EUROTRANS – DM1 Analysis of Protected Accidental Transients in EFIT with RELAP5 Code

WP 1.5 Progress MeetingENEA – Bologna, Italy, May 28-30, 2008

ENTE PERLE NUOVE TECNOLOGIE,L’ENERGIA E L ’AMBIENTE


FPN-FISNUC / Bologna

EUROTRANS – DM1

Analysis of Protected Accidental Transients in EFIT with RELAP5 Code

G. Bandini, P. Meloni, M. Polidori

2



EUROTRANS DM1 – WP 1.5 Progress Meeting, Bologna, May 28-30, 2008

Update of RELAP5 Model

22

112

173

UPPER PLENUMbranch120

110

LOWER PLENUMbranch 100

176 (177/8/9)175

6282

171

branch 160

Jun 106

InnerAverage

151

152153154

111

InnerHot

210211

OuterHot

OuterAverage

pipe281

282/3/4

SGswater side

Pumps113

DHR

Pth

pumpsplenumbranch

121

SGsPb side

SGsPb side

pipe381

382/3/4

annulus181

182/3/4

311310109

CoreMiddle

AverageMiddle

Hot

By pass&

reflector

branch

branchbranch

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03 010204050607

07 06 05 04 0203 01

01

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Jun 63Jun 23 Jun 83

Jun 104 Jun 114

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112

170


110


176 (177/8/9)175

6282

171

branch 160

Jun 106

InnerAverage

152153154

111

InnerHot

210211

OuterHot

OuterAverage

pipe281

282/3/4

SGswater side

113

DHR

Pth

SGsPb side

pipe381

382/3/4

annulus181

182/3/4

311310109

CoreMiddle

AverageMiddle

Hot

By pass&

reflector

branch

branchbranch

branch

03 010204050607

07 06 05 04 0203 01

01 0101

02

Jun 63Jun 23 Jun 83

Jun 104 Jun 114

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01 02

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0108

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Tar

get

lo

op

102

161

Jun 105

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102

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Jun 105

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22

112

173


110


176 (177/8/9)175

6282

171

branch 160

Jun 106

InnerAverage

151

152153154

111

InnerHot

210211

OuterHot

OuterAverage

pipe281

282/3/4

SGswater side

Pumps113

DHR

Pth

pumpsplenumbranch

121

SGsPb side

SGsPb side

pipe381

382/3/4

annulus181

182/3/4

311310109

CoreMiddle

AverageMiddle

Hot

By pass&

reflector

branch

branchbranch

branch

03 010204050607

07 06 05 04 0203 01

01

01 0101

02

Jun 63Jun 23 Jun 83

Jun 104 Jun 114

01

05

06

01 02

22

112

170


110


176 (177/8/9)175

6282

171

branch 160

Jun 106

InnerAverage

152153154

111

InnerHot

210211

OuterHot

OuterAverage

pipe281

282/3/4

SGswater side

113

DHR

Pth

SGsPb side

pipe381

382/3/4

annulus181

182/3/4

311310109

CoreMiddle

AverageMiddle

Hot

By pass&

reflector

branch

branchbranch

branch

03 010204050607

07 06 05 04 0203 01

01 0101

02

Jun 63Jun 23 Jun 83

Jun 104 Jun 114

01

05

06

01 02

0101

01080108

108

Tar

get

lo

op

102

161

Jun 105

08

102

161

Jun 105

08

RELAP5 Nodalization Scheme

Primary system layout by D1.26 of ANSALDO (November 2007)

Primary circuit pressure drops according to new ANSALDO data

Gagging at core inlet according to SIM-ADS

DHR modeling data according to detailed ANSALDO analysis

3




PRIMARY SYSTEM: Total power = 395.2 MW Lead mass flowrate = 33243 kg/s Lead temperature = 400 / 480 C Total primary circuit pressure drop = 1.37 bar

(core = 0.7 bar, SG = 0.4 bar, Pump = 0.27 bar )

Total mass of lead = 5880 tons (ANSALDO data = 5954 tons)

Lead free levels = 1.085 / 1.495 / 0.448 (ANSALDO data = 1.085 / 1.473 / 0.406)

SECONDARY SYSTEM: Feedwater flow rate (4 SGs) = 244.4 kg/s, Temperature = 335 C Steam pressure = 140 bar Steam temperature = 452 C (Superheating of 115 C)

Main EFIT Parameters

4




RELAP5 Steady-State Calculation

Maximum temperature

(°C)

Inner zone (Fax = 1.14)

Middle zone (Fax = 1.16)

Outer zone (Fax = 1.17)

Hot FA 1/42 Fr = 1.12

Average FA 41/42

Hot FA 1/66 Fr = 1.13

Average FA 65/66

Hot FA 1/72

Fr = 1.24

Average FA 71/72

Central fuel 1251 1151 1329 1214 1284 1093

Surface fuel 870 818 858 804 816 734

Internal clad 539 524 535 519 534 508

External clad 527 513 524 510 525 501

Lead 494 484 494 483 502 482

Parameter Inner zone

Middle zone

Outer zone

Reflector Target Total

Thermal power (MW) 96 142.3 140.5 5.2 11.2 395.2

Lead mass flow rate (kg/s) 7678 11486 11445 1127 1506 33243

By-pass

outlet

Target

outlet

- -

- -

- -

- -

431 450

5




Transients to be Analyzed by ENEA (1)

TRANSIENT TO BE ANALYZED FOR PB-COOLED EFIT DESIGN

Number Transient Description BOC EOCENEA

RELAP5 (X-S) RELAP/PARCS (X-C)

SIMMER

PROTECTED TRANSIENTS

P-1 PLOFTotal loss of forced

circulation in primary system (4 pumps)

x xX-S (reactor trip on

pump speed threshold)

P-1.1 PLOF-1Loss of 1 out of 4

primary pumps (pump rotor seizure)


core outlet temp. threshold)

P-4 PLOHTotal loss of secondary

loops (4 loops)x x

X-S (reactor trip on core outlet temp.

threshold)

P-4.1 PLOH-1loss of 1 out of 4 secondary loops


core outlet temp. threshold)

P-5PLOF + PLOH

(station blackout)

Total loss of forced circulation and secondary loops

x xX-S (reactor trip

at 0 s)X (reactor trip at 0 s)

P-10Spurious beam

tripbeam trip for 1,2,3 …..

10 s intervalsx x X-C

P-11 SGTRSteam generator tube rupture (1 to 5 tubes)

xX (reactor trip at 0 s)

6




Analysis of Protected Transients

PLOF: Total loss of forced circulation (4 pumps)

PLOF-1: Stop of 1 pump (pump rotor seizure)

PLOH: Total Loss of Heat Sink

PLOH-1: Loss of feedwater to 1 steam Generator

PLOF + PLOH (Station blackout): Total loss of forced circulation and secondary loops with beam trip

PTOP: Overpower Transient (+10%)

REACTOR TRIP (Proton beam switch-off):

Core outlet temperature > 515 - 525 C (> DTass-max x 1.2 + 400 C)

Pump speed close to 0 (in case of total loss of forced circulation)

Delay in reactor trip = 2 s

7




Safety Limits

According to PDS-XADS safety analysis: Lead temperature always below 1500 C

Clad temperature below 550 C during normal operation

Clad temperature in the range:

550 – 600 C for less than 600 s,

600 – 650 C for less than 180 s,

in transient conditions

Vessel wall temperature below 450 C

8




Sensitivity Study on Reactor Trip Set-Points (1)

Accident Beam trip set-point Beam trip delay (s)

Beam Trip (s)

Maximum Tclad (s)

Maximum Tclad (C)

PLOF-0 (4 pumps)

Tlead ave-chan > 525 C (steady = 482 C)

2 12 12 845

PLOF (4 pumps)


0 10 11.4 821

PLOF-1a (4 pumps)

Tlead hot-chan > 525 C (steady = 502 C)

2 6.8 11.2 742

PLOF-1 (4 pumps)


0 4.8 10.8 683

PLOF-2 (4 pumps)


0 3.4 10.8 645

PLOF-3 (4 pumps)

Pump speed close to 0 2 2.8 10.8 630

PLOF-1p-0 (1 pump)


2 88 88 584

PLOF-1p (1 pump)


0 86 86 584

PLOF-1p-1a (1 pump)


2 10 10 566

PLOF-1p-1 (1 pump)


0 8 8 561

9




Sensitivity Study on Reactor Trip Set-Points (2)

Accident Beam trip set-point Beam trip delay (s)

Beam Trip (s)

Maximum Tclad (s)

Maximum Tclad (C)

PLOH-0 (4 SGs)


2 76 76 576

PLOH (4 SGs)


0 74 74 574

PLOH-1a (4 SGs)


2 53 53 556

PLOH-1 (4 SGs)


0 51 51 554

PLOH-1sg-0 (1 SGs)


2 340 340 573

PLOH-1sg (1 SGs)


0 338 338 573

PLOH-1sg-1a (1 SGs)


2 146 146 553

PLOH-1sg-1 (1 SGs)


0 144 144 553

PLOHS-0 (St-blackout)

Station-blackout at 0 s 0 0 11.4 566

10




PLOF + PLOH – Station Blackout (1)

Core Mass Flow Rate

-10000

0

10000

20000

30000

40000

-10 0 10 20 30 40 50Time (s)

Flo

w r

ate

(kg/

s)

mflowj 100080000

Lead Free Levels

0.4

0.6

0.8

1.0

1.2

1.4

1.6

-10 0 10 20 30 40 50Time (s)

Leve

l (m

)

cntrlvar 50

cntrlvar 51

cntrlvar 56

Vessel

Pump

Core

Lead free level fluctuations and stabilization after primary pump stop

Core mass flow rate reduces down to 0 in the initial transient

11




Pump Angular Velocity

-20

-10

0

10

20

-10 0 10 20 30 40 50Time (s)

Vel

ocity

(ra

d/s)

pmpvel 910

Pump Mass Flow Rate

-6000

-3000

0

3000

6000

9000

-10 0 10 20 30 40 50Time (s)

Flo

w r

ate

(kg/

s)

mflowj 910010000


Very fast pump coastdown due to low initial pump velocity and low moment of inertia

Pump velocity and mass flow rate reverse in the initial transient following lead free level stabilization

12




Max Clad Temperature

400

450

500

550

600

-10 0 10 20 30 40 50Time (s)

Tem

pera

ture

(C

)

httemp 111101216

httemp 211101216

httemp 311101216

Max Lead Temperature

400

450

500

550

600

-10 0 10 20 30 40 50Time (s)

Tem

pera

ture

(C

)

tempf 111180000

tempf 211180000

tempf 311180000

Outer coreMiddle coreInner core



Maximum lead and clad peak temperature in hot channel of outer core zone

Maximum clad temperature is well below safety limits for transient conditions

13




Core and DHR Power

0.0E+00

5.0E+06

1.0E+07

1.5E+07

2.0E+07

2.5E+07

3.0E+07

0 1000 2000 3000 4000 5000Time (s)

Pow

er (

W)

cntrlvar 116

cntrlvar 131

Core and DHR Mass Flow Rates

0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000Time (s)

Flo

w r

ate

(kg/

s)

mflowj 100080000

mflowj 175010000

DHR

Core

DHR

Core


Natural circulation in the primary circuit and through the DHR stabilizes in about 500 s

Core decay power is totally removed by the DHR after about 1000 s

14




Lead Temperature

400

420

440

460

480

500

0 2000 4000 6000 8000 10000Time (s)

Tem

pera

ture

(C

)

tempf 100010000

tempf 120010000

tempf 175010000

tempf 113090000

DHR outCore in

DHR in

Core out (average)

Max Vessel Wall Temperature

400

410

420

430

440

450

0 2000 4000 6000 8000 10000Time (s)

Tem

pera

ture

(C

)

httemp 100100401


Primary hot lead temperature at core outlet stabilizes at about 453 C after 10000 s

Vessel wall temperature reaches a maximum of 435 C after 5000 s

15




PLOF – Total Loss of Forced Circulation (1)Pump Angular Velocity

-20

-10

0

10

20

-10 0 10 20 30 40 50Time (s)

Vel

ocity

(ra

d/s)

pmpvel 910

Core Mass Flow Rate

0

10000

20000

30000

40000

-10 0 10 20 30 40 50

Time (s)F

low

rat

e (k

g/s)

mflowj 100080000

Pump speed = 0 after 0.8 s Reactor trip with 2 s delay at 2.8 s

Initial core mass flow rate undershoot and fluctuations after primary pump stop

16




PLOF – Total Loss of Forced Circulation (2)Max Lead Temperature

400

450

500

550

600

650

-10 0 10 20 30 40 50Time (s)

Tem

pera

ture

(C

)

tempf 111180000

tempf 211180000

tempf 311180000


400

450

500

550

600

650

-10 0 10 20 30 40 50Time (s)

Tem

pera

ture

(C

)

httemp 111101216

httemp 211101216

httemp 311101216



Enhanced lead and clad temperature peaks after reactor trip at 2.8 s

Maximum clad temperature (hot channel of outer core) is below safety limits for transient conditions (less then 180 s in the range 600 – 650 C)

17




PLOF-1 – Stop of 1 Primary Pump (1)Pump Angular Velocity

0

5

10

15

20

25

-10 0 10 20 30 40 50Time (s)

Vel

ocity

(ra

d/s)

pmpvel 910

pmpvel 920

Lead Free Levels

0.4

0.6

0.8

1.0

1.2

1.4

1.6

-10 0 10 20 30 40 50Time (s)

Leve

l (m

)

cntrlvar 50

cntrlvar 51

cntrlvar 52

cntrlvar 56Vessel

Running pumps

Core

Stopped pump

Running pumps

Stopped pump

No reverse pump velocity is allowed after pump stop

Lead free level above stopped pump lies between vessel and core free levels after pump stop (reverse flow from vessel to core zone)

18




PLOF-1 – Stop of 1 Primary Pump (2)Pump Mass Flow Rate

-12000

-8000

-4000

0

4000

8000

12000

-10 0 10 20 30 40 50Time (s)

Flo

w r

ate

(kg/

s)

mflowj 910010000

mflowj 920010000

Core Mass Flow Rate

0

10000

20000

30000

40000

-10 0 10 20 30 40 50

Time (s)F

low

rat

e (k

g/s)

mflowj 100080000

Running pumps

Stopped pump

Slight increase in running pump mass flow rate and reverse flow through stopped pump

Core mass flow rate reduces by about 30%

19




PLOF-1 – Stop of 1 Primary Pump (3)Core In-Out Lead Temperature

325

375

425

475

525

575

-50 0 50 100 150 200 250 300Time (s)

Tem

pera

ture

(C

)

tempf 111180000

tempf 211180000

tempf 311180000

tempf 110180000

tempf 210180000

tempf 310180000

tempf 100010000

Core and SGs Extracted Power

0.E+00

1.E+08

2.E+08

3.E+08

4.E+08

5.E+08

-50 0 50 100 150 200 250 300Time (s)

Pow

er (

W)

cntrlvar 280

cntrlvar 116Core

SGs

Trip set-point

Reactor trip at 10 s (on hot channels T > trip set-point) or 86 s (on average channels T > trip set-point)

SG removal power decreases by about 12% after pump stop due to primary circuit mass flow rate reduction

Reactor trip onHot–average T-channel

20




PLOF-1 – Stop of 1 Primary Pump (4)Max Clad Temperature

350

400

450

500

550

600

-50 0 50 100 150 200 250 300Time (s)

Tem

pera

ture

(C

)

httemp 111101216

httemp 211101216

httemp 311101216

Max Fuel Temperature

400

600

800

1000

1200

1400

-50 0 50 100 150 200 250 300Time (s)

Tem

pera

ture

(C

)

httemp 111100701

httemp 211100701

httemp 311100701



Clad temperature is kept below safety limits for transient conditions (less than 600 s in the range 550 – 600 C)

Maximum fuel temperature is below acceptable value

21




PLOH – Total Loss of Heat Sink (1)Core In-Out Lead Temperature

325

375

425

475

525

575

-50 0 50 100 150 200 250 300Time (s)

Tem

pera

ture

(C

)

tempf 111180000

tempf 211180000

tempf 311180000

tempf 110180000

tempf 210180000

tempf 310180000

tempf 100010000


350

400

450

500

550

600

-50 0 50 100 150 200 250 300Time (s)

Tem

pera

ture

(C

)

httemp 111101216

httemp 211101216

httemp 311101216

Trip set-point



Clad temperature is kept well below safety limits for transient conditions


22




PLOH – Total Loss of Heat Sink (2)Core and DHR Power

0.0E+00

5.0E+06

1.0E+07

1.5E+07

2.0E+07

2.5E+07

3.0E+07

0 2000 4000 6000 8000 10000Time (s)

Pow

er (

W)

cntrlvar 116

cntrlvar 131

DHR

Core

DHR mass flow rate stabilizes at approximately 3500 kg/s after about 3 hours

DHR system reaches maximum performances (about 20 MW for 3 units) after about 400 s

DHR Mass Flow Rate

0

1000

2000

3000

4000

5000

6000

0 2000 4000 6000 8000 10000Time (s)

Flo

w r

ate

(kg/

s)

mflowj 175020000

23




PLOH – Total Loss of Heat Sink (3)

Lead Temperature

400

420

440

460

480

500

0 2000 4000 6000 8000 10000Time (s)

Tem

pera

ture

(C

)

tempf 100010000

tempf 120010000

tempf 175010000

tempf 113090000

Max Vessel Wall Temperature

400

410

420

430

440

450

0 2000 4000 6000 8000 10000Time (s)

Tem

pera

ture

(C

)

httemp 100100401

DHR inCore outCore in

DHR out

Primary lead temperature stabilizes at about 435 C after 10000 s

Maximum vessel wall temperature around 3000 s is below safety limit (450 C)

24




Core and SGs Extracted Power

0.E+00

1.E+08

2.E+08

3.E+08

4.E+08

5.E+08

-200 0 200 400 600 800 1000 1200Time (s)

Pow

er (

W)

cntrlvar 280

cntrlvar 116

PLOH-1 – Loss of Feedwater to 1 SG (1)Core In-Out Lead Temperature

325

375

425

475

525

575

-200 0 200 400 600 800 1000 1200Time (s)

Tem

pera

ture

(C

)

tempf 111180000

tempf 211180000

tempf 311180000

tempf 110180000

tempf 210180000

tempf 310180000

tempf 100010000

Core

SGs


Trip set-point


SGs removal power reduces down to 75% at transient initiation

25




PLOH-1 – Loss of Feedwater to 1 SG (2)

Clad temperature is kept below safety limits for transient conditions (less than 600 s in the range 550 – 600 C)

Maximum fuel temperature is below acceptable value


350

400

450

500

550

600

-200 0 200 400 600 800 1000 1200Time (s)

Tem

pera

ture

(C

)

httemp 111101216

httemp 211101216

httemp 311101216


400

600

800

1000

1200

1400

-200 0 200 400 600 800 1000 1200Time (s)

Tem

pera

ture

(C

)

httemp 111100701

httemp 211100701

httemp 311100701



26




PTOP – Overpower Transient (+10%)

Max Lead Temperature



Core and SGs Power

27




CONCLUSIONS

Core decay heat removal by natural circulation through the DHR system is efficient in all investigated scenarios with total loss of heat removal by the secondary loops

Core and vessel structures temperatures are kept well below safety limits in all investigated protected scenarios even under the most conservative assumptions on reactor trip occurrence based on core outlet temperature measurements and trip set-point

Reactor trip on low pump rotational speed signal is needed in case of total loss of forced circulation in the primary circuit to keep clad temperature peak within acceptable values

Documents

EUROTRANS – DM1 Analysis of Protected Accidental Transients in EFIT with RELAP5 Code