A Fuel Channel Design for CANDU-SCWR

2006 ◽  
Author(s):  
C. K. Chow ◽  
S. J. Bushby ◽  
H. F. Khartabil
Keyword(s):  
Corrosion Resistance ◽  
Material Selection ◽  
Porous Ceramic ◽  
Pressure Tube ◽  
Thermodynamic Efficiency ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Fuel Channel ◽  
Pressure Tubes ◽  
Metal Liner

The CANDU®-Supercritical Water Reactor (CANDU-SCWR) is one of the six reactor concepts being considered by the Generation-IV International Forum (GIF) for international collaborative R&D. With SCW coolant, the thermodynamic efficiency is increased to over 40%. The CANDU-SCWR is moderated using heavy water, and it has fuel bundles residing inside horizontal pressure tubes, similar to the current CANDU design. The coolant, however, is light water at 25 MPa, with an inlet temperature of 350°C and an outlet temperature of 625°C. Because of the high temperature and high pressure of the coolant, the standard CANDU pressure tube design cannot be used. This paper presents one of the insulated pressure tube designs being considered for the CANDU-SCWR fuel channels. Unlike current CANDU reactors, the proposed CANDU-SCWR fuel channel does not use calandria tubes to separate the pressure tubes from the moderator. Each pressure tube is in direct contact with the moderator, which operates at an average temperature of about 80°C. The pressure tube is thermally insulated from the hot coolant by a porous ceramic insulator. A perforated metal liner protects the insulator from being damaged by the fuel bundles and erosion by the coolant. The coolant pressure is transmitted through the perforated metal liner and insulator and applied directly to the relatively cold pressure tube. The material selection for each fuel channel component depends on its function. The fuel sheaths and the perforated liner must have high corrosion resistance in SCW, although their resident times are significantly different. The insulator must have high thermal resistance and corrosion resistance in SCW, plus sufficient strength to bear the weight of the fuel bundles without significant thickness reduction during its design life. The pressure tube is the pressure boundary material, so it must have high strength to contain the coolant. One common requirement for all in-core fuel channel components is that they should be as neutron transparent as possible. The irradiation deformation of all these components must also be considered in their design. This paper presents the design of this fuel channel, reviews existing data for materials, indicates where more data are required, and summarizes our plans to obtain these data.

Thermal Aspects of Using Uranium Dicarbide Fuel in an SCWR at Maximum Heat-Flux Conditions

2010 ◽  
Author(s):  
Caleb Pascoe ◽  
Ashley Milner ◽  
Hemal Patel ◽  
Wargha Peiman ◽  
Graham Richards ◽  
...  
Keyword(s):  
Heat Flux ◽  
Supercritical Water ◽  
Alternative Fuels ◽  
Elevated Temperatures ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Bulk Fluid ◽  
Maximum Heat ◽  
Fuel Channel ◽  
Sheath Material

There are 6 prospective Generation-IV nuclear reactor conceptual designs. SuperCritical Water-cooled nuclear Reactors (SCWRs) are one of these design options. The reactor coolant in SCWRs will be light water operating at 25 MPa and up to 625°C, actually at conditions above the critical point of water (22.1 MPa and 374°C, respectively). Current Nuclear Power Plants (NPPs) around the world operate at sub-critical pressures and temperatures achieving thermal efficiencies within the range of 30–35%. One of the major advantages of SCWRs is increased thermal efficiency up to 45–50% by utilizing the elevated temperatures and pressures. SuperCritical Water (SCW) behaves as a single-phase fluid. This prevents the occurrence of “dryout” phenomena. Additionally, operating at SCW conditions allows for a direct cycle to be utilized, thus simplifying the steam-flow circuit. The components required for steam generation and drying can be eliminated. Also, SCWRs have the ability to support hydrogen co-generation through thermochemical cycles. There are two main types of SCWR concepts being investigated, Pressure-Vessel (PV) and Pressure-Tube (PT) or Pressure-Channel (PCh) reactors. The current study models a single fuel channel from a 1200-MWel generic PT-type reactor with a pressure of 25 MPa, an inlet temperature of 350°C and an outlet temperature of 625°C. Since, SCWRs are presently in the design phase there are many efforts in determining fuel and sheath combinations suited for SCWRs. The design criterion to determine feasible material combinations is restricted by the following constraints: 1) The industry accepted limit for fuel centreline temperature is 1850°C, and 2) sheath-material-temperature design limit is 850°C. The primary candidate fuel is uranium dioxide. However; previous studies have shown that the fuel centreline temperature of an UO2 pellet might exceed the industry accepted limit for the fuel centreline temperature. Therefore, investigation on alternative fuels with higher thermal conductivities is required to respect the fuel centreline temperature limit. Sheath (clad) materials must be able to withstand the aggressive SCW conditions. Ideal sheath properties are a high-corrosion resistance and high-temperature mechanical strength. Uranium dicarbide (UC2) is selected as a choice fuel, because of its high thermal conductivity compared to that of conventional nuclear fuels such as UO2, Mixed OXide (MOX) and Thoria (ThO2). The chosen sheath material is Inconel-600. This Ni-based alloy has high-yield strength and maintains its integrity beyond the design limit of 850°C. This paper utilizes a generic SCWR fuel channel containing a continuous 43-element bundle string. The bulk-fluid, sheath and fuel-centreline temperature profiles together with Heat Transfer Coefficient (HTC) profile were calculated along the heated length of a fuel channel at the maximum Axial Heat Flux Profiles (AHFPs).

Engineering Process-Zone Model for Evaluation of Structural Strength of Fuel Channel Annulus Spacers in CANDU Nuclear Reactors

2017 ◽  
Author(s):  
Douglas Scarth ◽  
Steven Xu ◽  
Cheng Liu
Keyword(s):  
Structural Strength ◽  
Process Zone ◽  
Maximum Load ◽  
Pressure Tube ◽  
Irradiation Damage ◽  
Zone Model ◽  
Engineering Process ◽  
Fuel Channel ◽  
Load Carrying ◽  
Pressure Tubes

The core of a CANDU(1) (CANada Deuterium Uranium) pressurized heavy water reactor consists of a lattice of either 390 or 480 horizontal Zr-Nb pressure tubes, depending on the reactor design. These pressure tubes contain the fuel bundles. Each pressure tube is surrounded by a Zircaloy calandria tube that operates at a significantly lower temperature. Fuel channel annulus spacers maintain the annular gap between the pressure tube and calandria tube throughout the operating life. To meet this design requirement, annulus spacers must have adequate structural strength to carry the interaction loads imposed between the pressure tube and calandria tube. Crush tests that have been performed on specimens from as-received and ex-service Inconel X-750 alloy spacers have demonstrated that the structural strength of Inconel X-750 spacers has degraded with operating time due to irradiation damage. There was a need for an engineering model to predict the future maximum load carrying capacity of the spacer coils for use in Fitness-for-Service evaluations of spacer structural integrity. An engineering process-zone model has been developed and used to analyze the spacer crush test results, and provide predictions of the Inconel X-750 spacer coil future maximum load carrying capacities. The engineering process-zone model is described in this paper. The process-zone model is based on the strip-yield approach of a process zone with a uniform restraining stress representing the fracture region that is surrounded by elastic material.

Materials and Stress Analysis of Fuel-Channel of a Generic 1200-MWel Pressure-Channel Reactor With Nuclear Steam Reheat

2014 ◽  
Author(s):  
Rand Abdullah ◽  
Matthew Baldock ◽  
Andrei Vincze ◽  
Khalil Sidawi ◽  
Igor Pioro
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Pressure Tube ◽  
Outlet Temperature ◽  
Pressurized Water ◽  
Fuel Channel ◽  
Suitable Material ◽  
Inconel 600 ◽  
Fuel Bundle ◽  
Ss 304

The objective of this paper is to modify the current existing CANFLEX® fuel-bundle design to examine its ability to withstand high-temperature conditions of a proposed generic reactor with nuclear steam reheat. One of this reactor’s characteristics is having Super-Heated Steam (SHS) channels in addition to Pressurized-Water (PW) channels in order to increase the thermal efficiency of the plant by about 7–12%. This increase may be attained by raising the outlet temperature of the SHS-channels coolant to about 550°C. Operating at the higher temperatures will definitely have an effect on the mechanical and neutronic properties of fuel-channel materials, specifically on fuel-sheath and pressure-tube materials. This paper compares Inconel-600 and SS-304 in order to determine the most suitable material for SHS-channel’s sheath and pressure tube. This is achieved by comparing strength of materials by performing stress- and displacement-analysis simulation using NX8.5 software (NX8.5, 2009). The analysis in this paper can also be applied to other Nuclear-Power Plants (NPPs) that require operating at higher temperatures such as Super-Critical Water-cooled Reactors (SCWRs).

Deformation Behaviour of a Transversely Loaded Garter Spring

2004 ◽  
Author(s):  
Brian W. Leitch
Keyword(s):  
Finite Element ◽  
Heavy Water ◽  
Reactor Core ◽  
Pressure Tube ◽  
Fuel Channel ◽  
Helical Springs ◽  
Pressure Tubes ◽  
Non Linear ◽  
Rigid Component ◽  
Water Moderator

The CANDU power generation system is based on a natural uranium fuelled reactor with a heavy water moderator. A unique feature of the CANDU reactor is the horizontal fuel channel that allows on-line re-fuelling and fuel management. Pressure tubes containing the fuel bundles and pressurized heavy water coolant are the in-core component of the fuel channel assemblies. Calandria tubes span the length of the reactor core and provide passageways for the pressure tubes through the reactor core. The calandria and pressure tubes are each approximately 6 meters long. The calandria tube separates the heavy water moderator (∼80°C) from the pressure tube (∼300°C). Both tubes are subjected to gravity loads but the pressure tube carries the additional load of the fuel bundles as well as experiencing high temperature and irradiation induced material effects. The pressure tube deflects under the combined loading and areas of the pressure tube could come into contact with the calandria tube. This contact would limit the operating efficiency and lifetime of the fuel channel. To maintain a gap between the pressure and calandria tubes, helical springs manufactured from rectangular cross-section wire are placed over the pressure tube. These helical springs are known as garter springs and four such springs are spaced along the pressure tube. Initially, there is no contact between the springs and the calandria tube, but as gravity forces and creep effects begin to act, the pressure tube sags and garter spring/calandria tube contact occurs. As the pressure tube continues to deform, a portion of the pressure tube weight, fuel and coolant is transmitted through the garter spring onto the calandria tube. The calandria tube, in turn, begins to deflect under the applied stresses. This creep deformation of the fuel channel takes place over many thousands of operating hours. Eventually, creep induces a permanent vertical deformation (sag) in the fuel channel. The sag of a fuel channel is an important factor in the operation of the structure and many methods are used to determine the general response of the pressure tube/calandria tube/garter spring system. These methods assume the garter spring is a rigid component. This paper specifically examines the garter spring behaviour with respect to the non-linear material and contact response between the pressure tube/garter spring/calandria tube components. A three dimensional (3-D) finite element solid model of the garter spring is used to determine the non-linear response of the helical garter spring to the transverse forces applied from 3-D shell finite element models of the pressure and calandria tubes. Comparison with experimental, crushing tests on garter springs illustrate the analytical model is well behaved. Applying the operating load to the 3-D model shows that the garter spring’s transverse deformation is small and that assuming the garter spring is a rigid component is valid.

Axial Power and Coolant-Temperature Profiles for a Non-Re-Entrant Pressure-Tube Supercritical Water-Cooled Reactor Fuel Channel

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Vitali Kovaltchouk ◽  
Eleodor Nichita ◽  
Eugene Saltanov
Keyword(s):  
Cross Sections ◽  
Power Distribution ◽  
Pressure Tube ◽  
Coolant Temperature ◽  
Outlet Temperature ◽  
Thermal Hydraulics ◽  
Fuel Temperature ◽  
Fuel Channel ◽  
Technical Specifications ◽  
Institute Of Technology

The axial power and coolant-temperature distributions in a fuel channel of the Generation IV pressure-tube super-critical water-cooled reactor (PT-SCWR) are found using coupled neutronics-thermal-hydraulics calculations. The simulations are performed for a channel loaded with a fresh, 78-element Th-Pu fuel assembly. Neutronics calculations are performed using the DONJON diffusion code using two-group homogenized cross sections produced using the lattice code DRAGON. The axial coolant temperature profile corresponding to a certain axial linear heat generation rate is found using a code developed in-house at University of Ontario Institute of Technology (UOIT). The effect of coolant density, coolant temperature, and fuel temperature variation along the channel is accounted for by generating macroscopic cross sections at several axial positions. Fixed-point iterations are performed between neutronics and thermal-hydraulics calculations. Neutronics calculations include the generation of two-group macroscopic cross sections at several axial positions, taking into account local parameters such as coolant temperature and density and average fuel temperature. The coolant flow rate is adjusted so that the outlet temperature of the coolant corresponds to the SCWR technical specifications. The converged axial power distribution is found to be asymmetric, resembling a cosine shape skewed toward the inlet (reactor top).

NOx-Abatement Potential of Lean-Premixed GT Combustors

1998 ◽  
Vol 120 (1) ◽  
pp. 48-59 ◽  
Author(s):  
T. Sattelmayer ◽  
W. Polifke ◽  
D. Winkler ◽  
K. Do¨bbeling
Keyword(s):  
Flame Front ◽  
Thermodynamic Cycle ◽  
Turbulent Flames ◽  
Small Scale ◽  
Thermodynamic Efficiency ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Second Stage ◽  
Nox Abatement ◽  
Preferential Diffusion

The influence of the structure of perfectly premixed flames on NOx formation is investigated theoretically. Since a network of reaction kinetics modules and model flames is used for this purpose, the results obtained are independent of specific burner geometries. Calculations are presented for a mixture temperature of 630 K, an adiabatic flame temperature of 1840 K, and 1 and 15 bars combustor pressure. In particular, the following effects are studied separately from each other: • molecular diffusion of temperature and species; • flame strain; • local quench in highly strained flames and subsequent reignition; • turbulent diffusion (no preferential diffusion); • small scale mixing (stirring) in the flame front. Either no relevant influence or an increase in NOx production over that of the one-dimensional laminar flame is found. As a consequence, besides the improvement of mixing quality, a future target for the development of low-NOx burners is to avoid excessive turbulent stirring in the flame front. Turbulent flames that exhibit locally and instantaneously near laminar structures (“flamelets”) appear to be optimal. Using the same methodology, the scope of the investigation is extended to lean-lean staging, since a higher NOx-abatement potential can be expected in principle. As long as the chemical reactions of the second stage take place in the boundary between the fresh mixture of the second stage and the combustion products from upstream, no advantage can be expected from lean-lean staging. Only if the primary burner exhibits much poorer mixing than the second stage can lean-lean staging be beneficial. In contrast, if full mixing between the two stages prior to afterburning can be achieved (lean-mix-lean technique), the combustor outlet temperature can in principle be increased somewhat without NO penalty. However, the complexity of such a system with a larger flame tube area to be cooled will increase the reaction zone temperatures, so that the full advantage cannot be realized in an engine. Of greater technical relevance is the potential of a lean-mixlean combustion system within an improved thermodynamic cycle. A reheat process with sequential combustion is perfectly suited for this purpose, since, first, the required low inlet temperature of the second stage is automatically generated after partial expansion in the high pressure turbine, second, the efficiency of the thermodynamic cycle has its maximum and, third, high exhaust temperatures are generated, which can drive a powerful Rankine cycle. The higher thermodynamic efficiency of this technique leads to an additional drop in NOx emissions per power produced.

NOx-Abatement Potential of Lean-Premixed GT-Combustors

1996 ◽  
Author(s):  
T. Sattelmayer ◽  
W. Polifke ◽  
D. Winkler ◽  
K. Döbbeling
Keyword(s):  
Flame Front ◽  
Thermodynamic Cycle ◽  
Turbulent Flames ◽  
Small Scale ◽  
Thermodynamic Efficiency ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Second Stage ◽  
Nox Abatement ◽  
Preferential Diffusion

The influence of the structure of perfectly premixed flames on NOx-formation is investigated theoretically. Since a network of reaction kinetics modules and model flames is used for this purpose, the results obtained are independent of specific burner geometries. Calculations are presented for a mixture temperature of 630K, an adiabatic flame temperature of 1840K and 1 and 15 bars combustor pressure. In particular, the following effects are studied separately from each other: - molecular diffusion of temperature and species - flame strain - local quench in highly strained flames and subsequent reignition - turbulent diffusion (no preferential diffusion) - small scale mixing (stirring) in the flame front Either no relevant influence or an increase in NOx-production over that of the one-dimensional laminar flame is found. As a consequence, besides the improvement of mixing quality, a future target for the development of low-NOx burners is to avoid excessive turbulent stirring in the flame front. Turbulent flames that exhibit locally and instantaneously near laminar structures (“flamelets”) appear to be optimal. Using the same methodology, the scope of the investigation is extended to lean-lean staging, since a higher NOx-abatement potential can be expected in principle. As long as the chemical reactions of the second stage take place in the boundary between the fresh mixture of the second stage and the combustion products from upstream, no advantage can be expected from lean-lean staging. Only if the primary burner exhibits much poorer mixing than the second stage can lean-lean staging be beneficial. In contrast, if full mixing between the two stages prior to afterburning can be achieved (lean-mix-lean technique), the combustor outlet temperature can in principle be increased somewhat without NO-penalty. However, the complexity of such a system with a larger flame tube area to be cooled will increase the reaction zone temperatures, so that the full advantage cannot be realised in an engine. Of greater technical relevance is the potential of a lean-mix-lean combustion system within an improved thermodynamic cycle. A reheat process with sequential combustion is perfectly suited for this purpose, since, firstly, the required low inlet temperature of the second stage is automatically generated after partial expansion in the high pressure turbine, secondly, the efficiency of the thermodynamic cycle has its maximum and, thirdly, high exhaust temperatures are generated, which can drive a powerful Rankine cycle. The higher thermodynamic efficiency of this technique leads to an additional drop in NOx-emissions per power produced.

Heat Transfer to Supercritical Water in Vertical Annular Channel and 3-Rod Bundle

2009 ◽  
Author(s):  
V. G. Razumovskiy ◽  
Eu. N. Pis’mennyy ◽  
A. Eu. Koloskov ◽  
I. L. Pioro
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Supercritical Water ◽  
Annular Channel ◽  
Heat Fluxes ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Rod Bundle ◽  
Temperature Regimes ◽  
Outside Diameter

The results of heat transfer to supercritical water flowing upward in a vertical annular channel (1-rod channel) and tight 3-rod bundle consisting of the tubes of 5.2-mm outside diameter and 485-mm heated length are presented. The heat-transfer data were obtained at pressures of 22.5, 24.5, and 27.5 MPa, mass flux within the range from 800 to 3000 kg/m2·s, inlet temperature from 125 to 352°C, outlet temperature up to 372°C and heat flux up to 4.6 MW/m2 (heat flux rate up to 2.5 kJ/kg). Temperature regimes of the annular channel and 3-rod bundle were stable and easily reproducible within the whole range of the mass and heat fluxes, even when a deteriorated heat transfer took place. The data resulted from the study could be applicable for a reference estimation of heat transfer in future designs of fuel bundles.

Experimental Study to Characterize the Performance of Combined Photovoltaic/Thermal Air Collectors

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Véronique Delisle ◽  
Michaël Kummert
Keyword(s):  
Thermal Efficiency ◽  
Closed Loop ◽  
Multiple Linear Regression Model ◽  
Open Loop ◽  
Electrical Performance ◽  
Back Surface ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Cell Temperature ◽  
Average Temperature

Combined photovoltaic/thermal (PV/T) collectors show great potential for reaching the objective of net-zero energy consumption in buildings, but the number of products on the market is still very limited. One of the reasons for the slow market uptake of PV/T collectors is the absence of standardized methods to characterize their performance. Performance characterization is a challenge for PV/T collectors because of the interaction between the thermal and electrical yield. This study addresses this particular issue for PV/T air collectors used in either closed-loop or open-loop configurations. In particular, it presents the potential of the equivalent cell temperature method to determine the temperature of the PV cells in a PV/T air collector and validates models to predict the thermal performance and cell temperature for this particular type of solar collector. Indoor and outdoor experimental tests were performed on two c-Si unglazed PV/T modules. The indoor part of this procedure provided the thermal diode voltage factor and the open-circuit voltage temperature coefficient, two parameters that are essential in the calculation of the equivalent cell temperature. The outdoor procedure consisted of acquiring simultaneous electrical and thermal measurements at various inlet temperatures and flowrates. For the collector used in a closed-loop configuration, thermal efficiency models using the fluid inlet, outlet, or average temperature in the calculation of the reduced temperature provided similar results. For an open-loop configuration, a thermal efficiency model as a function of the fluid outlet flowrate was found to be more appropriate. Using selection of variable methods, it was found that a multiple linear regression model using the fluid inlet temperature, the irradiance, and the fluid outlet temperature as predictive variables could be used to estimate both the PV module back surface average temperature and the equivalent cell temperature. When using the PV temperature predicted by these models in the electrical efficiency model, both PV temperatures showed similar performance. In collectors where the PV back surface temperature is not accessible for temperature sensors mounting, the equivalent cell temperature provides a valuable alternative to be used as the PV temperature. The PV/T collector thermal and electrical performance in either closed-loop or open-loop configurations was found to be encapsulated with a series of five-plots.

The antioxidative-activity stability of aloe vera (Aloe vera var. chinensis) instant during storage

Food Research ◽  
2021 ◽  
Vol 5 (4) ◽  
pp. 288-293
Author(s):  
Riyanto ◽  
Ch. Wariyah
Keyword(s):  
Lipid Peroxidation ◽  
Critical Condition ◽  
Antioxidative Activity ◽  
Radical Scavenging ◽  
Aloe Vera ◽  
Oxygen Absorption ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Plastic Film ◽  
Lipid Peroxidation Inhibition

Aloe vera contains a phenolic compound that has bioactive activity. Previous research showed that microencapsulation of aloe vera powder with maltodextrin as an encapsulation agent produced instant aloe vera with high antioxidative activity. The problem was the hygroscopic instant caused rapid moisture and oxygen absorption during storage, therefore decreasing the instant aloe vera antioxidative activity periodically. The aim of this research was to evaluate the antioxidative activity stability of instant aloe vera during storage. The processing of instant aloe vera through a reconstituted aloe vera powder with water with a ratio of 1:120 and then added with 2.5% maltodextrin as the encapsulating agent. The solution was then inserted into a spray dryer with an inlet temperature of 130oC, an outlet temperature of 103oC, and the flow rate of the solution is 350.0 mL/h. The resulted instant aloe vera was divided into 15 packs with a weight of 25 g, and each sample was wrapped with polyethylene plastic film with 0.80 mm thickness and then was stored at 25oC with a relative humidity of 75%. The sample was conducted in triplicate. The moisture content, and antioxidative activity that was based on the ability to capture 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical (RSA) and lipid peroxidation inhibition were analyzed every week until the critical condition was achieved at a moisture level of 12%. The research showed that the radical scavenging activity (RSA) and lipid peroxidation inhibition of instant aloe vera before storage were 16.34±1.22% and 39.33±1.68%, respectively, whereas in the critical condition the RSA was 3.63±0.04% and the lipid peroxidation inhibition was 22.31±0.02%. Based on their antioxidative activity, the appropriate storage time of instant aloe vera was about 12 weeks in polyethylene plastic film of 0.08 mm thickness

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