What is the most prevalent hydrogen source after a design basis LOCA (chronic source of hydrogen)?

• A. Radiolytic Decomposition of Water
• B. Radiolysis of Water
• C. Electrolysis of Coolant
• D. Hydrogen Diffusion in Containment

Answer: (A)

Hydrogen generation in containment after a design-basis LOCA comes mainly from water molecules being split by ionizing radiation from decaying fission products. This radiolytic decomposition of water produces hydrogen and oxygen continuously as long as the radiation field remains, making it the chronic source of hydrogen in the post-LOCA period.

Electrolysis of coolant would require an external power source and active electrical systems, which are not reliably available in that scenario, so it isn’t the dominant long-term source. Hydrogen diffusion describes how hydrogen moves through containment, not how it is produced. The term radiolytic decomposition of water is simply another way to describe the same radiolysis process, which is the ongoing generation mechanism governing this situation.