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For food organisms which obtain all or part of their food by in- gestion of detritus which has settled on to the bottom (for example the mullet, and some pelecypods and Crustacea), we should take account of the concentration factors from bottom sediments to these organisms. Unfortunately, there are no data on this. However, a conservative as- sumption would seem to be that the concentration factor from bottom sediments to marine food organisms is the same as from water to or- ganisms. Under this assumption, the maximum permissible concen- trations in the bottom sediments, for estuarine and inshore waters which support bottom-feeding organisms used as food for man, will be the same as those tabulated for "environment" in Table 2. Since certain of the radioisotopes with which we have to deal, especially those which occur in particulate form in seawater, may be heavily concen- trated in the bottom sediments, this may prove restrictive on the max- imum permissible quantities which may be introduced into the super- jacent waters. WASTES FROM NUCLEAR-POWERED SHIPS The Maritime Administration's report (1959) gives data on the expected quantities of various nuclides in the primary cooling water and in the ion-exchangers of N. S. SAVANNAH*. In Table 3 pertinent data extracted from this report are tabulated for those isotopes in the primary system which present the greatest potential hazard through ingestion in marine food organisms. For the corrosion product nu- clides, the report gives the concentration in the system. From this and 'from the volume of the system (3.9 x 107 ml) the total quantity in the primary coolant has been calculated and tabulated. For the fission products (assuming 1,530 grams of exposed fuel, 100 days operation, and normal purification) the report gives the total quantity of each iso- tope in the system. These also are tabulated, with the corresponding calculated concentrations in the system. Since according to the Maritime Administration's report there will be 290 ft' of discharge water due to expansion at each start-up, it is possible to compute the resulting total amounts of each of the im- portant isotopes which could be displaced per start-up. These values are tabulated in Table 3. They may be used together with data from Table 2 to compute minimum necessary dilution volumes. With dis- charge in an environment (such as the open sea) where the accumula- tion would be negligible, the minimum necessary dilution volume will be obtained by dividing the partial permissible concentration for the particular subdivision of the marine environment into the amount dis- charged per start-up. For the discharge into a restricted segment of the sea having only slow exchange with the open ocean waters, more complex procedures, discussed later, must be followed. â¢Since completion of this report, subsequent re-evaluation of the probable character and activity of the primary coolant and the ion exchange resins has been issued by the Oak Ridge National Laboratory (1959). While the ORNL report includes somewhat different values for the activity in these potential wastes, the general conclusions arrived at here remain unchanged. 23
TABLE 3 IMPORTANT ISOTOPES IN REACTOR COOLANT WATER, N. S. SAVANNAH (based on estimates made in the Maritime Administration's report, 1959) Isotope ppc value for coastal waters (kic/ml) Concentration in primary coolant (Uc/ml) Total amount in primary coolant (curies) Amount displaced per start'up* (curies) Corrosion Products Co 60 3x io'9 1.2 x IO'2 4.6 x lO'1 9.8 x lO'2 Fe55 8x io'8 1.1 x IO'2 4.3 x 10Â° 8.9 x IO'2 Fe59 5x IO'9 5.5 x 10'" 2.1 x IO'2 4.5 x IO'3 To 182 4x io'8 1.7x IO'2 6.7 x lO'1 1.4 x io'1 051 2x lO'6 4.0 x 10'2 1.6 3.4 x io'1 Fission Products** Sr90 5x 10'' 1.4 x io'7 .52 x 10'5 1.2 x 10'6 Zr95 3x lO'8 1.4 x 10'6 .52 x 10'4 1.2x I0'5 Ru 106 1 x lO'8 0.9 x IO'5 .34 x IO'3 7.2 x IO'5 Cs 137 4x io'7 1.5 x io'4 .56 x 10'2 1.2 x I0'3 Nb95 5x io'7 1.3 x 10'6 .52 x 10'* 1.1 x IO'5 Ce 144 Ix IO'9 0.8 x io'6 .31 x IO'4 6.5 x 10'6 Weighted ppc value and gross activity for above listed isotopes 2 x IO'8 8 x IO'2 3.6 6.8 x 10'1 * From expansion volume of 290 ft3 ' 8.2 x IO6 ml. ** After 100 days operation, 1,530 grams fuel exposure, with normal purification. 24
In Table 4 are recapitulated from the Maritime Administration's report the corrosion products expected to be present in the ion exchange resins of the SAVANNAH at time of their discharge. If these are dis- posed of in the open sea far from known fishing areas, and if the prob- ability of two such discharges occurring in the same vicinity within a period of several days is negligible, the minimum necessary dilution TABLE 4 IMPORTANT CORROSION ISOTOPES IN DEMINERALIZER AFTER 50 DAYS OF OPERATION, N. S. SAVANNAH ppc value for open sea Total activity Required (non'fishing) in resin dilution vol. Isotope (ne/ml) (curies) in m3 * Fe 59 1 x 10'7 3.8 3.8 x 107 Fe 55 2 x 10'6 75.0 3.8 x 107 Co 60 7xlO'8 75.0 l.lxlO9 Ta 182 1 x 10'6 103 l.Ox 108 Cr 51 5 x IO'5 148 3.0 x 106 Weighted ppc value (for open sea, non' fishing areas) and gross activity for above listed isotopes 3 x 10'7 405 1.4 x 109 * For disposal in open sea, in regions not designated as known fishing areas (Zone 4b). volumes can be calculated by dividing the total activity by the ppc value for the open sea, for regions not designated as known fishing areas. This has been done for the corrosion product isotopes for which data are available. The report "Radioactive Waste Disposal from U. S. Naval Nuclear- Powered Ships" gives information on the actual observed concentrations of the various radioisotopes in the primary coolant and on the spent ion exchange resins for the U.S.S. NAUTILUS. These data are reproduced for the significant isotopes in Tables 5 and 6. The evaluation of permissible rates of discharge of nuclear wastes is complicated by the fact that the potential effluents from nuclear-pow- ered ships are composed of a mix of isotopes which may have additive effects on man. In order to include this feature in later computations, it is convenient to determine a weighted mean ppc value for the isotope 25
TABLE 5 IMPORTANT ISOTOPES IN REACTOR COOLANT WATER, U.S.S. NAUTILUS (average) ppc value for coastal waters (ue/ml) Concentration in primary coolant (Ue/ml) Amount displaced per warm'up * (curies) Corrosion Products Co 60 Fe 59 Cr51 Ta 182 Cu64 3x 10'' 5 x IO'9 2 x 1G"6 4 x 10'8 4 x 10'8 5.7 x 10'* 1.5 x 1C"4 1.0 x 10'5 7.3 x 10'3 1.5 x 10'5 1.1 x 10'5 2.9 x 10'4 1.9 x 10'5 1.4 x 10'2 2.9 x 10'5 Fission Products 1 131 3 x 10'8 5 x IO'9 1 x 10'5 5 x IO'8 1 x 10'7 1 x IO'8 1.9x 10'5 9.5 x lO'8 1.9 x 10'7 1.9 x 10'8 Sr90 Ce 144 Cs 137 1 X 1C"9 4 x 10'7 Weighted ppc value and gross activity for above listed isotopes 4 x ID'8 7.5 x 10'3 * From average expansion volume of 500 gals =1.9 x 10 ml. 1.4+x lO'2 TABLE 6 IMPORTANT CORROSION ISOTOPES IN SPENT DEMINERALIZER, U.S.S. NAUTILUS Isotope Co 60 Co 58 Fe59 Cr51 Mn54 Hf 175 ppc value for open sea Total activity Required (non'fishing) in resin dilution vol. (ue/ml) (curies) in m3 * 7xlO'Â« 10 1.4 x 108 0.5 1 x IO'7 0.5 5.0 x 10* 5x 10'5 0.3 6.0 x 103 0.2 1.0 Weighted ppc value (for open sea, non' fishing areas) and gross activity for above listed isotopes 7x 10 '8 12.5 1.8 x 108 * For disposal in open sea, in regions not designated as known fishing areas (Zone 4b). 26