Fukushima: Outside the Imagination and Lack of Preparation. Benefit of PST (Partial Stroke Test)

Transcription

1 International TÜV Rheinland Symposium in China Functional Safety in Industrial Applications October 2011, Shanghai - China Fukushima: Outside the Imagination and Lack of Preparation & Benefit of PST (Partial Stroke Test) 1

2 Part1: Fukushima - East coast Japan earthquake At 14:46 Japan time of March 11, 2011 Offshore about 150 km from Sendai. Two earthquakes followed seconds km south gap. Source region km wide km length Tsunami to Over 500 km coast area 2

3 Part1: Fukushima - Historic scale disaster and victims 1. M 9.5 : Chile ( ) 2. M 9.2 : Prince William Sound, Alaska ( ) 3. M 9.1 : Sumatra-Andaman Islands ( ) 4. M 9.0 : Near the East Coast of Honshu, Japan ( ) 5. M 9.0 : Kamchatka ( ) 6. M 9.0 : Arica, Peru (now Chile) ( ) 7. M 9.0 : Cascadia Subduction Zone ( ) 15,750 people dead, 4059 is still missing, and injured percent of the victims are by the Tsunami. Height of the Tsunami was mostly 5-15m. Highest point was 38.9m! 3

4 Part1: Fukushima - Fukushima Dai1- nuclear power station Japan's nuclear power plants are on the coast for cooling. Fukushima Dai-1 is BWR and Japan's oldest nuclear power plant in All the nuclear power plants in the area successfully stopped after the earthquake. Only Fukushima Dai-1 (=No.1) had the accident. Fukushima Dai-1 Nuclear Power Station (TEPCO) Facilities for external power supply, includes transmission towers are broken by the earthquake. No way to receive external power. 4

5 Part1: Fukushima - Fukushima Dai-1 nuclear power station 1 hour later, 14 to 15m height of Tsunami rushed to the station. -> Reactor/Turbine building are flooded. -> Emergency diesel power generators were submerged. -> Battery of ECSS (Emergency Core Cooling System) has gone after 8 hours. All cooling system were lost. Several hours later, 3 reactors had meltdown. Tsunami hits to Dai-1 Nuclear Power Station (TEPCO) 5

6 Part1: Fukushima - Tsunami to Fukushima Dai-1 M7 class earthquake is considered as a possible risk. M8 or beyond has considered very remote, no chance. Expected maximum height of Tsunami is 5.6m. But M9 was happened and Tsunami was 15.6m. 15.5m above sea level (TEPCO)) 6

7 Part1: Fukushima - Fukushima Dai-2 Fukushima Dai-2 (No.2) Nuclear power station 10km south of the Fukushima Dai-1 It is Japan's second oldest nuclear power plant in Both are BWR and basic design is same. All facilities of both of Dai-1 & Dai-2 could stand against the earthquake However, Fukushima Dai-2 safety stopped didn t have any accident like Dai-1. What divided the big difference of consequences? Fukushima Dai-2 Nuclear Power Station (TEPCO) 7

8 Part1: Fukushima - Lucky of Fukushima Dai-2 Dai-1 Dai-2 Site altitude from sea level 10m 12m Back-up diesel generator Turbine building Reactor building (Ocean side) (Mountain side) Reactor building has better airtightness than turbine building. Dai-2 could kept its power for cooling and other facilities. Fukushima Dai-1 Fukushima Dai-2 Turbine Reacto r Turbine Reacto r sea level 10m sea level 12m 8

9 Part1: Fukushima - Dilemma Another geological survey, Fukushima area had M8 class with 9m of Tsunami once per 1,000 years, from 3,000 years ago. How we could assume an interval of 15m height Tsunami? How large earthquake (disaster) we should prepare? Installing facility on 30m above sea level is possible. However, it creates other risks, i.e. lost of functions of pumping up the sea water for cooling. There is no easy answer for risk assessment. Also Fukushima Dai-1 shows a difficulty of considering common failure by disaster. 9

10 Part 2 Benefit of PST (partial stroke test) 10

11 - Horizontal / Vertical integration Horizontal integration: Process and system information (data, alarm & event) of both of DCS and SIS are integrated in common operator HIS (Human-machine interface station). Vertical integration: Diagnosis information of intelligent field devices for both of DCS and SIS are integrated in the common PRM (Plant resource management) window. HIS (DCS Operator Interface) (PRM)Plant Resource Management Process Controller Safety Controller Transmitters w/diagnostics Control Valves w/diagnostics Transmitters w/diagnostics ESD Valves w/diagnostics 11

12 - Proof test of ESD valve Proof test for ESD valves are most important part to maintain the safety functions. FST (full stroke test) - Confirm the full closure of the valve % coverage - Need process interruption (stop), or bypass installation - Time consuming and costly. PST (Partial stroke test) - Confirm the partial (small) closure of the valve. - Diagnostic coverage is not 100%. No guarantee of full closure. - No need to stop the process 12

13 - Legacy style FST/PST Old style FST without interrupting the process - Installation of bypass route and manual valve on it. Old style PST without interrupting the process - introduce a valve with some measure for PFT. Both has - Many manual procedures includes manual recording - Coordination between field engineer and asset manager Inherently include a chance of the human errors. 13

14 - Legacy style FST with bypass Bypass pipe and manual valve must be installed. How to test: 2 engineers (A & B) must be in the field. B visits the rack room. A visits the valve. A opens the manual valve. B shorts the terminal by a jumper. A confirms the closure. B removes the jumper. A confirms the open. A closes the manual valve. A or B records the test. B SIS A 14

15 - Legacy style FST with bypass Many chances of human-error to cause a dangerous failure, or a false trip SIS A opens the manual valve. If A opens the wrong manual valve. B shorts the terminal by a jumper. If B shorts wrong terminal by a jumper. B removes the jumper. If B forgets to remove the jumper. A closes the manual valve. If A forgets to close the valve. A or B records the test. If A or B forgets to record the test. B A 15

16 - Legacy style PST with block pin Use a pin to block the movement of stem. How to test: 2 engineers (A & B) must be in the field. B visits the rack room. A visits the valve. A inserts the pin to the valve. B shorts the terminal by a jumper. A confirms some closure. B removes the jumper. A confirms full open. A removes the pin. A or B records the test. B SIS A 16

17 - Legacy style PST with block pin Many chances of human-error to cause a dangerous failure, or a false trip SIS A inserts the pin to the valve. If A inserts the pin to the wrong valve. B shorts the terminal by a jumper. If B shorts wrong terminal by a jumper. B removes the jumper. If B forgets to remove the jumper. A removes the pin. If A forgets to remove the pin. A or B records the test. If A or B forgets to record the test. B A 17

18 - New technologies Remote PST box - Small box next to the valve, push button to execute PST, and indicator to confirm the result. - Still requires someone needs to visit the valve, weakest point. - Visiting valves is costly and troublesome work. especially in the remote and distributed site. - No integration to the PRM (Plant Resource Manager), the asset management software. PST from PC - Software commanding from PC - Based on the field digital technology. - No need to visit valve. - Not common among the vendors. - No integration to the PRM (Plant Resource Manager) software. 18

19 - PST Scheduler, the latest and common solution PST Scheduler Common interface for different valve venders. - Easy interface for scheduling of PST and monitoring the results. - Common workplace of PST for multiple venders. - Based on the common technology platform (HART, FDT/DTM) - Integration to PRM. The result of the test is integrated to PRM. - PST Scheduler client is available on the operator station, not only the safety engineering station. Operator can initiate cancel, and confirm PST. 19

20 - PST Scheduler 20

21 - PST Scheduler Easy calendar based scheduling Results and coming test are on one window 21

22 - PST Scheduler Common interface for different valve venders. Integrated to the PRM software. Client can be on HIS (Operator station) for closer relationship between operation and maintenance. Based on FDT/DTM technology Detail is available to upload 22

23 Fukushima: Outside the imagination, & Benefit of PST (partial stroke test) Conclusion The disaster of Fukushima Nuclear Power station has been caused very far rare large earthquake and Tsunami. However, a major disaster was not only the reason of the consequences. Difficulty of risk assessment is a limitation of human imagination. The implication of the PST makes available not only reducing the cost and complexity for proof testing of the valve, but also reducing the likelihood of human error. The unified PST scheduler among multiple venders is confirmed that there are many conveniences to users. 23