Failure analysis on abnormal leakage between tubes and tubesheet of spiral-wound heat exchanger for nuclear power plant

Abstract

In order to ensure the safety and reliability before actual operation in the nuclear power plant, the reliability test, i. e. bench test was parallelly carried out on two spiral-wound heat exchangers. During the test, both of the two heat exchangers suddenly failed. In our previous paper, the root causes analysis and mechanisms discussion were carried out on one of the spiral-wound heat exchangers, and concluded that the stress corrosion cracking induced by the interaction between inappropriate fabrication and aggressive environment upon the susceptible material was the root cause; while in the current paper, the abnormal leakage near the junction between the heat transfer tubes and the tubesheet of the other spiral-wound heat exchanger was investigated. The obtained results indicated that the interactive effect of crevice corrosion and stress corrosion cracking was the root cause of the failure, which was resulted from multiple factors including design, fabrication, surface treatment and operation. Then the failure mechanism was discussed in detail and the relevant countermeasures were put forward to prevent the similar failure cases occurring again. The achievement of this paper was expected to provide useful experience and suggestion for safe management of spiral-wound heat exchangers in the future.