Dr.-Ing. Rainer Kaulbarsch, Gösgen Power Plant (CH) August, 26th, 2013, Vienna

Transcription

1 Safety Examinations and Improvements after Fukushima, Status Dr.-Ing. Rainer Kaulbarsch, Gösgen Power Plant (CH) August, 26th, 2013, Vienna Folie 1

2 Overview Introduction Examinations easures Outlook and Conclusions Folie 2

3 Introduction - Side and Type Side: North Switzerland, Däniken, Kanton Aargau, Beside river Aare Water intake «0» Water intake «5» Earth Quake Areas Basel Zürich Bern Reference: nuklearforum River Aare KKG Type: SIEENS PWR 3-Loop primary circuit 3002 W th,1035 W el, Heat extraction for industrial use Folie 3

4 Introduction Defence in Depth Operating Systems Limiting Systems Safety Systems *) (Special) Bunkered Emergency Systems Internal Emergency easures External Emergency easures *) In most foreign power plants the «Safety Systems» are called «Emergency Systems». At KKG the «Emergency Systems» are an additional defence line beyond the safety systems. Folie 4

5 Introduction ain Safety Data 3 +1 safety train system (separated) Additional 2 trains of special emergency system (bunkered system) - 10 h autarky operation Designed according to the 30 minutes rule for operator interference Designed against airplane crash, external explosions Elevated location (design against external floods) Accident management manual since 1994, Filtered containment venting since end of 1993

6 Safety Concept Available Equipment (Generators, Water source) Safety Systems Diesel EY1-4 Aare, 0 Aare, 5 Internal Emergency Equipment Dieselgenerators (Security Systems) Well No. 1 Well No. 2 Redundant River Water Intake Aare, 5 Bunkered Emergency Systems Diesel FY5-7 After Fukushima Well No. 1 Well No. 2 Not available due to earthquake loads Firefighting Car (SG Water Injection) i.e. Aare, Cooling Tower obile Dieselgenerators (planned) i.e. Aare, Cooling Tower External Emergency Equipment obile Dieselgenerators i.e. Aare, Cooling Tower Folie 6

7 Safety Examinations (ENSI and EU-Stresstest) 1v2 Examination Result Earthquake (deterministic approach) Earthquake, Fragilities Flood (Deterministic Approach) Earthquake with Dam Rupture (Deterministic Approach) Control by (special) bunkered emergency systems (with & without single failure). Verification for loads < 0.46 g (based on preliminary PEGASOS SSHAG Level 4 project) Controled by (special) bunkered emergency systems (with & without single failure), No water on the plant area. Controled by (special) bunkered emergency systems (with & without single failure). Cascade rupture of all dams upward the river. => 0.2 m water level for approx. 40 min. (> 2.0 m tolerable) Station Blackout Batteries of emergency eystems > 3.5 h. Emergency diesel generators fuel > 72 h. With all fuel reserves on side > h. H 2 Hazard Deflagration with pressure peaks < 3 bar. Containment stays closed. No release over the gas scrubbing unit. Folie 7

8 Safety Examinations (ENSI and EU-Stresstest) 2v2 Examination Primary Circuit Isolation Containment Isolation Extreme weather Result Integritiy is ensured. Internal release into coolant storage unit. Automatic primary circuit isolation. Isolation not necessary due to primary circuit integrity. ain ducts are isolated due to loss of power. Remaining (smaller) ducts can be closed by hand. Swiss nuclear project for re-evaluation ongoing. (Air temperatur, river temperature, rain fall, snow, tornados, ) Ongoing project. Results 1. Dose < 1 msv (100 msv required by Authority). 2. Weak points of the safety systems identified. 3. Event control with (special) bunkered emergency systems. 4. easures to enhance margins of the bunkered emergeny systems done. 5. Further enhancement of safety & bunkered emergency systems. Objective: Reach State of odernization Technology. Folie 8

9 easures External Equipment Storage in «Reitnau» External Storage «Reitnau» obile Pump - obile emergency equipment is stored in a central storage in Switzerland. - Equipment for emergency power generation, power supply cables, pumps for feed water injection into i.e. steam generators available. - Transport to the KKG will be done by the swiss military. obile Diesel Generator => Safety margin increased. Folie 9

10 easures Flood wall - Emergency systems are flood protected up to levels > 2 m. - New wall limits water levels on the plant area to several centimeters and enhances feasibility of emergency measures. => Safety margin increased. New flood protection wall Folie 10

11 easures 2 nd Isolation Valve of ain Coolant Pump Drainage System - 1st isolation of drainage line are the main coolant pump sealings. - 2nd isolation is done by an isolation valve of the volume regulation system. - New isolation valve between pump and (old) second isolation valve ensures primary circuit isolation. => Safety margin increased. 2. Isolation valve TA50S003 Folie 11

12 easures Enhanced Anchorages of the RPS Secured RPS at ZX building Unsecured RPS at ZE building RPS at bunkered emergency systems (ZX) was necessary for event control. RPS inside the electrical building beneficial for event control. => Done to control the event earth quake. Folie 12

13 easures Dampers of the bunkered Emergency Diesels Old dampers replaced. Safety margin increased. Enhanced earthquake robustness > 0.92 g. (0.46 g required) Emergency diesel FY New emergency diesel dampers Folie 13

14 easures Enhancement of the Fire Fighting Building New light construction gate Buildung will withstand earthquaks, gate can easily be destroyed and opend by the firefighting car. The car is not needed wihtin 3 day s. => Safety margin increased. Wall enhancement inside Folie 14

15 easures 2 nd Feed Line for Wet Spent Fuel Storage The wet storage pool is passive cooled by natural convection. No active cooling is needed. Without cooling, T > 80 C will be reached after appr. 4 d. (high grace times). Pipes for external cooling Feed water connector No. 1 Feed water connector No. 2 Emergency pipes for cooling with the heat exchanger were already installed. One emergency pipe to fill in water were already installed before Fukushima. Second feed line installed after Fukushima. => Safety margin increased. Folie 15

16 easures Feed Line for «Loading» Pool The loading pool contains 3 fuel elements and a decay heat of 120 kw in maximum. 60 C will be reached after 2.6 d without cooling. Boiling with loss of coolant will occur more than 3 days after an event. Piping with a connector for exernal water feed-in is installed inside the annulus buildung. => Safety margin increased. Feed water connector Folie 16

17 easures Spent Fuel Pool 2 nd Feed Line The spent fuel pool will heat up to 100 C during several hours (approx. 6 h in minimum). After several hours of boiling, water can be fed into the pool by the existing connector TH74S005 in the annulus building. Entrance to the connector An additional connector for external water feed-in (TH74S007) was installed after the Fukushima event at a different place in the annulus building. => Safety margin increased. Feed water connector Folie 17

18 easures Emergency Control Room Instrumentation (Display Spent Fuel Pool Temperatur & Level) Before the Fukushima event, the spent fuel pool level and temperature was already displayed at the control room. At the emergency control room, level and temperature was controlled by calculations and prepared tables depending on the number of fuel elements. Now an additional pen recorder was installed to provide the current and also previous information of the spent fuel temperature and water level. => Safety margin increased. Pen recorders Folie 18

19 No measure necessary: Spent Fuel Pool Robustness For the Spent Fuel Pool finite-element Calculations show: Pool Integrity is ensured up to Temperatures of approx. 160 C. (160 C corresponds nearly to the Design Pressure of the Containment.) ain Advantage: In Case of Pool boiling with Containment Isolation the Pool Integrity is ensured. Source: AREVA => Low Dose Values. => No Enhancement is necessary. Cross Section of a Welding Folie 19

20 Placement into current Safety Concept Earthquakes with low loads are still controlled by the safety systems. Earthquakes with higher loads (like Fukushima or PEGASOS results) are controlled by the (special) bunkered emergency systems. Bunkeres Emergency Systems are in the Focus of Retrofit easures. Folie 20

21 Conclusion Fukushima like events are controlled by the special bunkered emergency systems. Several measures were necessary to increase earthquake robustness of the special bunkered emergency systems. A lot of measures were done to increase safety margins. Due to the action list of the authority, several measures may have to be done to increase margins. Investigation of KKG for significant safety increase - A-seismic bedding of the hole power plant (positive investigations ongoing). - Significant enhancement of the bunkered emergency systems (positive investigations ongoing). Coherent large Retrofit is appreciated because of higher Benefit compared to punctual Safety Increase. Folie 21