Wolsong NPP1 1

Steam Generator Tube Inspection and Foreign Object Retrieval

in Wolsong NPP

Lee, Jeong Uk ( jwlee357@khnp.co.kr )

Wolsong NPP1 Chemistry Dep’t KOREA HYDRO & NUCLEAR POWER CO., LTD.

South Korea

NDT in Canada 2016 & 6th International CANDU In-Service Inspection Workshop, Nov 15-17, 2016, Burlington, ON (Canada)

www.ndt.net/app.NDTCanada2016

Wolsong NPP1 2

Recently, To enhance integrity of secondary side tube of steam generator(S/G) is strengthening the requirements of non-destructive inspection • ECT

• FOSAR(Foreign Object Search and Retrieval)

CANDU type steam generator tube is hardly defective

But results of a diagnostic program may be affected by • Structural characteristics of S/G model

• Retention of optimized equipment, Operation period

• Inspection evaluation

• Foreign substance characteristics (Especially)

Diagnostic Program for S/G Reliability

Wolsong NPP1

Foreign Object Effect in S/G

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In steam generator with many years of operation, • Equipment access restriction due to hard sludge

• Difficult to access for foreign objects inspection

• ECT Detectivity effect : Co-existence of non-contact non-magnetic foreign objects and sedimentary sludge

Effect of Foreign Object remaining between tubes • Increase the tube defects probability by flow, vibration

Complementary relationship for Foreign Object detection • ECT

• FOSAR

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Item Unit 1 (1) Unit 2, 3, 4

Manufacturer Foster Wheeler Bobcock & Wilcox

Quantity 4 4

Tube 3,558 3,530

Tube Material Alloy 800 Alloy 800

2nd Side Handhole 3 (2” 1ea, 4” 2ea) 4 (2” 1ea, 4” 2ea)

2nd Side Manway 1 1

Tube Gap 4.74mm 5.02mm

Sludge Lancing No (2) Yes (4)

In-Bundle FOSAR Yes (3) Yes (4)

Tube ECT Yes Yes

(1) Continued Operation after license extension (2) No sludge lancing after first by B&W in 2001 (3) First In-Bundle FOSAR in 2016(After Equipment Development) (4) Sludge lancing & FOSAR(2 S/G) for Every outage since 2008

Wolsong NPP Condition

Wolsong NPP1

NDT Requirement : Performance for S/G

Inspection Methods

Item SGMP

Requirement

Performance Remarks

S/G #1 #2 #3 #4

Bobbin Full Length 100% / 60EFPM - 100% - 100%

MRPC H/L 100% / 60EFPM 10.5% 100% 10.5% 100%

C/L - - 9.6% - 9.6% 3 Col. of Annulus

Sludge Depth H/L

Once / 5 period - 100% - 100%

C/L - 20% - 20%

Sludge Lancing H/L Once / 4 period - - - - No equipment

FOSAR H/L Once / 4 period 50% 50% 50% 50% Hard sludge effect

Inspection Methods

Item SGMP

Requirement

Performance Remarks

S/G #1 #2 #3 #4

Bobbin Full Length 100% / 60EFPM 100% - 100% -

MRPC H/L 100% / 60EFPM 50.7% - 50.3% -

- C/L - - - -

Sludge Depth H/L

Once / 5 period 100% - 100%

C/L 20% - 20%

Sludge Lancing H/L, C/L Once / 4 period 100% - 100% Once / 2 period

FOSAR H/L, C/L Once / 4 period 100% 100% 100% 100% Once / 2 period

Unit 1 (24th Outage,

’16.3)

Unit 2 (15th Outage,

’15.11)

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(Monitoring) MVIQ by GE

(Inspection) 2.95mm Sword probe

by GE

Development of FOSAR equipment

FOSAR Mock-Up Simulation and Training • Moving magnetized Rail assembly to the annulus area of S/G

• 2.95mm Sword video probe(GE custom application) inspection

Guide Tube

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Development of FOSAR equipment

S/G Structural characteristic and FOSAR Equipment

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ECT & FOSAR • Unit 1&2 : No signal of degradation mechanism besides DSI(1)

• Unit 1 : A number of ECT PLP signal

Detection : ECT 81(404 signals) + FOSAR 146 = Total 227

Removal : FOSAR 108

Residue : 119 Access restriction area of FOSAR equipment because of sludge

Prevention Maintenance according to the evaluation results

Tube plugging : 1 tube (Remaining lifetime : 1.2 yr)

• ECT PLP evaluation was proved as FOSAR performance

In previous outages it was evaluated as deposit

After development of FOSAR equipment, it was confirmed foreign objects

• Unit 2 : ECT PLP (1) but FOSAR result was a hard sludge

Inspection Results

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ECT & FOSAR • Unit 1 : Foreign object 108(73.9%) of 146 were removed

Most foreign objects were thin plate type, Processing chip

(Mn 0.38%, Si 0.60% : Corroded carbon steel)

Applying the development(R&D) of FOSAR Equipment

Influx Route : S/G moisture separator remodeling work in 1984

Inspection Results

S / G Location Detection Removal Non Removal

#1 In bundle 30 25 5 Annulus 0 0 0

No tube lane 2 2 0

#2 In bundle 50 38 12 Annulus 0 0 0

No tube lane 0 0 0

#3 In bundle 48 34 14 Annulus 1 1 0

No tube lane 1 1 0

#4 In bundle 14 7 7 Annulus 0 0 0

No tube lane 0 0 0

소계 In bundle 142 104 38 Annulus 1 1 0

No tube lane 3 3 0

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ECT : DSI(Distorted Support Indication) of Unit 1 • +Point MRPC performance for Anti-Vibration Bar 6th

• Result : Wear defect 8% (Plugging Criteria : 40%)

[23th Outage] [24th Outage]

Inspection Results

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Sludge Depth & Sludge Lancing • Unit 1 : Steadily increase & distribution around hot leg center

Inspection Results

Date S/G Sludge Depth(inch) Sludge Lancing

(kg) Remarks Max Avg

15th(’01.09)

#1

30 B&W Canada

#2 #3 #4

: : : : : :

21th(’10.06)

#1 6.25 2.46 Refurbishment (’09.4~’11.7)

#2 6.73 3.20 #3 7.36 2.85 #4 7.96 3.00

22th(’12.07) #2 7.49 3.13

#4 8.61 3.33

23th(’15.03) #1 8.56 3.13

#3 9.93 3.51

24th(’16.03) #2 8.33 3.00

#4 9.19 3.24

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Sludge Depth & Sludge Lancing • Unit 2 : Slightly increase

Inspection Results

Date S/G

Sludge Depth(inch) Sludge Lancing

(kg) Remarks Max Avg

12th(’12.02) #2 2.94 1.00 4.3

#4 2.02 1.08 1.7

13th(’13.05) #1 1.29 0.68 2.6

#3 2.02 0.76 2.5

14th(’14.07) #2 3.12 1.04 2.6

#4 2.27 0.99 2.4

15th(’15.10) #1 1.72 0.87 3.0

#3 2.32 0.77 1.9

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In Unit 1, many foreign objects present inside S/G were removed through the FOSAR • S/G Reliability was proved by performing the residue evaluation

Developed FOSAR system was identified the performance • Field test was successful and some improvement is needed

ECT signal evaluation should be cautious if it’s an old plant and FOSAR has not been performed for a long time

For next, to overcome the access restriction area of FOSAR system • Development of Sludge Lancing system required(proceeding, ~’17.9) • (First) Sludge Lancing (later) FOSAR

Conclusions

Wolsong NPP1

( jwlee357@khnp.co.kr )

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Thank you