1
Kaspar Kööp, Marti JeltsovDivision of Nuclear Power Safety
Royal Institute of Technology (KTH) Stockholm, Sweden
LEADER 4th WP5 MEETING, Karlsruhe – 22nd of November 2012
Analyses of representative DEC eventsof the ETDR
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ETDR – ALFRED description• Pool-type• 300 MWth• Core pressure drop 1 bar• Temperature
– Core inlet 400 C– Core outlet 480 C
• Coolant velocity– Average 2 m/s– Maximum 3 m/s
• Lead void effect at EOC (only the fuel zones)– +2 $
3
KTH contributionTransients to be analyzed for Pb-cooled ALFRED Design (LEADER project)
Case Number Transient Description Burnup
State
Transients analyzed for Lb-cooled ALFRED Design BOC EOC
ENEA KIT-G NRG JRC/IET KTH
RELAP5 SIM-LFR SPECTRA SIMMER / TRACE
RELAP5 / CFD code
DEC Transients
TR-4
Reactivity insertion
(enveloping SGTR, flow blockage,
core compaction)
Reactivity insertion (voiding of part of
active region enveloping voids
introduction due SGTR, core compaction, fuel blockage) = 250 pcm
Reactor at hot full power (HFP)
X X X X X X (*) X (**)
TO-3
Reduction of FW
temperature + all pumps
stop
Loss of one preheater (feedwater temperature reduction from 335oC
down to 300oC) All primary pumps are
stoppedReactor is tripped
X X X X X
TO-6
Increase of FW flowrate+
all pumps stop
20 % increase in feedwater flowrate
All primary pumps are stopped
Reactor is tripped
X X X X X
T-DEC1
Complete loss of forced
flow + Reactor trip fails (total
ULOF)
All primary pumps are stopped
Feedwater system available
Reactor trip fails
X X X X X X (*) X
T-DEC3Loss of SCS+ Reactor trip
fails (ULOHS)
All primary pumps are operating
DHR system is operating
Reactor trip fails
X X X X X X (*)
T-DEC4
Loss of off-site power (LOOP) +
Reactor trip fails (ULOHS
+ ULOF)
All primary pumps are stopped
SCS is lostDHR system is
operatingReactor trip fails
X X X X X X
T-DEC5
Partial blockage in the hottest
fuel assembly
Reactor trip failsThe maximum acceptable flow
reduction factor has to be determined
X X X X X X
T-DEC6 SCS failure
All primary pumps are operating
DHR system totally fails
Reactor is tripped
X X X X X
• TR-4 – a transient event due to reactivity insertion (enveloping SGTR, flow blockage, core compaction)
• T-DEC1 – complete loss of forced flow + SCRAM fail
• T-DEC4 – complete loss of forced flow, complete loss of SCS, DHR system operating + SCRAM fail
4
TR-4 – Description
• TR-4 – a transient event due to reactivity insertion (enveloping SGTR, flow blockage, core compaction)
• We have shown in our previous works that using system TH codes it is not possible "...to investigate whether the steam bubble or bubbles can be dragged downwards towards the core inlet region.“
• Steam Generator Tube Leakage (SGTL) is assumed to be the cause for reactivity insertion (voiding of part of active region
• We address the task on the transport of bubbles that have leaked in the SG to the primary coolant flow
• Reactor is at hot full power (HFP)• Actions:
– First thermal-hydraulic part (CFD analysis of bubble transport)– Neutronic part (SERPENT code to look at the consequences of different
local core voiding that are typical for SG leakage)
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TR-4 – Thermal-hydraulics approach• Approach:
– Develop (or ask from partners) 3D CAD model of primary system of ALFRED according to the latest design provided to LEADER partners.
– Create 3D mesh of the primary system for CFD analysis.– Simulate primary coolant flow at normal (HFP) operation conditions
with a 3D CFD code (Star-CCM+)– Simulate bubble transport from the SG to the core– Assumptions in modeling of bubble transport:
• Lagrangian framework• Turbulent dispersion• Uncertainty in:
– bubble size distribution– different correlations for bubble drag in lead– locations of possible leakage from steam generator– leak rate– voiding scenarios– etc.
– Assess void accumulation rate in the core accounting for the uncertainties given
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TR-4 – Neutronics approach
• Neutronics part of the analysis is foreseen to be done using Serpent Monte Carlo code
• Input for neutronic calculation– void characteristics:
• accumulation rates• voiding scenarios are input for neutronics calculation
– geometry• ALFRED model exists in the house
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T-DEC1&4 ENEA’s RELAP5 model
Feedwater
Steam521-8
531-8
551-8 561-8
151-
8
Feedwater
Steam521-8
531-8
551-8 561-8
151-
8
841- 4
851- 8441-8
801- 4
811-4831-4
815
401-8
841- 4
-
801- 4
811-4831-4
815
841- 4
-
801- 4
811-4831-4
815
611- 8
841- 4
-
801- 4
811-4831-4
815
611-
711-
731-
741- 4
751- 8
761- 4
621- 4
641- 4
771
781- 8
601- 4
661- 4
611-
711- 8
731- 8
741- 4
751-
761- 4
621- 4
641- 4
771 - 8
781-
601- 4
661- 4
611-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781
601- 4
661- 4
841- 8
-
801- 4
811-4831-4
815
841-
-
801- 8
811-8831-8
815
611-
841-
-
801-
811-831-
411-8
611-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771
781
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781-
601- 8
661- 8
611-
711-
731-
741- 8
751-
761- 8
621- 8
641- 8
841- 4
851- 8441-8
801- 4
811-4831-4
815
401-8
841- 4
-
801- 4
811-4831-4
815
841- 4
-
801- 4
811-4831-4
815
611- 8
841- 4
-
801- 4
811-4831-4
815
611-
711-
731-
741- 4
751- 8
761- 4
621- 4
641- 4
771
781- 8
601- 4
661- 4
611-
711- 8
731- 8
741- 4
751-
761- 4
621- 4
641- 4
771 - 8
781-
601- 4
661- 4
611-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781
601- 4
661- 4
841- 8
-
801- 4
811-4831-4
815
841-
-
801- 8
811-8831-8
815
611-
841-
-
801-
811-831-
411-8
611-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771
781
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781-
601- 8
661- 8
611-
711-
731-
741- 8
751-
761- 8
621- 8
641- 8
ALFRED Nodalization scheme with RELAP5
8 SGs
8 Secondary loops Primary circuit
8 IC loops
Steam line
Feedwater line
100
101102109
110
115
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
100
101102109
110
115
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
100
101102109
110
115
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
Feedwater
Steam521-8
531-8
551-8 561-8
151-
8
Feedwater
Steam521-8
531-8
551-8 561-8
151-
8
841- 4
851- 8441-8
801- 4
811-4831-4
815
401-8
841- 4
-
801- 4
811-4831-4
815
841- 4
-
801- 4
811-4831-4
815
611- 8
841- 4
-
801- 4
811-4831-4
815
611-
711-
731-
741- 4
751- 8
761- 4
621- 4
641- 4
771
781- 8
601- 4
661- 4
611-
711- 8
731- 8
741- 4
751-
761- 4
621- 4
641- 4
771 - 8
781-
601- 4
661- 4
611-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781
601- 4
661- 4
841- 8
-
801- 4
811-4831-4
815
841-
-
801- 8
811-8831-8
815
611-
841-
-
801-
811-831-
411-8
611-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771
781
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781-
601- 8
661- 8
611-
711-
731-
741- 8
751-
761- 8
621- 8
641- 8
841- 4
851- 8441-8
801- 4
811-4831-4
815
401-8
841- 4
-
801- 4
811-4831-4
815
841- 4
-
801- 4
811-4831-4
815
611- 8
841- 4
-
801- 4
811-4831-4
815
611-
711-
731-
741- 4
751- 8
761- 4
621- 4
641- 4
771
781- 8
601- 4
661- 4
611-
711- 8
731- 8
741- 4
751-
761- 4
621- 4
641- 4
771 - 8
781-
601- 4
661- 4
611-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781
601- 4
661- 4
841- 8
-
801- 4
811-4831-4
815
841-
-
801- 8
811-8831-8
815
611-
841-
-
801-
811-831-
411-8
611-
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771
781
711-
731-
741- 4
751-
761- 4
621- 4
641- 4
771 -
781-
601- 8
661- 8
611-
711-
731-
741- 8
751-
761- 8
621- 8
641- 8
ALFRED Nodalization scheme with RELAP5
8 SGs
8 Secondary loops Primary circuit
8 IC loops
Steam line
Feedwater line
100
101102109
110
115
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
100
101102109
110
115
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
100
101102109
110
115
060061-8 070
050
020
200 151-8
121-8
131-8
141-8
220
230
210
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Model steady state
Parameter By design Previous input New input (5.11.12)Nominal reactor power 300 MWth 300.01 MWth 299.35 MWthNumber of SGs 8Number of PPs 8Power removed per SG 37.5 MWth 37.50125 MWth 37.41875 MWth
Lead (primary system)Core inlet temperature 400 C 673.07 K (399.92 C) 670.42 K (397.27 C)Core outlet temperature 480 C 753.03 K (479.88 C) 754.75 K (481.60 C)Mass flow rate 3247.5*8 kg/s 25013 kg/s (3126.625 * 8) 24636 kg/s (3079.5 * 8)
Secondary sidePressure
180 bar Imposed 188 bar feed water inImposed 180 bar steam out
Water inlet temperature 335 C 608.14 K (334.99 C) 608.14 K (334.99 C)Steam outlet temperature 450 C 723.36 k (450.21 C) 722.24 K (449.09 C)Mass flow rate 24.1 kg/s/SG 24.08 kg/s/SG 24.08 kg/s/SGPressure drop over core 0.98 bar
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T-DEC1 – Description
• T-DEC1 – complete loss of forced flow + SCRAM fail
• Pumps are tripped at 1500s
• Secondary side is operational, IC valves closed
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T-DEC1 - loss of 8 pumps
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T-DEC1 - loss of 7 pumps
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T-DEC4 – Description
• T-DEC4 – complete loss of forced flow + complete loss of secondary cooling system + SCRAM fail
• Pumps are tripped at 1500s• SCS is tripped at 1500s
• IC valves opened at 1500.5s
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T-DEC4 – loss of flow + loss of SCS + IC valves open
?
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Next steps
• Check T-DEC4 results
• Combine T-DEC1 and T-DEC4– Only some pumps fail– Only some IC valves open– Possibility of pump/valve recovery
• Look for – Overcooling/overheating scenarios– High local velocity scenarios– …
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SGTR
