Fuel Storage Facility Research Articles

Measurement of neutron spectra in spent fuel storage

The neutron spectrum was measured at two locations in the spent fuel storage facility of the Temelín nuclear power plant. The measurement had two primary objectives: to map the neutron -γ field by quantifying the ambient dose equivalent H∗(10) and to identify methods that could improve the quality of the adjusted neutron spectrum using a Bonner Sphere Spectrometer (BSS). Three spectrometers were used: a BSS and two proton recoil spectrometers. Hydrogen-filled proportional counters and an EJ309 scintillator were used to construct the a priori spectrum for BSS adjustment. The details of this process and its results are discussed. The a posteriori spectrum was used to calculate the ambient dose equivalent H∗(10). The resulting spectrum is highly thermalised, but the predominant contribution to H∗(10) was in the 100 keV-1.3 MeV range. The use of hydrogen-proportional counters in combination with the BSS is recommended.

Analysis of fuel storage tanks under internal deflagrations with different venting technologies: an experimental and numerical study

This study investigates small-scale fuel storage tanks subjected to internal methane-air explosions, focusing on three depressurization technologies using roof ventilation to mitigate overpressure and damage. Tests with low methane-air concentrations were conducted to generate a pseudo-static internal pressure. This approach minimized scale effects and aligned internal pressure frequency with real-scale tank behavior during deflagrations. The first prototype features a tank with a frangible roof activated by localized brittle failure of stitch welds around the roof-to-shell junction. This confirms that stitched weld patterns ensure controlled brittle failure with activation pressure estimated by a simplified equation. The second technology employs a sequential ventilation strategy, starting with a small hinged panel followed by stitch weld failure, managing low to medium-intensity explosions with the small vent alone, and allowing rapid operational recovery. In severe explosions, the hinged door facilitates earlier activation of the frangible roof, reducing the initial pressure rise rate and controlling the roof opening direction. Lastly, the study explores tanks with commercial explosion vent panels as an alternative to traditional frangible roofs, offering a practical solution for retrofitting existing tanks. Each technology enhances safety in fuel storage facilities by effectively managing internal pressures during explosive events.

EVALUATION OF TECHNOLOGICAL PLASTICITY OF HIGH BORON CORROSION-RESISTANT STEEL DURING HOT DEFORMATION OF PIPES USED FOR SPENT NUCLEAR FUEL STORAGE

Statement of the problem. The sustainable development of the global nuclear power industry in the future depends on how effectively the problems of radiation safety and nuclear proliferation are addressed. Such problems occur, among other things, at the final stage of the nuclear fuel cycle – spent fuel management. This task is currently on the agenda of both the international community and national governments of countries that develop or intend to develop nuclear energy [1−3]. Today, in connection with ensuring the safety of nuclear energy, boron-containing steels are widely used in the world practice as a material for biological protection and for the manufacture of special equipment parts. This is due to the fact that the B10 isotope in steels provides neutron capture [4]. Hexagonal pipes made of high-boron steel were needed to shield the support cover of the compacted spent fuel storage facility at nuclear power plants. Corrosion-resistant steels alloyed with boron are widely used in the nuclear power industry due to their special nuclear properties. During the operation of nuclear power plants, fuel assemblies that have served their useful life must be stored in special storage facilities using containers – hexagonal tubes made of 04Сr14Ti3B2V steel. To reduce costs during in the construction and operation of NPPs, part of the spent nuclear fuel management should be performed at Ukrainian enterprises. This will provide a significant import substitution effect. To manufacture hexagonal tubes from 04Сr14Ti3B2V steel according to the ingot-hot deformation-profiling-heat treatment scheme, it is necessary to develop the parameters of hot deformation and subsequent technological operations. The use of these pipes in compacted spent fuel storage facilities of NPPs will allow to increase the storage capacity by 2 times, which will give a significant national economic effect Material and methods of research. Material used for the study was steel 04Сr14Ti3B2V (CS-82), smelted using two variants (vacuum-induction – “VI” and vacuum-induction followed by vacuum-arc remelting – (“VD”). Steel grade 04Сr14Ti3B2V belongs to high-alloy, corrosion-resistant ferritic steels with a high boron content of up to 2 %. The method of differential thermal analysis was used to study the phase transformation temperatures in the steel. X-ray diffraction and micro-X-ray spectral analysis were used to assess the phase state. The steel samples were tested for weldability After cooling, the welded samples were subjected to X-ray transmission [5]. Hot twisting tests and mechanical tests at high temperatures were also performed. The macro- and microstructure of the metal was studied. Results. The macro- and microstructure of steel was evaluated depending on the smelting method. The phase composition of the steel was studied. The study of the plastic properties of steel ChS-82 by means of penetration and hot twisting tests showed that the temperature range of maximum plasticity is in a wide range (from 1 025 to 1 150 0C) with a rather low resistance to deformation. During hot deformation in the temperature range of 1 175 0C and above, metal fracture was observed along the grain boundaries at the melting points of the Cr−Fe−B boride phase. The optimal temperature range for hot deformation of steel ChS-82 is 1 000−1 050 ⁰С. Scientific novelty. For corrosion-resistant high boron steel used for spent nuclear fuel storage, the temperature range of hot deformation was selected and the structural and phase composition was estimated, which will allow deforming the metal on the piercing mill and manufacturing pipes.

Advancing real-time fuel classification with novel multi-scale and multi-level MHOG and light gradient boosting machine

Accurately classifying petrol and diesel fuel using an image processing method is crucial for fuel-related industries such as petrol pumps, refineries, and fuel storage facilities. However, distinguishing between these fuels using traditional methods can be challenging due to their similar visual characteristics. This article introduces a novel multi-scale and multi-level modified histogram of oriented gradients (MHOG) feature descriptors for robust classification of fuel images. Our proposed method involves extracting distinctive features from the images using the novel multi-scale and multi-level MHOG feature descriptor. These features are then utilized to train a range of machine learning classifiers with different hyperparameter settings for an ablation study. To the best of our knowledge, this is the first ablation study for this fuel classification application. To evaluate the effectiveness of our approach, we conduct experiments on a carefully labeled dataset consisting of petrol and diesel fuel images. The results demonstrate the high accuracy of our proposed method, achieving a classification accuracy of 98% using the light gradient boosting machine (LGBM). Furthermore, our method surpasses existing state-of-the-art techniques for fuel image classification. With its superior performance, this approach holds great potential for efficient and effective fuel classification in diverse fuel-related industries.

Confirmation bias, information selection, and belief reinforcement about the safety/risk of nuclear spent fuel storage facilities

This study investigates the phenomenon of confirmation bias in information selection in the context of nuclear spent fuel (NSF) storage facilities. An online survey was administered to a sample of 321 residents in South Korea. They were asked to assess their beliefs about the safety/risk of NSF storage facilities before and after their exposure to additional information. Our findings show a positive association between the initial belief and confirmation bias, suggesting that the research participants tend to select articles consistent with their beliefs about the safety/risk of the facility. Trust in government is negatively related to confirmation bias, implying that residents with a greater level of trust in government are more likely to choose information opposing their initial beliefs. Finally, this study finds the self-reinforcing and potentially polarizing nature of individuals' beliefs about the safety/risk of NSF storage facilities as residents’ initial beliefs are reinforced rather than challenged after they reviewed self-selected articles. Implications for public policy and communication strategies related to improving the acceptance of NSF storage facilities are discussed.

Enhancing emergency response planning for natech accidents in process operations using functional resonance analysis method (FRAM): A case of fuel storage tank farm

Recent increases in climate-induced natural disasters have amplified the risk of Natech (natural hazard-triggered technological) accidents, particularly in the chemical industry. These emergencies, characterized by their urgency and resource constraints, pose significant challenges for emergency planning. The Functional Resonance Analysis Method (FRAM) offers a systematic approach to enhance emergency response strategies. This study introduces a FRAM-based methodology specifically designed for fuel storage tank farms, structured into four critical stages: understanding, designing, analyzing, and enhancing the response process. It promotes a cycle of continuous improvement. A case study on a seismic Natech incident at a fuel storage facility demonstrates the methodology's effectiveness and its potential to boost the resilience of emergency response systems against Natech challenges.

Justification of measures aimed at ensuring the required fire resistance of structures enclosing NPP premises using CFD fire modeling

Introduction. The article presents a methodological approach to justifying measures designed to ensure the required fire resistance of structures enclosing NPP premises with the use of CFD (computational fluid dynamics) fire modeling. Approaches to justifying fire safety are considered using the fuel storage facility of an NPP standby diesel power plant as an example.Aim. To develop and analyze the methodological approach to justifying measures designed to ensure the required fire resistance of structures enclosing NPP premises with the use of CFD fire modeling.Materials and methods. The purpose and application scope of various methods for modeling fire dynamics was analyzed. Fire modeling used to justify measures for ensuring the required fire resistance of enclosing structures was considered using the fuel storage facility of an NPP standby diesel power plant as an example.Results. The performed analysis of different methods for modeling fire dynamics shows the possibility of using different fire simulation methods in the analysis of the fire hazard of buildings and facilities. The most dangerous fire development scenarios were modeled and the obtained results were analyzed on the example of a specific typical NPP facility in the NPP emergency power supply system. The redundancy requirements for these systems were taken into account to ensure tolerance to system failures in case of process failures and external effects on these systems.Conclusion. Since the CFD method is the most universal of the existing deterministic methods, it can be widely used to determine/revise the requirements for fire resistance of load-bearing and enclosing structures at NPP premises. It is possible to apply CFD-based fire modeling for the fire hazard of various buildings and facilities. This model is particularly effective in justifying the sufficiency of fire resistance requirements established for structures to prevent the spread of fire beyond the fire zone within the estimated burnout time of the entire fire load The obtained regularities can be used in the development/revision of regulatory documents on fire safety at operating NPPs and NPPs under construction.

A Study on Predicting Installation Scale of Photovoltaic Panels and Hydrogen Fuel Storage Facilities to Achieve Net Zero Carbon Emissions Exploiting Idle Sites of Military Bases

In this study, the scale of renewable photovoltaic(PV) panels and hydrogen fuel storage facilities required to achieve “net zero carbon emissions” in military facilities were predicted based on actual electricity consumption. It was set up to expect the appropriate installation size of PV panel and hydrogen fuel storage facility for achieving carbon neutrality, limited to the electricity consumption in the public sector, including national defense and social security administration in Yeongcheon. The experimental results of this paper are largely composed of two parts. First, representative meteorological factors were considered to predict solar power generation in the Yeongcheon area, and solar power generation was estimated through a multiple regression model using deep learning techniques. Second, the size of solar power generation facilities and hydrogen storage facilities in military bases was estimated with the amount of solar power generation and electricity consumption. As a result of this analysis, it was calculated that a site of 155.76×104 m<sup>2</sup> for PV panels was needed and a facility capable of storing 27,657 kg of hydrogen gas was required. Through these results, it is meaningful to demonstrated the prospect that military units can lead the achievement of “carbon net zero 2050” by using PV panels and hydrogen fuel storage facilities on idle sites of military bases.

Do procedural fairness and conflict perception affect the acceptance of the temporary nuclear spent fuel storage facility? Evidence from South Korea

This study uses data collected from the residents near South Korean nuclear power plants to explore the complex psychological factors that may influence the local acceptance of the expansion of temporary nuclear spent fuel (NSF) storage facilities in South Korea. Employing structural equation modeling, we examine the roles of perceived procedural fairness and perceived local conflicts in the traditional model of trust, knowledge, and perceptions of risks and benefits. Our findings demonstrate that perceived procedural fairness significantly influences trust, which further mediates the relationship between perceived local conflicts and benefit and risk perceptions, ultimately shaping local acceptance of temporary NSF storage facilities. Our findings underscore the importance of perceived procedural fairness and trust in shaping local acceptance and highlight perceived local conflicts’ role in amplifying the perceptions of benefits and risks. These findings inform new policy implications for the local acceptance of expanding temporal NSF storage facilities.

Safety analysis of spent fuel storage facility for BAEC TRIGA research reactor using MCNP5

Safety analysis of spent fuel storage facility for BAEC TRIGA research reactor using MCNP5

A Comprehensive Review on Material Compatibility and Safety Standards for Liquid Hydrogen Cargo and Fuel Containment Systems in Marine Applications

As the maritime industry’s emphasis on sustainable fuels has increased, liquid hydrogen (LH2) has emerged as a promising alternative due to its high energy density and zero-emission characteristics. While the experience of using natural gas in ships can serve as a basis for the introduction of hydrogen, the different risks associated with the two fuels must also be considered. This review article provides a methodology for selecting suitable metal materials for shipboard LH2 storage and piping systems based on operational requirements. The effects of both liquid and gaseous hydrogen environments on metal materials are first comprehensively reviewed. The minimum requirements for metal materials in liquefied natural gas (LNG) storage systems, as stipulated in the IGC and IGF codes, were used as a baseline to establish minimum requirements for liquid hydrogen. The applicability of austenitic stainless steel, a representative metal material for cryogenic use, to a liquid hydrogen environment according to nickel content was examined. In order to apply liquid hydrogen to the marine environment, the minimum requirements for liquid hydrogen were organized based on the minimum requirements for metal materials in the LNG storage system covered by the IGC and IGF codes. Finally, to expand the material selection criteria for low-temperature cargo and fuel storage facilities at sea, slow strain tensile testing, fatigue life, and fracture toughness considering the hydrogen environment and cryogenic temperature were derived as evaluation items.

Operational Experience in Degradation (Ageing Effects) and Implementation of Ageing Management Programmes for Dry Storage Systems in Ukraine

The Coordinated Research Projects (CRPs) of International Atomic Energy Agency (IAEA) is a power tool to engage simultaneously a lot of different countries that operate Spent Fuel Storage Facilities for solving important safety issues at a deep level of competence and expertise. One of the topics that needs thorough research is behavior and state assessment of spent fuel assemblies and fuel rods during long/very long term storage in spent fuel storage facilities. It is naturally that over a long period, special attention is drawn to degradation mechanisms, ageing effects and ageing management programs that should be implemented in order to avoid and mitigate the impact of degradation mechanisms on spent fuel elements. This article describes the first step of implementing new IAEA CRP project “T13019. Performance Assessment of Storage Systems for Extended Durations (PASSED)” with contribution from the State Scientific and Technical Center for Nuclear and Radiation Safety (SSTC NRS), which conducts research regarding the “Operational experience on degradation (ageing effects) of dry storage systems” during the first stage” at the first stage. The overall objective of the research proposed by the SSTC NRS is to strengthen technical knowledge, experience and understanding of the long-term behavior of the dry spent fuel storage systems, and of the currently applied inspection and monitoring technologies. At the same time, a specific objective of involving the SSTC NRS in this project was not only to present national experience and practices, but also to study the existing experience of the participating countries, which also joined the CRP proposed by the IAEA. The article considers the existing storage systems for spent nuclear fuel at the Chornobyl and Zaporizhzhya NPP sites, provides examples of the aging management system for components and structures, as well as examples of the issues that require development, implementation and maintenance of aging management programs.

Panel: safeguarding nuclear waste management

Abstract. When the world's first encapsulation plant and geological repository (EPGR) for spent nuclear fuel disposal will start operations in Finland in a few years, this will also be the first facility of this kind for which international safeguard measures (e.g. Niemeyer et al., 2021) will be implemented. This two-part panel takes this as an opportunity to focus on the approaches, concepts, methods and technologies for safeguarding nuclear waste management. The first part discusses the current state and challenges in safeguarding spent fuel storage facilities, encapsulation plants and geological repositories and elaborates on the recent progress of safeguard developments and implementation, as well as existing gaps. Panellists will address the following questions. (i) Which safeguards approaches are currently developed for or implemented at spent fuel storage facilities, encapsulation plants and geological repositories? (ii) How do we make best use of safeguards concepts, such as safety–security–safeguards (3S) and safeguards by design (SBD), in nuclear waste management? (iii) Lastly, what are the most important research and development (R&D) activities regarding safeguards methods and technologies in nuclear waste management (related to the technical readiness levels (TRL) 4–8)? The second part then looks at future challenges of safeguarding nuclear waste management in the medium and long term and develops some priorities in order to meet these challenges, based on the following questions. (i) Which challenges are on the horizon regarding safeguards implementation at spent fuel storage facilities, encapsulation plants and geological repositories in the medium and long term? (ii) What are medium- and long-term challenges of safeguards implementation from the operator's point of view? (iii) What are the most promising methods and technologies for safeguarding nuclear waste management in the medium- and long-term future (related to the technical readiness levels (TRL) 1–4)? Both parts will include panellists from safeguards inspectorates, national safeguards authorities, the nuclear industry and research entities. The panel will be held with the Final Disposal Working Group of the European Safeguards Research and Development Association (ESARDA) (https://esarda.jrc.ec.europa.eu/working-groups/final-disposal-fd_en, last access: 24 August 2023).

Antineutrino detection concepts for safeguarding spent nuclear fuel

Abstract. Spent nuclear fuel (SNF) from nuclear power generation requires long-term safeguards in interim storage and final disposal. Current safeguarding approaches for spent fuel storage facilities (SFSFs) propose a combination of material accountancy, containment and surveillance, and design information verification. Antineutrino emissions from the ongoing beta decay of fission fragments could provide complementary information on the potential diversion of nuclear material and misuse of the facility or assist in reverification scenarios as antineutrinos pass through any shielding, structure, or geology effectively unhindered. Antineutrino-based safeguards approaches have been discussed and have been under development for nuclear reactor sites for several years. In this relatively recent field of applied antineutrino monitoring, several approaches have been developed, ranging from scintillator-based technologies to large water Cherenkov detectors, each of which is suitable for different deployment scenarios. Utilising this principle for SNF is uniquely challenging, as the antineutrino flux of cooling fuel elements is several orders of magnitude lower than of an active core. In addition, the typical beta decays in SNF emit a softer antineutrinos energy spectrum, requiring large detectors sensitive to signals close to the inverse beta decay energy threshold. This study investigates a range of current technologies that have been proposed for reactor monitoring, along with a novel antineutrino detection concept using a liquid organic (LOr) time projection chamber (TPC). The LOr-TPC concept combines the scalability and high-resolution particle reconstruction of TPCs with the large quantity of target hydrogen atoms provided by organic compounds. The expected signal rate, sensitivity to inventory changes, and directional capabilities of all technologies are estimated and compared against each other for two simplified storage sites, namely one based on an interim storage facility and one based on a geological repository. For each simplified site, varying fuel ages, cask distributions, and detector deployment scenarios are investigated. This comparison will be used to determine the feasibility and potential of antineutrino monitoring as a complementary safeguards tool for SNF storage sites.

The information system concept for thermal monitoring of a spent nuclear fuel storage container

The paper notes that the most common way of handling spent nuclear fuel (SNF) of power reactors is its temporary long-term dry storage. At the same time, the operation of the dry spent fuel storage facilities almost never use the modern capabilities of information systems in safety control and collecting information for the next studies under implementation of aging management programs. The author proposes a structure of an information system that can be implemented in a dry spent fuel storage facility with ventilated storage containers. To control the thermal component of spent fuel storage safety, a database structure has been developed, which contains 5 tables. An algorithm for monitoring the thermal state of spent fuel was created for the proposed information system, which is based on the comparison of measured and forecast values of the safety criterion, in which the level of heating the ventilation air temperature was chosen. Predictive values of the safety criterion are obtained on the basis of previously published studies. The proposed algorithm is an implementation of the information function of the system. The proposed information system can be used for effective thermal monitoring and collecting information for the next studies under the implementation of aging management programs for spent fuel storage equipment, permanent control of spent fuel storage safety, staff training, etc.

Risk assessment and numerical analysis of short-term accident scenarios in a nuclear fuel storage vault

Analysis of various accident scenarios is vital for the safety assessment of nuclear fuel storage facilities. The accidents in the storage vault due to loss of cooling are generally considered highly uncertain since the accident progression is slow (in comparison to reactors) and allows time for remedial activities to the operator. In the present work, numerical simulations of different accident scenarios have been carried out for a short duration to understand the situation better. Thermal aspects of accident conditions such as failure of the suction blower, drying of cooling water at the chiller, and combined effect of both accidents were investigated. The airflow inside the ventilated enclosures due to the failure of the blower and the rise in inlet air temperature is analyzed numerically. The temperature distributions inside the vault and the rise in temperature of the sub-assemblies and magazines have been studied. The key mechanisms of heat transfer, which take part in nuclear fuel storage vault for post-accident conditions, were identified. The study will be helpful to classify various accident conditions based on their thermal implications and the model developed can be used to design passive cooling systems.

ASSESSMENT OF ENVIRONMENTAL RISKS AND ECONOMIC LOSSES TO GEOLOGICAL ENVIRONMENT AND MINERAL RESOURCES CAUSED BY RUSSIA’S MILITARY AGGRESSION AGAINST UKRAINE. UPDATED DATA

Beyond the enormous losses of priceless human lives, extreme economic losses, tremendous impacts on our country’s geological environment have been caused by russia’s military aggression since 2014. In particular, as a result of hostilities and missile attacks, the entire network of large metallurgical and chemical facilities have been completely destroyed, nearly a hundred of oil depots and other fuel storage facilities throughout the country have been damaged, resulting in the contamination of soil, surface and groundwater, vegetation, etc. A number of hydrotechnical facilities were damaged, leading to large-scale flooding, etc. Shelling damaged a number of mining facilities, mineral deposits and other geological sites, such as unique stratotypic cross-sections, geological landmarks, and landscape parks. The objective of this paper is to provide an assessment of environmental damage and economic losses to the geological environment and mineral resource base of the country based on updated satellite monitoring data using remote sensing. Based on the analysis of the map of operating deposits and the updated map of hostilities (impact of shells, missiles, etc.), it was found that as of 13.04.2023, out of 2,164 total mineral deposits in Ukraine (excluding water resources), only 490 deposits (22.6%) are located in the temporarily occupied territories or within 25 km of the frontline. According to the results of the assessments, the following deposits are located in the territories not controlled by Ukraine: 139 hydrocarbon deposits (24%); 175 coal deposits (81%); 67 non-metallic mineral deposits (5.3%); 5 metallic mineral deposits (7%). Thus, the use of geological environment monitoring and remote sensing using GIS tools (in the conditions of lack of access to such objects) plays a key role in obtaining reliable and internationally acceptable data as proof for financial compensation. In this regard, there is a critical need for immediate actions in order to revitalise and reform the geological monitoring system in Ukraine.

Intermittent flame lengths of buoyant jet flames in reduced and normal pressures: Experiments and theoretical analysis

Quantifying the intermittent flame length scale of buoyant jets is valuable for the understanding of the physical mechanisms of flame stabilization, risk assessment of fuel leakage fire in storage facilities, as well as the practical design of effective industrial burners. In this work, experimental studies are conducted to study the intermittent flame lengths in both reduced (0.64 atm) and normal (1.0 atm) pressures. The intermittent flame lengths are quantified by flame probability contours of propane flame using five nozzles with different diameters ranging from 4 to 10 mm with different heat release rates ranging from 4.31 kW to 49.52 kW. The intermittent flame lengths are found to be positively related to the heat release rate Q˙ and nozzle diameter d. Besides, results show that lower ambient pressure can bring about significantly higher intermittent flame lengths as compared with the results obtained in normal pressure. Moreover, based on physical analysis of the flow character of unburned fuel pressure dependence of flame length scale, a general model coupling with Froude number and nozzle diameter (d) and pressure effect (P∞/1.0atm)2/3 is established as Δlf/d(P∞/1.0atm)2/3=C1Frm−0.4(2−C2Frm−0.6) for the quantification of the intermittent flame lengths in both pressures. And the correlating results show that all the data in both pressures and those from previous literature can be well normalized with a satisfactory agreement. The current work can provide some supplemental knowledge on flame instability in the reduced pressure environment, a scientific evaluation model of fire length scale in fire safety strategies in fuel storage facility leakage cases, and good data reference for CFD validation.

Investigating the interactions between hydrotalcite and U(IV) nanoparticulates

In the UK, the decommissioning of legacy spent fuel storage facilities at the Sellafield nuclear facility requires the retrieval of radioactive sludge resulting from Magnox fuel corrosion. However, sludge retrievals may enhance uranium mobility including via sorption of radionuclide nanoparticles onto colloidal phases such as hydrotalcite (Mg4Al2(OH)16(CO3).4H2O). Hydrotalcite is a Mg-Al layered double hydroxide (LDH) which is a corrosion product of Magnox fuel cladding. Currently, there are a paucity of studies examining interactions between actinide nanoparticles and LDH phases such as hydrotalcite. Here, a multi-technique approach was used to investigate the interactions between colloidal hydrotalcite and three different forms of nanoparticulate U(IV): nanoparticulate uraninite (UO2); nanoparticulate UO2 reacted with silica (UO2-Si); and U(IV)-Si-coprecipitate under anoxic, neutral-to-alkaline conditions. Ultrafiltration and zeta potential analyses indicated that for UO2 and UO2-Si nanoparticulate phases, sorption to colloidal hydrotalcite was limited due to rapidly settling UO2 and UO2-Si aggregates (>450 nm). By contrast, ultrafiltration and zeta potential analyses confirmed the U(IV)-Si-coprecipitate nanoparticle phase showed significantly higher sorption to colloidal hydrotalcite. This was due to the increased colloidal stability of intrinsic U(IV)-silicate nanoparticles which in turn promoted increased sorption to hydrotalcite. TEM imaging showed some evidence for smaller UO2 and UO2-Si aggregates (<20 nm) sorbed to colloidal hydrotalcite. Similar behaviour was observed in TEM images of authentic pond effluent samples from Sellafield, providing confidence that the model laboratory experiments provided a bridge to the highly radioactive spent nuclear fuel pond interactions. This study highlights the potential for U(IV) nanoparticles to form a new type of colloid-colloid interaction with hydrotalcite, especially when silica is present. This further informs predictions of U(IV) (and An(IV)) behaviour in the legacy pond and silo environments, as well as in environmental scenarios where LDH mineral phases and silica are present (e.g. in geological disposal of radioactive waste).

Performance of cooling system of a fast reactor sub-assembly storage facility during station blackout

In this work, using a specifically developed CFD model, design of a cooling system for an upcoming fresh fuel storage facility with 22 kW of decay heat generation and its availability have been optimized in the event of equipment failure and station blackout. Parameters such as air temperature, concrete temperature, velocity of air and time taken by air to escape from the storage have been used to compare the performances of various designs of the cooling system. From the analysis of a pre-designed system without any backup equipment, it is observed that in absence of suction blower, contaminated air escapes through the upper inlets after 100 s. With an intention to stop this escape of contaminated air, we analyzed two upgraded designs; one with the backup equipment and another with relocated upper inlets. The results show that with backup equipment, -which starts within 100 s, the temperatures of the fuel sub-assemblies and concrete are maintained within the safe limit. With the relocation of upper inlets, the contaminated air remains in the storage vault, but the temperature of the air in the vicinity of the concrete ceiling reaches the safety limit of 338 K in 500 s. Hence, we suggest a safe limit of 400 s for starting up the backup system. The modification in inlet positions and integration of backup equipment for cooling of the nuclear inventories during station blackout prevents release of contaminated air and retains the temperature within safe limits.