drilling machine3.pdf

8/9/2019 drilling machine3.pdf

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22 Aug. 2012

J.T. Hong, S.H. Ahn, H.Y. Jeong, C.Y. Joung

Neutron Utilization Technology Division, KAERI

Development of a drilling machine

for the instrumentation of thermocouple in a

fuel pellet


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Establishment of HANARO and FTL

Feb.,1995

March,2009

Enhance researchequipments

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Fuel Test Loop Facility (1/3)

Schematics of FTL

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Applications

Fuel & material irradiation test under the same condition with

NPPs steady state operating condition

Integral Fuel Irradiation Tests

Fuel Qualification Tests

High Burn-up Fuel Tests

Water Chemistry and Corrosion TestsNon-fissile Tests of Pressure Tube Material

In-Pile SectionDesign Pressure : 17.5 MPa

Design Temperature : 350

Out-Pile System


In-Pile test Section

Out-of-Pile System(Room#1)

Out-of-Pile System(Room#2)

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Outer Pressure Vessel

Inner Pressure Vessel

Test Fuel Carrier Leg

Flow Divider

Insulation Gas Gap

Test Fuel

Downward Flow Path

Upward Flow Path

A-A

IPS Head

Outlet Nozzle

Intlet Nozzle

Fuel Carrier Head

Test Fuel

Flow Divider

AA

Fuel Carrier Leg

Inner Pressure

VesselOuter PressureVessel




Flow Divider

Insulation Gas Gap

Test Fuel

Downward Flow Path

Upward Flow Path

A-A




Flow Divider

Insulation Gas Gap

Test Fuel

Downward Flow Path

Upward Flow Path




Flow Divider

Insulation Gas Gap

Test Fuel

Downward Flow Path

Upward Flow Path

A-A

IPS Head

Outl

et Nozzle

Intlet Nozzle

Fuel Carrier Head

Test Fuel

Flow Divider

AA

Fuel Carrier Leg

Inner Pressure


IPS Head

Outl

et Nozzle

Intlet Nozzle

Fuel Carrier Head

Test Fuel

Flow Divider

AA

Fuel Carrier Leg

Inner Pressure


Outlet

Nozzle

InletNozzle

Test

Fuels

Loaded in IR-1 irradiation hole of HANARO

Doubly sealed pressure vesselMax. available fuel pin: 3 pieces


Doubly sealedPressure vessel

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Necessity of drilling a hole on a UO2 pellet

(1) Specification

- Diameter 8.190.01mm- Height 9.83mm

(2) Material Characteristics

- Density 10.19g/cm3

- Hardness 700Hv (HRC 61)- Yield stress 370MPa

(3) Hole drilling :

- Diameter 0.7~1.4mm (0.05)- Depth 0~12mm (0.1)

Section view of the fuel rod Characteristics of sintered UO2pellet

UO2

Al2O3

LVDT

Thermocouple

Characteristics of sintered Al2O3

(1) Material Characteristics

- Purity 99.7%

- Density 3.92g/cm3

- Hardness 1480Hv

- Yield stress 172MPa

Al2O3

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Decision of hole diameter

Diameter of thermocouple

D

General tolerance for assembly including shrinkage during irradiation test : 0.2mm

Hole Dia. for C-type T/C Hole Dia. for K-type T/C

1.40.05 0.70.05

14.18.192

Diameter

C-type 1.2mm

K-type 0.5mm

9.6

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Thermal analysis of a fuel rod

Thermocouple

UO2 pellet

Alumina

Clad

He gas

Analysis tool ABAQUS 6.11

FE Analysis Axisymmetric

Initial condition 25

Boundary condition 305

Heat generation atUO2pellet

789.056 mJ/secmm3

Modeling of fuel rod mockup Result of thermal analysis

r (mm)

Temperature

()

L

0.7mm

(Hole radius)

Distribution of temperature in the fuel rod

CladHe

T:120

z

r

C

Compensation of temperature difference due to the hole in the fuel pellet

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Previous study of drilling machine

[Old study, 1999, Kim. et al, KAERI]

Feeding of drill bit Horizontal

Drill tipFlat type

(Electro-deposited diamond)

Drilling time 3 hours (net)

Change of drill bit 3 times/hole

Frequently change of drill bit due to the severe wear of drill tip during drilling process

Long working time

: Drilling time + Change drill bit + Adjust tool position

Spec out (1.400.05) due to large run out (61.5m)

: Diameter of the drill tip (1.4) Diameter of drilled hole (1.362 - 1.523)

Need to develop a new drilling machine

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Drill tip

Diamond coating (CVD)

Drill tip

118

Selection of drill bit for UO2pellet

Large cutting resistance, severe tool wear

Chips are trapped in the drilling hole

Tooling time per hole : 3hr (net)

Change of drill bit per hole : 3 (average)

Electro-deposition part

Small cutting resistance, low tool wear

Self-remove chips

Electro-deposited diamond drill bit Diamond coated drill bitGCT Co. ltd.Ewha diamond ltd.

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Module design of drilling machine

Drilling part Circulation of coolant

Protection cover

Step motor

High frequencySpindle

LM guide (2)

Ball bearing

Chuck

XY table

Cooling drilled part

Remove chips

Prevent chips from being scattered out in all over the machine

Gather the coolant to flow into the circulation tube

Protect human body from a broken drill bit

120

100

Cutting oil

pump

Cutting oil

pumpmicro

filter

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Design and implemented drilling machine

XY table

chuck

spindle

Step motor

Control panel

Chiller for spindle

Coolant tank

Coolant hose

Housing flask

Assembly design of a drilling machine

Vertical movement: LM guide (2), ball bearing (1)

Spindle position control: Step motor (unit 0.01mm)

Fix chuck on a X-Y table

Filter the circulated coolant with a micro-filter

Picture of equipment

micro

filter

cutting oil

pump

cutting oil

chamber

control

panel

stepmotor

high freq.spindle

chuck

XY table

Control variable: RPM, drilling depth, feed rate

step feed

Al2O3

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Drilling Experiments with sintered Al2O3

Case study to find the optimal control variables

- Drilling time with various feed rate and step feed

Experiment 1

- Maximum number of holes with a drill bit (tool life)

Experiment 2

- Limit of step feed according to the rotational speed

Experiment 3

Feed rate : moving speed of spindle while drilling the workpieceStep feed : drilling depth in each stepRPM(revolutions per minute) : rotational speed of drill bit

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Influence of step feed and feed rate to the tooling time (at 18000 rpm)

3mm/min 5mm/min 7mm/min 9mm/min

0.02 mm/step - -O

(243min.)

O(242min.)

0.03 mm/step

O(165min.)

O(163min.)

O(163min.)

O(162min.)

0.05 mm/stepO

(101min.)

O(99min.)

O(99min.)

O(98min.)

0.07 mm/stepO

(74min.)

O

(72min.)

O

(72min.)

O

(71min.)

0.09 mm/step

O(58min.)

O(57min.)

O(56min.)

O(56min.)

0.11 mm/stepO

(48min.)

O(47min.)

O(46min.)

O(46min.)

0.12 mm/step

O(45min.)

O(43min.)

O(43min.)

O(42min.)

0.13 mm/stepO

(42min.)

O(40min.)

O(40min.)

O(39min.)

0.14 mm/step

X (broken)

X (broken)

O

(37min.)

X (broken)

0.15 mm/step

-

-

X (broken)

-

Feed rate does not affect the tooling time

As the step feed increases, tooling time is drastically decreased

Step feed should be larger than 0.07mm/step

Drill 5pellets / fuel rod1 working day

(8 hours = 480min.)96 min. / hole

(including waiting time)

Result of Drilling Experiment 1

Step feedFeed rate

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3mm/min 5mm/min 7mm/min 9mm/min

Diameters of drilled holes on a sintered alumina (Al2O3) (at 18000 rpm)

0.13mm/step

0.1

1m

m/step

0.0

7mm/step

No relation between step feed and feed rate

Step feed & feed rate do not affect the precision of drilled hole

Result of Drilling Experiment 1 16


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(rpm)Limito

fstepfeed(mm/step)

Limit of step feed according to rotational speed

Increase step feed by 0.01 until the drill bit is broken

Safe drilling is possible between 8000 rpm and 13000 rpm

Feed rate : 5.0 mm/min

Safe drilling range

Not enough cutting forceHigh friction due to lack

of coolant



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8000 rpm 13000 rpm 18000 rpm

Picture of drilling in each rotational speed

As rpm increases, the more coolant scatters out Feed rate : 5.0 mm/min


Drill bit scatters

out coolant

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0.03mm/step 0.05mm/step 0.07mm/step 0.09mm/step

Feed rate : 5mm/min

Diameters of drilled hole at various RPM and step feed

8000rp

m

13000rpm

18000rpm

Max. run out = 8 m

Max. run out = 4.5 m

Max. run out = 4 m

As the rotational speed increases, the precision of drilled hole increases


The spindle shows a good performance above 13000 rpm

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Summary of Experiment 1 & 2

Feed rate does not affect the tooling time

To drill off 5 fuel pellets in a day, step feed larger than 0.07 mm/step

Safe drilling is possible 8000 rpm - 13000 rpm at a high step feed

Above 13000 rpm, spindle shows a good performance (small run out)

Optimal drilling condition : 13000 rpm, 0.07 mm/step, 5 mm/min

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Check the number of drilling holes with a drill bit


1 2 3 4

5 6 7

Test maximum available drilling holes with a single drill bit At 8thhole, the neck of a drill bit is broken and stuck in the hole

(drill-1: broken at 8thhole, drill-2: broken at 20thhole)

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Drill tip is stuck in the hole

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Statistical analysis on the precision of drilled holes

Hole dia.(mm)

Number of hole

Design specification 1.40 0.05 mm

Diameter of drill bit 1.402 mm

Average diameter of drilled hole 1.413 mm

Standard deviation of hole diameter 0.004 mm

Max. run out 7m

ave

.=1.413mm

=0.004mm


Rotational speed : 13000 rpm

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Wear of a drill bit as the number of drilled holes increase

3

4 5 6

1sthole 2ndhole 3rdhole

4thhole 5thhole 6thhole


Wear is initiated from the lip of a drill tip

Drill bit shows severe wear after 6thhole

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Peeling off of diamond coating layer results in brittle fracture of the drill bit

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Diamond coating layer is peeled off

WC is exposed at the drill tip

Friction force is increased duringdrilling process Brittle fracture occurs at the neck of drill body

Need to inspect the drill bit at least after drilling 6 holes



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Laser weldingPin hole

spot welding

Fabrication of a test fuel rod mockup

Thermocouple

Seal Tube

(SUS 316L)

End Cap Nut Guide

SleeveSinteredalumina

End Cap

Zircaloy Tube

compressionRing

Preparation of components for a test fuel rod

Assembly of the components by welding and mechanical joining

Spot welding system

Fiber laserwelding system

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Concluding Remarks

Development of a new drilling machine for a nuclear fuel

D Applied to the fabrication of a test fuel rod mockup

Case experiments in sintered Al2O3blocks and find out the optimal

drilling condition

D A drill bit can drill off at least 7 holes in the sintered Al2O3blocks

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THANK YOU FOR YOUR

ATTENTION


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Reference

Fuel pellet

Spindle

Drill bit

12

Initial position

n

Feed rate : moving speed of spindle while drilling the workpieceRPM(revolutions per minute): rotational speed of drill bit

Step feed : depth of drilling in each step

Coolant

hose

Difficult to drilling with a single step

Divide total drilling depth with n steps to minimize the damage to the drill bit

Documents

drilling machine3.pdf