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however, it may tend to concentrate them in the bottom sediments from which they may be returned to the water or taken up by bottom-living food organisms. Biological effects: A number of elements are concentrated in the bodies of organisms by several orders of magnitude over their abun- dance in natural waters. Radio-isotopes of such elements are, there- fore, concentrated in man's aquatic foods. As pointed out by Ketchum (1957), the concentration of certain elements by organisms, subsequent migration of these organisms, and gravitational effects on their excreta and remains, all combine to produce a circulation of these elements which differs from the circulation of the water. This is of particular importance in inshore and estuarine waters where, as shown by Ketchum, there may result an accumulation of an element greater than that in the source waters. Revelle and Schaefer (1957) have noted also that "The time required for removal of radioactive materials from estuaries will, in general, be much greater than the flushing time of substances that are not absorbed by organisms or taken up by bottom sediments". MAXIMUM PERMISSIBLE CONCENTRATIONS IN SEA FOOD As we have noted above, the maximum permissible body burdens of various radio-isotopes and the corresponding maximum permissible concentrations in drinking water as applicable to the general public (calculated under the assumption that this is the only source of the in- gested isotope) have been tabulated in Title 10, Chapter 1, Part 20, Code of Federal Regulations, Revised 1959 (proposed). These are re- capitulated in Table 2 for a number of isotopes, including the more im- portant corrosion products and fission products which may occur in wastes from shipborne reactors. Two additional considerations are required in arriving at the maximum permissible concentrations in seafood which would be per- mitted to originate from waste disposal operations of nuclear-powered ships. The first of these involves estimation of the amount of seafood which would be ingested, per unit of time, by a segment of the popula- tion. The second involves allocating to ship waste disposal a certain share of the maximum permissible dose which man may receive from the utilization of atomic energy. As has been pointed out earlier, food from the sea is not the only source of ingestion of radio-isotopes, and nuclear-powered ships are not the only potential source of introduction of radioactive material to the sea. Therefore, it is necessary to de- cide how much of the maximum permissible intake shall be allocated to the results of waste disposal from nuclear-powered ships. Since the maximum permissible concentrations so determined apply only to that activity originating from nuclear ship operation, they are actually partial permissible concentrations (ppc's) and are so des- ignated in this report. The evaluation of how much of the maximum permissible intake should be allocated to the results of waste disposal from nuclear- 15
TABLE 2 DATA ON CERTAIN RADIOISOTOPES WHICH MAY BE PRESENT IN WASTE FROM NUCLEAR POWERED SHIP REACTORS Half Isotope Life Cobalt 60 5.2 y Iron 55 2.9 y Iron 59 45 d Chromium 51 27 d Copper 64 12.8y Tantalum 182 112 d Zinc 65 250 d Cesium 137 33y Strontium 90 28 y Zirconium 95 65 d Niobium 95 3Â«d Ruthenium 106 ly Cerium 144 280 d Iodine 131 8d Maximum* Permissible mpc in Partial Permissible Concentration in Mori ne Food Total Body Drinking** for Cases (see footnotes): Burden Water (D (2) (3) (4) (5) (ue) (ue/ml) (uc/g) (uc/g) <ue/g) (ne/g) (uc/g) 10 3x10'5 3x10'5 6x10'5 3xlO'4 IxlO'4 7xlO'4 IxlO3 8xlO'4 8xlO'4 2xlO'3 8xlO'3 4xlO'3 2xlO'2 20 SxlO'5 SxlO'5 IxlO'4 SxlO'4 2xlO'4 lxlO'3 800 2xlO'3 2xlO'3 4xlO'3 2xlO'2 IxlO'2 SxlO'2 10 2xlO'4 2xlO'4 4xlO'4 2xlO'3 lxlO'3 SxIO'3 7 4x10'5 4xlO'5 SxlO'5 4xlO'4 2xlO'4 lxlO'3 60 KIO'4 1xlO'4 2X10'4 IxlO'3 SxlO'4 2xlO'3 30 2x10'5 2x10'5 4xlO'5 2xlO'4 IxlO'4 SxlO'4 2 lxlO'7 lxlO'7 2xlO'7 IxlO'' SxlO'7 2xlO'6 20 6x10'5 6x10'5 IxlO'4 6xlO'4 3xlO'4 IxlO'3 40 IxlO'4 IxlO'4 2xlO'4 lxlO'3 SxlO'4 2xlO'3 3 IxlO'5 lxlO'5 2x10'5 lxlO'4 SxlO'5 2xlO'4 5 IxlO'5 IxlO'5 2x10'5 lxlO'4 SxlO'5 2xlO'4 7x10'' 3xlO'6 3xlO'Â« 6x10'' 3x10'5 2x10'5 7x10'5 Concentration Factor*** Sea Water to; Partial Permissible Concentration in Sea Water for Cases (see footnotes): Invertebrates Fish Fish (D (2) (3) (4) (5) Isotope (edible parts) (soft parts) (skeleton) (ue/ml) (uc/ml) (uc/ml) (ue/ml) (uc/ml) Cobalt 60 104 3x10'' 6x10'' 3x10'8 IxlO'8 7x10'8 Iron 55 104 103 SxlO3 SxlO'8 2xlO'7 BxlO'7 4xlO'7 2xlO'6 Iron 59 104 103 SxlO3 Sx10'' IxlO'8 SxlO'8 2x10'8 IxlO'7 Chromium 51 103 (6) 2xlO'6 4x10'* 2x10'5 MO'5 SxlO'5 Copper 64 SxlO3 10Â» 10* 4xlO'8 SxlO'8 4xlO'7 2xlO'7 IxlO'6 Tantalum 182 103 (6) 4xlO'8 SxlO'8 4xlO'7 2xlO'7 IxlO'6 Zinc 65 SxlO3 103 3xl04 2x10'8 4x10'8 2xlO'7 IxlO'7 SxlO'7 Cesium 137 50 10 4xlO'7 8xlO'7 4x10'* 2x10'' IxlO'5 Strontium 90 10 1 200 Sx10'' IxlO'8 SxlO'8 2x10'8 lxlO'7 Zirconium 95 2xl03 (7) 3xlO'8 6xlO'8 3xlO'7 IxlO'7 7xlO'7 Niobium 95 200 100 SxlO'7 IxlO'6 SxlO'6 2x10'* lxlO'5 Ruthenium 106 103 (7) IxlO'8 2xlO'8 IxlO'7 SxlO'8 2xlO'7 Cerium 144 SxlO3 (7) 12(8) IxlO'9 2x10'' IxlO'8 5x10'' 2x10'8 Iodine 131 100 10 3xlO'8 6xlO'8 3xlO'7 lxlO'7 7xlO'7 " From Title 10, Chapter 1, Part 20, Code of Federal Regulations, Revised, 1959 (proposed). â¢ â¢ From Title 10, Chapter 1, Part 20, Code of Federal Regulations, Revised, 1959 (proposed), for Hie general public. Same as 1 10th the values given in Handbook 52, Revised, 1959 (proposed). *** Data from Revel I e at o[. (1957); Ketchum and Chipman (1958); except as otherwise noted below. (1) Harbors, estuaries, and inshore waters within 12 miles of the coast line (Zone 1 and Zone 2). (2) The outer continental shelf, beyond 12 miles from the shore line, in known fishing areas (Zone 3a). (3) The outer continental shelf, beyond 12 miles from the shore line, in regions not designated as known fishing areas (Zone 3b). (4) The open sea, in known fishing areas (Zone 4a). (5) The open sea, in regions not designated as known fishing areas (Zone 4b). (6) No experimental data. Values approximated on basis of experimental data on biologically similar elements. (7) Calculated from Martin (1957). (8) Dunster (1956). 16
powered ships can be considered in two parts. The first involves an allocation to sea disposal in general. Essentially there are three en- vironments from which man might receive radioactivity; these are the atmosphere, the land (including food and water from the land), and the sea. It is assumed here that sea disposal from all potential sources should be limited to a contribution to a selected portion of the popula- tion of no more than one-third of the maximum permissible intake for such a selected portion of the population. This allocation is not in- tended to specify the manner of subdividing the remaining two-thirds between land and atmosphere. The evaluation of the remaining factors is somewhat different for each of the major subdivisions of the marine environment. In the following paragraphs the special considerations which apply to the in- shore areas, to the continental shelf, and to the open sea are presented. Special considerations related to harbors, estuaries and other inshore waters and to the continental shelf: An extremely conservative approach is warranted for these waters for the following reasons. 1. Most of the harvest of food from the sea comes from these waters, including the entire harvest of some sedentary forms, such as oysters, scallops, clams and seaweed, which concentrate certain ele- ments by very large factors. Some large segments of the world popula- tion receive the bulk of their protein requirements from this part of the sea. 2. With the continuing development of atomic power, there will inevitably occur a requirement for some introduction of radionuclides into the inshore waters from land based establishments; the cost of avoiding this may be prohibitively high. Thus only a portion of the total potential receiving capacity of these waters is available for waste dis- posal from nuclear-powered ships. 3. In the case of a nuclear war, one of the least contaminated sources of food will be the sea. It is, therefore, desirable to keep the radioisotope contamination prior to this as far below the maximum per- missible level as possible. Some areas of the continental shelf do not contribute materially to the commercial fisheries, and hence some subdivision of this environ- ment might be considered on the basis of known fishing areas. However, it should be remembered that the migratory species travel throughout the waters of the shelf, even though they may not be readily exploitable in some areas. Also some segments of the continental shelf are not now classed as known fishing areas simply because, for one reason or another, they have not yet been exploited. Hence no region of the shelf can be considered as completely devoid of biological significance. The possible introduction of radioactive wastes into the sea from land based operations will result, for the most part, in contamination of harbors, estuaries, and coastal waters. Hence it may be appropriate 17
to consider waters within an arbitrary twelve miles from the coastline in a different category from the waters of the outer continental shelf. It must be pointed out, however, that this outer continental shelf will very likely be utilized in the disposal of packaged waste material. Hence nuclear-powered ships are not the only potential source of radio- active material for these waters. Considerations relative to the open sea: Ocean areas more than 12 miles from shore and in which depths exceed 200 fathoms are here considered as open sea. In the open sea there are large areas which do not contribute materially to the commercial fisheries. There are, however, other large areas within which important oceanic fisheries operate, for example the Pacific tuna fishery. The open sea is now being utilized for the disposal of packaged waste material, though these wastes sink to the bottom and the possibility of any significant activity reaching the productive surface layers is slight. Under present doctrine regarding the containment of high level wastes on land, it appears that waste disposal from nuclear-powered ships will be the major source of radioactive wastes introduced into the surface layers of the open sea. Subdivision of the Marine Environment: On the basis of the above considerations the sea has been divided into six zones, which differ one from another either in terms of potential contribution to the food supply of a selected portion of the population, or in terms of importance as a potential receiver of wastes from sources other than nuclear-powered ships, or in terms of the restrictions placed on dispersal within the zone due to physical boundaries. These zones, together with the as- sumptions required for computation of the partial permissible concen- tration in seafood in each of the zones, resulting from the operation of nuclear-powered ships, are listed below: Zone 1. Harbors, estuaries, and inshore waters within 2 miles of the coastline. For this zone the assumption is made that a selected portion of the population receives all its protein requirement from sea- food harvested from these waters. It is further assumed that 30 per- cent of the maximum permissible dose which this population may re- ceive as a result of sea disposal may be allotted to waste disposal op- erations from nuclear ships in these waters. Zone 2. The coastal area, between 2 and 12 miles from the shore- line. For this zone the same assumptions are made as for Zone 1. This zone differs from Zone 1 in that the dispersion is less restricted by physical boundaries. Zone 3a. The outer continental shelf, beyond 12 miles from shoreline, having depths less than 200 fathoms, in known fishing areas. For this zone the assumption is made again that a selected portion of the population receives all its protein requirement from seafood har- vested in these waters. It is further assumed that three-fifths of the maximum permissible dose which this population may receive as a re- sult of sea disposal may be allotted to waste disposal operations from nuclear-powered ships in these waters. 18
Zone 3b. Those areas of the outer continental shelf which are not classified as known fisheries areas. For this zone the assumption is made that these areas contribute, either directly or indirectly through migratory fish, 20% of the protein requirement of a selected portion of the population. It is also assumed that three-fifths of the maximum permissible dose which this population may receive as a re- sult of sea disposal may be allotted to waste disposal operations from nuclear-powered ships in these waters. Zone 4a. The open sea, more than 12 miles from shore and hav- ing depths greater than 200 fathoms, in known fishing areas. For this zone the assumption is made that a selected portion of the population receives 50% of its protein requirement from seafood harvested in these waters, and that three-fourths of the maximum permissible dose which this population may receive as a result of sea disposal may be allotted to waste disposal operations from nuclear-powered ships in these waters. Zone 4b. Those areas of the open sea which are not classified as known fishing areas. For this zone the assumption is made that these areas contribute, either directly or indirectly through migratory fish, 10% of the protein requirement of a selected portion of the population, and that three-fourths of the maximum permissible dose which this population may receive as a result of sea disposal may be allotted to waste disposal operations from nuclear-powered ships in these waters. Computation of ppc Values for Seafood: A human population which obtained all its protein food from marine sources would eat about 1.5kg per week per person of fish or marine invertebrates. If this food is contaminated with a radioisotope, and if this is the only source of in- gestion of the isotope, we can calculate the maximum permissible con- centration in food corresponding to the maximum permissible concen- tration in drinking water by multiplying the latter by the ratio (water ingested per week) / (food ingested per week) = 2200 x 7 , . = 10 . 1500 Designate this factor as N^. Further, for each of the subdivisions of the marine environment, designate by Np that fraction of the protein requirement which a selected portion of the population receives from seafood harvested there; designate by N[> that fraction of the maximum permissible dose for this population which can be allotted to waste dis- posal into the sea, and by Ns that fraction of the allotment to the sea which may be utilized for nuclear-powered ships within the particular marine subdivision. Then the partial permissible concentration in sea- food which can result from the operation of nuclear-powered ships, for each of the subdivisions of the marine environment, is obtained by multiplying the maximum permissible concentration for drinking water for the general public by the factor Nm, which is given by 19