Nuclear accidents - lessons learned (TMI-2, Cernobyl, Fukushima) Prof. Vladimír Slugeň

Transcription

1 Nuclear accidents - lessons learned (TMI-2, Cernobyl, Fukushima) Presented by Prof. Vladimír Slugeň Institute of Nuclear and Physical Engineering, Slovak University of Technology, Bratislava, Slovakia

2 Goal of presentation -To inform participants about the main lessons learned from nuclear accidents. - To provide information about the main outcomes from nuclear accidents analyses and their impact on nuclear safety. 2

3 Content of presentation 1. Information about nuclear incidents and accidents 2. Most important lessons learned from TMI, Cernobyl, Fukushima,... 3

4 Three Miles Island Accident TMI 2 accident Vladimir Slugen

5 Three Miles Island Island on the river Susquehanna, 2 PWR: 1.block: 870MWe, 2.block: 956MWe.

6 2.Block TMI 1978, 2 cooling loops, 2 MCP on 1 loop, 956MWe, Fuel matrix: UO 2, Moderator and Coolant: H 2 O.

7 p in : 15,43MPa, p out : 14,96MPa, T c-in : 291 o C, T c-out : 319,4 o C.

8 Accident , 4 oo am 98%N nom

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11 p

12 p 16,23MPa

13 p 15,3MPa 11,04MPa

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15 p PCmin 9,31MPa

16 p BN 1,05MPa

17 p BN 1,31MPa rupture of the safety membrane

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21 Consequences Escape of fission products to environm., Particular realization of accidental plans, Core melting, Fuel destruction, Cracks in SG, INES: 5.

22 The main lessons learned from TMI Maintenance can cause big problems Thank Containment you! is recommended for all next NPPs Creation of WANO

23 Cernobyl accident 1986 Safety culture!

24 The main lessons learned from Cernobyl accident Thank you! INSAG documents Safety culture

25 Parameters Thermal power Moderator Coolant Reactor RBMK MW Grafit Voda Fuel UO 2 Core cylinder (diameter / hight) 12m / 7m Fuel enrichment 2% Burn-up MWd/t Coolent temp. (in / out) 270 C / 284 C Number of fuel assemblies 1661 Number of control rods 211

26 Reactors RBMK worldwide Lituania: Ignalina 1 & 2 (2x1500 MWe) (Russia -15: Bilibino 1-4 ( ) Kursk 1-4 ( ) Leningrad 1 4 ( ) Smolensk 1 3 ( ) Ukraina: Chernobyl 1-4 (1-3 shut-down 2001, 4 block-accident)

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28 Reactor core 1. Graphite stack 2. Pressure tubes 3. Reactor cavity 4. Concrete vault 5. Feedwater channels 6. Lower biological shield 7. Upper biological shield 8,9. Lateral shield 10. Reflector cooling channels 11. Feedwater pipes 12.Top cover 13. Top plate 14. Sand fill

29 Reactor RBMK 1000 Advantages - good experiences with this type of design - positive neutron balance (possibility for Pu production) - reactor pressure vessel is not necessary (fuel rods) - refueling during operation Disadvantages - not stable at low power (< 700MWt) - positive voids reactivity coefficient - core too large difficult regulation - small RA escapes from turbine cycle

30 Contaminated regions

31 Consequences direct victims soldiers as adjusters some of them high irradiated - about 100 time more escaped activity than in Hirošime and Nagasaki (but still times less than at nuclear weapons test in 60-ties) -

32 Safety Culture SAFETY in Nuclear CULTURE Instalations Strategy, aims, sources Multidirectional Regulatory authorities IAEA International communication Conference, ÚJD SR 2-6 December, Rio de Janeiro, Brazil selfcontrol of managing structure TEAMWORK Good visible line of management Responsibility on strategical level BOOM Event investigation, feedback Safety and health protection Emergency measures Slovak Republic Mochovce Nuclear Power Plant Critical approach Questioning attitude Responsibility of individual - Responsibility definition - Definition of working procedures and their checking - Qualification and training Jozef Markuš - Awards and rewards - Audits, inspections, indicators for comparison Rigorous and prudent approach Legislation, Laws, Notices Limits and Conditions, Operation License Responsibility of management Communication Selfcontrol Looking for root causes

33 Safety Culture Three levels of SC: 1. To keep the rules 2. Management has to be a driving force in SC improvement 3. Safety culture can be every times improved.

34 Safety Culture Historical Overview 1986 INSAG-1: Summary Report on the Post-Accident Review Meeting on the Chernobyl Accident THERE IS A NEED FOR A 'NUCLEAR SAFETY CULTURE' IN ALL OPERATING NUCLEAR POWER PLANTS 1988 INSAG-3: Basic Safety Principles for Nuclear Power Plants SAFETY CULTURE is identified as one of the three fundamental management principles AN ESTABLISHED SAFETY CULTURE GOVERNS THE ACTIONS AND INTERACTIONS OF ALL INDIVIDUALS AND ORGANIZATIONS ENGAGED IN ACTIVITIES RELATED TO NUCLEAR POWER

35 Safety Culture Historical overview (2) 1991 INSAG-4: SAFETY CULTURE To clarify and define the concept of SAFETY CULTURE, so that To provide a basis for judging the effectiveness of SAFETY CULTURE in specific instances ASCOT Guidelines (Assessment of Safety Culture in Organisations Team) (IAEA-TECDOC-743) Guidelines for organisational self-assessment of Safety Culture Providing ASCOT Services

36 INES SCALE The International Nuclear and Radiological Event Scale (INES) was introduced in 1990 by the IAEA in order to enable prompt communication of safety significance information in case of nuclear accidents. The scale is intended to be logarithmic, similar to the earthquakes. Each increasing level represents an accident approximately ten times more severe than the previous level. Because of the difficulty of interpreting, the INES level of an incident is assigned well after the incident occurs. Therefore, the scale has a very limited ability to assist in disaster-aid deployment.

37 INES SCALE

38 Tsunami March 11, 2011, 15:41 JST (6:41 UTC) at Fukushima-Daiichi Water Displacement: 40 km 3 (40 Billion tonnes) Wave Height (calculated + GPS): Maximum of 23 m Travel time from epicenter to shore: Epicenter to Fukushima: Wave height Fukushima (TEPCO): 15 Minutes 55 Minutes 14 m Tsunami clearance height Fukushima-I: Level of reactor and turbine buildings: Tsunami clearance height Fukushima-II: 5.7 m 10 to 13 m 5.2 m Tsunami clearance height Onagawa: About 25 m Tentative: If seismic data can be confirmed, practically all damage at Fukushima would have to be contributed to the tsunami. Quelle: GRS, 2011

39 Site Layout Internal emergency diesels 6: BWR 5 Mark II 5: BWR 4 Mark I 1: BWR 3 Mark I 2: BWR 4 Mark I 3: BWR 4 Mark I 4: BWR 4 Mark I Quelle: Florida Power& Light 2011

40 Initial Response Automatic shutdown within seconds (SCRAM) of all operating units in Onagawa (3), Fukushima-Daiichi (6), Fukushima-Daiini (4) and Tokai (1). Start of cooling systems to remove residual heat, with an initial value of about 5 to 10 % of normal heat load, decreasing steadily: 10 to 20 MW. Turbine room fire at Onagawa-1 (estinguished hours later). Loss of offsite power. Start of some emergency diesel generators and emergency cooling systems. Source: MIT NSE Nuclear Information Quelle: FPL

41 Initial Response 55 Minutes later: At least Fukushima-I struck by tsunami (beyond design of levee elevation), taking out all multiple sets of backup emergency diesel generators ( Common Mode Failure ). Reactor cooling by steam-driven emergency pumps, auxiliary systems require emergency battery power (8 h). Operators follow Abnormal Operating Procedures, Emergency Operating Procedures, later Severe Accident Management Procedures (SAMGs). Quelle: FPL

42 Fukushima-Daiichi-1 (GE BWR 3, Containment Mark 1 Design) Reactor Service Floor (Steel Construction) Concrete Reactor Building (Secondary Containment) Reactor Pressure Vessel (RPV) Primary Containment ( Drywell ) Pressure Suppression Pool ( Wetwell ) Quelle: NRC, GE nucleartourist.com

43 Aerial Views before Tsunami and after Explosion of Unit 3 Shared spent fuel Quelle: WANO PC, Barnwood pool building Missing tanks Displaced tank? 43

44 After Fukushima Strong impact on public opinion, bad time for political decisions Life extension will be a more controversial business. The E.U. has decided to submit all European reactors to a set of stress tests (a curious wording coming from the financial crisis). Germany has decided to suspend the plan to extend the life of 17 plants with a three month delay to decide the next step. The two oldest plants could be shutdown this year. Five more are under consideration. Switzerland has frozen its program of new built. Italy has announced its intent to reconsider the decision to restart construction of nuclear plants. U.K. intends to make a new review of EPR and AP1000 designs.

45 After Fukushima

46 PROCESS TO PERFORM THE STRESS TESTS AND THEIR REVIEWS The licensees have the prime responsibility for safety. Hence, it is up to the licensees to perform the reassessments, and to the regulatory bodies to independently review them. The potential timeframe could be as follows: - The licensees could be given 6 months to carry out the work described above and to send the results and related documentation to their national regulator; -The regulator then would perform a review of the licensees submissions. This could take 3 months; the review report would then be published. During the regulatory reviews, interactions between European regulators will be necessary and could be managed through WENRA or ENSREG. Results of the reviews could be discussed in a public seminar, to which other experts (from non nuclear field, from non governmental organisations, etc) should be invited.

47 SCOPE of stress tests The technical scope of the stress tests has been defined considering the issues that have been highlighted by the events that occurred at Fukushima, including combination of initiating events and failures. The following situations will be addressed, corresponding to steps of more and more severe situations: Initiating events - Earthquake - Flooding - Other extreme natural events Consequential loss of safety functions - Loss of electrical power, including station black out (SBO) - Loss of the ultimate heat sink (UHS) - Combination of both Severe accident management issues - Loss of core cooling function - Loss of cooling function in the fuel storage pool

48 The main lessons learned from Fukushima accident Thank you! Several accident management Stress tests