scholarly journals Conceptual Model to Determine Maximum Activity of Radioactive Waste in Near-Surface Disposal Facilities

2016 ◽  
pp. 61-64
Author(s):  
I. Iarmosh ◽  
Yu. Olkhovyk

For development of the management strategy for radioactive waste to be placed in near-surface disposal facilities (NSDF), it is necessary to justify long-term safety of such facilities. Use of mathematical modelling methods for long-term forecasts of radwaste radiation impacts and assessment of radiation risks from radionuclides migration can help to resolve this issue. The purpose of the research was to develop the conceptual model for determining the maximum activity of radwaste to be safely disposed in the NSDF and to test it in the case of Lot 3 Vector NSDF (Chornobyl exclusion zone). This paper describes an approach to the development of such a model. The conceptual model of 90Sr migration from Lot 3 through aeration zone and aquifer soils was developed. The results of modelling are shown. The proposals on further steps for the model improvement were developed.

2017 ◽  
pp. 34-39
Author(s):  
O. Tokarevsky ◽  
I. Iarmosh

The paper considers the conservative scenario of potential exposure that envisages simultaneous destruction of barriers with simultaneous release of radionuclides by the example of Lot 3 near-surface radioactive waste disposal facility at the Vektor Industrial Complex located in the Chornobyl Exclusion Zone. A conceptual model that considers migration of radionuclides through the aeration zone and aquifer to the potable water well, as well as mixing of infiltration water containing radionuclides with ground water in case of reaching the aquifer, was developed to analyze the mentioned scenario. Permissible specific activity of radioactive waste in the facility is calculated under the assumption that radioactive waste contains only 90Sr radionuclide. Normalysa software is used for calculations.


Author(s):  
Ian Upshall

The creation and subsequent access to accurate information is widely accepted as a vital component of a national radioactive waste management strategy. Information on the origin and quantity of the waste together with its physical, chemical and radiological characteristics provides a catalyst for sound and transparent decision making. This information will originate from a number of potentially disparate sources, including material manufacturers, facility operators, waste producers, Government and Non-Government organisations and regulators. The challenge to those with a role in information management in further increased by the fact that much of the information created is required to support activities, not only in the immediate future, but also in the longer-term — typically many decades or even centuries. The International Atomic Energy Agency (IAEA) has published a number of guidance documents under the Safety Series, one of which makes direct reference to information management. The document [1] is intended to assist Member States in the development of a national system for radioactive waste management and identifies the key responsibilities and essential features of such a system. The following statement appears in Section 5: “The regulatory body, the waste generators and the operators of radioactive waste management facilities should maintain documentation and records consistent with the legal requirements and their own needs.” An essential requirement of these ‘documents and records’ is that they should be “...kept in a condition that will enable them to be consulted and understood later by people different from, and possibly without reference to, those who generated the records ...” The scope of the documentation and records to be kept will be wide ranging but will include “...an inventory of radioactive waste, including origin, location, physical and chemical characteristics, and, as appropriate a record of radioactive waste removed or discharged from a facility”, and “site plans, engineering drawings, specifications and process descriptions ... radioactive waste package identification ...”. It is has long been recognised in the United Kingdom that the management of radioactive waste will require the assembly and secure retention of a diversity of records and data. This information will be needed to inform the strategic decision making process, thus contributing to the future safe, environmentally sound and publicly acceptable management of radioactive waste. In the meantime it will also service the nation’s international commitments. When the planning application for a Rock Characterisation Facility (RCF) was refused and the subsequent Nirex appeal rejected in 1997, it was recognised that transfer of waste to a national repository was ulikely to take place for many decades. The long-term preservation of information by the waste management organisations thus became an issue. Since this time, the UK nuclear industry, including the waste producers, regulators and other Government Departments have worked together to develop a common information management system that is now being implemented. It is based on an Oracle database and is supported by ‘electronic tools’ designed to facilitate entry and retrieval of data in a common format. Long-term access to these data underpins many aspects of the system design. Designing such a system and seeing through its development has been a challenge for all those involved. However, as the project nears the completion of the development phase, it is clear there are several benefits in this approach. These include a sharing of best practice, shared development costs, an improved understanding of the needs of all parties, and the use of a common platform and tools. The ‘partnership approach’ between waste management organisations, Government departments and regulators will also reduce the likelihood of future surprises or conflicts of interest. Industry-wide co-operation also provides a greater degree of confidence that the system will continue to enjoy technical and financial support for the foreseeable future. The British Radwaste Information Management System (BRIMS) is supported by the principal waste producers, the Department for Environment, Food and Rural Affairs (DEFRA), the Nuclear Installations Inspectorate (NII) and United Kingdom Nirex Limited (Nirex). All organisations that have participated in its development over the past seven years have free access to it and may use it as part of their waste management strategy.


Author(s):  
P. Poskas ◽  
J. E. Adomaitis ◽  
R. Kilda

The growing number of radionuclide applications in Lithuania is mirrored by increasing demands for efficient management of the associated radioactive waste. For the effective control of radioactive sources a national authorization system based on the international requirements and recommendations was introduced, which also includes keeping and maintaining the State Register of Sources of lonising Radiation and Occupational Exposure. The principal aim of the Lithuania’s Radioactive Waste Management Agency is to manage and dispose all radioactive waste transferred to it. Radioactive waste generated during the use of sources in non-power applications are managed according to the basic radioactive waste management principles and requirements set out in the Lithuanian legislation and regulations. The spent sealed sources and other institutional waste are transported to the storage facilities at Ignalina NPP. About 35,000 spent sealed sources in about 500 packages are expected until year 2010 at Ignalina NPP storage facilities. The existing disposal facility for radioactive waste from research, medicine and industry at Maisiagala was built in the early 1960’s according to a concept typical of those applied in the former Soviet Union at that time. SKB (Sweden) with participation of Lithuanian Energy Institute has performed assessment of the long-term safety of the existing facility. It was shown that the existing facility does not provide safe long-term storage of the waste already disposed in the facility. Two alternatives were defined to remedy the situation. A first alternative is the construction of a surface barrier and a second one is a retrieval solution, whereby the already stored waste will be retrieved for conditioning, characterisation and interim storage at Ignalina NPP. Facilities for the processing of the institutional radioactive waste are required before submittal to Ignalina NPP for storage, since the present facilities are inadequate. Feasibility study to establish a new central facility has been performed by SKB International Consultants (Sweden) with participation of Lithuanian Energy Institute. This study has identified the process applied and equipment needed for a new facility. Reference design and Preliminary Safety Assessment have also been performed. Plans for the interim storage and disposal of the institutional waste are described in the paper. The aspects of finging safe disposal solutions for spent sealed sources in a near surface repositories are also discussed.


Author(s):  
Mick Bacon ◽  
Doug Ilett ◽  
Andy Whittall

In 2006 the UK Governments response to recommendations by its Committee on Radioactive Waste Management (CoRWM) established, in England and Wales, that geological disposal, supported by safe and secure interim storage, is the preferred route for the long-term management of higher-activity radioactive waste (i.e. that which is not suitable for near-surface disposal). It also gave the responsibility for delivering the programme for a deep geological repository to the Nuclear Decommissioning Authority (NDA). The Scottish Government has a policy of long term, near site, near surface safe and secure interim storage. To support the open and transparent approach promised by Government, the Health and Safety Executive (HSE), the Environment Agency and the Scottish Environment Protection Agency (SEPA) are developing joint guidance on the management of higher-activity radioactive waste to explain regulatory objectives in securing safe and secure interim storage and the associated management of radioactive wastes. The guidance comes in two parts: • Guidance on the regulatory process; • Technical guidance modules. The guidance promotes a cradle to grave approach to radioactive waste management and by aligning the regulatory interests of environmental and safety regulators it delivers one of the Government’s “Better Regulation” objectives. This paper describes the process by which the joint guidance was produced with particular emphasis on stakeholder engagement. It describes the key features of the guidance, including the concept of the radioactive waste management case (RWMC). Finally the problems encountered with dissemination and implementation are discussed together with measures taken by the regulators to improve these aspects.


Author(s):  
A. Dreimanis

A unified analysis of the enlargement of the Baldone near-surface radioactive waste (RW) repository RADONS considers the interplay of the existing engineering, safety and infrastructure premises, with the foreseen newly socio-technical features. This enlargement consists in construction of two additional RW disposal vaults and in building a long-term storage facility for spent sealed sources at the RADONS territory. Our approach is based on consecutive analysis of following basic elements: - the origin of enlargement – the RADONS safety analysis and a set of optimal socio-technical solutions of Salaspils research reactor decommissioning waste management; - the enlargement – a keystone of the national RW management concept, including the long-term approach; - the enlargement concept – the result of international co-operation and obligations; - arrangement optimization of new disposal and storage space; - environmental impact assessment for the repository enlargement – the update of socio-technical studies. The study of the public opinion revealed: negative attitude to repository enlargement is caused mainly due to missing information on radiation level and on the RADONS previous operations. These results indicate: basic measures to improve the public attitude to repository enlargement: the safety upgrade, public education and compensation mechanisms. A detailed stakeholders engagement and public education plan is elaborated.


2008 ◽  
Vol 161 (2) ◽  
pp. 156-168 ◽  
Author(s):  
J. Mazeika ◽  
R. Petrosius ◽  
V. Jakimaviciute-Maseliene ◽  
D. Baltrunas ◽  
K. Mazeika ◽  
...  

2018 ◽  
Vol 66 (2) ◽  
pp. 202-210 ◽  
Author(s):  
Elizabeth M. Pontedeiro ◽  
Paulo F. Heilbron ◽  
Jesus Perez-Guerrero ◽  
Jian Su ◽  
Martinus Th. van Genuchten

AbstractIn September 1987 an accident occurred with a cesium chloride (CsCl) teletherapy source taken from a cancer therapy institute in Goiânia, Brazil. Misuse of the abandoned source caused widespread contamination of radioactive material (about 50 TBq of137Cs) in the town of Goiânia. Decontamination of affected areas did lead to about 3,500 m3of solid radioactive wastes, which were disposed in two near-surface repositories built in concrete in 1995. This paper documents a safety assessment of one of the low-level radioactive waste deposits containing137Cs over a time period of 600 years. Using HYDRUS-1D, we first obtained estimates of water infiltrating through the soil cover on top of the repository into and through the waste and its concrete liners and the underlying vadose zone towards groundwater. Calculations accounted for local precipitation and evapotranspiration rates, including root water uptake by the grass cover, as well as for the effects of concrete degradation on the hydraulic properties of the concrete liners. We next simulated long-term water fluxes and137Cs transport from the repository towards groundwater. Simulations accounted for the effects of137Cs sorption and radioactive decay on radionuclide transport from the waste to groundwater, thus permitting an evaluation of potential consequences to the environment and long-term exposure to the public. Consistent with previous assessments, our calculations indicate that very little if any radioactive material will reach the water table during the lifespan of the repository, also when accounting for preferential flow through the waste.


2019 ◽  
Vol 7 (2A) ◽  
Author(s):  
Vanessa Mota Vieira ◽  
Clédola Cássia Oliveira De Tello

The implementation of the national repository is an important technical requirement, and a legal requirement for the entry into operation of the nuclear power plant Angra 3. The Brazilian repository is being planned to be a near-surface one. In Brazil the low and intermediate level radioactive wastes are immobilized using cement and bitumen for Angra 1 and Angra 2 NPP, respectively. The main problems due to the disposal of bituminized wastes in repositories are swelling of the waste products and their degradation in the long term. To accommodate the swelling of the bituminized wastes, the drums are filled up to 70 - 90% of their volume, which reduces the structural the repository stability and the disposal availability. Countries, which use bitumen in the solidification of NPP´s radioactive waste and have near-surface repositories, need to immobilize this bituminized waste within other drums containing cement pastes or mortars to disposal them. This study aims to find solutions for the storage in surface repository of bituminized radioactive waste products, making them compatible with the acceptance criteria of cemented waste products. It was also performed a modeling with the results obtained in the leaching test using the ALT program and defined the transport model of the cesium leachate element and it was verified that in the early times the leaching was governed by the diffusion model and later by the partition model. The results obtained in this study can be used in the evaluation of performance of repositories.


Author(s):  
Peter W. Brennecke

Abstract According to the German disposal concept, all radioactive waste has to be emplaced in a repository constructed and operated in deep geological formations. To get a more detailed insight into site-specific safety-related issues, it is meaningful to perform additional investigations into the radiotoxicity and chemotoxicity. Thus, an evaluation including the hazard potential of organic and inorganic substances being the major constituents of waste packages to be disposed of becomes possible. In addition, possible releases via the water path must be investigated and assessed with regard to the safety of a repository during the post-closure phase, i.e. the radiological long-term effects (radionuclide-specific radiation exposures) as well as the possible pollution of near-surface groundwater by organic and inorganic substances. The latter will particularly take into account the principle of concern of section 34 “Reinhaltung” (Keeping Pure) of the Wasserhaushaltsgesetz (WHG – Water Resources Management Act).


2015 ◽  
Vol 4 (2) ◽  
pp. 119-123
Author(s):  
Nicholas Chan ◽  
Pierre Wong

Segregating radioactive waste at the source and reclassifying radioactive waste to lower waste classes are the key activities to reduce the environmental footprint and long-term liability. In the Canadian Standards Association’s radioactive waste classification system, there are 2 sub-classes within low-level radioactive waste: very short-lived radioactive waste and very low-level radioactive waste (VLLW). VLLW has a low hazard potential but is above the Canadian unconditional clearance criteria as set out in Schedule 2 of Nuclear Substances and Devices Regulations. Long-term waste management facilities for VLLW do not require a high degree of containment and isolation. In general, a relatively low-cost near-surface facility with limited regulatory control is suitable for VLLW. At Canadian Nuclear Laboratories’ Chalk River Laboratories site an initiative, VLLW Sequestration, was implemented in 2013 to set aside potential VLLW for temporary storage and to be later dispositioned in the planned VLLW facility. As of May 2015, a total of 236 m3 resulting in approximately $1.1 million in total savings have been sequestered. One of the main hurdles in implementing VLLW Sequestration is the development of process criteria. Waste Acceptance Criteria (WAC) are used as a guide or as requirements for determining whether waste is accepted by the waste management facility. Establishment of the process criteria ensures that segregated waste materials have a high likelihood to meet the VLLW WAC and be accepted into the planned VLLW facility. This paper outlines the challenges and various factors which were considered in the development of interim process criteria.


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