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2. REPORT ON DISPOSAL OF RADIOACTIVE WASTE ON LAND The Committee on Waste Disposal was set up at the request of the Atomic Energy Commission to study the possibilities of dispos- ing of radioactive waste materials on land and to indicate what re- search was needed to determine feasibility. In September 1955 a conference was held at Princeton which included representatives of AEC, members of the Department of Sanitary Engineering of Johns Hopkins, representatives of the U. S. Geological Survey, industry and many individual scientists compe- tent in relevant fields. Informed opinions were rendered at the con- ference on the questions asked by AEC so the present general report can be a brief summary of the main conclusions. The factual data resulting from the conference are included in this report as ap- pendices . As an outgrowth of the conferences (the preliminary ones at Johns Hopkins and the comprehensive one at Princeton) numerous reports have been made by individuals and committees dealing with the waste problem. In particular the summary by Drs. Hatch and Lieberman for the NAS-NRC "Study Group on Dispersal and Disposal of Radioactive Wastes" covers in adequate form much of what might have been included in a report of the present committee. The Conference and the subsequent studies of the Committee made it obvious that there is no specific answer to such a question as "How shall we dispose of radioactive waste?" On the other hand, given a specific geographic site and specific type of waste, a spe- cific answer as to feasibility and cost of waste disposal becomes pos- sible. It is then a chemical engineering, geological and economic investigation with definite parameters for which a definite answer or series of answers can be sought. The Committee has considered the complex and varied prob- lems of waste disposal on land and can express considered opinions on various of the problems and the research needed to deal with the problems. The Committee has in no sense done the research so that such expressions of opinion as are contained herein are predicated on the assumption that the research will be done before any final conclu- sion is reached on any type of waste disposal.
3. Unlike the disposal of any other type of waste, the hazard related to radioactive waste is so great that no element of doubt should be allowed to exist regarding safety. Stringent rules must be set up and a system of inspection and monitoring instituted. Safe disposal means that the waste shall not come in contact with any liv- ing thing. Considering half-lives of the isotopes in waste this means for 600 years if Cs and Sr are present or for about one-tenth as many years if these two isotopes are removed. The Committee has heard a number of descriptions of the waste disposal operations at Hanford and Oak Ridge and several com- mittee members have visited the Oak Ridge Installation. Some ques- tions exist at this time in the minds of most members concerning the long-term safety of waste disposal as practiced on these sites if con- tinued for the indefinite future. A great deal of work has been done at each of them by competent men, but it is not possible to say ex- actly what may happen to the waste and how its component elements may disperse. The above statements should in no sense be regarded as criticism of officials responsible for the operation of these instal- lations. They were constructed during the exigencies of a war so that plant location with respect to waste disposal could not be an over-riding consideration. They are in isolated localities far from population centers so that the hazard has been minimized in this re- spect, and in addition, continuing control is being maintained by the operators. The Committee is convinced that radioactive waste can be disposed of safely in a variety of ways and at a large number of sites in the United States. It may require several years of research and pilot testing before the first such disposal system can be put into operation. Until such time storage in tanks will be required for waste. The cost of safe waste disposal will probably be relatively high until a great deal of research has been done and experience gained. Transportation costs have to be added to over-all disposal costs. For this reason site selection for any chemical processing plant where large quantities of highly radioactive waste will be pro- duced, must be based on availability of a disposal area within eco- nomic transportation distance. Economic balance will exist between length of cooling time in tanks at the site of waste production vs. cost of transportation in shielded carriers -- the thickness of the shielding required being dependent on cooling time.
4. It will not be possible to dispose safely of large quantities of high-level waste in many large sections of the country. This cir- cumstance may dictate that it will not be economically feasible to place those types of power reactors or other nuclear facilities which produce liquid wastes in large quantity in such unfavorable sections of the country. We have on several occasions been asked such ques- tions as "Where can waste be disposed of within 25 miles of Tarry- town, New York?" The answer almost certainly is that waste cannot be disposed of safely anywhere near this site. We stress that the necessary geologic investigation of any proposed site must be com- pleted and the decision as to a safe disposal means established before authorization for construction is given. Unfortunately such an inves- tigation might take several years and cause embarrassing delays in the issuing of permits for construction. This situation can only be handled by starting investigation now of a large number of potential future sites as well as the complementary laboratory investigations of disposal methods. With the example of Tarrytown mentioned above it might be re- marked that the probability of finding a safe ultimate disposal means at the Savannah River plant appears equally gloomy. This only serves to emphasize the need for consideration of disposal before a site is chosen. A discussion of the various possibilities for waste disposal may be found in Appendices C and D, the Reports of the Committees for "deep" and "shallow" disposal, respectively. The most promising method of disposal of high level waste at the present time seems to be in salt deposits (see Appendix F by Heroy). The great advantage here is that no water can pass through salt. Fractures are self-sealing. Abandoned salt mines or cavities especially mined to hold waste are, in essence, long-enduring tanks. The possibility of making cavities in salt by pumping in water and removing brine is not favored (except for waste in solid form) unless the size and shape of such a cavity can be accurately controlled. The major element of potential risk in disposal in salt is that the cavity will collapse, structurally, in time. Salt is a weak material and will flow. Hence research is needed on size and shape of openings which can be relied upon to be structurally stable. The cavities should be at relatively shallow depth to avoid high confining pressures. Salt beds and mines are abundantly available along the south side of the Great Lakes from New York to Michigan and also in the form of salt domes along much of the Gulf Coast. Smaller salt deposits are
available at a number of other sites. The second most promising method seems to be in forming a silicate brick or slag which would hold all elements of the waste in virtually insoluble blocks. These could be stored in sheds on the surface in arid areas or in dry mines. Separation of the Cs and Sr isotopes from the waste and their storage in small packages or surface tanks would of course greatly simplify the general problem of waste disposal. Research on the feasibility of such separation should be pushed. Finally, disposal of waste in porous media such as sandstones at comparatively great depth may eventually be possible. Unlike oil, the waste would be denser than the normal saline water contained in such beds provided the heat generated by radioactive decay after emplacement is not sufficient to reverse the density relationship. Instead of concentrating in and being immobilized in tops of anticlines it would sink to floors of synclines. Deep synclines with closure would be preferred as disposal structures inasmuch as they would largely immobilize the waste if it was not allowed to become too hot. The great difficulty with this potential method is that the character of the waste fluid would have to be drastically changed to permit it to disperse in the porous medium without clogging the pore space.â Acid aluminum nitrate wastes would almost certainly form a gel-like substance if pumped into a sandstone. Extraction of the radioactive elements from the much larger bulk of aluminum nitrate appears at present to be a prohibitively expensive process. If processes were changed to produce waste without this unfavorable character deep disposal would become much more reasonable. The possibility that great dilution of aluminum nitrate waste fluid might alleviate pore space clogging should be investigated though it does not seem likely that the problem will be solved in this way. Folded rocks containing porous beds in which suitable structures could be located are widely distributed in the United States. The above remarks indicate the most promising avenues on which research should be pressed. Besides these, it is necessary to train a number of geologists in the attributes of the wastes and the possible solution of the problems of their disposal. Geological in- vestigation of a large number of potential sites for processing plants â Edwin Roedder (USGS) (1956) Disposal of high aluminum radioac- tive waste solutions by injection into aquifers.
6. or reactors producing liquid waste should be undertaken without delay. The question should not be phrased: "How can we dispose of waste at X site?" but should be: "Can or cannot waste be disposed of at X site?" The possibility of the negative answer should always be con- sidered. SPECIFIC RECOMMENDATIONS ON DISPOSAL 1. Storage in tanks is at present the safest and possibly the most economical method of containing waste. 2. Disposal in salt is the most promising method for the near future. Research should be pushed immediately on the structural problem of stability vs. size of cavities at a given depth; on the thermal problem - getting rid of the heat or keeping it down to ac- ceptable levels - and on the economics of such disposal. (Appendix F by Heroy) 3. Next most promising seems to be stabilization of the waste in a slag or ceramic material forming a relatively insoluble product. This could be placed in dry mines, surface sheds or large cavities in salt. 4. Disposal of waste in porous beds interstratified with im- permeable beds in a synclinal structure is a possibility for the more distant future. This is of particular interest for disposal of the large volumes of waste to be expected in the future. Very difficult and complex problems have to be solved before it will become feasi- ble. The reaction of the waste with connate waters or constituents of the rocks soluble in the waste solution will have to be studied. The composition of the rocks and the connate waters are both variable as will be the composition of the waste solutions so that an almost in- finite variety of circumstances result. In general acid aluminous waste would almost certainly tend to form precipitates which would clog pore spaces. The problem would have to be solved first for a given bed at a given site for a given waste solution at a given dilution. 5. The removal of Cs and Sr from the waste would make disposal somewhat easier for the waste free of these isotopes but does not change qualitatively the recommendations made in the report. 6. In the complex relations between (a) storage time of waste for cooling, (b) transportation cost in shielded carriers and (c) dis- tance to disposal site, the last of these factors must be considered
7. before location of any plant producing large quantities of waste, remembering that there are large sectors of the country where dis- posal is not possible. 7. Continuing disposal of certain /large volume/ locv level waste in the vadose water zone, above the water table, is of limited application and probably involves unacceptable long term risks. GENERAL. RECOMMENDATIONS ON COROLLARY PROBLEMS 1. The movement of gross quantities of fluids through porous media is reasonably well understood by hydrologists and geologists, but whether this is accomplished by forward movement of the whole fluid mass at low velocity or whether the transfer is accomplished by rapid flow in "ribbons", is not known. In deep disposal of waste in porous media it will in many cases be essential to know which of these conditions exists. This will be a difficult problem to solve. 2. The education of a considerable number of geologists and hydrologists in the characteristics of radioactive wastes and its disposal problems is going to be necessary.