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Packaged Wastes Packaged liquids and sludges in containers which can rupture and thus liberate their contents to the sea, and solid materials of density greater than sea water may also be safely disposed of in coastal waters if proper precautions are observed. The amount of activity which is dissolved in the sea water, or taken up by organisms, from such mate- rials is subject to the same limitations as for bulk liquid wastes. Precautions must be taken to guard against recovery by fishing or salvage operations, or transport to areas where the material could constitute a hazard. Disposal areas for such wastes should be in designated locations, and all disposal should be adequately recorded and controlled. THE PRESENT PROBLEM The basis for judgment. The request from the Atomic Energy Commission asks essentially for a differentiation between safe and unsafe procedures related to the dumping of radioactivity into coastal waters. The determination of where safe procedures end and unsafe pro- cedures begin involves an evaluation of information in two very different fields of science. The first'is radiation biology, a field that can supply information concerning tolerance limits for the quantities of radioactive materials that man can have either in his immediate environment or within himself, without regard for how it gets there. The second science field is oceanography, which can supply a description of the processes that can bring radioactive substances from a marine disposal area back to man. We emphasize here that the very nature of the primary information upon which our evaluation is based makes the division between safe and unsafe disposal procedures a rather broad region rather than a sharp dividing line. Because of this we have, with purpose, adopted a conser- vative attitude in our integration of the many pieces of information that make up our conclusions. Radioactive substances are a potential hazard to man, (1) because of radiation received from the immediate environment (external emit- ters), and (2) because of radiation received by substances taken into the body by ingestion, inhalation, or absorption through the skin (internal emitters). In both cases the potential hazards may do damage to the individual so as to reduce the life span, impair the functioning of parts of the body, etc., i.e. pathological damage, or to increase the mutation rate which will alter the inherited characteristics in future generations, i.e. genetic damage. 11
Our present state of knowledge with regard to th'e pathological effects of radiation is given in detail in NAS-NRC Publication 452 (7). A summary report of the National Academy of Sciences - National Research Council Committee on the Genetic Effects of Atomic Radiation was published in 1956 (8). The separation of safe from hazardous sea disposal procedures must be made, first of all, on the basis of potential hazard to man through his normal utilization of the sea, and secondly, on the possibility of injurious effect produced in the marine environment itself. Our assessment of the quantities and the rates of disposal of low level radioactive wastes into in-shore water that will create a potential hazard to man, through his uses of the sea and marine products, devel- oped from consideration of the natural processes occurring in the ma- rine environment that could bring the radioactive wastes back to man from suggested disposal sites. We have recognized two mechanisms that appear to be the most likely avenues through which this could occur. They are: (1) transport of the radioactive wastes from the disposal sites to the immediate shoreline, thereby creating a potential hazard in man's recreational uses of the coast, and (2) uptake of the radioactive waste components by one or more of the trophic levels in the marine biota with return to man in commercially important fish and shellfish. We would emphasize at this point that in all cases our separation of hazardous from non-hazardous procedures, so far as man's tolerance for radiation is concerned, is based upon the Handbook 52 values for maximum permissible amounts of radioisotopes in the total body and maximum permissible concentrations in water. The latter are for drinking water or for submersion in contaminated fluids. These values consider only pathological effects. No evaluation of possible genetic damage was attempted when Handbook 52 values were compiled. The conclusions in this report, then, may need revision if Handbook 52 max- imum permissible levels are drastically altered, or when some of the uncertainties introduced by lack of information in our evaluation of the oceanographic factors become better known. However, since Handbook 52 values are thought to be conservative and since our analysis of the oceanographic factors presents a conservative estimate of the behavior of the environment, as will be described below, we believe disposal practices based upon our recommendations have little likelihood of pro- ducing a hazard to man's present uses of the coastal waters. In the reports of quantities of radioactive substances already dis- posed of at sea one usually finds only the number of curies recorded. Only infrequently are the isotopes listed. Although this is unavoidable in many cases, a knowledge of the curie content of a disposal container only partially defines the potential hazard of the material. The extreme variability in the maximum permissible concentrations of various iso- topes in drinking water (3), for example, 2 x lO^and 8 x 10"7 nc/cc for tritium and strontium 90 respectively, emphasizes this point. 12
In the discussions which follow we will be concerned primarily with strontium 90. The hazard of other isotopes, relative to strontium 90, insofar as uptake by marine organisms and return to man in marine food products is concerned, will be given by the ratio of the permissible sea water concentration of an isotope to that of strontium 90. Table II lists the number of curies of each of a group of selected isotopes, equiv- alent to 250 curies of strontium 90, the latter value being the suggested maximum yearly rate of disposal of strontium 90 into any one disposal area. Also shown are the quantities of each of the isotopes that would decay to 250 equivalent curies following containment of one month and of one year. The significance of the quantities of isotopes relative to strontium- 90 is apparent when considering the practical problem of the disposal of packages containing a mixture of isotopes. Assume, for example, that packages containing waste of the following composition have been added TABLE II QUANTITIES OF SELECTED RADIOISOTOPES EQUIVALENT1 TO 250 CURIES OF STRONTIUM 90, SHOWING THE INITIAL QUANTITIES THAT WILL DECAY TO 250 EQUIVALENT CURIES ALLOWING ONE MONTH AND ONE YEAR CONTAIN- ME NT Isotope Curies no containment 1 mo. containment 1 yr. containment Na 24 5.0 x 107 1024 10183 P31 15.5 68.6 1.1 xlO9 S35 3.1 x 106 3.9 x 106 5.6 x 107 K42 3.1 x 106 1014 10226 Ca45 1.6x 105 l.SxlO5 7.5 x 105 Fe59 1.2 x 103 1.9x 103 3.3 x 10s Co 60 6.2 x 103 6.3 x 103 7.0 x 103 Cu 64 5.0 x 104 1021 1020l Zn65 1.4 x 104 1.5 x 104 3.8 x 104 Sr90 250 250 290 1 131 9.3 x 102 1.2 xlO4 10'* Cs 137 9.3 x 104 9.3 x 104 9.3 x 10* Equivalence based upon ratios of Permissible Sea Water Concentrations. 13
to a disposal area; 525 curies of Na-24; 1000 curies of Ca-45; 100 curies of Fe-59; 100 curies of Co-60; 120 curies of Sr-90; and 1000 curies of Cs-137. The total number of curies amounts to 2,845 well over the suggested yearly limit of 250 curies of Sr-90. Obviously, the relative hazard to man, considered in the route that might return the waste to him from the disposal area through marine food products, will be less for the mixture than for strontium-90. If the quantities of each of the isotopes above are multiplied by the ratio of the maximum per- missible sea water concentration of strontium-90 to that of the isotope, the sum of results assuming no containment is approximately 148 curies. This figure, which is a more realistic measure of the potential hazard of the waste than the 2,845 curies, includes the effect of MPC values for each isotope and the concentration factors from sea water to marine food products. Why dispose at sea? There are two ways of handling radioactive materials to prevent them from becoming a hazard to man. One is by containment, which has as its objective the retention of the material in such a manner that it does not get into the human environment, at least until natural radio- active decay has reduced the quantity of material to below permissible levels. The other is by dispersal, which has as its objective the dilu- tion of the waste to below permissible levels before it becomes a part of the immediate human environment. Within limits, procedures can be established so that disposal into coastal waters can take advantage of some of the desirable features of both methods of handling the wastes. The advantage of containment can be achieved by proper canister design. Presently used canisters are reclaimed 55 gallon steel drums which have an expected life, so far as corrosion by sea water is concerned, of approximately ten years (10). The factor of safety introduced by ten year containment is shown in Table III, in which the percents of the initial activity remaining after ten years and the maximum permissible concentrations for drinking water are listed for a group of isotopes including high yield, long-lived fission products and the isotopes that are shipped from Oak Ridge National Laboratories to licensed users. Two features of Table III should be emphasized. First, isotopes having long half life, that is, relatively large amounts remaining after ten years, and low MPC values are those that may produce the greatest potential hazard to man. Second, the MPC values are drinking water values and we are concerned here with sea water. Although not directly applicable to the present problem, these MPC values will be used later in modified form. The practice of mixing contaminated materials into concrete which is then cast into the steel drum, provides for containment 14
TABLE III PERCENTAGES OF INITIAL ACTIVITY REMAINING AFTER TEN YEAR CON- TAINMENT AND MAXIMUM PERMISSIBLE CONCENTRATIONS FOR DRINKING WATER, FOR SELECTED FISSION PRODUCT ELEMENTS AND ORNL ISOTOPES Percent after 10 ye an MPC (3) (uc/ml) Percent after 10 years MPC (3) (nc/ml) Isotope Isotope H3 57.5 0.2 Zn« 4.2 x 10-3 6 x 10-2 C" 99.9 3 x lO-3 Sr89 1o-18 7 x 10-5 No" 1o-1768 8 x 10-3 Sr90 75.8 8 x 10-7 P32 1o-" 2 x 10-4 Y91 io-1 7 0.2 S?S lO-8 5 x 10-3 Zr95 io-17 K42 1o-1998 1 x 10-2 Ru103 10-25 Co45 lO-5 5 x 10-4 Ru106 0.1 0.1 Cr51 io-39 0.5 ,131 ,0-lM 3 x 10-5 Fe55 9.3 Cs137 81 1.5 x 10* Fe59 10-22 4 x 10-3 Ce141 io-32 Co«0 26.5 2 x 10"2 Ce144 1.3x 10-2 4 x 10-2 Cu64 1o-2026 1 X 10-4 Pm147 &2 1 MPC for mixtures of isotopes of unknown composition is 1O"7 nc/ml. beyond the life of the steel drum. On the other hand, experiments de- signed to test the effect of hydrostatic pressure on disposal containers, indicated that voids in concrete may, at depths of a few hundred to a thousand meters, permit implosion of the steel drum and fracture of the concrete, thereby bringing about premature release of contaminant to the sea. The tests of canisters which have been performed have been con- cerned with disposal into at least 1000 fathoms of water where pressures in excess of 3000 pounds per square inch will be encountered, whereas we are concerned here with water depths up to approximately 30 fathoms where pressure less than 100 pounds per square inch will be encoun- tered. Although there is some doubt as to whether presently used con- tainers remain intact after disposal to the sea bottom, proper design and testing can provide the necessary information. 15
