Activists get nuclear-plant science all wrong

 

As a professor of nuclear engineering and an engineer who has worked in the nuclear field, I want to clarify misinformation in the March 1 story Critics: FPL playing risk with plant. Since 1979, when Hollywood splashed The China Syndrome onto the big screen, we nuclear engineers have watched as Americans have been subject to hair-raising descriptions of nuclear power plant accidents promoted by well-funded activists. They are very colorful, but typically loose with the facts.

More than three decades later, we find ourselves discussing different issues, but the commentary from these groups is no less irresponsible or incorrect.

Floridians should not fall for it.

The wild claims in this article were supported by activists rather than unbiased technical experts. The suggestion that a steam generator tube at the St. Lucie nuclear plant can “spew radioactive fluid” ignores basic understanding of a pressurized water reactor system and steam generator design.

Under certain conditions, these tubes could leak small amounts of water into another closed system, but they do not spew fluid externally. Even under the highly unlikely event of a leak, such a change would be detected immediately, and the plant would be shut down within minutes.

The article buried the fact that for a leak to actually occur, a tube wall would need to be worn down almost completely. The activists attempt to compare the St. Lucie plant to a California plant called San Onofre, which was shut down due to a phenomenon called “tube-to-tube wear.” It’s a flawed comparison.

In that plant, 134 steam generator tubes had more than 50-percent wear, while seven of the tubes had 100-percent wear because of tube-to-tube contact. FPL and the U.S. Nuclear Regulatory Commission have confirmed that there is no such tube-to-tube contact at St. Lucie. The depth of wear at St. Lucie is not analogous. The steam generators were different manufacturers and different designs. In fact, not one unbiased technical expert has suggested that what happened at San Onofre is plausible at St. Lucie. Rather, they have said exactly the opposite.

Those who have objectively studied this issue know that there is significant data showing that steam generator tubes can perform with up to 70-percent wear. Yet, in reality these tubes are “plugged,” or taken out of service before there is evidence of wear of 40 percent. From a technical perspective, this is conservative approach designed to head off the potential for an internal system leak.

The same critics claim that power retrofits increasing the output of a plant or “uprates” are like “pressing hard on the accelerator, even when you know the car has worn brakes.” This analogy is also misleading from a technical perspective. Today’s steam generators, such as those in the St. Lucie plant, are designed specifically to function under uprate conditions. These conditions were part of the safety review completed by credentialed experts at the U.S. Nuclear Regulatory Commission prior to granting St. Lucie’s license amendment allowing higher power levels.

It is true that there has been a significant amount of tube wear at St. Lucie Unit 2. Despite the opponents’ claims, however, it is not unusual to see greater tube wear early in the life cycle of a steam generator. This typically reduces over time, which appears to be the case at St. Lucie.

Based on publicly available information, only 155 of St. Lucie’s 18,000 steam generator tubes in Unit 2 have had to be plugged over the first seven years. These generators are built with significant margin, allowing the plant to operate at full power even when a significant number of tubes are taken out of service. There is no reason to believe that the St. Lucie steam generators will not be able to function safely as designed for quite some time.

As nuclear engineers and those responsible for public health and safety, we are forced to prove the accuracy of our conclusions and integrity of our data to multiple regulatory stakeholders. It’s too bad that the activists quoted in this article are not held to the same standards.

James S. Tulenko, is a professor emeritus in the Department of Nuclear and Radiological Engineering at the University of Florida. He has more than 40 years of experience with nuclear power plant design and operation, including tube wear on steam generators.

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