DETERMINATION OF THE EFFECT OF HIGH EXCESS H$sub 2$SO$sub 4$ CONCENTRATIONS ON THE RADIATION-INDUCED CORROSION OF ZIRCONIUM AND TITANIUM ALLOYS IN 0.17 m UO$sub 2$SO$sub 4$

Technical Report · Tue May 01 04:00:00 EDT 1962

OSTI ID:4821162

Jenks, G H; Baker, J E

An in-pile loop experiment (L-2-l4) was carried out with the primary objective of studying the effects on Zircaloy2 radiation corrosion of a high concentration of excess H/sub 2/SO/sub 4/ in a uranyl sulfate test solution, Previous results obtained in in-pile autoclave experiments had shown a beneficial effect of H/sub 2/SO/sub 4/ additions. The effect could be correlated with a reduction of the U content of the heavy scales (and consequent reduction in local intensity of fission recoils) found on the surfaces of Zircaloy-2 specimens. Because Zircaloy-2 specimens exposed in in-pile loop cores are free of heavy scales of the type found in autoclavesa resuIt of transport to unirradiated surfaces-it was not obvious that acid addition would actually reduce the corrosion of Zircaloy-2 exposed in loops or in the practical reactor systems which the loops simulate. The solution was 0,l7 M in UO/sub 2/SO/sub 4/, 0.15 M in CuSO/sub 4/, and 0.4 M in H/sub 2/SO/sub 4/, in H/sub 2/O. Temperatures in the main stream and pressurizer were 280 and 300 deg C respectively. The loop was constructed of Ti, specimens of Zircaloy-2, Zr-l5 Nb, Ti-55A, and Ti6 Al-4 V were tested. The loop operated in beam hole HB2 of the LITR for 663 hr, during which time the reactor output was l530 Mwhr. The experiment was terminated when the loop pump failed. The corrosion rates of Zircaloy2 coupons exposed in the core of the loop varied from 2.6 mils per year (mpy) at 5.5 w/ml to 5.1 mpy at 12.8 w/ml. Zircaloy-2 corrosion rates at similar power densities in previous 280 deg C loop experiments employing solutions that were 0.17 M in UO/sub 2/SO/sub 4/ but only 0.02 to 0.03 M in excess H/sub 2/SO/sub 4/ and 0.015 M in CuSO/sub 4/ were significantly higher than those in the present experiment. Since the loop specimens were free of heavy scales of the types found in autoclaves but in general retained thin-appearing films, it is concluded that U sorption must occur on or in the films and that, in accordance with those autoclave experiments that demonstrated reduced U sorption and corrosion rates in solutions containing high concentrations of excess H/sub 2/SO/sub 4/, the reduced Zircaloy-2 corrosion rates exhibited in the loop experiment were also a result of decreased sorption of U in or on the thin films. (These conclusions have been substantiated by subsequent experiments.) The crystal-bar Zr coupons in the loop core exhibited corrosion rates in excellent agreement with the Zircaloy-2 data, However, the Zr- 15 Nb core coupons exhibited rates that were approximately 2.5 to 4.5 times greater than those observed for the Zircaloy-2 specimens at similar power densities, This is in contrast to data from previous experiments in which Zr15 Nb core coupons exhibited rates lower than those of the Zircaloy-2 coupons, (auth)

• Research Organization: Oak Ridge National Lab., Tenn.
• DOE Contract Number: W-7405-ENG-26
• NSA Number: NSA-16-017981
• OSTI ID: 4821162
• Report Number(s): ORNL-2943
• Country of Publication: United States
• Language: English

Related Subjects

ADSORPTION
ALUMINUM ALLOYS
COPPER SULFATES
CORROSION
FILMS
IN PILE LOOPS
MATERIALS TESTING
METALS, CERAMICS, AND OTHER MATERIALS
NIOBIUM ALLOYS
PRESSURE
PRESSURE VESSELS
SOLUTIONS
SULFATES
SULFURIC ACID
SURFACES
TEMPERATURE
TITANIUM
URANIUM
URANYL COMPOUNDS
VANADIUM ALLOYS
WATER
ZIRCALOY
ZIRCONIUM ALLOYS