Reactor shutdown device

The object of this invention is to shutdown an LMFBR type reactor by surely inserting elements into a reactor core. That is, a reactor shutdown device is usually suspended upwardly by attracting an armature disposed at the top end of fuel elements by means of electromagnets. One or both of the electromagnet and the armature is made such a structure as having a first magnetic member of high permeability and a second magnetic member of high temperature strength. With this constition, since the first magnetic member is disposed, a sufficient magnetic flux density can be obtained at an appropriate current to reduce the residual magnetic flux after disconnecting the current. Further, since the second magnetic member is disposed, the load can be transported through the seocnd magnetic member to reduce the force applied to the first magnetic member having no sufficient high temperature mechanical strength. Accordingly, sufficient attraction force can be obtained and the fuel elements can be disconnected reliably. (I.S.)