LEADER, Task 5.5 ETDR Transient Analyses with

SPECTRA Code

LEADER Project

JRC, Petten, February 26, 2013

M.M. Stempniewiczstempniewicz@nrg.eu

NRG-22694/13.118781

Content

• SPECTRA Model 3- SPECTRA/RELAP Model and Steady State Results 5- SPECTRA Model - Heat Transfer Correlations 17- SPECTRA Model - Reactivity Feedback 18- SPECTRA Model - SCRAM Signals 20

• Analyzed Transients 21- TR-4, Reactivity insertion, 250 pcm in 2 s

22- T-DEC1, Loss of all primary pumps, reactor trip fails 27- T-DEC5, Partial blockage of hottest fuel assembly 32

• Conclusions 34

• References 35

• Appendix A: Liquid Lead Properties 36

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SPECTRA Model

• A model of the ETDR, ALFRED reactor design [1] was prepared for the SPECTRA code [2].

• Nodalization of the SPECTRA model was assumed very similar to the nodalization applied for RELAP analyses at ENEA [3]. Some simplifications in the number of nodes were made whenever possible.

• The model consists of:- Primary system (liquid lead)- Steam Generators and secondary system loops (8 steam/water loops)- Isolation Condensers

• The EOC conditions were assumed. For modelling the gap, fuel swelling of 0.149 mm was assumed (initial gap size 0.150 mm), following RELAP model.

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SPECTRA Model

• The model was prepared such that the 8 loops can be combined into one or split into several (up to 8) loops, if needed.

- This is done using # and $, for example:* Multiplicity

102#21 $.0 * No. of loops

- Automatic replacement of # → loop No. and $ → number of identical loops, creates the desired model version.

• The model was tested by running steady state calculations and comparing results with the resuts obtained at ENEA using RELAP5 [3].

• Comparison of SPECTRA and RELAP results is given below. A good agreement is obtained.

4NRG-22694/13.118781

Fuel ElementsSPECTRA Model and Steady State Results

5NRG-22694/13.118781

Fuel ElementsRELAP Model and Steady State Results

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Reactor CoreSPECTRA Model and Steady State Results

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Reactor CoreRELAP Model and Steady State Results

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Primary SystemSPECTRA Model and Steady State Results

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Primary SystemRELAP Model and Steady State Results

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Steam GeneratorSPECTRA Model and Steady State Results

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Steam GeneratorRELAP Model and Steady State Results

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Secondary LoopSPECTRA Model and Steady State Results

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Secondary LoopRELAP Model and Steady State Results

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Isolation CondenserSPECTRA Model and Steady State Results

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Isolation CondenserRELAP Model and Steady State Results

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SPECTRA Model - Heat Transfer Coefficient Correlations

• If a liquid metal is to be applied in SPECTRA calculations, the HTC correlations must be defined in input. The following correlations have been used:

- Ushakov correlation - reference [4]:

here x = P/D

- Reactor Core: Ushakov, with P/D=1.32- Steam Generator: Ushakov, with P/D=1.4182

17NRG-22694/13.118781

)19.056.0(213

041.02055.7 xeP

xxx Nu

SPECTRA Model - Reactivity Feedback

• The reactivity feedback includes:

- Doppler reactivity effect:

- Axial fuel expansion:

- Coolant density:

- Cladding expansion:

- Wrapper expansion:

- Diagrid expansion:

- Pad expansion:

- Control rod:

)/ln( 0,fuelfuelDD TTKR

)( 0,coolcoolcoolcool TTcR

)( 0,cladcladcladclad TTcR

)( 0,diadiadiadia TTcR

)( 0,padpadpadpad TTcR

)( 0,rodrodrodrod TTcR

18NRG-22694/13.118781

)( 0,exp fuelfuelfuelfuel TTcR

)( 0,wrapwrapwrapwrap TTcR

SPECTRA Model - Reactivity Feedback

• The constants in the reactivity feedback are:

Component

(slides 8, 9)

- Doppler reactivity effect: KD = -566.0 SC-044/-055

- Axial fuel expansion: cfuel = -0.155 pcm/K SC-044/-055

- Coolant density: ccool = -0.268 pcm/K CV-044/-055

- Cladding expansion: cclad = +0.050 pcm/K SC-044/-055

- Wrapper expansion: cwrap = +0.026 pcm/K SC-064/-075

- Diagrid expansion: cdia = -0.152 pcm/K CV-020

- Pad expansion: cpad = -0.430 pcm/K CV-057

- Control rod, prompt: crod = -0.218 pcm/K CV-021

- Control rod, delayed: neglected

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SPECTRA Model - SCRAM Signals

• SCRAM signals incorporated into the model:

• Neutron flux > 120%• Average assembly ΔT > 1.2×nominal• Hot assembly ΔT > 1.2×nominal• Low primary floe W < 90%

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Analyzed Transients

• Transients:1. TR-4 Reactivity insertion, 250 pcm in 2 s.

Model: 8 identical loops combined into one, no IC

2. TO-1, TO-3Loss of FW pre-heater on 1 loop (TO-3: +all primary pumps stop)

Model: 1+3+4 identical loops, IC working on 4 loops

3. TO-4, TO-620% increase of FW flow (TO-6: +all primary pumps stop)

Model: 8 identical loops combined into one, no IC

4. T-DEC1 Loss of all primary pumps. Reactor trip fails.

Model: 8 identical loops combined into one, no IC

5. T-DEC3 Loss of SCS. Reactor trip fails.

Model: 3+5 identical loops, IC working on 3 loops

6. T-DEC-4 Loss of off-site power. Reactor trip fails.

Model: 3+5 identical loops, IC working on 3 loops

7. T-DEC5 Partial blockage of hottest assembly.

Model: 8 identical loops combined into one, no IC

8. T-DEC6 SCS failure

Model: 8 identical loops combined into one, no IC

green: done

red: still to be done

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TR-4 Reactivity insertion, 250 pcm in 2 s

• Scenario: - Reactivity of 250 pcm (0.8375 $) is inserted in 2 seconds.- Reactor trip (SCRAM signal) is disabled.

• Core power reaches 970 MW and decreases to about 500 MW. Corresponding peak in RELAP5 is 870 MW, with decrease to about 450 MW.

Reactor power, TR-4, SPECTRA Reactor power, TR-4, RELAP5 [3]

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0

200

400

600

800

1000

0 5 10 15 20 25 30

Pow

er (

MW

)

Time (s)

Core power

ETDR, ALFRED, SPECTRA

CF-900-Valu-0000 f(x)

Time302520151050

Tot

al c

ore

pow

er, [

MW

]

1,000

800

600

400

200

0

TR-4 Reactivity insertion, 250 pcm in 2 s

• Long term core power behavior:• After the initial transient the core power slowly reduces and stabilizes slightly below 400

MW, with the same power removed by SG-s. • SG power increases slowly due to temperature increase at SG inlet on the primary side.

Steam outlet temperature increases on the secondary side (constant FW flow rate).

Reactor and SG power, TR-4, SPECTRA Reactor and SG power, TR-4, RELAP5 [3]

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0

200

400

600

800

1000

0 300 600 900 1200 1500 1800

Pow

er (

MW

)

Time (s)

Core power

SG power

IC power

ETDR, ALFRED, SPECTRA

CF-900, reactor core CF-141, Steam Generators

Time1,8001,5001,2009006003000

Tot

al c

ore

pow

er, [

MW

]

1,000

800

600

400

200

0

TR-4 Reactivity insertion, 250 pcm in 2 s

• Fuel temperatures:• The fuel peak temperature reaches a maximum value close to 2700°C (2600°C in RELAP)

in the initial part of the transient and then slowly decreases to about 2400°C.• Maximum fuel temperature is higher in Spectra and exceeds for a short period the melting

temperature (MOX melting point ~2673°C). This is a consequence of higher peak power and the SPECTRA/RELAP difference will be investigated in the future.

Fuel temperatures, TR-4, SPECTRA Fuel temperatures, TR-4, RELAP5 [3]

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1000

1400

1800

2200

2600

3000

0 300 600 900 1200 1500 1800

Tem

per

atu

re (

°C)

Time (s)

T fuel peak

T fuel average

ETDR, ALFRED, SPECTRA

CF-110-Valu-0000, Fuel maximum RK-000-Tfue-0000, Fuel average

Time, [s]1,8001,5001,2009006003000

Tem

pera

ture

[C]

3,000

2,800

2,600

2,400

2,200

2,000

1,800

1,600

1,400

1,200

1,000

TR-4 Reactivity insertion, 250 pcm in 2 s

• Coolant temperatures:• After an initial jump of about 40 °C the core outlet temperature slowly increases following

the temperature increase at core inlet.• The maximum core outlet temperature stabilizes at about 620°C (about 600°C in RELAP).

Coolant temperatures, TR-4, SPECTRA Coolant temperatures, TR-4, RELAP5 [3]

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350

400

450

500

550

600

650

0 300 600 900 1200 1500 1800

Tem

per

atu

re (

°C)

Time (s)

T core in

T core out max

T core out ave

ETDR, ALFRED, SPECTRA

CV-020-Temp-pool, Core inletCV-017-Temp-pool, Core outlet, maximumCV-057-Temp-pool, Core outlet, average

Time, [s]1,8001,5001,2009006003000

Tem

pera

ture

[C]

650

600

550

500

450

400

350

TR-4 Reactivity insertion, 250 pcm in 2 s

• Reactivities:• The inserted reactivity is mainly counterbalanced by negative Doppler and fuel expansion

feedbacks induced by fuel temperature increase• Total reactivity reaches a maximum of about 190 pcm (175 pcm in RELAP) at 2 s and then

reduces according to negative feedbacks.

Reactivities, TR-4, SPECTRA Reactivities, TR-4, RELAP5 [3]

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-150

-100

-50

0

50

100

150

200

0 5 10 15 20 25 30

Rea

ctiv

ity (

pcm

)

Time (s)

Rea doppler

Rea fuel exp

Rea clad exp

Rea cool exp

Rea diagrid

Rea pads

Rea c.rods

Rea total

ETDR, ALFRED, SPECTRA

Total reactivity CF-901, DopplerCF-902, Fuel exp CF-903, Coolant densityCF-904, Clad exp. CF-908, Control rod

Time, [s]302520151050

Rea

ctiv

ity, [

-]

0.002

0.0015

0.001

0.0005

0

-0.0005

-0.001

-0.0015

-0.002

T-DEC1 Loss of All Primary Pumps

• Scenario: - Coastdown of all primary pumps.- The secondary circuits remain in operation in forced circulation- Reactor trip (SCRAM signal) is disabled.

• After an initial small core flow rate undershot natural circulation stabilizes in the primary circuit a little above 5000 kg/s.

Core inlet flow, T-DEC1, SPECTRA Core inlet flow, T-DEC1, RELAP5 [3]

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ETDR, ALFRED, SPECTRA

JN-059-Wtot-0000, Primary

Time, [s]1,8001,5001,2009006003000

Mas

s flo

w, [

kg/s

]

2.5E04

2.0E04

1.5E04

1.0E04

5.0E03

0

5000

10000

15000

20000

25000

0 300 600 900 1200 1500 1800

Mas

s flo

w r

ate

(kg

/s)

Time (s)

Core flow

T-DEC1 Loss of All Primary Pumps

• The core power initially reduces due to negative reactivity feedbacks and then stabilizes at about 240 MW (about 210 MW in RELAP5), in equilibrium with SG power.

• The SG power initially decreases due to reduced primary flow and then increases with the lead temperature increase at the SG inlet.

Reactor power, T-DEC1, SPECTRA Reactor power, T-DEC1, RELAP5 [3]

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0

50

100

150

200

250

300

0 300 600 900 1200 1500 1800

Pow

er (

MW

)

Time (s)

Core power

SG power

IC power

ETDR, ALFRED, SPECTRA

CF-900-Valu-0000 f(x) CF-141-Valu-0000

Time, [s]1,8001,5001,2009006003000

Pow

er [M

W]

300

250

200

150

100

50

0

T-DEC1 Loss of All Primary Pumps

• Fuel temperatures:• Peak and average fuel temperatures reduce according to the decrease of core power

level.• The maximum fuel temperature stabilizes at about 1700˚C (1400˚C in RELAP).

Fuel temperatures, TDEC1, SPECTRA Fuel temperatures, T-DEC1, RELAP5 [3]

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400

800

1200

1600

2000

0 300 600 900 1200 1500 1800

Tem

per

atu

re (

°C)

Time (s)

T fuel peak

T fuel average

ETDR, ALFRED, SPECTRA

CF-110-Valu-0000, Fuel maximum RK-000-Tfue-0000, Fuel average

Time, [s]1,8001,5001,2009006003000

Tem

pera

ture

[C]

2,000

1,600

1,200

800

400

T-DEC1 Loss of All Primary Pumps

• Coolant temperatures:• Initial lead temperature increase at core outlet max calculated value near 700°C at 15 s• Max core outlet temperature stabilizes just above 600 °C • The core inlet temperature slowly decreases and stabilizes at about 340°C

Coolant temperatures, TR-4, SPECTRA Coolant temperatures, TR-4, RELAP5 [3]

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300

350

400

450

500

550

600

650

700

0 300 600 900 1200 1500 1800

Tem

per

atu

re (

°C)

Time (s)

T core in

T core out max

T core out ave

ETDR, ALFRED, SPECTRA

CV-020-Temp-pool, Core inletCV-017-Temp-pool, Core outlet, maximumCV-057-Temp-pool, Core outlet, average

Time, [s]1,8001,5001,2009006003000

Tem

pera

ture

[C]

700

600

500

400

300

T-DEC1 Loss of All Primary Pumps

• Reactivities:• The inserted reactivity is mainly counterbalanced by negative Doppler and fuel expansion

feedbacks induced by fuel temperature increase• Total reactivity reaches a maximum of about 190 pcm (175 pcm in RELAP) at 2 s and then

reduces according to negative feedbacks.

Reactivities, TR-4, SPECTRA Reactivities, TR-4, RELAP5 [3]

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-120

-80

-40

0

40

80

120

0 300 600 900 1200 1500 1800

Rea

ctiv

ity (

pcm

)

Time (s)

Rea doppler

Rea fuel exp

Rea clad exp

Rea cool exp

Rea diagrid

Rea pads

Rea c.rods

Rea total

ETDR, ALFRED, SPECTRA

Total reactivity CF-901, DopplerCF-902, Fuel exp CF-903, Coolant densityCF-904, Clad exp. CF-908, Control rod

Time, [s]1,8001,5001,2009006003000

Rea

ctiv

ity, [

-]

0.001

0.0008

0.0006

0.0004

0.0002

0

-0.0002

-0.0004

-0.0006

-0.0008

-0.001

T-DEC5 Partial Blockage of Hottest Fuel Assembly

• Scenario: - Partial blockage of the hottest fuel assembly.- Inlet junction (JN-001, slide 7) assumed to be blocked- Blockages considered:

- 50%- 60%

- 70% Coolant temperatures, T-DEC5, SPECTRA

- 80%- 90%

- Reactor trip (SCRAM signal) is disabled.

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ETDR, T-DEC5, Blockage of Hottest Assembly

700.0

800.0

900.0

1,000.0

1,100.0

0 20 40 60 80 100

Time, [s]

Max

imum

Coo

lant

Tem

pera

ture

, [K

]

50% Blockage60% Blockage

70% Blockage80% Blockage

90% Blockage

T-DEC5 Partial Blockage of Hottest Fuel Assembly

• With 90% blockage (decrease of inlet flow area by a factor of 10, or increase of resistance factor by a factor of 100):

• maximum fuel temperature is ~2430 K, (~2160˚C)• maximum clad temperature is ~940 K, (~670˚C)• coolant exit temperature is ~1060 K (790˚C)

Fuel temperatures, T-DEC5, SPECTRA Cladding temperatures, T-DEC5, SPECTRA

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ETDR, T-DEC5, Blockage of Hottest Assembly

700.0

750.0

800.0

850.0

900.0

950.0

0 20 40 60 80 100

Time, [s]

Max

imum

Cla

ddin

g T

empe

ratu

re, [

K]

50% Blockage60% Blockage

70% Blockage80% Blockage

90% Blockage

ETDR, T-DEC5, Blockage of Hottest Assembly

2,250.0

2,300.0

2,350.0

2,400.0

2,450.0

0 20 40 60 80 100

Time, [s]

Max

imum

Fue

l Tem

pera

ture

, [K

]

50% Blockage60% Blockage

70% Blockage80% Blockage

90% Blockage

Conclusions

Results of several transients analyzed for the ETDR, ALFRED reactor design were shown and compared to the results of RELAP calculations from ENEA.

Steady state results obtained with SPECTRA and RELAP are in very good agreement.

Some discrepancies are observed for transient simulations. These discrepancies will be investigated in the future.

34NRG-22694/13.118781

References

[1] E. Bubelis, K. Mikityuk, "PLANT DATA FOR THE SAFETY ANALYSIS OF THE ETDR (ALFRED)", TEC058-2012, Revision: 0 (Draft), Issued by PSI/KIT (including contributions from ANSALDO, ENEA, EA, CEA, SRS), 30.04.2012.

[2] M.M. Stempniewicz, “SPECTRA Sophisticated Plant Evaluation Code for Thermal-Hydraulic Response Assessment, Version 3.60, August 2009, Volume 1 – Program Description, Volume 2 – User’s Guide, Volume 3 – Subroutine Description, Volume 4 - Verification and Validation”, NRG K5024/10.101640, Arnhem, April 24, 2009.

[3] G. Bandini, “Design and safety analysis of ALFRED - Accident Analyses Overview”, 3rd LEADER International Workshop, Bologna, 6-th - 7-th September.

[4] P.A. Ushakov, A.V. Zhukov, M.M. Matyukhin, “Heat transfer to liquid metals in regular arrays of fuel elements”, High Temperature, 15, pp. 868-873, 1977.

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Appendix A: Liquid Lead Properties

• If a liquid metal is to be applied in SPECTRA calculations, the properties of liquid metal must be supplied by the user. The properties of liquid lead were obtained flow:

“Handbook on Lead-bismuth Eutectic Alloy and Lead Properties, Materials Compatibility, Thermal-hydraulics and Technologies”, OECD/NEA Nuclear Science Committee. ISBN 978-92-64-99002-9, 2007

• The required properties include:- Saturation pressure

- Liquid properties, including:

- Density

- Specific heat

- Thermal conductivity

- Viscosity

- Speed of sound

- Vapor properties are not defined, i.e. sodium vapor cannot be encountered in calculations with the present model.

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Liquid Lead Properties, Psat(T), h(T)

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(a) Above: values tabulated for SPECTRA

(b) Below: source data

Liquid Lead Properties, ϱ(T), cp(T)

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(a) Above: values tabulated for SPECTRA

(b) Below: source data

Liquid Lead Properties, k(T), μ(T)

39NRG-22694/13.118781

(a) Above: values tabulated for SPECTRA

(b) Below: source data

Liquid Lead Properties, σ(T), c(T)

40NRG-22694/13.118781

(a) Above: values tabulated for SPECTRA

(b) Below: source data