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Solution of IAEA International Collaborative Standard Problem on Integral PWR “Open Calculation” using KORSAR/GP Code

Yu.Sorokin, N.Fil, N.Bukin

Forth Technical Meeting/Workshop for the ICPS

on Integral Water Cooled Reactor Design,

Pisa 25-28 February 2013

2

ICSP Open Calculation Stage

Main Purposes:

- Comparison of the Blind & Open Calculation’s

results with the experimental data for SP-2 and SP-3

tests.

- Lessons learned during ICSP solution.

3

KORSAR/GP Code

Russian Thermal Hydraulic KORSAR/GP Code was

used for Blind and Open Calculations of MASLWR

parameters behavior during the SP-2 and SP-3

experiments.

KORSAR/GP is the Best Estimate Code and it is

intended for analyses of LWR processes in steady-state,

transient and accident conditions.

Modelling of Thermal Hydraulic processes in KORSAR/GP is carried out on the basis of completely nonequilibrium two-liquid model (three conservation equations for water and steam phases) in one-dimensional approach.

4 4

Two-Fluid Model Equation

System

g,mggg

ggRAW

zA

1

g,egggggg

gggR

z

PW

PAWh

zA

1h

Phase energy conservation equation

Phase mass conservation equation

Phase movement conservation equation

gmom,g

g

ggg

g

gg Rz

P

z

WW

W

ρ

τρ f,momR

z

P

f

f

fff

f

ffz

WW

Wρ

τρ

Phase state equation ggg h,P fff h,P

ff AWρzA

1fff

f,mR

fff h AWhzA

1ffffρ

Pf

z

PWff

f,eR

5

Specific Phisical Phenomena:

- non-condensable gases,

- choked flow,

- “flooding” of water and water steam counter flows;

- heat transfer crisis with boiling in coolant and steam-

generating channels;

- re-flooding;

- two-phase flow stratification in vertical channels;

- radiant heat transfer.

KORSAR/GP Code

6

Functional Content Structure

SPECIAL PROGRAM MODULES

UNIT OF CIRCUIT THERMAL

HYDRAULICS

CONSTITUTIVE

RELATIONS WATER AND

STEAM PROPERTIES

AUXILIARY

PROGRAM UNIT

7

Composition of Special Modules

Centrifugal

pump

Water steam

vessel under

pressure

Accumu-

lator

Tank with

free level Gate valves

Valves

Controls

Reactor

neutron

kinetics

Heat-

conducting

structures

8

F

Fcr2

Fcr2

1

Diagram of the conditions of Diagram of the conditions of

heat exchange with the wallheat exchange with the wall

Diagram of fDiagram of flowlow conditions conditions inin

horizontal pipeshorizontal pipes

Film

condensation

4

Film boiling

6

Pre-crisis boiling

2

Heat convection

to liquid

3

Transient boiling

260

345 450

340

256

Tmin

Tcr

TS

Steam volume fraction0 1

Wa

ll t

emp

era

ture Dispersed conditions

5

250

560

TS - 2

Bubble Slug

Dis

per

sed

Annulardispersed

Stratified

StB B-St SB ADS SAD1

D2

D

F

Fcr2

Fcr2

Diagram of the conditions of Diagram of the conditions of

heat exchange with the wallheat exchange with the wall

Diagram of fDiagram of flowlow conditions conditions inin

horizontal pipeshorizontal pipes

Film

condensation

4

Film boiling

6

Pre-crisis boiling

2

Heat convection

to liquid

3

Transient boiling

260

345 450

340

256

Tmin

Tcr

TS


Wa

ll t

emp

era


5

250

560

TS - 2 Film

condensation

4

Film boiling

6

Pre-crisis boiling

2

Heat convection

to liquid

3

Transient boiling

260

345 450

340

256

Tmin

Tcr

TS


Wa

ll t

emp

era


5

250

560

TS - 2

Bubble Slug

Dis

per

sed

Annulardispersed

Stratified

StB B-St SB ADS SAD1

D2

D

F

Fcr2

Fcr2

KORSAR Closing Relations

The skeleton tables are used for calculating of critical heat flux

9

The main modeling assumptions used for Blind

Calculation as follows.

All core heaters are lumped together.

All SG coil tubes are lumped together.

Three helical SG coils are modeled as single pipe

volume with the flow and heat transfer areas kept the

same.

Two parallel channels, connected with each other,

were used for HPC modelling.

System Idealization for Blind Calculation 1/2

10

Each pair of ADS lines is modeled as single equivalent

channel.

Choked flow model is implied at all valves on vent lines.

PRZ heaters, HPC heaters, feed water lines are not

modeled.

A surface roughness of 1.0x10-6m was used for all

MASLWR components.

System Idealization for Blind Calculation 2/2

11

Input Data Preparing

The KORSAR Input Data has been prepared on the base of

information found in Problem Specification and it is similar

to the RELAP Data described in OSU-MASLWR-08002

(Draft). 1 Problem Specification for the IAEA International Collaborative

Standard Problem on Integral PWR Design Natural Circulation

Flow Stability and Thermo-hydraulic Coupling of Containment and

Primary System during Accidents. Draft.

2 Analysis of RELAP5-3D Modeling Techniques for Natural

Circulation Small Integral Light Water Reactors,

Draft. OSU-MASLWR-08002.

12

The KORSAR Nodalization Diagram of the MASLWR Test Facility

Val800

bljun1

Val107

Ch107

Ch108

Val108

Val103

Ch103

Val106

Ch106

Ch210

Val30

Ch30

smass_t1

bvol_t3

HC

S3

Ch2-01

Ch2-02

Ch2-03

Ch2-04

Ch2-05

Ch2-06

Ch2-07

Ch2-08

Ch2-09

Ch2-10

Ch2-11

Ch2-12

Ch2-13

Ch2-14

Ch2-15

Ch2-16

Ch2-17

Ch2-18

Ch1-18

Ch1-17

Ch1-16

Ch1-15

Ch1-14

Ch1-13

Ch1-12

Ch1-11

Ch1-10

Ch1-09

Ch1-08

Ch1-07

Ch1-06

Ch1-05

Ch1-04

Ch1-03

Ch1-02

Ch1-01

HC

S1

Ch100

Ch3

Ch1

0

Ch20

Col30

HCS40

HC

S2

HC

S4

bvol_t1

bvol_t2

Ch300-20

Ch300-19

Ch300-18

Ch300-17

Ch300-16

Ch300-15

Ch300-14

Ch300-13

Ch300-12

Ch300-11

Ch300-10

Ch300-09

Ch300-08

Ch300-07

Ch300-06

Ch300-05

Ch300-04

Ch300-03

Ch300-02

Ch300-01

Ch200-20

Ch200-19

Ch200-18

Ch200-17

Ch200-16

Ch200-15

Ch200-14

Ch200-13

Ch200-12

Ch200-11

Ch200-10

Ch200-09

Ch200-08

Ch200-07

Ch200-06

Ch200-05

Ch200-04

Ch200-03

Ch200-02

Ch200-01

HC

S300

Ch200-21Ch300-21

Ch300-22 Ch200-22

HC

S201

HC

S200

HCS106

Val501

Ch40

HCS25

Ch400-18

Ch400-17

Ch400-16

Ch400-15

Ch400-14

Ch400-13

Ch400-12

Ch400-11

Ch400-10

Ch400-09

Ch400-08

Ch400-07

Ch400-06

Ch400-05

Ch400-04

Ch400-03

Ch400-02

Ch400-01

Ch500-18

Ch500-17

Ch500-16

Ch500-15

Ch500-14

Ch500-13

Ch500-12

Ch500-11

Ch500-10

Ch500-09

Ch500-08

Ch500-07

Ch500-06

Ch500-05

Ch500-04

Ch500-03

Ch500-02

Ch500-01

bvol_t3bvol_t3

HCS30

13

Elements of the KORSAR nodalization scheme

KORSAR

Component

KORSAR

Component Type

MASLWR Region

Ch100, Ch1, Ch2,

Ch3, Ch30

Channel

Primary System

Ch10, Ch20, Ch40 Channel Secondary System

Ch200, Ch300 Channel High Pressure

Containment

Ch400, CH500 * Channel Containment Pool

Ch106, Ch107,

Ch108

Channel ADS Lines

VAL106, VAL107,

VAL108

Valve ADS Valves

14


KORSAR

Component

KORSAR

Component Type

MASLWR Region

HCS1 Heat structure Core Heater Rods

HCS4,

HCS3, HCS22,

HCS25

Heat structure RPV Wall

RPV Features

HCS10 Heat structure SG tubes

HCS20, HCS23,

HCS24

Heat structure Steam Drum

HCS40 Heat structure Steam Line Wall

HCS200, HCS201 Heat structure HPC Wall

15


KORSAR

Component

KORSAR

Component Type

MASLWR Region

HCS106 Heat structure Vent line (PCS106)

Wall

HCS300 Heat structure Heat Transfer Plate

HCS30 * Heat structure Pressurizer Heaters

bvol_t1, bvol_t2,

bvol_t3

boundary cell

bljun_1 impenetrable

connection

16

After the analysis of the SP-2 and SP-3 experimental data the

following changes were made for Nodalization scheme used

for Open Calculation.

The steam line pressure (PT602) is used as the secondary side

boundary condition for transient.

Two vertical channels located inside the HPC model the

thermal heat boundary layer (Ch300) near the heat transfer

plate and other HPC volume (Ch200).

Ch300 cross section area is significantly less than Ch200 one.

Modelling Change for Open Calculation

17

Two channels located inside the cooling pool vessel model the

thermal heat boundary layer near the heat transfer plate

(Ch400) and other CPV volume (Ch500).

The elements of the channels Ch400 and Ch500 are

connected by the junctions.

Ch400 cross section area is significantly less than Ch500 one.

Heat transfer plate is modeled as two dimensional heat

structure.

The pressurizer heaters and additional heat losses are

modeled for SP-3 Open Calculation.


18

Ch500

Ch

40

0

Ch200

Ch

30

0 Ch400

Ch

30

0

Ch

20

0

HPC HPC CPV

CPV


Blind

Calculation

Open

Calculation

19

SP-2 Control Logic 1/2

Control logic was realized in conformance to 1.SP_2_and

SP_3_Prosedures (OSU-MASLWR-10005-R1, App. C).

SP-2

The core power and feed water flow rate are equal to initial

values if time less than steady-time.

If time is equal to steady-time or grater it the feed water

flow to SG is stopped, RPV pressure boundary condition

(for ch3) is changed on impenetrable connection.

After the time when PZR pressure (PT-301) reaches

9.063 MPa, power change is set by the tables from

3. ICSP_SP2_CorePower.xls.

20

SP-2 Control Logic 2/2

At this time the valve PCS106a is

opening, farther opening/closing are

in accordance with fallowing

conditions:

- HPC pressure <1.479 MPa - the

valve PCS106a is opened;

- HPC pressure > 1.7236 MPa - the

valve PCS106a is closed.

HPC vent valve SV-800 is closed too.

When the difference between RPV

pressure and HPC pressure (PT-301

minus PT-801) is 0.034 MPa the

valves on vent lines (PCS-106A, PCS-

106B) and on sump return lines

(PCS-108A, PCS-108B) are opened.

Val800

bljun1

Val107

Ch107

Ch108

Val108

Val103

Ch103

Val106

Ch106

Ch210

Val30

Ch30

smass_t1

bvol_t3

HC

S3

Ch2-01

Ch2-02

Ch2-03

Ch2-04

Ch2-05

Ch2-06

Ch2-07

Ch2-08

Ch2-09

Ch2-10

Ch2-11

Ch2-12

Ch2-13

Ch2-14

Ch2-15

Ch2-16

Ch2-17

Ch2-18

Ch1-18

Ch1-17

Ch1-16

Ch1-15

Ch1-14

Ch1-13

Ch1-12

Ch1-11

Ch1-10

Ch1-09

Ch1-08

Ch1-07

Ch1-06

Ch1-05

Ch1-04

Ch1-03

Ch1-02

Ch1-01

HC

S1

Ch100

Ch3

Ch10

Ch20

Col30

HCS40

HC

S2

HC

S4

bvol_t1

bvol_t2

Ch400-18

Ch400-17

Ch400-16

Ch400-15

Ch400-14

Ch400-13

Ch400-12

Ch400-11

Ch400-10

Ch400-09

Ch400-08

Ch400-07

Ch400-06

Ch400-05

Ch400-04

Ch400-03

Ch400-02

Ch400-01

Ch300-20

Ch300-19

Ch300-18

Ch300-17

Ch300-16

Ch300-15

Ch300-14

Ch300-13

Ch300-12

Ch300-11

Ch300-10

Ch300-09

Ch300-08

Ch300-07

Ch300-06

Ch300-05

Ch300-04

Ch300-03

Ch300-02

Ch300-01

Ch200-20

Ch200-19

Ch200-18

Ch200-17

Ch200-16

Ch200-15

Ch200-14

Ch200-13

Ch200-12

Ch200-11

Ch200-10

Ch200-09

Ch200-08

Ch200-07

Ch200-06

Ch200-05

Ch200-04

Ch200-03

Ch200-02

Ch200-01

HC

S300

Ch200-21Ch300-21

Ch300-22 Ch200-22

HC

S201

HC

S200

HCS106

Val501

Ch40

HCS25

21

Steady-State Comparison for Test SP-2 1/2 Parameter MASLWR Unit Experimental

Value

Steady-State Value

from Code

Pressurizer pressure PT-301 MPa(a) 8.719 8.718

Pressurizer level LDP-301 m 0.3607 0.3615

Power to core heater rods KW-101/102 kW 297.33

(149.39+147.94)

297.0

Feedwater temperature TF-501 ºC 21.39 21.39

Steam temperature FVM-602-T ºC 205.38 199.3

Steam pressure FVM-602-P MPa(a) 1.428 1.482

Ambient air temperature ºC 25.00

HPC pressure PT-801 MPa(a) 0.1255 0.1287

HPC water temperature TF-811 ºC 26.6 26.87

HPC water level LDP-801 m 2.8204 2.8005

Primary flow at core

outlet

FDP-131 kg/s 1.82 1.768

Primary coolant

temperature at core inlet

TF- 121/122/

123/124

ºC 215.34/214.82

214.42/215.11

218.75

Primary coolant

temperature at core outlet

TF-106 ºC 251.52 253.32

22

Steady-State Comparison for Test SP-2 2/2 Parameter MASLWR Unit Experimental

Value

Steady-State Value from

Code

Feedwater flow FMM-501 kg/s 0.106 0.108

Steam flow FVM-602-M kg/s 0.10207

Primary coolant

subcooling at core outlet

ºC 47.70

Total heat loss through

primary system

kW 2.38

Heat transfer through SG kW 290.02

Maximum surface

temperature of core

heater rods

ºC 301.8

Location from the SG

secondary inlet to reach

- saturation

- superheat

m 2.00

5.70

23

SP-2 Time Sequence of Events

Event Time (s)

Experiment Blind Open

Start of simulation – steady state from -1000.0 to 0.0

Stop MFP

Close HPC vent valve SV-800 0.0

0.0 0.0

PZR pressure (PT-301) reaches 9.064 MPa(a) (1300psig)

Enter decay power mode 18.0 17.0 35.0

De-energize PZR heaters

Open ADS vent valve (PCS-106A) 48.0 53.0 47.0

Record opening and closing times for PCS-106A See Table

Record opening and closing times for SV-800 No opening

Start long-term cooling when pressure difference

between primary system and HPC (PT-301 minus PT-

801) becomes less than 5 psi (0.034 MPa)

Open and remain open of PCS-106A and PCS-106B

Open and remain open of PCS-108A and PCS-108B

4024.0 4143.0 4250.0

End of test when one of the following conditions is

reached: PZR pressure (PT-301) ≤ 0.61 MPa(a) (75 psig) 15820. 14000. 14800.

24

SP-2 PCS-106A Operation

# of

Events

Experiment KORSAR BLIND KORSAR OPEN

Open (s) Close (s) Open (s) Close (s) Open (s) Close (s)

1 48.0 131.0 54.0 147. 0 47.0 85. 0

2 165.0 175.0 178.0 188.0 100.0 118.0

3 222.0 231.0 228.0 237.0 137.0 154.0

46 3917.0 3938.0 3982.0 4018.0

47 4024.0 null 4112.0 null

53 4003.0 4034.0

54 2100.0 null

Table 4 SP-2 PCS-106A Operation

25

SP-2 Calculation Results

After the MFP trip and HPC vent valve SV-800 closing the

pressurizer pressure increases up to 9.064 MPa at 17 s and

core power becomes equal to decay power.

26

RPV and HPC Pressures

After the PCS-106A opening (53 s) the primary pressure is fast decreasing and

becomes equal to the saturation pressure at ~85 s. During the blowdown and long-

term cooling stages the primary pressure is slowly decreasing due to the core power

decreasing and vapor release through PCS-106A and PCS-106B.

27

Primary Mass Flow Rate at Core Outlet

Natural circulation (single phase) at

the beginning of transient and

natural circulation (two phase) at

the blowdown stage takes place.

As primary pressure is going down,

the primary mass flow rate is

decreasing too. The ejection of

vapor from RPV to HPC leads to

RPV water level decrease to upper

edge of the chimney and later on to

SG inlet. Average value of void

fraction at core outlet is about 0.1

during blowdown stage.

Chocked flow phenomenon takes

place in the vent line A.


28

Primary Mass Flow Rate

-2

-1

0

1

2

3

4

5

0 100 200 300 400 500 600 700 800 900 1000

Time, s

Mas

s Fl

ow R

ate,

kg/

s

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

Valv

e O

pen

Frac

tion

Primary Mass Flow Rate(Core Outlet) (kg/s) s.val106 (PSC-106)

-2

-1

0

1

2

3

4

5

2500 3000 3500 4000 4500

Time, s

Mas

s Fl

ow R

ate,

kg/

s

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

Valv

e O

pen

Frac

tion

Primary Mass Flow Rate(Core Outlet) (kg/s) s.val106 (PSC-106)

29

RPV Void Fraction


30


Core Enter/Exit Temperature

31

Heat Rod Temperature


32

RPV and HPC Levels


33

RPV Pressure Drops


34

SG Thermal-Hydraulic Behavior

Steam generator tube wall heat transfer and reactor power are

equal at the start of the transient. At the time 0.0 s according to

SP-2 procedure the feedwater flow through SG was terminated. At

the same time the vapor flow from SG was terminated, too.

After the feedwater loss the heat transfer to secondary side is

decreased to about zero. While the transient the heat transfer in

SG is directed to primary coolant, therefore the secondary side

temperature and pressure follow to the primary coolant

parameters.


35

Cumulative Discharge

After 4105 s the vent valves are kept open, and the flow rate slowly decreases due

to primary cool down.

Start of long-term cooling is obtained as 4143 s. At this time cumulative discharge

through PCS-106A from primary circuit into HPC is equal to about 50 kg .

Blind Open

36

HPC Water Temperature at

at 6.99 cm

Water Temperature inside HPC PRZ Level

Thermal stratification in the HPC and in the CPV is observed. The

water and HTP temperatures in the low part of HPC depend on the

depth of penetration of steam jet in water volume.


37

Water Temperature inside HPC

at 157 cm at 227 cm


38


at 6.99 cm at 157 cm


39


at 227 cm at 416.9 cm


40

Wall Temperature HTP near HPC

at 227 cm at 317 cm


41

Wall Temperature HTP near CPV

at 227 cm at 317 cm


42

Water Temperature inside CPV

at 227 cm at 317 cm


43

SP-2 Phenomena

Phenomena

HPC Pool: Thermal stratification 0

HPC Pool: Natural convection 0

HPC Pool: Steam condensation 0

HPC: Effect of non-condensable gases on condensation heat transfer +

HPC: Condensation on containment structures +

Distribution of pressure drop through primary system +

Break flow +

Single phase NC +

Two phase NC +

Intermittent two phase NC 0

Heat transfer in core +

Heat transfer in SG +

Primary-containment coupling during blowdown and long-term cooling 0

44

SP-3 Control Logic

The core power and feed water flow rate are equal to initial

values if time less than steady-time (tau< t_steady) and are

calculated using the tabular functions for tau > t_steady.

Feed Water Mass Flow Rate Core Power

45

Steady-State Comparison for Test SP-3 1/2

Parameter MASLWR Unit Experimental

Value

Steady-State Value

from Code

Pressurizer pressure PT-301 MPa(a) 8.719 8.718

Pressurizer level LDP-301 m 0.3574 0.3760

Power to core heater rods KW-101/102 kW 21.19/21.00 42.00

Feedwater temperature TF-501 ºC 31.49 31.5

Steam temperature FVM-602-T ºC 205.44 208.50

Steam pressure FVM-602-P MPa(a) 1.446 1.48

Ambient air temperature ºC 27.00

Primary flow at core

outlet

FDP-131 kg/s 0.68 0.743

Primary coolant

temperature at core inlet

TF-

121/122/

123/124

ºC 250.11/250.69

250.21/------

253.47

Primary coolant

temperature at core outlet

TF-106 ºC 262.76 264.27

46

Steady-State Comparison for Test SP-3 2/2

Parameter MASLWR Unit Experimental

Value

Steady-State Value

from Code

Feedwater flow FMM-501 kg/s 0.0102 0.0108

Steam flow FVM-602-M kg/s 0.0101

Primary coolant

subcooling at core outlet

ºC 36.75

Total heat loss through

primary system

kW 3.16

Heat transfer through SG kW 31.14

Maximum surface

temperature of core

heater rods

ºC 278.1

Location from the SG

secondary inlet to reach

- saturation

- superheat

m 0.2

0.6

47

SP-3 Time Sequence of Events

Event Time (s)

Start of simulation – steady state

(start of data collection)

from -1000.0 to 0.0

(0.0)

Initiate core power increase to 80 kW According to

4. ICSP_SP3_BCs_SI.xls Initiate core power increase to 120 kW

Initiate core power increase to 160 kW





48

Heat Transfer

RPV-SG Core


49

PRZ Level Chimney Mass Flow Rate


50

Steam Mass Flow Rate and FW Mass Flow


51

Core Heaters Temperature


52

Pressure Drops

DP-101 DP-105


53

Core Inlet Temperatures (SP-3)


54

Core Outlet Temperatures (SP-3)


55

Temperature difference (AVG (TF-131, 133, 134) – AVG (TF-121 to 124)) (SP-3)


56

Steam Temperature at SG Coil Outlet TF-611/612/…/635 Average (SP-3)


57

SP3 Phenomena

Phenomena

Distribution of pressure drop through primary system 0

NC: stability +

NC: reflux condensation -

Temp stratification in downcomer +

Single phase NC +

Two phase NC -

Intermittent two phase NC -

Heat transfer in core +

Heat transfer in SG +

SG: superheating in secondary +

58

SP-2

- The high dependence of the RPV&HPC&CPV parameters

behavior from ADS Lines characteristics while the transient .

- The assumption of formation of boundary layers nearby HTP

inside HPC (because of steam jet penetration into water volume)

and CPV is made. Modeling changes for the consideration of these

phenomena in Open Calculation are made.

- The SP-2 experimental data of temperatures distribution in HPC

and CPV may be used to verify of the 3-D heat and mass transfer

models in future.

SP-3

- There are need to take into account of the RPV heat losses

compensation system (PRZ Heaters) in SP-3 calculation.

Lessons learned

59

Conclusion

- Both Blind and Open Calculations were perform with

KORSAR/GP code.

- At the Open Calculation performance some discrepancies

of the model (input deck) used for Blind Calculation are

considered. In particular, the boundary condition at Steam Line

output is corrected, the value of loss coefficient for PCS-106A, B

line is corrected either.

- The assumption of formation of boundary layers nearby

HTP inside HPC (because of steam jet penetration into water

volume) and CPV is made. Modeling changes for the

consideration of these phenomena in Open Calculation are

made.

60

Conclusion (Cont)

- Open calculation using corrected model has allowed to

reduce the differences between calculated values of some

parameters and experimental data for SP-2 (RPV and HPC levels,

HPC and HTP and CPV temperatures, etc.).

- For the Open Calculation developed model of MASLWR

experimental facility on the basis of KORSAR code allows to

execute modeling of SP-2 and SP-3 natural circulation

experiments.

- Results of Blind and Open Calculations of SP-2 and SP-3

experiments quite well coincide with experimental data.

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