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Decision of IAEA International Collaborative Standard Problem on Integral PWR “Blind Calculation” using KORSAR/GP Code Yu.Sorokin, N.Fil, N.Bukin

Third Technical Meeting/Workshop for the ICPS on Integral Water Cooled Reactor Design, Daejeon 27-30 March 2012

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ICSP “Blind Calculation” International Collaborative Standard Problem (ICSP) on «Integral PWR» is performed by IAEA and OSU, suggested to perform this ICSP on the basis of the experiments executed on MASLWR test facility. “Blind Calculation” Tests: SP-2: Loss of Feedwater Transient with Subsequent ADS Operation and Long Term Cooling; SP-3: Normal Operating Conditions at Different Power Levels

3

MASLWR SCHEME

MASLWR – is a small modular pressurized light water reactor relying on natural circulation during both steady-state and transient operation.

4

Oregon State University has constructed a system-level test facility to assess computer codes for reactor system design and analysis.

OSU MASLWR Test Facility

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KORSAR/GP Code Russian Thermal Hydraulic KORSAR/GP Code was used for MASLWR parameters estimation during SP-2 & SP-3 experiments at Blind Calculation phase. KORSAR/GP is the Best Estimate Code and it is intended for analyses of LWR processes in stationary, transitive and emergency operation.

Modelling of Thermal Hydraulic processes in KORSAR/GP: - nonequilibrium two-liquid model (on three equations of preservation for water and steam phases); - one-dimensional approach; - non-condensable gases.

6

1 What nodalization strategies have been used, if any, in model development?

All of geometric data has been collected or calculated from information found in the MASLWR Test Facility Description Report, Problem Specification and the Table 1 of OSU-MASLWR-08002 (Draft).

2 Have any 2/3D component been used to model any of the

following components?

Two parallel connected the channels were used for HPC.

MODEL ASSUMPTIONS 1/5

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3 How have the following components been modeled—separately or lumped in N pipes?

All core heaters lumped together. All SG coil tubes lumped together. The three helical SG coils are

modeled as single pipe volume with the flow and heat transfer areas kept same.

4 Have the following components been modeled? PRZ heaters - no HPC heaters - no steam line – yes, channel connected to steam drum, feed water lines – no

MODEL ASSUMPTIONS 2/5

8

MODEL ASSUMPTIONS 2/5 5 Have the following components been modeled separately?

blowdown lines – no two vent lines – no two sump recirculation lines – no

Every pare of lines are modeled as single equivalent channel. 6 Has the insulation on any of the following components been

modeled? The insulation of RPV, HPC and ADS lines are modeled. CPV is at adiabatic condition.

9

MODEL ASSUMPTIONS 3/5 7 Has the heat loss from the following components been

simulated? Heat loss from CPV to the atmosphere is neglected. Heat losses from RPV & HPC & ADS lines have been simulated.

The outer surface temperature is equal to ambient temperature.

8 Describe specific models used for the following phenomena:

Heat transfer in the helical coils – the correlations for bundle of rods is used

Condensation in the HPC – standard model of KORSAR Choked flow – standard model of KORSAR

10

MODEL ASSUMPTIONS 4/5 9 Has you model been checked against available

characterization data such as height versus volume and the heat structure mass?

Only the relative elevation of hydraulic channels and heat structures are checked automatically in KORSAR.

10 Are there any differences between the SP-2 and

SP-3 models? The model (nodalization scheme) is the same.

11

MODEL ASSUMPTIONS 5/5 11 Are there any changes in model or methodology between

blind and double blind calculation results? Nodalization schemes are similar. Some changes are made in model for Blind Calculation

concerning the model used for Double Blind Calculation. For modelling the Steam Drum and Steam Line the channels

(ch20, ch40) were added. For modelling the Heat Losses and accumulated heat the

fallowing heat-conducting structures were added: - steam drum bottom, head and wall with insulation (HCS20,

HCS23, HCS24); - steam line with insulation (HCS40); - HPC wall with insulation (HCS200 and HCS201); - Vent Line (PCS-106) wall with insulation (HCS106), - RPV flange with insulation (HCS25).

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The KORSAR Nodalization Diagram of the MASLWR Test Facility for Blind Calculation

Val800

bljun1

Val107

Ch107

Ch108

Val108

Val103

Ch103

Val106

Ch106

Ch210

Val30

Ch30

smass_t1

bvol_t3

HCS3

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

HCS1

Ch100

Ch3

Ch10

Ch20

Col30

HCS40

HCS2

HCS4

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

HCS30

0

Ch200-21Ch300-21

Ch300-22 Ch200-22

HCS20

1HC

S200

HCS106

Val501

Ch40

HCS25

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Heat elements used in KORSAR nodalization scheme Name Rin,m Rout,m Material

HCS1(1:5) Core Heater 0.0 0.00795 steel HCS2(1:30) RodsSG tubes 0.0063 0.00795 steel HCS3(1:18) 0.1971 0.2032 steel HCS4(1:21) RPV Wall 0.1460 0.1778+0.102 steel+ thermo12 HCS200(1:17) HPC Wall 0.1329 0.135+0.102 steel+ thermo12 HCS201(1:5) HPC Wall 0.2516 0.254+0.102 steel+ thermo12 HCS106(1:8) Vent line Wall

(PCS106) 0.0 0.008 steel+ thermo12

HCS20(1:2) Steam Drum Wall 0.2951 0.3048+0.102 steel+ thermo12 HCS22(1:2) RPV Wall 0.1460 0.1778 steel HCS25(1) RPV Flange 0.1460 0.3048 steel+ thermo12 HCS40(1:15) Steam Line Wall 0.01752 0.02108+0.05 steel+ thermo12

Thickness Wide

HCS300(1:22) Heat Transfer Plate 0.05 0.168 steel HCS23(1:2) SD Bottom 0.0175 steel+ thermo12 HCS24(1:2) SD Head 0.0175 steel

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Regime map of heat transfer to the wall

Tw – wall temperature, Tcr- critical temperature (corresponding to critical heat flux) Tmin - minimal temperature of steady film boiling

KORSAR use the original technique for calculating closing relations and closing relations taken from the published data too. Heat transfer correlations are similar to ones used in Best Estimate codes (CATHARE, RELAP5) and modified for WWER.

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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 (According to 4. ICSP_SP3_BCs_SI.xls).

Feed Water Mass Flow Rate Core Power

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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 0.743

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

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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 0.0108

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

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SP-3 Calculation Results The behavior of primary and secondary parameters is defined by the boundary conditions: the core power and feed water flowrate. The increasing of the core power results in the increasing of the core mass flowrate, the core exit temperature, the core temperature difference and the heat transfer from primary to secondary side. The increasing of the feed water flowrate results in the increasing of heat transfer from primary to secondary side and decreasing of the core enter temperature.

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SP-3 Calculation Result

Heat Flux Feed Water Mass Flow

At about 2700 s the large rise of feed water flow rate occurs, heat transfer to secondary side becomes larger than core power, and the farther behaviors of primary and secondary parameters depend from this rise.

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SP-3 Calculation Result

Steam Mass Flow Rate Feed Water Mass Flow Rate

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SP-3 Calculation Results

Pressurizer Level Pressurizer Pressure

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SP-3 Calculation Results

RPV Mass Flow

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

0 1000 2000 3000 4000 5000 6000

Time, s

Ma

ss

Flo

w R

ate

, k

g/s

Core Pressure Difference

Two basic factors influence on the primary pressure drops: primary coolant density and mass flow rates. The core pressure drop is defined mainly by the mass flow rate. Increasing of the core mass flow rate results in the core pressure drop increasing.

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Pressure Difference (SP-3)

For the other pressure drops the influence of the primary coolant density is larger then the influence of the mass flow rate, so they increase (decrease) if coolant density becomes higher (lower).

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RPV Pressure Drop (SP-3)

25

SP-3 Calculation Results

Core Enter/Exit Temperature Core Heater Temperature

26

Steam Temperature (inside Steam Line) SP-3

27

Dependence of Core Parameters from Core Power (SP-2)

0

5

10

15

20

25

30

35

40

41,8 80 119 159 199 238 280 318

Power, kW

dT C

ore,

deg

.C

0,0

0,20,4

0,60,8

1,0

1,21,4

1,61,8

2,0

Mas

s Fl

owra

te, k

g/s

dT Core deg. CMass Flowrate kg/s

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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.

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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

Ch10

7

Ch10

8

Val108

Val103

Ch103

Val106

Ch106

Ch21

0

Val30

Ch30

smass_t1

bvol_t3

HCS

3

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

HCS

1

Ch100

Ch3

Ch10

Ch20

Col30

HCS

40

HCS

2

HCS

4

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

HCS

300

Ch200-21Ch300-21

Ch300-22 Ch200-22

HCS

201

HCS

200

HCS106

Val501

Ch40

HCS25

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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 26.87 HPC water level LDP-801 m 2.8204 2.8005 Primary flow at core outlet

FDP-131 kg/s 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

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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 0.108

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

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SP-2 Time Sequence of Events

Event Time (s) Start of simulation – steady state (start of data collection)

from -1000.0 to 0.0 (-600.0)

Stop MFP Close HPC vent valve SV-800

0.0

PZR pressure (PT-301) reaches 9.064 MPa(a) (1300 psig) Enter decay power mode

17.0

De-energize PZR heaters Open ADS vent valve (PCS-106A)

53.0

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

4143.0

End of test when one of the following conditions is reached: - PZR pressure (PT-301) ≤ 0.61 MPa(a) (75 psig)

14000.0

33

Record opening and closing times for PCS-106A Experiment KORSAR

# of Events Open (s) Close (s) Open (s) Close (s)

1 48.00 131.00 54.00 147. 00

2 165.00 175.00 178.00 188.00

3 222.00 231.00 228.00 237.00

4 287.00 295.00 289.00 298.00

5 359.00 367.00 358.00 367.00

6 434.00 443.00 433.00 442.00

7 512.00 520.00 506.00 515.00

8 591.00 599.00 575.00 584.00

9 670.00 678.00 646.00 655.00

10 750.00 758.00 719.00 728.00

11 830.00 838.00 794.00 803.00

12 911.00 919.00 869.00 878.00

13 993.00 1000.00 942.00 951.00

14 1074.00 1082.00 1014.00 1023.00

15 1156.00 1164.00 1087.00 1097.00

16 1240.00 1248.00 1159.00 1169.00

17 1323.00 1331.00 1229.00 1239.00

18 1406.00 1414.00 1300.00 1309.00

19 1490.00 1498.00 1371.00 1381.00

20 1574.00 1582.00 1444.00 1454.00

Table 4 SP-2 PCS-106A Operation

Experiment KORSAR

# of Events Open (s) Close (s) Open (s) Close (s)

21 1658.00 1666.00 1519.00 1529.00

22 1743.00 1751.00 1596.00 1606.00

23 1828.00 1836.00 1667.00 1677.00

24 1913.00 1922.00 1739.00 1750.00

25 1999.00 2008.00 1813.00 1824.00

26 2085.00 2094.00 1885.00 1896.00

27 2171.00 2181.00 1957.00 1967.00

28 2259.00 2268.00 2027.00 2038.00

29 2345.00 2355.00 2100.00 2111.00

30 2433.00 2443.00 2177.00 2188.00

31 2521.00 2531.00 2254.00 2265.00

32 2609.00 2619.00 2327.00 2339.00

33 2697.00 2707.00 2400.00 2412.00

34 2786.00 2796.00 2475.00 2488.00

35 2876.00 2886.00 2548.00 2562.00

36 2966.00 2977.00 2623.00 2636.00

37 3056.00 3068.00 2696.00 2709.00

38 3148.00 3160.00 2770.00 2784.00

39 3240.00 3252.00 2848.00 2861.00

40 3332.00 3345.00 2928.00 2942.00

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Record opening and closing times for PCS-106A Experiment KORSAR

# of Events Open (s) Close (s) Open (s) Close (s)

41 3426.00 3439.00 3011.00 3026.00

42 3521.00 3535.00 3089.00 3104.00

43 3617.00 3632.00 3168.00 3184.00

44 3715.00 3731.00 3249.00 3267.00

45 3814.00 3832.00 3329.00 3347.00

46 3917.00 3938.00 3408.00 3427.00

47 4024.00 null 3487.00 3506.00

48 3566.00 3586.00

49 3647.00 3669.00

50 3730.00 3753.00

51 3816.00 3841.00

52 3905.00 3932.00

53 4003.00 4034.00

54 4105.00 null

35

Core Power (SP-2)

36

PSC-106A, PSC-106B Mass Flow Rate (SP-2)

After the PSC-108A opening (53 s) the primary pressure is fast decreasing and becomes equal to the saturation pressure at ~85 s. At the moment of opening the value of the mass flow rate through PSC-106A is about 0.68 kg/s, then it is decreasing and at the moment of the first PSC-106A closing it is less then 0.07 kg/s.

37

PSC-106A, PSC-106B Mass Flow Rate (SP-2)

At second opening the peak value of flow rate don’t exceed 0.08 kg/s and every next value becomes lower then previous value.

38

PSC-106A, PSC-106B Mass Flow Rate (SP-2)

After 4105 s the vent valves are kept open, and the flow rate slowly decrease from 0.005 till 0.001 kg/s due to primary cool down.

39

PSC-108A, PSC-108B Mass Flow Rate (SP-2)

During time from 4143 up to 4400 s average value of the mass flow through PSC-108A (PSC-108B) decrease up to negative values,the direction of a flow is changed (from HPC up to RPV).

40

Cumulative Discharge (SP-2) Start long-term cooling is obtained as 4143 s. At this time cumulative discharge through PSC-106A from primary circuit into HPC is equal to about 50 kg.

41

Primary Mass Flow Rate (SP-2)

-1

0

1

2

3

4

5

-1000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000

Time, s

Mas

s Fl

ow R

ate,

kg/

s Primary Mass FlowRate (Upper Plenum toSG) (kg/s)

-1

0

1

2

3

4

5

-1000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000 12000 13000 14000 15000

Time, s

Mas

s Fl

ow R

ate,

kg/

s Primary Mass FlowRate (Chimney to UpperPlenum) (kg/s)

42

Primary Mass Flow Rate (SP-2)

-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)

43

Primary Mass Flow Rate (SP-2)

-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)

44

RPV and HPC Pressures (SP-2)

45

RPV and HPC Level (SP-2) At 8000 s the RPV and HPC levels and pressure drops stabilization take place.

46

RPV Pressure Difference (SP-2)

47

Core Pressure Difference (SP-2)

48

Core Temperatures (SP-2)

Core Enter/Exit Temperature Core Heaters Temperature

49

RPV Void Fraction (SP-2)

0

0,2

0,4

0,6

0,8

1

0 2000 4000 6000 8000 10000 12000 14000

Time, s

Vo

id F

rac

tio

n Void Fraction (UpperPlenum Bottom)

The void fraction in upper part of RPV is equal to 1.

50

Wall Temperature HTP near HPC Water Temperature inside HPC

HPC Temperatures (SP-2) Release of hot steam into HPC leads to heating of the HPC wall and to heating of the HPC steam and water.The HPC wall is cooling through the heat plate (between CPV and HPC) .

51

Water Temperature inside CPV

CPV Temperatures (SP-2)

52

Conclusion During the decision of the International Collaborative Standard Problem at the Blind Calculation stage : - The modification of nodalization scheme and input deck is developed for MASLWR test facility modeling using the KORSAR/GP code; -The analysis of SP-3 and SP-2 experiments is executed; -The more detailed analysis of the SP-2 and SP-3 will be made at the Open Calculation stage .