Safety issues review of the EU HCLL ITER TBM

Transcription

Safety issues review of the EU HCLL ITER TBM
I. HCLL main features
II. Safety issues
III. Occupational exposure
IV. Conclusion
Christian Girard (CEA/Cadarache – France)
Ch. Girard - 8th IAEA Technical Meeting on « Fusion Power Plant Safety »
1
I - HCLL TBM main features
2
The HCLL (He-PbLi) DEMO blanket
DEMO HCLL
Main features
Large modules
RAFM steel
(EUROFER)
Module box
(container &
surface heat
extraction)
He (8 MPa, 300-500°C)
Breeder
cooling unit
(heat extraction
from PbLi)
Liquid Pb-15.7Li
(eutectic) as breeder
and multiplier
Lifetime 7.5 MWy/m2
PbLi slowly recirculating (10/50
rec/day)
90 % 6Li in Pb-15.7Li
TBR = 1.15 with
550mm Breeder radial
depth
Stiffening
grid
He collector system
(back plates)
3
The HCLL TBM to be tested in ITER
BUs
BUs back plates
BUs He collectors
TBMs have to be DEMOrelevant TBMs proposal
are derived from DEMO
programs
First TBMs have to be
installed since the first
day of the H-H operation
(to check interfaces & main
operations, compatibility with
ITER operations and to support
to licensing and safety dossier)
TBM
design
(mainly
Breeder Units) will be
specifically optimized for
each ITER phase (at least
4 different TBMs could be
tested in ITER)
Top cover
Stiffening grid
PbLi inlet pipe
FW/SW
Vertical shear key-way
PbLi distribution box
He inlet pipe
PbLi feeding pipe
Horizontal shear key-way
Stiffening rod
Vertical shear key-way
PbLi feeding pipe
He outlet pipe
BP1
PbLi outlet pipe
BP2
BP3
BP4
Back collector
4
Helium-Cooled Lithium-Lead (HCLL)
ITER TBM description
HCLL main design features
Box layout common with HCPB
– FW
– Stiffening plates (SPs)
– Back collectors
radial cells delimited by stiffening
plates (SPs) for box resistance
under faulted conditions
breeder units inside cells
All flow connections located at
the rear of the module
6
HCLL blanket design
7
First Wall – Toroidal He cooling
He out
He in
8
Horizontal/vertical Stiffening Plates (He cooled)
He in/out
9
He flow in horizontal/vertical Stiffening Plates (SPs)
10
Breeder units are inserted inside cells
11
Breeder units inserted inside SPs (view from back)
12
HCLL breeder unit design
Front
He in/out unit
manifolds
Cooling Plates
(CPs)
He unit inlet
He unit outlet
Unit backplate
13
He flow scheme in cooling plates
14
Design of a 3-levels collector
(Module top view)
Level # 1:
-Main inlet He spreadout
-FW/SP/Covers inlet
Level # 2:
- FW/SP/Covers return
- Breeder unit inlet
Level # 3:
-Breeder unit return
Main outlet He
Main inlet He
15
HCLL breeding blanket
He flow scheme
He flow scheme – I
Stage # 1:
-Main inlet He spreadout
-FW/SP/Covers inlet
(Module top view)
80% He in FW
20% He in SPs
Main He inlet
17
He flow scheme – II
(Module top view)
80% He in FW
100% He in BUs
20% He in SPs
Stage # 2:
- FW/SP/Covers return
- Breeder unit inlet
Main He inlet
18
He flow scheme – III
(Module top view)
80% He in FW
100% He in BUs
20% He in SPs
Stage # 3:
-Breeder unit return
-Main He outlet
Main He inlet
Main He outlet
19
He thermalhydraulic performances
SP
SP
0.286
0.286 kg/s
kg/s
300°C
300°C
1.3
1.3 kg/s
kg/s
FW
FW
1.3
1.3 kg/s
kg/s
457°C
457°C
CP
CP
0.286
0.286 kg/s
kg/s
500°C
500°C
369°C
369°C
398°C
398°C
By-pass
By
By-pass
1.014
1.014 kg/s
kg/s
369°C
369°C
20
HCLL breeding blanket
PbLi flow scheme
PbLi feeding through back collector
22
PbLi flowing inside Breeder Unit
FW frontier
(FW not shown
here)
Stiffening plates (SPs) frontier
pol
rad
PbLi
tor
23
PbLi general flow scheme
Breeding zone cell
LiPb inlet
Horizontal stiffening
plate
LiPb outlet
LiPb distribution
box
Breeding zone
column
24
Main Tritium flows
HCLL Blanketmodules
mLiPb
Φ3
ΦFW
Φ1
LiPb
purification
Φ1 = tritium production rate
Φ2 = extraction rate from LiPb
Φ3 = permeation rate towards He
Φ4 = extraction rate from He
Φ5 = potential release rate
to the environment
Φ2
Pump
ηLiPb Tritium extraction
fromLiPb
GPbLi
air
Φ4
He purification
Steam
purification
generator
Φ5
ηHe
GHe
Secondary circuit
QHe
mHe
25
The HCLL TBM system integration
He circuit in vault
TBM in
port frame
PbLi circuit
in port cell
II - Safety issues
27
Safety approach for HCLL-TBM integration
Safety requirements presented in § 8 of the TBWG report are or will
be fulfilled,
Respect and application of ITER basic safety guidelines (AAG,
AAS, SADL),
Establishment of a list of potential new hazards brought by the
integration of the TBM
The identification of the SF assigned to TBM and the Safety
Important Components of the whole experimental device,
The review of the normal and abnormal operating conditions of
ITER including the HCLL-TBM,
The selection, from the operating conditions and events, of those
relevant for definition of the studies either on safety, dimensioning
or operation.
28
Coupling aspects of the approach
A general approach, both for initiating the TBM safety analysis
and defining safety design requirements, can be split into two
sub-approaches :
Investigating the influence of TBM integration on ITER
operation, availability and safety,
Investigating the impact of ITER system and operation on
TBM design, operation and safety.
29
Identification of new radioactive inventories and new
sources of hazards for the HCLL TBM
Radioactive inventory
T production in the TBM has to be quantified and Tritium outputs
have to be assessed (extraction, permeation, release)
New hazard
Exothermic chemical reaction between Pb-Li and possible released
steam (from an ITER FW failure),
New “condition”
He when spilt in the VV acts as a non-condensable gas which may
alter VVPSS performance (if triggered in case of combination of a
large FW leak and He leak).
30
HCLL-TBM SAFETY RELATED FUNCTIONS
TBM safety requirements indicate that:
Component
Safety function and
rationale for classification
Ex-vessel part of Test Blanket
components
Part of confinement barrier
Test Blanket cells
The another (second) confinement barrier
This implies that many TBM components must be safety classified:
Safety classified barriers to prevent fluid leakage or chemical interaction,
Safety classified cooling system, if failure of heat removal can threaten barriers
integrity.
31
ABNORMAL OPERATING CONDITIONS AND EVENTS
Two complementary approaches:
1. ITER events impacting the HCLL-TBM
A rea
R e fe re n c e e v e n ts
P la s m a
L o s s o f p la s m a c o n tr o l/e x c e p tio n a l p la s m a b e h a v io r
In -v e s s e l
L o s s o f v a c u u m th r o u g h a v a c u u m v e s s e l p e n e tr a tio n lin e
Power
E x -v e s s e l H T S
M a in te n a n c e
T r itiu m p la n t,
F u e l c y c le
M agnet
C r y o s ta t
H o t C e ll
L o s s o f o ff- s ite p o w e r fo r u p to 1 h
H e a t e x c h a n g e r tu b e r u p tu r e
S tu c k d iv e r to r c a s s e tte in tr a n s p o r t c a s k
M a in te n a n c e a c c id e n t o n v a c u u m v e s s e l
T r itiu m p r o c e s s lin e le a k a g e
Is o to p e s e p a r a tio n s y s te m fa ilu r e
F u e llin g lin e w ith im p a ir e d c o n fin e m e n t
N o t r e le v a n t fo r r e le a s e s , a n d n o t fo r H C L L - T B M s tu d ie s
W a te r /a ir /h e liu m in g r e s s
F a ilu r e o f c o n fin e m e n t
I : I n c id e n t
A : A c c id e n t
O ff- s ite : r e le v a n t fo r e n v ir o n m e n ta l r e le a s e s
C a t.
O f f - s it e
I, A
I
A
A
A
A
I
A
A
A
A
R
*
X
X
X
X
X
X
X
X
X
X
X
R : r e le v a n t fo r T B M - H C L L s tu d ie s
*
33
OFF-NORMAL OPERATING CONDITIONS AND
EVENTS
1.
2. HCLL-TBM events with self-impact or impacting ITER
The following methodology was developed in order to define a list of
events. Its outlines are :
Define the Initiating Event (IE), a priori equivalent to a loss of
barrier: direct (leakage) or indirect one (resulting from overheating)
for a confinement barrier (for radioactive material) or a separating
barrier (separation of 2 reactive media that could threaten
confinement barriers).
Check completeness by comparing to WCLL I.E. list (set by an
FMEA) for Pb-Li faults and to HCPB list for He faults.
Define aggravating condition that shall be combined with the PIE.
34
OFF-NORMAL OPERATING CONDITIONS AND
EVENTS
Internal faults :
AOC Loss of He pressure
He overpressure
He inventory change
Fault of He purification system
PbLi inventory change
Fault of PbLi purification system
PbLi flow change
Heating circuit fault (PbLi freezing)
LOF He flow decre ase
He circulator trip
He circulator seizure
PbLi pump seizure
Partial blockage of CP channel(s)
Partial blockage of SP channel(s)
Partial blockage of FW channel(s)
LOHS LOF of secondary circuit
Loss of final heat sink(s)
LOSP Loss of onesupply file
Total LOSP
LOC Leak of cooling plate(s)
Leak of stiffening plate(s)
Inner LOC of FW
Rupture of HX tube(s)
Faults impacting the 1st confinement :
LOC In-vessel He leakage
In-vessel PbLi leakage
Small FW break (He+PbLi)
Large FWbreak (He+PbLi)
Faults impacting the 2nd confinement :
LOC In-cryostat PbLi leakage
In cryostat He leakage
In-cryostat (He+PbLi) leakage
Ex-cryostat He leakage
Breaking of PbLi detritiation system
Breaking of PbLi purification system
Breakingof He detritiation system
Breaking of He purification system
Leak of secondary coolant
Leak of primary + secondary fluids
Required rationale for compatibility
with the ITER project selected PIE
PIE
1) Loss of
coolant into
VV
rationale
2) Loss of
coolant into
breeder/
multiplier
zone
3) Ex-vessel loss
of coolant
into port cell
(vault)
Assessment of
• small pressurisation of the first confinement
(i.e.VV)
• passive removal of decay heat
• Limited chemical reactions and hydrogen
formation
• pressurisation of the module and purge gas
sysstem.
• Limited chemical reactions and hydrogen
formation
• subsequent in-vessel leakage
• pressurisation of the port cell, vault, assembly
cask
Limited
chemical reactions and hydrogen
•
formation
35
HCLL TBM safety issues status
Parameters to be assessed
(asked by ITER-IT )
Pressurization in:
vault
Port Cell
CCWS
TBM box
(breeder)
HCLL TBM status
When accurate He circuit volume
will be determined
In progress (see next slides)
Passive decay heat removal
In progress (see next slides)
PbLi limited to 0.28 m3
OK for in TBM volume, provisions
for outside volume have TBD
FMEA studies to confirm I.E. list
Rationale for PIE selection
In progress
In progress
36
TBM thermal-mechanical results
1. Decay heat removal
2. In-TBM LOCA and box pressurization
3. LOFA
37
Decay heat removal by thermal radiation (1/3)
Heat flux / Be layer : 0.5 MW.m-2
Thermal emissivity Be layer : 0.61
Thermal emissivity ITER wall : 0.3
Temperature ITER wall : 413 K
Be layer : boundary conditions
Power density profile versus distance from
the plasma (NWL 0.78) :
• Be : 5.2 MW.m-3
• FW : 5.4 MW.m-3 (0.69 kW.kg-1)
• SW : red curve
• CP : blue curve
• SPV : green curve
• PbLi : pink curve (10 MW.m-3 0.98 kW.kg-1)
TBM-HCLL : Thermal loads
38
Several hypothesis :
• decay heat Eurofer no impurities
• decay heat Eurofer impurities
• decay heat LiPb no impurities
• decay heat LiPb impurities (with or without Tritium)
Lipb
1,E+00
1,E+00
1,E-01
1,E-02
1,E-03
1,E-04
1,E-05
1,E-06
1,E-07
1,E-08
1,E-09
1,E-10
1,E-11
1,E+00
1,E+02
1,E+04
1,E+06
1,E+08
1,E+10
1,E-01
1,E-02
1,E-03
front
mid
rear
decay heat kW/kg
heat decay kW/kg
1,E+00 1,E+03 1,E+06 1,E+09 1,E+12
1,E-04
1,E-05
front
mid
rear
1,E-06
1,E-07
1,E-08
1,E-09
1,E-10
1,E-11
time (seconds)
1,E-12
TBM decay heat
time after shutdown (s)
39
He in-vessel LOCA
- Helium leak stops immediately the plasma so that the surface heat flux and the
nuclear power density drop to zero,
- There is no cooling by He.
t1
FW temp.
t2
t1 : T max. = 563°C
t1 + 1 sec. :
T max. = 541°C
t2 : T max. = 426°C
40
TBM box pressurization (in TBM LOCA)
Thermomechanical calculation of the module
at 8.0 MPa .
41
Loss of Flow Accidents
Under some conditions LOFAs
could avoid to end up in a LOCA.
555 °C ≤ T ≤ 1100 °C
Plasma
side
Automatic shut-down
t = 35 sec. – T max. = 1100 °C
End of simulation
t = 135 sec. – T max. = 692 °C
Beginning of LOFA
t = 0 sec. – T max. = 559 °C
42
III - Occupational exposure
The contribution of the TBM to occupational exposure during
operation was estimated taking into account the ALARA
principle, with the objective of minimizing such exposure:
• Dose rate was estimated for TBM structural material
(EUROFER) and for Liquid Breeder (Pb-Li).
• Dose rate was estimated with and without bioshield
protection – the attenuation is quite significant (926 mSv/hr
at 1 year without shield and 1.26E-09 mSv/hr with shield).
• Review of this analysis has to be performed considering the
new operating scenarios and design (new neutronics data).
• Dose rate during maintenance activities still to be done.
43
IV – Conclusion
HCLL TBM safety does not show any critical issue,
All TBM events are covered by ITER accidental situations,
He inventory is small and not able to pressurize ITER
confinement volumes,
Pb-Li inventory is limited and reaction with steam in hypothetical
situations cannot produce more than 2.5 kg of hydrogen,
Combined ITER + TBM sequences have to be assessed in order
to estimate safety systems performance with mixed medias as:
steam, He, Pb-Li.
44

Safety issues review of the EU HCLL ITER TBM

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