ENTE PER
FPN-FISNUC
/ Bologna
LE NUOVE TECNOLOGIE,
L’ENERGIA E L’AMBIENTE
EUROTRANS – DM1
RELAP5 Model Evaluation with
SIMMER-III Code and Preliminary
Transient Analysis for EFIT Reactor
P. Meloni, G. Bandini, M. Polidori
WP5.1 Progress Meeting
KTH / Stockholm, May 22-23, 2007
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)
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
Used Approach
SIMMER-III calculation
PLOHS (beam trip at t = 0 s)
3 DHR in operation
Comparison
Comparison with
ANSALDO data
Recirculation ratio
at DHR outlet
Additional RELAP5 pressure
drop coefficients to fit core
and DHR natural circulation
mass flow rates (SIMMER)
RELAP5 calculation
PLOHS (beam trip at t = 0 s)
3 DHR in operation
RELAP5 revised model
RELAP5 model
evaluation and
transient analysis
Transient analysis
with RELAP5
ULOF
with SIMMER-III
Comparison
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
ULOF
PLOHS
(beam and pump
trip if aver. core
out T > 500 C)
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)
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
SIMMER-III Results (Lead Temperature)
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
SIMMER-III Results (Lead Temperature)
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
SIMMER-III Results at 3600 s (Lead Velocities)
Vertical velocity
Horizontal velocity
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
Recirculation Ratio at DHR Outlet for RELAP5
SIMMER-III
Results at
t = 3600 s:
ANSALDO
after 1 hour
(P = 16 MW)
mC = 2740 kg/s
mD = 2983 kg/s
TCi = 410.5 C
TCo = 449.1 C
TDi = 444.6 C
TDo = 407.0 C
y = mC
TDi
2985 Kg/s
mD
444 C
407 C
(TCi - TDo)
(TDi - TDo)
TCo
mC
Recirculation ratio at
DHR outlet:
x = 498 kg/s (17% of mD)
TDo
TDi
TCo
x
y
TCi
x = y + mD - mC
y = 255 kg/s
TCo
TCi
TCi
Simplified scheme of RELAP5 model
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
SIMMER and RELAP5 Comparison at t = 3600 s
Parameter
Unit
SIMMER-III
RELAP5
RELAP5 (revised)
Kg/s
2740
3047
2737
Core inlet temperature
C
410.5
413.7
410.5
Core outlet temperature
C
449.1
448.5
449.2
Kg/s
2983
3108
2983
DHR inlet temperature
C
444.6
442.7
443.0
DHR outlet temperature
C
407.0
408.4
406.9
MW
16.67
15.89
16.02
Core mass flow rate
DHR mass flow rate (3 units)
DHR removed power (3 units)
TDi
mD
TCo
mC
TCo
TDo
TDi
TCo
x
y
Additional pressure drop
coefficients in RELAP5 model
to fit SIMMER-III results
TCi
TCi
TCi
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
Code Result Comparison (Transient)
Core inlet / outlet temperature
Core mass flow rate
and temperature
490
Tcore in (simmer)
Tcore out (simmer)
Tcore in (relap5)
Tcore out (relap5)
Temperature (C)
470
Core mass flow rate
4000
450
430
Flow rate (kg/s)
3000
410
2000
390
0
Core flow (simmer)
1000
1000
2000
3000
Time (s)
4000
5000
Core flow (relap5)

0
0
1000
2000
3000
Time (s)
4000
5000
After the initial transient (about 2000 s)
the revised RELAP5 model fit very well
the SIMMER-III results
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
Code Result Comparison (Transient)
DHR inlet / outlet temperature
DHR mass flow rate
and temperature
450
440
Temperature (C)
Tdhr in (simmer)
DHR mass flow rate
4000
430
Tdhr out (simmer)
Tdhr in (relap5)
420
Tdhr out (relap5)
410
Flow rate (kg/s)
3000
400
390
2000
0
1000
2000
3000
Time (s)
4000
5000
DHR flow (simmer)
1000
DHR flow (relap5)

0
0
1000
2000
3000
Time (s)
4000
5000
After the initial transient the revised
RELAP5 model fit well the SIMMER-III
results, and stable DHR operation is
predicted by both codes
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
Code Result Comparison (Transient)
30
DHR power (simmer)
25
Core
decay
power
DHR power (relap5)
Decay power
Power (MW)
20
and
15
DHR
removed
power
10
5
0
0
1000
2000
3000
Time (s)
4000
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
5000
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)
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1, WP1.5 Progress Meeting
Nominal Conditions (RELAP5 steady-state)
Parameter
Thermal power (MW)
Lead mass flow rate (kg/s)
Inner
zone
Middle
zone
Outer
zone
Reflector
+ by-pass
Total
96
142.3
140.5
0 (*)
378.8
7615
11330
11805
1106
31856
(*) about 5 MW (not considered in this study)
Maximum
temperature
(°C)
Inner zone
Middle zone
Outer zone
(Fax = 1.14)
(Fax = 1.16)
(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
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
PLOHS Transient Results (Relap5)
About 3 hours transient
Core and DHR
mass flow rate
6000
Flow rate (kg/s)
DHR flow
Initial transient
35000
Flow rate (kg/s)
Core flow
5000
30000
Core flow
25000
DHR flow
4000
3000
2000
1000
20000
0
0
15000
10000
0
100
300
200
Time (s)
400
500
4000
6000
Time (s)
8000
10000

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
5000
0
2000
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
PLOHS Transient Results (Relap5)
About 3 hours transient
Core and DHR
power
30
Core power
25
DHR power
Power (MW)
20
Initial transient
400
350
Core power
300
DHR power
15
10
Power (MW)
5
250
0
200
0
2000
150
100
0
200
400
600
Time (s)
800
1000
8000
10000

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)
50
0
4000
6000
Time (s)
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
PLOHS Transient Results (Relap5)
About 3 hours transient
Max lead and clad
temperature
600
Temperature (C)
Tclad (inner_hot)
Initial transient
600
Tlead (inner_hot)
570
Tlead (inner_hot)
570
540
510
480
Temperature (C)
Tclad (inner_hot)
450
540
420
510
0
2000
4000
6000
Time (s)
8000
10000
480
450
420
0
100
200
300
Time (s)
400
500

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
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
PLOHS Transient Results (Relap5)
Max fuel temperature
(hot channel)
Max vessel wall
temperature
480
About 3 hours transient
1400
1200
Tfuel (middle_hot)
Tfuel (outer_hot)
Temperature (C)
1400
1200
Temperature (C)
460
Tfuel (inner_hot)
1000
Tfuel (inner_hot)
Tfuel (middle_hot)
800
1000
600
800
400
Tfuel (outer_hot)
Temperature (C)
Initial transient
440
420
Vessel temp1
Vessel temp2
Vessel temp3
400
380
0
2000
4000
6000
Time (s)
8000
10000
2000
0
6000
4000
Time (s)
8000
10000
600

400
0
100
200
300
Time (s)
400
500
The vessel wall temperature
reaches a maximum of about
460 C after 3000 s and reduces
below 440 s after 10000 s
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
ULOF Transient Results (Relap5)
Core mass flow rate
Core mass flow rate
and power
1.0
Fraction (M/Mo)
Core and SG exchanged power
500
Power (MW)
400
0.6
0.4
0.2
300
0.0
-100
Core power
200
0
100
200
Time (s)
300
400
SG power
100
0
-100
Core flow
0.8
0
100
200
Time (s)
300
400
500

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
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
500
ULOF Transient Results (Relap5)
Hot channel temperature
850
Max lead temperature
(top of active zone)
Tlead (inner_hot)
Temperature (C)
Average channel temperature
850
Tlead (inner_ave)
Temperature (C)
Tlead (outer_hot)
650
550
Tlead (middle_ave)
750
Tlead (middle_hot)
750
Tlead (outer_ave)
450
-100
650
550
450
-100
0
100
200
Time (s)
300
400
500
0
100
200
Time (s)
300
400

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
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
500
ULOF Transient Results (Relap5)
Hot channel temperature
Max clad temperature
(top of active zone)
900
Tclad (inner_hot)
Tclad (middle_hot)
Temperature (C)
800
Average channel temperature
900
Tclad (inner_ave)
Temperature (C)
700
600
Tclad (middle_ave)
800
Tclad (outer_hot)
Tclad (outer_ave)
700
500
-100
600

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
500
-100
0
100
200
Time (s)
300
400
500
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
0
100
200
Time (s)
300
400
500
ULOF Transient Results (Relap5)
Hot channel temperature
Max fuel temperature
(centre of active zone)
1600
Temperature (C)
1500
Average channel temperature
1600
Tfuel (inner_hot)
1500
1300
1100
Tfuel (outer_hot)
Tfuel (outer_hot)
1400
1000
-100
1300
1200
0
100
200
Time (s)
300
400
500
0
100
200
Time (s)
300
400

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
1100
1000
-100
Tfuel (inner_hot)
1200
Tfuel (middle_hot)
Tfuel (middle_hot)
Temperature (C)
1400
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
500
ULOF with SIMMER-III (Lead Temperature)
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
ULOF with SIMMER-III (Lead Temperature)
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
ULOF with SIMMER-III at 1000 s (Lead Velocities)
Vertical velocity
Horizontal velocity
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
ULOF: SIMMER-III – RELAP5 Comparison
Core inlet / outlet temperature
850
Core mass flow rate
and temperature
Tcore in (simmer)
Temperature (C)
750
Core mass flow rate
1.0
Core flow (simmer)
0.8
Tcore in (relap5)
Tcore out (relap5)
650
550
450
Core flow (relap5)
Fraction (M/Mo)
Tcore out (simmer)
0.6
350
0
0.4
0
100
200
300
Time (s)
400
500
200
300
Time (s)
400

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
0.2
0.0
100
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
500
A
A
Use of SIMMER-IV
(3-D Calculation)
In progress
B
B
(Convergence and CPU time
problems still to be solved)
Section
A-A
KTH – Stockholm, May 22 – 23, EUROTRANS – DM1 – WP1.5 Progress Meeting
Section
B-B