South Texas Project Nuclear Power Plant Unit 1 Condenser: Scale Deposit Removal From 96,234 Condenser Tubes

South Texas Project (STP) Nuclear Power Plant was commissioned for operation in 1988. There are two units, Unit 1 and Unit 2, similar in design and capacity. Unit 1 is base loaded and produces 1,250 megawatts of power. There are 96,234 titanium condenser tubes, size 3/4” O.D. by 22 BWG in the multi-stage condenser. The tubes in the condenser were known to be fouled with calcium carbonate; however the extent of the fouling was unknown prior to the outage. The last effective cleaning on the Unit 1 condenser had been conducted five years ago in 2001 and only thin calcium deposits were noted at that time. It is well known that fouling of the condenser can have significant impact on unit operations: It increases unit heat rate and it can also limit unit generation capacity. However, due to the size and capacity of a condenser, and the heat transfer characteristics of a deposit type, fouling may go unrecognized until the deposition rate reaches an advanced level. As was the case at the South Texas Project Nuclear Power Plant in Wadsworth, Texas, where scale build up in the condenser tubes had not only developed, hardened, and thickened over time, but had also rendered many of the tubes completely blocked and useless. The tenacious scale, when combined with the large size of the condenser, made returning the condenser to its new and clean condition an extremely challenging project. A comprehensive cleaning project was planned and executed in September, 2006 cleaning all 96,234 titanium condenser tubes utilizing innovative scale cutting technology and mechanical scrapers. The completion of the project resulted in virtually all tubes being opened, clean, and available for service. This paper will acquaint you with the project from its conception to fruition and report the outcome.