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New technologies of microelectronics are emerging to reduce the size of devices and combine them into more compact ultralow power systems. Betavoltaic power sources (BVPSs) can serve as power generators of such order. BVPSs consist of a combination of betavoltaic cells (BVCs) based on long-lived radioisotopes of beta radiation and semiconductor converters (SCs). One of the key tasks for increasing the power of BVCs is the selection of SCs that can efficiently convert the energy of beta particles into electricity. Currently, semiconductor structures with a developed surface and a high band gap are considered to be perspective SCs. In present work, arrays of titanium dioxide nanopores (TiO2 NPs) synthesized by common electrochemical anodization were chosen as a SCs. These SCs were part of BVCs based on nickel-63 with an activity of ~10 Ci/g. TiO2 NPs with an amorphous structure in the composition of BVC demonstrated low electrical parameters. To increase them, we modified TiO2 NPs by the hydrothermal method in a solution of Sr(OH)2 with a concentration of 0.05 mol/L at various times. These experiments were carried out in order to convert TiO2 (anatase) into structure-like SrTiO3. We found that the electrical parameters of the SCs increased with the duration of the modification time. The best result was obtained in the case of modification for 3 h—the BVC generated a short circuit current of 2.9 nA and open circuit voltage of 0.8 V and had a maximum power of 0.8 nW at 0.45—0.5 V. The obtained electrical parameters in combination with the miniature dimensions of the BVCs open up the potential possibility of creating a BVPS with an increased power density. [ABSTRACT FROM AUTHOR]

AbstractA nuclear battery is a promising candidate for small power supply sources in the military and commercial fields, but its output power and energy conversion efficiency need to be improved. This paper mainly describes a design, preparation, and electrical performance analysis of a GaAs-based tritium battery. The design of the tritium battery uses a multistage process with Monte Carlo and Matlab simulations. A titanium tritide source was prepared by a high-temperature tritium absorption device, and a GaAs semiconductor transducer was developed using a metal-organic chemical vapor deposition method. The D/Ti ratio and T/Ti ratio of the deuterium/tritium titanium films were 1.9 and 1.7, respectively. Two kinds of GaAs-based PIN junction semiconductor transducers were proposed and irradiated with the prepared tritium source. Their electrical properties were measured in situ and analyzed qualitatively. Under the irradiation of a 0.61-Ci tritium source, the short-circuit current of the device was 0.3 to 0.38 μA, the open-circuit voltage was 35 to 63 mV, the peak power was 2.8 to 6.4 nW, and the energy conversion efficiency of the GaAs semiconductor transducer was about 1.86%. It was found that an air gap between the GaAs semiconductor transducer and the radioactive source caused serious loss of beta particle energy, resulting in low output power and low energy conversion efficiency of the nuclear battery. The open-circuit voltage of the devices with a SiO2 passivation layer on the surface decreased both in a dark environment and in light illumination, but SiO2 passivation did not reduce surface recombination as expected. The research work in this paper will provide some valuable reference for the preparation and performance optimization of nuclear batteries. [ABSTRACT FROM AUTHOR]

A direct charge nuclear battery, or DCNB, is one of the nuclear batteries based on direct energy conversion and is characterized by exceptional high voltage generation and conversion efficiency higher than other nuclear batteries. For studying potential applications of DCNB, a preliminary estimation of DCNB electrical power and performance is required; hence, conversion efficiency analysis is crucial. For preliminary verification purposes, an ideal DCNB conversion efficiency was calculated under the simplified electron transport model by using the general-purpose Monte Carlo particle transport calculation code PHITS. The result was compared with a reference experimental efficiency for a T-loaded parallel plate DCNB, and the resulting relative error was approximately 12%. Considering the relative error of 20% or less in DCNB conversion efficiency shown by preceding studies, the resulting error was comparable, and it was concluded that the PHITS code is sufficiently applicable to DCNB conversion efficiency analysis. [ABSTRACT FROM AUTHOR]

A direct charge nuclear battery, or DCNB, is one of the nuclear batteries based on direct energy conversion and is characterized by exceptional high voltage generation and conversion efficiency higher than other nuclear batteries. For studying potential applications of DCNB, a preliminary estimation of DCNB electrical power and performance is required; hence, conversion efficiency analysis is crucial. For preliminary verification purposes, an ideal DCNB conversion efficiency was calculated under the simplified electron transport model by using the general-purpose Monte Carlo particle transport calculation code PHITS. The result was compared with a reference experimental efficiency for a T-loaded parallel plate DCNB, and the resulting relative error was approximately 12%. Considering the relative error of 20% or less in DCNB conversion efficiency shown by preceding studies, the resulting error was comparable, and it was concluded that the PHITS code is sufficiently applicable to DCNB conversion efficiency analysis.

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The performance of tritium-based nuclear batteries based on two different energy conversion modes, the irradiated voltaic effect and irradiated photovoltaic effect, was studied by using the Monte Carlo method. The influence of the geometrical-physical parameters of energy conversion materials on the electrical output performance of batteries wais investigated. Single-layer and stacked-layer tritium-based nuclear batteries were designed and prepared. The effects of increasing the tritium source intensity and adopting the stacked-layer configuration on the enhancement of the electrical output of the batteries were analyzed. The simulation results showed that Si, SiC, and GaAs photovoltaic modules could be used for irradiated voltaic effect tritium-based nuclear batteries and that their respective optimal thickness parameters allow the electrical output performance to be optimized; the optimal thicknesses were 3.8 μm, 2.2 μm, and 1.7 μm, respectively. For irradiated photovoltaic effect tritium-based nuclear batteries, the thickness of the ZnS:Cu fluorescent layer could be adjusted to maximize the emitted fluorescence irradiance and optimized the electrical output performance. The experimental results showed that increasing the radiation intensity of the tritium source and adopting the stacked-layer configuration could effectively enhance electrical parameters such as the maximum output power of tritium-based nuclear batteries. The maximum output power of the stacked-layer nuclear battery could reach 106.138 nW, which was an increase of more than 64% compared with that of the single-layer configuration.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The theoretical and experimental investigation work of an in-house produced 63Ni radioisotope-powered gallium nitride (GaN)-based direct conversion (betavoltaic) nuclear battery is described. The GaN-PIN devices with different thicknesses of depletion layer were fabricated, and the thickness of depletion layer and doping concentration of the cell were simulated and optimised. The nuclear battery was tested with 63Ni radioisotope source with different radioactivity density. The test results show that the power density of the nuclear battery can exceed 6 nW/cm2, the open-circuit voltage can reach 1.25 V and the energy conversion efficiency is 2.78%. The radioisotope's self-absorption effect is explored by Monte Carlo modelling. The series and parallel integrated forms of the two devices are successfully fabricated, and their electrical characteristics are tested. Finally, the temperature effect of nuclear cell is studied preliminarily, the output power of nuclear battery is increasing with the increase of temperature. [ABSTRACT FROM AUTHOR]

Summary: The feasibility of utilizing CdSe/ZnS quantum dots (QDs) in liquid scintillator radioluminescent nuclear batteries to improve battery performance was studied. The peak position of the radioluminescence emission spectra of liquid scintillator can be regulated by controlling the QD components. This method is suitable for obtaining a satisfactory spectral matching between fluorescence materials and photovoltaic devices to increase the output performance of the battery. In the experiment, CdSe/ZnS QDs were introduced into Emulsifier‐Safe liquid scintillator, and the output properties of radioluminescent nuclear batteries were investigated via X‐ray. Results indicate that the battery with 15 mg CdSe/ZnS QDs generated the best electric power under different tube voltages. To analyze the X‐ray radioluminescence effects of the liquid scintillator, the radioluminescence spectra of the Emulsifier‐Safe with and without CdSe/ZnS QDs were measured and compared. The spectral matching degree between the Emulsifier‐Safe with different concentrations of CdSe/ZnS QDs and the GaAs device was also analyzed by considering luminescence utilization in batteries. This framework can serve as a guide for the development of a radioluminescent material system for long‐lasting, high‐performance power supplies. [ABSTRACT FROM AUTHOR]

In this paper, a beta radioluminescent battery with different radioisotopes is studied, and different parameters of the proposed structure are optimized. These parameters include the luminescent layer thickness, the doping concentration in the semiconductor P-N junction, etc. Some of the parameters have an inverse effect on the battery outputs. So, a trade-off is sought between them to increase efficiency. Each part of the proposed structure is divided into much smaller parts in the simulations to ensure proper tracking of photons and the creation of electron holes in the semiconductor layer. Also, the passage of particles through each layer is carefully reviewed and calculated in terms of particle crossing percentage, their reflection percentage, rate of self-absorption, etc. Finally, the power, open-circuit voltage, and short-circuit current density of the proposed battery versus the main parameter changes are presented. [ABSTRACT FROM AUTHOR]

Nuclear reaction processes are used for the production of energetic 208,209,210Po nuclei from Pb and Bi targets with particle accelerators, instead of the production with a nuclear reactor, for use in the nuclear battery and radioisotope thermoelectric generator technologies. The cross-section curves, simulated activity and yields of product of each reaction process were calculated under particular conditions, including 24 h of irradiation with a particle beam current of 1 mA for the energy range Eparticle = 200 → 1 MeV. Based on the calculated and simulated results, to produce 208,209,210Po nuclei, the appropriate target nuclei, nuclear reaction processes, and energy region of reactions were discussed by comparing the obtained results with the experimental data of literature and TENDL database in detail. [ABSTRACT FROM AUTHOR]

Research done on a set of simple fluidic (with the fluid used as the ionized medium being air under atmospheric pressure) alphavoltaic cells – small ionizing reactors or "nuclear batteries", designed in the Faculty of Power and Aerospace Engineering of Warsaw University of Technology, Poland – has shown the possibility of accumulation of usable amount of electric charge. Two simple methods are proposed to describe the fluidic alphavoltaic cells in terms of their efficiency. The results of these methods are presented and compared with the efficiencies of other contemporary types of solid-body (semiconductor junction-based) alpha- and betavoltaic cells. The comparison showed that despite the far-reaching simplicity in design, the designed fluidic cells are still more efficient than some of the solid-body devices that use the alpha type of decay. [ABSTRACT FROM AUTHOR]

This review presents the current state of the knowledge regarding the use of radioactive sources to generate photonic light in scintillators as converters of ionizing radiation to electricity in photovoltaic cells. The possibility of using the phenomenon of the excitation of light photons in the scintillation materials during the interaction with particles and photons of ionizing radiation was analyzed in detail. The light photons obtained in such a way can generate an electric charge in photovoltaic cells. The whole process can be named as a nuclear cell (nuclear battery). Theoretically, the use of such physical phenomena seems to be an ideal practical solution to meet the energy needs of the modern world. However, there are many physical and technical problems that limit its widespread use in practical applications. In an ideal system, the ionizing radiation sources can emit the radiation for billions of years, and the energy of particles and photons from the radiation can be converted into photons in the scintillation material, with energy suitable to generate a photoelectric effect in a photovoltaic cell. Such a cascade sequence of different physical phenomena allows, from a theoretical point of view, for the creation of a virtually inexhaustible source of electricity. This review of historical and current literature reports aims to bring closer the idea of “energy perpetuum mobile”, which has troubled many scientists around the world for centuries.

Summary: This work describes the theoretical and experimental investigation of an in‐house produced 63Ni radioisotope‐powered GaN‐based direct conversion (betavoltaic) nuclear battery. GaN p‐n junction device with 1‐mm2 area was fabricated and irradiated by the 63Ni plate source. Short‐circuit current and open‐circuit voltage of the battery were measured, and current‐voltage curves were plotted. The energy stored in battery, maximum power, and efficiency parameters were calculated. Monte Carlo modelling was used to investigate radioisotope's self‐absorption effect, the optimization of semiconductor and source thickness, transport, and penetration of beta particles in semiconductor junction. A large fraction of beta particle energy emitted from 63Ni source is absorbed within 1 μm of the semiconductor junction on the basis of the simulation results. Epitaxial growth of GaN was performed using metal‐organic chemical vapour deposition (MOCVD) system. Monte Carlo simulation with MCNPX was used to determine optimum 63Ni radioactive film thickness. 63Ni film was electroplated on one face of 1‐mm2 copper plate and mounted 1 mm over the semiconductor device. A 63Ni source with an apparent activity of 0.31 mCi produced 0.1 ± 0.001 nA short‐circuit current (Isc), 0.65 V ± 0.0022 open‐circuit voltage (Voc), and 0.016 nW ± 0.0002 maximum power (Pmax) in the semiconductor device. The filling factor (FF) of the betavoltaic cell was 25%, and the conversion efficiency (ɳ) was 0.05%. Finally, experimental results were compared with theoretical calculations. [ABSTRACT FROM AUTHOR]

Summary: High‐quality diamond intrinsic layer was epitaxially grown on a IIb‐type boron‐doped diamond substrate. The quality of the epitaxy layer was evaluated by Raman spectroscopy and cross‐polarizer images and compared with other samples. The dark current of the diode was analyzed, revealing a rectification ratio as high as 2 × 109 at ±7 V. Current‐voltage characteristics of the converter under the irradiation of different americium‐241 activity sources were investigated. A maximum total conversion efficiency (ηtotal) of 1.41%, short‐circuit current (Isc) of 6.68 nA/cm2, and open‐circuit voltage (Voc) of 1.06 V from the diamond alpha‐voltaic battery were obtained under the irradiation of an americium‐241 source with a source activity of 8.85 μCi/cm2. The trend for the battery parameters with the increase in the activity of the americium‐241 source was clarified. Parameters Isc and Voc increase with the increase in the radioactive source activity. The ηtotal increases with the increase in the source activity but fluctuates in a certain activity interval with an increase in the fill factor, and then decreases with the increase in radioactive source activity. The research results are significant for the design of nuclear batteries. Highlights: Diamond Schottky alpha‐voltaic battery with high quality intrinsic layer was fabricated;The quality of the intrinsic layer was analyzed by Raman microscopy and cross‐polarizer images, and compared with other samples;The variation of battery parameters with the increase in radiative source activity was explained. [ABSTRACT FROM AUTHOR]

Aims of this work are: (i) Investigation of the production of some radioisotopes that could be used in nuclear battery technology with neutron-induced reaction processes, (ii) Estimation of the cross-section curves of (n , γ) reactions for astrophysical processes in the energy region between 1 eV and 1 MeV, (iii) Determination of suitable level density models for the (n , γ) reaction processes. Additionally, the obtained results were compared with the experimental data and recommended data. Based on the calculated results, to eliminate lack of nuclear data in the literature, we recommend new experiments for some reaction processes to be performed by the experimenters. Moreover, for the (n , γ) reaction processes, suitable level density models were proposed. [ABSTRACT FROM AUTHOR]

Summary: Remote, terrestrial, and space sensors require sources that have high enough power and energy densities for continuous operation for multiple decades. Conventional chemical sources have lower energy densities and lifetimes of 10 to 15 years depending on environmental conditions. Betavoltaic (βV) nuclear batteries using β‐‐emitting radioisotopes possess energy densities approximately 1000 times greater than conventional chemical sources. Their electrical power density (Pe,vol in W/cm3) in a given volume is a function of β‐‐flux surface power density Pβ−, surface interface type between radioisotope and transducer, β‐ range, and transducer thickness and conversion efficiency (ηs). Tritium is the most viable β‐‐emitting radioisotope because of its commercial availability, low biotoxicity, half‐life, and low energy, which minimizes the penetration depth and damage of transducer. To maximize Pe,vol, tritium in solid or liquid form must be used in the βV nuclear battery. A Monte Carlo source model using MCNP6 was developed to maximize the Pe,vol of a tritium‐based βV nuclear battery. First, a planar coupling configuration with different tritiated compounds (ie, titanium tritide and tritiated nitroxide) and a semiconductor transducer (4H‐SiC) with thicknesses of 1 and 100 μm were modeled. The results showed that β‐‐source efficiency (ηβ), which is the percentage of energy deposited in the transducer, decreased as the tritiated compound's mass density increased. The highest Pe,vol was dependent on a combination of characteristics: specific activity (Am in Ci/g), mass density, and 4H‐SiC layer thickness. The tritiated nitroxide with the highest Am at 2372 Ci/g produced the highest Pe,vol at 2.46 mW/cm3. Second, a 3‐D coupling configuration was modelled to increase surface interfacing between the radioisotope source and textured transducer surface. 3‐D coupling configuration increased the percentage of energy deposited into the transducer because of more surface interfacing between the transducer and source in the same volume. The tritiated nitroxide was selected as the radioisotope source coupled with five different textured surface feature types. The Pe,vol as a function of textured surface feature and gap, where the radioisotope is located, width was calculated for 1‐ and 100‐μm 4H‐SiC layer thicknesses. Results showed that ηβ increased compared with planar coupling configuration (ie, approximately 56.2% increase over planar with cylindrical hole array) except with the rectangular pillar array. Still, the rectangular pillar array produced the highest Pe,vol at 4.54 mW/cm3 with an increasing factor of 2.29 compared with the planar coupling configuration. [ABSTRACT FROM AUTHOR]

This work aimed to investigate the production of 1 5 1 Sm and 1 5 2 , 1 5 4 , 1 5 5 Eu on natural Nd and Sm targets via particle accelerator because these radionuclides have the potential for use in nuclear battery technology such as betavoltaic batteries and radioisotope thermoelectric generators. Therefore, this work estimated cross-section curves for proton, deuteron, triton, helium-3, and alpha particles induced reactions in the energy range E particle = 1 0 0 → 1 MeV. The activities and products of yield were simulated for all reaction processes under selected conditions, the particle beam current of 1 mA and the irradiation time of 24 h. Moreover, to understand the formations of 1 5 1 Sm and 1 5 2 , 1 5 4 , 1 5 5 Eu in the reaction processes, the appropriate energy region of the reactions by calculating the integral yield curves were determined. Based on the obtained results, determination of suitable targets, energy regions, and reaction processes were discussed by this work. [ABSTRACT FROM AUTHOR]

Direct charging nuclear batteries (DCNB) have the potential of being widely used to meet the special requirements in the area of aerospace and ocean. The current application of direct charging nuclear batteries is restricted by the low energy conversion efficiency, commonly less than 10%. This low efficiency is limited mainly by issues of low source efficiency and shunt factor among others, such as collection and geometry factors. Based on a numerical simulation and empirical calculations we here propose a design of DCNB by utilization of a sub-micrometer thickness radiation source to increase the source efficiency, both-side emission, and collection of decay particles to improve the collection and geometry factors, as well as impedance matching of batteries and load to improve the shunt factor, among other various optimizations. The energy conversion efficiency of DCNB with this design reaches over 20%. The successful deployment of the current design should vastly improve the energy conversion efficiency of DCNBs, and also establish a theoretical foundation for extending the scope of applications of DCNBs in the future. • A new design for DCNB with sub-micrometer thickness radiation source, both-side emission and collection. • The energy conversion efficiency of DCNB with this design may reaches over 20% in theory. • This work will establish a theoretical foundation for application of DCNBs in the future. [ABSTRACT FROM AUTHOR]

This paper discusses the use of one of the safest isotopes known isotopes, Kr-85, as a candidate fuel source for deep space missions. This isotope comes from 0.286% of fission events. There is a vast quantity of Kr-85 stored in spent fuel and it is continually being produced by nuclear reactors. In using Kr-85 with a novel Dual Cycle Conversion System (DCCS) it is feasible to boost the system efficiency from 26% to 45% over a single cycle device while only increasing the system mass by less than 1%. The Kr-85 isotope is the ideal fuel for a Photon Intermediate Direct Energy Conversion (PIDEC) system. PIDEC is an excellent choice for the top cycle in a DCCS. In the top cycle, ionization and excitation of the Kr-85:Cl gas mixture (99% Kr and 1% Cl) from beta particles creates KrCl* excimer photons which are efficiently absorbed by diamond photovoltaic cells on the walls of the pressure vessels. The benefit of using the DCCS is that Kr-85 is capable of operating at high temperatures in the primary cycle and the residual heat can then be converted into electrical power in the bottom cycle which uses a Stirling Engine. The design of the DCCS begins with a spherical pressure vessel of radius 13.7 cm with 3.7 cm thick walls and is filled with a Kr-85:Cl gas mixture. The inner wall has diamond photovoltaic cells attached to it and there is a sapphire window between the diamond photovoltaic cells and the Kr-85:Cl gas mixture which shields the photovoltaic cells from beta particles. The DCCS without a gamma ray shield has specific power of 6.49 W/kg. A removable 6 cm thick tungsten shield is used to safely limit the radiation exposure levels of personnel. A shadow shield remains in the payload to protect the radiation sensitive components in the flight package. The estimated specific power of the unoptimized system design in this paper is about 2.33 W/kg. The specific power of an optimized system should be higher. The Kr-85 isotope is relatively safe because it will disperse quickly in case of an accident and if it enters the lungs there is no significant biological half-life. [ABSTRACT FROM AUTHOR]

Summary: CsPbBr3 and CsPbBr1.5I1.5 perovskite quantum dots (QDs) are synthesized by hot‐injection with PPO (2,5‐diphenyloxazole) as a fluorescent material for radioluminescent nuclear battery. The results reveal that the fluorescence of the QD/PPO system consists of radioluminescence (4.79%‐5.35%) and photoluminescence (nearly 95%). The addition of QDs leads to more excellent optical and electrical properties of radioluminescent nuclear battery. The peak position of the radioluminescence spectra of QD/PPO can be regulated by controlling the components of QDs. This strategy is suitable for obtaining a satisfactory spectral matching factor for different photovoltaic devices to obtain outstanding output performance. Moreover, good selection of QD/PPO as a fluorescent material can significantly improve the overall output performance of the radioluminescent nuclear battery. The linear relationship between optical and electrical properties was presented. Perovskite QDs exhibit excellent application prospects for the (α, β, γ, and X‐ray sources) radioluminescent nuclear battery and X‐ray imaging technology. [ABSTRACT FROM AUTHOR]

Radiation damage is a significant concern with both alphavoltaic and betavoltaic cells because their performance degrades, especially with high-energy - (>200 keV) beta and alpha particles. Indirect excitation methods, such as the Photon Intermediate Direct Energy Conversion (PIDEC) framework, can protect the transducer from radiation. A nuclear battery using a 90 Sr beta source was constructed by the author's research group, which demonstrated the radiation resistance of a PIDEC cell driven by beta particles (PIDECβ cell). Use of alpha sources to drive nuclear batteries would appear to be much more attractive than beta sources due to higher potential power density. However, they are also subject to higher rates of radiation damage. This paper describes the successful incorporation of alpha particles into the PIDEC framework using the alpha emitter 210 Po to form a PIDECα cell. The PIDECα cell transducer was exposed to alpha particles for over one year without experiencing adverse effects from radiation damage. [ABSTRACT FROM AUTHOR]

Nuclear batteries based on silicon carbide betavoltaic cells have been studied extensively in the literature. This paper describes an analysis of design parameters, which can be applied to a variety of materials, but is specific to silicon carbide. In order to optimize the interface between a beta source and silicon carbide p-n junction, it is important to account for the specific isotope, angular distribution of the beta particles from the source, the energy distribution of the source as well as the geometrical aspects of the interface between the source and the transducer. In this work, both the angular distribution and energy distribution of the beta particles are modeled using a thin planar beta source (e.g., H-3, Ni-63, S-35, Pm-147, Sr-90, and Y-90) with GEANT4. Previous studies of betavoltaics with various source isotopes have shown that Monte Carlo based codes such as MCNPX, GEANT4 and Penelope generate similar results. GEANT4 is chosen because it has important strengths for the treatment of electron energies below one keV and it is widely available. The model demonstrates the effects of angular distribution, the maximum energy of the beta particle and energy distribution of the beta source on the betavoltaic and it is useful in determining the spatial profile of the power deposition in the cell. [ABSTRACT FROM AUTHOR]

In this paper, we intend to extend the nuclear data of , , , , , , and nuclei used in nuclear battery technology, because, these nuclei are quite important for space investigations in radioisotope thermoelectric generator (RTG) and for microelectronic technologies in betavoltaic batteries. Therefore, the nuclear structure properties of nuclei such as separation energies, neutron skin thicknesses, proton, charge and neutron density distributions as a function of radius, the root mean square (rms) proton, charge and neutron radii, binding energies per particle, have been investigated by Hartree-Fock with eight different Skyrme forces. The obtained results have been compared with the experimental data in literature and relativistic mean field theory (RMFT) results. [ABSTRACT FROM AUTHOR]

• We propose the safety assessment of a transportable, plug-and-play, heat-pipe-cooled microreactor. • We make use of an advanced safety framework that embeds STPA, modeling and simulation, and GTST-MLD. • The work provides qualitative, quantitate, and dynamic risk insights. • The safety framework makes use of the RELAP code. • We identify previously unknown threats and hazards relevant to the novel microreactor design. A safety analysis of a transportable, plug-and-play, heat-pipe-cooled microreactor – or Nuclear Battery (NB)– designed at MIT is presented. The considered design is a semi-autonomous 5 MW (thermal) high-temperature heat-pipe-cooled, yttrium-hydride moderated NB envisioned to be a transportable, flexible, affordable, and distributed low-carbon energy source. The analysis makes use of a recently proposed methodology that integrates i) System-Theoretic Accident Model and Processes (STAMP) to guide a qualitative exploration of the NB threats and hazards, ii) Modeling and Simulation (M&S) to investigate the NB dynamic behavior during accident scenarios, and iii) Goal-Tree Success-Tree Master Logic Diagram (GTST-MLD) to assess risk quantitatively. The methodology has been shown to provide systematic risk insights without the need to rely on prior operating experience, and enables a dynamic evaluation of the risk profile. Moreover, it identifies unknown threats and hazards relevant to the novel microreactor design and explores the related accident scenarios. The key findings of the safety analysis performed on the nuclear microreactor considered are the identification of vulnerabilities related to the use of yttrium hydride as the moderator, the assessment of threats and accident scenarios associated with the loss of sodium from the heat pipes, and, for such scenarios, the quantification of the grace time, i.e., the period during which human operators can intervene to avoid unacceptable consequences. [ABSTRACT FROM AUTHOR]

• We propose a novel methodology for dynamic risk assessment. • The methodology integrates STAMP, modeling and simulation, and GTST-MLD. • The methodology provides qualitative, quantitate, and dynamic risk insights. • The methodology makes use of RELAP code. • The methodology is validated considering the safety assessment of a micro-reactor. Accidents may occur as a result of complex dynamic processes in interconnected socio-technical systems. Such accidents cannot be explained solely in terms of static chains of failures. Therefore, the traditional Probabilistic Risk Assessment (PRA) framework, which stands on the consideration that accidents are caused by direct failures or chains of events, is not apt to describe the dynamic behavior of the relevant Systems, Structures and Components (SSCs) and assess the risk. This work proposes a novel framework that embeds (i) System-Theoretic Accident Model and Processes (STAMP) principles to guide a qualitative exploration of the SSC threats and hazards, (ii) Modeling and Simulation (M&S) to investigate the SSC dynamic behavior during accidental scenarios, and (iii) the Goal-Tree Success-Tree Master Logic Diagram (GTST-MLD) framework to assess risk quantitatively. The integration of STAMP, M&S and GTST-MLD allows a systematic analysis to provide risk insights, with due account to the SSC dependencies and interactions, and enables a dynamic assessment of the risk profile. The effectiveness of the proposed framework is shown by means of its application to the safety assessment of Nuclear Batteries (NBs), a unique class of nuclear micro-reactors which is gaining attention as a transportable, flexible, affordable, and distributed low-carbon power source. [ABSTRACT FROM AUTHOR]

A radioluminescent nuclear battery was fabricated and the performance was measured and calculated at temperature of 223.15–323.15 K. Experimental and theoretical results indicate that J sc minimally decreases with the increase in temperature, whereas V oc linearly decreases. P max rapidly decreases with temperature. The mechanism of temperature effect is discussed using the temperature dependency of semiconductor parameters. This study significantly guides the selection of batteries' power source under various temperature. The nuclear battery may also be used as a long-life temperature transducer. [ABSTRACT FROM AUTHOR]

Based on the theory of ADS (Accelerator Driven Subcritical reactor), a new type of nuclear battery was investigated, which was composed of a subcritical fission module and an isotope neutron source, called NBDEx (Nuclear Battery Driven by External neutron source). According to the structure of GPHS-RTG (General Purpose Heat Source Radioisotope Thermoelectric Generator), the fuel cell model and fuel assembly model of NBDEx were set up, and then their performances were analyzed with MCNP code. From these results, it was found that the power and power density of NBDEx were almost six times higher than the RTG's. For fully demonstrating the advantage of NBDEx, the analysis of its impact factors was performed with MCNP code, and its lifetime was also calculated using the Origen code. These results verified that NBDEx was more suitable for the space missions than RTG. [ABSTRACT FROM AUTHOR]

GaN PIN betavoltaic nuclear batteries are demonstrated in this work. GaN epitaxial layers were grown on 2-inch sapphire sub-strates by MOCVD, and then the GaN PIN nuclear batteries were fabricated. Current-voltage ( I-V) characteristic shows that the small leakage currents are 0.12 nA at 0 V and 1.76 nA at −10 V, respectively. With 147Pm the irradiation source, the maximum open circuit voltage and maximum short circuit current are 1.07 V and 0.554 nA, respectively. The fill factor (FF) of 24.7% for the battery was been obtained. The limited performance of the devices is mainly due to the low energy deposition in the microbatteries. Therefore, the GaN nuclear microbatteries are expected to be optimized by growing high quality GaN films, thin dead layer and so on. [ABSTRACT FROM AUTHOR]

The use of a photon intermediate direct energy conversion (PIDEC) process to develop a proof of concept of a long-lived and efficient nuclear battery powered by a radioactive beta source is discussed. Fundamentally, PIDEC is a means of matching the scale length of the range of radiation to the scale length of the transducer. The device uses a photovoltaic cell and excimer gas-based photon source, b7 this work, argon was used to produce the excimer photon source (argon excimer at 129 nm) with a pressure range firm 7 X 10-3 to 1.4 X 107 Pa (10-6 to 2100 psig). The beta source used in this study was a 90Sr source that has a daughter, 90Y, that then decays to stable 90Zr. Intermediate shielding from lead and an argon gas plenum were used to prevent damage to the photovoltaic cell. This battery, demonstrated power variations with gas pressure as expected, and no radiation damage to the photovoltaic cell was observed over a period in excess of 150 h. Such a long exposure period demonstrates the desired tolerance of the device to the direct radiation damage that would otherwise be sustained in normal semiconductor-based energy conversion systems. [ABSTRACT FROM AUTHOR]

SUMMARY Spacecraft venturing to the outer planets and beyond-or onto the planetary surface where available solar energy is reduced-benefit from the longevity and consistency of electrical and thermal energy derived from radioisotope energy sources. A review of likely mission requirements and concept studies of small electrical generating units (<10 We) reveals a potential opportunity for a unit with an electrical output of around 1 We that can also supply some heat to the spacecraft to aid thermal control: a radioisotope thermoelectric and heating unit. This power requirement cannot be achieved with current US space-qualified modular radioisotope fuel assemblies. Additionally, new European programmes consider 241Am fuel to be much more cost effective than 238Pu. Taken together, these factors provide the rationale for taking a relatively 'clean-sheet' approach to design of a radioisotope thermoelectric and heating unit fuelled with 241Am. In this paper, initial requirements and performance targets for such a unit are developed, a simple concept design and thermal model is presented and the performance and mass are estimated. The results suggest that units generating 1-2 We may achieve a specific power of around 0.7-0.9 We kg−1 without the thermal inputs to spacecraft becoming impractically large. Such units can use a bismuth telluride thermoelectric material, which is commercially applied in terrestrial applications and is therefore likely to incur lower cost and development risk than more specialised compounds. This study may form the basis of a more detailed design effort. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Monte Carlo simulations have been used for calculating the energy deposition of beta particles in the depletion region of a silicon carbide (SIC) betavoltaic cell along with the corresponding theoretical efficiencies. Three Monte Carlo codes were used in the study: GEANT4, PENELOPE, and MCNPX. These codes were used to examine the transportation of beta particles from 90Y, 90Sr, and 35S. Both the average beta energy from each source and the entire spectrum were modeled for calculating maximum theoretical energy deposition in both a spherical and slab geometry. A simulated depletion region was added in postprocessing containing the maximum energy deposited per micrometer. The calculated maximum efficiencies with the slab configuration model are approximately 1.95%, 0.30%, and 0.025% using monoenergetic average energy and 1.54%, 0.25%, and 0.019% using an energy spectrum for 35S, 90Sr, and 90Y, respectively. These efficiencies when using the spherical configuration model are 2.02%, 0.31%, and 0.023% using the monoenergetic average energy and 1.10%, 0.17%, and 0.013% using an energy spectrum for 35S, 90Sr, and 90Y, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a study on the optimization of the amount of energy deposited by alpha particles in the depletion region of a silicon carbide (SiC) alphavoltaic cell using Monte Carlo models. Three Monte Carlo codes were used in this study: SRIM/TR1M, GEANT4, and MCNPX. The models examined the transport of 5.307-MeV alpha particles emitted by 210Po. Energy deposition in a 1-µm depletion region of SiC was calculated using an isotropic alpha source for a spherical geometry using GEANT4, and a monodirectional alpha source for a slab geometry using both SRIM/TRIM and GEANT4. In addition, an isotropic point source was modeled using GEANT4 and MCNPX for a slab geometry. These geometries were optimized for the maximum possible alpha-voltaic energy efficiency. The models, which match very well indicate that the maximum theoretical energy conversion efficiency, which was optimized for a SiC alpha-voltaic cell, is ~3.6% for the isotropic alpha source on a slab geometry and 2.1% for both the monodirectional alpha source on a slab geometry and the isotropic alpha source at the center of a sphere. This study provides a useful guide governing the upper limit of expected efficiency for an alphavoltaic cell using a linearly graded single junction SiC transducer. [ABSTRACT FROM AUTHOR]

Long-lived and high-energy-density betavoltaics have a great potential as power supplies for remote and hostile environmental conditions, where volume power density and/or power lifetime are very important considerations. In this paper, we provide new results to aid in the design and optimization of betavoltaics made with Si space solar cells and beta sources. The new results were obtained by using a customized low-energy electron accelerator to characterize the radiation-hardened high-efficiency Si space solar cells while varying the electron beam energy and electron beam current density, i.e., electron beam flux. The betavoltaic conversion efficiency of Si space solar cells increases until 60 keV and then decreases with the increasing electron beam energy. The maximum efficiency (6%) obtained at the electron beam energy of 60 keV suggests that Pm-147 would be a good beta source to make high-efficiency nuclear batteries. The radiation ionization energy is \sim3.90 eV per electron–hole pair for Si space solar cells. Some radiation damage-induced performance degradation was also observed when the Si space solar cells were exposed to the bombardment of 62-keV electrons with fluence up to \4.92 \times \10^18\ \betas/cm^2, which is equivalent to the radiation from a semi-infinite Pm-147 layer for \sim2.26 years. The results in this paper suggest that beta-particle entrance window, betavoltaic cells' configuration structure, and device properties such as charge carriers' diffusion length are very important factors to be engineered to improve the conversion efficiency for practical betavoltaics [ABSTRACT FROM PUBLISHER]

The paper describes a micronuclear battery that utilizes the conversion of beta particles into photons and back into electrons through a photoelectric cell to potentially deliver a nuclear battery of higher efficiency than other nuclear battery concepts and with much greater energy per gram and lifetime than chemical batteries. The Monte Carlo nuclear code MCNP has been used to analyze the performance of the proposed battery, and the photoelectric stage has been shown to be insensitive to the expected radiation for at least 1 yr of performance. [ABSTRACT FROM AUTHOR]

Abstract: Gallium Nitride (GaN) Schottky betavoltaic nuclear batteries (GNBB) are demonstrated in our work for the first time. GaN films are grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD), and then GaN Schottky diodes are fabricated by normal micro-fabrication process. Nickel with mass number of 63 (63Ni), which emits β particles, is loaded on the GaN Schottky diodes to achieve GNBB. X-ray diffraction (XRD) and photoluminescence (PL) are carried out to investigate the crystal quality for the GaN films as grown. Current–voltage (I–V) characteristics shows that the GaN Schottky diodes are not jet broken down at −200V due to consummate fabrication processes, and the open circuit voltage of the GNBB is 0.1V and the short circuit current density is 1.2nAcm−2. The limited performance of the GNBB is due to thin effective energy deposition layer, which is only 206nm to absorb very small partial energy of the β particles because of the relatively high dislocation density and carrier concentration. However, the conversion efficiency of 0.32% and charge collection efficiency (CCE) of 29% for the GNBB have been obtained. Therefore, the output power of the GNBB are expected to greatly increase with growing high quality thick GaN films. [ABSTRACT FROM AUTHOR]

Electronic medical devices have become an indispensable part of modern healthcare. Currently, a wide variety of electronic medical devices are being used to monitor physiological parameters of the body, perform therapy and supplement or even entirely replace complex biological functions. Cardiac pacemakers, cardioverter-defibrillators and cochlear implants are a few examples of such medical devices. Proper functionality of these devices relies heavily on the continuous supply of a sufficient amount of electricity to them. In this sense, a reliable, safe and convenient method for the provision of energy is very crucial. Various approaches have been developed to fulfil the divergent and challenging energy requirements of medical devices. In this article, we present a brief overview of the energy requirements of medical devices and review the existing and emerging energy sources for application in these devices, particularly wearable and implantable devices. INSET: Key issues. [ABSTRACT FROM AUTHOR]

The diode junction nuclear battery is a long-lived, high-energy-density, but low electrical current power source with many specialized applications. In this type of battery, nuclear radiation is directly converted to electric power. A model is described and used to design the device configuration. Details of fabrication and testing of a planar geometry battery with 63Ni radiation source are described. The electron beam induced current (EBIC) measurement technique and CASINO Monte Carlo simulation code were employed to analyze the device performance. Finally, an improved design with 3-dimensional surface microstructures that will provide improved performance is presented. [ABSTRACT FROM AUTHOR]

Abstract: A micro-battery powered by tritium is being developed to utilize tritium produced from the Wolsong Tritium Removal Facility. The 3D p–n junction device has been designed and fabricated for energy conversion. Titanium tritide is adopted to increase tritium density and safety. Sub micron films or nano-powders of titanium tritide is applied on silicon semiconductor device to reduce the self absorption of beta rays. Until now protium has been used instead of tritium for safety. Hydrogen was absorbed up to atomic ratio of ∼1.3 and ∼1.7 in titanium powders and films, respectively. [Copyright &y& Elsevier]

Abstract: Beta particle surface fluxes for tritium, Ni-63, Pm-147, and Sr-90 sources were calculated in this work. High current density was experimentally achieved from Pm-147 oxide in silica–titana glass. A 96GBq (2.6Ci) Pm-147 4π-source with flux efficiency greater than 50% was used for constructing a direct charge capacitor with a polyimide coated collector and vacuum as electrical insulation. The capacitor connected to high resistance (TΩ) loads produced up to 35kV. Overall conversion efficiency was over 10% (on optimal load). [Copyright &y& Elsevier]

Abstract: A number of approaches were explored for improving characteristics of the encapsulated nuclear heat source (ENHS) reactor and its fuel cycle, including: increasing the ENHS module power, power density and the specific power, making the core design insensitive to the actinides composition variation with number of fuel recycling and reducing the positive void coefficient of reactivity. Design innovations examined for power increase include intermediate heat exchanger (IHX) design optimization, riser diameter optimization, introducing a flow partition inside the riser, increasing the cooling time of the LWR discharged TRU, increasing the minor actinides'' concentration in the loaded fuel and split-enrichment for power flattening. Another design innovation described utilizes a unique synergism between the use of MA and the design of reduced power ENHS cores. Also described is a radically different ENHS reactor concept that has a solid core from which heat pipes transport the fission power to a coolant circulating around the reflector. Promising features of this design concept include enhanced decay heat removal capability; no positive void reactivity coefficient; no direct contact between the fuel clad and the coolant; a core that is more robust for transportation; higher coolant temperature potentially offering higher energy conversion efficiency and hydrogen production capability. [Copyright &y& Elsevier]

Fast reactors cooled by lead or lead-bismuth alloy offer new interesting fuel cycle and fuel management options by virtue of the superb neutronics and safety features of these heavy liquid metal (HLM) coolants. One option is once-for-life cores having relatively low power density. These cores are fueled in the factory; there is no refueling or fuel shuffling on site. A second option is very long-life cores being made of a fissioning zone and a natural uranium blanket zone. The fissioning zone very slowly drifts toward the blanket. A third option is multirecycling of light water reactor (LWR) discharged fuel without partitioning of transuranics (TRUs) in fuel-self-sustaining reactors. LWR spent fuel could provide the initial fuel loading after extracting fission products and ∼90% of its uranium. The makeup fuel is natural or depleted uranium. A fourth option is the high-burnup once-through fuel cycle using natural or depleted uranium feed. The initial fuel loading of this reactor is a mixture of enriched and natural uranium. The natural uranium utilization is 10 to 20 times higher than that of a once-through LWR. A fifth option is transmutation of TRUs from LWRs using critical HLM-cooled reactors; such reactors could be designed to have the same high actinide burning capability of accelerator-driven systems and have comparable safety, but at a substantially lower cost. These novel reactor designs and fuel management options are hereby reviewed. [ABSTRACT FROM AUTHOR]