High efficiency cold traps are desirable to reduce reactor sodium impurities to their lowest practical levels to minimize materials degradation and prevent system flow blockages from occurring. The trap efficiency can be improved by increasing the coefficient of mass transfer in the crystallizer zone, through increasing the turbulence in that region. A highly effective method of accomplishing this, utilizing electromagnetic stirring, was employed in sodium mass transfer studies at General Electric Company under AEC sponsorship. The effect of increasing cold trap turbulence, to achieve calculated Reynolds numbers up to 105, was tested in a loop by measuring hydrogen and oxygen removal rates with the cold trap operated in both turbulent and laminar modes. The results show that electromagnetic stirring increased the conventional cold trap efficiency from ∼51% to ∼99%. Use of this concept permits faster system impurity cleanup with smaller equipment than was possible heretofore.