Hazardous Nuclear Waste Research Articles

Colloidal silica as a grouting material for the temporary encapsulation of heat-generating radioactive waste during removal and transport operations: A proof of concept

Hazardous nuclear waste is produced at all stages during the nuclear fuel cycle. The removal operations of nuclear waste from nuclear reactors and/or storage facilities, such as spent fuel pools and storage silos, pose a hazard for the workforce and the environment, due to the potential release of radioactive particulates, and loss of radioactive debris. The development of innovative techniques to address this issue is desirable. A potential technology to inhibit particulate release during nuclear waste removal and transport operations is colloidal silica grouting. Colloidal silica is an aqueous suspension of silica (SiO2) nanoparticles, able to provide immobilisation of particulates within a hydrogel matrix. In this study, an experimental investigation was carried out to simulate colloidal silica grouting operations around objects at temperatures of 60°C and 120°C, to simulate radioactive waste in standard storage conditions, and during loss of cooling/loss of coolant accident scenarios. The results of the experimental campaign confirm the suitability of colloidal silica to safely remove and transport heat-generating radioactive waste. Critical parameters for designing the silica grout mix, in order to optimise the performance of the hydrogel upon exposure to temperature in different scenarios, are identified and discussed.

Machine Learning Tools for Fossil and Geothermal Energy Production and Carbon Geo-sequestration—a Step Towards Energy Digitization and Geoscientific Digitalization

Eighty percent of current world energy consumption is satisfied by subsurface resources. In future, billions of watts of electrical power will be generated from geothermal energy sources. Subsurface earth can store the energy produced from renewable sources, such as wind and solar, and could provide safe storage of contaminants and hazardous nuclear waste. Engineering of subsurface earth is critical for fossil energy production, geothermal energy production, and carbon geo-sequestration. However, the subsurface is opaque, inaccessible, and heterogenous with nano-scale to kilo-scale processes that limits our understanding (characterization) and constrains the efficient engineering of the complex subsurface earth resources. There has been rapid increase in sensor deployment, data acquisition, data storage, and data processing for purposes of better engineering and characterizing the subsurface earth. This has promoted large-scale deployment of data-driven methods, machine learning, and data analytics workflows. Subsurface data ranges from nano-scale to kilometer-scale passive as well as active measurements. Subsurface data is acquired in the form of physical fluid/solid samples, images, 3D scans, time-series data, waveforms, and depth-based multi-modal signals, to name a few. Subsurface data sense various physical phenomena, e.g., transport, chemical, mechanical, electrical, and thermal properties. Integration of such varied data sources being acquired at varying scales, rates, resolutions, and volumes mandates robust machine learning methods to better characterize and engineer the subsurface earth. Machine learning has shown to improve the efficiency, efficacy, and productivity of subsurface engineering and characterization efforts required to produce fossil/geothermal energy and to sequester carbon dioxide.

The Cold Fusion Phenomenon – Nuclear Reactions in the CF Materials at Around Room Temperature

Since the discovery of nuclear reactions in PdDx alloys at around room temperature in 1989, there have been accumulated very many experimental data sets showing existence of nuclear reactions in solid materials composed of transition metals and occluded hydrogen isotopes (let us call them the CF materials, for short) resulting in various nuclear products such as neutrons, tritium, transmuted nuclei, and others accompanied with large excess energies at relatively low temperatures up to 1000°C (let us call these whole events the cold fusion phenomenon (CFP), for short). As the cause of these nuclear reactions in the CFP, we have to accept the existence of the interactions between nuclei in the CF material through the nuclear force (let us call this interaction the nuclear-force interaction, for short) recognized its existence in the nucleus in the nuclear physics. We can classify the CF materials, i.e. materials where CFP occurs, into three groups: (1) metallic material including transition-metal hydrides (e.g. NiHx, AuHx) and deuterides (e.g. PdDx, TiDx), (2) carbonic material including hydrogen graphite (HCx) and XLPE (cross-linked polyethylene) and (3) biological material including microorganisms, microbial cultures and biological tissues or organs. We will explain the characteristics of the CFP observed in each group in this paper. The nuclear reactions in the CF material gives rise to production of new particles from neutron, triton, and new nuclei with proton numbers Z up to 83 accompanying enormous excess energy. In addition to these events, there occurs the stabilization of unstable nuclei, including the decay-time shortening of radioactive nuclei, which is especially interesting to apply it to treat hazardous nuclear waste produced by the nuclear power plant. Finally, we give an overview of the CFP in relation to the solid state-nuclear physics and the solid state-nuclear chemistry where the nuclear-force interaction may play important roles to explain the riddles found but not given appropriate explanations in these old sciences hitherto.

Consistency and shielding efficiency of cement-bitumen composite for use as gamma-radiation shielding material

At radioactive waste disposal facilities all around the world, radiation shielding is required to reduce the background γ-radiation as much as possible in order to achieve protection against high radiation. In the current study, an inexpensive material, Portland cement, has been utilized as shielding material against γ-radiation from radioactive materials including radioactive wastes. Portland cement was used as principal compound and mixed with various ratios of bitumen (0, 10, 20, 30%). Three parameters (compressive strength, permeability and attenuation coefficient) were monitored to estimate the mechanical, physical stability and isolation performance of cement-bitumen as novel γ-radiation shielding material. These parameters were studied under several variable conditions, and results were supported by spectroscopic and scanning investigations. The results confirmed that the cement-bitumen composite (with 10% bitumen) has a high attenuation coefficient comated to the measured for the pure cement paste. Although the compressive strength has decreased gradually with increasing the amount of bitumen relative to cement, the porosity and water absorption capacity have increased gradually at higher bitumen ratio, and consequently the shielding performance outperformed the control sample. As major outcome, this novel composite material could be safely applied in encapsulating or disposing hazardous nuclear waste generated by non-military applications (nuclear power plants) for efficient shielding of the environment from precarious γ-radiation.

The Cold Fusion Phenomenon – Nuclear Reactions in the CF Materials at Around Room Temperature

Since the discovery of nuclear reactions in PdD_x alloys at around room temperature in 1989, there have been accumulated very many experimental data sets showing existence of nuclear reactions in solid materials composed of transition metals and occluded hydrogen isotopes (let us call them the <i>CF materials</i>, for short) resulting in various nuclear products such as neutrons, tritium, transmuted nuclei, and others accompanied with large excess energies at relatively low temperatures up to 1000°C (let us call these whole events the <i>cold fusion phenomenon</i> (<I>CFP</I>), for short). As the cause of these nuclear reactions in the CFP, we have to accept the existence of the interactions between nuclei in the CF material through the nuclear force<i> </i>(let us call this interaction the<i> nuclear-force interaction,</i> for short) recognized its existence in the nucleus in the nuclear physics. We can classify the CF materials, i.e. materials where CFP occurs, into three groups: (1) metallic material including transition-metal hydrides (e.g. NiH_x, AuH_x) and deuterides (e.g. PdD_x, TiD_x), (2) carbonic material including hydrogen graphite (HC_x) and XLPE (cross-linked polyethylene) and (3) biological material including microorganisms, microbial cultures and biological tissues or organs. We will explain the characteristics of the CFP observed in each group in this paper. The nuclear reactions in the CF material gives rise to production of new particles from neutron, triton, and new nuclei with proton numbers <I>Z</I> up to 83 accompanying enormous excess energy. In addition to these events, there occurs the stabilization of unstable nuclei, including the decay-time shortening of radioactive nuclei, which is especially interesting to apply it to treat hazardous nuclear waste produced by the nuclear power plant. Finally, we give an overview of the CFP in relation to the solid state-nuclear physics and the solid state-nuclear chemistry where the nuclear-force interaction may play important roles to explain the riddles found but not given appropriate explanations in these old sciences hitherto.

Radiation Tolerance Testing Methodology of Robotic Manipulator Prior to Nuclear Waste Handling.

Dramatic cost savings, safety improvements and accelerated nuclear decommissioning are all possible through the application of robotic solutions. Remotely-controlled systems with modern sensing capabilities, actuators and cutting tools have the potential for use in extremely hazardous environments, but operation in facilities used for handling radioactive material presents complex challenges for electronic components. We present a methodology and results obtained from testing in a radiation cell in which we demonstrate the operation of a robotic arm controlled using modern electronics exposed at 10 Gy/h to simulate radioactive conditions in the most hazardous nuclear waste handling facilities.

Nuclear Transmutations and Stabilization of Unstable Nuclei in the Cold Fusion Phenomenon∗

We summarize the nuclear transmutations observed in the cold fusion phenomenon (CFP) putting a weight on the biotransmutation, i.e. nuclear transmutations in biological systems. The CF materials, i.e. materials where occurs the CFP, are classified into three groups: (1) the metallic material includes transition-metal hydrides (e.g. NiHx, AuHx) and deuterides (e.g. PdDx, TiDx), (2) the carbonic material includes hydrogen graphite (HCx) and cross-linked polyethylene (XLPE) and (3) the biological material includes microorganisms, microbial cultures and biological tissues or organs. We explain these characteristics briefly in this paper. The stabilization of unstable nuclei, including the decay-time shortening of radioactive nuclei, in the nuclear transmutation is especially interesting from the applicatory point of view in relation to the treatment of the hazardous nuclear waste accompanied to the nuclear power plant. A characteristic of biological systems where occurs selective adsorption of specific ions seems especially useful for the application. If we have a microorganism or microbial culture absorbing an ion of a radioactive element selectively, we can remediate the radioactivity by the biotransmutation.

Special Issue on Hazardous Nuclear Waste Disposal

Special Issue on Hazardous Nuclear Waste Disposal

Burnup extension of the Fixed Bed Nuclear Reactor using alternative fuels

Time evolution of criticality and burn up grades of the Fixed Bed Nuclear Reactor (FBNR) are investigated using alternative fuels. Neutron transport calculations are performed by using XSDRNPM/SCALE 5 codes. Firstly, the calculations were performed to search the optimum compositions of UO2/Reactor grade-PuO2; UO2/weapon grade-PuO2 and of UO2/MAO2 that would result in the similar initial value of keff as that of UO2, the original fuel of FBNR. Fuel component has been varied from 1% to 100%. The fuel compositions have been obtained with UO2: ① 35% RG-Pu O2; ② 19% WG-Pu O2; ③ 50% MAO2. After that, keff, burnup and operation time values of the fuels were compared. The temporal variation of the criticality keff and the burn-up values of the reactor have been calculated by full power operation for a period of 18years. The criticality in compositions of Reactor grade-PuO2/UO2; weapon grade-PuO2/UO2 and MAO2/UO2 starts by keff=1.2742, 1.2726 and 1.2783 for the fuels compositions, respectively. These mixed fuels would allow full power reactor operation for ⩾14years and burn up grade can reach ∼104,646, ∼101,990 and ∼80,798 MWD/T, respectively. On that way, the hazardous nuclear waste product can be transmuted as well as utilized as fuel.

Laser-induced photo transmutation of 126Sn – A hazardous nuclear waste product-into short-lived nuclear medicine of 125Sn

Relativistic electrons, generated in the interaction of an ultra-intense laser pulse with plasma in front of a high-Z solid target, when passing near the nuclei of the solid target produce several MeV highly collimated Bremsstrahlung gamma beam, which can be used to induce photo-nuclear reactions. In this work the possibility of photo-induced transmutation (γn) of a nuclear waste of 126Sn with a half-life of 100,000years into 125Sn with a half-life of 9.64days was investigated for the first time. Calculations based on the available experimental data show that the Bremsstrahlung γ beam generated by irradiating a 2mm thick tantalum target as a converter with 1020Wcm-2μm2 and 10Hz table-top laser for an hour can produce 293Bq activity in a 1cm thick 126Sn sample placed directly behind it. The remarkable feature of this work is to evaluate the optimal laser intensity to produce maximum activity of 2257Bq which is 1.18×1021Wcm-2μm2. The selective excitation of nuclear resonance states are discussed by studying the rate equations and calculating the Einstein coefficient. According to our calculations, we achieve relative decay rate of 0.0025, for two possible decay channels. Our results show the most probable channel for this mechanism which has a good agreement with direct excitation process.

Below the Horizon

This article elaborates the advantages of underground nuclear parks over conventional nuclear power plant designs. Locating the reactors a few hundred feet underground in bedrock at a suitable site eliminates the need for containment structures, and the site would be largely impervious to physical attack from terrorists. (Indeed, it would be far easier to secure the few access points to an underground nuclear park than it is to protect the large perimeter of an isolated nuclear power plant.) A properly constructed underground facility would also be less subject to weather-related construction delays or the effects of hurricanes, tornadoes, flooding, or heat waves. Also, if designers were careful in the site selection, an underground nuclear park could virtually eliminate the transportation of hazardous nuclear waste material. Spent nuclear fuel could be moved via tunnel from the reactors to an array of storage tunnels; high-level waste could be permanently stored in another set of tunnels. When the reactors reach the end of their productive life, they can be decommissioned in place.

The evaluation of transmutation of hazardous nuclear waste of 90Sr, into valuable nuclear medicine of 89Sr by ultraintense lasers

AbstractThe analytical evaluation of the capability of Bremsstrahlung highly directional energetic γ-beam to induce photo transmutation of 90Sr (γ,n) 89Sr is presented. Photo transmutation of hazardous nuclear waste of 90Sr, one of the two main sources of heat and radioactivity in spent fuel into valuable nuclear medicine radioisotope of 89Sr is explained. Based on the calculations, a fairly decent fraction of gamma rays in this range are used in transmuting of 90Sr into 89Sr where according to the available experimental data it is shown that by irradiating a 1-cm thick 90Sr sample with lasers of intensity of 1021 W/cm2 and repletion rate of 100 Hz for an hour, the reaction activity would be 1.45 kBq. It is shown that there is not a linear relationship between the growth of the activity and increasing the laser intensity, but there is a dramatic increase in the growth rate especially between 1020and 1021 W/cm2. In this work, the advantage of photonuclear transmutation over the neutron capture transmutation for 90Sr isotope is also discussed.

Criticality and burn up evolutions of the Fixed Bed Nuclear Reactor with alternative fuels

Time evolution of criticality and burn-up grades of the Fixed Bed Nuclear Reactor (FBNR) are investigated for alternative fuels. These are: (1) low enriched uranium, (2) weapon grade plutonium, (3) reactor grade plutonium, and (4) minor actinides in the spent fuel of light water reactors (LWRs). The criticality calculations are conducted with SCALE 5.1 using S 8-P 3 approximation in 238 neutron energy groups with 90 groups in thermal energy region. The main results of the study can be summarized as follows: (1) Low enriched uranium (UO 2) : FBNR with an enrichment grade of 9% and 19% will start with k eff = 1.2744 and k eff = 1.36 and can operate ∼8 and >15 years with the same fuel charge, where criticality drops to k eff = 1.06 and a burn-up grade of 54 000 and >110 000 MW.D/t can be attained. (2) Weapon grade plutonium: Such a high quality nuclear fuel suggests to be mixed with thorium. Second series of criticality calculations are conducted with fuel compositions made of thoria (ThO 2) and weapon grade PuO 2, where PuO 2 component has been varied from 1% to 100%. Criticality with k eff > 1.0 is achieved by ∼2.5% PuO 2. At 4% PuO 2, the reactor criticality will become satisfactory ( k eff = 1.1121), rapidly increasing with more PuO 2. A reasonable mixture will by around 20% PuO 2 and 80% ThO 2 with a k eff = 1.2864. This mixed fuel would allow full power reactor operation for >20 years and burn-up grade can reach 136 000 MW.D/t. (3) Reactor grade plutonium: Third series of criticality calculations are conducted with fuel compositions made of thoria and reactor grade PuO 2, where PuO 2 is varied from 1% to 100%. Reactor becomes critical by ∼8% PuO 2 content. One can achieve k eff = 1.2670 by 35% PuO 2 and would allow full power reactor operation also for >20 years and burn-up grade can reach 123 000 MW.D/t. (4) Minor actinides in the spent fuel of LWRs: Fourth series of criticality calculations are conducted with fuel compositions made of thoria and MAO 2, where MAO 2 is varied from 1% to 100%. Reactor becomes critical by ∼17% MAO 2 content. Reasonably high reactor criticality ( k eff = 1.2673) is achieved by 50% MAO 2 for a reactor operation time of 15 years with a burn up of 86 000 MW.D/t without fuel change. On that way, the hazardous nuclear waste product can be transmuted as well as utilized as fuel.

Criticality investigations for the fixed bed nuclear reactor using thorium fuel mixed with plutonium or minor actinides

Prospective fuels for a new reactor type, the so called fixed bed nuclear reactor (FBNR) are investigated with respect to reactor criticality. These are ① low enriched uranium (LEU); ② weapon grade plutonium + ThO 2; ③ reactor grade plutonium + ThO 2; and ④ minor actinides in the spent fuel of light water reactors (LWRs) + ThO 2. Reactor grade plutonium and minor actinides are considered as highly radio-active and radio-toxic nuclear waste products so that one can expect that they will have negative fuel costs. The criticality calculations are conducted with SCALE5.1 using S 8–P 3 approximation in 238 neutron energy groups with 90 groups in thermal energy region. The study has shown that the reactor criticality has lower values with uranium fuel and increases passing to minor actinides, reactor grade plutonium and weapon grade plutonium. Using LEU, an enrichment grade of 9% has resulted with k eff = 1.2744. Mixed fuel with weapon grade plutonium made of 20% PuO 2 + 80% ThO 2 yields k eff = 1.2864. Whereas a mixed fuel with reactor grade plutonium made of 35% PuO 2 + 65% ThO 2 brings it to k eff = 1.267. Even the very hazardous nuclear waste of LWRs, namely minor actinides turn out to be high quality nuclear fuel due to the excellent neutron economy of FBNR. A relatively high reactor criticality of k eff = 1.2673 is achieved by 50% MAO 2 + 50% ThO 2. The hazardous actinide nuclear waste products can be transmuted and utilized as fuel in situ. A further output of the study is the possibility of using thorium as breeding material in combination with these new alternative fuels.

Plan-N-Scan: A Robotic System for Collision-Free Autonomous Exploration and Workspace Mapping

This paper presents a sensor-based robotic system, called Plan-N-Scan, for collision-free, autonomous exploration and workspace mapping, using a wrist-mounted laser range camera. This system involves gaze planning with collision-free sensor positioning in a static environment, resulting in a 3-D map suitable for real-time collision detection. This work was initially motivated by the great demand for autonomous exploration systems in the remediation of buried but leaking tanks containing hazardous nuclear waste. Plan-N-Scan uses two types of representations: a spherical model of the manipulator and a weighted voxel map of the workspace. In addition to providing efficient collision detection, the voxel map allows the incorporation of different types of spatial occupancy information. The mapping of unknown sections of the workspace is achieved by either target or volume scanning. Target scanning incorporates a powerful A*-based search, along with a viewing position selection strategy, to incrementally acquire scans of the scene and use them to capture targets, even if they are not immediately viewable by the range camera. Volume scanning is implemented as an iterative process which automatically selects scan targets, then employs the target scanning process to scan these targets and explore the selected workspace volume. The performance and reliability of the system was demonstrated through simulation and a number of experiments involving a real robot system. The ability of the Plan-N-Scan system to incrementally acquire range information and successfully scan both targets and workspace volumes was demonstrated.

Numerical Studies of Radionuclide Migration in Heterogeneous Porous Media

Burial of hazardous nuclear waste in geological repositories is considered to be in the best environmental interest. However, to minimize potential risk for future generations, an accurate knowledge is required of the time- and space-dependent concentrations of the radionuclides as they migrate from their burial site. Numerical solutions to both the conventional advection-dispersion equation and a new transport equation (containing directional dependence) are utilized to study the migration of radionuclides in heterogeneous media. In particular, layered fractured formations are examined. The new transport formulation, with its directional dependence, yields details in concentration profiles not shown by the advection-dispersion approach.