Corrosion behavior of sodium-exposed stainless steels in chloride-containing aqueous solutions
- PDF / 2,652,813 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 35 Downloads / 229 Views
P. C. S. WUis Project Engineer, Materials Program, B. R. GRUNDY is Principal Engineer, Chemical Technology, and R. L. MILLER is Senior Engineer, Mass Transfer, Westinghouse Advanced Reactors Division, Madison, PA 15663. Manuscript submitted August 3, 1978.
METALLURGICAL TRANSACTIONS A
M A T E R I A L S AND SPECIMENS T w o types of stainless steel w h i c h had been e x p o s e d to s o d i u m w e r e studied in the present investigation. T y p e 316 SS tubing (5.84 m m O D , and 0.38 m m wall) w a s e x p o s e d in a r e g i o n of corrosion (hot leg of a forced convection s o d i u m loop constructed of stainless steel), while annealed T y p e 304 SS tubing (ii.I m m O D , and 0.51 m m wall) was e x p o s e d in a region of corrosion product deposition (cold leg of sodium/stainless steel loop). T h i r t y s p e c i m e n s in the f o r m of capsules w e r e manufactured f r o m each of the a b o v e materials. T h e capsules, s h o w n in Fig. I, were approximately 7.6 c m long, and w e r e designed with top and b o t t o m end caps. T h e caps provided a c c e s s for pressurization d u r i n g e x p o s u r e to water, in simulation of internal stresses experienced b y a fuel e l e m e n t due to fission gas. In addition, an insert w a s included in the capsule to r e d u c e stored e n e r g y during pressurization. T h e r e w e r e two subdivisions of the T y p e 316 SS s p e c i m e n s f r o m the s o d i u m corrosion region. Fifteen of the s p e c i m e n s w e r e e x p o s e d at 6 4 9 ° C in s o d i u m with less than I0 p p m o x y g e n content, and flowing at 2.1 m / s for 5000 h. T h e other fifteen s p e c i m e n s w e r e e x p o s e d in s o d i u m u n d e r the s a m e conditions except that the t e m p e r a t u r e w a s 718°C. T h e T y p e 304 SS s p e c i m e n s were m a d e of an econ o m i z e r tube (liquid s o d i u m heat exchanger) f r o m a nonisothermal dynamic sodium loop. As a result, t h e r e were sodium mass transfer deposits on the surf a c e . This heat transfer unit was subjected to a temperature gradient a c r o s s the tubing wall plus a temperature differential a l o n g its entire length. The temperature differential over the economizer length was from 440 t o 574°C. This economizer was exposed t o sodium (20 to 25 ppm oxygen) for 3800 h. Thereafter, it was sectioned with each length of tubing assigned a n u m b e r t o identify its original position within the economizer. Thirty specimens were fabricated from these m a r k e d pieces for the present investigation. T h e s e specimens were numbered according t o their parent m a t e r i a l which in turn had been identified as t o location within the eco-
ISSN 0360-2133/7910312-0319500.75/0 © 1979 AMERICAN SOCIETY FOR METALS AND THE METALLURGICAL SOCIETY OF AIME
VOLUME 10A, MARCH 1979-3 19
Fig. 1--Photograph of corrosion capsules.
nomizer. Therefore, results on specimen characterization can be r e l a t e d t o varying temperatures around the economizer.
The microstructure of the 649°C sodium-exposed Type 3
Data Loading...
