Environmentally Assisted Cracking Initiation in High-Temperature Water

Abstract

Environmentally assisted cracking (EAC) is a very complex process that develops in materials that involve combining actions of environment and tensile loading. Crack initiation is the least explored stage and is not clearly defined. For this paper, current knowledge of crack initiation mechanisms was reviewed for three types of commercial structure materials exposed to high-temperature (HT) water coolants of power plants, namely ferritic low-alloy (LAS) and carbon (CS) steels, austenitic stainless (AS) steels, and nickel-based alloys. Physicochemical microprocesses engaged in the two earliest phases of the mechanism, the precursor and the incubation phases, are rather specific for each of these materials. In the latter, the slow growth phase, the crack development process passes into a sequence of repeating steps where the specific key microprocesses persist.

Feasibility of Safe Operation of WWER-440-Type Nuclear Power Plants for Up to 60–70 Years

“…The case has been thoroughly investigated, and the bolt has been replaced [33][34][35][36]. According to analysis [37] in There is only one case of known cracked baffle bolts in WWER-440 internals [33] found by volumetric ultrasonic examination. The damaged bolts could have cracked due to improper alignment and restricted thermal expansion.…”

“…The case has been thoroughly investigated, and the bolt has been replaced [33][34][35][36]. According to analysis [37] in the Czech Republic, the baffle-former bolts are the most susceptible subcomponent of reactor vessel internals. They are loaded by fatigue and IASCC.…”

“…Supporting the long-term operation research activities are taking place in all WWER-440 operating countries, see the examples for Finland [33,34,36], the Czech Republic [37,50], etc. 4.…”