Design Study for Passive Shutdown System of the PGSFR

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1 Design Study for Passive Shutdown System of the PGSFR Lee, Jae-Han Koo, Gyeong-Hoi IAEA TM on passive shutdown system 1

2 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 Drive Motor Electromagnet [EM] 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 Seal Bellows Eq. Diameter = 158 cm Inner core F.A. 52 Outer core F.A. 60 Primary control rod 6 Secondary control rod 3 Reflector 78 B4C shield 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 Eq. Diameter = 253 cm IAEA TM on passive shutdown system 2 Bushing Electro- Magnetic gripper, SASS 313

3 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) Sodium level Materials Components Electromagnet cores / armature Thermal expansion device Drive shaft corresponding to the thermal expansion device Materials SS410 or soft iron / SS410 or 2.25Cr- 1Mo SS316 9Cr-1Mo-V or Inconel 718 Thermal Expansion device Coil enclosure structure Armature Drive Shaft Electro magnet Control rod assembly (CRA) head Flow guide structure IAEA TM on passive shutdown system 3

4 3. Basic Actuation Concepts of Passive Shutdown System Use of thermal expansion differences Behaviors at three situations Fabrication, 25 o C Operating condition, ~ 545 o C One of ATWS conditions, ~ 650 o C 25 o C ~ 545 o C ~ 650 o C Drive Shaft (Inconel 718) Thermal expansion device (SS316) Drive shaft (9Cr-1Mo-V (Inconel718)) Thermal Expansion device (SS316) ~ 9.7 mm Electro Electro magnet magnet ~ 0.8 mm Electro magnet Gap size, ~ 1 mm Electro magnet Thermal Thermal Thermal Thermal Temp [ o Expansion Conductivity Expansion Conductivity C] [10-6 mm/mm/ o C] [W/(m o C)] [10-6 mm/mm/ o C] [W/(m o C)] Magnet flux gap CRA head (14.13) 27.9(17.7) (14.4) 27.9(19.4) (14.9) 27.5(21.2) 1.8 mm = (~ 6.0 x 10-6 / o C) x ( 105 o C) x (~2.86 m) 9.0 mm = (~ 6.0 x 10-6 / o C) x ( 520 o C) x (~ IAEA TM on passive shutdown system 4 m)

5 4. Design Conditions of Passive Shutdown System Initial design values for building up the design concept Design conditions Weight of secondary control rod assembly (CRA) Temperature rising range Targets ~ 50Kg 100 ~ 150 o C Drive Motor Seal Bellows Thermal Expansion Device Coil enclosure Structure (option) CRA release Gap size to the armature Maximum electromagnetic force ~ 1 mm (TBD) < 300 N Bushing Drive Shaft Allowable length of thermal expansion device ~ 3.0 m (TBD) Electromagnet Gripper 2nd CRA (~50 Kg) IAEA TM on passive shutdown system 5 Electro- Magnet gripper

5. Design Issues of Passive Shutdown System Installation space of electromagnet Limited diameter => Limited

environments Core material of electromagnet Permeability Coil insulation Insulation materials and methods Coil

head contact rod through a central hole in electromagnet Electrical way using an eddy current Diameter, 100 mm

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(545 o C) and radiation environments Core material of electromagnet Permeability Coil insulation Insulation materials and methods Coil design life Drive Motor Seal Bellows 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 IAEA TM on passive shutdown system 6 Bushing Electro- Magnetic gripper Length of thermal expansion device Drop height

6. Electromagnet Designs of Passive Shutdown System Two

interspaces mineral (M g O) insulation and seamless SS316

structure weld seal at gaps of the electromagnet cores Size

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 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 (M g O) insulation and seamless SS316 sheath Type 1 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 Type IAEA TM on passive shutdown system 7

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.

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. Thermal Expansion Device Coil enclosure structure Outer core Coils Inner core Armature 2nd CRA head Redan IAEA TM on passive shutdown system 8

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. Table 5 Electromagnet forces induced by design variations Gap size between fixed core and armature Electromagnet Inner core Inner diameter Outer diameter Electromagnet armature Thickness Coil (6 layers) Axial length Ampere turns Force mm mm mm mm mm AT N x x x x * x x x x x x Table 6 Electromagnet forces for magnetic core thicknesses Gap size between fixed core and armature Electromagnet Inner core thickness Outer core thickness IAEA TM on passive shutdown system 9 Coil space Coil Layer no Ampere turns Force mm mm mm mm AT N x * x x x x

9. Calculation of Electromagnetic Force (Type 2) Design parameters of

25~ 2 mm Different core materials Fixed values Outer core outside

No coil enclosure structure The role is replaced with the sealed outer

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 Thermal expansion device Outer core enclosure coils Coils Power supply DC ~ 15V, 7.5 A 1,980 AT Calculation software ANSYS Emag. Inner core (inside) Armature 2nd CRA head IAEA TM on passive shutdown system 10

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

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 The electromagnetic forces on the CRA within 0.5 mm gap are strong enough to hold the CRA. Magnetic force (N) Low carbon & SS deg.(lc 10 mm)" Soft iron & 2.25Cr-1Mo (Lc 10 mm) The electromagnetic forces with 1 mm 500 gap are in the range of ~ 300 N, it makes the CRA drop into the reactor Gap size between fixed magnet and armature (mm) core by gravity. Figure 4 Electromagnetic force variations to air gap size to the armature IAEA TM on passive shutdown system 11

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 100 o C. 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 ( ~ 650 o C). 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 IAEA TM on passive shutdown system 12

A1. Design feasibility tests for Electromagnets Type 1 Design

size 1 ~ 0 mm 20 ~ 260 kgf Type 2 Design Use of mineral

~ 240 kgf Thermal Expansion Device Electro- Magnet Coated

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 Thermal Expansion Device Electro- Magnet Coated coil 2nd CRA head MI coil IAEA TM on passive shutdown system 13

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.

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 ( o C) CRA weight variations IAEA TM on passive shutdown system 14

15 Thanks for your attention! IAEA TM on passive shutdown system 15

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