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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

Reactor Accidents

Noteworthy LOCA Events


Loss of cooling accidents

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


Stationary low power plant no 1 sl 1 accident
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


Millstone 1 accident
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


Browns ferry 1 and 2 fire
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


Ginna incident
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


Mihama 2 incident
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


Nrx incident
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


Lucens incident
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


Windscale fire
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


St laurent fuel meltdown
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


Hunterston b seawater problem
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


Hinkley point b fuel damage
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


Experimental breeder reactor i ebr 1 meltdown accident
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


Enrico fermi fuel melting incident
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


Examples and problems 5 1
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


Examples and problems 5 11
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


Examples and problems 5 2
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


Examples and problems 5 21
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


Examples and problems 5 22
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


  • Examples and problems 5 23
    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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