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one per day. In non-fishing areas of the continental shelf, where the environmental ppc value for the isotope mix on the ion exchange resins is about 3 x 10'Â° nc/ml, the permissible number of releases of ion ex- change resins having the activity reported for the NAUTILUS is com- puted to be about 20 per day. According to the report "Radioactive Waste Disposal from U. S. Naval Nuclear-Powered Ships", the ion exchange resins in the NAUTILUS require replacement about once each six months. Thus, if each of the potential 300 nuclear-powered ships were to discharge their spent ion exchange resins twice each year, in a random spatial distribution over the continental shelf of the eastern United States, the environmental limits for this area would not be exceeded, provided that the total activ- ity on the spent ion exchange resins for each ship would not exceed 50 curies. EVALUATION OF THE OPEN SEA (ZONES 4a AND 4b) For the purposes of this report, the open sea is considered to consist of those regions of the oceans which are more than 12 miles from any land and which have depths greater than 200 fathoms. The open sea undoubtedly has greater capacity to safely receive radioactive wastes than any of the marine environments previously considered. Since the waters of the outer continental shelf are suitable receivers of the low level liquid effluent from nuclear-powered ships, it is evident that no restriction need be placed on the discharge of low level liquid effluent from nuclear-powered ships into the open sea. This statement is valid so long as the activities in the liquid effluent are similar to those observed on the NAUTILUS and predicted for the SAVANNAH. The major source of potential wastes for marine disposal on nu- clear-powered ships are the spent ion exchange resins. According to the report "Radioactive Waste Disposal from U. S. Naval Nuclear-Pow- ered Ships", these resins sink in sea water and also rapidly give up the attached active isotopes to the sea water. It is a basic requirement for the application of the findings of this study that in all cases these resins must sink when released into the sea. In the evaluation of the dispersal of an inoculant in the open sea, using the equations developed by Joseph and Sender, a layer depth of 100 meters is assumed. Since no boundaries exist to restrict horizon- tal diffusion, at least on the scale of concern here, n inequations 5 through 8 would be equal to unity. The value of P, the diffusion velocity, is taken as 1 cm/sec. In determining the total area A. to be used in evaluating the cri- teria expressed by equation 1, it is conservatively assumed that all 300 potential nuclear-powered ships operate in the New York-London route. The area of this route is estimated at 6 x 105 km2 (6000 km x 100 km). The length of the significant time period T is, as in the eval- uations for the inshore and continental shelf areas, taken as 1 month, and t]/2 is taken as 15 days. 44