Quad Cities' new steam dryers project

(Taken from article in Nuclear News October 2005)
For the first time ever, Exelon performed the replacement of a pair of steam dryers.

Exelon Generation's Quad Cities nuclear power plant installed new steam dryers in the site's boiling water reactors earlier this year. Quad Cities, in Cordova, Ill., has two General Electric BWRs, each rated at 867-Mwe (net design electric rating). Unit 1 started commercial operation in February 1973 and Unit 2 in March 1973.

The installation project, which took place during outages at Unit 1 in April and Unit 2 in May, was a first for Exelon and its contractor, Barnhart Crane and Rigging. The utility-contractor team worked together on the off-site assembly of the steam dryers, transporting them to the site, removing and replacing siding from the reactor building, and designing, fabricating, and building a temporary platform and slide rail system that were used to get the dryers inside the reactor building. Once inside, the dryers were moved from a temporary containment airlock to the refueling floor for their eventual installation in the reactors.

The steam dryers, manufactured in Pennsylvania by GE, weigh 55 tons each. The width of each dryer is 20 ft 7 in., and the height is 17 ft 10 in. After manufacture, the dryers were transported in March in pieces to an assembly plant in Illinois. Once assembled, the dryers traveled 15, miles down the road aboard a hydraulic platform trailer to the Quad Cities plant.

The utility-contractor team focused on minimizing the project’s impact on plant activities. Seismic and tornado loads were important considerations for the team in the design and fabrication of the temporary platform, which had to be capable of supporting more than 110, 000 pounds. Once on the platform, the dryers were seated on a slide rail system that used hydraulics to transport each one into the airlock through a series of small moves, 30 inches at a time. The distance covered along the slide rail system was about 30 feet, almost an hour's worth of work. Clearances were as tight as a couple of inches for moving the dryers through the airlock doors. Tolerances were less than that for other parts of the job.

Steam dryers are used online in BWRs --not in pressurized water reactors. When wet steam is formed in a BWR, it leaves the core and goes through a steam separator, jut like in a PWR. But unlike a PWR, the steam in a BWR also goes through a steam dryer, where additional moisture is removed. The steam then proceeds to the turbine.

This was the first time Exelon had ever replaced steam dryers in any of its BWRs, and it was one of the first replacement jobs of its kind in the industry, according to a project manager.