GIF , HTR

GIF , HTR
Prof. Wolfgang Kröger
((http://www.riskcenter.ethz.ch,
p
, [email protected])
g @
)
Generation IV Initiative – Aims (1/2)
Nuclear energy-systems including fuel cycles of the 4th
generation should ...
SR-1 ... be excellent regarding
g
g safety
y and reliability
y while in
operation.
SR-2 ... have very low core damage frequency and little
consequences.
consequences
SR-3 ... eliminate the need for emergency planning outside of
the plant.
p
EC-1 ... clear lifecycle-cost advantages over other energy
sources.
EC-2 ... comparable financial risk to other energy projects.
Spring 2012 / Prof. W. Kröger
Safety of Nuclear Power Plants
2
Generation IV Initiative – Aims (2/2)
Nuclear energy
energy-systems
systems including fuel cycles of the 4th generation
should ...
SU-l ... produce sustainable energy, following regulations for air
pollution prevention and enhancing the long term availability
of the system and efficient usage of fuel.
SU-2
... minimise the nuclear waste and disposing it, especially they
will reduce administration efforts on a long term scale and
hence improve the protection of health and environment
environment.
SU-3
... increase the certainty that they are an undesirable and
difficult source to obtain dangerous materials for usage in
weapons.
Spring 2012 / Prof. W. Kröger
Safety of Nuclear Power Plants
3
Selected Generation IV Concepts (out of 21)
GEN IV Concepts
Sodium Cooled Fast
L d All
Lead
Alloy-Cooled
C l d
Gas-Cooled Fast
Very High Temperature
Supercritical Water Cooled
Molten Salt
Spring 2012 / Prof. W. Kröger
Acronym Spectrum Fuel cycle
Pressure
SFR
LFR
GFR
VHTR
SCWR
MSR
Fast
F t
Fast
Fast
Thermal
Th.&Fast
Thermal
Closed
Cl
Closed
d
Closed
Once-Through
Once/Closed
Closed
Safety of Nuclear Power Plants
Temperature
[°C]
530-550
550 800
550-800
490-850
640-1000
280-510
280
510
565-850
[bar]
1
1
90
70
250
<5
4
VHTR - Technology gaps
Process-specific R&D gaps exist to adapt the chemical process and the nuclear
heat source Qualification of high-temperature alloys and coatings.
Performance issues include
development of a highperformance helium turbine.
Modularization of the reactor
and heat utilization systems is
another challenge for
commercial deployment of
the VHTR.
Spring 2012 / Prof. W. Kröger
Safety of Nuclear Power Plants
5
Concept of a modular HTR (1/3)
Fuel element and restraining the fission products up to 1600°C
Fuel element
SiC
coating
Graphite
10,000 to
20,000 coated particles
Spring 2012 / Prof. W. Kröger
Safety of Nuclear Power Plants
6
Concept of a modular HTR (2/3)
15
11
feedwater
12
5
steam
10
9
2
3
8
1
7
to the
filter
G
13
16
Spring 2012 / Prof. W. Kröger
M
4
6
 Thermal power 300MW
 Circular core
 Pre-stressed primary loop as an
burst prove inclusion
 Interior concrete cell with a
limitation on air amount
 Underground
U d
d arrangementt off th
the
reactor building
 Use of the primary loop to steam
production, gas turbines and
process heat applications (with inbetween heat exchanger)
14
Safety of Nuclear Power Plants
7
Concept of a modular HTR (3/3)
Underground arrangement of the reactor
18
20
15
0
0
19
12
11
5
10
Speisewasser
9
3
Frischdampf
8
2
7
17
1
G
14
M
16
Spring 2012 / Prof. W. Kröger
13
4
Safety of Nuclear Power Plants
6
8
Accident behaviour of a modular HTR (1/10)
Accident assumptions
internal
Causes
• Full loss of coolant
• Full loss of the active residual heat
removal
• Massive water ingress into the
primary system
• Massive air ingress into the primary
system
external
Causes
external
causes
(beyond
licensing)
• Crash of a plane
(Phantom)
• Terrorist attacks with
planes (Boeing 747)
• Gas cloud explosion
• Sabotage
• Earthquake (b < 0,3 g)
• Impacts of war (missiles)
• Fire
• Extreme earthquakes
(b > 0,3 g)
• Tornados, hurricanes
and floods
• Meteorites
• Extreme reactivity disturbances
• Massive damage of reactor
components
Spring 2012 Prof. W. Kröger
Safety of Nuclear Power Plants
9
Accident behaviour of a modular HTR (2/10)
Stabilitätsprinzip
nichtschmelzbare Brennelemente und
Corestrukturen
nukleare
Stabilität
selbsttätige Begrenzung von nuklearer
Leistung und Brennstofftemperaturen
thermische
Stabilität
selbsttätige Nachwärmeabfuhr aus
dem Reaktorsystem
chemische
Stabilität
selbsttätiger
g Schutz
gegen Korrosion
mechanische
Stabilität
Spring 2012 / Prof. W. Kröger
Wirkung
selbsttätiger Schutz
gegen mechanische
C
Corezerstörung
tö
Requirements for a non melting
inherent safe modular HTR
 Fulfilment of the principles for all
accidents
id t d
due tto iinternal
t
l and
d
foreseeable external cause
(requirements from licensing)
 Fulfilment of the principles for all
accidents including
unforeseeable occurrences such
as terrorist attacks or extreme
earthquakes
Accident behaviour of a modular HTR (3/10)
Automatic removal of the residual
heat in the case of failing of all
active heat removal (for example:
PBMR, additionally the total failure
of the first shut down system was
assumed)
max
T Brennst. (°C)
1600
1400
1200
1000
800
max
600
TBrennst.
400
TBrennst.
Brennst
200
0
Zeit (h)
0
20
Spring 2012 / Prof. W. Kröger
40
60
80
100
120
 Fuel elements can never melt
 Maximum fuel temperature
remains below 1600°C
 Most fuel elements stayy far
below this temperature
 Total fission product release
stays below 10-5 of the inventory
Accident behaviour of a modular HTR (4/10)
Biological
g
analogue
g for the automatic residual heat removal and
limitation of accident temperature
Tmax < 1600 °C
C
QN
Tw
Tmax < 38 °C
< 400 °C
QN  a  A ( Tw - Tu)
Q
Tmax - To  QN /H
4c
Tmax
QN  600 kW
To
Tw
Tu
Spring 2012 / Prof. W. Kröger
Safety of Nuclear Power Plants
< 37 °C
Q  a  A ( To - Tu)
Tmax - To  Q/H
4 i
Tmax
(entspricht der Nachwärme
eines Cores mit Pth = 300 MW
nach etwa 30 h )
To
To
Tu
Q  60 W
(entspricht der Wärmeabgabe
eines Menschen unter
“normalen” Bedingungen)
12
Accident behaviour of a modular HTR (5/10)
New safety requirements for
nuclear technology
105 t
K (t)
1,1 10 4 t
zukünftige
Annahmen
Flamment
temperatur
t
(°C)
max 1200 °C
max.
C
zukünftige
Annahmen
heutige
Annahmen
heutige
Annahmen
800 °C
t
Schutz der Gebäude gegen
Penetration und Zerstörung
Spring 2012/ Prof. W. Kröger
0
30 min
2h
t
Schutz gegen langandauernde
Flammeneinwirkungen mit hohen
Temperaturen bei Kerosinbrand
Safety of Nuclear Power Plants
13
Accident behaviour of a modular HTR (6/10)
Reaktor
Bauschutt
(mit Isolationswirkung)
T (°C)
1500
Core (maximum)
1000
Reaktordruckbehälter
500
Behälter zu 60% isoliert
B hält zu 99% iisoliert
Behälter
li t
0
0
20 40 60 80 100 120 140 160 180 200 220 240
Zeit (h)
Spring 2012 / Prof. W. Kröger
Automatic removal of the residual
h t after
heat
ft the
th destruction
d t ti off the
th
reactor building (for example caused
by an extreme earthquake or a
plane
l
crash
h caused
db
by tterrorists)
i t )
 Reactor totallyy covered with
rumble
 Residual heat is still removed
automatically,
au
o a ca y, but
bu sslowed
o ed do
down
 Maximum fuel temperature stays
below 1600°C
 Total fission product release
stays below 10-5 of the inventory
Safety of Nuclear Power Plants
14
Accident behaviour of a modular HTR (7/10)
P/PO 6000
(%)
0.1 s
1.0 s
4000
Leistung des
Reaktors
10 0 s
10.0
2000
t/s
0
0
10
20
 Strongly negative temperature
coefficient ends the excursion
 Transient heat is quickly and for
the most part stored in the ffuel
el
element graphite
 Maximum fuel temperature stays
b l
below
1600°C
TB 1300
(°C)
1200
1100
0.1 s
1000
1.0 s
10.0 s
900
Brennelementtemperatur
800
Automatic limitation of nuclear
power and fuel temperature when
faced with extreme reactivity
transient (total loss of the first shut
down system: ρ = 1,2 % in a short
period of time)
700
t/s
0
Spring 2012 / Prof. W. Kröger
10
20
Safety of Nuclear Power Plants
15
Accident behaviour of a modular HTR (8/10)
Concepts for minimising the
consequences of an air ingress
accident:
Vluft  5000m3
Granulat
6
8

1

2
4
5
3
7
1)
Internal concrete cell (sealed against outside air)
2))
Reactor building
g
3)
Draining channel
4)
Sealing flaps (gravity)
5)
Sealing plug
6))
G
Granulate
silo
7)
Filter
8)
Flue
Spring 2012 / Prof. W. Kröger


Draining the primary Helium
g p
pipes
p over a filter
through
Automatic limitation on the amount
of air within the concrete cell (V <
5000 m3) by automatic closing
mechanisms (flaps and pouring
granulate)
Limitation of possible graphite
g C and
corrosion to < 500 kg
therefore no radiological
consequences
Limitation of possible graphite
corrosion to < 100 kg by simple
intervention methods (protection of
investment)
Safety of Nuclear Power Plants
16
Accident behaviour of a modular HTR (9/10)
Begrenzung
der Menge
an Luft
Begrenzung
der Mengenrate an
Luft
Verhine
derung der
Korrosion
von Brennelementen
 Volumen der inneren
Betonzelle ist begrenzt
(<5000m³)
 Vorgespannter ReaktorReaktor
druckbehälter mit
kleinen Öffnungen
 Korrosionsbeständige
SiC-beschichtete
Brennelemente
 nach erfolgter Druckentlastung schließt eine
Klappe oder ein Granulatvorrat den Kanal ab
 Berst-Schutz für
di B
die
Behälter
hält
 innere Betonzelle
ist mit Inergas
gefüllt
 innere Betonzelle wird
mit Inertgas gefüllt
Spring 2012 / Prof. W. Kröger
 Intervention in
innerer Betonzelle
Safety of Nuclear Power Plants
17
Accident behaviour of a modular HTR (10/10)
Comparison of the fuel behaviour after loss of the active residual heat removal.
PWR
5
~
HTR
Brennstofftemperatur
TB
(°C)
1Ci
~<
Partikel
Tmelt =
2850 °C
10 Ci
Brennstab
Zr
ZrCanning
0
S
Brennstofft
temperatur
t
<1600 °C
UO2-Kern
TC ~
600°C
UO2Tablette
TB
C
1h
SiC
t
Schäden an den
B
Brennelementen
l
t
30 h
t
C
C Matrix
S
Schäden an den
Brennelementen
1
-5
10
1h
Spring 2012 / Prof. W. Kröger
t
30 h
Safety of Nuclear Power Plants
t
18
Total Assessment of Safety (1/2)
Integral proof of safety behaviour
elektrische
Widerstandsheizung
Spring 2012 / Prof. W. Kröger
 Simulation of the residual heat in a
graphite-sphere-pile
hit
h
il b
by electrical
l ti l
resistance heating. (~ 2 MW for a 300
MWth - Core)
 Analysis of all assumable accidents
(total loss of coolant, air ingress,
water ingress, pressure discharge,
mechanical impacts on the elements
of the shut down system, component
damage when pressure relief)
 Validation of all calculating programs
for extreme accidents (heat transfer
throughout all structures, flow
phenomena, acts of pressure
discharge).
Safety of Nuclear Power Plants
19
Total Assessment of Safety (2/2)







Fuel elements can never melt; there is no heating up of the fuel elements to a
temperature above 1600°C
The principal of automatic residual heat removal can never fail, even after the
destruction of the reactor building it stays intact.
Th reactor
The
t would
ld even stay
t resistant
i t t against
i t extreme
t
reactivity
ti it transient.
t
i t
There is no temperature raise of the fuel elements to above 1600°C
The pre-stressed reactor containment can not burst; It is impossible that an
unacceptable
p
amount of air enters the p
primary
y loop,
p g
graphite
p
corrosion is
minimal.
The ingress of larger amounts of water into the primary loop will not lead to
unacceptable states of the reactor; in the case of gas turbines operating this
accident is not applicable.
Against extreme, in future even more severe external impacts, the
underground way of building with covering mound, and fast removal of
spherical fuel elements as protection
Th
There
iis no accident
id t iin which
hi h case a significant
i ifi
t amountt off radiation
di ti iis released
l
d
Spring 2012/ Prof. W. Kröger
Safety of Nuclear Power Plants
20