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The mechanical properties of 316 stainless steel were measured at room temperature and at 1200 F during exposure to environments of air, helium and “clean” sodium. The test results were: Test: Cyclic strain / Environment: Air - Least cycles to failure; Environment: Helium - Most cycles to failure; Environment: Sodium - Between air and helium values. Test: Rupture / Environment: Air/Helium - No significant difference in rupture strenth; Environment: Sodium - Possible increase in ductility compared to air. Test: Creep / Environment: Air - Lowest rate; Environment: Helium - Highest rate; Environment: Sodium - Between air and helium values. Test: Tensile / Environment: Air/Helium/Sodium - 5 percent or less difference in tensile strength; 6 percent or less difference in yield strength. The small changes seen in the rupture, creep, and tensile tests, due to different environments, are considered insignificant when compared to overall variations between heats of stainless steel. The differences seen in cyclic strain tests reflect changes in material surface condition produced by environment.

The effects of air, helium, and sodium on the creeprupture properties of chromium-molybdenum carbon steel and type 316 stainless steel at 1100 and 1200 deg F, respectively, are shown.

The nineteenth in a series of progress reports (March 1962) on the status of physical properties study of stainless steel exposed to Na at 1200 nif- F is presented. Results of all the tests performed by the end of this report period (March 1962) for the physical properties of materials program are reported in tabular form. Changes recommended by the AEC Subcommittee are included. (H.G.G.)

I have read with great interest Professor K. C. Bullen's article on the constitution of the earth, etc., published in the January, 1960, issue of the Bulletin. There is a small error in the calculations on page 2, concerning the two spherical balls, A and B. The moment of inertia of the ball B is stated to be about 5/6 that of A.