Highly radioactive waste

D. W. CleeUand, Proceedings of the Symposium on the Solidification and Eong-Term Storage of Highly Radioactive Wastes, USAEC, Richland, Wash., 1966. 

Historically, the Redox process was used to achieve the same purification as in the Purex process (97,129). The reagents were hexone (methyl isobutyl ketone) as the solvent, dichromate as an oxidant, and A1(N02)3 as the salting agent. The chief disadvantages of hexone are its flammability and its solubihty in water. However, because A1(N03)3 collects in the highly radioactive waste, thereby impeding the latter s further processing, the Redox process was abandoned in favor of the Purex process. 

Nuclear reactors, however, do generate highly radioactive waste. This waste, which consists primarily of the fission fragments and their radioactive-decay products, must be stored for many years before its radioactivity decays to a reasonable level, and the safe long-term storage of this waste is a matter of great concern and debate. Fortunately, the volume of waste that is created is only about 20 cubic meters annually from a reactor, compared with 200,000 cubic meters of waste ash from a coal-fired plant. When nuclear weapions were tested in the atmosphere, the radioactive products from the nuclear explosions were released into the air and fell to Earth as radioactive fallout. 

Congress has decided that reprocessing will not be practiced in this country so that we will not be in the plutonium production business. This seems like a safe thing to do since this action will minimize terrorism threats. Reprocessing generates chemi cal wastes but greatly reduces the volume of the highly radioactive waste. It also isolates plutonium and unused fuel for possible use as new fuel. 

Clark, W. E. Godbee, H. W. 1963. Fixation of simulated highly radioactive wastes in glassy solids. In Treatment and Storage of High Level Radioactive Wastes. IAEA, Vienna, 412-432. 

However, there are problems. The main problem associated with a nuclear power station is that the reactor produces highly radioactive waste materials. These waste materials are difficult to store and cannot be disposed of very easily. Also, leaks of radioactive material have occurred at various sites throughout the world. Accidents at a small number of nuclear power stations, such as Three Mile Island in the US (1979) and Chernobyl in the Ukraine (1986) have led to a great deal of concern about their safety. More recently, in March 2011 a major nuclear accident happened at the Fukushima nuclear power plant in northern Japan. On this occasion the accident was not caused as a result of the plant itself undergoing a problem, but as a result of an earthquake near Japan that gave rise to a tsunami. This damaged essential... 

By contrast, a nuclear plant of 1000-MWe capacity produces annually some 35 tonnes of highly radioactive spent fuel. If the spent fuel is reprocessed, the volume of highly radioactive waste will be about 3 m. The entire nuclear chain supporting this 1000-MWe plant, from mining through operation, will generate, in addition, some 200 m of intermediate-level waste and some 500 m of low level waste of year. 

The liquid level in the 300,000-gal tanks that contain highly radioactive waste is continuously monitored. A level indicator in each tank is set to alarm when the volume reaches 285,000 gal. This alarm sounds in both the control house and the main process building. A second leak detection system is a liquid-level indicator in the sump of the vault surrounding the tanks. 

Unlike burning fossil fuels, nuclear reactions do not produce pollutants such as carbon dioxide and acidic sulfur and nitrogen compounds. However, the nuclear reactions do form highly radioactive waste that is hard to dispose of safely. Other serious problems include the potential release of radioactive materials into the environment when fires or explosions take place, and also the limited supply of fissionable fuel and the higher cost of producing electricity using nuclear fuels rather than fossil fuels. Nuclear reactors that have experienced serious accidents are shown in Figure 21.13. 

Because of the danger, elaborate and expensive precautions must be taken to protect people who work with radioisotopes. Highly radioactive waste products that can take many thousands of years to decay must be stored carefully. Choosing storage sites is difficult, and so is transport of the wastes to the storage sites. Many people are concerned about nuclear processes as energy sources. The threat of nuclear war and concern over radioactive fallout have also caused some people to be reluctant to use any form of radioactivity. 

The curves indicate the fraction of the radioactivity present in the waste at the time of reprocessing that will be in solution if the glass block has come into contact with water 10, 65, or 300 years after reprocessing. An increase with time means that the leaching process is faster than the overall decay of radioactivity and vice versa. Thus, the curves represent the fraction of the initial radioactivity available for release into the environment at any time when the geologic barrier may fail. For comparison, the top curve of Fig. 11.9 shows the total fraction of the initial radioactivity available at any time. The plot thereby demonstrates that the solidification products presently envisaged for final disposal of highly radioactive waste may in fact provide an effective release barrier. 

Specific vitrification processes. An installation that has to serve a 5 MT/day reprocessing plant will have to have a capacity of about 150 liters/h, corresponding to a specific HLW volume of 600 liters/t of heavy metal and 80 percent load factor. As yet, none of the vitrification processes has been operated on this scale and with full radioactivity. In fact, there is only one process that is now demonstrated on a technical scale with highly radioactive waste and about 25 percent of full capacity, the French AVM process. The others are in different stages of development and still awaiting the hot demonstration phase. Consequently, design and operation data available are preliminary, and the following discussions of individual vitrification processes will not go deeply into the details but rather emphasize the principles of the processes. 

Hall, A. R., et al. Development and Radiation Stability of Glasses for Highly Radioactive Wastes, Proceedings of the Management of Radioactive Wastes from the Nuclear Fuel Cycle, vol. 2, International Atomic Energy Agency, Vienna, 1976, p. 3. 

Highly Radioactive Wastes by Incorporation into Glass, l.A.E.A. Panel Proc. Ser. ST1IPUBI18 1960, 375. 

Since that time the objects of the industry have changed from military to civil applications and three generations of plant have been constructed and operated. The United Kingdom reasonably can claim to have technical and industrial competence in all of the aspects of the nuclear fuel cycle, although the experience of the final disposition of highly radioactive waste is limited and affected necessarily more by social and political factors than by technology. 

Besides highly radioactive wastes of the core and blankets (spent core and blanket fuel subassemblies), medium and low level radioactive wastes are produced in... 

Kolarik E, Koch G, Kuesel HH, Fritsch J (1972) Separation of Americium and Curium from highly radioactive waste solution, KFK-1553, Karlsruhe Nuclear Research Center, Karlsruhe, Germany... 

Spent fuel from nuclear power stations contains radiogenic U and Pu, and highly radioactive waste solution is produced when the spent fuel is reprocessed. This waste solution needs to be disposed of as it remains highly radioactive for a very long period. 

A major consideration in the widespread use of nuclear fission power is the production of large quantities of highly radioactive waste products. These remain lethal for thousands of... 

Systems for the containment of highly radioactive waste in gaseous, vapour, liquid and/or solid form. 

AEC 180/13 (20 Sept. 1960), AEC/NRC A. R. Luedecke to James T. Ramey, 15 June 1959, General Correspondence (Waste Disposal), R. L. Kirk to James T. Ramey, 21 Mar. 1961 (Conunittee Members—Holifield, Chet), JCAE Papers Hewlett, "Federal Policy for the Disposal of Highly Radioactive Wastes," pp. 7-9 Defense High-Level Radioactive Waste Hanford Reservations, pp. 2-7 JCAE, "202" Hearings, 88th Cong., 1st sess., 1963, p. 650 Shapiro, Radwaste, pp. 50-51, 60-61. 

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