The class 1 equipment is very important in the nuclear device, in the design and testing process required to carry out their stress and strain analysis, so as to ensure their safety.

一级设备在核设备中非常重要，在该设备的设计和调试的过程中需要对其进行应力与应变分析，从而确保其安全性。

youdao

As part of my job, I reported alarming inadequacies: in one case high-grade equipment (ASME III, class 1) was operated in nuclear power reactors with no accepted safety file, regardless of a previous accident and a half-dozen failures in achieving acceptable design results.

BBC: Can nuclear power ever be safe?