Fuel rod bundle

R. Meyder, Solving the Conservation Equations in Fuel Rod Bundles Exposed to Parallel Flow by Means of Curvilinear-Orthogonal Coordinates, J. Comp. Physics, (17) 53-67,1975. 

Although current Monte Carlo codes have very powerful geometry routines, there e still many practical and. important systems that cannot be described without approximation. Two examples are a tank randomly filled with Raschig rings and a hexagonal array of fuel rod bundles. 

Critical heat flux measurement for SMART-specific UO2 fuel rod bundles,... 

Wide (or open ) fuel rod lattices, application of spacer grids to fix fuel rod bundles, fuel assemblies without shrouds (ducts), a cluster-type control and protection system, developed for light water reactors [XXIII-6]. 

S. Hagen, et al., "CORA Experiments on the Materials Behavior of LWR Fuel Rod Bundles at High Temperatures", 19th Water reactor Safety Information Meeting, Bethesda, October 28-30, 1991. 

S. Hagen, et al., Interaction in Zircalov UO2 Fuel Rod Bundles with Inconel Spacers at Temperatures above 1200 qC fPosttest Results of Severe Fuel Damage Experiments CORA-2 and CORA-31, KfK-4378, September, 1990. 

A large-scale CFD calculation is useful for the design of the Super FR and Super LWR. For example, the ACE-3D code for supercritical water calculation was developed for analysis of the 37-fuel rod bundle geometry. Validation of the code with 7-rod bundle experiments can be expected to reduce future R D work on fuel assembhes. The flow characterization within the RPV will also be made by CFD calculation. 

J. Yang, Y. Oka, Y. Ishiwatari, J. Liu and J. Yoo, Numerical Investigation of Heat Transfer in Upward Flows of Supercritical Water in Circular Tubes and Tight Fuel Rod Bundles, Nuclear Engineering and Design, Vol. 237,420-430 (2007)... 

The fifth component is the stmcture, a material selected for weak absorption for neutrons, and having adequate strength and resistance to corrosion. In thermal reactors, uranium oxide pellets are held and supported by metal tubes, called the cladding. The cladding is composed of zirconium, in the form of an alloy called Zircaloy. Some early reactors used aluminum fast reactors use stainless steel. Additional hardware is required to hold the bundles of fuel rods within a fuel assembly and to support the assembhes that are inserted and removed from the reactor core. Stainless steel is commonly used for such hardware. If the reactor is operated at high temperature and pressure, a thick-walled steel reactor vessel is needed. 

There are several hundred pressure tubes, each containing bundles of 28 fuel rods, 50 cm long. The coolant is at a pressure of around 10 MPa (1450 psia) and the D2O is at 310°C. Headers on each side of the vessel collect and return coolant from all the tubes. The 4-mm wall-thickness zirconium—4.5%... 

Uranium oxide [1344-57-6] from mills is converted into uranium hexafluoride [7783-81-5] FJF, for use in gaseous diffusion isotope separation plants (see Diffusion separation methods). The wastes from these operations are only slightly radioactive. Both uranium-235 and uranium-238 have long half-Hves, 7.08 x 10 and 4.46 x 10 yr, respectively. Uranium enriched to around 3 wt % is shipped to a reactor fuel fabrication plant (see Nuclear REACTORS, NUCLEAR FUEL reserves). There conversion to uranium dioxide is foUowed by peUet formation, sintering, and placement in tubes to form fuel rods. The rods are put in bundles to form fuel assembHes. Despite active recycling (qv), some low activity wastes are produced. 

Spent Fuel Treatment. Spent fuel assembhes from nuclear power reactors are highly radioactive because they contain fission products. Relatively few options are available for the treatment of spent fuel. The tubes and the fuel matrix provide considerable containment against attack and release of nucHdes. To minimi2e the volume of spent fuel that must be shipped or disposed of, consoHdation of rods in assembhes into compact bundles of fuel rods has been successfully tested. Alternatively, intact assembhes can be encased in metal containers. 

B8. Batch, J. M., and Hesson, G. M., Comparison of boiling burn-out data for 19-rod bundle fuel elements with wires and warts, HW 80391, G. E. Hanford Lab., Richland. Washington (1964). 

Rod bundle heat transfer analysis (Anklam, 1981a) A 64-rod bundle was used with an axially and radially uniform power profile. Bundle dimensions are typical of a 17 X 17 fuel assembly in a PWR. Experiments were carried out in a steady-state mode with the inlet flow equal to the steaming rate. Generally, about 20-30% of the heated bundle was uncovered. Data were taken during periods of time when the two-phase mixture level was stationary and with parameters in the following ranges ... 

Rowe, D. S, 1970, COBRA II Digital Computer Program for Thermal Hydraulic Subchannel Analysis of Rod Bundle Nuclear Fuel Elements, BNWL 1229, Battelle Northwest Laboratory, Richland,... 

Tong, L. S., 1967b, Heat Transfer in Water-Cooled Nuclear Reactors, Nuclear Eng. Design (5 301. (3) Tong, L. S., 1968a, An Evaluation of the Departure from Nucleate Boiling in Bundles of Reactor Fuel Rods, Nuclear Sci. Eng. 33 7-15. (5)... 

Waters, E. D., 1963, Fluid Mixing Experiments with a Wire-Wrapper 7-Rod Bundle Fuel Assembly, Rep. HW-70178 Rev., Hanford Lab., General Electric Co., Hanford, WA. (App.)... 

In this reactor type water is brought to its boiling point in the reactor core at a pressure of 70 bar. The resulting steam is directly fed from the pressurized reactor vessel to turbines. Fuel element bundles, each consisting of fuel rods in a lattice-like (6 x 6 to 8 x 7) array are to be found in the reactor core. The core fuel consists of - U-enriched... 

Fuel elements consist of a bundle of fuel rods... 

Purex process The actual reprocessing process begins with the cutting up of the fuel elements taken from entry basins. This can be carried out in two process variants cutting up in ca. 5 cm long pieces with rod shears, whereby initially the head pieces are separated off and the individual fuel rods withdrawn from the rod bundle, or direct cutting with hydraulic bundle shears. 

Figure 10. Fabrication flow sheet for rod bundles containing pelletized fuel. (After Ref. 10.)...

Figure 13. Each fuel rod consists of an assembly (often called a bundle ) of zirconium alloy tubes eontaining pellets of uranium oxide. Each rod, or bundle, is 495.3 mm (19.5 in.) long and contains about 15 kg (33 lb) of uranium oxide. (After Ref. 13.)...

Enriched UF is shipped to the plant for fabricating reactor fuel elements in monel cylinders whose size is determined from the content, so as to prevent accumulation of a critical mass. At the fuel fabrication plant UF is converted to UO or other chemical form used in reactor fuel. For light-water reactors the UOj is pressed into pellets, which are sintered, ground to size, and loaded into zircaloy tubing, which is filled with helium and closed with welded zircaloy end plugs. These individual fuel rods are assembled into bundles, constituting the fuel elements shipped to the reactor. Conversion of UFj to UO2 is described in Chap. 5. Extraction of zirconium from its ores and separation of zirconium from its companion element hafnium is described in Chap. 7. 

The lower end of each tube contains irradiated depleted UOj, the middle portion irradiated mixed depleted UO2 and PuOj, an upper portion irradiated depleted UO2, and the top a plenum to accommodate buildup of fission-product gases. The rod bundles are surrounded by a square or hexagonal stainless steel sheath to the top and bottom of which are attached end fittings to direct sodium flow in the reactor and to facilitate handling outside. Fuel assemblies for the radial blanket are of the same length but contain rods of larger diameter charged initially with depleted UO2. 

L. S. Tong, An Evaluation of the Departure From Nucleate Boiling in Bundles of Reactor Fuel Rods, Nuclear Sci. Eng. (33) 7-15,1968. 

H. C. Hopkins, Jr., Irradiation of a 19-rod-bundle fuel element. USAEC Rept. GA-3065, General Atomic, May 24, 1962. 

The general aim of the Mol 7C e3q>eriments in the BR2 reactor was to investigate the failure events and the inherent coolability conditions in a fuel bundle subjected to a local (partial) coolant flow blockage in the fissile zone. Operation of reactors with small number of failed fuel rods is desirable for economic reasons, but safety must nevei be prejudiced. Therefore the behaviour of failed fuel during accident is of primary interest and fuel simulation codes are essential in establishing an operational set of safety measures. The present MOL7C experiments fit clearly the current need for improved techniques which should help establish operational limits for fuel rods and develop higher performance materials. 

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