CRACKS in a condenser that caused commissioning problems at the Daya Bay nuclear power station will lead to a multi-million dollar addition of equipment at each of the two reactor units during this month's refuelling. The 21/2-month shutdown of Unit One for removal of the radioactive fuel rods and replacement of the third of them that are spent will start on December 17. That shutdown is scheduled to end on February 26, before the shutdown of Unit Two for the same process on March 10. The condenser is in the electricity generating part of the station, not the nuclear section. It cools the steam which has passed through the turbine, where electricity is generated. The 40,000 tubes of the condenser are cooled using seawater. If there are any cracks in the tubes, seawater can get in, which can then corrode the pipes in the loop, says Hong Kong Nuclear Investment technical adviser Jacques Pretti. There were strict guidelines for the sodium content of the cooling water, he said. 'Even if we have a very small ingress [of seawater] into the condenser we would exceed the criteria and would have to shut down the plant, or reduce the power and try to plug the leaking tubes,' he said. During commissioning, a damaged plate that holds the tubes in place had led to cracks forming in six of the condenser tubes, which are made of titanium. The sodium content of the water had exceeded the threshold and seawater had got into two pumps which had then failed to operate. The company decided then to buy an ion exchange column, or 'polishing plant' - to 'polish' the water by removing any salt in the form of sodium ions, said Dr Pretti. The company refused to give the exact equipment cost, saying only that it would be in the millions of dollars. The advantage of having the plant was that if there was a leak, a shutdown could be put off until a convenient time, such as low-demand times, he said. Pressurised water reactor designer and consultant Steven Sholly of California agreed.