It would not be desirable to prohibit production of heavy water and deuterium in quantity since heavy water is the best moderator of neutrons in the large-scale production of atomic power for industrial uses. Furthermore, such a prohibition could never be enforced, since, as stated, the manufacture of heavy water and the separation of deuterium are relatively simple processes that “may be carried out in small plants which can exist in a variety of locales.” What makes it even more difficult, if not impossible, to detect any violation of such a prohibition is the fact that the raw material for heavy water or deuterium is just plain water. 7. SHOULD THE PROVISIONS OF THE PRESENT UN PLAN RELATING TO INSPECTION, SURVEYS, AND EXPLORATIONS BE MODIFIED TO CONTROL HEAVY WATER AND DEUTERIUM PRODUCTION? The United Nations plan assumes that the production of fissionable material cannot be regulated without strict supervision over the mining of source materials such as uranium and thorium: Without the control of raw materials, any other controls that might be applied in the various processes of atomic energy production would be inadequate because of the uncertainty as to whether or not the international agency has knowledge of the disposition of _all_ raw material. (_Second Report_, p. 30.) Whereas uranium and thorium are needed to produce U-235, [U-233] and plutonium, the production of deuterium is not subject to such limitation of source materials. Only water, the existence of power, and comparatively simple plants are needed for the manufacture of heavy water and deuterium. In view of these facts, can the existing United Nations plan cope with the problem of regulating deuterium production? In commenting upon spot aerial surveys, for example, the _Second Report_ recommends that “the [international] agency shall conduct spot aerial surveys in each period of 2 years over areas not exceeding 5 percent of the territory under the control of each nation or areas not to exceed 2,000 square miles, whichever is the larger. (These area limitations apply to spot aerial surveys only)” (p. 68). If aerial surveys were to be used not only in controlling raw materials but also to help in spotting deuterium and heavy water plants, must they be carried out more frequently than is provided in the existing plan? The _Second Report_ also indicates that a UN inspectorate should be compelled to secure permission, through a warrant procedure, before inspecting “private and restricted property not open to visitation by the population in the locality, and in the case of certain ground surveys and aerial surveys which are additional to others which the agency may conduct without warrant or other special authorization” (p. 60). Do the technical facts surrounding heavy water and deuterium production suggest that such a restriction on an international agency’s authority would have to be modified? AUTHOR’S COMMENT