BWR pipe crack remedies evaluation

Conference · Wed Oct 01 04:00:00 EDT 1986

OSTI ID:6952979

Shack, W J; Kassner, T F; Maiya, P S; Park, J Y; Ruther, W E

This paper presents results on: (a) the influence of simulated BWR environments on the stress-corrosion-craking (SCC) susceptibility of Types 304, 316NG, and 347 stainless (SS); (b) fracture-mechanics crack-growth-rate measurements on these materials and weld overlay specimens in different environments; and (c) residual stress measurements and metallographic evaluations of conventional pipe weldments treated by a mechanical-stress-improvement process (MSIP) as well as those produced by a narrow-gap welding procedure. Crack initiation studies on Types 304 and 316NG SS under crevice and non-crevice conditions in 289/sup 0/C water containing 0.25 ppM dissolved oxygen with low sulfate concentrations indicate that SCC initiates at very low strains (<3%) in the nuclear grade material. Crack growth measurements on fracture-mechanics-type specimens, under low-frequency cyclic loading, show that the Type 316NG steel cracks at a somewhat lower rate (approx.40%) than sensitized Type 304 SS in an impurity environment with 0.25 ppM dissolved-oxygen; however, the latter material stops cracking when sulfate is removed from the water. Crack growth in both materials ceases under simulated hydrogen-water chemistry conditions (<5 ppB oxygen) even with 100 ppB sulfate present in the water. An unexpected result was obtained in the test on a weld overlay specimen in the impurity environment, viz., the crack grew to the overlay interface at a nominal rate, branched at 90/sup 0/ in both directions, and then grew at high rate (parallel to the nominal applied load). Residual stress measurements on MSIP-treated weldments and those produced by a narrow-gap welding procedure indicate that these techniques produce compressive stresses over most of the inner surface near the weld and heat-affected zones.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6952979
• Report Number(s): CONF-8610135-55; ON: DE87004934
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
210100* -- Power Reactors
Nonbreeding
Light-Water Moderated
Boiling Water Cooled
36 MATERIALS SCIENCE
360103 -- Metals &amp; Alloys-- Mechanical Properties
360105 -- Metals &amp; Alloys-- Corrosion &amp; Erosion
ALLOYS
BWR TYPE REACTORS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-NICKEL STEELS
CORROSION
CORROSION RESISTANT ALLOYS
CRACK PROPAGATION
CRACKS
EVALUATION
FRACTURE MECHANICS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS
MECHANICS
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NIOBIUM ADDITIONS
NIOBIUM ALLOYS
PIPES
REACTOR MATERIALS
REACTORS
STAINLESS STEEL-304
STAINLESS STEEL-316
STAINLESS STEEL-347
STAINLESS STEELS
STEELS
STRESS CORROSION
STRESSES
WATER COOLED REACTORS
WATER MODERATED REACTORS