Safety implication for an unsaturated zone nuclear waste repository

In this paper we shed some light on the safety of unsaturated zone nuclear geological repositories in the long run by examining the effect of physical and chemical processes that take place inside a partially failed nuclear waste container. Our analysis addresses the safety of the proposed nuclear repository at Yucca Mountain, which is intended to store high-level nuclear waste. Our study is independent of the US Department of Energy (DOE) analysis, which involves a number of complex computer codes and assumptions, and relies on the performance of an engineered barrier system. Our safety analysis could be applied in general to any geological repository designed to be in an unsaturated zone, since it is based on the geology, unsaturated zone location, and a key characteristic of the waste, heat production. This analysis shows that the radionuclide release from a partially failed waste container, stored in an unsaturated zone geological repository, is likely to be gradual and long delayed.     

Nuclear waste repository siting: An alternative approach

Under the Nuclear Waste Policy Act of 1982, the US Department of Energy has initiated a highly centralized siting process for two high-level nuclear waste repositories. Concomitantly, the Low Level Radioactive Waste Policy Act of 1980 requires states to create regional compacts for low-level nuclear waste disposal. This paper evaluates these and other federal nuclear waste facility siting proposals from constitutional choice and social equity perspectives. A satisficing site selection model is proposed which could resolve the likely geopolitical impasses in US federal nuclear waste management.     

HEAT TRANSFER ANALYSIS OF NUCLEAR WASTE CASKS STORED IN THE YUCCA MOUNTAIN REPOSITORY

ABSTRACT

A numerical model of the residual heat associated with stored nuclear waste casks proposed for long-term storage in Yucca Mountain has been developed. The Yucca Mountain Repository, located about 100 miles from Las Vegas, NV, is the proposed long-term geologic repository for high-level nuclear waste. STAR-CD, one of several commercial computational fluid dynamics packages being used for the assessment studies, was used to establish the numerical model. The model was developed to simulate the fluid flow and heat transfer within the drift tunnels generated by the waste casks over a 10,000-year time cycle. The model shows that the heat generated from within the casks is partially removed by ventilating air moving through the drifts and conduction through the drift walls. Thermal radiation was found to have little effect on overall cooling compared to the roles of natural convection adjacent to the casks and forced convection from the drift ventilation.     

Toward a viable nuclear waste disposal program

The essay deals with the lack of a suitable permanent storage site for the radioactive waste that has been produced by more than 103 open-cycle nuclear reactors in the U.S. The DOE has recently withdrawn the licensing application for the Yucca Mountain Repository leaving the nuclear industry responsible for the safety of more than 800 waste-containing concrete casks currently on the open surface at 34 sites. It also has not undertaken measures to reduce the volume of additional waste produced by both existing and newly planned reactors. The DOE has instead opted to undertake research to develop new cycles that "burn" the radioactive waste. This policy appears subordinated to obvious political pressures. It is short sighted in terms of a practical program to serve the interests of the clean and safe energy requirements of the country. The essay also describes technical initiatives and processes that are recommended for a better solution.     

Finessing the fuel: Revisiting the challenge of radioactive waste disposal

It is pointed out that the apparent decision of the United States to end development of the Yucca Flat, Nevada repository for permanent disposal of radioactive waste may inadvertently place it at variance with the disposal principles of the International Atomic Energy Agency (IAEA) which caution nuclear nations that “The burden on future generations shall be minimized by safely disposing of high level radioactive wastes at an appropriate time, technical, social and economic factors being taken into account.” It is then shown that the IAEA's ten technical criteria for underground disposal can seemingly be met by storing vitrified waste a kilometer underground in the crystalline basement rock of a mid-continent shield, where: (a) it should be invulnerable to redistribution by incompetence, natural disaster, or terrorism and (b) there is no obvious pathway for leakage into the biosphere. Finally, a method is proposed by which the storage impasse may be broken.     

Implications of the new National Energy Basic Plan for nuclear waste management in Korea

The Korean National Energy Committee has recently adopted a new National Energy Basic Plan according to which the electricity generated by nuclear power plants is to increase from the current 35.5% of total electricity production to 59% by 2030. This large increase in nuclear power will inevitably accelerate the accumulation of spent fuel; if the direct disposal option is pursued, spent fuel arisings in Korea are expected to exceed 100,000 tHM in 2100. It is estimated that the country will require between 10–22 disposal sites, each with an area equal to the Gyeongju low- and intermediate-level radioactive waste (LILW) disposal site, to accommodate this amount of spent fuel. However, considering Korea's geographic profile, securing this number of sites will be almost impossible, and will ultimately create a serious problem for the sustainability of nuclear energy in the country. In view of this dilemma, this paper recommends that the volume of Korean nuclear waste for disposal be significantly reduced, and offers sodium fast reactor (SFR)-based recycling as a potentially viable solution.     

Three-dimensional thermal analysis of the repository for high-level radioactive nuclear waste

One of the key issues of the dimensioning design and safety assessment of the repository for deposing the high-level radioactive nuclear waste is the temperature distribution. A three-dimensional layered model was established for analyzing the heat conduction near single waste canister. Applying the Laplace transform and finite Fourier Sine transform upon the governing equations of heat conduction, the solutions in the Laplace domain were obtained. The solutions in the Laplace domain were numerically inverted into semi-analytical solutions in the time domain by the Crump method, and the temperature distribution was obtained near the canister at the center of one disposal panel. The initially estimated value of the canister spacing was determined according to the temperature distribution and design criterion. Finally, the obtained temperature distribution was used to investigate the influence of relevant parameters on the canister surface temperature. The results show that the present model is reliable by comparing with the existing analytical model. The peak canister surface temperature is significantly affected by the tunnel spacing, canister spacing, thickness of buffer layer, and thermal conductivities of buffer material and surrounding rock.     

Study of an incrementally loaded multistage flash desalination system for optimum use of sensible waste heat from nuclear power plant

Existing practice of nuclear desalination cogeneration incurs loss of nuclear plant power generation because it competes for live steam with nuclear plant steam turbine. Such loss is completely avoided with the nuclear desalination plant design proposed in the present study. The plant called GTHTR300 is based on a high‐temperature gas reactor rated at 600 MWt. Gas turbine is used to replace steam turbine as power generator. The gas turbine converts about a half of the reactor's thermal power to electricity while rejecting the balance as sensible waste heat to be utilized in a multistage flash (MSF) plant for seawater desalination. A new MSF process scheme is proposed and optimized to efficiently match the sensible waste heat source. The new scheme increments the thermal load of the multistage heat recovery section in a number of steps as opposed to keeping it constant in the traditional MSF process. As the number of steps increases, more waste heat is utilized, and top brine temperature for peak water production is increased. Both tend to increase water yield. Operating with a similar number of stages, the new process is shown to produce 45% more water than the traditional process operating over the same temperature range. As a result, the GTHTR300 yields 56,000 m³/d water and generates 280 MWe power at constant efficiency with and without water cogeneration. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis of possible geological storage of CO2 and nuclear waste in Lithuania

Lithuania is currently dealing with two major problems in energy sector: final closure of Ignalina Nuclear Power plant (Ignalina NPP) in the end of 2009 and nuclear waste disposal and climate change mitigation issues having in mind replacement of nuclear capacities with fossil one and anticipated increase in GHG emissions. Lithuania has two options: to construct new nuclear power plant also taking into account nuclear waste disposal issue or to burn fossil fuel and to apply carbon capture and storage (CCS) for GHG emission reduction. These two options need to be investigated in Lithuania based on various studies conducted in Lithuania and abroad dealing with geological carbon storage and nuclear waste disposal potentials. There are no long-lived nuclear waste geological storage capacities in Lithuania and there is no pilot project on CCS developed in Lithuania. The aim of the article is to analyse and compare geological carbon and nuclear waste storage opportunities in Lithuania and to assess nuclear and carbon capture and storage technologies in terms of costs.     

Scientific basis for corrosion of copper in water and implications for canister lifetimes

Abstract

The Swedish Nuclear Fuel and Waste Management Company has developed a method for safely disposing spent nuclear fuel, which involves encapsulation of the waste in copper canisters and burying it deep in the stable crystalline rock of the Fenno-Scandian shield. The design life of the canisters in the so called KBS-3 design is in excess of 100?000 years. These long canister lifetimes are a consequence of a number of factors involving the properties of the material and the nature of the near field environment in the KBS-3 repository. One of these factors, namely the thermodynamic stability of copper in O₂ free water in the absence of sulphide, has been questioned. This paper critically reviews the evidence for and against the claim that water oxidises copper, and discusses the implications for canister lifetimes even if the proposed mechanism is correct. Even though the evidence presented in support of the proposed mechanism is not compelling, the Swedish Nuclear Fuel and Waste Management Company is actively engaged in ongoing research and development on the topic.     

Introducing OTEC to mainland utilities

The adoption of advanced technology by a large electric utility must be preceded by a lengthy assessment process involving cost, performance, reliability, technology availability, environmental impact, legal, institutional, and other factors. Over the past 25 years, the most important technological development to take place in the electric utility business has been that of nuclear power generation. This technology, though proven technically, has encountered significant problems. The time to site and construct a nuclear plant has grown because of environmental and regulatory restrictions. The absence of a national policy with respect to nuclear waste disposal and fuel recycling has created what appears to utility planners to be a very unfavorable political environment. For these and other reasons, the capital cost of nuclear plants has been steadily increasing and utility managements have begun to look to other fuel technologies such as coal.In this paper, we examine the major factors which a large utility considers in evaluating any potentially important new energy system. Briefly, we review U.S. electric utility experience with technological innovation and identify the major problem areas facing industry from one utility's point of view. We then discuss the feasibility and appeal of ocean thermal energy conversion (OTEC) technology and describe the steps which one utility executes in determining the need for new capacity and the planning process which results in the construction and operation of a new plant. These steps are then applied to OTEC.Tentatively, we have concluded that the current U.S. Government OTEC program leaves OTEC an unlikely candidate for meaningful U.S. mainland applications within the century. We recommend a specific development strategy which will produce performance and cost data needed by potential investors in, and by operators of, electric utilities.     

Comparison of carbon dioxide and nuclear waste storage costs in Lithuania

Nuclear power and carbon capture and storage (CCS) are key greenhouse gas mitigation options under consideration across the world. Both technologies imply long-term waste management challenge. Geological storage of carbon dioxide (CO₂) and nuclear waste has much in common, and valuable lessons can be learnt from a comparison. Seeking to compare these technologies economic, social and environmental criteria need to be selected and expressed in terms of indicators. Very important issue is costs and economics of geological storage of carbon dioxide and nuclear waste. The costs of storage are one of the main indicators for assessment of technologies in terms of economic criteria.The paper defines the costs of the geological storage of CO₂ and nuclear waste in Lithuania, drawing also on insights from other parts of the world. The costs of carbon dioxide and nuclear waste storage are evaluated in UScnt/kWh and compared. The paper critically compares the characteristics and location of the both sources of and storage options for CO₂ and nuclear waste in Lithuania. It discusses the main costs categories for carbon dioxide and nuclear waste storage. The full range of potential geological storage options is considered and the most reliable options for carbon dioxide and nuclear waste are selected for the comparative costs assessment.     

Rate controlling reactions for copper corrosion in anaerobic aqueous sulphide solutions

Abstract

The long term corrosion behaviour of copper in anoxic aqueous sulphide solutions has been studied using corrosion potential and electrochemical impedance spectroscopy measurements and scanning electron microscopy on corroded surfaces and cross-sections of surfaces prepared using a focused ion beam. Experiments were conducted in solutions containing either 5×10^?4 or 5×10^?5 mol L^?1 sulphide for 1691 and 4000 h respectively. In the more concentrated solution, a coherent, compact and crystalline chalcocite (Cu₂S) film accumulated on the corroding copper surface. A parabolic growth law was obtained, and the kinetics were controlled by Cu(I) ion transport either through the Cu₂S matrix or along crystalline grain boundaries in the film. In the more dilute solution, the growth of a less crystalline, porous chalcocite layer followed approximately the linear growth kinetics controlled by sulphide ion transport through the pores. If the sulphide was allowed to deplete in the dilute solution, rate control switched to sulphide diffusion in the bulk solution. The implications for waste container corrosion in a nuclear waste repository are discussed.     

Choosing a standard reactor: International competition and domestic politics in Chinese nuclear policy

China has ambitious plans to expand its nuclear power capacity. One of the policy goals that high-level policymakers have desired is to base the nuclear program on a standardized reactor design. However, this has not materialized so far. By examining its nuclear reactor choices for individual projects, we argue that China’s policymaking process has been greatly influenced by international competition and domestic politics. Multiple international nuclear vendors are intent upon maintaining their respective niches in the expanding Chinese reactor market, and they have used various forms of economic and political pressure to achieve their objectives. On the other hand, China’s policymaking process is fragmented and the shifting power balances among powerful domestic actors do not allow a fixed path to be followed. Further, because of the high costs and potential profits involved, nuclear reactor choices in China have been driven not just by technical considerations but also by foreign and trade policy objectives. All of these make it unlikely that China will standardize the reactor type it constructs in the near future.     

Managing spent nuclear fuel in South Korea: Heterogeneous public attitudes toward different management strategies at individual- and segment levels

The management of spent nuclear fuel is a problem shared by countries that are operating nuclear power plants or have done so in the past. To implement socially agreed spent nuclear fuel management policies, it is necessary to recognize public attitudes and preferences toward policies. This study analyzed public preferences at the individual- and segment levels toward spent nuclear fuel management strategies in South Korea using a choice experiment and the hierarchical Bayesian normal mixture discrete choice model. Furthermore, it compared public acceptance for different types of management strategies using ex-ante simulation. Accordingly, the public was categorized into two groups. Segment 1 (31.62%) took a smaller proportion of the population than segment 2 (62.38%) and showed a higher degree of heterogeneity than segment 2. Segment 1 was more sensitive to increased electricity costs than segment 2 because of the implementation of spent nuclear fuel management policies and preferred a democratic process. Based on the results, we expect that the Korean government would receive public support when proceeding with the construction and operation of a permanent spent nuclear fuel repository facility. However, considering the degree of heterogeneity, governmental efforts to achieve social consensus are necessary.     

Nuclear energy: Status and future limitations

The status of nuclear energy today and its potential evolution during the next 10–20 years is discussed. Nuclear energy contributes only about 14% of the world’s electric energy mix today, and as electric energy contributes itself only about 16% to the end energy use, its contribution is essentially negligible. Still, nuclear energy is plagued already with a long list of unsolved problems. Among the less known problems one finds the difficulties that nuclear plants cannot provide power according to needs, but have to be operated at full power also during times of low demand and regions with large contributions from nuclear power need some backup hydropower storage systems. The better known problems, without solutions since at least 40 years, are the final safe storage of the accumulated highly radioactive nuclear waste, that uranium itself is a very limited and non renewable energy resource and that enormous amounts of human resources, urgently needed to find a still unknown path towards a low energy future, are blocked by useless research on fusion energy. Thus, nuclear energy is not a solution to our energy worries but part of the problem.     

电石热回收技术分析与探讨

传统电石生产工艺中,电石产品出炉后仍具有大量余热,但难以有效回收,而且冷却过程长时间占用场地。在国内此余热回收利用的研究很少,项目应用几乎空白。从行业总体规模出发,评估国内电石热可利用的总量,归纳电石产品降温过程特性,总结余热回收的技术难点。综合已有文献和专利分析,归纳余热回收的技术路线并予以评价,提出了一种加快取热的方法。     

我国内陆核电选址决策思考及安全环境问题探讨

核能作为清洁绿色能源,是发展低碳经济的必然选择,在发展核电的同时更要重视其安全性;今后我国核电选址将是沿海、内陆并举,核电规划应符合总体国家安全,选址要与自然生态、城市规划和环境相协调,遵循审慎决策原则。厂址的安全性是保证核电厂安全运行的前提条件,随着厂址资源的日益稀缺,选址阶段需要关注的问题愈发复杂,除了考虑地质水文气象、水资源等自然条件,人口密度分布、大气水体弥散条件、公众参与和核事故应急响应等也是影响厂址成立的主要因素,需要做深入探讨。结合国情不断地完善我国的核安全法规标准体系和核监管体系,从而保证核电厂从选址、设计、建造、运行和退役整个过程都是安全可靠经济的。     

Evaluating options for the future energy mix of Japan after the Fukushima nuclear crisis

The Fukushima nuclear accident in March 2011 has increased social and political reluctance to embrace nuclear power in Japan (and elsewhere). The Japanese government has thus been considering four possible future energy mixes, including a nuclear-free pathway, and three others with 10%–35% nuclear supply coupled with a larger proportion of renewable energy and fossil fuels to replace nuclear. Here we use multi-criteria decision-making analysis (MCDMA) to assess the potential negative economic (levelised cost of electricity, and energy security), environmental (greenhouse-gas emissions, land transformation, water consumption, heated water discharge, air pollution, radioactive waste, and solid waste) and social (safety issues) impacts of the four proposed pathways to determine which scenario most holistically minimises adverse future outcomes. The nuclear-free pathway has the highest overall potential for adverse outcomes (score=2.49 out of 3), and the 35% nuclear power supply option yielding the lowest negative impact score (0.74) without weightings. Despite some sensitivity to the choice of criterion weights, our analyses demonstrate clearly that from an empirical perspective, a nuclear-free pathway for Japan is the worst option to pursue. We recommend that MCDMA methodology we used for Japan can be applied to other countries to evaluate future electricity generation scenarios.     

Safe and Secure

This paper focuses on the issues critical to the operation of commercial nuclear power electric generating plants. These issues include safe, secure long-term plant operations, plant physical security, radioactive waste management, and environmental impact. Few energy choices can compete with the environmental benefits of nuclear power. By capturing and sequestering waste products during the entire fuel cycle, nuclear power is one of the cleanest baseload energy sources available. Long-term storage of used fuel is technically feasible in both aboveground storage containers and in underground geologic formations. Continued research into new nuclear reactors is expected to allow for almost complete consumption of the available unused fuel in high level waste