Fukushima & Three Mile Island Reactor Accidents: Recovery, Cleanup, Lessons, & Future

Transcription

1 Fukushima & Three Mile Island Reactor Accidents: Recovery, Cleanup, Lessons, & Future Foundation For Nuclear Studies Congressional Briefing May 18, 2012 Lake H. Barrett Disclaimer: Fukushima Information is preliminary especially regarding interpretation of events; opinions expressed are mine and mine alone. Most Photos Courtesy of TEPCO 1

2 Energy & Human Societal Evolution Mankind Huts to Modern Cities Energy Simple Fire to Fossil Electricity to Nuclear Electricity Energy Density Diffuse/Intermittent to Concentrated/Continuous 2

3 Constant Evolutionary Societal Benefit/Risk Tradeoffs No Energy Source is Free From Risk or Cost Oil Rig Fire Gas Pipeline Explosion Wind Mill Collapse Coal Mine Accident Coal Ash Dam Break Hydro Power Floods 2000 Killed 1963 Solar Panel Roof Falls 3

4 Nuclear Power Plant High Density Energy Reactor Core Boils Water 4

5 Three Mile Island Units 1 &2 March 28,

6 Three Mile Island Unit 2 Accident March 28, 1979 Relief Valve fails to close PORV Operators Believe Reactor Overfilled and Turn Off Injection Pumps Core is uncovered Fuel overheats/fails/~50% Melt 650,000 gallons of highly radioactive water collects L. Barrett Consulting 6 LLC

7 TMI Core Damage Sequence 7

8 Three Mile Island March 28, 1979 Hydrogen Deflagration 28psig 13:00 ~3M deep water 1000R/hr 8

9 Offsite Releases Variable & Confused Readings 3/

10 Public Confusion Due To Lack of Information & Distrust Company Not Believed Government Distrusted But NRC Single Spokesman Denton Made Progress 10

11 TMI Precautionary Evacuation Minimal Releases But Great Uncertainty Then Mostly Noble Gases, Minor Iodine (<15Ci), No detectable Cs release Maximum Dose <<1msv, ave ~10 μsv (<1mr) over 2M Advisory Evacuation for Pregnant Women & Children on 3/30/79 ~140,000 People Left for Less than a Week Cost $71M Paid by Owner Insurance 11

12 PA Evacuation Sites 12

13 President Carter Arrives April 1 President Carter In Control Room Carter, Denton & PA Governor Thornburg 13

14 Initial Plant Stabilization Core Cooling Established: 6 Hours Cold (<100C) Passive Shutdown:1 Month All Accident Water Retained Pre accident Water Processed and Released to Make Room For Accident Water Accident Water Never Released to River Airborne Iodine Releases From Auxiliary Building Mitigated 14

15 Recovery Cleanup Actions Building Remediation to Gain Core Access (Barrett Entry) Phased Unique Air and Water Cleanup Systems Created Based on Best Available Technology 15

16 TMI Damaged Core Removal ~

17 TMI Defueling Sequence Core Bore Machine Defuel Can Loading Can Transfers Shipping Cask Transport Core Debris Storage 17

18 TMI Unit 1 Restarted Restarted September 18, 1985 Six and Half Year Process Extensive Operator Training Plant Modifications Extensive Public Regulatory Hearing Process One of Best Operating Reactors Today in US 18

19 Three Mile Island History Reactor Scram: 04:00 3/28/79 Core melt and relocation: ~ 05:00 07:30 3/28/79 Hydrogen Deflagration: 13:00 3/28/79 Recirculation Cooling: Late 3/28/79 Phased Water Processing: :Removed ~1.2MCi Cs137 Containment Venting 43KCi Kr 85: July 1980 Containment Entry: July 1980 Reactor Head removed and core melt found: July 1984 Start Defuel: October 1985 Shipping Spent Fuel: Finish Defuel: Jan 1990 Evaporate ~10 M Liters Processed Water: Cost: ~$1 Billion (YOE) 19

20 Peace On The River Most Painful Experiences Are the Most Teachable We Learned & We Changed Most Stress is Gone- All are Wiser Nuclear Power is Safer Nuclear Power is More Productive 20

21 Fukushima Daiichi Nuclear Power Station Units 5 &6 Common Spent Fuel Pool Dry SNF Storage Units

22 Event Initiation March 11, 2011 About 14:46, a 9.0 magnitude earthquake struck (Plant design basis earthquake: 8.2) Plant safety systems reportedly function satisfactorily. Units 1,2 & 3 Scram & Unit 4 has 100 day old core offloaded into Unit 4 Spent Fuel Pool Subduction Fault ~ 15:45, Seven tsunami waves up to 14 meters high inundated the site, whose design basis was 5.7 meters the reactors and backup diesel power sit roughly 10 to 13 meters above sea level The tsunami & earthquake impacts up and down the northeast coast resulted in tragic loss of 20,000+ lives, damage, and destruction of infrastructure. L. Barrett Numark Assoc 22

23 No Known Seismic Safety Damage Despite Huge Earthquake, Seismic Loads Close to Design Safety Systems Appeared Functional 23

24 Tsunami Waves 24

25 Incoming Wave Behind Reactor Building 15:42 25

26 Wave Behind Reactor Building 15:43:26 26

27 Wave Behind Reactor Building 15:43:54 27

28 Wave Behind Reactor Building 15:44:58 28

29 Wave Behind Reactor Building 15:47 Tank Top 15M 29

30 30

31 Tsunami Size: Main Safety Factor 3/11 15:45 31

32 GE Mark I Reactor Building Boiling Water Reactor Design At Fukushima Daiichi Secondary Containment Refueling Floor Spent Fuel Pool Steel Containment Vessel Reactor Vessel Primary Containment Suppression Pool (Torus) 32

33 Browns Ferry Primary Containment 33

34 Post Tsunami U 1 4 Conditions No AC Power (~15:45) No Unit 1 & 2 DC & Partial Unit 3 DC Power No Control room Lighting (flashlights) Salt Water Flooded EDGs & Switchgear Salt Water Destroyed Service Water Pumps & Switchgear Unit 1 Isolation Condenser Valve Problems Spotty Instrumentation Readings L. Barrett Numark Assoc 34

35 Battery Power Control of Steam Driven Reactor Core Isolation Cooling System In Units 2 &3 (Unit 1 Had Isolation Condenser which Operators Stopped) Unit 1 Isolation Condenser CST? Slide 35 3/11 15:45 to ~ 3/11 24:00 JST

36 Actions to Extend DC Power For Control Scavenged Truck Batteries To Maintain Reactor Instrumentation Control Room Operator During Black Out 36

37 Battery Power Exhausted Core Uncovers and starts to overheat Suppression pool (wet well) becomes saturated 3/12 ~02:00 JST Slide 37

38 Venting Primary Containment Filter H2 & Steam H2 & Steam? Refueling Bay Core Overheated Primary Containment Pressure~ 3/12 H2 & Steam Uncertain Command & Control Actions & Unit 1 Vent Valve Operability 3/12 ~05:30 U1 3/13 ~ 00:00 U2 3/13 ~ 08:40 U3 38

39 Hydrogen Leakage Paths Dry Head Seals Hatch Seals Electrical Penetrations 39

40 Unit 1 Reactor Building Explosion 3/12 15:31 40

41 Unit 3 Reactor Building Explosion 3/14 11:15 41

42 Unit 1 Reactor Building 42

43 Unit 3 Reactor Building Before After 43

44 Fukushima: Reactor Vessel Primary Secondary Containment Sequence Primary Coolant System Primary Containment Secondary Containment Core Over Heats Clad Burst ~900C Clad Oxidize ~1200C H2 Release Partial Melt~1800C 2700C Primary Coolant System Overpressure Vent from Primary Coolant Sys to Primary Containment H2, Steam, & Fission Products (Xe, Kr, I, Cs etc) No Primary Containment Cooling therefore Primary Containment Overpressure Vent to Secondary Containment 44

45 Cores Melted, Slumped Into Lower Head& Likely Failed Some CRD Penetrations Unit 1 RPV Failed Grossly and Units 2&3 Partially Original Core Melted Core dropped RPV Thermal Failures Core on Floor Unit 1 Melt: 3/11~19:00 RPV Fails ~3/12 ~15:00 Unit 2 Melt: 3/14 ~20:00 Unit 3 Melt: 3/13 ~09:00 45

46 Unit 2 & 3 Core Melt Mostly Retained In Vessel? Longer Core Cooling With Turbine Driven Pumps Resulted in Less Aggressive Core Melting Projected Vessel Breach with some Melted core on the floor Minor Concrete Penetration (if any) due to low Melted Core Mass and Flooded Drywell Floor U 2 Water Level is 60cm deep with Very High Gamma Levels (~7000R/hr or 70Sv/hr) Likely exposed Melted Fuel 3/12 46

47 Unit 1 Core Melt to the Floor Loss of Isolation Condenser Cooling: Early Core Melt & Significant Vessel Penetration & Likely Core Drop Unit 1 Corium Penetrated ~70cm (30%) of the 260cm thick floor concrete Above the 4cm steel liner plate. There is 7M of base mat concrete below the liner plate 7M Thick 47

48 Core Cooling Established With Fire Truck Sea Water Injection 48

49 Bleed & Feed Core Cooling Established Seawater Injection Started Using Fire Engine Pump Shift to Fresh Water Injection: To Dissolve Possible Salt Cakes Vapor Venting Water Core Injection Seawater Fresh Rate Rate (1/12) (gpm) (gpm tpd) U1 3/12 20:20 3/ U3 3/13 13:10 3/ U2 3/14 16:30 3/ Tank Condensation/Water Leakage to Reactor Building Turbine Bldg Intake Structure Boric Acid 49

50 Immediately After Unit 3 Explosion 3/14/11 ~10:00AM JST 50

51 Spent Fuel Pool in Reactor Building Unit 4 Pool ~350,000 Gal U4:1331 Assemblies SF ~100 day old U3:514 Assy SF~ 200 Days old U2: 587 Assy SF ~120 Days Old 51

52 Unit 4 Reactor Building 52

53 Unit 4 Spent Fuel Pool Water Sampling Boom Inserting Probe ~ ml Sample Probe ~

54 Unit 4 Spent Fuel Pool Sampling Indicates Little If Any Fuel Damage Low Cesium Levels in 90Bq/ml Water Level Lowered For Seismic Safety 54

55 Unit 4 Explosion: H2 From Unit 3 Unit 4 Unit 3 55

56 Dry Storage Cask Facility overhead travelling crane cask trolley storage cask transport vehicle air inlet Relative Low Elevation 56

57 Storage Only Metal Cask Body: γ-ray shield (carbon steel) outer shell primary lid neutron shield (boron-added resin) bottom plate secondary lid cask frame basket (borated-aluminum alloy) Main features Cylindrical forged carbon-steel casks Similarity with transport casks 5-115T 52 Assy Casks & 4-96T 37 Assy Casks Helium filled Steel for γ-ray shield/ resin for neutron shield 57 Borated-aluminum alloy basket for sub-criticality

58 Dry Storage Facility Was Flooded But All 9 Casks Intact 58

59 Fukushima Stabilized Established Recirculation Core Cooling Damaged Pressure Vessel(s) & Containments Mitigating Airborne Releases Mitigating Water Releases Gaining Building Access to Start Recovery Activities Managing Solid Wastes Maintain Personnel Safety: High Rad Areas Addressing Evacuation Zone Situation 59

60 Units 1 4 After U4 Building Explosion 3/16 60

61 Unit 4 Fuel Pool Side 61

62 Unit 3 & Unit 4 62

63 Water Spray to Unit 3 Pool Area 63

64 Unit 4 Reactor Building Water Injection Boom To Spent Fuel Pool 64

65 Release Periods Based On Site Gamma 1Km U2 Internal Explosion? U3 White Smoke? U4 Building Explosion? U3 Gray Smoke? U1 Explosion? 65