Design parameters are presented for Tajoura reactor core utilizing the new fuel assemblies with low enriched uranium (LEU, using IRT-4M fuel assemblies) in the steady state safety operational parameters and Loss of Flow transient mathematical models (NATIRT - computer program. The calculated results of the model are presented in the cases of forced convection steady state, transient during emergency tank filling and natural convection after emergency tank filling modes at different reactor core thermal power level. The results of NATIRT for all cases of flow were in good agreement with the PARET and PLTEMP computer programs.

Abstract: A conventional ground-coupled heat pump (GCHP) can be used to supplement heat

rejection or extraction, creating a hybrid system that is cost-eective for certainly unbalanced climes.

This research explores the possibility for a hybrid GCHP to use excess heat from a combined heat

power (CHP) unit of natural gas in a heating-dominated environment for smart cities. A design for

a multi-family residential building is considered, with a CHP sized to meet the average electrical

load of the building. The constant electric output of the CHP is used directly, stored for later use in a

battery, or sold back to the grid. Part of the thermal output provides the building with hot water,

and the rest is channeled into the GCHP borehole array to support the building’s large heating needs.

Consumption and weather data are used to predict hourly loads over a year for a specific multi-family

residence. Simulations of the energies exchanged between system components are performed, and a

cost model is minimized over CHP size, battery storage capacity, number of boreholes, and depth of

the borehole. Results indicate a greater cost advantage for the design in a severely heated (Canada)

climate than in a moderately imbalanced (Ohio) climate.

In certain extremely low probability, severe accident scenarios which have been postulated for liquid metal cooled fast reactors,large bubble cavities containing fuel vapor and fission products transit a layer of coolant and release this material to the cover gas thereby presenting a contribution to an accident-specific source term [5].Mie model in radiation heat transfer has been investigated to analysis and interpret the experiments that conducted during 1980's for oxide UO 2 fueled reactors in Fuel Aerosol Simulant Test (FAST) facility at Oak Ridge National Laboratory (ORNL).These analyses are applied to estimate the bubble collapse of Liquid Metal reactors (LMR's) during a hypothetical core disruptive accident (HCDA).InMie scattering model the particle size was 0.07 µm [6]. The scattering coefficient of UO 2 particles (σ = 1.24 m-1), was calculated by using Mie theory,at the same number of stable nuclei's N (2.9 E15 nuclei/m 3) that resulted from theabsorbed coefficientk = 0.082 m-1 [7].P 1 approximation method was used to solve the radiative heat transfer equation (RTE) in spherical coordinates of participating medium confined between the two concentric spheres.The surfaces of the spheres are assumed to be gray, diffusely emitting and diffusely reflecting boundaries, and an isothermal boundary conditions were assumed at these surfaces.Marsak's boundary condition was to computed, the net radiative heat flux q(τ), and the incident radiation G(τ), to analyze and interpret the CVD experiments data that were conducted in the FAST facility at ORNL [8] and Fast Flux Test Facility reactor (FFTF) in Argonne National Laboratory ANL.The conclude that extracted from this study is greater margin of safety when the bubble rising time is greater than the bubble collapse time since the bubble collapses (UO 2 condenses) before it can reach the top of the vessel therefore there is less chance of release of aerosol as in Oak Ridge National Laboratory (ORNL) FAST experiments and Argonne National Laboratory (FFTF) reactor.

In certain extremely low probability, severe accident scenarios which have been postulated for liquid metal cooled fast reactors, large bubble cavities containing fuel vapor and fission products transit a layer of coolant and release this material to the cover gas thereby presenting a contribution to an accident-specific source term [5]. Rayleigh model in radiation heat transfer has been investigated to analysis and interpret the experiments that conducted during 1980's for oxide UO 2 fueled reactors in Fuel Aerosol Simulant Test (FAST) facility at Oak Ridge National Laboratory (ORNL).These analyses are applied to estimate the bubble collapse of Liquid Metal reactors (LMR's) during a hypothetical core disruptive accident (HCDA). In Rayleigh non-scattering model the particle size was 0.01 µm [6],and according to Mie theory principle, the absorption coefficient for small particle-size distribution was estimated (k = 10 m-1 was used) from reference [7] at complex refractive index of UO 2 at λ = 600 µm and x = 0.0785.A MATLAB code was used to solvethe radiative heat equation (RTE) in spherical coordinates. The mixture is in local thermodynamic equilibrium inside the bubble which has a black body surface boundary.The mixture in the cavity contains three components: the non-condensable gas Xenon, Uranium dioxide vapor, and fog.To simulate fuel bubble's geometry as realistically as possible, according to experimental observation, the energy equation in a spherical coordinate system has been solved with the radiative flux heat transfer equation (RTE) to obtain the effect of fuel bubble's geometry on the transient radiative heat flux and to predict the transient temperature distribution in the participating medium during a hypothetical core disruptive accident (HCDA) for liquid metal fast breeding reactor (LMFBR) for FAST. The transient temperature distribution in fog region was utilized to predict the amount of condensable UO 2 vapor = − ! " ! #. The conclusion that can be drawn from the present study, is that the Fuel Aerosol Simulant Test (FAST) facility at Oak Ridge National Laboratory has a larger margin of safety since the bubble rising time is greater than the bubble collapse time.

The multi-family residential building sector is the least energy efficient in the United States, thus allowing for ample opportunities for significant cost-effective energy and carbon savings. In the present study, we propose a district solar borehole thermal solar energy storage (BTES) system for both retrofit and new construction for a multi-family residence in the Midwestern United States, where the climate is moderately cold with very warm summers. Actual apartment interval power and water demand data was mined and used to estimate unit level hourly space and water heating demands, which was subsequently used to design a cost-optimal BTES system. Using a dynamic simulation model to predict the system performance over a 25-year period, a parametric study was conducted that varied the sizes of the BTES system and the solar collector array. A life-cycle cost analysis concluded that is it possible for an optimally-sized system to achieve an internal rate of return (IRR) of 11%, while reducing apartment-wide energy and carbon consumption by 46%. Both a stand-alone and solar-assisted ground-source heat pump system were designed and simulated for comparison to the BTES system, and found to be less economically favorable than the solar BTES system. Thus, the promise for district-scale adoption of BTES in multi-family residences is established, particularly for new buildings.

A novel geothermal heat pump (GHP) system with an integrated low- to moderate-temperature salt hydrate phase change material (PCM) storage tank for buildings in cold climates is proposed in this study. The purpose of the PCM storage tank is to dampen peak heating loads and to remove annual ground thermal load imbalances on the ground heat exchanger (GHX) to assist in achieving an optimally-sized GHX. As heat is extracted from the closed-loop system by heat pumps in heating mode, a significant portion of this heat is used to solidify a salt hydrate PCM. This heat of fusion is later released back into the heat transfer fluid, storing it in the PCM tank and GHX for later diurnal and seasonal use. To examine the merits of the proposed concept, electric utility meter data on 15-minute time intervals were mined from an actual apartment building and used to estimate space heating, cooling, and hot water heating loads. Those data were used in an hourly, dynamic 20-year life-cycle simulation model in TRNSYS to design an optimum combination of GHX and PCM storage, where each component was sized to balance the annual ground thermal loads. The system simulation results show significant potential for GHX size reduction with a PCM storage tank, but the system is quite sensitive to the PCM melt temperature due to significant hysteretic nature of the salt hydrate PCM heating and cooling curves. We also find that there is no unique optimum unless other factors are considered such as installation cost and physical constraints; many combinations of GHX size and PCM mass are capable of achieving the design goal with similar annual electric energy consumption. For the cases examined here, a PCM melt temperature of 27 °C yields the most favorable economic results, and a preliminary economic analysis suggests that with typical drilling cost and PCM tank cost values, the GHX size can be reduced by over 50 %.

Analytical study associated with liquid-metal fast breeder reactor (LMFBR) has been investigated by using scattering and non-scattering mathematical radiation models. In the nonscattering model, the radiative transfer equation (RTE) was solved together with the continuity equations of mixture components under local thermodynamic equilibrium. A MATLAB code was used to solve these equations. This application employed a numerical integration to compute the temperature distribution within the bubble and the transient wall heat flux. First, in Rayleigh nonscattering model the particle size was 0.01 µm [6], and according to Mie theory principle, the absorption coefficient for small particle –size distribution was estimated (k = 10 m-1 was used) from reference [7] at complex refractive index of UO2 at λ = 600 µm and x = 0.0785. A MATLAB code was used to solve the radiative heat equation (RTE) in spherical coordinates. The mixture is in local thermodynamic equilibrium inside the bubble which has a black body surface boundary. The mixture in the bubble contains three components: the non-condensable gas Xenon, Uranium dioxide vapor, and fog. To simulate fuel bubble’s geometry as realistically as possible, according to experimental observation, the energy equation in a spherical coordinate system has been solved with the radiative flux heat transfer equation (RTE) to obtain the effect of fuel bubble’s geometry on the transient radiative heat flux and to predict the transient temperature iv distribution in the participating medium during a hypothetical core disruptive accident (HCDA) for liquid metal fast breeding reactor (LMFBR) for FAST. The transient temperature distribution in fog region was used to predict the amount of condensable UO2 vapor. The conclusion that can be drawn from the present study, is that the Fuel Aerosol Simulant Test (FAST) facility at Oak Ridge National Laboratory has a larger margin of safety since the bubble rising time is greater than the bubble collapse time. Second in the scattering model, the spherical harmonics method was used to solve the radiative heat transfer equation (RTE) in spherical coordinates, and the particle size was 0.07 µm [6]. The scattering coefficient of UO2 particles (σ = 1.24 m-1 ), was calculated using Mie theory at the same number of stable nuclei N (2.9 E15 nuclei/m3 ) that resulted from the absorption coefficient k = 0.082 m-1 [7]. The P1 approximation method was used to solve the radiative transfer equation (RTE) in spherical coordinates of participating medium confined between two concentric spheres. The surfaces of the spheres are assumed to be gray, diffusely emitting and diffusely reflecting boundaries, and isothermal boundary conditions were assumed at these surfaces. Marsak’s boundary condition was used to compute the net radiative heat flux, q(τ), and the incident radiation, G(τ), to analyze and interpret CVD experiments data that were conducted in the FAST facility at ORNL [8] and Fast Flux Test Facility reactor (FFTF) at ANL. From this study, it can be concluded that there is greater margin of safety when the bubble rise time is a greater than the bubble collapse time since the bubble collapses (UO2 condenses) before it can reach the top of the vessel. In addition, the work transfer by itself can’t completely eliminate the super-heated vapor, as the bubble contains noncondensable species which hinder condensation. However, it is reasonable to assume that work transfer could decrease the amount of UO2 vapor contained in the bubble as it reached the covergas [63].

Abstract

This article presents yet another methodology for the calculation of dimensionless thermal response factors for vertical borehole ground heat exchanger (GHX) arrays, which is a concept introduced by Eskilson (1987). The presented method is based on a well-known solution to an analogous problem in the field of well hydraulics. This solution method, known mathematically as an incomplete Bessel function, and known in the field of well hydraulics as the 'leaky aquifer function', describes the hydraulic head distribution in an aquifer with predominantly radial flow to a well combined with vertical 'leakage' from geologic layers above and below the pumped aquifer. The solution is adapted to model heat transfer from an array of arbitrarily-placed vertical boreholes of finite depth. With proper expression of parameters in the incomplete Bessel function, we show that g-functions of previous researchers can be approximated. The proposed method has been implemented into Matlab and Excel/VBA for g-function generation and monthly GHX simulation.

In certain extremely low probability, severe accident scenarios which have been postulated for liquid metal cooled fast reactors, large bubble cavities containing fuel vapor and fission products transit a layer of coolant and release this material to the cover gas thereby presenting a contribution to an accident-specific source term. So that a more mechanistic assessment of these types of events can be developed, analyses have recently been performed to account for the heat and work transfer observed in out-of-reactor source term experiments conducted during the 1980’s for oxide fueled reactors in the Fuel Aerosol Simulant Test (FAST) facility at Oak Ridge National Laboratory. In ten experiments, UO2 specimens were vaporized in pools of sodium, and for an additional number of benchmarking tests, in pools of water, for purposes of experimentally assessing the bubble transport characteristics of both types of pools. The current analyses present several firsts for these experiments: (a) a comparison of the bubble-to-coolant transfer rates; heat versus work, (b) a bubble-to-coolant heat transfer model accounting for how condensation and radiation heat transfer are affected by coolant selection; sodium versus water, and (c) an assessment of how both types of heat transfer influence the movement of aerosol-laden bubbles through the coolant pool. These analyses significantly extend previous evaluations of FAST experimental results by providing a more comprehensive model for determining how bubble-coolant interactions affect aerosol transport and, in this way, contribute to data base development associated with mechanistic assessments of the source term.

Experimental and numerical investigations have been performed to study the natural convection heat transfer from a longitudinal fin arrays at different orientation angles. For such purpose, an experimental test rig was manufactured to be used for these investigations. It basically consists of base plate, an array of parallel longitudinal fins, heating unit and layers of thermal insulation. During the experiments, the fin spacing (S) was varied from 3.375 to 33 mm, while the fin height (H) from 15 to 60 mm. The orientation angle (Ф) was changed from 0° to 180°, and temperature difference between fin and surrounding (∆T) from 35 to 95 °C. To understand the general flow patterns dominating flows from the heat sink, the three-dimensionless elliptic governing equations were solved using finite volume computational fluid dynamics (CFD) code. A comparative study between the experimental and numerical results was performed to verify the numerical code. It was found for the configuration tested that the heat transfer rate per unit base area increases with the increase in the fin spacing and reaches a maximum value then decreases with farther increase in the fin spacing. The maximum heat dissipation occurs at optimal spacing 5. 6 S opt = mm. Moreover, the average heat transfer coefficient was found to have a maximum value at Ф = 0° and decreased with the increase of (Ф) to reach a minimum value at Ф = 90°. Empirical correlations between Nussult number, Rayleigh number, fin spacing, fin height, orientation angle, temperature difference between the fin and surroundings were derived.