Abstract: A method for densely packaging an element inside a casing, such that the element-containing casing is suitable for use in the preparation of a radiation source, comprising providing a solution containing ions of said element, positioning a working electrode and at least one counter electrode in contact with said solution, connecting said working electrode and said at least one counter electrode to the negative and positive poles of a power source, respectively, passing an electrical current between said electrodes to electrochemically deposit said element on said working electrode in a geometrical form corresponding to the form of the interior of the casing and concurrently or sequentially loading said casing with said element.