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[en] Radioactive wastes may are generated throughout the life cycle of a nuclear power plant. These wastes can be categorized as follows: Operational wastes in the form of solids, liquids and gases. Plant components resulting from maintenance, modification or life extension work (e.g. steam generators, pumps, valves, control rods, spent filters, etc.). Materials from the structure of the plant and equipment (e.g. metals and concrete that result in large quantities of waste upon decommissioning Large quantities of materials will be generated during decommissioning and dismantling. A significant proportion of these materials will only be slightly contaminated with radioactivity. Due to economies of scale, recycling and reuse options are more likely to be cost effective for such large quantities of materials than for the relatively smaller quantities arising during operation. These materials also present opportunities to manage waste more effectively by utilizing the approaches to blending discussed in this paper. The NRC uses allows blending based on risk and performance measures for public health and safety. Performance-based regulation means that the blended waste must meet the limits on radiation exposures at the disposal facility and limits on how much the radioactivity concentration may vary or in other words, how homogeneous and well mixed it is. LLW blending is an approach to waste management that can give greater flexibility for disposal options for NPP waste from the entire life cycle of the plant which includes operational wastes such as ion exchange resins and filters, maintenance wastes which include replacement components (discrete items), and large quantities of decommissioning wastes
[en] The Waste Isolation Pilot Plant (WIPP), located approximately 42km (26miles) due east of Carlsbad, New Mexico U.S.A., is the first deep geologic repository certified in the United States (U.S.) to safely and permanently dispose of transuranic (TRU) radioactive waste generated from the research and production of nuclear weapons. March 2009 marked the 10 year anniversary of the first shipments of TRU waste to the WIPP by the U.S. Department of Energy (DOE). To date, 7,177 shipments of contact handled (CH) and remote handled (RH) waste have been received at WIPP. WIPP has disposed of over 100,000 waste containers for a total of nearly 58,600m3 of waste (58,502m3 CH and 84m3 RH). WIPP continues to be highly successful with 2008 being the safest year in WIPP history. WIPP received both the U.S.Transport Council award and the DOE Voluntary Protection Program Star of Excellence award in 2008. DOE submitted its Compliance Recertification Application for WIPP in March 2009 and renewal of its Hazardous Waste Facility Permit is due to the New Mexico Environment Department in May 2009. On located about 100 miles northwest of Las Vegas, Nevada, U.S.A.The license application was accepted for docketing by the U.S.Nuclear Regulatory Commission (NRC) on September 8, 2008, and the DOE is currently responding to NRC's Requests for Additional Information of which they have received over 200 requests, to date. However, the Yucca Mountain project will be scaled back to just those costs necessary to respond to NRC's RAIs, while the Administration develops a new approach to the long term management of nuclear waste in the U.S.
[en] The purpose of this paper is to review the updated NRC low level radioactive waste regulatory strategy and also present an update on a significant change in the LLW disposal landscape in the U.S., the opening of a new commercial disposal facility, the Texas Compact Waste Facility (CWF) in Andrews, Texas. Operational since spring of 2012, the CWF is owned and licensed by the state of Texas and operated by Waste Control Specialists LLC (WCS). The WCS facility in western Andrews County is the only commercial facility in the United States licensed to dispose of Class A, B and C LLW in the U.S. in the past 40 years. Based on the observation that other suitable sites have been identified such as the Clive, Utah site that meet (almost) all of these criteria it would appear that the first and last factors in our list are the most problematic and it will require a change in the public acceptance and the political posture of states to help solve the national issue of safe and cost-effective LLW disposal
[en] In the near future, many countries, including the Republic of Korea, will face a significant increase in low level radioactive waste (LLW) from nuclear power plant decommissioning. The purpose of this paper is to look at blending as a method for enhancing disposal options for low-level radioactive waste from the decommissioning of nuclear reactors. The 2007 U.S. Nuclear Regulatory Commission strategic assessment of the status of the U.S. LLW program identified the need to move to a risk-informed and performance-based regulatory approach for managing LLW. The strategic assessment identified blending waste of varying radionuclide concentrations as a potential means of enhancing options for LLW disposal. The NRC's position is that concentration averaging or blending can be performed in a way that does not diminish the overall safety of LLW disposal. The revised regulatory requirements for blending LLW are presented in the revised NRC Branch Technical Position for Concentration Averaging and Encapsulation (CA BTP 2015). The changes to the CA BTP that are the most significant for NPP operation, maintenance and decommissioning are reviewed in this paper and a potential application is identified for decommissioning waste in Korea. By far the largest volume of LLW from NPPs will come from decommissioning rather than operation. The large volumes in decommissioning present an opportunity for significant gains in disposal efficiency from blending and concentration averaging. The application of concentration averaging waste from a reactor bio-shield is also presented
[en] The purpose of this paper is to evaluate several leading options for the management of radioactive metallic waste against a set of general criteria including safety, cost effectiveness, radiological dose to workers and volume reduction. Several options for managing metallic waste generated from decommissioning are evaluated in this paper. These options include free release, controlled reuse, and direct disposal of radioactive metallic waste. Each of these options may involve treatment of the metal waste for volume reduction by physical cutting or melting. A multi-criteria decision analysis was performed using the Analytic Hierarchy Process (AHP) to rank the options. Melting radioactive metallic waste to produce metal ingots with controlled reuse or free release is found to be the most effective option
[en] Highlights: •The management strategy of the metallic waste from the decommissioning of Kori Unit 1 is proposed. •The operational concept and the melting technology principle were established. •Dose calculation was done and the highest dose was observed in the slag worker. -- Abstract: The oldest commercial reactor in South Korea, Kori Unit 1 Nuclear Power Plant (NPP), will be permanently shut down starting in 2017. Since decommissioning of NPPs will generate a huge amount of radioactive metallic waste, proper treatment for decommissioning wastes is one of the key factors to decommission a plant successfully. Many studies have been conducted and experience accumulated for waste minimization and the reduction of disposal volume. Melting technology is one of the proven technologies for effectively managing the metallic waste and has been adopted by many countries. However, a licensed melting facility to dispose of metallic wastes from the NPP decommissioning has not been implemented in Korea. The purpose of this study is to establish a management plan for metallic waste and to evaluate the preliminary doses according to the acceptance criteria and operations at the facility. Based on the available research papers and empirical data from domestic and international experience, the operational concept and the melting technology principle were established and its dose and volume reduction effects were evaluated. The concept of operating a melting plant is to finally free release the ingots after melting or free release after a planned storage period. Based on this concept, the radioactive concentration of the scrap metal which can be treated was derived, demonstrating that melting can be applied to low level and very low level wastes above the clearance level. The RESRAD-RECYCLE computer code was used to assess worker doses and was rated within the regulatory limits in most scenarios, except for slag workers. Factors affecting the dose, such as methods of radiation protection, operating method and working time, will be important factors in establishing the melting facility and the radiological limits should also be determined accordingly.
[en] Since the first description of carbon dioxide (CO2) angiography the indications for using CO2 have been changing and the applications of CO2 angiography evolving. This review covers the contemporary role of CO2 angiography. CO2 angiography can be considered according to whether it is likely to be better, equivalent to or worse than conventional iodinated contrast medium (ICM). Areas where CO2 angiography offers distinct advantages over ICM will be emphasized. The limitations to using CO2 and specific caveats will be discussed. The basic physical properties of CO2 and avoidance of the complications of gas angiography will be considered. CO2 gas is cheap, non-allergenic, and is not nephrotoxic. Unfortunately it is not a panacea, angiographic quality is reduced, it is not tolerated by every patient, and it cannot be used in every location. It is important to be pragmatic and to use conventional contrast or alternative imaging rather than struggling with suboptimal CO2 angiography
[en] Tajikistan has a number of uranium ore deposits and mining and milling facilities, which operated in the past. This country's own ores and imported raw materials were processed mainly at the former Leninabad Geochemical Combine facility (currently State Enterprise (SE) 'Vostokredmet') and also at other hydro-metallurgical plants located in the vicinity of uranium ore extraction sites (Adrasman, Taboshar, Isphara, etc.). Presently the only operating enterprise in the Republic of Tajikistan, which still has the potential to process uranium ores using an acid leach extraction process, is State Enterprise 'Vostokredmet'. There are also 10 sites where uranium residues and waste rock piles are disposed which belongs to the current enterprise. One of the most popular decisions is to make cover system for tailings by using as natural as engineer barriers which can provide long term sustain operation and performance. Then HELP (Hydrologic Evaluation of Landfill Performance) program, will be used to designing, evaluate and optimize cover system
[en] Large amounts of concrete waste are likely to arise from the decommissioning of a Kori-1 nuclear power plant. Several studies have been conducted on decommissioning concrete waste in recent decades, however, they have been limited to contaminated concrete issues or were small pilot-scale experiments. This study constructed two industrial-scale models of on-site concrete waste management for clean as well as contaminated concrete. To evaluate the performance of both the models, simulations were conducted using the Flexsim software. The concrete particle size distribution of Kori-1 and concrete processor properties based on widely used construction equipment were used as sources of input data for the simulations. It was observed that it may take over two years to complete the on-site concrete management processes owing to the performance of existing processors. In addition, it was demonstrated that it is essential to identify bottlenecks in the system and enhance the performance of the relevant processors to avoid delays of the decommissioning schedule. Our results suggest that this novel approach can contribute to developing schedules or expediting delayed activities in the Kori-1 decommissioning project
[en] In this study, we observe the effects on the dose results when the ingestion rate is modified at maximum and when the respiratory mask used in the general industry is applied. RESRAD-RECYCLE, a dose assessment for radioactive contaminated materials, was useful in identifying the results from changes in parameters affecting internal exposures. The ingestion rate and the respiratory protection factor were found to be influential factors on ingestion dose, and the change of ingestion rate had a great effect. In the case of inhalation dose, there was no causal relationship with the ingestion rate, and dose was significantly reduced by applying respiratory protection factor. However, it was also seen that the inhalation dose is not large compared to the ingestion. The results of this study can be used as useful data for the workers’ radiation protection measures in recycling of the radioactive contaminated metallic waste.