CORROSION ANALYSIS: LOW-CAPACITY PUMP. Large Sodium Pump Study, Phase II. Page: 7 of 30
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REVIEW OF CORROSION DATA ON AUSTENITIC STAINLESS STEELS
Much of the early liquid-metal data cannot be applied to the evaluation of
materials for nuclear systems because the data were generated in static
capsules and low-velocity thermal convection loops. Oxygen levels in these
tests were either not clearly defined or were too high to be of value. Data
obtained in pumped loops indicated that corrosion rates are strongly depend-
ent on loop operating parameters such as sodium velocity, temperature
differences in the system, chemistry gradients (different materials in dif-
ferent parts of the system), and system geometry, as well as on the local
temperature and oxygen content of the sodium.
Of the corrosion data generated to date, the only applicable data are those
from the UKAEA1lI and G.E. programs. The test parameters are summarized
in Table 1. In addition to the austenitic stainless steels listed, various
ferritic steels [1, 2], and high-nickel  alloys were studied.
The principal observations were:
a. Corrosion occurs in the hot-leg regions of pumped-loop systems, and
deposition occurs in cold-leg regions.
b. The corrosion rates for all low-nickel alloys are similar.
c. After an initial period of a few hundred hours, the corrosion rates
became linear. The UKAEA work(I also reported an initial small
d. An increase in test temperature caused an increase in corrosion rate,
corresponding to an Arrhenius-type relationship.
e. An empirical equation was developed for the G.E. data and is given as:
R=V0884 Ox 1.156 exp (12.845 - 23,827) -( 0.00676 L )+ 2.26 (1)
I T+460 D 5 t+l
R = average rate of removal (mg/dm2/m to time t)
O = oxide level (ppm)
V = sodium velocity (ft/sec)
T = sample temperature (*F)
L/D = downstream factor (number of diameters a sample is downstream
in an isothermal region)
t = exposure time (months)
f. A 'downstream effect' was observed in both programs [1,2]. Specimens
at the inlet end of the hot leg corroded at a higher rate than speci-
mens further down stream due, presumably, to progressive saturation
of the sodium with corrosion products.
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Thomas, K.C. & Shiels, S. CORROSION ANALYSIS: LOW-CAPACITY PUMP. Large Sodium Pump Study, Phase II., report, October 31, 1970; Madison, Pennsylvania. (https://digital.library.unt.edu/ark:/67531/metadc1034653/m1/7/: accessed March 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.