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Page 1 of 9 DSAR-3.7 Nuclear Fuel Mechanical Design Rev 0 Safety Classification:
Usage Level:
Safety Information Change No.:
EC 69283 Reason for Change:
This section is being updated to reflect the permanent cessation of operations Fort Calhoun Station. The contents of this section have been changed to remove any information which is not applicable during decommissioning.
Preparer:
Tim Schulte Fort Calhoun Station
DSAR-3.7 Information Use Page 2 of 9 Mechanical Design Rev. 0 Table of Contents 3.7 Mechanical Design.......................................................................................................... 4 3.7.1 Deleted............................................................................................................... 6 3.7.1.1 Deleted............................................................................................... 6 3.7.1.2 Deleted............................................................................................... 6 3.7.1.3 Deleted............................................................................................... 6 3.7.1.4 3.7.1.4 Deleted................................................................................... 6 3.7.1.5 Deleted............................................................................................... 6 3.7.1.6 Deleted............................................................................................... 6 3.7.1.7 Deleted............................................................................................... 6 3.7.2 Deleted............................................................................................................... 6 3.7.2.1 Deleted............................................................................................... 6 3.7.2.2 Deleted............................................................................................... 6 3.7.2.3 3.7.2.3 Deleted................................................................................... 6 3.7.2.4 Deleted............................................................................................... 6 3.7.2.5 Deleted............................................................................................... 6 3.7.2.6 Deleted............................................................................................... 6 3.7.3 Nuclear Fuel Mechanical Design........................................................................ 7 3.7.3.1 Fuel Assembly.................................................................................... 7 3.7.3.2 Fuel Rods........................................................................................... 7 3.7.3.3 Poison Rods....................................................................................... 8 3.7.3.4 Part Length Poison Rods................................................................... 8 3.7.3.5 Hafnium Flux Suppression Rods........................................................ 8 3.7.3.6 Deleted............................................................................................... 8 3.7.3.7 Control Element Assembly................................................................. 8 3.7.3.8 Deleted............................................................................................... 9 3.7.4 Deleted............................................................................................................... 9
DSAR-3.7 Information Use Page 3 of 9 Mechanical Design Rev. 23 List of Tables Table 3.7-1 Mechanical Design Parameters 5
DSAR-3.7 Information Use Page 4 of 9 Mechanical Design Rev. 23 3.7 Mechanical Design A cross section of the nuclear fuel is shown in Figure 3.1-2. Mechanical design features of the nuclear fuel are described below. With the permanent defueled status of the station, the reactor vessel and internals no longer provide a design function.
Mechanical design parameters are listed in Table 3.7-1.
DSAR-3.7 Information Use Page 5 of 9 Mechanical Design Rev. 23 Table 3.7 Mechanical Design Parameters Control Element Assemblies (CEA's)
Type Framatome Design CEA Description Five(5) non-reconstitutable Full Length Poison Rods Attached to a Spider Poison Material B4C Pellets Ag-In-Cd Tips Sheath Material Inconel 625 Poison Length 125" Overall Length 152" Corner Element 4.64" Pitch Pre-Irradiated 0.95" CEA Rod Diameter CEA Weight 82+/-1 Total Operating 267 lbs.
CEA weight
DSAR-3.7 Information Use Page 6 of 9 Mechanical Design Rev. 23 3.7.1 Deleted 3.7.1.1 Deleted 3.7.1.2 Deleted 3.7.1.3 Deleted 3.7.1.4 3.7.1.4 Deleted 3.7.1.5 Deleted 3.7.1.6 Deleted 3.7.1.7 Deleted 3.7.2 Deleted 3.7.2.1 Deleted 3.7.2.2 Deleted 3.7.2.3 3.7.2.3 Deleted 3.7.2.4 Deleted 3.7.2.5 Deleted 3.7.2.6 Deleted
DSAR-3.7 Information Use Page 7 of 9 Mechanical Design Rev. 23 3.7.3 Nuclear Fuel Mechanical Design 3.7.3.1 Fuel Assembly Each fuel assembly consists of 176 fuel rods, five guide tubes, nine fuel spacer grids, and upper and lower end fittings. The structural frame of the assembly consists of the guide tubes, spacer grids and end fittings. The five guide tubes are attached to the end fittings. The spacer grids contained in the assemblies are attached to the guide tubes.
The fuel assembly upper end fitting serves as an attachment for the guide tubes and as the lifting fixture.
The fuel rod spacer grids maintain the fuel rod pitch over the full length of the fuel rods.
3.7.3.2 Fuel Rods The fuel rods consist of UO2 pellets, a compression spring and spacer discs, all encapsulated within a M5, Zircaloy-4 or ZIRLO tube.
The fuel cladding is slightly cold worked M5, Zircaloy-4 or ZIRLO tubing. The compression spring maintains the column in its proper position during handling and shipping. It also provides support for the clad in the plenum region to prevent local collapse.
The adequacy of the spring to perform its functions has been demonstrated in a series of long term creep collapse tests with plenum clad temperatures above those expected in the reactor.
There is one spacer at the top of the pellet stack in Westinghouse fuel rods and Framatome ANP fuel does not include a spacer.
The upper spacer on the Westinghouse prevents UO2 chips from entering the plenum region.
The plenum above the pellet column provides space for axial thermal expansion of the fuel column and for expansion of fission gas. The rod designs have been evaluated to ensure that the maximum end-of-life internal pressure will be less than the design limit.
DSAR-3.7 Information Use Page 8 of 9 Mechanical Design Rev. 23 Each fuel rod is internally pressurized with helium. The internal pressurization with helium improves the thermal conductance between the fuel pellets and the cladding, resulting in a decrease in fuel temperature with an attendant reduction in the release of fission products and an increase in the margins between operating temperatures and allowable thermal limits. In addition, by reducing the differential pressure across the clad, internal pressurization affords a substantial reduction in the adverse effects of fuel-clad interaction.
Some Fuel rods containing axial blankets have a reduced U-235 enrichment in the top and bottom ends of each fuel rod.
3.7.3.3 Poison Rods In some of the fuel assemblies, poison rods are included. The poison rods are mechanically similar to fuel rods except that they contain a poison (neutron absorber) integrated with the fuel.
Posion types used in the fuel at Fort Calhoun Station include B4C, IFBA, and Gadolina.
3.7.3.4 Part Length Poison Rods The part length poison rods (PLPR), when used, resided in guide tubes of selected peripheral assemblies. These rods no longer have any function, but are stored in the spent fuel pool.
3.7.3.5 Hafnium Flux Suppression Rods The Hafnium Flux Suppression Rods, when used, resided in guide tubes of selected peripheral assemblies. These rods no longer have any function, but are stored in the spent fuel pool.
3.7.3.6 Deleted 3.7.3.7 Control Element Assembly Each CEA is composed of five (5) full length control rods (i.e., fingers) assembled in a square array (i.e., spider), one (1) finger in the center capture tube (i.e., hub) and four (4) fingers at each corner of the spider. The overall length of each assembly is approximately 152 inches and the active length is 125 inches near the bottom of the rod.
DSAR-3.7 Information Use Page 9 of 9 Mechanical Design Rev. 23 The active length contains neutron absorbers (i.e., poison) in the Inconel tube and each finger is sealed by a welded end cap at the bottom and by a welded end fitting at the top. The upper 27 inches of nonactive length contains a gas expansion space to limit the maximum tube stress due to internal pressure buildup by the helium gas and moisture release from the B4C pellets during the reactor operation. All improved design and Framatome design CEA's include Ag-In-Cd in the tip to minimize the strains due to swelling induced by high neutron exposure during reactor operation.
3.7.3.8 Deleted 3.7.4 Deleted