Abstract: According to the design requirements of heat pump evaporating system of nuclear power plant, a set of testing installation was built and corresponding performances and efficiencies of separating process were researched. The results show as follows: the reflux ratio of evaporation and concentration in concentrate has low impact on separating efficiencies of the testing installation. The boron concentration in distillate is less than 0.2 mg/L, which is much lower than the most strict limit value (2 mg/L) of releasing to the environment. The results of radioactive alternative test by using MgSO₄, show that the decontamination factor of the test installation reaches 10⁵. Generally, the performance of separating and decontaminating of test installation is much better than similar devices as known, which provided the feasibility of near-zero releasing for inland nuclear plant.