Advanced Core Design And Fuel Management For Pebble-Bed Reactors

A method for designing and optimizing recirculating pebble-bed reactor cores is presented. At the heart of the method is a new reactor physics computer code, PEBBED, which accurately and efficiently computes the neutronic and material properties of the asymptotic (equilibrium) fuel cycle. This core state is shown to be unique for a given core geometry, power level, discharge burnup, and fuel circulation policy. Fuel circulation in the pebble-bed can be described in terms of a few well?defined parameters and expressed as a recirculation matrix. The implementation of a few heat?transfer relations suitable for high-temperature gas-cooled reactors allows for the rapid estimation of thermal properties critical for safe operation. Thus, modeling and design optimization of a given pebble-bed core can be performed quickly and efficiently via the manipulation of a limited number key parameters. Automation of the optimization process is achieved by manipulation of these parameters using a genetic algorithm. The end result is an economical, passively safe, proliferation-resistant nuclear power plant

A design of selective solar absorber for high temperature applications

This study presents a design of multilayer solar selective absorber for high temperature applications. The optical stack of this absorber is composed of four layers deposited by magnetron sputtering on stainless steel substrates. The first is a back-reflector tungsten layer, which is followed by two absorption layers based on CrAlSiNx/ CrAlSiOyNx structure for phase interference. The final layer is an antireflection layer of SiAlOx. The design was theoretically modelled with SCOUT software using transmittance and reflectance curves of individual thin layers, which were deposited on glass substrates. The final design shows simultaneously high solar absorbance = 95.2 % and low emissivity ε= 9.8% (at 400 ºC) together with high thermal stability at 400 ºC, in air, and 600 ºC in vacuum for 650 h.The authors acknowledge the support of FCT in the framework of the Strategic Funding UID/FIS/04650/2013 and the financial support of FCT, POCI and PORL operational programs through the project POCI-01-0145- FEDER-016907 (PTDC/CTM-ENE/2882/2014), co-financed by European community fund FEDER.info:eu-repo/semantics/publishedVersio

PEBBED ANALYSIS OF HOT SPOTS IN PEBBLE-BED REACTORS

The Idaho National Laboratory’s PEBBED code and simple probability considerations are used to estimate the likelihood and consequences of the accumulation of highly reactive pebbles in the region of peak power in a pebble-bed reactor. The PEBBED code is briefly described, and the logic of the probability calculations is presented in detail. The results of the calculations appear to show that hot-spot formation produces only moderate increases in peak accident temperatures, and no increases at all in normal operating temperatures

Evaluation of the HTR-10 Reactor as a Benchmark for Physics Code QA

The HTR-10 is a small (10 MWt) pebble-bed research reactor intended to develop pebble-bed reactor (PBR) technology in China. It will be used to test and develop fuel, verify PBR safety features, demonstrate combined electricity production and co-generation of heat, and provide experience in PBR design, operation, and construction. As the only currently operating PBR in the world, the HTR-10 can provide data of great interest to everyone involved in PBR technology. In particular, if it yields data of sufficient quality, it can be used as a benchmark for assessing the accuracy of computer codes proposed for use in PBR analysis. This paper summarizes the evaluation for the International Reactor Physics Experiment Evaluation Project (IRPhEP) of data obtained in measurements of the HTR-10’s initial criticality experiment for use as benchmarks for reactor physics codes

Next Generation Nuclear Plant Methods Technical Program Plan

One of the great challenges of designing and licensing the Very High Temperature Reactor (VHTR) is to confirm that the intended VHTR analysis tools can be used confidently to make decisions and to assure all that the reactor systems are safe and meet the performance objectives of the Generation IV Program. The research and development (R&D) projects defined in the Next Generation Nuclear Plant (NGNP) Design Methods Development and Validation Program will ensure that the tools used to perform the required calculations and analyses can be trusted. The Methods R&D tasks are designed to ensure that the calculational envelope of the tools used to analyze the VHTR reactor systems encompasses, or is larger than, the operational and transient envelope of the VHTR itself. The Methods R&D focuses on the development of tools to assess the neutronic and thermal fluid behavior of the plant. The fuel behavior and fission product transport models are discussed in the Advanced Gas Reactor (AGR) program plan. Various stress analysis and mechanical design tools will also need to be developed and validated and will ultimately also be included in the Methods R&D Program Plan. The calculational envelope of the neutronics and thermal-fluids software tools intended to be used on the NGNP is defined by the scenarios and phenomena that these tools can calculate with confidence. The software tools can only be used confidently when the results they produce have been shown to be in reasonable agreement with first-principle results, thought-problems, and data that describe the “highly ranked” phenomena inherent in all operational conditions and important accident scenarios for the VHTR

Epitaxial CuInSe2 thin films grown by molecular beam epitaxy and migration enhanced epitaxy

While CuInSe2 chalcopyrite materials are mainly used in their polycrystalline form to prepare thin film solar cells, epitaxial layers have been used for the characterization of defects. Typically, epitaxial layers are grown by metal-organic vapor phase epitaxy or molecular beam epitaxy (MBE). Here we present epitaxial layers grown by migration enhanced epitaxy (MEE) and compare the materials quality to MBE grown layers. CuInSe2 layers were grown on GaAs (001) substrates by co-evaporation of Cu, In, and Se using substrate temperatures of 450 ºC, 530 ºC, and 620 ºC. The layers were characterized by high resolution X-ray diffraction (HR-XRD), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and atomic force microscopy (AFM). HR-XRD and HR-TEM show a better crystalline quality of the MEE grown layers, and Raman scattering measurements confirm single phase CuInSe2. AFM shows the previously observed faceting of the (001) surface into {112} facets with trenches formed along the [110] direction. The surface of MEE-grown samples appears smoother compared to MBE-grown samples, a similar trend is observed with increasing growth temperature.The authors would like to acknowledge the CAPES (CAPES-INL 04/14), CNPq, and FAPEMIG funding agencies for financial support. We acknowledge the collaboration project with IMMCSIC (AIC-B-2011-0806). P.M.P.S. acknowledges financial support from EU through the FP7 Marie Curie IEF 2012 Action No. 327367.info:eu-repo/semantics/publishedVersio

Next Generation Nuclear Plant Methods Technical Program Plan

One of the great challenges of designing and licensing the Very High Temperature Reactor (VHTR) is to confirm that the intended VHTR analysis tools can be used confidently to make decisions and to assure all that the reactor systems are safe and meet the performance objectives of the Generation IV Program. The research and development (R&D) projects defined in the Next Generation Nuclear Plant (NGNP) Design Methods Development and Validation Program will ensure that the tools used to perform the required calculations and analyses can be trusted. The Methods R&D tasks are designed to ensure that the calculational envelope of the tools used to analyze the VHTR reactor systems encompasses, or is larger than, the operational and transient envelope of the VHTR itself. The Methods R&D focuses on the development of tools to assess the neutronic and thermal fluid behavior of the plant. The fuel behavior and fission product transport models are discussed in the Advanced Gas Reactor (AGR) program plan. Various stress analysis and mechanical design tools will also need to be developed and validated and will ultimately also be included in the Methods R&D Program Plan. The calculational envelope of the neutronics and thermal-fluids software tools intended to be used on the NGNP is defined by the scenarios and phenomena that these tools can calculate with confidence. The software tools can only be used confidently when the results they produce have been shown to be in reasonable agreement with first-principle results, thought-problems, and data that describe the “highly ranked” phenomena inherent in all operational conditions and important accident scenarios for the VHTR

Locally-confined electrodeposition of Cu(In,Ga)Se 2 micro islands for micro-concentrator solar cells

The thin-film micro-concentrator solar cell concept promises to significantly reduce the consumption of the critical raw materials In and Ga by using a micro lens array to illuminate a regular array of Cu(In,Ga)Se 2 micro solar cells. We present the materials-efficient fabrication of micro solar cells by electrodeposition into holes inside a SiO 2 insulating matrix. The electrodeposition process shows a strong dependence on the hole size due to lateral diffusion in the solution, leading to faster deposition at the circumference of the holes. A calibration curve for the deposited CuInSe 2 thickness as a function of hole size is deduced. Cu(In,Ga)Se 2 micro solar cells were fabricated by sequential deposition of Cu and In-Ga, followed by a selenization process, leading to devices with 4.6% efficiency under 34 suns. Using finiteelement simulations, the heat transport in the microconcentrator solar cells is shown to be beneficial