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Demonstration Drop Test and Design Enhancement of the CANDU Spent Fuel

Storage Basket in MACSTOR/KN-400

Woo-Seok Choi*, Jae-Yeon Jeon, Ki-Seog Seo(KAERI)Jung-Eun Park (KHNP)

2010. 6. 2

Demonstration Drop Test and Design Enhancement of the CANDU Spent Fuel

Storage Basket in MACSTOR/KN-400

Woo-Seok Choi*, Jae-Yeon Jeon, Ki-Seog Seo(KAERI)Jung-Eun Park (KHNP)

2010. 6. 2

International Conference for Spent Fuel Management from Nuclear Power Reactors

May 31- June 4, 2010, Vienna, AustriaIAEA-CN-178/08-04

International Conference for Spent Fuel Management from Nuclear Power Reactors

May 31- June 4, 2010, Vienna, AustriaIAEA-CN-178/08-04

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Contents

1. Introduction

2. Demonstration test

3.1 Devices to measure an impact velocity

3.2 Accelerometers and strain gauges

3.3 Leak test

3. Drop test results

3.1 Deformations

3.2 Impact velocity

3.3 Leak rate

4. Design enhancement

5. Conclusion

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A dry interim storage facility named MACSTOR/KN-400 for

CANDU type spent fuels has been constructed at the Wolsung

Power Plant(WSPP) in Korea. The MACSTOR/KN-400 has 7 modules. 400 cylinders/module, 10 baskets/cylinder Under the process of licensing this facility, KINS(Korea

Institute of Nuclear Safety) recommended the demonstration

drop test of the basket in this facility. KAERI(Korea Atomic Energy Research Institute) conducted

this test with the support of KHNP (Korea Hydro & Nuclear

Power Co.).

A dry interim storage facility named MACSTOR/KN-400 for

CANDU type spent fuels has been constructed at the Wolsung

Power Plant(WSPP) in Korea. The MACSTOR/KN-400 has 7 modules. 400 cylinders/module, 10 baskets/cylinder Under the process of licensing this facility, KINS(Korea

Institute of Nuclear Safety) recommended the demonstration

drop test of the basket in this facility. KAERI(Korea Atomic Energy Research Institute) conducted

this test with the support of KHNP (Korea Hydro & Nuclear

Power Co.).

1. Introduction

A drop test facility consisting of a cylinder and towerA basket test

modelMacstor/KN-400

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1. Introduction (Performance requirements)

Drop Conditions Dropping a basket into a cylinder Dropping a basket onto the other basket loaded in

cylinder Performance requirements

Deformation requirement is for the retrievability. Leak rate requirement is for maintenance of containment

boundary. Geometric dimension

Inner diameter of cylinder : 1,117.6 mm

Outer diameter of basket : 1,066.8 mm

Drop Conditions Dropping a basket into a cylinder Dropping a basket onto the other basket loaded in

cylinder Performance requirements

Deformation requirement is for the retrievability. Leak rate requirement is for maintenance of containment

boundary. Geometric dimension

Inner diameter of cylinder : 1,117.6 mm

Outer diameter of basket : 1,066.8 mm

Performance requirement

Allowable criteria

1. Deformation< 1,102 mm

(for outer diameter of basket)

2. Leakage rate < 10-5 atm·cm3/sec (He)

Schematic drawing of a drop test facility and drop conditions

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2.1 The first device to measure an impact velocity

Two devices invented and installed to measure the impact velocity of a basket The first device uses two laser displacement sensors installed with a distance difference.

Calculates the time difference between the measured times when the basket passes over

each sensor The distance difference divided by the measured time difference yields the impact velocity.

Two devices invented and installed to measure the impact velocity of a basket The first device uses two laser displacement sensors installed with a distance difference.

Calculates the time difference between the measured times when the basket passes over

each sensor The distance difference divided by the measured time difference yields the impact velocity.

Schematic drawing for the laser sensor arrangement

Arrangement of two installed laser sensors

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The second device uses a fan shaped rotation device and a laser displacement sensor. The invented device is installed above the cylinder.

A fishing string is rolled around the circulated object and one end of string is attached to

the top of a basket. When the basket starts to drop, the string becomes unfolded and the object starts to

circulate. A laser sensor acquire the pulse data when it circulates. From this pulse data, the RPM of the circulated object is calculated. Consequently, an impact velocity is calculated from this RPM.

The second device uses a fan shaped rotation device and a laser displacement sensor. The invented device is installed above the cylinder.

A fishing string is rolled around the circulated object and one end of string is attached to

the top of a basket. When the basket starts to drop, the string becomes unfolded and the object starts to

circulate. A laser sensor acquire the pulse data when it circulates. From this pulse data, the RPM of the circulated object is calculated. Consequently, an impact velocity is calculated from this RPM.

2.2 The second device to measure an impact velocity

Schematic drawing for the second device Arrangement of the second device

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2.3 Accelerometer and strain gauge

Accelerometers and strain gauges are attached to

basket only. Accelerometers: 4 each

On spacer pad blocks by the space of 90 degree Impact acceleration acquisition Evaluate which bottom region drops first

Strain gauges: 8 each 4 strain gauges attached to the neighborhood of an

upper welded part between the top plate and the

post. 4 strain gauges to the neighborhood of a lower

welded part between the side wall and the bottom

plate. Strain acquisition before and after impact

Accelerometers and strain gauges are attached to

basket only. Accelerometers: 4 each

On spacer pad blocks by the space of 90 degree Impact acceleration acquisition Evaluate which bottom region drops first

Strain gauges: 8 each 4 strain gauges attached to the neighborhood of an

upper welded part between the top plate and the

post. 4 strain gauges to the neighborhood of a lower

welded part between the side wall and the bottom

plate. Strain acquisition before and after impact

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Measuring the leakage rate after drop test Procedure

Basket is charged with helium gas A Sniffer test is conducted. After basket is kept for 15 minutes, a leakage rate is measured by the helium mass

spectrometer.

Measuring the leakage rate after drop test Procedure

Basket is charged with helium gas A Sniffer test is conducted. After basket is kept for 15 minutes, a leakage rate is measured by the helium mass

spectrometer.

2.4 Leak test

Basket under charging helium gas Leakage test by helium mass spectrometer

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3.1 Drop test results (deformation)

Before After

Diameter (0º-180º) 1067.2 1065.8Diameter (90º-270º) 1067.1 1065.6

Height (0º) 557.22 557.75Height (90º) 557.36 558.06

Height (180º) 557.65 557.90Height (270º) 557.74 557.66

Dropping basket Loaded basket

Before After Before After

Diameter (0º-180º) 1067.1 1067.0 1067.0 1066.0Diameter (90º-270º) 1067.0 1067.0 1066.3 1066.2

Height (0º) 557.67 558.18 557.35 556.06Height (90º) 557.37 557.61 557.92 555.89

Height (180º) 557.37 557.47 557.69 557.09Height (270º) 557.40 560.37 557.29 557.64

After the drop test, both of the dropped basket and the loaded basket were withdrawn by a

grappler. The retrievability of both baskets was maintained.

After the drop test, both of the dropped basket and the loaded basket were withdrawn by a

grappler. The retrievability of both baskets was maintained.

Dimension of a basket before/after the first drop testDimension of a basket before/after the second drop test

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1.806 1.808 1.810 1.812 1.814 1.816 1.818 1.820

-40

-20

0

20

40

Ma

gn

itu

de

[m

m]

Time [sec]

1st 2nd

1.70 1.72 1.74 1.76 1.78 1.80 1.82 1.84 1.86 1.88 1.900

10

20

30

Ma

gn

itu

de

[m

m]

Time [sec]

Rev_Pulse

Drop test Using 2 laser sensors

Using rotation device

case 11st drop test 9.43 m/s 9.26 m/s

case 12nd drop test 9.42 m/s N/A

Drop test Using 2 laser sensors

Using rotation device

case 21st drop test 9.15 m/s 9.17 m/s

case 22nd drop test 9.22 m/s N/A

3.2 Drop test results (impact velocity)

Case 1: Drop to the cylinder bottom Theoretical free drop velocity: 12.13 m/s Velocity reduction: 22.3% ~ 23.7%

Case 1: Drop to the cylinder bottom Theoretical free drop velocity: 12.13 m/s Velocity reduction: 22.3% ~ 23.7%

Case 2: Drop onto the other basket Theoretical free drop velocity: is 11.67 m/s Velocity reduction: 21.0% ~ 21.6%

Case 2: Drop onto the other basket Theoretical free drop velocity: is 11.67 m/s Velocity reduction: 21.0% ~ 21.6%

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Impacted area to the post of stacked basket (45 degree)

Dropped basket figure 1 Dropped basket figure 2

Loaded basket figure 1 Loaded basket figure 2

Leak happening region (PT) Leak happening region (PT)

Leak from welding part between the top plate and the post (225 degree)

Leak rate: 1.5×10-2 atm· cm3/sec (HE)

3.3 Drop test results (leak rate)

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4. Design enhancement

Clear understanding of the problem has been done by drop analysis. Drop analysis showed that a large plastic strain happened locally at the welding part.

Clear understanding of the problem has been done by drop analysis. Drop analysis showed that a large plastic strain happened locally at the welding part.

The bottom plate of a dropping basket impacts to the post of a loaded basket

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Direction of design enhancement

(1) To enhance the welding performance of welding region itself

(2) To afford the deflection of the bottom plate of the dropped basket

(3) To increase the bending rigidity of the top plate of the basket

(4) To increase the bending rigidity of the bottom plate of the basket Six revised designs based on the design direction were generated

Direction of design enhancement

(1) To enhance the welding performance of welding region itself

(2) To afford the deflection of the bottom plate of the dropped basket

(3) To increase the bending rigidity of the top plate of the basket

(4) To increase the bending rigidity of the bottom plate of the basket Six revised designs based on the design direction were generated

The revised basket designs

Revised designs Design direction

1. Increase of the welding thickness at top welding region (1)

2. Addition of extra spacer pads and increase of rib height (2)

3. Increase of the thickness of side wall (4)

4. Increase of the thickness of bottom plate (3)

5. Increase of the thickness of top plate (4)

6. Decrease of the height of central post (2)

4. Design enhancement (Cont’d)

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Among 6 proposed designs, the final revised design was achieved by the evaluation of many FE

analysis and the specimen test. The final revised design was the one, which is decreasing the height of the central post. And the revised design was achieved by the minimum design change from the original design. Demonstration test with the revised basket satisfied all the performance requirements.

Among 6 proposed designs, the final revised design was achieved by the evaluation of many FE

analysis and the specimen test. The final revised design was the one, which is decreasing the height of the central post. And the revised design was achieved by the minimum design change from the original design. Demonstration test with the revised basket satisfied all the performance requirements.

Post of the revised basket

Post of the previous basket

4. Design enhancement (Cont’d)

Revised designs EnhancementStrain (%)

(Previous:28.07%)

1. Welding thickness increase ▲ 27.35

2. Addition of extra spacer pads and rib height increase ▲ 25.87

3. Side wall thickness increase ▲ 25.40

4. Bottom plate thickness increase △ ※ 25.55

5. Top plate thickness increase ▼ ※ Over than elongation

6. Central post height decrease ▲ 24.89

※Collision between fuel dummy and top plate

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Deformation

Basket impact velocity

Acceleration history

Strain history

DesignEnhancement

Needed

Demonstration test with the revised basket satisfied all the performance requirements.

Evaluation of FE Analysis and Specimen Test

Comparison between Test and Analysis Results

Data Acquisition During Test

Performance Requirements

5. Conclusion

Deformation (Retrievability) criteria satisfied

Leak rate criteria not satisfied for the loaded basket

Verification through PT

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