The Omaha Public Power District (OPPD) expects to carry out its Containment Internal Structures (CIS) project this fall to bolster the structural support under select plant components at the Fort Calhoun nuclear station in Nebraska.
The project is being carried out as part of the refueling and maintenance outage at Fort Calhoun this fall, OPPD said in its recent online newsletter, The Wire.
The project is meant to increase the structural support under select plant components, specifically two safety injection tanks. In addition, two beams will benefit from the added support columns under them.
The CIS project has no bearing on the containment building itself, OPPD said in the newsletter.
During the spring 2015 refueling outage, contractors from an Omaha-based 3D computer modeling company developed interactive, virtual maps of the entire containment structure. The CIS project team then used the maps to perform virtual “walk-throughs” of the containment structure without setting foot inside, OPPD said.
Previous CIS column designs relied on casting concrete around rebar, with a significant amount of supporting work inside containment. This presented issues of time, dose and cost.
Additional design refinements helped engineers come up with a novel solution: encasing the steel beams in concrete.
This approach reduced the complexity of the installation while retaining column strength. While the structure is already safe and secure, the concrete outer shell of the beams will reduce heat fluctuations that the steel could experience. The approach has been used successfully in other industrial, non-nuclear scenarios, OPPD said.
Fort Calhoun is a roughly 500-MW pressurized water reactor (PWR) in Washington County, Neb. Its primary water source is the Missouri River.