CORROSION ANALYSIS: LOW-CAPACITY PUMP. Large Sodium Pump Study, Phase II. Page: 19 of 30
This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
Further metal loss may be expected at high velocities because of mechanical
erosion. The impingement of the high-velocity fluid might cause localized
failure at the impeller surface, resulting in metal loss. The importance
of this problem is not yet known; but, an experimental program is being
planned to resolve this.
The Effect of Sodium Corrosion on Mechanical Properties
The effects of prolonged exposure to sodium on the mechanical integrity of
structural materials are unknown; but, several possibilities exist. Briefly
these can be listed as follows:
a. deterioration of strength due to thinning of component cross sections
b. structural changes caused by mass transfer, which can involve:
(1) selective leaching of specific elements from the hot-leg region,
for example, the removal of chromium and nickel to give a ferri-
tic surface structure and decarburization or de-nitriding of
(2) carburization; and
c. grain boundary penetration.
Since the operating temperature and oxygen level will be low, it is not
expected that the mechanical integrity of the pump will be significantly
effected. The estimated corrosion losses given in Table 2 should not effect
the pump components, since they represent an extremely small percentage of
the total component thickness. Any affected layer formed by selective
peaching will again be small compared with the total component thickness.
Because of the 900 F temperature, decarburization should be minimized. The
effect of decarburization on Type 304 stainless steel is to increase the
yield strength and elongation without significantly affecting the UTS and
impact properties[6). The short-term rupture strength and rupture life of
cold worked Type 304 stainless steel thin wall tubing were found to be
significantly lower after decarburization in sodium at 1300 and 1400*FL7J.
It must be emphasized that these data were generated at high temperatures
(1175 to 1400*F) and under extreme decarburizing conditions (Zr hot trapping).
Such changes will not occur under the pump operating conditions.
The Effect of Exposure Time on Mechanical Properties
Above 800*F, austenitic stainless steels are subject to sensitization, the
precipitation of chromium carbide in grain boundary regions. Generally,
the effect of sensitization on mechanical properties is to increase the
ultimate strength and yield stress and decrease the elongation and impact
properties. The magnitude of these changes in mechanical properties is a
Here’s what’s next.
This report can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Report.
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/m1/19/: accessed March 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.