Zero Power Research Articles

Verification and Validation of the VANGARD Pinwise Nodal Code with Analyses of BEAVRS

This paper validates the graphical processing unit (GPU)–based pinwise nodal core calculation code VANGARD using the Benchmark for Evaluation And Validation of Reactor Simulations (BEAVRS), focusing on hot-zero-power (HZP) physics tests, hot-full-power (HFP) depletion, and load follow operation for both Cycles 1 and 2. Results are compared with measured data and other high-fidelity numerical solutions. In HZP physics tests, the critical boron concentration (CBC), control rod bank worth, and isothermal temperature coefficient agree well with measured data, satisfying the design review criteria for typical zero power physics tests. Pin power distributions for various rodded cases confirm the high accuracy of pin-resolved solutions compared to other numerical results. For HFP depletion, CBC closely matches measured data and other high-fidelity numerical solutions, showing differences smaller than 35 and 10 ppm, respectively, throughout the whole depletion steps. Computational performance analysis reveals that a cycle depletion of a realistic pressurized water reactor core can be completed within 3.5 min using a single gaming GPU, which affirms the feasibility of practical pinwise core designs.

Neutronics design of shutdown and control systems for a Zero Power Experiments of chloride-based molten salt fast reactor.

Nuclear power's role as a reliable, baseload, low-carbon source and its importance in achieving clean energy goals are being increasingly recognized with growing urgency around decarbonization of the global energy systems. However, to deliver a long-term sustainable solution, it is essential to develop innovative nuclear technologies for improving the fuel utilization and reducing the nuclear waste disposal challenge. Zero Power Reactors (ZPR) are an essential initial step for developing new nuclear technologies because they allow for testing and refinement in a safe environment before large-scale deployment. This paper discusses the design of a ZPR experiments for the development of iMAGINE, a novel chloride-based molten salt reactor technology. The paper presents a detailed analysis of the neutronic design for the shutdown and control systems of an experimental ZPR based on the iMAGINE molten salt reactor technology. The study concludes that a split-core design with a lower corner reflector as an extension of the lower annular reflector offers the most robust ZPR configuration, offering optimum operational margins and maneuverability. This design ensures safety, regulatory compliance, and sufficient control and shutdown performance for the successful development of the iMAGINE technology.

Application of the PSI cycle check-up methodology for full-core Monte Carlo simulations verified using pin power estimates and validated for hot zero power conditions

Monte Carlo (MC) based neutron transport codes provide high-fidelity numerical solutions to problems beyond the modelling capabilities of conventional core simulation methods. However, performing core-follow calculations with MC codes remains challenging due to the necessity of incorporating thermal-hydraulic feedback and generating evolved fuel composition for the cycle of interest by taking into account the entire irradiation history of loaded fuel assemblies over previous cycles. Nevertheless, at PSI, the neutronic version of a cycle check-up methodology (CHUP) is under development to address this challenge. This methodology involves extracting operating conditions and nuclide compositions from validated reference deterministic core-follow models (CASMO5/SIMULATE5/SNF), subsequently generating MC neutron transport models for selected operating points. This article presents the verification and validation performed for a hot zero power operating condition of a Swiss pressurised water reactor using the updated CHUP methodology, which automates information extraction from reference core models to minimise human intervention. The MC models were verified by assessing their deviation from criticality, consistently found to be supercritical within the [10,60] pcm range. Additionally, radial relative power distribution verification yield deviations in the [−5,4] % range compared to validated nodal results. Finally, additional validation was performed using start-up measurements from two successive cycles. Eight MC models were found to be subcritical, on average by 51 pcm, with a standard deviation of 25 pcm.

Multiscale Approach of Investigating the Density of Simulated Fuel for a Zero Power Reactor

Multiscale Approach of Investigating the Density of Simulated Fuel for a Zero Power Reactor

Enriched PQ-based bridgeless isolated one-stage sepic PFC converter for power solutions

ABSTRACT This article deals with an enriched power quality (PQ) based bridgeless isolated one-stage (BIOS) Sepic PFC converter as a cost-effective power solution. The presented revamped bridgeless structure on the front-end avoids unnecessary capacitive coupling and assures less current harmonic distortions, better power factor (PF) at the AC mains to confirm the permissible power quality (PQ) metrics as per IEC 61,000-3–2 standards. This PFC circuit is modelled to be operated on discontinuous inductor current mode (DICM) to reveal the innate zero current switching (ZCS) and power factor correction (PFC) capability. The added merits of DICM and high-frequency isolation involve lesser number of sensors, part count, control complications, size and cost associated with the entire power conversion. Further, the hardware setup of 250W/48 V power solution is assembled to testify the performance of the developed circuit. From the experimental outcomes it is notable that this power solution retains the bettered PQ profile within the perceivable limits even under broad range of source voltage and load discrepancies. Finally, the extensive loss modelling of the power circuit is formulated to evaluate the actual efficiency of the entire power conversion.

An Approach to Near Zero Power Bi-Stable Driving With a Simple Pulse Signal for RF MEMS Switch

An Approach to Near Zero Power Bi-Stable Driving With a Simple Pulse Signal for RF MEMS Switch

Analysis of variation of neutronic and kinetic parameters of a Heavy Water Zero Power Reactor caused by changes in the fuel lattice pitch using MCNPX code

Analysis of variation of neutronic and kinetic parameters of a Heavy Water Zero Power Reactor caused by changes in the fuel lattice pitch using MCNPX code

Integrated Electromagnetic Actuator With Adaptable Zero Power Gravity Compensation

Integrated Electromagnetic Actuator With Adaptable Zero Power Gravity Compensation

Development of uncertainty quantification module for VVER analysis in STREAM/RAST-V two-step method

This paper introduces the creation of a module for Uncertainty Quantification (UQ) specifically designed for VVER analysis through the implementation of the STREAM/RAST-V two-step approach. The aim was to expand the range of use by developing a UQ module tailored for analyzing VVER. This research presents two innovative computational functionalities: (1) development of a library for the pin-based pointwise energy slowing down method (PSM), and (2) extension of the analysis area to study hexagonal-geometry fuel assemblies. The proposed UQ scheme was evaluated through verification using UAM benchmark, and comparative analysis between codes using SCALE 6.2.2 for. STREAM provides an accuracy comparable to that of SCALE 6.2.2. Additionally, a PSM covariance library was utilized in the calculations, achieving 0.7941% and 0.7907% accuracies in the hot full power and hot zero power calculations, respectively. To assess the UQ sequences in the two-step method, the STREAM/RAST-V calculation scheme was verified using the STREAM lattice code. To conclude, this study furnishes comprehensive insights into the development of the UQ module within the two-step method for VVER analysis, and it validates its performance through utilization of the UAM benchmark.

Systemwide energy return on investment in a sustainable transition towards net zero power systems

The Glasgow Climate Pact articulated the vital importance of renewables in reducing emissions on the way to net-zero pledges. During the power sector transition, foreseeing conditions affecting the plausibility of pathway options is crucial for specifying an optimal system development strategy. This study examines the net energy performance of nine decarbonisation global energy transition scenarios until 2050 by applying a newly developed systemwide energy return on investment (EROI) model. All scenarios result in an EROI value above the upper limit of the net energy cliff, expected to be around 10. EROI trends heavily depend on transition paths. Once achieving higher renewable energy shares begin requiring significant enabling technologies, EROI continually declines as the shares increase. Shortening the transition period leads to a sharper declining of EROI, which stabilises after achieving 100% renewables. The vulnerability arising from natural gas and oil depletions may have worst impact on EROI of fossil fuels dominated systems.

Time discretization sensitivity analysis for a rod ejection transient scenario in a generic SMR concept using Serpent/SUBCHANFLOW

This paper analyses a control rod ejection transient scenario in a generic SMR concept using the multi-physics coupling tool which includes the Monte Carlo Serpent code (developed at VTT, Finland) and the subchannel thermal-hydraulic code SUBCHANFLOW (developed at KIT, Germany). A Hot Zero Power state (HZP at 330 W) is considered for the initial condition. A control rod assembly located in the peripheral part of the core is ejected in 0.05 s, inserting a reactivity of ~1.4$ into the system and producing a fast excursion of the power in an asymmetric shape, achieving a peak power ~107 times bigger than the initial state. The thermal-hydraulic feedback then controls the prompt-critical condition, achieving a subcritical state. The analysis is restricted to one second time evolution, and a sensitivity analysis on the time discretization using different time bins is performed. The results show how the use of different time discretizations impact the prediction of the main safety parameters’ evolution, with differences up to ~50% in peak power, ~100 °C in fuel temperature, ~20 °C in cladding temperature, and ~40% in DNB ratio. For this particular problem, it is concluded that shorter time bins are needed; minimum differences in terms of temperatures were observed when using 1 ms and 0.5 ms bins, suggesting that time bins of these orders are appropriate for the type of scenario analyzed in this work.

From Zero Energy to Zero Power Buildings: A new paradigm for a sustainable transition of the building stock

This research introduces an innovative method aimed at evaluating building energy performance within urban environments and communities, departing from the conventional Zero Energy Building (ZEB) concept and introducing the Zero Power Building (ZPB) framework. This approach, overcoming the limitations of the ZEB concept, offers a holistic definition in line with the goal of achieving a Zero-emission Building stock. By employing a power balance assessment coupled with dynamic Key Performance Indicators (KPIs), this methodology surpasses traditional techniques, providing a more accurate assessment of energy consumption and generation patterns. The method was applied to a district case study encompassing seven nearly Zero Energy Buildings (nZEBs), demonstrating its potential efficacy. Findings indicate how the proposed framework can accurately evaluate the integration of energy storage and sharing strategies, increasing the Zero Power target from 29 % to 51 % of annual hours. KPIs were also dynamically examined at the building and district level, introducing the concept of KPI accuracy and identifying pivotal hourly patterns to guide a sustainable transistion. The adoption of the Zero Power Building framework and the utilization of dynamic KPIs offer viable solutions to address conventional limitations in building energy assessments. This approach aids in guiding targeted energy efficiency measures aimed at fostering sustainable and Zero-emission Communities.

Characterization of neutronic parameters and radiation shielding design for an aqueous homogeneous reactor

In this research, an aqueous homogeneous reactor is simulated and its neutronic parameters are investigated. Due to the negative reactivity caused by temperature change and void formation, the cold excess reactivity is considered equal to 4 βeff. Also, calculations of radiation shielding and neutronic characterization of the reactor are performed. For different heights of uranyl sulfate fuel, the effective multiplication factor (keff) of the reactor is calculated under cold zero power and hot full power conditions to assess the required excess reactivity. The amount of fuel burnup and changes in the keff are investigated for 500 days, finally 200 operating days are chosen as the working duration of the reactor. The control rods worth (CRW) for different diameters of boron carbid and reactor safety parameters including shot down margin (SDM) and safety reactivity factor (SRF), temperature and void coefficients of reactivity are analyzed. In order to design a suitable radiation shield for this reactor, two different shields are considered. The first shield is a combination of polyethylene thicknesses and barite concrete, and the second shield is made only of barite concrete. The total thickness of the first and second shield was 230 and 180 cm, respectively. Due to the problems of using polyethylene (e.g. problems related to machining, shield dimensions and low melting temperature), the second shield is chosen as the suitable radiation shield for this reactor. Using this radiation shield, the total dose rates of neutron and gamma rays satisfy the ICRP dose limits.

Measurement of leakage neutron flux from reactor tank surface of AHWR-critical facility

AHWR - Critical Facility (AHWR - CF) is a “zero power” reactor designed to carry out various reactor physics experiments for validation of AHWR physics design. AHWR-CF is a vertical tank type reactor. This paper describes the experiments carried out for neutron flux measurements on the reactor tank surface of AHWR-CF. A number of bare Au and cadmium covered Ni foils were used to measure thermal and fast neutron flux at the outer surface of the reactor tank. One cadmium covered Au foil was also irradiated at one of the locations on the tank surface, to estimate the epithermal component of neutron flux. Westcott thermal flux on the tank surface (at an elevation of 120 cm from tank bottom) was found to be (5.48 ± 0.57)E+6 n cm−2 s−1 on one of the sides of the reactor tank. Cadmium ratio for Au for this location was 40.28, indicating a highly thermalized neutron spectrum. No statistically significant activity was found in the irradiated Ni foils, indicating the absence of fast neutron flux above the measurable threshold. Low value of flux on the reactor tank surface implies that any irradiation damage in the AHWR-CF reactor tank material will be insignificant over its period of operation.

From Zero Energy to Zero Power Buildings: A new framework to define high-energy performance and carbon-neutral buildings

The definition of Zero Energy Building (ZEB) has often been controversial both in regulation and research. This work explores a new evaluation framework introducing the Zero Power Building (ZPB) concept, a novel method that studies the relationship of buildings to the physical boundary, weighting system and analysis timeframe, approaching performance assessment at reduced time intervals. The methodology proposed in this paper showcases how the limitations of the ZEB can be overcome by adopting the ZPB concept on a reference commercial building. The case study was analysed under two different scenarios, with and without an electric storage system. The application of the ZPB concept on an hourly basis poses a challenge to the case study performance, considering both final energy use and CO2 emissions. Specifically, the building commonly accepted as a ZEB turns as a ZPB for only 54.76% of annual hours and as carbon-neutral building for 55.58% of annual hours. The paper presents an innovative methodology that aims to assist in the design and operation of future buildings, as well as provide guidance for policymakers and regulators. The findings emphasize the significance of using dynamic assessment strategies to accurately evaluate the buildings performances and enable meaningful comparisons in various contexts.

Subcritical neutron noise measurements for plutonium systems with varying geometry and mass

Recently, experiments were performed at the National Criticality Experiments Research Center (NCERC) with Zero Power Physics Reactor (ZPPR) plates in two very different geometries. The intent of this set of experiments was to provide the EUCLID (Experiments Underpinned by Computational Learning for Improvements in Nuclear Data) project team measured data of multiple radiation detector responses to be used in an adjustment of plutonium nuclear data. The work shown in this paper will focus on multiplicity results measured for subcritical arrangements of ZPPR plates in the two geometries. The Hage–Cifarelli formalism of the Feynman variance-to-mean method, a moments-based time-correlated neutron noise approach, was used. A validation of the methodology used to estimate uncertainties in the moments was performed and is presented. The effective neutron multiplication factor (keff) value were inferred from this analysis. The keffvalues were compared to simulated values using the radiation transport code Monte Carlo N-Particle® (MCNP). The results shown in this work provide evidence of larger bias in keffvalues as the geometric buckling of the system increases. This effect will be important for nuclear data validation and future adjustments of plutonium nuclear data.

Effect of cross-sections data on calculated static neutronic parameters of PWR MOX/UO2 core transient benchmark case using NODAL3 code

This paper describes the effect of cross-section data generated by several codes on calculated neutronic parameters. The Pressurized Water Reactor Mixed Oxide and Uranium Oxide (PWR MOX/UO2) Core Transient Benchmark case was chosen because it has been used widely to validate neutronic codes. The cross-section data in this study will be generated by SRAC, Serpent, and HELIOS codes. The NODAL3 code will be used to calculate neutronic parameters from each cross-section. The neutronic parameters calculated by NODAL3 are the effective multiplication factor (keff), control rod worth, critical boron concentration, and power distribution under Hot Zero Power (HZP) conditions. The Power-Weighted Error (PWE) and Error-Weighted Error (EWE), as a measure of the relative error in fuel assembly power, are less than 5 %, indicating that the calculation is consistent with DeCART as a reference. The difference in calculated radial power peaking factor for all three cross-sections to reference data reaches 6.284 % (G-3), 8.438 % (G-3), and 10.998 % (C-7), respectively, for SRAC, Serpent, and HELIOS. The axial power distribution calculated by NODAL3 at the top and bottom of the reactor core has a relative error that peaked at 16.60 %, 13.86 %, and 10.20 %, respectively, for cross-sections provided by SRAC, Serpent, and HELIOS. Further improvements are needed for NODAL3 by applying various discontinuity factors to improve its performance.

The reliability of coronary artery calcium score in symptomatic patients: Questioning the “power of zero”

The reliability of coronary artery calcium score in symptomatic patients: Questioning the “power of zero”

Wired-Wireless Hierarchical Sensor Network using Zero power Sensor Node

The wireless sensor network, WSN, is a promising technology to make our social life better. However, the maintenance of the battery attached to each sensor node avoids WSN widely be used. The zero standby-power sensor node (ZSSN) extends battery life by eliminating standby power, but they impose high cost and maintenance burdens because each node has its own battery and wireless module. This paper proposes a wired-wireless hierarchical sensor network consisting of a small network group of ZPSNs (Zero power sensor node) with large capacitor as power supply that are wired together, and the parent node has a wireless module and an energy harvester. The proposed WSN can suppress the number of energy harvesters and wireless modules to that of groups. There are no batteries by replaced to the capacitors. That is, our WSN can reduce the maintenance and cost caused by which there is no battery, and each only parent node has wireless module and energy harvester. The experimental result shows that the standby ZPSN can keep enough voltage 48 days on the large capacitor to operate in active mode correctly.

Immune sets in monotone infection rules. Characterization and complexity

Many dissemination processes in graphs can be described as follows at a basic level. At each step of the process, some vertices of the graph are coloured blue, and the remaining are coloured white, and a well-defined infection rule acts locally on a chosen element of the graph. As an outcome of this action, perhaps one or more white vertices are forced to become blue. Zero forcing, power domination and bootstrap percolation are some examples of widely studied infection rules.This paper presents a general view of infection rules on graphs, paying particular attention to monotone rules. We state several results referring to the final stable set of blue vertices at the end of the dissemination process driven by the infection rule R, and to the combinatorial transversal relation between the families of inclusion-minimal R-forcing and R-immune sets of the graph. Our results apply to many infection rules considered in the literature, as well as to new ones introduced in this paper. Besides, for each one of these infection rules, we provide a characterization of their R-immune sets formulated in terms of neighbourhood, so without referring to the iterative dissemination process acting on the graph.In the second part of the paper, and for the particular rules treated in the first part (k-PUSH, (kb,kw)-PUSH, α-PUSH, k-PULL, α-PULL, and k-wPULL), we prove the NP-Completeness of the decision problem associated to the corresponding R-immune number of the graph.