Material selection and protection from environment-induced degradation

  • Environmental attack on exposed surfaces is an important consideration in the design of a SSC. The selection of the material of construction is a critical decision to protect the SSC from adverse environmental effects. Typical hazards are: Stress corrosion cracking (in stainless steels), surface corrosion (carbon steels), Galvanic corrosion, pitting corrosion, crack propagation from thermal shock, etc.
  • Attack on the internals of a SSC from generation of aggressive species during operation is another form of degradation which is routinely considered as a part of the Company’s design practice. A classic example of severe equipment damage from concentration of solutes produced from operation is the Inconel tubed steam generators in the light water reactor plants.

Holtec maintains a comprehensive information base of potential environmental damage mechanisms that is utilized in the selection of materials.

The operating mantra for our specialists is: “Let us devise the technical solution to an operating problem or deficiency in a SSC without recourse to a physical ‘mod.’”  In their quest for an effective and economical solution, our specialists are not reluctant to escalate the sophistication of the analysis model. Seismic analysis of SSCs provides a typical example: Upon finding that a static seismic analysis is unable to provide a satisfactory answer, a Holtec specialist’s team can invoke the response spectrum method, and if that does not work, then perform a direct time history analysis of the SSC. HGS views many physical modifications made to SSCs in operating plants can be averted (with significant associated savings) by utilizing more advanced and refined analysis techniques. In other words, pragmatic use of advanced analysis methods in the service of safe and economical design is the essence of HGS’ technical approach. Developing optimal solutions to technical problems that require insightful optimization is another forte’ of the Company’s engineering organization.