The problem of estimating plutonium temperature by an iterative procedure based on the special trans functions theory has been studied in some detail. In theory, the differential linear plutonium temperature equation can be effectively reduced to a non-linear functional transcendental equation solvable by special trans functions theory. This approach is practically invariant under the starting plutonium temperature value. This is significant, because the said iterative special trans functions theory does not depend on the password data of the plutonium cargo. Obtained numerical results and graphical simulations confirm the applicability of such approach