RELATIONSHIP OF CARBURIZING POTENTIAL TO OPERATING TEMPERATURE LIMITATIONS IN SRE

Technical Report · Mon Jan 01 04:00:00 EST 1962

OSTI ID:4740661

Sinizer, D I; Pearson, E N

The effective carbon concentration of SRE sodium has now been reduced, by hot trapping, mechanical cleaning, and filtration, to a level where it will carburize Type 304 stainless steel to a surface carbon content of 0.4%. This is well below the operating limit for surface carbon, which is set at 0.5%. It is therefore recommended that the upper operating temperature limitation of 800 deg F at the claddingcoolant interface be removed. The cladding-coolant temperature limitation should be raised, in steps, to 930 deg F and then to 1060 deg F. The stepwise program is outlined here. With these higher temperature limitations, power level can be raised to 15 Mw, and then to 20 Mw, with a flow rate of 1400 gpm. Analysis of available information indicates that carbon in the SRE exists partially in a dissolved form, in which it is capable of carburizing stainless steel to a level dependent on time, temperature, and effective carbon level. Carbon also exists in a second phase particulate form, in which it is not available for carburizing stainless steel. Second phase carbon dissolves rapidly only when the sodium mixed mean temperature exceeds about 850 deg F. Therefore, most solution under present operating conditions occurs in the hot trap side stream, where the temperature reaches 1250 to 1300 deg F. Limiting carburization criteria are established for Type 304 stainless steel in sodium systems. If surface carbon is less than 0.5%, cladding life is infinite, from the standpoint of carburization. If surface carbon exceeds 0.5%, the limiting criterion is reached when the metallographically detectable case depth reaches 10% of the section thickness. No hazardous consequences, other than fuel element cracking under abnormal stress and operating conditions, are envisioned if carburization exceeds the established criteria. Even this condition would release no activity hazardous to operating personel or the general public. Chemical or metallurgical analysis of grab samples from the sodium system cannot be correlated with carburizing potential of carbon in sodium, at the present time, The only method applicable, at the present time, is by monitoring the carburization of tabs in the hot trap side stream during reactor operation. Carburizing potential appears to be independent of oxygen concentration, at least to about 50 ppm. (auth)

• Research Organization: Atomics International. Div. of North American Aviation, Inc., Canoga Park, Calif.
• DOE Contract Number: AT(11-1)-GEN-8
• NSA Number: NSA-17-017597
• OSTI ID: 4740661
• Report Number(s): NAA-SR-Memo-7804
• Country of Publication: United States
• Language: English

Related Subjects

CARBIDES
CARBON
CARBURIZATION
CLEANING
CRACKS
FILTERS
FUEL CANS
HIGH TEMPERATURE
LAYERS
LIQUID FLOW
LIQUID METAL COOLANT
METALLURGY
OXYGEN
QUALITATIVE ANALYSIS
QUANTITY RATIO
REACTOR TECHNOLOGY
REACTORS
SAFETY
SODIUM
SOLUTIONS
SRE
STAINLESS STEELS
STRESSES
SURFACES
TRAPS