EFFECT OF HEAT FLUX ON THE CORROSION OF ALUMINUM BY WATER. PART III. FINAL REPORT ON TESTS RELATIVE TO THE HIGH-FLUX ISOTOPE REACTOR

Technical Report · Wed Dec 20 04:00:00 EST 1961

DOI:https://doi.org/10.2172/4826330· OSTI ID:4826330

Griess, J. C.; Savage, H. C.; Rainwater, J. G.; Mauney, T. H.; English, J. L.

The effect of very high heat fluxes on the corrosion of 1100 and 6061 aluminum alloys by water was investigated. The test conditions generally simulated those expected to exist during operation of the High-Flux lsotope Reactor. At heat fluxes between 1 and 2 x l0/sup 6/ Btu/hr-ft/sup 2/ and with coolant temperatures and velocities in the ranges of 13l to 250 deg F and 3l to 51 fps, respectively, a layer of boehmite ( alpha Al/sub 2/O/sub 3/- H/sub 2/0), which has low thermal conductivity, formed on the water-cooled aluminum surfaces during test. When only relatively thin films formed, the boehmite adhered tightly to the aluminum, but in those cases where relatively thick films formed, some boehmite spontaneously spalled from the surface. The rate at which the boehmite formed on the surface (and consequently the rate at which the aluminum temperature increased) was a function of the temperature at the specimen-water interface and the pH of the coolant. The lower the temperature and the lower the pH (in the range of 5.0 to 6.5 with HNO/sub 3/), the lower the rate of corrosion- product formation. Within the ranges investigated, pressure and flow rate were without effect, and the same results were obtained with 6061 and 1100 , aluminum. In those cases where the pH of the coolant was adjusted to 5, corrosion penetration was uniform and even under the most severe conditions did not exceed l.5 mils in 10 days. When the test conditions were such that the rate of oxide formation was high and oxide spalled from the surface of the specimen, localized attack of the aluminum in the form of subsurface voids extending several mils into the metal was always observed. From the experimental data, fluid-film heat- transfer coefficients were calculated and the thermal conductivity of the corrosion product was estimated. The fluid-film heat-transfer coefficients were in excellent agreement with those determined by others under similar conditions, and a value of 1.3 plus or minus 0.2 Btu/hr-ft/sup 2/ deg F/ft was obtained as the thermal conductivity of the corrosion-product film. The results indicate that from a corrosion standpoint either 6061 or 1100 aluminum could be used as cladding material for the High-Flux lsotope Reactor fuel elements, provided the pH of the coolant is maintained at 5.0 to 5.3 with nitric acid. Under test condstions simulating the most severe conditions anticipated during operation of the reactor (hot spot--hot channel) the maximum penetration observed was only 1 mil in 10 days. Although somewhat excessive temperatures are probable at hot spots due to a high rate of corrosion-product buildup, the great majority of the fuel plates will operate at reasonable temperatures. (auth)

• Research Organization: Oak Ridge National Lab., Tenn.
• DOE Contract Number: W-7405-ENG-26
• NSA Number: NSA-16-004499
• OSTI ID: 4826330
• Report Number(s): ORNL-3230
• Country of Publication: United States
• Language: English

Related Subjects

ACIDITY
ADHESION
ALUMINUM
ALUMINUM ALLOYS
ALUMINUM OXIDES
BOEHMITE
COOLING
CORROSION
FILMS
FLUID FLOW
FUEL CANS
HEAT FLOW
HEAT TRANSFER
HFIR
LAYERS
MATERIALS TESTING
METALS, CERAMICS, AND OTHER MATERIALS
NITRIC ACID
REACTION KINETICS
REACTORS
RESEARCH REACTORS
SURFACES
TEMPERATURE
THERMAL CONDUCTIVITY
THERMAL RADIATION
WATER
WATER COOLANT