The small fast reactor 4S adopt the high temperature electromagnetic pump (EMP) as a primary main pump, which is superior in reliability, safety and economy. The studies about 4S EMP are carried out for the realization of the free maintenance during 4S operating time and the backup power system ensuring flow coast down at the reactor trip. The 4S EMP involve large dimension coil and short height stator in comparison with existing EMP. In FY2008, the 4S prototype EMP was manufactured as same dimension as practical one to confirm manufacturability. After manufactured, the magnetic flux density was measured. In the result, analytic value almost agreed with actual measurement value. The electromagnetic characteristic was confirmed as design at room temperature and atmosphere.
