[What to do about radioactive waste?].
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During 1985, low-level radioactive waste disposal has become a critical concern. The issue has been forced by the threatened closure of the three commercial disposal sites. The medical community has used radioactive isotopes for decades in nuclear medicine, radiation therapy, radioimmunoassay, and biomedical research. Loss of disposal capacity for radioactive wastes generated by these activities, by the suppliers of radioisotopes, and by pharmaceutical companies will have a profound impact on the medical profession.
The University of Texas Medical Branch (UTMB) at Galveston is a large academic medical center with about 12,700 employees, 350 radioisotope research labs and 200 permitted radioactive materials users. Consequently, UTMB generates a fairly large amount of radioactive waste. The majority of this waste contains short-lived radionuclides, such as 32P, 33P, and 35S, which are held for decay and then disposed at a sanitary landfill. However, some waste, including long-lived waste and stock vials, is compacted into drums and stored in a warehouse facility, on-site, until disposal at a low-level radioactive waste (LLRW) facility. Space in the warehouse is limited but disposal is currently cost prohibitive. A reevaluation of our program was conducted to see if volumes of LLRW requiring disposal at a commercial LLRW facility could be reduced. A reevaluation of the waste streams resulted in the shifting of most of the material that was being drummed for shipment to a LLRW facility to disposal by landfill or incineration. Materials that were previously assumed to be radioactive are now being evaluated prior to disposal to determine if they may be disposed of as non-radioactive waste. Following the initial evaluation, the amount of compacted dry solids assumed to contain long-lived radionuclides was reduced. The space that was saved due to the decrease in drumming for disposal is now used to hold the increased volume of decay-in-storage material. The monetary savings will amount to about $45,000 per year. This program is currently being expanded to reduce other waste streams at the university.
There is a need to provide realistic estimates of the activity discharged to the drains by patients undergoing procedures involving unsealed radionuclides. These estimates are essential for record keeping purposes, to demonstrate compliance with limits set in waste disposal authorizations and for planning new installations. In this study, we report the discharge of activity for 174 patients (202 treatments) undergoing treatment of thyroid carcinoma with radioactive iodine. We have found that approximately 55% of administered activity is excreted in the first 24 h and that 85% of administered activity is discharged to the sewer over a typical inpatient stay of 5 days. There was no significant difference in levels of discharge between those patients undergoing inaugural ablation therapy and those having further treatments with radioactive iodine.
Polonium-210 concentrations were determined for soil, vegetation and small mammal tissues collected at a solid radioactive waste disposal area, near a phosphate ore processing plant and at two rural areas in southeastern Idaho. Polonium concentrations in media sampled near the radioactive waste disposal facility were equal to or less than values from rural area samples, indicating that disposal of solid radioactive waste at the Idaho National Engineering Laboratory Site has not resulted in increased environmental levels of polonium. Concentrations of 210Po in soils, deer mice hide and carcass samples collected near the phosphate processing plant were statistically (P less than or equal to 0.05) greater than the other sampling locations; however, the mean 210Po concentration in soils and small mammal tissues from sampling areas near the phosphate plant were only four and three times greater, respectively, than control values. No statistical (P greater than 0.05) difference was observed for 210Po concentrations in vegetation among any of the sampling locations.
This paper reviews progresses on the use of alkali-activated cements for stabilization/solidification of hazardous and radioactive wastes. Alkali-activated cements consist of an alkaline activator and cementing components, such as blast furnace slag, coal fly ash, phosphorus slag, steel slag, metakaolin, etc., or a combination of two or more of them. Properly designed alkali-activated cements can exhibit both higher early and later strengths than conventional portland cement. The main hydration product of alkali-activated cements is calcium silicate hydrate (CSH) with low Ca/Si ratios or aluminosilicate gel at room temperature; CSH, tobmorite, xonotlite and/or zeolites under hydrothermal condition, no metastable crystalline compounds such as Ca(OH)(2) and calcium sulphoaluminates exist. Alkali-activated cements also exhibit excellent resistance to corrosive environments. The leachability of contaminants from alkali-activated cement stabilized hazardous and radioactive wastes is lower than that from hardened portland cement stabilized wastes. From all these aspects, it is concluded that alkali-activated cements are better matrix for solidification/stabilization of hazardous and radioactive wastes than Portland cement.
Deregulation, with concurrent pressure on electricity utilities, has fundamentally changed the once-"closed" radioactive waste management system controlled by the so-called "nuclear establishment." Advocacy coalitions may change-who knows in which direction-but policy learning may also take place. This article presents a framework to evaluate the management options for a specified concept of "sustainability." When weighing the different objectives in view of the long-lasting potential danger of radiotoxic substances, the overall goal of a sound waste management system is to demonstrate safety. The first-priority objective of a disposal system, therefore, is its stability so that it can comply with the protection goal, that is, the long-term protection of humans and the environment from ionizing radiation. The complementary objective is flexibility, defined here as intervention potential. Because trade-offs within the "sustainability triangle" of ecology, economy, and society are unavoidable, the concept of "integral robustness"-both technical and societal-is introduced into radioactive waste management. A system is robust if it is not sensitive to significant parameter changes. In the present case, it has to have a conservative, passively stable design with built-in control and intervention mechanisms. With regard to technical implementation, a concept called "monitored long-term geological disposal" is presented. Such an "extended" final disposal concept emphasizes technical robustness, recognizes evaluation demands (for a potential break-off of a project), and enhances process-based transparency. This open approach admittedly sets high challenges with regard to technicalities as well as the institutional setting and the management process. It requires "mutual learning" by and from all stakeholders to achieve a truly sustainable radioactive waste management system.
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It is well known that very large storage tanks for radioactive liquids are necessary for the disposal of liquid radioactive waste. In vitro tests in radioimmunoassay in nuclear medicine are rapidly increasing for clinical examination causing marked increase in the volume of liquid radioactive waste. Thus we have developed a system for decontaminating radioactivity from liquid waste. In the first step, the liquid waste is boiled by a sterilizer and, in the second step, this sterilised liquid is filtered by a cylindrical filter (Toyo filter No. 84). After filtration, the liquid waste is passed into a beaded charcoal column and an ion exchange resin (Amberlite IRA 402) column. After these treatments, the radioactivity level of liquid waste is lowered to less than 1% of the original radioactivity. We are now in the planning stages of building an apparatus for practical use.
The radioactive waste incineration plant at Tokai Research Establishment, JAERI, was installed in 1966 and has been operated routinely. The exhaust-gas system of the incinerator consists of spray scrubber, electrostatic precipitator, cloth filter, HEPA filter and so on. This experimental program was carried out to examine the behavior of tritium water to various parts of the incineration plant when combustible waste contaminated with tritium water was incinerated. The experiment results were as follows. The collective rate of tritium water in each dust collector was 85% in the spray scrubber, and 6% as condensation water in electrostatic precipitator, gas cooler and HEPA filter. Further the release rate of tritium water from stack was 9%.
The physicochemical conditions, composition of microbial communities, and the rates of anaerobic processes in the deep sandy horizons used as a repository for liquid radioactive wastes (LRW) at the Siberian Chemical Combine (Seversk, Tomsk oblast), were studied. Formation waters from the observation wells drilled into the production horizons of the radioactive waste disposal site were found to be inhabited by microorganisms of different physiological groups, including aerobic organotrophs, anaerobic fermentative, denitrifying, sulfate-reducing, and methanogenic bacteria. The density of microbial population, as determined by cultural methods, was low and usually did not exceed 10(4) cells/ml. Enrichment cultures of microorganisms producing gases (hydrogen, methane, carbon dioxide, and hydrogen sulfide) and capable of participation in the precipitation of metal sulfides were obtained from the waters of production horizons. The contemporary processes of sulfate reduction and methanogenesis were assayed; the rates of these terminal processes of organic matter destruction were found to be low. The denitrifying bacteria from the underground repository were capable of reducing the nitrates contained in the wastes, provided sources of energy and biogenic elements were available. Biosorption of radionuclides by the biomass of aerobic bacteria isolated from groundwater was demonstrated. The results obtained give us insight into the functional structure of the microbial community inhabiting the waters of repository production horizons. This study indicates that the numbers and activity of microbial cells are low both inside and outside the zone of radioactive waste dispersion, in spite of the long period of waste discharge.
During the process of negotiation of the Convention on Nuclear Safety it was recognised that the safe management of radioactive waste was also a subject of great international concern. It was not possible to cover this subject comprehensively in a Convention focusing on the safety of civil nuclear power plants but the need for a further Convention was identified in the preamble to the Convention on Nuclear Safety. Accordingly the procedures were started that led to the setting-up of an open-ended Group of Experts to agree the text of a new Convention. This article describes from a scientific and technical viewpoint the deliberations of the Group of Experts, the compromises needed to cover in a single Convention the safety of both spent fuel management and radioactive waste management, the last minute expansion of the scope to admit reprocessing, the delicate negotiations on the inclusion of material from military programmes and the contentious question of the transboundary movement of spent fuel and radioactive waste. The article also summarises and provides some commentary on the final provisions of the Convention as adopted by a Diplomatic Conference in Vienna in September 1997 and now open for signature.
(79) Waste, by definition, has no benefit. It should be viewed as one aspect of the beneficial practice that gave rise to it. Furthermore, radioactive waste management should be placed in the context of the management of society's waste in general. (80) A major issue in evaluating the acceptability of a disposal system for long-lived solid radioactive waste is that doses or risks may arise from exposures in the distant future. There is uncertainty surrounding any estimate of these doses or risks due to lack of knowledge about future conditions. Such exposures are treated as potential exposures as their magnitude depends on future processes and conditions that have probabilities associated with them. (81) Nevertheless, the Commission recognises a basic principle that individuals and populations in the future should be afforded at least the same level of protection from the action of disposing of radioactive waste today as is the current generation. This implies use of the current quantitative dose and risk criteria derived from considering associated health detriment. Therefore, protection of future generations should be achieved by applying these dose or risk criteria to the estimated future doses or risks in appropriately defined critical groups. These estimates should not be regarded as measures of health detriment beyond times of around several hundreds of years into the future. In the case of these longer time periods, they represent indicators of the protection afforded by the disposal system. (82 Constrained optimisation is the central approach to evaluating the radiological acceptability of a waste disposal system; dose or risk constraints are used rather than dose or risk limits. By this transition from limitation to optimisation, the needs of practical application of the radiological protection system to the disposal of long-lived solid waste disposal are met: determination of acceptability now for exposures that may occur in the distant future. Optimisation should be applied in an iterative manner during the disposal system development process and should particularly cover both site selection and repository design. (83) Two broad categories of exposure situations should be considered: natural processes and human intrusion. The latter only refers to intrusion that is inadvertent. The radiological implications of deliberate intrusion into a repository are the responsibility of the intruder. Assessed doses or risks arising from natural processes should be compared with a dose constraint of 0.3 mSv per year or its risk equivalent of around 10(-5) per year. With regard to human intrusion, the consequences from one or more plausible stylized scenarios should be considered in order to evaluate the resilience of the repository to such events. (84) The Commission considers that in circumstances where human intrusion could lead to doses to those living around the site sufficiently high that intervention on current criteria would almost always be justified, reasonable efforts should be made at the repository development stage to reduce the probability of human intrusion or to limit its consequences. In this respect, the Commission has previously advised that an existing annual dose of around 10 mSv per year may be used as a generic reference level below which intervention is not likely to be justifiable. Conversely, an existing annual dose of around 100 mSv per year may be used as a generic reference level above which intervention should be considered almost always justifiable. Similar considerations apply in situations where the thresholds for deterministic effects in relevant organs are exceeded. (85) Compliance with the constraints can be assessed by utilising either an aggregated risk-oriented approach, with a risk constraint, or a disaggregated dose/probability approach, with a dose constraint, or a combination of both. A similar level of protection can be achieved by any of these approaches; however, more information may
In several countries, low-level radioactive wastes are treated and stored awaiting construction and operation of a final repository. In some cases, interim storage may be extended for decades requiring special attention regarding security issues. The International Atomic Energy Agency (IAEA) recommends segregation of wastes that may be exempted from interim storage or ultimate disposal. The paper presents a method to optimize the decision making process regarding exemption vs. interim storage or ultimate disposal of these wastes.
Interactions between element chemistry and the ambient geochemistry play a significant role in the control of radionuclide migration in the geosphere. These same interactions influence radionuclide release from near surface, low level radioactive waste, disposal sites once physical containment has degraded. In situations where LLW contains significant amounts of metal and organic materials such as cellulose, microbial degradation in conjunction with corrosion can significantly perturb the ambient geochemistry. These processes typically produce a transition from oxidising to reducing conditions and can influence radionuclide migration through changes in both the dominant radionuclide species and mineral phases. The DRINK (DRIgg Near field Kinetic) code is a biogeochemical transport code designed to simulate the long term evolution of the UK low level radioactive waste disposal site at Drigg. Drigg is the UK's principal solid low level radioactive waste disposal site and has been receiving waste since 1959. The interaction between microbial activity, the ambient geochemistry and radionuclide chemistry is central to the DRINK approach with the development of the ambient pH, redox potential and bulk geochemistry being directly influenced by microbial activity. This paper describes the microbial aspects of the code, site data underpinning the microbial model, the microbiology/chemistry interface and provides an example of the code in action.
The disposal of low-level radioactive waste (LLRW) entails financial and safety risks not common to most market commodities. This manifests debilitating uncertainty regarding future waste volume and disposal technology performance in the market for waste disposal services. Dealing with the publicly perceived risks of LLRW disposal increases the total cost of the technology by an order of magnitude, relative to traditional shallow land burial. Therefore, this analysis first examines five proposed disposal facility designs and quantifies the costs associated with these two important sources of uncertainty. Based upon this analysis, a marketable disposal permit mechanism is proposed and analyzed for the purpose of reducing market uncertainty and thereby facilitating a market solution to the waste disposal problem. In addition to quantifying the costs, the results illustrate the ways in which the design of a technology is influenced by its institutional environment, and vice versa.
The authors present experience accumulated by "RADON" Industrial Research Association in treating liquid radioactive waste. According to the presentation, activities of "R ADON" Industrial Research Association develop in three directions--evolving technical means to purify radioactive waters in "RADON" Industrial Research Association, advancing mobile plants to purify radioactive waters in other institutions, elaborating new technologies for liquid radioactive waste purifications within numerous national and international projects and agreements with various organizations (including those associated with nuclear power stations and nuclear submarines).
This paper describes a software package for a personal computer which deals with storage records of radioactive wastes; the software keeps the records of purchase and use of radioisotopes and makes the inventory records of radioactive wastes. The records for the cargo booking of the wastes for the Japanese Radioisotope Association can be prepared by this software package.