Reactor Accidents

1
Reactor Accidents

• Noteworthy LOCA Events

2
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

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 Didnt
  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 isnt 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?