Which of the following is NOT a source of activation products in a reactor coolant system?

• A. Neutron Activation of Corrosion Products
• B. Neutron Activation of Structural Materials
• C. Neutron Activation of Coolant Itself
• D. Fission Products

Answer: (D)

Activation products in a reactor coolant system come from neutron interactions with materials that are in the loop. When neutrons activate corrosion products, structural materials, or even the coolant itself, stable nuclei are turned into radioactive isotopes. For example, oxygen in the coolant can form short‑lived isotopes like 16N, and metals in corrosion deposits or the reactor’s components can produce isotopes such as Co-60 or Mn-56 through neutron activation. The coolant itself can also be activated, contributing additional activation products. Fission products, on the other hand, are created directly by fission reactions in the fuel, not by neutron activation of materials in the coolant loop. They can contaminate the coolant only if fuel leaks occur, but they are not activation products of the coolant system.