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

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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

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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

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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

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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

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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

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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

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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

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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

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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.

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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

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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

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Thanks for your attention !