Summary of "The SL-1 Reactor Incident" Episode
Stuff You Missed in History Class
Hosted by Holly Fry and Tracy B. Wilson
Released on December 18, 2024

1. Introduction

In the episode titled “The SL-1 Reactor Incident,” hosts Holly Fry and Tracy B. Wilson delve into one of the most tragic and least discussed nuclear accidents in U.S. history. They explore the circumstances leading up to the incident, the disaster itself, and its lasting impact on nuclear safety protocols.

2. Background and Purpose of the SL-1 Reactor

The Stationary Low Power Reactor Number One (SL-1) was a small boiling water reactor located at the National Reactor Testing Station, now known as the Idaho National Laboratory, about 40 miles west of Idaho Falls, Idaho. Established in 1949 by the Atomic Energy Commission, the testing station was designed to research, build, and test various nuclear reactors in a remote area.

Holly Fry explains:

"The SL1 was a 3 megawatt reactor designed for an output of 200 kilowatts of net electricity and 400 kilowatts of energy in the form of heat."
[08:15]

The SL-1 reactor was developed in response to a 1955 Department of Defense request for a nuclear power plant to support the Defense Early Warning system (DEW Line), a chain of radar stations across the Arctic aimed at early detection of Soviet aircraft or missile attacks during the Cold War.

3. Reactor Design and Operational Challenges

The SL-1 reactor's design prioritized practicality, efficiency, and reliability. However, several design flaws and operational challenges plagued its functionality:

• Burnable Poisons: The reactor used boron alloy strips as burnable poisons to manage reactivity. Over time, these strips warped, causing boron to flake off and settle at the reactor's bottom, disrupting reactivity calculations and affecting water seals around drive shafts.
  Holly Fry notes:

  "The boron that was flaking off was affecting the reactivity of the fuel in unpredictable ways."
  [11:33]

• Control Rods: Unlike most reactors that utilize numerous control rods for fine-tuned regulation, the SL-1 relied on only five control rods, one of which could independently manage the reactor's criticality. These rods began to exhibit "stickiness," getting stuck about 2% of the time, leading to reliability issues.
  Savannah Guthrie states:

  "Once they got into the reactor room, their radiation detectors maxed out at the highest possible readings."
  [23:56]

By December 1960, the stickiness of the control rods had become a significant concern, with over 30 incidents recorded in just November and December, leading technicians to implement manual rod travel exercises to keep the rods moving smoothly.

[14:26]

4. The Night of the Incident

On January 3, 1961, during the reactor's restart procedure after a holiday shutdown, three men were on duty:

• CB Richard C. Leg (Dick Legg): Navy shift supervisor with limited experience in nuclear engineering.
• Army Specialist John A. Burns III (Jack Burns): More experienced but known for a volatile temper.
• Army Specialist Richard Leroy McKinley: A trainee with no background in nuclear operations.

The procedure to restart involved reconnecting the reactor’s rack and pinion system, a delicate process requiring precise movements. According to Savannah Guthrie:

"For unclear reasons, while doing this process for the central control rod, Burns suddenly raised it more than 20 inches, rather than the few inches that were required."
[21:17]

This over-extension caused the reactor to enter a prompt critical state, leading to an explosive surge in power—over 6,000 times the reactor's rated output. The resulting steam shaft explosion vaporized water in the reactor, causing a water hammer that physically lifted the reactor building off its foundation. Approximately 20% of the reactor’s radioactive fuel melted, displacing the fuel rods and leading to catastrophic containment failure.

[22:11]

5. Immediate Aftermath and Rescue Efforts

Emergency alarms triggered by radiation detectors alerted nearby Atomic Energy Commission fire stations, but initial responders mistook the alarms for false alerts due to prior malfunctions. Upon arrival, firefighters found the exterior undamaged, aside from steam rising from the roof, and no immediate signs of disaster inside.

As they entered with protective gear, radiation levels began to climb:

• Initial Response: Firefighters initially did not detect dangerously high radiation levels, but upon reaching the reactor's stairwell, their detectors maxed out.
  Savannah Guthrie recounts:

  "Radiation alarms were going off when they got into the building."
  [23:56]

• Health Physicists: Specialized radiation safety experts arrived but initially had to withdraw due to insufficient protective equipment. It wasn't until additional health physicists with enhanced gear arrived that rescue operations could proceed, albeit with strict time limits due to lethal radiation exposure rates.

In the reactor room, firefighters discovered two bodies—Richard McKinley, who was still breathing, and another man pinned to the ceiling. Tragically, McKinley later succumbed to his injuries, contaminated by intense radiation, while efforts to locate the third victim, Dick Legg, resulted in his eventual death six days later.

Holly Fry explains:

"Burns and Leg were buried in private cemeteries, and McKinley was buried at Arlington National Cemetery."
[31:37]

6. Cleanup and Decontamination

Following the disaster, a massive cleanup operation commenced:

• Scope: The cleanup involved over 800 personnel working to decontaminate eight support facilities, a water storage tank, fuel storage tanks, an electrical substation, and other infrastructure.
  Holly Fry states:

  "This was an enormous project with more than 800 people involved."
  [37:19]

• Methods: Techniques included scrubbing surfaces to remove radioactive debris, painting or concreting contaminated areas, and securely burying irreparable materials on-site. Remote operations were employed to handle the reactor core and other highly radioactive components safely.

• Duration: The decontamination and decommissioning process spanned 18 months, involving meticulous planning and execution to ensure safety and effectiveness.

Despite official reports claiming minimal radiation spread, radioactive isotopes like iodine were detected in surrounding communities, raising concerns about long-term environmental and health impacts.

7. Investigations and Theories

Investigations into the SL-1 incident revealed multiple potential causes, though definitive conclusions remain elusive:

• Control Rod Mismanagement: One theory posits that Burns, while attempting to free a stuck control rod, inadvertently moved it too far, causing the reactor to go prompt critical. However, tests and mock-ups suggested this was unlikely.

• Supervisory Errors: Another possibility involves shift supervisor Dick Legg's actions or oversight. Legg’s known issues with anger and possible conflicts with Burns may have contributed to a lapse in proper reactor handling protocols.
  Savannah Guthrie comments:

  "It's possible that Leg was trying to do two things at once... and that he just didn't realize what the consequences would be."
  [46:50]

• Personal Conflicts: Speculation about personal animosities between Legg and Burns, including reported fights and marital problems, suggested that interpersonal dynamics might have played a role, though evidence remains inconclusive.

Critics argue that the reactor's inherent design flaws made it unsafe regardless of operator actions, emphasizing the "one stuck rod rule" that emerged post-incident to prevent similar disasters.

8. Impact and Legacy

The SL-1 reactor accident had profound implications for nuclear safety and industry practices:

• Regulatory Changes: In response, the Nuclear Regulatory Commission (NRC) implemented stringent safety protocols, including the "one stuck rod rule," ensuring that reactors could not reach criticality with the removal of a single control rod.

• Worker Protections: Unions advocated for enhanced worker safety measures at nuclear facilities, leading to better training, stricter supervisory roles, and improved emergency response plans.

• Reactor Design Reevaluation: The incident prompted a reevaluation of reactor designs, emphasizing redundancy, fail-safes, and the importance of comprehensive operator training to handle complex systems safely.

Despite these advancements, the SL-1 remains a somber reminder of the potential dangers inherent in nuclear technology and the importance of rigorous safety standards.

Conclusion

The SL-1 Reactor Incident stands as a pivotal moment in nuclear history, highlighting the critical need for meticulous safety protocols, thorough operator training, and robust reactor design. Holly Fry and Tracy B. Wilson effectively convey the complexity and tragedy of the event, offering listeners a comprehensive understanding of how this disaster shaped the future of nuclear energy in the United States.

Notable Quotes:

• Holly Fry:

  "The SL1 was a 3 megawatt reactor designed for an output of 200 kilowatts of net electricity and 400 kilowatts of energy in the form of heat."
  [08:15]

• Savannah Guthrie:

  "Once they got into the reactor room, their radiation detectors maxed out at the highest possible readings."
  [23:56]

• Holly Fry:

  "This was an enormous project with more than 800 people involved."
  [37:19]

This episode not only chronicles a catastrophic event but also underscores the evolving landscape of nuclear safety, serving as an educational resource for understanding the delicate balance between technological advancement and safety.