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Reactor Accidents

Reactor Accidents. Noteworthy LOCA Events. Light Water SL-1 Millstone 1 Browns Ferry 1 and 2 Three Mile Island 2 ** Ginna Mihama 2 Chernobyl ** Heavy Water NRX Lucens. Gas Cooled Windscale St. Laurent Hunterston B Hinckley Point B Liquid Metal EBR-1 Enrico Fermi

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Reactor Accidents

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  1. Reactor Accidents Noteworthy LOCA Events

  2. Light Water SL-1 Millstone 1 Browns Ferry 1 and 2 Three Mile Island 2 ** Ginna Mihama 2 Chernobyl ** Heavy Water NRX Lucens Gas Cooled Windscale St. Laurent Hunterston B Hinckley Point B Liquid Metal EBR-1 Enrico Fermi ** Will be Covered in Upcoming Lectures Loss of Cooling Accidents

  3. Stationary Low-Power Plant No. 1 (SL-1) Accident • January 3, 1961 • 3 MW • National Reactor Testing Station, Idaho • Control Rods Manually Removed • Reached 20,000 MW in 0.01 s • Destroyed Core, Melted Fuel, Steam/Pressure Explosion • Killed the 3 Military Personnel • Need Control Rod Interlocks • Uncontrolled Reactors are Very Dangerous

  4. Millstone 1 Accident • September 1, 1972 • 660 MWe BWR • Malfunction if Water Purification Systems • Seawater Corrosion to Primary Coolant Loop • Repaired and Resumed Operation • No Injuries or Radiation Release • Need Alternative Cooling Methods

  5. Browns Ferry 1 and 2 Fire • March 22, 1975 • Three 1095 MWe BWRs, Alabama • Worker Performing Leak Tests with a Candle Started a Fire in the Walls • 7 Hours, $10M & 1 year Repair • Burned ~2000 Cables • Alternative Cooling Methods Needed for Core • No Serious Injury or Radiation Release • Segregation of Components and Wiring for Safety and Control

  6. Ginna Incident • January 25, 1982 • 490 MWe PWR, New York State • Loose Metal Object Vibrated and Damaged Steam Generator Tubes • Delayed Coolant Response • Release of Some Radiation (Noble Gases) • No Injuries

  7. Mihama-2 Incident • February 9, 1991 • 500 MWe PWR, Japan • Steam Generator Tube Rupture • Fatigue Failure • Corrosion Debris • Improper Installation of Antivibration Support • Small Release of Radioactive Gas • No Injuries

  8. NRX Incident • December 12, 1952 • 40 MWt CANDU, Chalk River, Canada • Operator Removed Too Many Control Rods • Supervisor Had Them Returned but They Didn’t Complete Enter the Core • Power Rose to 60 – 90 MWt • Low Coolant Flow for Testing • Core Melted and Ruptured • 10,000 Ci Fission Products Dumped in 1M Gallons Water • Need Proper Control Rod Operations

  9. Lucens Incident • January 21, 1969 • 30 MWt, Lucens, Switzerland • Combined Magnox and Heavy Water Reactor • Corrosion of Fuel Rod = Rupture • Molten Cladding Blocked Coolant • Pressure Burst • Need Better Understanding of Chemical Interactions, Reactor Characteristics, and Monitoring

  10. Windscale Fire • October 7-10, 1957 • Plutonium Production • Heating to Anneal Graphite Moderator Defects • Fuel Overheated • Released 20,000 Ci I-131 and Noble Gases • Milk Production Stopped for 6 weeks • Estimated Increase of 30 Cancer Deaths for Every 1M Cancer Deaths • Filter Trapped Some of the Release

  11. St. Laurent Fuel Meltdown • October 17, 1969 • 500 MWt, MagnoxSt. Laurent, France • Improper FuelLoading, Charging Machine Override • Blocked Coolant Channel • Molten Fuel • No Radiation Release Beyond Core • No Injuries • 1 year to Cleanup and Modify the Reactor • Heat Removal is Critical

  12. Hunterston B Seawater Problem • October 11, 1977 • AGR, Hunterston, Scotland • Temporary Testing with Pure Water • CO2 Acidified Water to Cause Corrosion • 8000 L Seawater Entered Reactor Vessel • Repairs Cost £13M and 28 months • Temporary Modifications Should be Properly Analyzed

  13. Hinkley Point B Fuel Damage • November 19, 1978 • AGR • Fuel Loading During Reactor Operation • Vibrations and Pressure Increased Cladding Cracks • Fuel and Heat Removal Failure During Operation • On-Load Refueling Performed at Low Power

  14. Experimental Breeder Reactor I (EBR-1) Meltdown Accident • Novemeber 29, 1955 • First Reactor to Generate Electricity • High Temperature Effects Caused Fuel Pins to Bow Closer Together and Increase Reactivity • Melted 40% of the Core • Fast Reactors Built to Expand Rather than Contract

  15. Enrico Fermi Fuel Melting Incident • October 5, 1966 • 200 MWt LMFBR, Lagoona Beach, Michigan • Guide Plate became Loose and Blocked 2 Fuel Channels • Fuel Melted • No Injury or Outside Release of Radiation • 10,000 Ci Fission Products Released to Sodium Coolant • Need Careful Analysis of Parts in a Reactor

  16. Examples and Problems 5.1 • Decay Heat Removal using PORVs • How Many PORVs are Needed to Release Decay Energy from a 4000 MWt PWR in 100 seconds after Shutdown? • Valve Area = 0.002 m2 • Decay Heat Fraction is 3.2% of Power (Table 2.2) • Maximum Release Rate is 17,000 MW/m2 (Section 4.3.2) • Decay Heat Rate is 128 MW • Flow Area Required = 0.0075 m2 • Therefore, 4 PORVs Would be Required

  17. Examples and Problems 5.1 • Other Problems using Same Equations • Evaluate the Problem for Different Lengths of Time, Operational Power Levels, Flow Areas, or Number of PORVs • Additional Analysis • If 1 PORV Valve Remained Closed, How Long Would it Take to Remove the Decay Heat? • Re-evaluate the Problem if the Efficiency of Energy Release for Each PORV is Reduced

  18. Examples and Problems 5.2 • Evaporation of Coolant • A 3800 MWt PWR is half uncovered due to a small LOCA event; what is the rate of becoming uncovered at 1 h after shutdown? • Void fraction = 0.5 • Fuel occupies 40% of core • Core diameter, d = 3.6 m • Core length, l = 5 m • Pressure, P = 85 bars • Assume uniform heat flux across core

  19. Examples and Problems 5.2 • (V/l)core = (pr2)*(1-0.5)*(1-0.4) = 3.054 m2 • Using Table 2.2 (Heat from core = 1.4%) • 3800 MW * 1.4% * ½ core = 2.66 x 107 W • Latent heat of evaporation at 85 bars • 1.4 x 106 J/kg • Evaporation rate = 26.6/1.4 = 19 kg/s • Density of water at 85 bars • 713 kg/m3

  20. Examples and Problems 5.2 • Volume evaporation rate = 0.0266 m3/s • Uncovery rate • Volume evap rate / volume of core per length • U = 31.4 m/h

  21. Examples and Problems 5.2 • Other Problems using Same Equations • What if heat generation isn’t uniform across the core? • How and why would the evaporation rate change with fluid level in the core? • Additional Analysis • What if the heat generation changed across the cross-sectional area of the core as well?

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