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 Wolsong NPP1 1
Diagnostic Program for S/G Reliability 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) Wolsong NPP1 2
Foreign Object Effect in S/G 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 Wolsong NPP1 3
Wolsong NPP Condition 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 2 nd Side Handhole 3 (2 1ea, 4 2ea) 4 (2 1ea, 4 2ea) 2 nd 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 NPP1 4
NDT Requirement : Performance for S/G Unit 1 (24th Outage, 16.3) Inspection Methods Item SGMP Requirement Performance S/G #1 #2 #3 #4 Bobbin Full Length 100% / 60EFPM - 100% - 100% MRPC Sludge Depth H/L 100% / 60EFPM 10.5% 100% 10.5% 100% Remarks C/L - - 9.6% - 9.6% 3 Col. of Annulus H/L - 100% - 100% Once / 5 period 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 Unit 2 (15 th Outage, 15.11) Inspection Methods Item SGMP Requirement Performance S/G #1 #2 #3 #4 Bobbin Full Length 100% / 60EFPM 100% - 100% - MRPC Sludge Depth H/L 100% / 60EFPM 50.7% - 50.3% - C/L - - - - - H/L 100% - 100% Once / 5 period C/L 20% - 20% Remarks 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 Wolsong NPP1
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 (Inspection) 2.95mm Sword probe by GE (Monitoring) MVIQ by GE Wolsong NPP1 6
Development of FOSAR equipment S/G Structural characteristic and FOSAR Equipment Wolsong NPP1 7
Inspection Results 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 Wolsong NPP1 8
Inspection Results 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 S / G Location Detection Removal Non Removal #1 #2 #3 #4 소계 In bundle 30 25 5 Annulus 0 0 0 No tube lane 2 2 0 In bundle 50 38 12 Annulus 0 0 0 No tube lane 0 0 0 In bundle 48 34 14 Annulus 1 1 0 No tube lane 1 1 0 In bundle 14 7 7 Annulus 0 0 0 No tube lane 0 0 0 In bundle 142 104 38 Annulus 1 1 0 No tube lane 3 3 0 Influx Route : S/G moisture separator remodeling work in 1984 Wolsong NPP1 9
Inspection Results 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] Wolsong NPP1 10
Inspection Results Sludge Depth & Sludge Lancing Unit 1 : Steadily increase & distribution around hot leg center Date S/G Sludge Depth(inch) Sludge Lancing (kg) Max Avg Remarks #1 15 th ( 01.09) #2 B&W 30 #3 Canada #4 : : : : : : #1 6.25 2.46 21 th ( 10.06) #2 6.73 3.20 #3 7.36 2.85 #4 7.96 3.00 22 th ( 12.07) 23 th ( 15.03) 24 th ( 16.03) #2 7.49 3.13 #4 8.61 3.33 #1 8.56 3.13 #3 9.93 3.51 #2 8.33 3.00 #4 9.19 3.24 Refurbishment ( 09.4~ 11.7) Wolsong NPP1 11
Inspection Results Sludge Depth & Sludge Lancing Unit 2 : Slightly increase Sludge Depth(inch) Date S/G Max Avg Sludge Lancing (kg) Remarks 12 th ( 12.02) 13 th ( 13.05) 14 th ( 14.07) 15 th ( 15.10) #2 2.94 1.00 4.3 #4 2.02 1.08 1.7 #1 1.29 0.68 2.6 #3 2.02 0.76 2.5 #2 3.12 1.04 2.6 #4 2.27 0.99 2.4 #1 1.72 0.87 3.0 #3 2.32 0.77 1.9 Wolsong NPP1 12
Conclusions 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 Wolsong NPP1 13
Thank you ( jwlee357@khnp.co.kr ) Wolsong NPP1 14