safety analysis of supercritical-pressure light-water cooled reactor with water rods yoshiaki oka...
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Safety analysis of supercritical-pressure light-water cooled reactor with water rods
Yoshiaki Oka
April 2003, GIF SCWR Mtg. at Madison
SCLWR-H plant system
Flow rate low Level 1 Reactor scram Level 2 AFS Level 3 MSIV/ADS/LPCI systemPressure low Level 1 Reactor scram Level 2 MSIV/ADS/LPCI systemPressure high Level 1 Reactor scram Level 2 SRVAFS: auxiliary feedwater system MSIV: main steam isolation valve ADS: automatic depressurization systemLPCI: low pressure core injection system
Capacity:RCIC(AFS) TD 1 unit: 4%/unitAFS TD 2 units: 4%/unitADS 8 units: 20%/unit at 25MPaLPCI MD 3 units: 150kg/s/unit at 1.0MPa
Configuration: TD- RCICLPCI/RHR
TD-AFS TD-AFSLPCI/RHR LPCI/RHRRCIC: reactor core isolation cooling system
RHR: residual heat removal system
Accidents
1 Total loss of feedwater
2 Reactor coolant pump seizure
3 Control rod ejection at normal operation
4 Control rod ejection at hot standby
5 Control rod ejection at cold standby
Transients
6 Loss of feedwater heating
7 Inadvertent startup of AFS
8 Partial loss of feedwater
9 Loss of offsite power
10 Loss of load with turbine bypass
11 Loss of load without turbine bypass
12 Control rod withdrawal at normal operation
13 Control rod withdrawal at hot standby
14 Feedwater control system failure
15 Pressure control system failure
24.0
24.5
25.0
600650700750800850
0 5 10 15 20 25 300
20
40
60
80
100
pressure
feedwater flow rate
peak cladding temperature
power
time [s]
rati
o [
%]
tem
peratu
re [℃
]pre
ssure
[MP
a]
Total loss of feedwater accident
Coast-down time [s] 1 2 3 4 5
PCT [ ]℃ 974 934 890 859 833
AFS capacity [%/unit] 1 2 3 4 6
PCT [ ]℃ 872 857 856 833 816
AFS delay [s] 3 10 30
PCT [ ]℃ 833 902 904
PCT: peak cladding temperature
Total loss of feedwater accident
25.0
25.5
26.0
26.5
27.0
600
650
700
750
0 1 2 3 4 50
50
100
150
200
main steam flow rate
pressure
feedwater flow rate
peak cladding temperature
power
time [s]
rati
o [
%]tem
perature [℃]
pressure [MP
a]
Loss of load without turbine bypass transient
1 2 3 4 5 6 7 8 9 10 11 12600
700
800
900
1000
1100
1200
1300
Transient criterion
Accident criterion
151413119 108765
peak
cla
ddin
g te
mpe
ratu
re [
℃]
event number (corresponding to Table 3)
Ratio of coolant density coefficient 0.5 1 1.3 1.5
Maximum pressure [MPa] 26.8 26.8 27.6 28.7
Maximum power [%] 114 154 419 887
Peak cladding temperature [ ]℃ 707 727 873 1040
SRV setpoint [MPa] 26.0 26.2 26.5
Maximum pressure [MPa] 26.6 26.8 27.2
Maximum power [%] 135 157 177
Peak cladding temperature [ ]℃ 698 727 652
PCT: peak cladding temperature
Loss of load without turbine bypass transient
1 2 3 4 5 6 7 8 9 10 11 12 13 14 1524
25
26
27
28
29
30
31
Transient criterion
Accident criterion
max
imum
pre
ssure
[M
Pa]
event number (corresponding to Table 3)
Transients PCT [ ]℃ Over 670℃ Over 700℃
Loss of feedwater heating 671 1.5 s -
Partial loss of flow 702 4.5 s 1.0 s
Loss of load (no-bypass) 727 0.5 s 0.3 s
PCT: Peak Cladding Temperature
Durations of high cladding temperature
Result – 100% hot leg break (blowdown)
200
300
400
500
600
700
0 10 20 30 40 50 600
5
10
15
20
25
pressre peak cladding
temperature
Time [s]
Pre
ssure
[M
Pa]
Tem
peratu
re [℃
]
0 10 20 30 40 50 600
100
200
300
400
Break ADS Hot leg (Intact)
Flo
w r
ate [
%]
Time [s]
ADS line
LPCI
ADS
MFL
MSIVMSL
Break
Result – 100% hot leg break (blowdown)
200
300
400
500
600
700
0 10 20 30 40 50 600
5
10
15
20
25
pressre peak cladding
temperature
Time [s]
Pre
ssure
[M
Pa]
Tem
peratu
re [℃
]
0 10 20 30 40 50 600
100
200
300
400
Break ADS Hot leg (Intact)
Flo
w r
ate [
%]
Time [s]
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0 10 20 30 40 50 600
50
100
150
200
250
300
350
400
power average water density
Time [s]
Pow
er
[%]
Density [g/
cm
3]
Result – 100% Cold leg break (blowdown)
0
200
400
600
800
1000
0 20 40 600
5
10
15
20
25
pressure peak cladding
temperature
Time [s]
Pre
ssure
[M
Pa]
Tem
peratu
re [℃
]
0 20 40 60- 600
- 400
- 200
0
200
400
600
Core top Core bottom Water rod top
Flo
w r
ate [
%]
Time [s]
Break
0
200
400
600
800
1000
0 100 200 300 400 500 6000
5
10
15
20
25
pressure peak cladding
temperature
Time [s]
Pre
ssure
[M
Pa]
Tem
peratu
re [℃
]
200 400 600 8000
1
2
3
4
5
6
7
Core Down comer
Wat
er lev
el [m
]
Time [s]
LPCI 容量 (kg/s/u
nit)100 150 300 400 800
被覆温度( )℃
1190 930 800 690 650
0 10 20 300
50
100
450
500
550
Core power Core flow rate
Rat
io [%
]Time [s]
T = 0 sec : Scram, T = 1 sec : ADS
300
400
500
600
700
0 20 40 60 80 100 1200
5
10
15
20
25
pressre peak cladding
temperature
Time [s]
Pre
ssur
e [M
Pa] T
emperature [C
]
Core power does not exceed 100%.
Cladding temperature does not exceed that of normal operation.
Depressurization cools the core effectively
T = 0 sec : ADS, T = 0.55 sec : Scram
300
400
500
600
700
0 20 40 60 80 100 1200
5
10
15
20
25
pressre peak cladding
temperature
Time [s]
Pre
ssur
e [M
Pa] T
emperature [C
]
0 10 20 300
50
100
150
200
250
300
Core power Core flow rate
Rat
io [%
]Time [s]
Core power increases to 160% before scram.
But cladding temperature does not exceed that of normal operation because core flow rate is higher.
Summary of the results
• Total loss of flow accident: maximum cladding temperature stays low, 833C (margins to the limit 1260C)
• Overpressurization transient without turbine bypass shows 50% power rise and Tc reaches 727C, (margins to the limit 800C )
• Duration of high cladding temperature is short less than 5 sec. Potential for improvement of fuel integrity criteria at transients.
• Hot leg break LOCA gives rise to reactivity insertion. But Tc reaches only 550C. Core flow is induced by depressurization due to the once-through coolant cycle.
• Cold leg break LOCA, Tc reaches 930C, (margins to the limit 1260C)
• Depressurization cools the core effectively