Document Type

Annual Report

Publication Date

7-7-2004

Abstract

As indicated in the original proposal, the primary objective of this task was to evaluate the effect of hydrogen on environment-assisted cracking of candidate target structural materials for applications in spallation-neutron-target (SNT) systems such as accelerator production of tritium (APT) and accelerator transmutation of waste (ATW). The materials selected for evaluation and characterization were martensitic stainless steels including Alloy EP 823, HT-9, and Type 422 stainless steel. The susceptibility to stress corrosion cracking (SCC) of these materials were evaluated in neutral and acidic aqueous environments using smooth and notched tensile specimens under constant-load (CL) and slow-strain-rate (SSR) conditions. Further, the localized corrosion (pitting and crevice) behavior of these alloys was evaluated by electrochemical polarization technique. The extent and morphology of cracking and localized corrosion of the tested specimens were determined by optical microscopy and scanning electron microscopy (SEM).

The experimental program proposed in this task was refocused to evaluate the effect of molten lead bismuth-eutectic (LBE) on the corrosion behavior of similar target structural materials in the presence of oxygen. Since the Materials Performance Laboratory (MPL) at UNLV could not accommodate this type of testing, the LBE loop at the Los Alamos National Laboratory (LANL) is currently being used to contain the stressed test specimens to evaluate the SCC and localized corrosion (pitting and crevice) behavior of all three candidate alloys in the molten LBE environment. Since the magnitude of the applied load/stress during these tests could not monitored or controlled (as in conventional SCC experiments) in the LBE environment, the test specimens were self-loaded. Two types of specimen configurations, namely C-ring and U-bend, were used to perform these experiments. The results of SCC testing being conducted at LANL are not yet available. The stress of principal interest in both types of specimen is the circumferential stress. SCC tests using these types of self-loaded specimens have also been conducted at MPL in aqueous environments having neutral and acidic pH values at ambient and elevated temperatures.

Keywords

Eutectic alloys; Hydrogen; Lead-bismuth alloys; Lead-bismuth eutectic; Martensitic stainless steel – Cracking; Materials – Cracking; Metals — Effect of high temperatures on; Particle accelerators; Radioactive wastes — Transmutation; Spallation (Nuclear physics); Stress corrosion; Tritium

Disciplines

Materials Chemistry | Materials Science and Engineering | Metallurgy | Nuclear Engineering | Oil, Gas, and Energy

Language

English


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