In PWR demineralizer operation, which statement correctly describes pH handling?

• A. The pH goal is greater than 7.2
• B. The pH is greater than 6.9 and adjusted by adding lithium based on boron concentration
• C. The pH is adjusted by adding sodium hydroxide
• D. The pH is maintained by temperature control

Answer: (B)

In PWR demineralizer operation, pH control is tied directly to the boron concentration in the reactor coolant. Boron is present as boric acid for neutron absorption, and as its concentration changes it tends to shift the solution’s acidity. To keep the water in a mildly alkaline range that protects materials from corrosion, lithium hydroxide is added, and the amount of LiOH is adjusted based on how much boron is present. The target is to keep pH above about 6.9, so the system remains corrosion-resistant while boron continues to provide reactivity control. This approach avoids relying on temperature to set pH and prevents introducing excessive sodium or other ions.