November 6, TAEK-CHO Yoon Wolsong NPP-2, KHNP, Korea / 1

Transcription

1 November 6, 2013 TAEK-CHO Yoon Wolsong NPP-2, KHNP, Korea / 1

2 Introduction - Wolsong [Wolsong NPS] NPP1&2 : PHWR, Wolsong Unit1~4, Candu 6 NPP3 : PWR, Shin-Wolsong Unit1&2, OPR1000 [Wolsong NPP-2] Rx type : PHWR, Unit3&4 Capacity : 700MW Commercial operation / Lifetime performance( ~2012) - Unit3 : Jul 4,1998 ~ / 93.4% - Unit4 : Oct 1, 1999 ~ / 93.7% Rx manufacturer : AECL/DHI Plant designer : AECL/Kepco E&C Refuelling : 4~5 days/week, 1~4 fuel channels/day / 2

3 Event Summary [Summary] Event Date : May 14, 2012 Unit : Wolsong 4 One of the fuelling machine shielding door was stuck Forced shut down : May 17 16:00 2 driving devices(bogies) for the door were replaced Back to normal operation : May 21 02:00 [Causes] Maint. locks side wheel shaft roller bearing was broken Poor grease lubrication It is impossible to check whether the grease reach maint. locks side roller bearing because the grease outlet hole is inside the door, so we have to disassemble the bogie assembly from the shielding door to check the outlet greasse hole. / 3

4 F/M Shielding Door [General Information] Located between the fuelling machine maintenance locks and the reactor vault Two doors, each of the 2 fuelling machine maintenance locks Provide radiation shielding and ventilation barrier when fuelling machines are not in the reactor vault / 4

5 F/M Shielding Door [General Information] (cont.) Be opened to allow passage of the fuelling machine into the reactor vault for refuelling Provide sufficient shielding to allow personnel access to the fuelling machine maintenance locks while the reactor is in operation [Daily Operation] Open shielding door for refuelling Refuelling Close shielding door after refuelling If shielding door is not fully opened Fuelling machine cannot go into the reactor vault Refuelling is impossible Reactor shut down / 5

6 F/M Shielding Door [Design Description] Consists of a steel plate filled with heavy concrete Size : 7.56m(length), 6.25m(height), 0.96m(thickness) Weight : app. 180ton Travel length : max. 7.6m Travel speed : app. 5m/min takes 1.5min to open or close fully Duty cycle : 5 open&close cycles/week Life : 30years=Plant life [Rx vault side] [Maint. locks side] / 6

7 F/M Shielding Door [Driving device(bogie)] 2 bogies at the bottom edge of the door Weight : app. 7ton Two wheels per one bogie Wheel shaft is mounted on 2 roller bearings / 7

8 Causes & Analysis Poor lubrication of shaft roller bearing - Rx vault side : lubricated well - Maint. locks side : lubricated poorly Maint. locks side roller bearing was broken(front wheel, bogie#2) Grease was injected during every outage but, grease was not reached the maint. locks side bearing because it was leaked around the oil seal.(between bogie body and wheel shaft) [Rx vault side bearing] [Maint. Locks side bearing] / 8

9 Wheel Causes & Analysis Manufactured poorly and maybe did not check the grease path during the plant construction period Motor Coupling Reducer Reactor Vault Torque Limiter Bogie Assembly Grease Inlet Grease path F/M Maint. Locks roller Bearing Rail roller Bearing Door Wall [Grease Path] grease inlet roller bearing(rx side) wheel shaft hole roller bearing grease outlet Check all shaft roller bearings for unit3&4 Not sufficient / 9

10 Follow up Actions All driving device(bogie) replacement - 2 bogies : during forced shutdown period - 6 bogies : Planned outage period in 2013 PM revision - Motor current check : 6month 1week - Bogie replacement : No 10yrs New hole & plug to check grease outlet hole of maint. locks side - Every wheel shaft, ϕ12cm, 15cm depth, 4EA/door New check hole & plug / 10

11 Forced Maintenance Schedule May 14 11:56 May 17 16:00 May 17 17:00 May 20 22:00 May 21 02:00 C-side shielding door stuck Inspect and prepare maintenance Disconnect to national grid Rx shutdown Replace C-side 2 bogies & Conduct Preventive maintenances Rx critical Return to the grid / 11

12 Shielding Door Preventive Maintenance [Every planned outage period] Lubrication of Bogies (grease outlet check added) Calibration of torque limit coupling Oil replacement of reducer gear box Check Inflatable seal or replace Check and Lubricate rail and guide roller Lubrication of bearing Door operational test Check motor current, cable and limit switch [During the Rx is in operation] Check motor current (interval changed) Open and close switch interlock check [Every 10-year] Bogie replacement (added) / 12

13 Thanks / 13