Validation of the CATHARE2 code against experimental data from Brayton-cycle plants

1HTR 2006, October 1-4, 2006, Johannesburg, South AfricaValidation of the CATHARE code against experimental data from Brayton cycle plants

Validation of the CATHARE code Validation of the CATHARE code against experimental data from against experimental data from BraytonBrayton cycle cycle

plantsplants

Fabrice Bentivoglio, Nicolas TauveronCEA, DEN/DER


ContextContext

Gas Cooled Reator Thermal Hydraulic simulations, with the system code CATHARE:

•Describe the thermal hydraulics of the whole plant, primary and secondary circuits.

•Analyze the behavior of GCR in both normal operation and various accident transients

•Answer to specific demand of designers

•Design and optimisation of I&C systems

•Incidents and accidents analyses for plant safety evaluation

Need of validation against existing experimental data for a reliable and efficient tool

Comparison CATHARE/ Experiment on two system loopsOberhausen I and II (Brayton cycles, Germany),


CATHARECATHARE appliedapplied to to GasGas CooledCooled ReactorReactor

• CATHARE is the reference safety code for French nuclear program (EdF, IRSN, FRA-ANP, CEA) firstly developed for Pressurized Water Reactors

• Adapted for all the different concepts of Gas-Cooled Reactors (GCR) with Specific features integrated as independent options in the standard version of CATHARE

– OD turbomachinery module

– Specific Core thermal modeling with a simplified 2D conduction calculation (for VHTR)

– Neutron kinetics feedback model specific to the GCR

– Physical correlations (gas properties, specific components correlations (HX)…)

A unique version of CATHARE to take benefit of the code “structure” (stringent procedures for documentation and maintenance)


Validation on Validation on experimentalexperimental data: 3 data: 3 stepssteps

•Validation on Component Tests (recuperator, turbomachinery…)

•Validation on System Tests Facility to take into account allthe dynamic interactions during transient situations, includingregulations

Oberhausen I and II (Brayton cycles, Germany),

PBMM (Pebble Bed Micro Model, South Africa),EVO II

Recuperator

Inter Cooler

Turbo machinery

Electric Heater

Pre Cooler

•Validation on Separate Effect Tests to get the adequate heattransfer and pressure drop coefficients for all the flow conditions (in the core and heat exchangers)

Rmk: paper H8, « Comparison of the Thermal-Fluid Analysis Code Flownex with Experimental Data From the Pebble Bed Micro Model”

PBMM


Introduction on Introduction on OberhausenOberhausen II facilityII facility

“Oberhausen II, operated by the German utility EnergieVersorgung Oberhausen(EVO), is a 50 MW(e) direct-cycle Helium turbine plant . The facility was part of a large German R&D program initiated in 1968 to demonstrate the feasibility of a Brayton-cycle power conversion system with Helium turbomachines. The power

source is a gas burner rather than a nuclear reactor core, but the power conversion system resembles those of the GCR concepts. Oberhausen II was operated for

more than 25 000 hours between 1974 and 1988.”

Measurement of temperatures, pressures and mass flows all along the circuit.

About 20 plans (burner, coolers, recuperator, turbomachinery…) and 10 internal reports, given by E.V.O in the frame of the European project HTR-E

Unique opportunity to validate CATHARE code on a large-scale helium Brayton cycle.

Proposed as benchmark test cases in the frame of the European project RAPHAEL


Available data Available data OberhausenOberhausen II II

Data corresponding to four nominal states :

The design specification established in 1972 (Bammert & Deuster, 1974): 50MW(e) and 33% of efficiency were expected

The normal operating conditions of the real installation between 1974 and 1988 (Bammert et al., 1983), with a maximum power obtained of 30MW(e) (22% of efficiency).

Two partial load conditions at 20MW(e) and 13 MW(e)

Data corresponding to transients :

Load following, Loss of load (under progress)


OberhausenOberhausen II : Cycle presentationII : Cycle presentation

Gear Box

Burner

HP Turbine

LP Turbine

LPC

Recuperator

Precooler

Intercooler

HPC

closed-loop primary system and two open-loop secondary coolant system

gaseous coolant : HELIUM

compressors and HP turbine run at a speed of 5500 rpm and the LP turbine at 3000 rpm.

Cooling of the first stages of HP Turbine

Thermal losses all along the circuit Leakages, mainly located on HP side.

Helium re-injection at Precooler inlet.

Max pressure : 28.7bMax temperature : 750°C

Power expected : 50MW(e)30MW(e) reached

Efficiency expected : 33% 22% reached


OberhausenOberhausen II : Design data and full loadII : Design data and full loadParameter Design Measured Estimated impact on generator

output power

HP Turbine efficiency 88.3 % 82.3 % - 3.9 MW

LP Turbine efficiency 90.0 % 85.6 % - 2.4 MW

HP Compressor efficiency 85.5 % 77.9 % - 4.0 MW

LP Compressor efficiency 87.0 % 82.6 % - 1.3 MW

Pressure losses 10.25 % 12.79 % - 2.6 MW

Leakage + Cooling 1.78 kg/s 7.53 kg/s - 5.3 MW

Turbo-machine input temperature (HPT/LPC/HPC) 750/25/25 °C 743.6/24.3/23.8 °C - 0.4 MW

∆T across recuperator3.0 °C 8.7 °C - 0.3 MW

Total - 20.2 MW


CathareCathare ModelingModeling

HP Turbine

LP Turbine

HP Compressor

LP Compressor

Intercooler

Burner

Recuperator

Precooler

Helium tanks for load following

The whole circuit is modeled using 1D and 0D modules

Cooling of the first stages of the HP turbines is modeled by a pipe and a valve

Leakages and re-injections are modeled by punctual sources and sinks of mass

A specific motion equation is solved for the turbomachinery

Helium tanks used for load following are represented.

~900 meshes for the whole facility


Load following transientLoad following transient

Load Following Transient :

10.75 b2.64 b

16.6 b

Scenario :

• t = 0s : beginning of the transient• t = 231s : opening of the valves joining the outlet of the HP compressor and the tank T1. • t = 515s : closing of the valves joining the outlet of the HP compressor and the tank T1• t = 597s: opening of the valves joining the outlet of the HP compressor and the tank T2.• t = 1170s : closing of the valves joining the outlet of the HP compressor and the tank T2• t = 1200s: end of the transient.


Load following transient Load following transient -- ResultsResults

Pressure in Tank 1

6

8

10

12

14

16

0 200 400 600 800 1000 1200

Time (s)

Pres

sure

(bar

)

E.V.O Data

CathareCalculation

Pressure in Tank 2

02468

101214

0 200 400 600 800 1000 1200

Time (s)

Pres

sure

(bar

)

E.V.O Data

CathareCalculation

HP Compressor Outlet Pressure

89

101112131415161718

0 200 400 600 800 1000 1200 1400

Time (s)

Pres

sure

(bar

)

E.V.O Data

Cathare Calculation


Load following transient Load following transient -- ResultsResults

LP Compressor Outlet Pressure

6

6.57

7.58

8.5

99.5

10

0 200 400 600 800 1000 1200

Time (s)

Pres

sure

(bar

)

E.V.O Data

CathareCalculation

HP Turbine Outlet Pressure

66.5

77.5

88.5

99.510

0 200 400 600 800 1000 1200Time (s)

Pres

sure

(bar

)

E.V.O Data

CathareCalculation

HP Turbine Inlet Pressure

8

9

10

11

12

13

14

15

16

0 200 400 600 800 1000 1200 1400

Te m p s ( s )

P ETHP EVO

P ETHP Ca t ha re

Mass Flow Rate in primary loop

3537394143454749515355

0 200 400 600 800 1000 1200Time(s)

Mas

s Fl

ow R

ate

(kg/

s)

E.V.O Data

CathareCalculation

Maximum differences between Cathare and E.V.O : 0.5 bar for pressure, 2kg.s-1 for mass flow rate


Introduction on Introduction on OberhausenOberhausen I facilityI facility

(f) (b)

(a)

(d)

(e)

(g)

(h)

~(c)

P = 32.4b T = 712.5°C

P = 8.3b T = 448°C

P = 8.8b T = 130°C

P = 7.8b T = 30°C

P = 18.1b T = 130°C

P = 17.7b T = 30°C

P = 34.7b T = 106°C

P = 36b T = 419°C

129.3kg.s-1

130.7kg.s-1

131.1kg.s-1

130.9kg.s-1

closed-loop primary system and two open-loop secondary coolant systemgaseous coolant : Air

Cooling of the first stages of HP TurbineLeakages, mainly located on HP side. Air re-injection at Precooler inlet.

Power expected : 13.75MW(e)

Bypass valve


Available data on Available data on OberhausenOberhausen I facility I facility

two nominal states :

The normal operating conditions of the real installation between 1974 and 1988 (Bammert et al., 1983), with a maximum power obtained of 13.75MW(e)

A partial load conditions 10 MW(e)

three transients :

An aperture and closure of the turbo-machine by-pass valveLoss of electrical load without turbo-machine tripAn house load rejection without turbo-machine trip


Transient : Aperture and closure of the turboTransient : Aperture and closure of the turbo--machine bymachine by--pass valvepass valve

Scénario :

It consists in a slow manual opening of the turbo-machine by-pass valve and then a manual closing of this valve.

By-pass valve opening rate

0

0.05

0.1

0.15

0.2

0.25

0 10 20 30 40 50 60 70Time (s)

Ope

ning

rate

(%)

CATHARE CalculationE.V.O Data

Mass flow rate over turbo-machine bypass line

0

5

10

15

20

25

30

35

40

45

0 10 20 30 40 50 60 70Time (s)

Mas

s flo

w ra

te (k

g/s)

CATHARE CalculationE.V.O Data



Pressure in the primary loop

579

11131517192123252729313335

0 10 20 30 40 50 60 70Time (s)

Pres

sure

(bar

)

CHP Inlet CATHARECHP Inlet E.V.O DataTurbine Inlet CATHARETurbine Inlet E.V.O DataTurbine Outlet CATHARETurbine Outlet E.V.O Data

Temperature in primary loop

0

100

200

300

400

500

600

0 10 20 30 40 50 60 70Time (s)

Tem

péra

ture

s (°

C)

Turbine Outlet CATHARETurbine Outlet E.V.O DataCHP Outlet CATHARECHP Outlet E.V.O DataPrecooler Inlet CATHAREPrecooler Inlet E.V.O Data

Maximum difference between Cathare calculation and E.V.O data is about 2barfor pressure and 20°C for temperature

Main explanation : The magnitude of the pressure evolution tightly depends on the distribution of volume between HP side and LP side. This distribution is probably not so good in the CATHARE modelling due to the lack of data about piping and volumes



Electrical Power available on the shaft

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60 70Time (s)

Elec

tric

al p

ower

(MW

)CATHARE CalculationE.V.O Data

Maximum difference between Cathare Calculation and E.V.O data :~1.5 MW


Transient : Loss of load without turboTransient : Loss of load without turbo--machinery tripmachinery trip

-> Brutal disconnection of the generator, leading to a brutal fall of the power extracted on the shaft from 10MWe to 0.

-> An opening of the by-pass valve to limit the turbo-machine over speed

An appropriate regulation of the by-pass valve opening permits to recover the nominal speed of the shaft.

Turbo-machine by-pass valve opening rate

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 5 10 15 20 25Time (s)

Ope

ning

rate

(%)

E.V.O dataCATHARE Calculation

Mass flow rate over turbo-machine bypass line

0

50

100

150

200

250

300

0 5 10 15 20 25Time (s)

Mas

s flo

w ra

te (k

g/s)

E.V.O DataCATHARE Calculation



Turbo-machine speed

2700

2800

2900

3000

3100

3200

3300

0 5 10 15 20 25Time (s)

Rot

atio

n Sp

eed

(rd/

min

) E.V.O DataCATHARE Calculation

The amplitude and frequency of the speed variation are well predicted and the nominal state is recovered at the same time as E.V.O data

Max difference between E.V.O data and Cathare Calculation : ~100 round/min



The order of magnitude of the evolutions are globally good

Max difference between Cathare calculation and E.V.O data ~ 2bar for pressure and 20°C for temperature

Pressure in primary loop

0

5

10

15

20

25

30

35

0 5 10 15 20 25Time (s)

Pres

sure

(bar

)

CBP Inlet E.V.O DataCBP Inlet CATHARECHP Outlet E.V.O DataCHP Outlet CATHARECHP Inlet E.V.O DataCHP inlet CATHARE

Temperatures in primary loop

0

100

200

300

400

500

600

0 5 10 15 20 25Time (s)

Tem

pera

ture

s (°

C)

Turbine Outlet E.V.O DataTurbine Outlet CATHAREBurner Inlet E.V.O DataBurner Inlet CATHARECBP Inlet E.V.O DataCBP Inlet CATHAREPrecooler Inlet E.V.O DataPrecooler Inlet CATHARE


ConclusionConclusion

•• The study highlights some interesting feedback on The study highlights some interesting feedback on OberhausenOberhausen I and II I and II facilities :facilities :o Influence of some critical parameters : leakages, cooling, repartition of volume

between HP side and LP side…o Necessity to well represent these phenomenon in Cathare simulation.

•• These calculations are a first step in the validation of These calculations are a first step in the validation of CathareCathare applied to applied to GCR : GCR : o Oberhausen I and II are unique opportunities to compare Cathare calculation with

large scale helium and air Brayton cycles. o Nominal states for the design cycle and for three operating cycles are well

predicted.o Load following, aperture and closure of by-pass valve and loss of load transient

calculation give results in good agreement with experimental data.

•• PerspectivesPerspectiveso Calculation of the Loss of load transient for Oberhausen IIo Find and collect additional data (more detailed geometrical data, other transient

measurements) through the European project Raphael.

Validation of the CATHARE2 code against experimental data from Brayton-cycle plants

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