A Hilarious Nuclear Criticality Incident at Los Alamos

The 2011 Los Alamos Incident

The video investigates a 2011 safety incident at Los Alamos National Laboratory. A photograph showed several plutonium rods grouped together inside a glove box—a sealed workspace used to handle radioactive material. Based on the image, the narrator estimates that the amount may have exceeded a commonly cited 5 kg critical-mass limit. However, the narrator stresses that this figure depends on the material’s shape and surroundings and cannot, by itself, establish whether the arrangement was critical.

The photograph was reportedly taken to show senior management how much plutonium had been produced. The narrator argues that several safeguards appear to have failed: the material was grouped in a hazardous configuration, normal movement procedures were not followed, and a senior manager reportedly told staff to continue working rather than evacuate. The room was eventually evacuated after an employee contacted the laboratory’s criticality expert.

In 2013, the Department of Energy learned that nearly all employees responsible for criticality safety at the laboratory had resigned. The narrator presents this as part of a broader pattern of safety and security concerns, with major consequences for plutonium operations.

How Criticality Works

When a plutonium-239 atom undergoes fission, it releases energy and additional neutrons. Those neutrons can trigger further fissions, producing a chain reaction. Whether the reaction grows depends on factors including the amount and arrangement of fissile material, and how neutrons behave around it.

Key concepts include:

• Subcriticality: Too many neutrons escape or are absorbed for the chain reaction to sustain itself.
• Criticality: Conditions allow a self-sustaining chain reaction.
• Neutron reflection: Nearby material, including water or a person’s body, can send neutrons back toward fissile material.
• Neutron moderation: Water can slow neutrons, making them more likely to cause fission.
• Geometry and concentration: For fissile material in solution, mass alone is not enough to determine risk. The concentration and shape of the container also matter.

A brief criticality excursion can release dangerous neutron and gamma radiation. The resulting heat may disrupt the arrangement and stop the reaction, but not before exposing nearby people to radiation.

Historical Case Studies

Los Alamos, 1944: The “Lady Godiva” Experiment

Researchers stacked uranium-hydride blocks to study how close the assembly was to criticality. When a neutron counter was switched off, Otto Frisch noticed that nearby signal lights were glowing steadily rather than flashing. His body reflected some neutrons back toward the assembly. He quickly scattered the blocks, preventing an accident. The episode illustrates how people and nearby materials can affect criticality.

Siberian Chemical Plant, 1978

Workers handling plutonium ingots were supposed to follow written instructions and store the ingots separately in cadmium-coated containers. Cadmium absorbs neutrons. Under production pressure, one operator gave verbal instructions that bypassed the written process. Four ingots ended up in one container, and a brief criticality event followed.

The operator lost both arms below the elbows, and seven other workers received radiation doses.

Windscale, 1970

During a plutonium-recovery process, plutonium-rich solvent accumulated unexpectedly in a transfer tank. The cause was never established, though a backflow route was suspected. The solution briefly became critical when flow stopped, then returned to a subcritical state as the contents mixed.

Staff evacuated, and engineers later inspected and drained the vessel remotely. The event highlighted the value of monitoring equipment and remote procedures for unexpected configurations.

Safety Lessons

These incidents illustrate that criticality safety depends on multiple layers, not simply on asking workers to be careful:

• Control the amount and arrangement of fissile material in workspaces and containers.
• Use physical safeguards, such as suitable storage containers and neutron-absorbing materials, rather than relying solely on written warnings.
• Follow documented procedures and checklists for handling and moving material; avoid informal substitutions or verbal instructions.
• Recognize that surroundings matter: water, people, and other materials can change how neutrons behave.
• If a potentially hazardous configuration is discovered, stop work and evacuate. Do not try to rearrange the material by hand; have qualified experts assess it and use remote methods where appropriate.
• Maintain detection and monitoring systems, and ensure alarms are acted on.

Root Causes and Broader Argument

The narrator cautions against assigning blame to one technician, manager, or photographer, especially given the incomplete public record. Instead, the video focuses on organizational conditions. It notes that Los Alamos was then operated by a for-profit contractor and raises questions about how production targets, contracting structures, morale, secrecy, and a weakened safety culture may interact. These points are presented partly as the narrator’s interpretation, not as definitively established explanations for the incident.

The video closes with a 1957 report criticizing the idea that a worker’s hand movement could bring a system to criticality. It argues that remote methods and accumulated safety knowledge should make such situations unnecessary.

Speakers and Sources Featured

• Speaker: The video’s narrator and creator, who explains the science, recounts the incidents, and offers commentary.
• Center for Public Integrity: A 2017 article is identified as a key source for information about the 2011 Los Alamos incident.
• Los Alamos National Laboratory website: Cited for information about material-handling procedures.
• Criticality-safety guidance and industry standards: Referred to in the discussion of mass limits, safe handling, and controls.
• Historical reports and accounts: The video refers to an account by the Siberian-plant operator, reports on the Windscale incident, and a 1957 report about the Lady Godiva device.
• Historical figure discussed: Otto Frisch is described in the 1944 account; he is not presented as a speaker in the video.