• WTR was a pressurized tank-type water-cooled/water-moderated test reactor
• Pressurized by head tank 250 ft. in the air
• 60 MWt, designed to test materials and components
• Privately owned
• Each assembly had 200 grams of highly-enriched uranium in uranium-aluminum alloy
• Fuel elements made of 3 concentric rings

• A test was planned to reduce flow and see how the reactor operated
• Power was 40 MW and flow was 15,000 gpm
• Power was reduced to 30 MW and safety system setpoints were adjusted
• Flow was reduced to 5250 gpm, power increased back to 37 MW and then back to 40 MW
• At 8:35 pm, power unexpectely dropped to 17 MW
• Automatic control rods withdrew to upper limit
• Power started increasing again
• Radiation alarms! ☢️😱
• Personnel scramed and secured the plant and evacuated the area

• Gross fission product contamination of primary coolant
• By April 9, the head was raised and scrubbed with carwash brushes
• A three-inch thick shielded platform was constructed
• Fuel was removed, but one assembly was stuck
• It was melted
• Coolant voiding around it explains the power reduction

• Bonding defect from fuel fabrication over 1/2” found able to cause burnout
• Inspections of spare fuel showed tons of big defects, up to 1”
• Solution: improved fabrication tolerances and inspection
• Blister tests insuffucient, ultrasonic inspection required
• Cost increase of fabrication lower than cleanup costs

(Editors, 1960)