AbstractQuick replacement has been accomplished by using a shape memory alloy (SMA) coupling in the conceptual design of a cassette compact toroid reactor (CCTR). Further, by using an SMA driving element, a compact large gate valve can be newly devised. This gate valve will enable in-situ handling without breaking vacuum, so that the baking of the vacuum boundary for every replacement becomes unnecessary, except the initial baking. In these applications of SMA, the compacting and quickly replaceable technology that are needed for dealing with the problems associated with very high neutron loading in a compact reactor become available by using presently available or promised materials rather than an assumed material.