SUPERCRITICAL CO2 HEAT REMOVAL SYSTEM - …•A sensitivity study was performed in order to see the...

www.sCO2-HeRo.eu

A.Vojacek, V.Hakl, P.Hajek

SUPERCRITICAL CO2 HEAT REMOVAL SYSTEM -INTEGRATION INTO

EUROPEAN PWR FLEET

Content

• Basic design– SBO-SG_HRS– Contaiment_HRS

• System integration• Thermodynamic analysis

– Cycle calculation – optimization of parameters– Heat exchangers calculations– Calculation of thermodynamic parameters for off-design

conditions– Control strategy

• Open issues• Conclusions

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3

Basic design - integration to the NPP defense in depth concept IAEA

Levels ofdefense indepth

Associated plant conditioncategories

Objective Essential means

DID 1 DBC - Normal operation Prevention of abnormal operationand failures

Conservative design and highquality in construction andoperation, control of main plantparameters inside defined limits

DID 2 DBC - Anticipated operationaloccurrences (abnormal)

Control of abnormal operation anddetection of failures

Control, limiting and protectionsystems and other surveillancefeatures

DID 3 Design basis accidents (postulatedsingle initiating events)

Control of accident to limitradiological releases and preventescalation to core melt conditions

LOCAReactor protection system, safetysystems, accident procedures

DID 4a DEC - Postulated multiple failureevents

SBO

LOCA (no emergency

active cooling system

available )

Additional safety features, accidentprocedures

DID 4b Beyond design basis accidentsSevere accidents

Control of accidents with core melt tolimit off-site releases

Core melt, directCont. heating, coriumcooling

Complementary safety features tomitigate core melt, Management ofaccidents with core melt (severeaccidents)

DID 5 - Mitigation of radiologicalconsequences of significant releasesof radioactive material

Off-site emergency response

SBO-SG_HRS Containment_HRS

• SBO-SG_HRS system should work in case of Station BlackOut, in defense in depth level DID 4a - design extension condition DEC - Postulated multiple failure events according IAEA or DID 3b Selected Multiple failures events according WENRA.

• Containment_HRS serves for removal of heat from containment and it should work in case of any rupture in primary circuit. It can be used in case of LOCA accident DID 3 - Design basis accidents (postulated single initiating events) according IAEA or DID 3a Postulated single initiated events according WENRA and in case of SA (Severe accidents) DID 4b - Beyond design basis accidents according IAEA or DID 4 – Postulated Core Melt Accidents according WENRA.

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Basic design - integration to the NPP defense in depth concept IAEA

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Basic design - SBO-SG_HRS

• SBO-SG_HRS is Self-propellant, self-sustaining and self-launching. The self-launching system is conditioned by:– For newly build NPP, is possible to integrate SBO-SG_HRS to

DID logic sequence, because it’s newly developed in the design phase of project.

– For currently operated units, it’s difficult to add SBO-SG_HRS system as self-launching - operator manually actuated systems needed.

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Basic design - SBO-SG_HRS

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Basic design - Containment_HRS

• Design of Containment_HRS (Heat Removal System) can be self-propellant, but not self-sustaining and self-launching because of changing conditions inside containment.

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Basic design - Containment_HRS

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System integration - SBO-SG_HRS

• Arrangement of four units in containment– System consists of 4 individual trains

• System componentsPipelines, Isolation valve – vapor/ water, Containment localization group of valves, CO2 loop turbo machinery, Breather valve, Heat exchanger CO2 / air, Heat exchanger steam / CO2, Air fan, Start up system, Storage and supply of CO2 gas

• System functions• System requirements• Operational regimes and parameters• Power supply

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11


12


steam/sCO2 micro heatexchangers each for for 5MWth

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• Arrangement of four units in containment– System consists of 4 individual trains

• System componentsPipelines, Containment localization group of valves, CO2 loop turbo machinery, Heat exchanger CO2 / air, Heat exchanger steam / CO2, Air fan, Start up system, Storage and supply of CO2 gas

• System functions• System requirements• Operational regimes and parameters• Power supply

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System integration - Contaiment_HRS

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System integration - Contaiment_HRS

Thermodynamic analysisCycle calculation – optimization of parameters

•The sCO2-HeRo cycle is design as a simple Brayton cycle.•The optimization is based on searching a compressor inlet and compressor outlet pressure of cycle to receive the highest efficiencies of the cycle.• thermodynamic values of the cycle which were considered.

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Variable Value Unitinlet temperature sCO2 to the compressor 30, 40 and 50 °Cinlet temperature sCO2 to the turbineCONTAIMENT_HRS/SBO-SG_HRS

114.0/280.0 °C

inlet pressure sCO2 to the compressor 75, 100, 125 and 150 barinlet pressure sCO2 to the turbine 100, 150, 200 and 300 barthermal power of heat source 5000.0 kWisentropic efficiencies of the compressor 0.65, 0.75 and 0.8 -isentropic efficiencies of the turbine 0.75, 0.85 and 0.9 -


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SBO-SG_HRS system optimization

0

2

4

6

8

10

12

14

16

18

0 10 20 30 40

eff [

%]

p_compr_out [MPa]

eff [%] for T_compr_in=30°C, ny_compr=0.75, ny_turb=0.85

p_compr_in=7.5 MPa

p_compr_in=10 MPa

p_compr_in=12.5 MPa

p_compr_in=15 MPa


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0

2

4

6

8

10

12

14

0 10 20 30 40

eff [

%]

p_compr_out [MPa]


p_compr_in=7.5 MPa

p_compr_in=10 MPa

p_compr_in=12.5 MPa

p_compr_in=15 MPa


20


0

2

4

6

8

10

12

0 5 10 15 20 25 30 35

eff [

%]

p_compr_out [MPa]


p_compr_in=7.5 MPa

p_compr_in=10 MPa

p_compr_in=12.5 MPa

p_compr_in=15 MPa


•According to Czech authority (SUJB) all safety systems needs to be designed for extreme climatic conditions, i.e. air temperature 45°C. On the other hand, the system should be able to work during winter temperatures below zero °C as well.•A sensitivity study was performed in order to see the behavior of cycle in off-design inlet compressor temperature to prevent difficulties when setting improper nominal design conditions.

•Thermodynamic parameters of cycle designed for 55°C of compressor inlet and influence on the cycle for 30°C


•It is evident that the system designed for nominal conditions 30°C compressor inlet has a few percent higher power output than the system designed for 55°C during off-design 30°C. However, this system would shows worse performance at off-design 55°C which has the highest importance.

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T1 [°C] p1 [MPa] p2 [MPa] m [kg/s] η_cycle [%] P_cycle [MW]55.00 11.67 17.51 15.36 5.39 0.2730.00 11.67 17.51 11.58 5.33 0.27




•nominal thermodynamic values of the SBO-SG_HRS cycle which were selected as an optimum.•The pressure ratio was limited to 1.5 so to keep one stage design of compressor and having acceptable low rpm.

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Variable Value Unitinlet temperature sCO2 to the compressor 55.0 °Cinlet temperature sCO2 to the turbine 280.0 °Coutlet temperature sCO2 of the compressor 77.1 °Coutlet temperature sCO2 of the turbine 240.9 °Cinlet pressure sCO2 to the compressor 116.7 barinlet pressure sCO2 to the turbine 175.1 barmass flow rate of sCO2 15.4 kg/sthermal power of heat source 5000.0 kWthermal power of sink HX 4730.0 kWisentropic efficiencies of the compressor 0.75 -isentropic efficiencies of the turbine 0.85 -power of turbine 500.0 kWpower of compressor 230.0 kWpower output of cycle 270.0 kWcycle efficiency 5.4 %

The preliminary calculation of compressor and turbine sizing was performed according toAungier (R. Aungier, Centrifugal compressor).



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-2

-1

0

1

2

3

4

5

6

7

8

0 10 20 30 40

eff [

%]

p_compr_out [MPa]


p_compr_in=7.5 MPa

p_compr_in=10 MPa

p_compr_in=12.5 MPa

p_compr_in=15 MPa

CONTAINMENT_HRS system optimization


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-10

-8

-6

-4

-2

0

2

4

6

8

10

0 10 20 30 40eff

[%]

p_compr_out [MPa]


p_compr_in=7.5 MPa

p_compr_in=10 MPa

p_compr_in=12.5 MPa

p_compr_in=15 MPa


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-10

-8

-6

-4

-2

0

2

4

6

8

10

0 5 10 15 20 25 30 35eff

[%]

p_compr_out [MPa]


p_compr_in=7.5 MPa

p_compr_in=10 MPa

p_compr_in=12.5 MPa

p_compr_in=15 MPa


•According to Czech authority (SUJB) all safety systems needs to be designed for extreme climatic conditions, i.e. air temperature 45°C. On the other hand, the system should be able to work during winter temperatures below zero °C as well.•A sensitivity study was performed in order to see the behavior of cycle in off-design inlet compressor temperature to prevent difficulties when setting improper nominal design conditions.



•It is evident that the system designed for nominal conditions 30°C compressor inlet has higher power output, approximately double than the system designed for 45°C during off-design 30°C. However, this system would not be self-propellant during off-design 45°C which has the highest importance.

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T1 [°C] p1 [MPa] p2 [MPa] m [kg/s] η_cycle [%] P_cycle [MW]45.00 7.21 14.43 327.29 -69.73 -3.4930.00 7.21 14.43 28.77 7.28 0.36


•nominal thermodynamic values of the CONTAINMENT_HRS cycle which were selected as an optimum.

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Variable Value Unitinlet temperature sCO2 to the compressor 45.0 °Cinlet temperature sCO2 to the turbine 114.0 °Coutlet temperature sCO2 of the compressor 63.6 °Coutlet temperature sCO2 of the turbine 79.3 °Cinlet pressure sCO2 to the compressor 102.8 barinlet pressure sCO2 to the turbine 158.5 barmass flow rate of sCO2 38.2 kg/sthermal power of heat source 5000.0 kWthermal power of sink HX 4840.0 kWisentropic efficiencies of the compressor 0.75 -isentropic efficiencies of the turbine 0.85 -power of turbine 650 kWpower of compressor 490 kWpower output of cycle 160 kWcycle efficiency 3.2 %

The preliminary calculation of compressor and turbine sizing was performed according toAungier (R. Aungier, Centrifugal compressor).

Thermodynamic analysisHeat exchangers calculations - SBO-SG_HRS system

• 1D approach using heat transfer correlations was used• Detailed description in the deliverable report D1.3 - Documentation system integration into

European LWR fleet

281st year meeting 29 – 30 June 2016

quantity for total 4x5 MWth: 24


Thermodynamic analysisHeat exchangers calculations - CONTAINMENT_HRS system

• 1D approach using heat transfer correlations was used• Detailed description in the deliverable report D1.3 - Documentation system integration into

European LWR fleet

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Thermodynamic analysisCalculation of thermodynamic parameters for off-design conditions

•Dymola software (modeling language Modelica) with implemented ClaRa 1.1.0. library was used.•Some adaptation had to made:

–A basic model for axial steam turbine using Stodola’s cone law is already implemented in ClaRa 1.1.0. and has been adapted for the representation of radial turbines.–implementation of a mechanical port (shaft) evaluating a dynamic torque balance–introducing isentropic efficiency for off-design conditions which includes the influence of aerodynamic losses, as recommended by Dyreby et al. used in Venker’s dissertation

•As for the compressor (pump), the derived dynamical equations for the model consider balance of certain properties, like mass, energy and momentum. Furthermore, mechanical and hydraulic efficiency of the pump are used. The behavior of the compressor (pump) at off-design speeds is assumed to follow a quadratic affinity law.

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•SBO-SG_HRS model in Modelica for nominal state (air temperature 45°C)

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•SBO-SG_HRS thermodynamic parameters for off-design conditions air temperature range 20°C –50°C

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T_air[°C]

T3 [°C]

T1 [°C]

m_CO2 [kg/s]

p1 [bar]

p2 [bar]

P_cycle [kW]

P_T [kW]

P_C [kW]

50 280 58.8 15.5 122.8 180.1 236 472 23645 280 55 15.4 116.6 175 266 497 23140 280 51.2 15.2 110.1 169.6 295 521 22630 280 44 14.9 97.6 159.5 339 570 23120 280 37.7 14.5 86.2 150.1 377 613 236

T_air[°C]

Q_in[kW]

Q_out [kW]

η_cycle [%]

dT3 [K]

dT1 [K]

50 4918 4682 4.80 0 3.845 4990 4724 5.33 0 040 5046 4751 5.85 0 -3.830 5151 4812 6.58 0 -1120 5213 4836 7.23 0 -17.3

The resulted off-design thermodynamic parameters for air temperature range 20°C – 50°C, i.e. -25 K to +5 K from nominal condition, are displayed.


•Temperature of air above 50°C is not expected. During temperatures of air below 20°C the system will need an active intervention in terms of switching-off the individual sections of SBO-SG_HRS sink HXs to set the system according to the actual air temperature. Total number of these HXs is 6.

•The number of SBO-SG_HRS sink HXs needed in operation for actual air temperature T_air was calculated.

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01234567

-20 -10 0 10 20 30

n_SB

OHX

s [-]

T_air [°C]

Number of SBO-SG_HRS sink HXs neededaccording to air temperature T_air


•CONTAINMENT_HRS model in Modelica for nominal state (air temperature 40°C)

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•CONTAINMENT_HRS thermodynamic parameters for off-design conditions air temperature range 20°C – 50°C

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T_air[°C] T3 [°C]

T1 [°C]

m_CO2 [kg/s] p1 [bar]

p2 [bar]

P_cycle [kW]

P_T [kW]

P_C [kW]

50 116.9 51.4 38.5 113.8 166.8 65 585 52045 115.7 48.7 38.4 108.5 162.9 103 612 50940 114 45 38.2 102.6 158.5 151 651 50030 111.4 38.6 37.9 91.6 150.5 200 728 52820 109.1 33.1 37.2 79.6 141.3 243 799 556

T_air[°C]

Q_in[kW]

Q_out[kW]

η_cycle [%]

dT3 [K]

dT1 [K]

50 4436 4371 1.47 2.9 6.445 4662 4559 2.21 1.7 3.740 4977 4826 3.03 0 030 5555 5355 3.60 -2.6 -6.420 6075 5832 4.00 -4.9 -11.9

The resulted off-design thermodynamic parameters for air temperature range 20°C – 50°C, i.e. -20 K to +10 K from nominal condition, are displayed.


•Temperature of air above 50°C is not expected in potential location of first deployment (Europe). Higher temperatures can be critical. During temperatures of air below 20°C the system will need an active intervention in terms of switching-off the individual sections of CONTAINMENT_HRS sink HXs. Total number of these HXs is 24 so there is quite a flexibility to set the system according to the actual air temperature.•The number of CONTAINMENT_HRS sink HXs needed in operation for actual air temperature T_airwas calculated.

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0

10

20

30

-20 -10 0 10 20 30n_L

OCA

HXs

[-]

T_air [°C]

Number of CONTAIMENT_HRS sink HXs needed according to air temperature

T_air

Thermodynamic analysisControl strategy

•Two control strategies of the sCO2-HeRo cycles were investigated–regulating the electric side with resistor - speed of the machines is kept constant, all excess generated power will be wasted in the resistor. The results showed previously supposed this approach.–regulating the bypass over the turbine - The bypass valve is used for regulating power of turbine on actual temperature of air and actual decay heat. This valve bypasses part of the flow around the turbine, thus reducing the amount of work added to the shaft. The regulation range of thermal power (decay) removed by sCO2-HeRo is approximately 4.2 – 8.4 MWth.

•Deployment of sCO2-HeRo systems during decay heat for the SBO-SG_HRS system with regulating the bypass over the turbine

37

decay heat [MW] Q1 [MWth] Q2 [MWth] Q3 [MWth] Q4 [MWth]33.6 8.4 8.4 8.4 8.432 8 8 8 831 7.75 7.75 7.75 7.7530 7.5 7.5 7.5 7.529 7.25 7.25 7.25 7.2528 7 7 7 727 6.75 6.75 6.75 6.7526 6.5 6.5 6.5 6.525 6.25 6.25 6.25 6.2524 6 6 6 623 5.75 5.75 5.75 5.7522 5.5 5.5 5.5 5.521 5.25 5.25 5.25 5.2520 5 5 5 519 4.75 4.75 4.75 4.75

decay heat [MW] Q1 [MWth] Q2 [MWth] Q3 [MWth] Q4 [MWth]18 4.5 4.5 4.5 4.517 4.25 4.25 4.25 4.2516 5.33 5.33 5.33 -15 5 5 5 -14 4.67 4.67 4.67 -13 4.33 4.33 4.33 -12 6 6 - -11 5.5 5.5 - -10 5 5 - -9 4.5 4.5 - -8 8 - - -7 7 - - -6 6 - - -5 5 - - -

• Open issues:– Possibility of use frequency inverter in safety system.– Acceptance of special plate heat exchangers by nuclear

community and regulatory body.– Start-up system (energy source).– Problems with health and safety inspection – large

quantities of CO2 inside units building.– Phenomenology of heat exchanger inside containment for

Containment_HRS. Different heat transfer conditions. – CO2 loop – changing of critical point by mixing gases for

better cycle efficiency.

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Open issues for Containment_HRS and SBO-SG_HRS

Conclusions

It can be concluded that according to performed analyses for the PWR the aim of having integrated the sCO2-HeRo system into the real power plant is feasible as a safe, reliable and efficient residual heat removal system from the nuclear reactor vessel without the requirement of external power sources.

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Foliennummer 1ContentFoliennummer 3Foliennummer 4Foliennummer 5Foliennummer 6Foliennummer 7Foliennummer 8Foliennummer 9Foliennummer 10Foliennummer 11Foliennummer 12Foliennummer 13Foliennummer 14Foliennummer 15Thermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Cycle calculation – optimization of parametersThermodynamic analysis� Heat exchangers calculations - SBO-SG_HRS systemThermodynamic analysis� Heat exchangers calculations - CONTAINMENT_HRS systemThermodynamic analysis� Calculation of thermodynamic parameters for off-design conditionsThermodynamic analysis� Calculation of thermodynamic parameters for off-design conditionsThermodynamic analysis� Calculation of thermodynamic parameters for off-design conditionsThermodynamic analysis� Calculation of thermodynamic parameters for off-design conditionsThermodynamic analysis� Calculation of thermodynamic parameters for off-design conditionsThermodynamic analysis� Calculation of thermodynamic parameters for off-design conditionsThermodynamic analysis� Calculation of thermodynamic parameters for off-design conditionsThermodynamic analysis� Control strategyFoliennummer 38Conclusions

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