Which of the following are purification processes used in reactor coolant systems?

• A. Letdown/Makeup
• B. Filtration
• C. Ion Exchange
• D. All of the above

Answer: (D)

Purification of reactor coolant relies on several complementary methods to keep the primary loop clean and chemically controlled. Letdown and makeup continuously refresh the coolant: a controlled portion is discharged (letdown), passed through purification stages, and makeup water is added to maintain volume while removing or diluting contaminants carried over from the loop. Filtration provides physical removal of particulates and corrosion debris that can foul surfaces or elevate radiation fields. Ion exchange removes dissolved ions—such as metal ions and other dissolved species—so conductivity stays low and corrosion products are kept in check. Since each method targets a different impurity category, all of these purification steps are used in reactor coolant systems.