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20151021 IAEA TM on passive shutdown system 1
Design Study for Passive Shutdown System of the PGSFR
2015. 10. 20
Lee, Jae-Han
Koo, Gyeong-Hoi
20151021 IAEA TM on passive shutdown system 2
Eq. Diameter = 253 cm
Eq. Diameter = 158 cm
Secondary control rod
Primary control rod
Reflector
B4C shield
6
3
78
114
Outer core F.A. 60
Inner core F.A. 52
313
1. Reactor Control and Shutdown Concepts of PGSFR
6 Primary CRDMs – Start up, power control and reactivity
compensation through the CRA’s position movement driven by AC servo motor
– Shutdowns • Normal shutdown – Plant Control System Rod insertion by AC servo motor
• Scram – Reactor Protection System, RPS Rod insertion by gravity (EM power off)
and then the insertion confirmed by fast drive-in motor
3 Secondary CRDMs – Scram – RPS
• 1 : Rod insertion by gravity (EM power off) and confirmed by fast drive-in motor
– Passive shutdown function of relaxing ATWS • Use of thermal expansion difference of two
metals, when the coolant temperature rises up at certain level
Electro-magnet [EM]
Dri
ve M
oto
r
Seal B
ellow
s
Bushin
g
Ele
ctr
o-
Magnetic g
ripper,
SA
SS
20151021 IAEA TM on passive shutdown system 3
Sodium level
Thermal Expansion device
Flow guide structure
Electromagnet
Driv
e S
haft
Control rod assembly (CRA) head
Armature
2. Components and Materials of Passive Shutdown System
System components
– Electromagnet, which is attached to the bottom end of CRA driveline, to hold or trigger off the CRA
– Armature, attached to the top of the CRA extension rod head – Thermal expansion device (structure), material of a relatively large
thermal expansion coefficient – Coil enclosure structure for protecting the coil from hot sodium – Flow guide structure supported by upper internal structure (UIS)
Materials
Components Materials
Electromagnet cores / armature
SS410 or soft iron / SS410 or 2.25Cr-1Mo
Thermal expansion device SS316
Drive shaft corresponding to the thermal expansion device
9Cr-1Mo-V or Inconel 718
Coil enclosure structure
20151021 IAEA TM on passive shutdown system 4
3. Basic Actuation Concepts of Passive Shutdown System
Thermal expansion device (SS316)
Drive shaft (9Cr-1Mo-V (Inconel718))
Temp [oC]
Thermal Expansion
[10-6 mm/mm/oC]
Thermal Conductivity [W/(moC)]
Thermal Expansion
[10-6 mm/mm/oC]
Thermal Conductivity [W/(moC)]
425 19.6 20.1 13.4(14.13) 27.9(17.7)
525 20.4 21.5 14.0(14.4) 27.9(19.4)
625 21.4 22.9 14.9(14.9) 27.5(21.2)
1.8 mm = (~ 6.0 x 10-6 /oC) x ( 105oC) x (~2.86
m)
9.0 mm = (~ 6.0 x 10-6 /oC) x ( 520oC) x (~2.86
m)
Use of thermal expansion differences
– Behaviors at three situations • Fabrication, 25oC • Operating condition, ~ 545oC • One of ATWS conditions, ~ 650oC
Thermal Expansion device (SS316)
Electromagnet
CRA head
Magnet flux gap
~ 9.7 mm
Driv
e S
haft (In
conel 7
18)
Electromagnet
~ 0.8 mm
Electromagnet Gap size,
~ 1 mm
Electromagnet
25oC ~ 545oC ~ 650oC
20151021 IAEA TM on passive shutdown system 5
4. Design Conditions of Passive Shutdown System
Design conditions Targets
Weight of secondary control rod assembly (CRA)
~ 50Kg
CRA release
Temperature rising range
100 ~ 150oC
Gap size to the armature
~ 1 mm (TBD)
Maximum electromagnetic force
< 300 N
Allowable length of thermal expansion device
~ 3.0 m (TBD)
Thermal Expansion Device
Drive Shaft
2nd CRA (~50 Kg)
Coil enclosure Structure (option)
Electro- magnet Gripper
Dri
ve M
oto
r
Seal B
ellow
s
Bushin
g
Ele
ctr
o-
Magnet
gri
pper
Initial design values for building up the design concept
20151021 IAEA TM on passive shutdown system 6
5. Design Issues of Passive Shutdown System
Installation space of electromagnet
– Limited diameter => Limited electromagnetic force – Limited length of thermal expansion device
High temperature(545oC) and radiation environments
– Core material of electromagnet • Permeability
– Coil insulation • Insulation materials and methods • Coil design life
Layout of DC power line
– Length : ~ 12 m
Monitoring the CRA release
– CRA head contact rod through a central hole in electromagnet
– Electrical way using an eddy current
Diameter, 100 mm
Dri
ve M
oto
r
Seal B
ellow
s
Bushin
g
Ele
ctr
o-
Magnetic g
ripper
Dro
p he
ight
Leng
th o
f th
erm
al e
xpan
sion
dev
ice
20151021 IAEA TM on passive shutdown system 7
6. Electromagnet Designs of Passive Shutdown System
Two design types are studied, Type 1
is an initial design, Type 2 is an
improved design concept.
Type 1
Type 2
Type 1 Type 2
Coil wire (Cu) rectangular, 4~ 6 layers, 2 x 6 mm 2
circular, 1.4 mm in diameter
Coil insulation materials
fiber glass in interspaces
mineral (MgO) insulation and seamless SS316 sheath
Coil seal from sodium
SS316 enclosure structure
weld seal at gaps of the electromagnet cores
Size of coil enclosure structure
OD : 80 mm, thickness : ~ 2 mm
Size of outside core
OD : 75 mm OD : 80 mm
20151021 IAEA TM on passive shutdown system 8
7. Calculation of Electromagnetic Force (Type 1)
Design parameters of electromagnets
• Gap size between the electromagnet core and the armature of the CRA head, 0.5 ~ 3 mm
• Size of the electromagnet core,
Length, 200 ~ 300 mm
Thickness of cores
• No. of coil turns, 100 ~ 320 turns
• Fixed value
Outer core outside diameter : 75 mm
Power supply • DC ~ 6V, 17A ~ 20A
• ~ 3,200 Ampere Turns
Calculation software • ANSYS Emag.
2nd CRA head
Thermal Expansion Device
Coils
Inner core
Outer core
Armature
Coil enclosure structure
Redan
20151021 IAEA TM on passive shutdown system 9
8. Electromagnetic Forces on CRA head (Type 1)
The electromagnet forces on the CRA head are
calculated by changing the design parameters.
The electromagnetic forces on the CRA with 1
mm gap and the 160 coil turns are in the range
of ~ 250 N for the several core thicknesses.
The results in Table 6 show that the increase of
the core thickness is proportional to the
electromagnetic force even if the ampere turns
are decreased in the certain range.
Gap size between
fixed core and
armature
Electromagnet Inner core
Electromagnet armature Coil (6 layers)
Inner diameter
Outer diameter Thickness Axial
length Ampere turns Force
mm mm mm mm mm AT N 1 15 27 20 185 17x 160 177 1 11 27 20 185 17x 160 217 1 9 27 20 185 17x 160 231 1 5 27 20 185 17x 160 251* 1 5 27 10 385 17x 320 290 1 5 27 10 185 17x 160 245 1 5 27 10 185 17x 220 463 2 5 27 20 185 17x 160 86 3 5 27 20 185 17x 160 48
0.5 5 27 20 185 17x 160 490
Gap size between
fixed core and armature
Electromagnet Coil
Inner core thickness
Outer core thickness
Coil space
Layer no
Ampere turns Force
mm mm mm mm AT N 1 12 4 19.5 6 20x150 253* 1 14 5 16.5 5 20x125 310 1 17.5 5.5 12.5 4 20x100 384 1 17.5 5.5 12.5 5 20x125 456 1 17.5 5.5 12.5 5 25x125 532
Table 6 Electromagnet forces for magnetic core thicknesses
Table 5 Electromagnet forces induced by design variations
20151021 IAEA TM on passive shutdown system 10
9. Calculation of Electromagnetic Force (Type 2)
Design parameters of electromagnet
• Gap size variations to the armature : 0.25~ 2 mm • Different core materials
• Fixed values
Outer core outside diameter : 80 mm, thickness : 3 mm, length : ~ 300 mm Coil turns : 264
• No coil enclosure structure
The role is replaced with the sealed outer and lower cores
Power supply
• DC ~ 15V, 7.5 A
• 1,980 AT
Calculation software • ANSYS Emag.
2nd CRA head
Thermal expansion device
Coils
Inner core (inside)
Outer core enclosure coils
Armature
20151021 IAEA TM on passive shutdown system 11
10. Electromagnetic Forces on CRA head (Type 2)
The electromagnetic forces on the CRA
head are calculated when the outer core
outside diameter is enlarged to 80 mm,
and the calculated results for the
different core materials and the gap size
variations to the armature are suggested
in Figure 4.
The electromagnetic forces on the CRA
within 0.5 mm gap are strong enough to
hold the CRA.
The electromagnetic forces with 1 mm
gap are in the range of ~ 300 N, it
makes the CRA drop into the reactor
core by gravity.
0
500
1000
1500
2000
2500
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2
Mag
netic
forc
e (N
)
Gap size between fixed magnet and armature (mm)
Low carbon & SS410 25 deg.(Lc 10 mm)"
Soft iron & 2.25Cr-1Mo (Lc 10 mm)
Figure 4 Electromagnetic force variations to air gap size to the armature
20151021 IAEA TM on passive shutdown system 12
11. Summary
The thermal expansion difference of the 2.86 m long expansion device
is calculated about 1.7 mm for the temperature rise of 100oC.
The electromagnetic forces on the CRA with 1 mm gap are in the range
of ~ 300 N.
The thermal expansion difference of the thermal expansion device to
trigger off the CRA shall be controlled within 1 mm at a set
temperature ( ~ 650oC).
Additional design study to trigger off the CRA by utilizing the limited
length of thermal expansion device is going on.
The design feasibility tests for a passive shutdown concept of the
PGSFR are being performed by using several test mockups of the
thermal expansion device.
20151021 IAEA TM on passive shutdown system 13
A1. Design feasibility tests for Electromagnets
Type 1 Design
– Use of rectangular coated coil
– Electromagnet forces for gap size 1 ~ 0 mm
• 20 ~ 260 kgf
Type 2 Design
– Use of mineral insulation coil
– Electromagnet forces for gap size 1 ~ 0 mm
• 20 ~ 240 kgf
2nd CRA
head
Thermal
Expansion
Device
Coated
coil
Electro-
Magnet
MI coil
20151021 IAEA TM on passive shutdown system 14
A2. Design feasibility tests for passive shutdown device
Under the fabrication of a
medium size test facility
• Type 2 design
• Use of shorten thermal
expansion device : 0.7 m
• Initial position of expansion
device
Passive Function tests
• CRA drop test for
temperature 600 ~ 650 (oC)
• CRA weight variations