0.2006/0.0186364

-0.7058/0.0655710

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.210

0.0

0.0

0.0

0.51235

0.0

0.210

0.0

0.0

0.0

0.51235

0,0

00100

10

01000

01000

00

01000

01000

00

01000

00

01000

01000

00

01000

01000

Servo-valve

Valve

Discharge

Elbow 1 in

Elbow 1 volume

Elbow l out

Expansion in

Expansion out 018

0

RELAP SIMOD3
Table 4.2. (Cont'd)

DOWNSTREAM PIPING GEOMETRIC DATA (CROSBY TESTS)

Compo~nent Volume or

Number junction Number

Component

Type

Lenght

(ft/rn)

Area

(ft2 /m2)

Forward Loss Reverse Loss

Coefficient Coefficient

Junction Flags or Comments

Volume Flags

019

020

021

022

023

024

025

026

V 1-30

J 1-29

J 1

V 1

J 1

V 1

V 2

V 3-42

V-43

V 44

J 1-25

J 26-28

J2943

jI1

V I

J1

PIPE 0-50/0.1524 0.7058/0.065571

- 0.7058/0.065571

SNGLJUN -0.7058/0.065571

SNGLVOL 0.70/0.21336 0.7058/0.065571

SNCLJUN - 0.7058/0.065571

PIPE 0.70/0.21336 0.7058/0.065571

1.00/0.3048 0.7058/0.065571

1.00/0.3048 0.7058/0.065571

1.00/0.3048 0.7058/0.065571

0.70/0.21336 0.7058/0.065571

* 0.7058/0.065571

- 0.7058/0.065571

- 0.7058/0.065571

SNGLJUN - 0.7058/0.065571

SNGLVOL 0.70/0.21336 0.7058/0.065571

SNCLJUN - 0.7058/0.065571

0.0

0.182

0.0

0.0

0.3192

0.0

0.182

0.0

0.0

0.182

0.0

0.0

0.3192

0.0

0.182

0.0

00

01000

01000

00

01000

00

00

00

00

00

01000

01000

01000

01000

00

01000

Elbow 2 in

Elbow 2 volume

Elbow 2 out

Valve SW-2

Elbow 3 in

Elbow 3 volume

Elbow 3 out

I-J

RELAP 5/MOD3

I .
Table 4.2. (Contd)

DOWNSTREAM PIPING GEOMETRIC DATA (CROSBY TESTS)

Componenit Volume or

Numiber Junction Number

Component

Type

027

028

029

V 1-2

V 3

j1-2

JIi

V I

PIPE

SNGLJUN

SNGLVOL

Lenght

(ft/rn)

0.50/0.1524

0.50/0.1524

10000.0

Area

(ft'2 fm2)

0.7058/0.065571

05592/0.0519514

0.7058/0.065571

05592/0.0519514

10000.0

Forward Loss

Coefficient

Reverse Loss Junction Flags or

Coefficient Volume Flags

00

00

Comments

0.0

0.0

0.0

0.0

01000

01100

11 Atmosphere

RELAP 51MOD3
Table 4.3.

DOWNSTREAM PIPING HEAT STRUCTURE (CROSBY TESTS)

H-eat

Structure

Numnber

Left Right

Boundary Boundary

Volume Volume

Volume

Lenght (ft/rn) Description

009

Valve outlet

flange

011

Pipe 1

Horizontal

013

Elbowi1

015

Pipe 2

Vertical

017

Expansion

019

Pipe 3

021

Elbow 2

Geometry Mesh Material Left Boundary

(ft/rn).

Carbon steel 0.2527/0.077023

Right Boundary

(ft/rn)

CYL 0.2760/0.084125

CYL

CYL

CmL

N/A

CmL

CmL

1.10

1-10

1-10

1-10

N/A

1-10

1-10

Carbon steel 0.2527/0.077023 0.2760/0.084125

Carbon steel

Carbon steel

N/A

0.2527/0.077023

0.2527/0.077023

N/A

0.2760/0.084125

0.2760/0.084125

N/A

0091

0111

0131

0151

N/A

0191

0211

0901-03

1101-08

*1301

1501-12

N/A

1901-30

2901

2901

2901

2901

N/A

2901

2901

0.50/0.1524

0.50/0.1524

0-50/0.1524

0.50/0.1524

N/A

0.50/0.1524

0.70/0.21336

Carbon steel 0.4740/0.144475 0.53129/0.161937

Carbon steel 0.4740/0.144475 053129/0.161937 2101

tA)

RELAP SWMD3
Table 4.3. (Cont'd)

DOWNSTREAM PIPING HEAT STRUCTURE (CROSBY TESTS)

Description Geometry Mesh Material Left Boundary Right Boundary

(ft/rn) (ft/rn)

Heat

Structure

Number

Left

Boundary

Volume

Right

Boundary

Volume

Volume

Lenght (ft/rn)

023

Pipe 3

Horizontal

CmL 1-10 Carbon steel 0.4740/0.144475 0-53129/0.161937 0231 2301

2302

2303-42

2343

2344

2501-01

2701-02

2901

2901

2901

2901

2901

0.70/0.21336

1.00/0.3048

1.00/0.3048

1.00/0.3048

0.70/0.21336

0.70/0.21336

0-50/0.1524

025

Elbow 3

027

Pipe 4

Vertical

CYL

CmL

1-10

1-10

Carbon steel 04740/0.144475 0.53129/0.161937

Carbon steel 04740/0.144475 0.53129/0.161937

0251

0271

2901

2901

t-.

RELAP S(MOD3
JPD/5N 17 1is

5. Mechanical loads determination

Two methods are commonly used for evaluating the mechanical loads on a piping

system : force balance and momentum balance (ref. 7). The force balance method equates

the resultant force transmidtted from the fluid to the structure as the sum of the pressure

and frictional forces acting on the wetted surface of the pipe. The momentum balance

method equates the force on the element to the time rate of change of fluid momentum

with~in the pipe. The former has the difficulty of calculating fluid friction forces on the

wetted surface. The latter has the- potential risk of numeric instabilities con-ing from

the time derivative nature of the method. This latter method has been used in this

analysis and no instabilities have been found.

Two kind of terms appear in the momentum balance method (ref. 8) : the wave or

acceleration force.

(where P and v stand for the density and velocity of the fluid in the pipe respectively

and the volumetric integral extends to the fluid control volume c, in the pipe).

And the blowdown force that appears only for open ended pipe segments.

FB =±A(P+Pv2) (5.2)

(where A is the area, P, P and v are the relative pressure, density and velocity of the

fluid at the open end respectively ; the positive sign is applied to inlets and the

negative one to outlets). The numerical discretisation of the wave force (eq. 5.1) yields

for segment K,

F,,k=-Ei-,Vi(CLgipgivgi+Caflpfivfi)] (5.3)

where the sumnation extends to all the nodes i of a bounded segment K of the pipe. The

phasic void fraction, density and velocity are represented by a1, P and v respectively.

The subindexes g and f refer to the gaseous and liquid phases. V stands for the node

volume. Figure 5.1. shows the implementation of that expression for a part of segment 2

with the aid of the TROPIC preprocessor. The Vi factor in expression 5.3 is included as

a multiplier in the adder control block. For the last segment in the test facility, which

is an open-ended segment, the total force is the sum of the wave force (eq. 5.1) and the

blowdown force (eq. 5.2) which can be computed as follows

FB~AoPo~ag~govi+afopfovJo) (5.4)

where the subindex o refers to the conditions at the discharge junction.

RELAP 5/MvOD3
wig eat-,,7 1i =Lc-i W:*::ILC Ill.. vac 9q. 19-29

Wolo 011-17No 019-1 Mopl IIIV si vowK 0 19-it"

ftw Cof*? TT IMF *M-s 7T 11w ea i.it 7T pM of-t, 

WIO 09-1 WSG0190

Up ac 019- -- T -

W-CK sit-it TIC TrACMI T cM1944T

AWi $19-21 7Tb I-I TM to"1 W 19tit"7

WfL? $li-il vici ale-i 410-2 iL Si-i $01

MCI[M. "togf etlK f WIS1011t"-K :9

ft"04 SIIIf 9fl TO *101 9-111 IT NO o$"1OR 11111T

M~ CIts." lVc~ Sit-f4M 1111 .

voto e-il IT "for Mi-16 f "I lw 1-

WI.? IIII-f pwI 910i 6 u $ .1?1ioi.

w eli-i,

WIN? 019-li OfI.? 919-311Up

Tr "" 0116-110OPICP1.0

Figure 5.1.. TROPIC modelization ot segmient loads
JPD/5N 17 1

16

6. Analysis and results

The RELAP 5/MOD3 code version has been received at TRACTEBEL recently. As it is

going to be the future tool for thermal hydraulic analysis, an assessment has been

conducted to prove the convenience of its application to the evaluation of discharge

piping hydrodynamidc loads. Different code options had been tested on this version to

check the range of the modifications and new models introduced in the MOD3 version.

EPRII CE test number 917 is used for ths assessment process.

6.1. Test 917 (Crosby hot water loop seal discharge)

Table 6.1. summarizes the different options that have been tested on RELAP 5/MOD3.

Table 6.2. compares the characteristic values of the loads on the segments and pressures

to test measurements and MODI. Figures 6.1. to 6.6. present the time evolution of those

variables for some significative cases compared to experimental data. The results are

commented in next paragraph.

6.1 .1. Results with the original MODI model (CASE 0)

Load peak values are close to the test measurements and RELAI' 5/MODI results (Table

6.2.). However, it can be observed from Figs 6.3. to 6.6. that RELAP 5/MOD3 loads are

clearly delayed with respect to the experiment, just the opposite of MODI results,

reflecting a lower slug velocity in MOD3 transient discharge evolution.

This is the consequence of a low coupling between phases (low interphase drag

coefficients, Fig. 6.7.) given by the last version of RELAP 5. On the contrary MODI

exhibited a high coupling between liquid and steam that is translated into a higher

slug velocity and hence an anticipation in the loads as compared to the experiment.

6.1.2. Results with bundle Interphase friction (CASES I and 8)

The liquid loop seal discharge is extremely dependent on the interfacial friction

between phases. RELAP S/ MOD3 allows for the possibility of choosing an alternative

interphase friction correlation that is applicable to bundle geometries. In order to test

the effect of this new correlation on the loads, two trials have been done : case 1 and

case 8 (Tables 6.1. and 6.2.). Case 1 was equivalent to base case 0 (piping is arranged

horizontally) and case 8 was similar to case 4 (segment 2 is considered vertical) but both

cases used the bundle interphase drag option. Comparison of case 1 to case 0 results and

case 8 versus case 4 shows no effect neither on the loads nor on the pressure. The

Bestion's interfacial friction correlation for rod bundles is only applied in bubbly /slug

flow regime. Such regimes are not developed in the discharge of a liquid loop seal and

the results must be unsensitive to this option.

6.1.3. Sensitivity to the horizontal stratification option at junctions (CASE 2)

Most of the flow regime during the loop seal discharge is annular-mist. Horizontal

stratification is initially present since an air-steam-liquid mixture is assumed filling

the pipe. Junction options were changed in this case (case 2 in Tables 6.1 and 6.2) to

account for a possible horizontal stratification downstream the valve. The results

show a negligible or null effect on the loads or pressure values. The very small amount

of liquid that is initially stratified and the fast development into annular-mist regime

are the reasons for that midnor effect.

RELAP 5/MOD3
icA? ricErTnp. MADPTO, SFAAJ. inAy. 11'L'

c6 F-~sr q i?. g6LAP5 MOD -3

35, 146. 6.1 . FeSS QR6 AT re

*PATA

-CA56: 0

30-- CA 5 a P

±CASG

*CA.SE /0

lt~

0J4 O

l0-

0.1 ol

Til?4E (see-)
ICAP M2ECTh'JG.MAPREPSP iN. flIy /q

l0

In

~5.

I

0-

Cis Trs7 q1lp. IE1AP-F~ WD-3

FI*6 6.2, .?FESSUIZ6 AT PT/o

-CASS. 0

-f--CA56 6

w -CASE 10

0.1 oz2 0.35

TiME (sec)
LCAP rMrE7-ip6, MApkip, SPAMV. MAY, ,'?qO

CE T67ST 1/7. R6UtP-5 ?1OP-3

241 FiG. G.3 LAD ON .566)16A~r I

CAC

0-

I-o

-21

T114E CSe-C)
1*

ICAFI&FiP16. MAV~iD, SPAN -N M'AY, 192

CC T657 117. ReZAV-6 NtOt-3

qo- FiG. 6.4. L-OAD ON .Su6mut~1ArZ

V ATA

-CASE 0

~CASE: 7-

-4-CASE 6

*CASE 10

o.;.3 036

77ME (.ec)
ISO

* DATA

-CASE 0

+CASE 6

50 -*CASE 10

l:zo

0.1

VnCf (Sec)
(2ao 9W.L

0

I9 36V) -4-

o 95v.7

1N A(q9-W579 NO' db'07 3 59 09!11

E-aIOH .9-dV7aZ *lb -~ls .90

Sb b I ' A vw 0NI d 9-' a 1IW1 9W.LL3aJq dl I.7

ofI
ANNULA2-t11T REcit

10 ~~ALL. OVE5R

Fi*6. 6:7. QuvNirY ANt? lhRTWRASE P1RA6 VISTPL~tfriVAIS IN 11OP3 M~AX CA515,O.2-w-)
Table 6.1 Summary of run sequence for RELAP -5/MOD -3, Test CE 917

BASE

PARAMETER SELECTION CASE 0 CASE I CASE 2 CASE 6 CASE 7 CASE 4 CASE 8 CASE 9 CASE 10 RECOMiMENDED OPTION

Interphase friction model pipe (b=O) bundie(b=l) pipe pipe pipe pipe bundle pipe pipe Pipe interphase friction

Horizontal Strati!, In Jun. off (v=0) Ioff on (v--3) off off off off off off No horizontal stratification

Expansion -Contraction K(K fAbrupt area KiK fK fLocal pr~ess losses

Heat slab mnodeling yes yes yes yes no so to no yes No beat slab modeling

Vertical orientation of seg. 2 no 11) to no no yes yes yes 110 Apply appropiate orientation

Choking model dlownstreamn "D no to 10 no re no yes no No choking option

downstream

Phase velocity option 2 (h=0) 2 2 2 2 2 12 12 1 1(h=2) Two velocity solution

I-.

RELAP 1M003
Table 6.2 Comparison of RELAP 5/MOD 3 results from parametric studies and experiment for test CE 917

RELAP5/

TEST MOD] CASE 0 CASE I CASE 2 CASE 6 CASE 7 CASE 4 CASE 8 CASE 10

LOAD (W)I max* - 8.3 8.3 8.3 8.3 8.4 8.1 8.1 7.2

ON SEGMENTI1 MAX 18.4 10.5 21.2 21.2 21.2 20.4 21.2 20.7 20.7 19.7 MIN -19.8 -11.3 -23.0 -23.0 -23.0 -16.0 -33.1 -32.4 .32.4 -23.6

LOAD MkN) MAX 50.8 56.8 40.3 40.3 40.3 65.0 40.4 45.8 45.8 45.6 ON SEGMENT 2 MIN -59.8 -65.3 -87.3 .87.3 -89.3 .205.3 -101.4 -66.0 -66.0 -41.2

LOAD (WN) MAX 78.3 123.3 96.3 96.3 98.7 191.4 110.9 77.1 77.1 90.3

ON SEGMENT 3 min -31.6 -42.1 -20.1 -20.1 -20.3 -25.8 -21.4 -

MIN -74.3 -47.5 -55.2 -55.2 -55.0 -46.7 -52.2 -43.9 -43.9 -48.7

LOAD MkN) MAX 64.8 70.9 96.2 %.2 95.9 86.7 95.2 78.9 78.9 95.2 ON SEGMENT 4

PRESSURE (bar) MAX 34.3 28.8 24.9 24.9 24.9 24.9 24.9 25.0 25.0 25.6

ATFTO09 STEADY 16.3 17.0 15.9 15.9 15.8 15.9 15.9 16.8 16.8 16.4

PRESSURE (bar) MAX 7.7 6.9 6.6 6.6 6.6 6.2 6.8 6.5 6.5 8.0 AT PT' 101

' Values in the table are given for characteristic points in the figures: maximum (MAX), minimum (MIN), local minimum and maximumn (min and max), and steady state (t = 0.3 sec).

CD.

REALP 5/M003
JPD/bJ1 7 119

6.1.4. Sensitivity to the abrupt area change model at expansion (CASE 6)

It was proven for MOD2 that using the abrupt area change model at the expansion in

segment 2 instead of a local pressure loss coefficient contributed to reduce induced loads.

The results are just the opposite for MOD3 (see Table 6.2, case 6). The negative load in'

segment 2 and the positive load in segment 3 are doubled when using the abrupt area

change. The explanation for the contradiction is that in MOD2 the important variable

driving the load was the mass profile and in MOD3 (with a smoother slug mass

distribution) the relevant parameter is the slug velocity. The abrupt area change

model results in a lower pressure loss for the liquid phase than in the base case where a

local form loss coefficient is applied. As the liquid is not slowed down when the slug

goes through the expansion, the effect of front densification in MOD2 is not enhanced

and loads are lower. MOD3 does not produce sharp fronts and a lower pressure loss at

expansion makes slug velocity larger and induced loads have higher values.

6.1 .s. Effect of heat slab modeling (CASE 7)

It has been shown that heat transfer to pipe walls had an striking effect on RELAP 5/

MOD2 computed loads. The sensitivity analysis has been repeated on RELAP 5/

MOD3. The results are presented in Table 6.2 under the header case 7 ( to be compared

to base case 0). Except for the loads on segment 1 that exhibit a very oscillatory

pattern, all load and pressure values are quite similar to the case with heat transfer to

the cold pipe walls (case 0). The same low influence was observed for MODI results

(Tractebel results for MOD] differ from ITI ones in heat slab modeling). Comparing

condensation rates for MOD2 and MOD3 it has been found that MOD2 produced 10 times

more condensation than MOD3. Because of this the influence of heat slab modeling in

MOD2 was so important, while being negligible for MOD3.

6.1 .6. Effect of vertical orientation of segment 2 (CASE 4)

The original MOD] input model assumed there was no change in the elevation for the

discharge pipes, i.e., an horizontal arrangement was considered for the input model. It

has been already pointed out that the dominant flow regime is annular-mist. There are

no different correlations for the interphase drag coefficient on vertical and horizontal

pipes. Any possible difference when verticality is imposed should be attributed to

body force effect on the slug and/or changes in the onset of annular-m-ist conditions.

Table 6.2 shows the results under the case 4 header. Positive load on segment 2

increases and negative one is reduced, getting closer to the experimental measurements.

The other loads are also closer to the experiment (except load on segment]1 because of its

oscillatory behaviour).

Case 4 includes all the recommended options for the application of RELAP 5/MOD3 to

the calculation of hydrodynamidc loads. Figures 6.8 to 6.14 compare the pressure and

load results to the experimental measurements and the MOD] computations (ITI results

are the EPRI validation for MOD] and TIhA results are the TRACTEBEL check for

MOD]). Some oscillations can be observed in the load for segment]1 as a result of the

new choking model for MOD3 (Fig. 6.14).

RELAP 5/MOD3
RELAP5/MOD3/V5M5 23/07/90

CE TEST NO.917. CASE 4

SDATA

*)( RELAPS/MOD1 ITI

-- RELAPS/movi TRA

R ELAP5/MOD3 FIG 6.8 PRESSURE AT PT09 PRESSURE (PA)

3.e+06

2.5e+06-

2.e+06-

1.50+06

5.0+05-

0- . 9 1 . . I . . . . . 1.1 . I I a I I . I I . v . I . . I

0.00 0.05 0.10 0.15

TIME (SEC)

0.20 0.25 0.30 0.35
RELAP5/MOD3/V5M5 23/07/90

CE TEST NO.917. CASE 4

SDATA

* IELAIPS/MOD1 ITI

-A IELAP5/MOD1 RA

P2RESSUIM (PA) FIG 6.9 PRESSURE AT PT102

0.00 0.05 0.1.0 0.15 0.20 0.25 0.30

TIME (SEC)

0.35
RELAP5/MOD3/V5M5 23/07/ 90

CE TEST NO.917. CASE 4

- -DATA

* 4 ELAP5/MODI ITI

-A TELAP5IMOD1 TRA

R 1X"A5/MOD3

TRoiCE (N) FIG 6.10 LOAD ON SEGMENT 1

20000-

15000-

10000

5000-

0,

-5000-

-10000-

-15000

-20000-

-25000-

-30000-

0.00

I

0.05 0.10 0.15 0.20 0.25 0.30 0.35

TIME (SEC)
FORCE (N)

RELAP5/MOD3/v5M5 23/07/90

CE TEST NO.917. CASE 4

E3 DATA

- $.RELAP5/k4ODl ITI

-A-ELxAPS/uo140 TRX

1ELAP5/moD3 R 

FIG 6.11 LOAD ON SEGMENT 2

0.5 .1 0150200.5 13 03

0.00

TIME (SEC)
RELAP5/MOD3/V5M5 23/07/90

CE TEST NO.917,. CASE 4

E3 DATA

* $-IELRP5/MOD1 ITT

-A IELAP5/moD1 TPA

- R- rXAP5/MOD3

FIG 6.12 LOAD ON SEGMENT 3 roi~zz (N)

1.2e+05

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0 .35

TIME (SEC)
IRELAP5/MOD3/V5M5 23/07/90

CE TEST NO.917. CASE 4

Ea DATA

- W4- RELAPS/HOD1 ITI

-A*- IRELAP5/MOD2. TRA

-,V--. RELAP5/HOD3

ToRCE (H) FIG 6.13 LOAD ON SEGMENT 4

70000

60000

50000

40000

30000

20000

10000

0

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

TIME (SEC)
MASS FLOW (Kc/SEC)

RELAP5/MOD3/V5m5 23/07/90

CE TEST NO.917. CASE 4

P~TZXaP5/MOD3

FIG 6.14 VALVE MASS FLOW

n o~ r, i0 101 0 .20 0.25 0.30 0.35 n nnl

TIME (SEC)
JPD,'bJI 7 220

6.1 .7. Results of a fully choked solution downstream the valve (CASE 9)

Some changes have been introduced in MOD3 for the choking model (ref. 10). The

improvements consisted on smoothing the transition from the subcooled to the twophase choking model and elimination of a coding error. Although it is still

recommended not to use the choking model in succesive junctions, a trial was made to

study the slug evolution using the choking model at all junctions downstream the valve,

as it was tried for MOD2. As a result, the liquid slug remained still in the first volumes

downstream until t= 0.2, when the code failed. Recommendation of not using the

choking option downstream the valve is mnade again.

6.1.8. One velocity solution In RELAP 5/MVOD3 (CASE 10)

One-velocity analysis has been repeated with MOD 3 as it was done with MOD2 to

assess the effect of interphase drag coefficients. Results are presented in Table 6.2

referred to as case 10. Although it is not shown in that table, the load peak tim-ing is

quite similar to the RELAP 5/MOD1 results proving that MODI solution was very close

to one speed calculation. However the peak values are not equivalent, the differences

arising from a different valve discharge due to the changes in the choking model in

RELAP 5/MOD3.

RELAP 51M0D3
JPD/5N1 7 21

7. Run statistics

The simulation has been performed on a computer APOLLO 10020 running with a UNIX

operating system.

The requested time step for the whole calculation was 0.0002 sec yielding 1803

attempted advances (14 repeated) for the transient time of 0.35 sec (run statistics are

taken from case 4).

The time step history as a function of the transient time is presented in Fig. 7.1 as well

as the Courant time step. Figure 7.2 shows the CPU time performance.

The code performance PF = (1000OCPU)/(N*DT) is (1000*463)/(118*1789)=

2.19 ms/step/volume.

In case 4 heat transfer to the pipe walls is not accounted for.

RELAP 5/MOD3
RELAP5 /MOD3 /V5m52/7/9 23/07/90

CE TEST NO.917. CASE 4

FIG 7.1 ACTUAL AND COURANT TIME STEPS

0.0012

0.001

0.0008

0. 0006

0. 0004

0.0002'

0.

0.00 0.05 0.10 0.15 0.20 0.25 0.30

TIME (SEC)

0.35
RELAP5/MOD3/V5m5 23/07/!

CE TEST NO.917. CASE 4

FIG 7.2 CPU TIME ON APOLLO 10020

90

T

I

H

S

E:

C

450-

400-

3.50

300-

250-

200-

150-

100-

50-

0.00 0.05

- PUTIMF:

0.10 0.15 0.20 0.25 0.30 0.35

TIME (SEC)
-JPD).51J 17 2

22

8. Conclusions

RELAP 5/MOD] was validated by EPRI for the calculation of safety and relief value

discharge piping hydrodynamic loads (ref. 4). Modelization guidelines were issued for

a proper code application to this kind of calculations and are summarized as follows:

- control volumes must have a length between 0.15 and 0.3 m for a correct slug and

pressure fronts tracking.

- time step must be limited externally to the material Courant limit U~ 0.2 m sec)

- the no-chocking option must be imposed to all the junctions downstream the test

valve

- heat transfer to pipe walls must be included; ten radial nodes suffice to yield a

solution not dependent on noding detail

- cold water loop seals (< 100*0

C should be located initially downstream the test

valve.

The suitability of some of these guidelines has been checked for RELAP 5/MOD3/5M5.

One additional guideline has been found suitable for R.ELAP 5/MOD3 calculations.

- pipe orientation (horizontal or vertical) should be taken into account for pipes

downstream the valve.

The main conclusions that have been reached during the assessment process are the

folowing.

I1. For liquid loop seal discharges the effect of heat transfer to pipe heat structures

need not be modeled for a correct evaluation of liquid discharge loads. The same

conclusion was obtained for REALP S/ MOD1.

2. RELAP 5/MOD3 underestimates the coupling between the liquid and vapour phases

producing a lower liquid slug velocity than in the experiments. Although maximum

values for the loads are quite comparable to the measurements, the loads are

delayed in time.

3. The changes that have been introduced to the choking model in RELAP 5/MOD3

(inclusion of a transition zone between the subccoled and two phase flow regimes)

produces a characteristic two-bump valve flow discharge that is reflected on the

loads of the downstream piping.

4. From this assessment study, one can recommnend to use the following options using

RELAP 5/MOD3:

a . control volumes must have between 0.15 and 0.3 m for a correct slug and pressure

fronts tracking.

b. time step must be limited externally to the material Courant limit U~ 0.2 m sec).

c. the no-chocking option must be imposed to all the junctions downstream the test

valve.

d. heat transfer to pipe walls is not requiered to be included for water loop seal

discharges.

RELAP 51M0D3
JPDI5N17 2

23

e. cold water loop seals (< 100* C) should be located initially downstream the test

valve.

The suitability of some of these guidelines has been checked for RELAP 5/MOD3.

Some additional guidelines have been found suitable for RELAP 5/MOD3

calculations.

f. pipe orientation (horizontal or vertical) should be taken into account for pipes

downstream the valve.

g. valve junction is modeled with the 2 velocity option.

5. Comparing the RELAX' 5/MOD3 results for case 4, which corresponds to the

recommended options above, and the experimental data (Table 6.2) it is observed

that

a . The positive forces agree with the measured forces and a margin of 10 % covers

all experimental points.

b. The calculated negative forces all exceed the measured forces except for segment

3, where the measured results exceed the calculated values by 80 %. However,

the large negative measured value is probably due to the lower stiffness of the

supports for this segment (ref. 11) and the same discrepancy was found for

RELAX' 5/MODI and ignored for its qualification. Hence, it is proposed to

consider the RELAX' 5/MOD3 results acceptable, with a suitable margin to bring

the data in line with the RELAX'5/MODI results, and to estimate the negative

forces on all segments.

RELAP 51MOD3
JPD'5r17 24

9. References

1. USNRC "TM! - 2 Lessons Learned Task Force Status Report and Short Term

Recommendation", NUREG 0578, July, 1979.

2. "EPRI/C-E PWR Safety Valve Test Report", EPRI NP-2770-LD, January 1983

3. "Application of SOLA -NEt for Safety and Relief Valve Inlet and Discharge Piping

Analysis", EPRI NP-2585-LD, September 1982.

4. "Application of RELAP-5/MOD-1 for Calculation of Safety and Relief Valve

Discharge Piping Hydrodynamic Loads", EPRI NP-2479-LD, July 1982.

5. V.H. Ransom, et al., -RELAP-5/MOD-2 Code Manual", NUREG/CR-4312, EG & G

Idaho, March 1987.

6. F. Bastenaire, et al., *TROPIC User's Manual", TRACTEBEL, draft version,

January,1990.

7. J.G. Arcndts and A.G. Ware, "Piping System Response Induced by Thermalhydraulic

Transient :A review of Recent Analysis Methods and Experiments", Nuclear

Engineering and Design 90 (1985), 271-277, Nort-Holland, Amsterdam.

8. R.K. House, et al. "Calculation of Safety Valve Discharge Piping Hydrodynamic

Loads Using RELAP-5/MOD-1" ASME 83-NE-IS.

9. R.A. Riemke, "Report on CCFL and Interphase Drag Models for RELAP-5/MOD3",

EGG-TFM-8012, EG & G idaho, February 1988.

10. W.L. Weaver, "Improvements to the RELAP-5/MOD-3 Choking Model", EGG-EST8822, EG & G Idaho, December 1989

11. L.C. Smith and T.M. Adams, "Comparison and Evaluation of Anatycal Structural

Solutions with EPRI Safety Valve Test Results", journal of Pressure Vessel

Technology, Vol. 107, 380-386, Nov. 1985.

RELAP 51M0D3
;RC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION I. REPORT NUMBER

1.89) IAseignea tr NRIC. Add Vol.. S.,po.. Rev..

ACM 1102. V4Addsnaw, Nuvmbn. If emy.1

201. 3202 BIBLIOGRAPHIC DATA SHEET

ISto instructions on the fvyefuI NUREG/IA-0093

*TITLE AND SUBTITLE ICAP00159

RELAP5IMOD3 Assessment for Calculation of Safety and 3. D ATE REPORT PUBLISHED

Relief Valve Discharge Piping Hydrodynamic Loads FebNTruaryA February 1994

4. FIN OR GRANT NUMBER

______________________________________________________ L2245

* AUTHORIS) 6. TYPE OF REPORT

E. J. Stubbe, L. VanHoenacker, and R. Otero Techni1cal Report

7. PERIOD COVERED Iiu-ai.ov Dormi

*PER FORMING ORGANIZATION - NAME AND ADDRESS (If NRC. prvit Division. OlfictorAeispln. U.S1 Nucafi##W Rplrory Cearmwuae. and mwiling eddewv.if conhractor. provide

now sag nfeiMkV addmwa&I

TRACTEBEL Avenue Ariane 7

B-1200 Brussels, Belgium

SPONSORING ORGANIZATION - NAME AND ADDR ESS 1IiiNRC. svoe -S jjgw,***if ove" re.Drv NRC Dikvtso. Officeafw Meg V10 Au.S. id.. Raeulitoiy COMMInion.

owE melileg a" ees1

O~ffice of Nuclear Regulatory Research

11.5. Nuclear Regulatory Commission

Washington, DC 20555

3. SUPPLEMENTARY NOTES

1. ABSTRACT 10 oiro'seieinsom

Mbs report presents an assessment study for the use of the code RELAP5/MOD3/5M5 in the calculation of transient

-iydrodynamic loads on safety and relief discharge pipes. Its predecessor, RELAP5/MOD1, was found adequate for

Mis kind of calculation by EPRI. The hydrodynamic loads are very important for the discharge piping design

x)cause of the fast opening of the valves and the presence of liquid in the upstream loop seals.

rhe code results are compared to experimental load measurements performed at the Combustion Engineering

Laboratory in Windsor (U.S.A.). Those measurements were part of the PWR Valve Test Program undertaken by

EPRI after the TMI-2 accident.

Ths particular kind of transients challenges the applicability of the following code models

-Two-phase choked discharge

-Interphase drag in conditions with large density gradients

-Heat transfer to metallic structures in fast changing conditions

-Two-phase flow at abrupt expansions.

2. KEY WORDSIDESCRIPTORS (air watch oppA~rew 54.1se wil aut "mom""l A ioengJCR Ithe "Port-) 13. AVAILABILITY STATEMENT

ICAP PogramUnlimited RELAP Program 14. SIcuAITY CLASSIFICATION

HyrodyA5Mic oad IrA!, peg. Hydrdynaic LadsUnclassified

Unclassified

15. NUMBER OF PAGES

16. PRICE

ARC FORM 33S 12491


Federal Recycling Program
JPD/5N1 7

10. Attachment : microfilm (CASE 4)

momj~ 6aiifa-4 -s '"L

ISBN 0-16-043119-0

90000

9 780160 431197 RELAP 5/M003