eurotrans – dm1

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


EUROTRANS – DM1

RELAP5 Model Evaluation with SIMMER-III Code and Preliminary

Transient Analysis for EFIT Reactor

WP5.1 Progress MeetingKTH / Stockholm, May 22-23, 2007

P. Meloni, G. Bandini, M. Polidori

FPN-FISNUC / Bologna

EFIT Transient Analysis by ENEA

Use of SIMMER-III code for in-vessel natural circulation assessment and DHR performance evaluation

RELAP5 model evaluation and revision based on SIMMER-III results

Preliminary transient analysis (PLOHS and ULOF) with revised RELAP5 model



KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting

EFIT Design and Parameters

Primary circuit layout from ANSALDO presentation at the last EUROTRANS - DM4 Technical Review Meeting (March 2007):

Reactor core with 3 fuel zones

4 primary pumps, 8 IHXs, 4 secondary loops

4 DHR units (3 out of 4 in operation in transient analysis)

Primary circuit parameters:

Active core thermal power = 379 MW (ENEA study)

Lead mass flowrate = 31850 kg/s

Core inlet / outlet temperature = 400 / 480 C

Total pressure drop = 43 kPa (core pressure drop = 36 kPa)




Used Approach



KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting

SIMMER-III calculationPLOHS (beam trip at t = 0 s)

3 DHR in operation

Recirculation ratio at DHR outlet

RELAP5 calculationPLOHS (beam trip at t = 0 s)

3 DHR in operation

Comparison

Additional RELAP5 pressure drop coefficients to fit core and DHR natural circulation mass flow rates (SIMMER)

Comparison with ANSALDO data

RELAP5 revised model

Transient analysis with RELAP5

ULOF

PLOHS (beam and pump trip if aver. core out T > 500 C)

RELAP5 model evaluation and transient analysis

Comparison

ULOF with SIMMER-III

SIMMER-III Model of EFIT




2-D R-Z (36 x 35) Cylindrical model

Initial condition with stagnant lead and free level DH simulation

Harmonization with RELAP5 plant data and boundary conditions

No steam generator heat losses

3 out of 4 DHR units in operation (degraded conditions)

DHR heat removal based on constant oil temperature in secondary side (Tin = 405 C, Tout = 409 C)

SIMMER-III Results (Lead Temperature)




SIMMER-III Results at 3600 s (Lead Velocities)




Horizontal velocityVertical velocity

SIMMER-III ANSALDOResults at after 1 hourt = 3600 s: (P = 16 MW)

mC = 2740 kg/s

mD = 2983 kg/s 2985 Kg/s

TCi = 410.5 C

TCo = 449.1 C

TDi = 444.6 C 444 C

TDo = 407.0 C 407 C

Recirculation Ratio at DHR Outlet for RELAP5




y = mC (TDi - TDo)

(TCi - TDo)

x = y + mD - mC

y = 255 kg/s

Recirculation ratio at DHR outlet:x = 498 kg/s (17% of mD)

Simplified scheme of RELAP5 model

xy

mC

mD

TCi

TCo

TDo

TDi

TDi

TCi

TCo

TCi

TCo

SIMMER and RELAP5 Comparison at t = 3600 s




Parameter Unit SIMMER-III RELAP5

Core mass flow rate Kg/s 2740 3047

Core inlet temperature C 410.5 413.7

Core outlet temperature C 449.1 448.5

DHR mass flow rate (3 units) Kg/s 2983 3108

DHR inlet temperature C 444.6 442.7

DHR outlet temperature C 407.0 408.4

DHR removed power (3 units) MW 16.67 15.89

xy

mC

mD

TCi

TCo

TDo

TDi

TDi

TCi

TCo

TCi

TCo

Additional pressure drop coefficients in RELAP5 model to fit SIMMER-III results

RELAP5 (revised)

2737

410.5

449.2

2983

443.0

406.9

16.02

Code Result Comparison (Transient)




Core mass flow rate and temperature

0

1000

2000

3000

4000

0 1000 2000 3000 4000 5000Time (s)

Flo

w r

ate

(kg

/s)

Core flow (simmer)

Core flow (relap5)

390

410

430

450

470

490

0 1000 2000 3000 4000 5000

Time (s)T

em

pe

ratu

re (

C)

Tcore in (simmer)

Tcore out (simmer)

Tcore in (relap5)

Tcore out (relap5)

Core inlet / outlet temperature

Core mass flow rate

After the initial transient (about 2000 s) the revised RELAP5 model fit very well the SIMMER-III results





DHR mass flow rate and temperature

0

1000

2000

3000

4000

0 1000 2000 3000 4000 5000

Time (s)

Flo

w r

ate

(kg

/s)

DHR flow (simmer)

DHR flow (relap5)

390

400

410

420

430

440

450

0 1000 2000 3000 4000 5000

Time (s)T

em

pe

ratu

re (

C)

Tdhr in (simmer)

Tdhr out (simmer)

Tdhr in (relap5)

Tdhr out (relap5)

DHR mass flow rate

DHR inlet / outlet temperature

After the initial transient the revised RELAP5 model fit well the SIMMER-III results, and stable DHR operation is predicted by both codes





Core decay power

and

DHR removed power

0

5

10

15

20

25

30

0 1000 2000 3000 4000 5000Time (s)

Po

we

r (M

W)

DHR power (simmer)

DHR power (relap5)

Decay power

Preliminary Transient Analysis with RELAP5




Protected Loss of Heat Sink (PLOHS) at BOC with beam and pump trip when average outlet core temperature exceeds 500 C and DHR degraded conditions (3 out of 4)

Unprotected Loss of Flow (ULOF) at BOC with SGs full capacity and without reactivity feedback (constant core power)




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 1252 1151 1330 1215 1282 1091

Surface fuel 870 819 859 806 813 733

Internal clad 540 525 536 521 531 505

External clad 528 514 526 511 522 498

Lead 495 485 496 484 499 480

Parameter Inner zone

Middle zone

Outer zone

Reflector + by-pass

Total

Thermal power (MW) 96 142.3 140.5 0 (*) 378.8

Lead mass flow rate (kg/s) 7615 11330 11805 1106 31856

Nominal Conditions (RELAP5 steady-state)

(*) about 5 MW (not considered in this study)




PLOHS Transient Results (Relap5)

Core and DHR mass flow rate

Initial transient

About 3 hours transient

0

5000

10000

15000

20000

25000

30000

35000

0 100 200 300 400 500

Time (s)

Flo

w r

ate

(kg

/s)

Core flow

DHR flow

0

1000

2000

3000

4000

5000

6000

0 2000 4000 6000 8000 10000

Time (s)F

low

ra

te (

kg/s

)

Core flow

DHR flow

Proton beam and pump trip is assumed at 73 s (average lead temperature at core outlet > 500 K)

After some initial oscillations (free levels movements) both core and DHR mass flow rates became stable





Core and DHR power

Initial transient


0

5

10

15

20

25

30

0 2000 4000 6000 8000 10000

Time (s)P

ow

er

(MW

)

Core power

DHR power

0

50

100

150

200

250

300

350

400

0 200 400 600 800 1000

Time (s)

Po

we

r (M

W)

Core power

DHR power

The DHR system reaches full operation after about 600 s

A maximum of 20 MW power can be removed by 3 DHR units in operation)





Max lead and clad temperature

Initial transient


420

450

480

510

540

570

600

0 2000 4000 6000 8000 10000

Time (s)T

em

pe

ratu

re (

C)

Tlead (inner_hot)

Tclad (inner_hot)

420

450

480

510

540

570

600

0 100 200 300 400 500

Time (s)

Te

mp

era

ture

(C

)

Tlead (inner_hot)

Tclad (inner_hot)

Peak clad temperature reaches 585 C in the hot channel of inner core zone

Max lead and clad temperature stabilize at about 450 C after 6000 s





Max fuel temperature (hot channel)

Initial transient

400

600

800

1000

1200

1400

0 100 200 300 400 500

Time (s)

Te

mp

era

ture

(C

)

Tfuel (inner_hot)

Tfuel (middle_hot)

Tfuel (outer_hot)

400

600

800

1000

1200

1400

0 2000 4000 6000 8000 10000

Time (s)

Te

mp

era

ture

(C

)

Tfuel (inner_hot)

Tfuel (middle_hot)

Tfuel (outer_hot)


380

400

420

440

460

480

0 2000 4000 6000 8000 10000

Time (s)T

em

pe

ratu

re (

C)

Vessel temp1

Vessel temp2

Vessel temp3

Max vessel wall temperature

The vessel wall temperature reaches a maximum of about 460 C after 3000 s and reduces below 440 s after 10000 s




ULOF Transient Results (Relap5)

0.0

0.2

0.4

0.6

0.8

1.0

-100 0 100 200 300 400 500

Time (s)F

ract

ion

(M

/Mo

)

Core flow

Core and SG exchanged power

Core mass flow rate

Core mass flow rate and power

0

100

200

300

400

500

-100 0 100 200 300 400 500

Time (s)

Po

we

r (M

W)

Core power

SG power

All primary pumps stop at 0 s (no pump inertia), secondary loops at nominal conditions

Core mass flow rate stabilizes at about 37% of the nominal value





Max lead temperature (top of active zone)

Average channel temperature

Hot channel temperature

450

550

650

750

850

-100 0 100 200 300 400 500

Time (s)

Te

mp

era

ture

(C

)

Tlead (inner_ave)

Tlead (middle_ave)

Tlead (outer_ave)

450

550

650

750

850

-100 0 100 200 300 400 500

Time (s)T

em

pe

ratu

re (

C)

Tlead (inner_hot)

Tlead (middle_hot)

Tlead (outer_hot)

Peak lead temperature reaches about 850 C in the hot channel of inner core zone just after pump stop

Max lead temperature stabilizes at about 625 C in the hot channel of outer core zone





Max clad temperature (top of active zone)



500

600

700

800

900

-100 0 100 200 300 400 500

Time (s)T

em

pe

ratu

re (

C)

Tclad (inner_hot)

Tclad (middle_hot)

Tclad (outer_hot)

500

600

700

800

900

-100 0 100 200 300 400 500Time (s)

Te

mp

era

ture

(C

)

Tclad (inner_ave)

Tclad (middle_ave)

Tclad (outer_ave)

Peak clad temperature reaches about 870 C in the hot channel of inner core zone just after pump stop

Max clad temperature stabilizes at about 660 C in the hot channel of inner core zone





Max fuel temperature (centre of active zone)



1000

1100

1200

1300

1400

1500

1600

-100 0 100 200 300 400 500

Time (s)T

em

pe

ratu

re (

C)

Tfuel (inner_hot)

Tfuel (middle_hot)

Tfuel (outer_hot)

1000

1100

1200

1300

1400

1500

1600

-100 0 100 200 300 400 500

Time (s)

Te

mp

era

ture

(C

)

Tfuel (inner_hot)

Tfuel (middle_hot)

Tfuel (outer_hot)

Peak fuel temperature reaches about 1525 C in the hot channel of middle core zone just after pump stop

Max fuel temperature stabilizes at about 1405 C in the hot channel of middle core zone




ULOF with SIMMER-III (Lead Temperature)




ULOF with SIMMER-III at 1000 s (Lead Velocities)

Horizontal velocityVertical velocity




ULOF: SIMMER-III – RELAP5 Comparison

Core mass flow rate and temperature

Core inlet / outlet temperature

Core mass flow rate

0.0

0.2

0.4

0.6

0.8

1.0

0 100 200 300 400 500

Time (s)

Fra

ctio

n (

M/M

o)

Core flow (simmer)

Core flow (relap5)

350

450

550

650

750

850

0 100 200 300 400 500

Time (s)T

em

pe

ratu

re (

C)

Tcore in (simmer)

Tcore out (simmer)

Tcore in (relap5)

Tcore out (relap5)

SG tube temperature in SIMMER-III calculation is imposed according to RELAP5 results

After the initial transient (about 200 s) there is a good agreement in code results




Use of SIMMER-IV (3-D Calculation)

In progress(Convergence and CPU time problems still to be solved)

A A

BB

SectionA - A

SectionB - B

eurotrans – dm1

Documents