PURPOSE: To reduce thermal stress from a core section by interposing an elastic body energizing the clearance of heat transfer plates so as to be expanded between the heat transfer plates while a large number of flexible heat transfer films promoting heat transfer between the heat transfer plates are disposed in tension between the heat transfer plates.

CONSTITUTION: A thermal conduction device 11 in which stainless plates as a pair of heat transfer plates 8a, 8b are arranged so as to be oppositely faced and elastic bodies 9 energizing the clearance of the heat transfer plates 8a, 8b so as to be expanded are interposed between the heat transfer plates 8a, 8b while a large number of flexible heat transfer films 10 having thermal conductivity higher than air and made of aluminum foil promoting heat transfer between the heat transfer plates 8a, 8b are disposed in tension between the heat transfer plates 8a, 8b is formed, and the thermal conduction device 11 is fast stuck and fitted to the clearance of an external core 5 and an external duct 1, thus constituting an electromagnetic pump. Heat generated in a coil 4 and the external core 5 is conducted through the external core 5 with the operation of the electromagnetic pump, and reaches to the heat transfer plate 8b. The heat is passed through the flexible heat transfer films 10 and reaches to the heat transfer plate 8a, and is further transmitted through the external duct 1 and is dissipated in liquid metallic sodium flowing in an annular flow path 3.