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Effects of High Thermal and High Fast Fluences on the Mechanical Properties of Type 6061 Aluminum on the HFBR
The High Flux Beam Reactor (HFBR) at Brookhaven National Laboratory (BNL) is an epithermal, externally moderated (by D2O) facility designed to produce neutron beams for research. Type 6061 T-6 aluminum was used for the beam tubes, pressure vessel, fuel cladding, and most other components in the high flux area. The HFBR has operated since 1965.
The epithermal, external moderation of the HFBR means that materials irradiated in different areas of the facility receive widely different flux spectra. Thus, specimens from a control rod drive follower tube (CRDF) have received () and thermal fluence, while those from a vertical thimble flow shroud received () and thermal. These numbers correspond to fast to thermal fluence ratios ranging from 0.05 to 1.9. Irradiations are occurring at approximately 333 K. The data indicate that the increase in tensile strength and decrease in ductility result primarily from the thermal fluence, that is, the transmutation of aluminum to silicon. These effects appear to be saturating at fluences above approximately thermal at values of 90,000 psi (6700 Kg/mm2) and 9%, respectively. The specimens receiving the highest fluence ratios appear to have less increase in tensile strength and less decrease in ductility than specimens with a lower fast to thermal fluence ratio and the same thermal fluence, suggesting a possible beneficial effect of the high energy neutrons in preventing formation of silicon crystallites.
radiation, aluminum alloys, thermal fluence effect, high flux research reactors
Weeks, John R.
Senior metallurgist, Brookhaven National Laboratory, Upton, NY
Czajkowski, Carl J.
Research engineer, Brookhaven National Laboratory, Upton, NY
Tichler, Paul R.
Reactor safety evaluation group leader, Brookhaven National Laboratory, Upton, NY