Preventing Accidents Involving Nuclear Chain Reactions that can be Fatal to Workers

Multiple Sites

Nuclear criticality accidents are uncontrolled chain reactions of nuclear materials that can result in fatal radiation doses to workers.


Improving DOE’s Management of Criticality Safety

Our Work

DNFSB conducted criticality safety reviews across the DOE complex. These reviews involve understanding how DOE sites comply with relevant requirements and industry standards.


 

Our Safety Impact

As a result of DNFSB-identified issues, DOE has improved in multiple areas such as uranium accumulation in out-of-service equipment, labeling of legacy containers, tracking material-at-risk, increasing the rigor of criticality safety evaluation bases, and strengthening the interface between criticality safety personnel and other work groups at DOE sites.

Plutonium components staged in a glovebox at Los Alamos National Laboratory and machine coolant piping capped with rubber gloves at Y-12 National Security Complex. These conditions violated nuclear criticality safety requirements.
Pictured: Plutonium components staged in a glovebox at Los Alamos National Laboratory (left); and machine coolant piping capped with rubber gloves at Y-12 National Security Complex (right). These conditions violated nuclear criticality safety requirements.

 

 

Developing National Standards on Nuclear Measurements

Our Work

DNFSB’s Recommendation 2007-1, Safety-Related In Situ Nondestructive Assay of Radioactive Materials, noted that DOE had not established programmatic requirements for performing nondestructive assay measurements, which are relied upon for safely monitoring locations and quantities of nuclear materials inside equipment.

Our Safety Impact

Subsequent to the DNFSB’s Recommendation, the American Nuclear Society issued a new national consensus standard on nondestructive assay measurements for criticality safety.


 

Nondestructive assay measurement of nuclear material holdup.
Pictured: Nondestructive assay measurement of nuclear material holdup.

 

 

Promoting Institutional Knowledge of Nuclear Criticality Safety

Our Work

Over its history, the DNFSB has advocated for DOE to establish and preserve institutional knowledge of good nuclear criticality safety practices. For example, DNFSB identified the need for DOE to develop its critical experiment capability to maintain expertise in criticality safety.

Our Safety Impact

With the DNFSB’s encouragement, DOE’s nuclear criticality safety experts routinely provide criticality safety training to DOE workers.


 

Former Board members Brown and Bader perform nuclear criticality measurements as part of a DOE hands-on training course.
Pictured: Former Board members Brown (left) and Bader (right) perform nuclear criticality measurements as part of a DOE hands-on training course.

 

Last Updated: March 23, 2026