•Loading Tc-99 to PWR is equivalent to introducing extra poisons to PWR.•Coating Tc-99 on the PWR fuel rods can cause less effect on keff of PWR.•A thin layer coating of Tc-99 on PWR fuel rods is the optimal loading pattern.•Optimal coating thickness of Tc-99 on PWR fuel rods is between 0.00488 and 0.0065 mm.Based on the EFTTRA-T2 experiment results, we study the transmutation characteristics of pressurized water reactors (PWR) after coating a thin layer of Tc-99 on the fuel rods. Our calculation shows that for the same Tc-99 loading amount, the effect on the PWR keff after coating Tc-99 on the PWR fuel rods is much less than that of the homogeneous addition of Tc-99 to uranium dioxide nuclear fuel. If we just coat 0.2λc (0.0065 mm) thickness Tc-99 on PWR fuel rods, the total Tc-99 coating amount is about 291.37 kg, this is approximately equivalent to the 4 PWR Tc-99 annual outputs, and the system keff merely decreases to 0.98530.Loading Tc-99 to the PWR is equivalent to introducing extra poisons to PWR system to control excess reactivity, some control poisons like boric acid concentration in primary coolant or burnable poison rods in fuel assemblies are needed to be removed to keep the reactor in criticality. As Tc-99 coating thickness increases from 0.05λc to 0.2λc, no matter which substitution pattern is used, B16→12 or C16→12, the system keff variations are almost the same and can return to criticality again after removing corresponding burnable poison rods from fuel assemblies. For coating 0.15λc or 0.2λc thickness on the fuel rods of PWR, the system keff is slightly below the criticality either in B16→12 or C16→12 substitution pattern, we may reduce the concentration of the boric acid slightly to let the system in criticality again.Our calculation results indicate that the optimal coating thickness of Tc-99 on PWR fuel rods is probably between 0.15λc to 0.2λc, i.e. 0.00488–0.0065 mm.