Before loading campaigns, a number of spent fuel assemblies would be selected as targets for surveillance of the long-term behaviour of spent fuel in dry-storage conditions. These selected assemblies will be characterized in detail, including inspection by high resolution colour TV, noble gas seeping, profilometry, and gamma spectrometry, as well as separation of one rod and post-irradiation examination of this rod at the laboratory. The remainder of the fuel assembly will be stored in the normal process, preferably at the centre of a vault, where higher temperatures can be expected. The number of fuel assemblies pre-selected for examination is limited to six (two low burn-up PWR; two high burn-up PWR; one BWR low burn-up; one BWR high burn-up), taking into account the complexity and cost of this characterisation. If there is not a technical specification or contractual provision forbidding filling up a canister with fuel from different power plants, they will be stored in only two different canisters.
6 Conclusion and discussion
Integrated 1D simulations of atmospheric carbonation coupled with the drying process of ILLW concrete disposal packages in deep geological conditions during the operating period were performed. Complete drying of the 11 cm thick wastedisposal package wall occurs over a period ranging from 2 years for the low-performance concrete to 10 years for the high-performance concrete. The drying process slows down when hydraulic and transport properties of the cementitious material are enhanced. The simulations also provide a first evaluation of total carbonated depth: about 2 cm after 100 years. These first simulations do not take into account the decrease of chemical reactivity with the decrease of the material water content. The second set of simulations, which takes into account this phenomenon via a Bazant type function, leads to a less intense but deeper carbonation of the cementitious material (about 3 cm after 100 years).
inadequate communication between the designer and user, with a package not meeting specific or regulatory requirements during test or use. This may occur because both parties have assumed, but not confirmed, that all necessary requirements have been taken into account by the other party in their interfacing activities. Interfaces between groupings such as design, testing and manufacture or user, carrier, storage operator, disposal operator and conditioning unit will frequently occur however, other more infrequent interfaces should not be overlooked as these often create or add to problems and misunderstandings in radioactive waste management processes.
Figure 1. Concrete vault layout.
The facility will be a stand‐alone facility providing its own administrative support and maintenance infrastructure. The facility will be laid out in a manner which will allow trucks to enter the disposal facility and proceed directly to the unloading area where a dedicated crane will unload the shielded transportation package and deposit the waste directly into the concrete vault system while minimizing direct radiation exposure to facility workers. A cask‐to‐vault adapter system will be used to provide a shielded interface between the transportation cask and the concrete vault, also reducing exposure to radiation during waste placement operations. Figure 2 illustrates the facility layout and also shows the cask unloading activities expected to be utilized in the project.
All materials that are contained in typical waste streams can be treated by plasma with visible effects. Especially all materials constituting waste from nuclear power plant operations are treatable. In general the combustible materials burn and the non-combustible materials melt. A partial vitrification was observed when mixing material with glass particles. An effect is visible after a few seconds of treatment and the longer the treatment, the more distinct is the effect. Metals are also treat- able, though in the experiments the effect was not significant due to the low scale power of the plasma torch. It was observed that melting is easier to achieve with small particle sizes in the samples. The most intense effect or the starting point of the combustion was always in the focus of the plasma. Therefore to achieve a com- plete treatment, the plasma flame has to touch all surfaces for a short time. This, too, is more easily achieved with small grains as the used material to increase the surface.
Proper Segregation and Disposal of Low-Level Radioactive Waste (LLRW) at Wayne State University
Wayne State University-Office of Environmental Health & Safety (OEH&S) will collect and process the various forms of radioactive waste generated at University research facilities provided the waste is properly segregated, packaged and identified according to the methods detailed in these guidelines.
Were entrainment of waste-derived radionuclides in LNAPL to occur, such migration could result in a shorter overall travel time to environmental or human receptors than radionuclide migration solely associated with the movement of groundwater. This paper provides a contribution to the assessment of this issue through multiphase-flow numerical modelling underpinned by a review of the UK's ILW inventory and literature to define the nature of the associated ILW LNAPL source term. Examination has been at the waste package–local GDF environment scale to determine whether proposed disposal of ILW would lead to significant likelihood of LNAPL migration, both from waste packages and from a GDF vault into the local host rock. Our review and numerical modelling support the proposition that the release of a discrete free phase LNAPL from ILW would not present a significant challenge to the safety case even with conservative approximations. ‘ As- disposed’ LNAPL emplaced with the waste is not expected to pose a significant issue. ‘Secondary LNAPL’ generated in situ within the disposed ILW, arising from the decomposition of plastics, in particular PVC (polyvinyl chloride), could form the predominant LNAPL source term. Released high molecular weight phthalate plasticizers are judged to be the primary LNAPL potentially generated. These are expected to have low buoyancy-based mobility due to their very low density contrast with water and high viscosity. Due to the inherent uncertainties, significant con- servatisms were adopted within the numerical modelling approach, including: the simulation of a deliberately high organic material — PVC content wastestream (2D03) within an annular grouted waste package vulnerable to LNAPL release; upper bound inventory estimates of LNAPLs;
In conclusion, if the concrete is properly designed and carefully produced with good quality control forms, it is as an inherently durable material. However, several factors may affect the durability of concrete: constituent materials, construction practices, physical properties, environmental exposure conditions and types of loads. One of the most important factors is connected to the construction practices, i.e. to avoid the use of pre-rusted rebars. It is well recognized that concrete construction methods and practices influence the final quality of the concrete. Besides, the placement of concrete, that includes transporting the concrete to the jobsite delivery point, discharging into formwork, consolidating and providing proper curing conditions, will ensure adequate durability, serviceability and structural integrity in accordance to design specifications. It is worth to mention that, up to now, the site for the Argentine near-surface disposal facility has not been determined. So, as soon as this location is established, it will be necessary to fully characterize the environment for the correct identification of key parameters involved in the long term durability.
As GAO reported in 2004, existing disposal facilities had adequate capacity for most LLRW and were accessible to waste generators (hereafter referred to as disposal availability) in the short term, but constraints on the disposal of certain types of LLRW warranted concern. Specifically, South Carolina had decided to restrict access to its disposal facility by mid-2008 for class B and C waste—the facility now accepts about 99 percent of this waste generated nationwide—to only waste generators in the three states of its compact. If there are no new disposal options for class B and C wastes after 2008, licensed users of radioactive materials can continue to minimize waste generation, process waste into safer forms, and store waste pending the development of additional disposal options. While NRC prefers that LLRW be disposed of, it allows on-site storage as long as the waste remains safe and secure. In contrast, disposal availability for domestic class A waste is not a problem in the short or longer term. In 2004, GAO reported that the Utah disposal facility—which accepts about 99 percent of this waste generated nationwide—could accept such waste for 20 years or more under its current license based on anticipated class A waste volumes. Since 2005, the volume of class A waste disposed of has declined by two-thirds primarily because DOE completed several large cleanup projects, extending the capacity for an additional 13 years, for a total of 33 years of remaining disposal capacity.
reaches a value of 0.30 g m –2 . The leaching of Cs is potentially of concern due to the significant contribution of Cs to the activity of the waste. More significantly the two major Cs isotopes contributing to the activity of the waste namely 134 Cs and 137 Cs have half-lives of 2.0652 y and 30.08 y respectively  which means that >10 half- lives should have passed and thus the levels of these isotopes should be negligible (although long-lived 135 Cs would remain), before water ever reaches the glass in any disposal scenario being proposed for UK ILW. Thus, except in an extreme fault scenario, the relative ease by which Cs may be removed from the glass through leaching should not be a problem. The high initial retention level for Cs in the glass is more significant as minimising the amount of Cs that goes into the off-gas is always a challenge for thermal treatment routes.
Who is paying for the repository?
The “polluter pays principle”, common in environmen- tal law, has also been implemented under atomic energy law for final disposal projects. This means that the generators of the waste have to bear all the costs for the construction, operation and sealing of a repository. The waste generators are primarily the operators of nuclear power stations, but can also be institutions in the areas of research, medicine and industry who use radioactive materials and produce radioactive waste. In accordance with § 21b of the Atomic Energy Act, the waste genera- tors are obliged to finance the necessary costs for the con- struction of a repository through contributions. To en- sure that the Federal Government, which is responsible for the construction of repositories, does not have to provide advance financing for an extended period, the Atomic Energy Act and an ordinance on repository advance payment issued as part of this act, stipulate that the annual costs should be borne by the waste generators through advance payment and part-payment systems, and also regulate how this payment is made.
LLW Repository Ltd is a company responsible for the operation and management of the UK National LowLevelWaste Repository site in West Cumbria. Now into their second contract award period, LLW Repository Ltd continues to lead in the implementation of the National LowLevelWaste Strategy ensuring the effective management of lowlevelwaste across the nation on behalf of the Nuclear Decommissioning Authority (NDA). LLW Repository Ltd has driven an innovative, supply chain focused programme to optimise the management of ‘lower activity’ waste such that disposal and storage capacity at the national repository can be preserved and extended.
Over the past few decades, extensive research and development programs related to deep disposal of HLW have been conducted by international nuclear com- munity. The underground research laboratories (URLs) are developed in several countries such as Sweden, Germany, Switzerland, Canada, Belgium and Japan to address the fundamental issues on whether or not a particular rock mass type would be suitable as a repository host rock. Compared with these nuclear nations, the current Chinese HLW disposal program is still at the preliminary stage, and some scientific and technological issues are needed to be further studied.
However, the several site selection processes currently underway all seek to involve in the decision process a broad range of different stakeholders.
23. It is important to emphasize that wastedisposal in any country involves a sequence of decisions spread out over decades. Each of these is, in theory, reversible although, in practice, some approaches would lend themselves to reversibility better than others. For example, switching from direct disposal of spent fuel to reprocessing would be easier if spent fuel were in long term surface storage rather than buried in a geological repository. Reasons that some stakeholders might prefer approaches that ease later reversibility include the greater ability to take advantage of new technology, of new management approaches, of enhanced safety options, of new scientific information and of changed economic circumstances.
Geosciences 2017, 7, 57 9 of 11
surfaces. The structure of the biofilms formed was surface dependent with the NRVB and graphite biofilms having a complex eDNA, lipid, and polysaccharide structure. The steel on the other hand had a clear eDNA base which anchored the more complex biofilm to the steel surface. The formation of these biofilms was only possible however, when the ambient pH was below pH 13. This indicates that in order to propagate through cracks or fissures in the NRVB, microbes would require an initiation point of active microbial metabolism. Such an initiation point could for example be associated with an actively growing biofilm or a region of cellulosic waste that has acidified due to microbial activity . In the presence of an active biofilm, the sorption of ISA to the NRVB was reduced by limiting the interaction of the NRVB with the solution. Thus, one impact of microbial activity could be increased transport of complexants such as ISA through the near field. However, it should be noted that in an actual ILW-GDF a wide range of other factors will contribute to the overall transport of complexants, including microbial degradation of complexants, consequently at this stage the impact of these microbial process on facility performance is not quantifiable. At the highest pH values where no biofilm was established, all the test surfaces (NRVB, graphite, and steel) became conditioned by the organic components of the microbial flocs, indicating that isolated areas of microbial activity may have wider impacts on the surfaces present within an ILW-GDF. The binding of these organic components may act as a point of attachment for the generation of new biofilms if the overall pH were to fall far enough. This is best illustrated by the steel samples where eDNA was preferentially accumulated on the steel surface and eDNA was seen to anchor the biofilms that formed on these surfaces. Overall, the study demonstrates that the formation of biofilms in the highly alkaline near field of a proposed ILW-GDF is possible provided an initiation point of below pH 12.0 is present. These biofilms will have direct and indirect impacts on the performance of these surfaces through both carbonation and the accumulation of organic biofilm components. These observations emphasize the importance of heterogeneity within the near-field since any areas of reduced pH could allow the initiation of an active microbial population that could then propagate throughout the facility.
To provide for a safe work environment, all infectious agents need to be handled at a certain containment or biosafety level depending on: virulence, pathogenicity, stability, route of spread, communicability, operation(s), quantity, and availability of vaccines or treatment. The applicable biosafety level not only defines the general handling procedures, but also the treatment of biohazardous waste. Under normal circumstances, a risk group 2 agent requires biosafety level 2 containment and biohazardous waste procedures. Nevertheless, if a risk group 2 agent is grown in mass quantities, biosafety level 3 containment is necessary.
Septic tanks must be periodically desludged and cleaned. This is usually carried out mechanically using a tanker. Because of the length of piping involved it is necessary that the cesspool or tank be sited within 30 m of a vehicular access;
however, where the invert level of the tank is more than 3 m below the vehicle access level the 30 m distance will need to be reduced accordingly. Emptying and cleaning should not involve the contents being taken through a dwelling or place of work, and there should be a clear route for the hose so that the emptying and cleaning can be carried out without creating a hazard for the building's occupants. Access covers for emptying and cleaning should be sufficiently durable to resist the corrosive nature of the tank contents and should be designed to prevent unauthorised access (by being lockable or otherwise engineered to prevent personnel entry).