Xenon is commonly described as what in neutron physics?

Xenon is commonly described as what in neutron physics?

• A. Neutron source
• B. Moderator
• C. Neutron poison
• D. Coolant

Answer: (C)

Xenon is described as a neutron poison because it readily and effectively absorbs neutrons, reducing the neutrons available to sustain fission. The key player is Xe-135, a fission product with an exceptionally large thermal-neutron absorption cross-section (millions of barns). When Xe-135 is present, many neutrons get captured by xenon nuclei instead of causing more fission, so the reactor’s reactivity drops. This absorption effect is what defines a neutron poison. Xenon doesn’t generate neutrons, so it isn’t a source, and it doesn’t slow down neutrons like a moderator, nor does it primarily function as a coolant.

Xenon is described as a neutron poison because it readily and effectively absorbs neutrons, reducing the neutrons available to sustain fission. The key player is Xe-135, a fission product with an exceptionally large thermal-neutron absorption cross-section (millions of barns). When Xe-135 is present, many neutrons get captured by xenon nuclei instead of causing more fission, so the reactor’s reactivity drops. This absorption effect is what defines a neutron poison. Xenon doesn’t generate neutrons, so it isn’t a source, and it doesn’t slow down neutrons like a moderator, nor does it primarily function as a coolant.