SAFETY IMPROVMENTS AT KANUPP. Ahsan Ullah Khan Principal Engineer Karachi Nuclear Power Plant

Transcription

1 SAFETY IMPROVMENTS AT KANUPP Ahsan Ullah Khan Principal Engineer Karachi Nuclear Power Plant

2 General 137 Mwe CANDU Plant Started commercial operation in 1972 Design life of 30 years completed in 2002 An extensive program for Safe Operation of KANUPP (SOK) launched in 1991 under the umbrella of IAEA Re-licensing Outages in 2003 and 2006 for addition of new safety systems and several other safety upgrades to fulfill regulatory requirements for renewal of operating license Regulator granted operating license at 98 MW till Dec. 2016

3 International Review / Assistance IAEA Safety Review (OSART Missions) 1985, 1989 Review of Reactor Core Components (ASSET) 1989 Membership of CANDU Owner s Group (COG) 1989 Membership of WANO-TC and WANO-AC 1989, st WANO Peer Review by Tokyo Centre (TC) 1994 WANO-TC Peer Review Follow-up 1996 Aging Management Assessment Team (AMAT) 1999, nd WANO Peer Review by Atlanta Centre (AC) 2000 IAEA International PSA Review Team (IPSART) Mission 2001 IAEA Led Full Scope PROSPER Mission rd WANO Special Review by TC 2010 Follow up of 3 rd WANO Special Review 2013

4 Major Safety Improvements at KANUPP Improvements in LOCA handling capability: 1. Provision of Redundancies in Low Pressure ECC System to meet single failure criteria (Redundant Emergency Injection System,RIJW) 2. Installation of Medium Pressure ECC system to handle Sizable Break LOCA (Forced Emergency Injection System (FIJW) 3. Installation of Emergency D 2 O Addition facility for handling of small LOCA (EHWT System)

5 Major Safety Improvements at KANUPP 4. Automatic Boiler Crash Cool down (ABCC) 5. LOCA Handling Capability outside boiler room (EST System) 6. LOCA qualified MH-PMs & AD-PMs 7. AD Sump protection against debris

6 Major Safety Improvements at KANUPP Installation and Automation of Emergency Feed Water System (EFW, Secondary Heat Sink)

7 Improvements in LOCA handling capability Redundant Emergency Injection System (RIJW) Purpose The main function of the Emergency Injection System (IJW) is to provide cooling of the fuel in the event of loss of coolant which is due to a rupture or break in the Primary Heat Transport System. Cooling is necessary to maintain the integrity of the fuel to prevent escape of fission products. Installation of Second Train in IJW system (RIJW) to fulfill the single failure criteria of old Emergency Injection (IJW) system.

8 PREVIOUS EMERGENCY INJECTION SYSTEM Core and PHT Headers NOH NIH SOH SIH Old IJW Path and Circuit = 6 = 6 Core = 6 = 6 Service Building (S- 308) SH-MV1 SH-P1 SH-MV5 SH-MV3 SH-HX1 SH-MV2 SH-P2 SH-MV6 SH-MV4 SH-HX2 SH-MV7 SH-NV1 SH-NV2 =8 =8 =8 SH-MV8 To Ab, Bs. Rods MH-MV7 To Calandria Sprays MH-HX1/2 MH-HX3 AD- P8 AD- P9 MH- MV10 MH- TK1 MH- Pumps Sump Boiler Room R-207

9 IJW SYSTEM WITH REDUNDANT VALVES =6 Reactor Building R-207 =6 =6 NOH = 6 = 4 IJW- MV1 IJW-MV5 = 6 = 4 IJW- MV3 NIH Core = 4 IJW-MV2 SO H IJW-MV6 = 6 = 4 IJW-MV4 SI H = 6 = 6 Service Building (S-308) IJW-V2 SH-MV1 SH-P1 IJW-V1 CH (P) SH- HX2 IJW-V3 SH-MV8 SH- MV7 SH-MV5 SH- MV3 SH-HX1 SH-MV2 SH- P2 SH-NV1 SH-NV2 =8 =8 IJW -MV7 =8 SH-MV6 SH-MV4 IJW-MV8 CH (P) IJW-V4 Core and PHT Headers To Ab, Bs. Rods MH-MV20 MHMV2 7 MH-MV7 To Calandria Sprays Existing IJW Path and Circuit AD- P8 AD- P9 MH- MV10 MH-TK1 MH- HX1/2 MH-HX3 MH-Pumps Redundant IJW Path and Circuit MH-MV30 Sump

10 Improvements in LOCA handling capability Forced Emergency Injection System (FIJW) Purpose To enhance core cooling, medium pressure system (FIJW) has been installed to improve the functionality and effectiveness of core cooling at KANUPP. FIJW will provide once through cooling in the event of loss of coolant accident, LOCA, by injecting light water at the rate of 360 Igpm and 300 psig pressure till the IJW system take over cooling function (at 90 psig). The major aim is to prevent fuel sheath heating beyond the acceptable limit (600 C) particularly for small break LOCA cases in the range of kg/sec. A storage tank of capacity 180 Tons, which is sufficient to provide water to FIJW system for 100 minutes ( 1.66 hrs ).

11 Improvements in LOCA handling capability Design Basis: Complete Independent and Physically Separated System. Medium Pressure Injection. Equipment of FIJW System is Redundant by itself. Automatic Initiation. FIJW-DGs can also provide power supply to some essential loads under Station Blackout (SBO) by energizing plant essential bus through FIJW-DG1 & FIJW-DG2.

12 FORCED EMERGENCY INJECTION WATER SYSTEM (FIJW) Core and PHT Headers Reactor Building Existing IJW Path & Circuit Redundant IJW Path & Circuit Forced FIJW Path & Circuit NOH IJW- MV1 IJW- MV3 NIH SOH IJW- MV2 IJW- MV4 SIH Service Building (S- 308) =6 Core = 6 AD- P8 Sum p AD- P9 SH-MV1 SH-P1 IJW- MV7 SH-MV7 MH- MV10 MH-MV30 = FIJW-NV1 3 = 4 MH- TK1 SH-MV3 SH-HX1 SH-NV1 Vent to CH (P) FIJW- V2 FIJW-MV4 MH- MV27 MH- HXs =8 SH-MV2 SH-P2 SH-NV2 = 3 FIJW- MV8 MH-MV7 MH-PPs FIJW-NV2 FIJW- V1 SH- MV4 SH-HX2 SH-MV8 IJW- MV8 FIJW-MV7 Drain to CH (P) FIJW-MV1 FIJW-MV2 = 4 FIJW-MV8 Drain EL = 110 Flang e FIJW-MV3 FIJW-OR1 FIJW-V11 FIJW-V10 Drain Re-circulation and Testing Line = 2 FIJW-MV5 FIJW-V8 P P 2 x FIJW- PPs FIJW- V12 FIJW-MV6 EL = 120 FIJW-V5 FIJW- V9 H FIJW-V3 Chemical Addition FIJW-V6 FIJW-TK1 (180 Ton) H 2 O FIJW-V4 FIJW-NV3 FIJW-NV4 FIJW-P1 FIJW-P2 FIJW- V7 = 6 MW-V FIJW-V14

13 Improvements in LOCA handling capability Emergency Heavy and Light Water Transfer System (EHWT) Purpose Add D 2 O rapidly into CPH-TK1 to help the operator to crash cool down & depressurize the PHT during LOCA that are within the capacity of charging pumps. The reserve D 2 O will help to gain time for leak isolation (If possible) before IJW actuation. 04 D 2 O storage tanks with 18 ton capacity. H 2 O can also be injected if IJW has failed or pressure stagnation delayed IJW injection.

14 Improvements in LOCA handling capability Automatic Boiler Crash Cooling System (ABCC) Purpose KANUPP Emergency Injection (IJW) System is a low pressure system (100 psig) and after Loss of Coolant Accident (LOCA) the actual IJW injection could not take place until PHT pressure decreases to < 90 psig. After LOCA PHT depressurization pattern is a strong function of break size i.e., for Large LOCA PHT decreases very rapidly to < 90 psig. However, for some small LOCA scenarios it takes rather longer time to PHT to decrease below 90 psig. Therefore, for small LOCA scenarios emergency coolant injection in to the core delayed and resulted in rise in fuel / sheath temperature which is not desirable. There are certain small LOCA break sizes where PHT pressure locked on to the secondary side boiler pressure at around 610 psig (blow-off set point). In these cases boiler start acting as a heat source rather as a heat sink. Thus it is necessary to remove boiler heat through blow off so that effective cooling and depressurization of PHT will take place.

15 Improvements in LOCA handling capability Meaning of ABCC Simultaneous and full (100%) opening of all six (06) blow off valves. Automatic Termination When any steam header pressure is < 50 psig (that side blow off valves will close) to avoid containment breach condition in case of steam line break scenario. ABCC Current Policy It is a part of IJW system Must be on AUTO when reactor critical and PHT > 300 F

16 15

17 T emperature ( C) Fuel / Sheath / PT Temperatures After Loss of Crash Cooling Sheath PT Fuel Without Crash Cool Time (s)

18 With Crash Cool 17

19 Improvements in LOCA handling capability LOCA Handling Capability outside boiler room (EST System) Purpose KANUPP IJW system has no capability of re-circulation to handle the LOCA out side boiler room. Emergency Sump Transfer System (EST) transfer spilled D2O from reactor building sumps to moderator area sump after LOCA outside boiler room for prolong core cooling. Main Component : Two vertical submersible pumps(est-pm1/pm2) installed at AD5H. Two vertical submersible pumps(est-pm3/pm4) installed at AD7H.

20 Purpose Emergency Boiler Feed Water system (EFW) The Emergency Boiler Feed Water system has been incorporated to provide water to all six Steam Generators in the event of total loss of Boiler Feed Water. In case of SBO, independently seismically qualified Emergency Feed Water (EFW) system acts as an alternate heat sink.

21 Emergency Boiler Feed Water system (EFW) The EFW system consist of : Two 100% percent duty, diesel powered multistage centrifugal pumps, capacity 60 Igpm at discharge pressure 250 psig. Two 100% duty Diesel Generator of 169 KVA. A storage tank, capacity 22,700 Imperial gallons in addition to RFW-TK2 capacity sufficient to provide EFW to boilers for 36 hrs.

22 Major Safety Improvements at KANUPP Some of the other Safety improvements are Installation of third emergency diesel DE-DG3 to improve reliability of emergency power Replacement of Battery Banks Replacement of 132 KV transmission line circuit breakers and protection relays Modification in Annulus Gas System for Leak Before Break (LBB) MCR Habitability for Main Steam Line Break (MSLB)

23 Major Safety Improvements at KANUPP Some of the other Safety improvements are Seismic fixes (Seismic Retrofits / Easy Fixes (Improve seismic resistance 0.2g) Seismic monitoring instrumentation Strengthening in Fire Prevention / Control Refurbishment of Delayed Neutron Activity Monitoring System Safety Parameter Display System (SPDs) / Critical Parameter Display System (CPDS)

24 Major Safety Improvements at KANUPP Some of the other Safety improvements are Implemented safety culture programs (Ageing Management, CAP, RCA, SA, SPI, EPM, etc) Development of EOPs / SAMGs (under development) Replacement of C&I Loops (Reactor protection = 49, Safety = 15, Control = 22, Measurement = 27) Fire doors

25 PAEC Response in the Wake of Fukushima In response to Fukushima NPPs Accident, PAEC Corporate Office called a meeting on 25 March 2011 to re-assess the safety of KANUPP and CHASHMA NPPs. Targeted action plan called Fukushima Response Action Plan (FRAP) issued for KANUPP by Corporate Office on 22 June 2011.

26 PAEC Response in the Wake of Fukushima After Incorporation of Post Fukushima modification the safety again natural hazards will significantly improve. Following safety improvements in connection to FRAP have been implemented. 1. EWI system (EL-180 ft) which is non-electric water injection system. 2. Diesel generators (EL-180 ft) for recharging the batteries 3. Make-Shift A/C power systems.

27 Additional Measures For Core Cooling (Direct / Indirect) PW-TK1 (2000 IG) BFW-TK1 (27740 IG) RFW-TK2 (20000 IG) DMW-TK1 (20000 IG) FW Ring Flexible Hose Gravity Feed Line Boilers Core Cooling Dousing Spray Diesel Driven Pumps (02) 100 igpm, 100 psi Vault Cooling Spent Fuel Bay SEA WATER

28 Thank You!