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Performance and Functionality. The use of a plutonium thorium-based fuel cycle in the Canadian SCWR, instead of enriched uranium, may aid in improved sustainability by reducing the overall need for mined uranium, thereby extending world uranium reserves. Enhanced security in the Canadian SCWR may be achieved through the use of fuel cycles with increased intrinsic proliferation resistance and appropriate safeguards.
A second ratio of a cross sectional area of the coolant in the central flow passage to a cross sectional area of the coolant in the fuel bundle chamber may be between approximately 0. The central flow passage may be laterally surrounded by the fuel bundle.
A central axis of the central flow passage may be laterally centered relative to the fuel bundle. The fuel bundle may be rotationally symmetrical about the central axis. The fuel elements of the inner ring may be positioned along a first common circumference about the central axis, and the fuel elements of the outer ring may be positioned along a second common circumference about the central axis that is concentric with and laterally outboard of the first common circumference.
A number of the fuel elements in the inner ring may be equal to a number of the fuel elements in the outer ring. A subchannel distance between each of the fuel elements in the inner ring and the corresponding adjacent one of the fuel elements of the outer ring may be approximately equal to a subchannel distance between each of the fuel elements in the inner ring.
Axial cross sectional areas of each of the fuel elements in the inner ring may be different than axial cross sectional areas of each of the fuel elements in the outer ring. The fuel elements of the inner ring may have a smaller cross sectional area than the fuel elements of the outer ring. The insulator may be encapsulated between inner and outer liner tubes, and the outer liner tube may be arranged along an interior surface of the outer conduit.
The insulator may be formed of a solid material. The inner and outer liner tubes may be formed of different materials. A third ratio of a cross sectional area of the moderator in the moderator region to a cross sectional area of the fuel elements may be between approximately 10 and A forth ratio of a cross sectional area of the moderator in the moderator region to a cross sectional area of the coolant in the fuel bundle chamber and the central flow passage may be between approximately 2.
For each fuel assembly, the inner and outer conduits may be received within a pressure tube. Each pressure tube may include a closed lower end that receives the flow of the coolant from the central flow passage, and directs the flow of the coolant into the fuel bundle chamber.
The nuclear reactor may further include a first plenum chamber in fluid communication with each pressure tube to supply the coolant to the central flow passage, and a second plenum chamber in fluid communication with each pressure tube to collect the coolant from the fuel bundle chamber. The coolant may be light water, and the moderator may be heavy water. Both of the conditions i and ii may be satisfied. A forth ratio of a cross sectional area of the coolant in the centra! For each fuel assembly, the coolant may flow downwardly in the central flow passage, and upwardly in the fuel bundle chamber.
Each pressure tube may include a closed lower end that receives the flow of the coolant from the centra! In the drawings:. Figure 1A is a schematic cross sectional view of an example of a fuel bundle and a fuel channel assembly;. Figure 1 B is a cutaway perspective view of the fuel bundle and the fuel channel assembly of Figure 1A;. Figure 2A is a perspective view of a pressure-tube nuclear reactor including a plurality of fuel channel assemblies;.
Figure 2B is a sectional view of the nuclear reactor of Figure 2A taken along line 2b-2b;. Figure 3 is a quarter core channel map and fuel loading scheme for a nuclear reactor;. Figure 4 is a graph of k-infinity modeling data versus axial position in the nuclear reactor;. Figure 5 is a graph of CVR modeling data versus axial position;. Figure 6 is quarter core channel map showing normalized power profiles;. Figure 7 is a graph of normalized axial power profiles;. Figures 9 and 10 are graphs of axial power profiles; and.
Figures 1 1 and 12 are diagrams of coolant temperature distribution. No embodiment described below limits any claimed invention and any claimed invention may cover apparatuses and methods that differ from those described below. The claimed inventions are not limited to apparatuses and methods having all of the features of any one apparatus or method described below, or to features common to multiple or all of the apparatuses or methods described below.
It is possible that an apparatus or method described below is not an embodiment of any claimed invention. Feeder tubes for coolant flowing out of the fuel channels have been eliminated, and, instead, the fuel channel has a re-entrant or double flow pass configuration.
Light water coolant flows from an inlet plenum into flow tubes located in the center of each fuel channel. The bottom ends of the channels are sealed, and when the coolant reaches the bottom of the central flow tubes, it reaches a space at the bottom of each channel where it is redirected upward and flows through the region containing the fuel pins or elements. In particular, these changes may result in a positive increase in coolant void reactivity CVR and decrease in exit burnup.
Additional changes to the fuel bundle and fuel channel configurations may therefore be introduced in order to lower the CVR and increase the exit burnup. These changes may result in a significant decrease in CVR and large increase in exit burnup, thus recovering the target CVR and exit burnup, and may allow a large margin for additional changes that may be incorporated in the Canadian SCWR design.
The thermalhydraulic assessment focuses specifically on the maximum wall temperature, which may be an important parameter in the design of the fuel bundle. The fuel channel assembly 1 2 may be referred to herein as a high-efficiency re-entrant channel HERC.
In some examples, the conduits 14, 16 may be received within one or more additional conduits or pressure tubes not shown. The inner and outer conduits 14, 16 are illustrated to have generally circular axial cross sectional shapes. Other cross sectional shapes, for example but not limited to, square and hexagonal, may be possible.
A fuel bundle chamber 18 is defined by an annular space between an outer surface of the inner conduit 14 and an opposed inner surface of the outer conduit The fuel bundle 10 is received in the fuel bundle chamber 18, and laterally surrounds a central flow passage Moderation region 22 laterally surrounds the outer conduit However, in some examples, it may be possible to reverse the orientation of the reactor, so that the plenum is arranged on the bottom of the fuel assembly, and the light water coolant would flow up through the central flow passage 20 and then down through the fuel bundle chamber Furthermore, arrangements of the fuel assembly other than vertical may be possible, including, for example, a horizontal arrangement.
The insulator 24 may be sized to be received within the inner surface of the outer conduit 16, so that it is positioned radially intermediate of the fuel bundle chamber 18 and the outer conduit Liner tubes 26a, 26b may encapsulate the insulator 24 to provide a physical barrier between the outer conduit 16 and the insulator 24, and the insulator 24 and the fuei bundle chamber 18, respectively.
In some examples, the fuel bundle chamber 18 may include an additional liner tube not shown arranged between it and the liner tube 26b. However, in some examples, other arrangements of the fuel elements 28a, 28b may be possible, including arrangements having three rings or more, or grid arrangements. The fuel elements 28b of the outer ring are positioned along a second common circumference about the central axis 32, which is concentric with and laterally outboard of the first common circumference.
The fuel bundle 10 is rotationally symmetrical around the central axis 32 of the fuel channel assembly 12, and the number of the fuel elements 28a in the inner ring is equal to the number of the fuel elements 28b in the outer ring in this case thirty one each. Consistent subchannel geometry may enable a more balanced heat transfer and coolant mass flow within the fuel bundle chamber Axial cross sectional areas of the fuel elements 28a of the inner ring may be varied relative to axial cross sectional areas of the fuel elements 28a of the outer ring to facilitate generally uniform subchannel geometry,!
In previous designs for the Canadian SCWR see, for example, a element fuel assembly having three concentric rows described in J. The uneven power distribution may result in an underutilization of the inner rings of fuel elements, and may adversely affect the fuel performance of the outer ring.
In contrast, fuel bundle 10 may achieve a nearly even power distribution among the inner and outer fuel rings, thus maximizing fuel utilization while minimizing performance issues. Moderation in the heavy water in the moderation region 22 may drive fission in the fuel elements 28b of the outer ring, while moderation in the light water coolant in the central flow passage 20 may drive fission in the fuel elements 28a of the inner ring. Balance between these two contributions to the lattice physics behavior may be characterized by the following lattice parameters: i ratio of the total cross sectional area of the coolant in the fuel bundle chamber 18 and the central flow passage 20 to the cross sectional area of the fuel elements 28a, 28b; ii ratio of the cross sectional area of the coolant in the central flow passage 20 to the cross sectional area of the coolant surrounding the fuel bundle 10 in the fuel bundle chamber 18; iii ratio of the moderator cross sectional area to the cross sectional area of the fuel elements 28a, 28b in one lattice cell ; and iv ratio of the cross sectional area of the moderator to the total cross sectional area of the coolant in one lattice cell.
The target for the ratio of outer to inner fuel power densities is 1 , the lattice CVR target is to be negative, and the k-infinity target is to be maximized. Based on the lattice scoping studies, the following ranges of parameters applied simultaneously were found to yield values for power density ratio, CVR and k-infinity that satisfied the targets for lattice physics performance: a coolant-to-fuel ratio of between approximately 2. Based on the relatively wide ranges in the moderator-to-fuel and coolant-to-fuel ratios, the total fuel mass in the fuel assembly may be varied significantly without adverse impacts to power density ratio, CVR or k-infinity.
However, other design constraints may restrict the variation in fuel mass in the assembly, such as the maximum allowable power density. In the example illustrated, the calandria is shown as being generally circular in axial cross-sectional shape. The plenum vessel 1 12 is configured to supply coolant to a plurality of the fuel channel assemblies 12 Figure 2B in the reactor and to extract the heated coolant from the fuel channel assemblies 12 after the coolant has been heated by flowing past the fuel bundles 10 Figures 1A and 1 B contained within the fuel channel assemblies The coolant is pressurized to a higher pressure than the moderator, and the plenum vessel 1 12 is a pressure vessel capable of withstanding the operating temperatures and pressures of the coolant.
In the example illustrated, the first plenum chamber is in fluid communication with each of the fuel channel assemblies 12 to allow coolant to flow between the first plenum chamber and each of the fuel channel assemblies Only a single fuel channel assembly 12 is illustrated for clarity.
One or more fluid ports may be provided in the plenum vessel to allow coolant to flow in and out of the first plenum chamber In the example illustrated, the plenum vessel includes four ports spaced apart from each other around the sidewall The second plenum includes a second plenum chamber that is bounded by a bottom wall , a sidewall and an upper wall or lid In this configuration, the second plenum chamber is self-contained and is fluidly isolated from the first plenum chamber so that fluid within the second plenum does not mix with fluid in the first plenum chamber In this configuration, a gap around the perimeter of the second plenum , between an outer surface of the second plenum sidewall and an opposing inner surface of the first plenum sidewall 1 16, provides a fluid flow path around the outside of the second plenum to link the upper portion and lower portion In this configuration, a coolant flow path is provided so that coolant fluid may flow between the first plenum chamber and the second plenum chamber via the fuel channel assemblies Optionally, some or all of the fuel channel assemblies 12 may be detachably coupled to the bottom wall using any suitable connector.
In this configuration, the first plenum chamber is in fluid communication with each fuel channel assembly 12 to supply coolant and the second plenum chamber is in fluid communication with each fuel channel assembly 12 to collect the heated coolant fluid. The coolant flows from the first plenum chamber in a downward direction through the central flow passage 20 Figures 1A and 1 B of the fuel channel assemblies 12, and flows to the second plenum chamber in an upward direction through the fuel bundle chambers 18 Figures 1A and 1 B of the fuel channel assemblies The fuel bundles 10 are positioned within the fuel channel assembly 12 in the flow path of the coolant flowing in the upward direction Optionally, the plenum vessel 1 12 may be configured to handle liquid coolants, gas coolants, mixed-phase coolants and supercritical coolant conditions.
Optionally, the inlet conditions may be selected so that the incoming coolant remains subcritical. This may help facilitate greater energy pickup from the fuel bundles 10 when the coolant flows through the fuel channel assemblies In other configurations, the outlet pressure may be between about 12 and about 22 MPa and may be greater than 26 MPa. Such temperature differences may impart significant thermal stresses in the lid , sidewal!
As it is located outside of the neutron field, the outlet plenum may be made from a variety of suitable materials, including, for example stainless steel and nickel-based super alloys. Alternatively, as the pressure difference between the plenums may be relatively small, the second plenum may be formed from materials that have desirable thermal properties, including, for example refractory materials and ceramic-based materials, instead of highly thermally conductive metals.
This may help improve the efficiency of a nuclear power generation station as the heated coolant may remain at a high temperature when it reaches the turbines. Alternatively, the heated coolant may be used to heat a secondary circuit, for example via a steam generator, and the turbine generators may be driven by steam in the secondary circuit.
Configuring the system to include a steam generator and secondary circuit may help increase the safety of the power generation system, but may reduce overall efficiency. The tubesheet 1 14 may also separate the reactor core containing fissile nuclear fuel from the non-core portions of the reactor. The tubesheet includes a plurality of apertures to accommodate the plurality of fuel channel assemblies 2. Portions of each of the fuel channel assemblies 12 are submerged in the moderation region The number, configuration and arrangement or pitch spacing of the apertures in the tubesheet 1 14 defined as generally horizontal distance between fuel channel axes within the lattice may be any suitable distance.
The pressure tube of each of the fuel channel assemblies may be sealed to the tubesheet , and provide both pressure and fluid separation between the moderator in the moderation region 22 and the coolant circulating within the fuel channel assemblies Adjacent to the bottom wall , and above the tubesheet , inlet ports and feeder conduits provide fluid communication between the first plenum chamber and the central flow passage 20 Figures 1 A and 1 B.
The inlet ports are arranged about the outer conduit 16, and the feeder conduits provide a fluid-sealed connection between the inlet ports and the central flow passage 20, while permitting flow of the heated coolant upwardly through the fuel bundle chamber The length of each fuel channel assembly 12 may be selected to be any suitable length that is compatible with other components of the reactor , and may be, for example, between about 1 m and about 10 m.
The axial length of the fuel bundle 10 within each fuel channel assembiy 12 may be any suitable length, and may be between about 0. Skip to main content. Companies House does not verify the accuracy of the information filed link opens a new window. Follow this company File for this company.
Company status Active. Company type Private limited Company Incorporated on 14 March Accounts Next accounts made up to 31 July due by 30 April Last accounts made up to 31 July Confirmation statement Next statement date 14 March due by 28 March Last statement dated 14 March
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