BARC
BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 1
PASSIVE SYSTEMS RELIABILITY ANALYSIS USING THE METHODOLOGY APSRA
A.K. Nayak, PhD
Reactor Engineering Division
Bhabha Atomic Research Centre
Trombay, Mumbai 400085, India
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 2
India’s Innovative Reactor – The AHWR
• AHWR is a vertical pressure
tube type, boiling light water
cooled and heavy water
moderated reactor using
(233U-Th) O2 and (Pu-Th) O2
fuel.
MAJOR DESIGN OBJECTIVES
1. A LARGE FRACTION OF POWER FROM THORIUM.
2. DEPLOYMENT OF SEVERAL PASSIVE SAFETY SYSTEMS – 3 DAYS GRACE PERIOD.
3. NO NEED FOR EMERGENCY PLANNING IN PUBLIC DOMAIN.
4. POWER OUTPUT – 300 MWe.
CALANDRIA
STEAM DRUM
REACTOR BUILDING
INCLINED FUEL
TRANSFER MACHINE
FUELLING
MACHINE
FUEL BUILDING
GRAVITY DRIVEN
WATER POOL (GDWP)
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 3
General Arrangement of AHWR
Core cooling by natural circulation in Main Heat Transport System
Direct steam cycle, Moderator heat recovery
Decay heat Removal by Isolation Condensers
Passive ECCS injection by Accumulators & GDWP; Passive Containment Coolers
Moderator cooling, End Shield Cooling Calandria Vault Cooling Systems
GDWP Recirculation System
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 4
AHWR Reactor Building
Double Containment, Small V1-Volume containing High enthalpy MHT piping
Large inventory of water at higher elevation in Gravity Driven Water Pool
MAIN HEAT TRANSPORT
(MHT) SYSTEM
TAIL PIPES
REACTOR CAVITY
101000 GROUND LEVEL
GRAVITY DRIVEN
WATER POOL (GDWP)
ISOLATION CONDENSER
PRIMARY
CONTAINMENT
SECONDARY
CONTAINMENT
PASSIVE CONCRETE
COOLING SYSTEM
V1 VOLUME
HIGH TEMPERATURE, 285°C
DOWNCOMERS
STEAM DRUM (TYP.)
VENT SHAFT
TAIL PIPE TOWER
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 5
AHWR Reactor Block
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 6
Passive Safety Feature
Heat removal from core by natural circulation of coolant in Main Heat Transport System
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 7
Passive Safety Feature
Passive core decay heat removal by Isolation Condensers immersed in Gravity Driven Water Pool
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 8
Passive Safety Feature
Passive injection of ECC water during LOCA, initially from accumulators and later from the overhead GDWP, directly into fuel cluster.
Passive Containment Isolation & Passive Containment Cooling
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 9
Passive Safety Feature
Passive Poison Injection System actuates during very low probability event of failure of wired shutdown systems (SDS#1 & SDS#2) and non-availability of Main condenser
Passive Poison Injection in moderator during overpressure transient
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 10
Use of moderator as heat sink
Water in calandria vault
Flooding of reactor cavity following LOCA
Passive Safety Feature
Back up heat sink during low probable event of ECCS failure
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 11
AHWR PHWR
Light water coolant Heavy water coolant
Coolant boils in core No boiling of coolant Core flow maintained by Core flow caused by pump
natural circulation Vertical flow channel Horizontal flow channel
Passive decay heat removal Active decay heat removal
Core coolant transports heat Core coolant transfers heat to directly to condenser secondary coolant which rejects heat in condenser
Main Heat Transport System - AHWR vis-à-vis
PHWR
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 12
Safety criteria for advanced reactor systems
Risk based approach
Accuracy of Current
PSA treatment
- human reliability?
Advanced systems
- operator action
is minimized through
passive systems.
- reliability of
passive systems
must be considered. RADIOLOGICAL CONSEQUENCES
-
-
FR
EQ
UE
NC
Y
(even
ts/y
ea
r)
unallowable
domain
-
Fig 3. Frequency vs. Consequence Safety Goal
Quantitative Probabilistic Safety Goal
allowable
domain
Residual risk (RR) : no additional public health concerns
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 13
Why Passive Systems Can Fail?
While, Passive systems by definition, should operate only on the basis of fundamental natural physical laws, question arises
Can Such Systems Fail? • Possibly no – for example,
gravity does not fail; buoyancy does not fail or
in other words “mechanism does not fail”
• Possibly Yes – for example,
mechanism may not fail, but the system may not
be able to carry out the required duty or
defined objectives whenever called on
This is called as “Functional Failure” of a Passive System, which can happen if the boundary conditions deviate from the specified value on which the performance of the system depends. Mainly because, the driving force of passive systems are small, which can be easily changed even with a small disturbance or change in operating parameters.
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 14
Difficulties in Evaluation of Functional Failure of
Passive Systems
Lack of Plant Data and Operational Experience
Lack of sufficient experimental data from Integral Facilities or even from Separate Effect Tests in order to understand their performance characteristics not only at normal operation but also during transients and accidents.
The definition of failure mode of the systems are not well defined.
Difficulty in modeling the physical behaviour of such systems; particularly, • low flow natural circulation; the flow is not fully developed and can be multi-dimensional in
nature
• flow instabilities which include flashing, geysering, density-wave, flow pattern transition instabilities, etc.
• critical heat flux under oscillatory condition
• flow stratification with kettle type of boiling particularly in large diameter vessel
• thermal stratification in large pools such as in GDWP
• effect of non-condensable gases on condensation, etc.
Capability of so called “Best Estimate Codes” for such systems
- use models applicable for active systems.
- applicability for passive systems? Not well known.
- Uncertainty of predictions
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 15
Sources of Uncertainties
Uncertainties in the best estimate codes can arise due to
• incapable models built-in the codes to represent a specific
phenomena;
• absence of models to represent a particular phenomena;
• deviations of the input parameters due to the uncertainties of the
instruments and control systems and that of the geometry of the loop;
• uncertainties in the material properties such as fuel thermal
conductivity; fuel-to-clad gap conductance, etc.
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 16
Experimental Programme for Data Generation for
Assessment of Code Uncertainties
BARC has built many experimental facilities for study of
• Natural Circulation, Flow Instabilities, CHF Under
Oscillatory Condition;
• Condensation in Presence of Non-condensable;
• Behaviour of PCCS and PCIS
BARC will use its best estimate codes (RELAP5 and others) to
compare code prediction with test data and evaluate
uncertainties.
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 17
Experimental Facilities for Study of Boiling Two-phase
Natural Circulation
TEST SECTION
BUS BAR
BUS BAR
VENT LINEBLEED LINE
COOLING WATER OUT
COOLING WATER IN
CONDENSER
FILL LINE
DRAIN LINE
STEAM DRUM
RUPTURE DISCRELIEF VALVE
COOLER
COOLING WATER IN COOLING WATER OUT
Objectives
•To generate date for natural
circulation steady state and
stability behaviour
Major Design Parameters Design Pressure : 114 kg/cm2
Design temperature : 315 oC
Maximum Power : 80 kW
Loop Diameter : 50 mm
Elevation : 3000 mm
Heated Section : 1000 mm
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 18
Experimental Facilities for Study of Boiling Two-phase
Natural Circulation (Contd.)
STEAM DRUM
APSARA REACTOR
Test Section
NEUTRON BEAM
CONDENSER
Flow pattern transition studies
using neutron radiography
OBJECTIVES:
• Develop flow pattern transition
criteria
• To understand the low power
(Type I) and high power (type
II) instabilities in natural
circulation
• Measurement of CHF, pressure
drop, void fraction and its
distribution using NRG
• Evolution of Start-up
procedure
Operating Parameters:
Pressure : 70 bar
Temperature : 285 0 C
Neutron Flux : 106 to 108 n/cm2s
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 19
Experimental Facilities for Study of Boiling Two-phase
Natural Circulation (Contd.)
Objectives: • In-phase and out-of-phase
instability behaviour of
parallel channels in natural
circulation mode
• Effect of void reactivity
feed back on thermal
hydraulic stability
Geometric Details:
Number of channels : 4
Elevation : 3000 mm
Pipe diameter : 25 mm
Heater diameter : 12 mm
Length of heater : 1000 mm
Operating pressure : 15 bar
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 20
Experimental Facilities for Study of Boiling Two-phase
Natural Circulation (Contd.)
ISOLATION
CONDENSE
R
STEAM
DRUM N2
CYLINDE
R
ADVANCED
ACCUMULATOR
TAIL PIPE
GRAVITY DRIVEN
WATER POOL
RUPTURE
DISC
HEADER
FEEDER
ECCS
HEADER
FUEL
CHANNEL
SIMULATOR
INTEGRAL TEST
LOOP
Generation of database for performance evaluation
of following
Steady state performance of natural circulation in MHTS
- Mass flow rate
- Pressure drop
- void fraction
- CHF
- Gravity separation of Steam-water mixture in SD
Stability performance of natural circulation in MHTS
- Static instability
- Dynamic instability
Safety systems
- Passive decay heat removal system (ICS)
- ECCS
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 21
Scaling Philosophy for Design
A three level approach is followed
(a) GLOBAL SCALING
Power – to – Volume scaling philosophy adopted
• Pressure, temperature and elevation : 1:1
• Volume scaling ratio : 452
(b) BOUNDARY FLOW SCALING
• Feed water and steam flow simulation
• Pressure, temperature and enthalpy : 1:1
(c ) LOCAL PHENOMENA SCALED ARE
• CHF
• Geysering, flashing, Carry-over and carry-under in steam drum, etc.
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 22
Examples of Uncertainties of RELAP5/MOD3.2 with the
in-house natural circulation data
-50 0 50 100 150 200 250 300 350-30
-20
-10
0
10
20
30
% E
rro
r
Power (kW)
Apsara
HPNCL
ITL Uncertainties have been
evaluated for
- steady state natural
circulation,
- stability of natural
circulation and limited data
for CHF
Example of error distribution for the test data of ITL,
HPNCL and Apsara natural circulation loops
Ab
solu
te F
req
uen
cy
% Error
Experimental
Loop
Number of
steady state
data points
Uncertainty
Apsara ½” 87
~ 17 % HPNCL 26
ITL 14
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 23
Examples of Uncertainties of RELAP5/MOD3.2 with the
in-house natural circulation data (Contd.)
Uncertainties in code prediction for flow instabilities
State or condition of flow
- Stable
- Unstable
- Threshold of Instability
Characteristics of Instabilities
- Amplitude and frequency of oscillations including flow reversals
- Important for simulation of CHF
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 24
Examples of Uncertainties of RELAP5/MOD3.2 with the
in-house natural circulation data (Contd.)
How to Evaluate Uncertainties for Flow Instabilities Prediction?
Current Numerical Codes are formulated based on First-Order-Numerical Discretization.
They have inherent numerical problems due to
- ill-posedness of basic equations
- numerical diffusion
- instability whether physical or numerical???
- sensitive to nodalization, etc.
Capability of Best-Estimate Codes to flow instabilities are not proven even for the condition or state of instability.
Characteristics of Instability????
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 25
Example of Nodalization Sensitivity of RELAP5 code
for Simulation of Flow Instability
220 230 240 250 2604.9
5.0
5.1
5.2
5.3
5.4
5.5
Number of grids
in Riser
Ma
ss F
low
Ra
te (
kg
/s)
Time (s)
4 grids
8 grids
12 grids
36 grids
40 grids
44 grids
48 grids
52 grids
Inlet Feeder
pipes
Down
Comers
Ring
Header
Steam
Steam
drums
Tail
pipes
Fuel
bundles
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 26
Characterization of Uncertainty for Flow Instability
Prediction
Quantification of Uncertainties in Code Prediction for Instabilities is not
possible with the current knowledge.
A Qualitative Treatment Can be Given
Error Uncertainty
< 10% Low
10%<Error<30% Medium
30%<Error<50% High
>50% Severe
.
5.%EXPT
RELAPEXPT
Parameter
ParameterParameterError
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 27
Examples of Uncertainties in RELAP5 code for
prediction of CHF induced by flow instability
Tube ID
(mm)
Pressure
(bar)
Expt. CHF
(kW/m2)
Predicted
CHF
%Error Uncertainty
13.5 209.68 212.70 1.44 LOW
5.1 196.12 196.56 0.20 LOW
7.0
2.35 118.82 102.68 13.60 MEDIUM
8.11 356.61 310.30 12.99 MEDIUM
6.25 335.00 366.72 9.47 LOW
9.1
4.6 335.00 169.25 49.47 HIGH
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 28
Assessment of Passive Systems ReliAbility
(APSRA)
BARC has developed a methodology for Assessment of Passive Systems
ReliAbility known as APSRA.
It mainly considers the functional failure of the system to carry out the
desired function as the basis of the failure of the passive systems.
The functional failure due to deviation of parameters are correlated with the
failure of actual components through root diagnosis.
The methodology relies on in-house experimental data from simulated
facilities in addition to best estimate codes for evaluation of reliability.
The method has been evaluated to evaluate the reliability of various Passive
Systems of the AHWR.
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 29
APSRA - How it works ?
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 30
Reliability Evaluation of Natural Circulation Using
APSRA
Step I
Passive System – For example,
Natural Circulation in the
MHT System of the AHWR
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 31
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
Step II
Identification of its operational mechanisms:
Natural circulation operates by difference in density in hot
and cold legs (known as buoyancy force) balanced by
flow resistances.
Identification of its failure:
Natural circulation failure in AHWR can be identified by
- rise in clad surface temperature above a critical
value (400 oC) or/and
- occurrence of CHF by flow induced instability
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 32
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
Step III
Parameters affecting the
operation
Natural Circulation
Performance depends on
- operating pressure
- fission heat
- level in the steam drum
- feed water temperature/ core inlet
subcooling
- presence of non-condensable gases
- flow resistances in the system 2 4 6 8 10
1200
1400
1600
1800
2000
2200
2400
2600
Fig.6 Effect of pressure on primary system flow rate
Flo
w r
ate
- kg
/sec
Pressure - Mpa
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 33
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
Step IV
Key parameters causing the failure
- fission heat generation rate high
- level in steam drum low
- pressure in the system too low
- feed water temperature too low or
too high
- concentration of non-condensables
gases high
Failure can happen if these
parameters exceed their limits to
cause the failure as discussed in
Step II
200 220 240 260 280 300-2
0
2
4
6
8
10
12
Tsub
=25 K
Pressure = 70 bar
Ma
ss
flo
w r
ate
(k
g/s
)
Time (s)
2.6 MW (100% FP)
3.536 MW (136% FP)
3.614 MW (139% FP)
Flow oscillation induced CHF at high power
200 220 240 260 280 300-1
0
1
2
3
4
5
6
CH
FR
Time (s)
100% FP (2.6 MW)
136% FP (3.536 MW)
139% FP (3.614 MW)
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 34
ISOLATION
CONDENS
ER
STEAM
DRUM N2
CYLINDE
R
ADVANCED
ACCUMULATOR
TAIL PIPE
GRAVITY DRIVEN
WATER POOL
RUPTURE
DISC
HEADER
FEEDER
ECCS
HEADER
FUEL
CHANNEL
SIMULATOR
INTEGRAL TEST LOOP
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
How to determine the limits of the parameters
- Through use of best estimate codes
supplemented by experiments in order
to reduce the uncertainties in the best
estimate codes.
- BARC has a full scaled facility of the
AHWR, known as the Integral Test Loop
(ITL). This facility operates at the same
pressure and temperature conditions of
the AHWR.
- BARC also has number of experimental
facilities for study of boiling two-phase
natural circulation.
- Experiments will be conducted in these
facilities in order to confirm the limits of
the parameters at which failure of
natural circulation occurs.
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 35
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
Step – V :
Generation of failure surface
Failure Surface generated by
taking into account 3 parameters
010
20
30
40
505055
6065
7075
100
110
120
130
140
150
160
170
180
190
Subcooling (K
)
% F
ull
po
wer
Pressure (bar)
Success
Failure
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 36
Programme for Validation of Failure Surface with Test
Data
Range of Key Parameters to cause failure to be determined by Best Estimate Codes
Experimental Facilities
ITL HPNCL
PCL
Set the Key Parameters To the Desired Value as the input for the experiments
Monitor the Failure Variables
Compare code prediction with test data
Determine the Uncertainty and
modify the failure data points
Failure data point as input to Mathematical Model to generate failure surface
Failure Surface of Passive System
Input to step V
Benchmarking 20
40
60
80
05
1015
2025
0
300
600
900
1200Experimental Data
Unstable data
Stable data
Pow
er
(kW
)
Pre
ssure
(bar)
Stable
Unstable
Subcooling (K)
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 37
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
Step VI : Root Diagnosis
After establishing the domain of failure surface, Next task is to Identify the
causes for the deviation of key parameters
This must be done carefully through experts’
judgments.
The key parameters’ deviations are either caused by failure of some
active components such as
- valves, pumps, instruments, control systems, etc.
Or, due to failure of some passive components such as
- rupture disc, check valves, passive valves, etc.
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 38
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
Step VII Once the causes of failure of key parameters (either due to
active components or passive devices) are known in Step V,
the failure probability of the components can be evaluated in
the conventional way.
To evaluate the failure probability of certain components such as a
globe valve at partial open positions, a new methodology is being
developed.
An example of event tree/fault tree for high feed water
temperature or low inlet subcooling
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 39
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
FEEDTEMPw=1.150e-1
HIGH FEEDWATER
TEMPERATURE
LOWFEEDFLOW
w=1.150e-1
LOW FEEDWATERFLOW
FEED VALVES MALFUNCTI ONI NG
w=2.064e-10
VALVESFEED&STEAM
SIDE
CHECK VALVEw=1.240e-2
Check Valves inthe feed water line
Malfuction
SD-LEVEL-CNTRL- FAIL1
w=2.018e-7
2
Steam DrumLevel controllermalfuctioning
LEVELCNTRL VAL
Malfuctioningof level control
Valves
w=4.31102e-005*
CEP-MKV
Condensateextration pump
malfuction
w=0.0530312*
FWP-MKV
Feed waterPump
malfuction
w=0.0530312*
VAL-STEAMw=2.694e-2
Inadvertantopening ofVALVES
VAL-FEEDw=2.656e-7
IsolationvalveS feedwater side
SD-LVL-CNTRL1
Steam DrumLevel controller-1
malfuctioning
r=0.003504
SD-LVL-CNTRL2
Steam DrumLevel controller -2
malfuctioning
r=0.003504
SD-LVL-CNTRL3
Steam DrumLevel controller-3
malfuctioning
r=0.003504
LVL-CHV1
before levelcontrol valves -Check Valve 1
stuck close
r=0.0062
LVL-CHV2
After level controlvalves - CheckValve2 stuck
close
r=0.0062
CV-STEAM
Inadvertant openingof C/V in the steamside of temp control
heater
r=0.0245
MANUAL VALVE-STEAM
Parallel MANUALvalve fails toremain closed
r=0.00245
ISOVAL1-FEED
Isolation valve-1 inthe temp control
heater feed waterside fails to remain
closed
r=0.002628
ISOVAL2-FEED
Isolation valve-2 inthe temp control
heater feed waterside fails to remain
closed
r=0.002628
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 40
Reliability Evaluation of Natural Circulation Using
APSRA (Contd.)
Step VIII
Evaluation of Reliability Of NC System
160.0
150.0
170.0
140.0
130.0
180.0
180.0
50 55 60 65 70 755
10
15
20
25
30
35
40
45
50
120.0
Failure frequency
-5E-10
0
5E-10
1E-9
1.5E-9
2E-9
2.5E-9
3E-9
3.5E-9
Pressure (bar)
Su
bco
olin
g (
K)
Constant % full power lines
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 41
APSRA applications: other examples
Isolation Condenser
0 20 40 60 80 100
0
1
2
3
4
5
6
7
40
50
60
70
80
90
Failure region
Success region
% o
f N
on
-co
nd
en
sab
les
GD
WP
wate
r
tem
pera
ture
(oC
)
% Height Exposure of IC Tubes
Failure probability for IC to maintain
Hot-SD ~ 8x1e-7/ yr
0 20 40 60 80 100 120 140 160 180 2000
10
20
30
40
50
60
70
80
90
100
Failure due to insufficient
V1-V2 pressure differential to
raise water to spill into duct
Failure due to insufficient
inventory in the tank to
form liquid seal
Success region
Failu
re r
eg
ion
Failure region
Wate
r le
vel in
tan
k (
% o
f d
esig
n v
alu
e)
% Break size
Passive Containment Isolation
System (PCIS)
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BARC
INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 42
RMPS vs. APSRA
There are certain points which are common in both the
methodologies; for example,
• treatment of the functional failure as the failure of the system
• identification of functional failure criteria
• evaluation of uncertainties in code prediction
• Consideration of uncertainties in prediction of functional failure
of system.
However, there are differences; for example,
• treatment of deviation of key parameters causing the failure
• generation of failure data/surface
• consideration of test data/code-to-code differences for
calculation of uncertainties.
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INPRO Consultancy Meeting JUNE 16-17, 2008, Cadarache, France 43