Incident Synopsis
A hydrogen explosion occurred in an emergency battery container used to transfer fuel elements. The container had five emergency power batteries. Damage was incurred by the explosion.
Cause
The H2 concentration in the container increased because the battery charger had been left on charge. In addition, the container was placed in an un-ventilated airlock. Ignition of the H2-air mixture was believed to be caused by the relays and micro switches activated when the airlock door was opened.
The charging characteristics of a battery vary with the condition of the battery and are proportional to the ampere-hour capacity of the battery. During charging, when a battery is close to being fully charged, hydrogen and oxygen both offgas in a flammable mixture. Emergency battery containers require adequate ventilation for all operations, or the battery box should be designed to:
- Eliminate all sparking devices
- Ventilate during charging operations,
- Provide inert gas purge and pressurization methods, and
- Provide adequate pressure relief.
Adequate ventilation of battery charging facilities is addressed in the Lessons Learned Corner on this website.