1. Hydrogen is a colorless, odorless gas that is a very dangerous fire and explosion hazard when exposed to heat, flame, or oxidizers.
2. Hydrogen can be flammable or explosive when mixed with air, oxygen, or chlorine.
3. Work cannot be performed in an explosive atmosphere where hydrogen concentrations are above 10% of the lower explosive limit (LEL) but below the upper explosive limit (UEL).
4. At atmospheric pressure, the LEL for hydrogen is 4.1% by volume and the UEL is 74.2% by volume.
5. When using an explosive meter to determine the presence of hydrogen, the instrument operation manual must be consulted to determine the exact meter readings that correspond to the LEL and UEL for hydrogen.
6. Only individuals trained as atmosphere testers for habitability purposes in accordance with procedures or an industrial hygienist shall conduct monitoring for the presence of hydrogen. Procedures must be consulted for limits on in-line monitoring systems.
7. Hydrogen may be found in several plant systems. These include the reactor coolant system (RCS) and the turbine generator.
8. Hydrogen may be produced as a byproduct in the battery rooms and when sulfuric acid contacts bare metal, such as in unlined sulfuric acid tanks or lines.

General Guidelines

1. Pre-job briefs shall include a discussion of safe work practices for the system and current conditions.
2. A clearance shall be used that provides protection for the worker, such as isolating the flow of hydrogen, and provides appropriate protection for plant equipment, such as eliminating static or electrical charges.
3. Maintenance of hydrogen-related systems shall be in accordance with plant procedures.
4. Non-sparking tools and intrinsically safe equipment shall be used when working with hydrogen.
5. Special care shall be required if initial tests indicate hydrogen concentrations above the UEL. In that case the atmosphere shall be first inerted and then purged before work begins.

Working on Systems Containing Hydrogen

1. Isolate the hydrogen source if possible.
2. Before beginning work, systems containing hydrogen shall be purged and atmospheric concentrations verified below the LEL.
3. In the reactor coolant system at Plants Vogtle and Farley (only), the H2 concentration shall be verified at less than 5cc/kg before opening the system for work.
4. Fleet Safety; Site Safety; and plant management shall be contacted prior to repairing a hydrogen leak if the source cannot be isolated.
5. Identified hydrogen leaks may be deemed manageable. These areas shall be isolated from general employee access, clearly marked as hazardous, and have appropriate clearances to ensure that the system is not breached without appropriate precautions, such as isolating the source, ventilation, or eliminating ignition sources.

Repairing Leaks with Hydrogen Gas Present

1. Observe the General Guidelines above.
2. If possible, stop the hydrogen supply and/or purge the system to eliminate the hydrogen source.
3. Continuously ventilate the immediate work area to maintain the hydrogen concentration below the LEL.
4. If above the UEL, the atmosphere shall be inert prior to ventilation.
5. Individuals familiar with the system shall evaluate each hydrogen leak to ensure safe ventilation.
6. Sample the atmosphere to determine the hydrogen concentration. Continuous monitoring may be required.