Disposal Program Research Articles

Evaluation of the long-term behavior of potential plutonium waste forms in a geological repository

ABSTRACTVarious candidate waste matrices such as nuclear waste glasses, ceramic waste forms and low-specification “storage” MOX have been considered within the current UK geological disposal program for the immobilization of separated civilian plutonium, in the case this material is declared as waste. A review and evaluation of the long-term performance of potential plutonium waste forms in a deep geological repository showed that (i) the current knowledge base on the behavior and durability of plutonium waste forms under post-closure conditions is relatively limited compared to HLW-glasses from reprocessing and spent nuclear fuels, and (ii) the relevant processes and factors that govern plutonium waste form corrosion, radionuclide release and total systems behavior in the repository environment are not yet fully understood in detail on a molecular level. Bounding values for the corrosion rates of potential plutonium waste forms under repository conditions were derived from available experimental data and analogue evidence, taking into account that the current UK disposal program is in a generic stage, i.e. no preferred host rock type or disposal concept has yet been selected. The derived expected corrosion rates for potential plutonium waste forms under conditions relevant for a UK geological disposal facility are in the range of 10-4 to 10-2 g m-2 d-1 and 10-5 to 10-4 g m-2 d-1 for borosilicate glasses, and generic ceramic waste forms, respectively, and ∼5·10-6 g m-2 d-1 for storage MOX. More realistic assessments of the long-term behavior of the waste forms under post-closure conditions would require additional systematic studies regarding the corrosion and leaching behavior under more realistic post-closure conditions, to explore the safety margins of the various potential waste forms and to build confidence in long-term safety assessments for geological disposal.

The Use of Clay as an Engineered Barrier in Radioactive-Waste Management — A Review

AbstractGeological disposal is the preferred option for the final storage of high-level nuclear waste and spent nuclear fuel in most countries. The selected host rock may be different in individual national programs for radioactive-waste management and the engineered barrier systems that protect and isolate the waste may also differ, but almost all programs are considering an engineered barrier. Clay is used as a buffer that surrounds and protects the individual waste packages and/or as tunnel seal that seals off the disposal galleries from the shafts leading to the surface.Bentonite and bentonite/sand mixtures are selected primarily because of their low hydraulic permeability in a saturated state. This ensures that diffusion will be the dominant transport mechanism in the barrier. Another key advantage is the swelling pressure, which ensures a self-sealing ability and closes gaps in the installed barrier and the excavation-damaged zone around the emplacement tunnels. Bentonite is a natural geological material that has been stable over timescales of millions of years and this is important as the barriers need to retain their properties for up to 106 y.In order to be able to license a final repository for high-level radioactive waste, a solid understanding of how the barriers evolve with time is needed. This understanding is based on scientific knowledge about the processes and boundary conditions acting on the barriers in the repository. These are often divided into thermal, hydraulic, mechanical, and (bio)chemical processes. Examples of areas that need to be evaluated are the evolution of temperature in the repository during the early stage due to the decay heat in the waste, re-saturation of the bentonite blocks installed, build-up of swelling pressure on the containers and the surrounding rock, and degradation of the montmorillonite component in the bentonite. Another important area of development is the engineering aspects: how can the barriers be manufactured, subjected to quality control, and installed?Geological disposal programs for radioactive waste have generated a large body of information on the safety-relevant properties of clays used as engineered barriers. The major relevant findings of the past 35 y are reviewed here.

Review of environmental aspects and waste management of stone cutting and fabrication industries

Iran is the second largest stockholder of construction stones with 10 % of world production ;and there are more than 4000 stone cutting and fabrication industries (SCFIs). In the processing of raw stones, a considerable part of stone is turned into waste. Generated wastes include excess parts of different stones and sludge. The present paper reviews the state of SCFIs waste management using multiple data sources including site, analysis of effluent and sludge samples, and conducting interviews with people who are involved in 286 SCFIs in Qom and Tabriz. The results revealed that currently almost 35 to 52.5 % of raw stones were converted to solid wastes depending on stone cutting and processing methods, type of stones and their quality, which seemed a high percentage. Also, the effluents between 0.8 and 2.8 m3 were generated per ton of processed stone. Based on the analysis of heavy metals with atomic absorption spectroscopy, sludge samples contained a considerable amount of Pb, Cu, Cr, and Cd. It was also found that the lack of specific recycling, reuse and disposal programs and suitable supervision has led to uncontrolled disposal of stone wastes and sludge in different areas. However, there are good opportunities for reuse and recycling of the SCFIs wastes.

Unintentional opioid overdose deaths in New York City, 2005–2010: A place-based approach to reduce risk

BackgroundDrug poisoning is the leading cause of death from injuries in the United States. In New York City (NYC), unintentional drug poisoning death is the third leading cause of premature death, and opioids are the most commonly occurring class of drugs. Opioid overdose prevention efforts aim to decrease the number of people at risk for overdose and to decrease fatality rates among those using opioids by improving overdose response. These strategies can be enhanced with a comprehensive understanding of the settings in which overdoses occur. MethodsA cross-sectional analysis of unintentional opioid poisoning deaths in NYC from 2005 to 2010 (n=2649). Bivariate and multivariate analyses were performed to identify factors associated with settings of fatal opioid overdose. ResultsThree-quarters of the sample overdosed in a home; one-tenth in an institution, and the remaining in a public indoor setting, the outdoors or another non-home setting. Factors associated with overdosing at home include female gender, college degree, residence in the borough of Staten Island, and combined use of opioid analgesics and benzodiazepines. Factors associated with overdosing outside of the home include ages 35–64, residence in Manhattan, and use of heroin. ConclusionThe sample represents a near census of unintentional opioid overdose deaths in NYC during the study period, and allows for the identification of demographic and drug-using patterns by setting of overdose. Because most opioid overdoses occur inside the home, opioid overdose response programs can most efficiently address the epidemic by both reducing the risk of overdose in the home and targeting those who may be in the home at the time of an overdose for overdose response training. Approaches include minimizing risk of misuse and diversion through safe storage and safe disposal programs, physician education on prescribing of opioid analgesics and benzodiazepines, prescription of take-home naloxone, and Good Samaritan laws.

Deployment of Radioactive Waste Disposal Facility with the Introduction of Nuclear Power Plants (NPP) in Kenya

This paper describes basic plans for the development of a radioactive waste disposal facility with the introduction of Nuclear Power Plants (NPPs) for Kenya. The specific objective of this study was to estimate the total projected waste volumes of low- and intermediate-level radioactive waste (LILW) expected to be generated from the Kenyan nuclear power programme. The facility is expected to accommodate LILW to be generated from operation and decommissioning of nuclear power plants for a period of 50 years. An on-site storage capacity of 700 <TEX>$m^3$</TEX> at nuclear power plant sites and a final disposal repository facility of more than 7,000 <TEX>$m^3$</TEX> capacity were derived by considering Korean nuclear power programme radioactive waste generation data, including Kori, Hanbit, and APR 1400 nuclear reactor data. The repository program is best suited to be introduced roughly 10 years after reactor operation. This study is important as an initial implementation of a national LILW disposal program for Kenya and other newcomer countries interested in nuclear power technology.

Simulation of Reactive Diffusion in Clays By a Continuous-Time Markovian Particle-Tracking Scheme

Clay minerals and clay rocks are considered as efficient components of engineered and natural barriers in many high-level radioactive waste disposal programs worldwide because of their low permeabilities and high sorption capabilities. In this paper we present an approach for modeling solute diffusive transport in saturated clay minerals at the structure map scale based on an extension of the Kolmogorov–Dmitriev theory of stochastic branching processes. The proposed modeling framework allows a simple description of (i) the dual-porosity behavior typical of some compacted clay structures, where diffusion occurs both in the interlayers and in the pore space between clay particles, and (ii) the chemical interactions between the dissolved ions and the solid matrix surfaces (both at nonequilibrium and equilibrium conditions). Furthermore, the Markovian nature of the modeling approach lends itself to a continuous-time particle-tracking scheme of resolution of the model equations, which, in general, easily allows us to deal with the complex geometrical structures of the porous media. Finally, in order to account for the uncertainty in the geometrical properties of the clay samples within the proposed modeling framework, the structure map is represented as a stochastic network of interconnected, one-dimensional interlayers with different lengths and orientations. The combined methods are demonstrated on a two-dimensional literature case study of diffusion through a compacted clay sample, and the resulting average diffusion coefficients are in general agreement with those obtained by a different simulation-based technique found in the literature. Then, the methods are applied to model the diffusion of the weakly sorbing cation Na+, providing results in accordance with physical intuition.

사용후핵연료 심층처분을 위한 지하연구시설(URL)의 필요성 및 접근 방안

This study gives a conceptual and basic direction to develop a URL (underground research laboratory) program for establishing the performance and safety of a deep geological disposal system in Korea. The concept of deep geological disposal is one of the preferred methodologies for the final disposal of spent nuclear fuel (SNF). Advanced countries with radioactive waste disposal have developed their own disposal concepts reasonable to their social and environmental conditions and applied to their com-mercial projects. Deep geological disposal system is a multi-barrier system generally consisting of an engineered barrier and natural barrier. A disposal facility and its host environment can be relied on a necessary containment and isolation over timescales envisaged as several to tens of thousands of years. A disposal system is not allowed in the commercial stage of the disposal program without a validation and demonstration of the performance and safety of the system. All issues confirming performance and safety of a disposal system include investigation, analysis, assessment, design, construction, operation and closure from planning to closure of the deep geological repository. Advanced countries perform RD&D (research, development & demonstration) programs to validate the performance and safety of a disposal system using a URL facility located at the preferred rock area within their own territories. The results and processes from the URL program contribute to construct technical criteria and guidelines for site selection as well as suitability and safety assessment of the final disposal site. Furthermore, the URL program also plays a decisive role in promoting scientific understanding of the deep geological disposal system for stakeholders, such as the public, regulator, and experts.

Nitrate source apportionment in a subtropical watershed using Bayesian model

Nitrate (NO3−) pollution in aquatic system is a worldwide problem. The temporal distribution pattern and sources of nitrate are of great concern for water quality. The nitrogen (N) cycling processes in a subtropical watershed located in Changxing County, Zhejiang Province, China were greatly influenced by the temporal variations of precipitation and temperature during the study period (September 2011 to July 2012). The highest NO3− concentration in water was in May (wet season, mean±SD=17.45±9.50mgL−1) and the lowest concentration occurred in December (dry season, mean±SD=10.54±6.28mgL−1). Nevertheless, no water sample in the study area exceeds the WHO drinking water limit of 50mgL−1 NO3−. Four sources of NO3− (atmospheric deposition, AD; soil N, SN; synthetic fertilizer, SF; manure & sewage, M&S) were identified using both hydrochemical characteristics [Cl−, NO3−, HCO3−, SO42−, Ca2+, K+, Mg2+, Na+, dissolved oxygen (DO)] and dual isotope approach (δ15N–NO3− and δ18O–NO3−). Both chemical and isotopic characteristics indicated that denitrification was not the main N cycling process in the study area. Using a Bayesian model (stable isotope analysis in R, SIAR), the contribution of each source was apportioned. Source apportionment results showed that source contributions differed significantly between the dry and wet season, AD and M&S contributed more in December than in May. In contrast, SN and SF contributed more NO3− to water in May than that in December. M&S and SF were the major contributors in December and May, respectively. Moreover, the shortcomings and uncertainties of SIAR were discussed to provide implications for future works. With the assessment of temporal variation and sources of NO3−, better agricultural management practices and sewage disposal programs can be implemented to sustain water quality in subtropical watersheds.

Community-acquired, non-occupational needlestick injuries treated in US Emergency Departments

The escalating number of persons self-injecting medications, predominantly insulin, has generated concerns that the public is at risk of acquiring blood-borne infections from discarded needles/syringes. Communities have developed disposal guidelines but a debate continues over the need for further legislation and/or at-home safety devices. This study examines the number, characteristics, treatment and costs of community-acquired needlestick injuries (CANSIs). US-representative CANSI rates and characteristics were derived from 2001-08 National Electronic Injury Surveillance System All Injury Program data on product-related injuries treated at US emergency departments (EDs). CANSI-related medical care was examined using 2003-09 National Hospital Ambulatory Medical Care Surveys, representing all US ED visits. Cost analyses used 2010 Current Procedural Terminology Coding and Medicare rates. In 2001-08, an estimated 16 677 CANSIs were treated in US EDs, with an associated annual rate of 0.7 per 100 000 US citizens (95% CI 0.6-0.8) and no observable temporal trend. The estimated maximum annual medical cost of ED-treated CANSIs was $9.8 million, or $0.03 per citizen, $1.66 per insulin-injecting person and $0.0018 per insulin injection. US ED-treated CANSI rates are extremely low. Stricter disposal programs and the at-home use of safety devices do not appear to be needed at this time.

방사성폐기물 처분안전성 평가 자료 제공을 위한 핵종 수착 데이터베이스(KAERI-SDB) 개발

방사성폐기물 처분 안전성 평가를 위하여 방사성 핵종의 수착특성에 대한 정보제공이 필요하다. 그러나 우리나라는 최근까지 핵종 수착 데이터베이스에 대한 접근성이 취약하여 이용에 제한이 있었다. 사용자들에게 효율적인 방법으로 핵종 수착관련 정보를 제공하기 위해 웹을 기반으로 하는 핵종 수착 데이터베이스(KAERI-SDB)를 개발하였다. KAERI-SDB를 개발하기 위하여 1998년에 개발된 수착 데이터베이스 프로그램인 SDB-21C을 분석하고 사용자 요구사항을 반영하였으며, 사용자가 웹 브라우저를 통하여 실시간으로 수정 및 보완된 핵종 수착 자료에 실시간으로 접근이 가능하도록 구성하였다. KAERI-SDB는 로그인/회원가입, 자료 검색 및 저장 그리고 검색결과에 대한 차트 구현 등의 기능들이 포함되도록 고안되었다. KAERI-SDB는 수착 자료를 이용하고자 하는 이용자들의 접근성을 향상함으로써 방사성폐기물 처분 안전성 평가에 폭넓게 활용될 것으로 예상된다. 나아가, 핵종 수착관련 자료들을 일반인에게 공개함으로써 방사성폐기물 처분 프로그램에 대한 신뢰도와 대중 수용성을 증진시킬 수 있을 것으로 기대된다. Radionuclide sorption data is necessary for the safety assessment of radioactive waste disposal. However the use of sorption database is often limited due to the accessability. A web-based sorption database program named KAERI-SDB has been developed to provide information on the sorption of radionuclides onto geological media as a function of geochemical conditions. The development of KAERI-SDB was achieved by improving the performance of pre-existing sorption database program (SDB-21C) developed in 1998 and considering user's requirements. KAERI-SDB is designed that users can access it by using a web browser. Main functions of KAERI-SDB include (1) log-in/member join, (2) search and store of sorption data, and (3) chart expression of search results. It is expected that KAERI-SDB could be widely utilized in the safety assessment of radioactive waste disposal by enhancing the accessibility to users who wants to use sorption data. Moreover, KAERI-SDB opened to public would also improve the reliability and public acceptance on the radioactive waste disposal programs.

Policy topics: Groundwork for patient care, dialogue

Policy topics: Groundwork for patient care, dialogue

Variations in the Water Quality of an Urban River in Nigeria

Sango-Ota is the industrial nerve centre of Ogun State in Nigeria. River Atuara is an urbanized river in this town. The aim of this study is to assess the quality of water in the river along its 13 km urbanized stretch within Owode – Ota and Gbenga quarters of Sango – Ota in Ogun State, Nigeria. A study of some physical and chemical analysis was carried out to determine the level of pollution in the river. Total Dissolved Solids, TDS, pH, Colour and Temperature measurements were obtained for nine locations on the 21 km river stretch. Laboratory analyses were carried out at 4 locations along the water course for the following parameters: pH, Conductivity, Turbidity, DO, BOD, COD, TDS, TSS. Others include Phosphate, Chloride, Nitrate, Sulphate, Cadmium, Lead, Iron, Copper, Zinc, and Nickel. Results indicate that the water quality reduces downstream of the urbanized stretch. Some of the level of heavy metals in the river calls for concern. At Owode, the lead content of 0.11 mg/L is too high compared to a maximum of 0.01 mg/l permissible, which can cause cancer. This can interfere with Vitamin D metabolism, and can affect mental development in infants. It is toxic to the central and peripheral nervous systems. Cadmium is below 0.002 which is just below the 0.003 mg/l permitted in Nigeria. Nickel content was 0.046 mg/l between Owode and Ewupe and this is above the maximum permissible level of 0.02 for Nigeria. This has the possibility of carcinogenic health impact. Owode and Ewupe have greater industrial impacts than the other two locations, Igboloye and Gbenga. The trends of each of the 21 parameters from the urbanized stretch of the river have been observed to follow a pattern that can be categorized as similar, mirrored, somersault and composite of mirrored and somersault. More studies were recommended in this direction as well as in determining the locations of factories and industries contributing to the pollution level around Ewupe and their effluent disposal programs will need to be ascertained.

An introduction to package evolution and criticality research studies relevant to the UK disposal programme

AbstractIn the UK, radioactive wastes currently planned for disposal in a geological disposal facility (GDF) include intermediate level waste, some low level waste and high level waste. Disposal of other materials, including spent fuel, uranium and plutonium is also being evaluated to inform the safety case for a GDF, if such materials were to be classified as wastes in the future. This paper describes the generic safety functions through which waste packages can contribute to the safety case of a GDF in the UK. It describes the engineering approach used or envisaged, in the UK and internationally, to ensure that waste packages retain their safety functions for the required periods of time and summarizes the scientific basis underpinning the current understanding of relevant evolution processes. Where gaps in the knowledge exist, the Nuclear Decommissioning Authority Radioactive Waste Management Directorate has identified specific research activities needed to close out such gaps to a level of maturity sufficient for this stage of the disposal programme (generic). This paper describes the latest results from their R&amp;D programme and presents a summary of the research activities planned to meet the current needs of the disposal programme with specific reference to the topics of package evolution and criticality safety.

An introduction to geosphere research studies for the UK geological disposal programme

AbstractThis paper gives an overview of the geosphere research studies being undertaken by the Radioactive Waste Management Directorate (RWMD) of the Nuclear Decommissioning Authority. The approach of the RWMD in the current generic phase of the UK managing radioactive waste safely (MRWS) programme is to maintain an understanding of key processes and to carry out research and development into techniques so capability can be built. Although RWMD can demonstrate a general understanding of geosphere processes at this stage in the UK project, it is recognized that this will need to be made site-specific as the MRWS programme progresses. An understanding of the geosphere at the selected site(s) will be an important part of the future programme. Where possible, the RWMD will participate in international studies so that relevant site-based information can be accessed. In this way, the RWMD will be prepared for site-specific work in stage 5 of the MRWS process.

Representation of the biosphere in post-closure assessments for the UK geological disposal programme

AbstractThis paper gives an overview of the Nuclear Decommissioning Authority, Radioactive Waste Management Directorate approach to representing the biosphere in post-closure safety assessment studies. The assessments consider potential releases of radionuclides and chemically toxic substances from a geological disposal facility that may reach the biosphere by transport in groundwater and gas. It gives an outline of the key processes and understanding underpinning the representation of the biosphere and how the biosphere may evolve over the long timescales of relevance to post-closure safety. The current biosphere assessment approach and associated models are supported by research studies and collaboration that ensure they are consistent with international recommendations. Research studies are also commissioned to reduce uncertainty surrounding key contaminants and potential exposure pathways and to help ensure that the approach and models are adaptable and flexible enough to incorporate future developments, as the geological disposal programme moves towards site selection.

An overview of near-field evolution research in support of the UK geological disposal programme

AbstractThe near field, together with the containment and isolation provided by the geosphere, contributes to the long-term safety provided by a geological disposal facility (GDF) after closure. The different engineered barriers can prevent or limit the release of radionuclides and their migration to the undisturbed host rock or geosphere and are expected to fulfil their post-closure safety functions for many thousands to hundreds of thousands of years. They will continue to contribute to containment after their eventual degradation when there would no longer be confidence that they would continue to fulfil all of their safety functions in their totality. By that time, significant radioactive decay will have occurred, substantially reducing the hazard associated with the wastes. Therefore, demonstration of long-term safety requires an understanding of the evolution of the engineered barriers and the consequences for the generic safety functions that the different barriers provide. This paper provides an overview of the research of the Nuclear Decommissioning Authority Radioactive Waste Management Directorate into the evolution of the near field of a GDF.

Geological disposal programme design and prioritization in the face of uncertainty: use of structured evidence support logic techniques

AbstractProgrammes for the geological disposal of radioactive wastes are by nature extremely complex. A structured approach for making and documenting varied kinds of decisions is required to support programme design and implementation. At each programme stage, the decision-making process must be able to identify and justify key priorities for work, to reduce uncertainties.To support structured decision-making evidence support logic (ESL) has been developed and applied to varied complex projects, nationally and internationally, in several industries. Evidence support logic involves breaking down a hypothesis that informs a decision into a hierarchical 'decision tree'. Examples of hypotheses are 'the geology associated with site x will provide sufficient disposal capacity', 'container x will contain waste form y for z years' and 'the engineered barrier system will provide the required safety functions'. Independent evaluations of confidence 'for' and 'against' bottom-level hypotheses allow the level of remaining uncertainty (or conflict) to be recognized explicitly, and the overall confidence (and uncertainty) relevant to the overall decision, and key sensitivities, to be represented clearly and succinctly.Thus ESL can help (1) break down decisions into a manageable and logical structure, assisting clear presentation; (2) identify key uncertainties and sensitivities to inform prioritization; and (3) test whether the outcomes of specific studies have improved confidence.

An overview of radionuclide behaviour research for the UK geological disposal programme

AbstractIn the UK, radioactive wastes currently planned for disposal in a geological disposal facility (GDF) are intermediate-level waste, some low-level waste and high-level waste. Disposal of other materials, including spent fuel, separated uranium and separated plutonium are also included in the planning of a GDF, if such materials are classified as wastes in the future. This paper gives an overview of the radionuclide behaviour research studies of the Nuclear Decommissioning Authority Radioactive Waste Management Directorate (NDA RWMD). The NDA RWMD's current understanding of the processes that control radionuclide behaviour in groundwater and how the engineered and natural barriers in a GDF would contain radionuclides is presented. Areas requiring further work are also identified.

Performance assessment and the safety case: lessons from the European Commission PAMINA project

AbstractA three-year European Commission project entitled performance assessment methodologies in application to guide the development of the safety case (PAMINA) was conducted in the period 2006–2009 and brought together 27 organizations from ten European countries, including the Nuclear Decommissioning Authority and Galson Sciences Ltd from the UK. The PAMINA project had the aim of improving and developing a common understanding of performance assessment (PA) methodologies for disposal concepts for spent fuel and other long-lived radioactive wastes in a range of geological environments.Work undertaken within PAMINA focussed on four areas: (1) review of PA methodologies in participating organizations; (2) treatment of uncertainty in PA and the safety case; (3) other methodological advancements in PA; and (4) relevance of advanced PA approaches to practical cases.The state of development of a radioactive waste disposal programme has a strong influence on the type of safety case and supporting PA that is produced. A range of PA methodologies has been developed by different waste management organizations. This paper presents a selection of conclusions from the PAMINA project, in the context of general understanding developed on what would constitute an acceptable safety case for a geological disposal facility, and outlines areas for further development.

An overview of gas research in support of the UK geological disposal programme

AbstractGases will be generated in waste packages during their transport to a geological disposal facility (GDF), this generation will continue during GDF operations and after GDF closure. The range of gases produced will include flammable, radioactive and chemotoxic species. These must be managed to ensure safety during transport and operations, and the post-closure consequences need to be understood. The two primary post-closure gas issues for a GDF are the need for the system pressure to remain below a value at which irreversible damage to the engineered barrier system and host geology could occur, and the need to ensure that any flux of gas (in particular gaseous radionuclides) to the biosphere does not result in unacceptable risk. This paper provides an overview of the research of the Nuclear Decommissioning Authority, Radioactive Waste Management Directorate into gas generation and its migration from a GDF.