MORE CONCRETE FRACTURES AT REACTOR BUILDING AT CRYSTAL RIVER UNIT 3 NUCLEAR POWER GENERATOR
Crystal River is a small town on Florida’s West Coast, and is one of only three nuclear electric power generating stations in the State. This article will review the nuclear plant, its history, and current condition. It has been in cold shutdown since September 26, 2009, for repair and maintenance. The ongoing repair operation is the interesting part of the story.
Atomic power was in its infancy in the United States in the 1950’s when the U. S. Government began testing various reactor designs at the National Reactor Testing Station [NRTS] in Idaho Falls, Idaho. This facility was operated by the U.S. Military in order to produce functional reactor designs for various uses in defense installations, as well as one strange project to build a nuclear-powered aircraft. A good source of information on this rather bizarre test facility is Atomic America, by Todd Tucker, Simon and Schuster, 2009. The nuclear reactor design used at Crystal River Unit 3 came out of this original military reactor prototyping and testing at Idaho Falls, and the specific Crystal River design dates back to the 1960’s. Babcock and Wilcox, a well-known engineering and construction firm headquartered in Charlotte, NC, produced the plant design and managed the construction for Florida Power Corp., as it was named back in the 1970’s.
Crystal River Unit 3 is a typical electric generating station, using steam-driven turbines connected to alternators (AC electric generators) to produce electricity. This basic steam power process has been in use since the late 1800’s when steam-driven turbines were first used to power ships by turning their propellers. The primary difference between this nuclear-powered electric generating station and a coal-fired boiler plant is the nuclear reactor. The reactor is sealed inside a pressurized water vessel (container) which produces high temperature pressurized water. This high pressure water is passed through a heat exchanger or “steam generator,” which produces non-radioactive steam, and which is, in turn, passed through the giant steam-driven turbines used to directly rotate the alternators which generate the electricity. The Unit 3 nuclear reactor vessel and the heat exchangers or “steam generators” are housed in a sealed “containment” structure or building, which has an access hatch for personnel along with small tools and minor equipment to pass through. This is the cylindrical “building” seen in the photos of the Unit 3 nuclear generating station. In 1975 I was fortunate to go on an engineering field trip to this construction site when I was a student at the University of Florida College of Engineering. The site superintendant guided our “tour,” and was a rather tall individual who had just lost a leg in a construction accident at the plant. He was obviously still in a considerable amount of pain, but carried on anyway. I distinctly remember him telling the group that once the containment building was completed, all of the large machinery and nuclear reactor inside the containment building would have to stay there for the life of the power plant. The access hatch opening was too small to allow complete removal and replacement of the nuclear reactor or the “steam generators.” However, the nuclear reactor requires periodic replacement of the nuclear fuel rods, so personnel must be able to access this equipment on a regular basis through the circular access hatch. Reports from the Nuclear Regulatory Commission [NRC] and associated diagrams show that the electricity-producing turbine-alternators are housed in a separate building adjacent to the nuclear reactor “containment” building. The diagrams (some in the slide show with this article) also show that there is a spent fuel storage area in a separate structure adjacent to this nuclear reactor “containment” building. The Babcock and Wilcox design is quite different than the General Electric Mark 1 nuclear generating station design used in Japan at Fukushima.
Now the dilemma – sometime in 2007 or 2008, the management team at Progress Energy determined that the two original heat exchangers or “steam generators” housed in the Unit 3 reactor containment building would have to be replaced, in part due to the planned request for license extension to year 2036 for the plant. These are the original heat exchangers or “steam generators” which were never supposed to be removed from the containment building. Plans were prepared to cut a large access opening in the side of the containment building so this work could be accomplished. The work commenced in 2009, with removal of a 25 ft. by 27 ft. section of concrete in the upper part of one cylindrical section of the reinforced concrete “containment” building. [See photos in slide show.] Steel tension rods had to be cut, and during the removal of this concrete wall section the inspectors noticed that the existing concrete wall adjacent to the new access opening had fractured, resulting in a fissure or split inside the concrete wall of the structure. Work was halted (in 2009), plans were revised, public meetings were held, and work resumed, including removal and replacement of a larger section of existing cylindrical building wall. The tensioned steel reinforcement of a concrete building behaves unpredictably when the tension steel is cut and concrete is removed.
So now, in 2011, as a larger work area in the cylindrical building wall was being readied for concrete placement, workmen noticed a second, additional wall fracture in an area previously thought to be stable and structurally sound. Work was again stopped, the anticipated work completion date of April 2011 was thrown out, and new investigations are under way (as of March, 2011) to determine the cause and extent of this newly-discovered wall fracture. These are not the “hairline cracks” referred to in NRC documents which are linked in this article. A final completion date for this ongoing maintenance operation is presently indeterminate.
According to information from Suzanne Grant of Progress Energy, the company intends to ask the NRC to license this Unit 3 generating station for an additional 20 years past the existing license expiration date of 2016. That would put the end-of-life date for this plant at year 2036, making the generating station 60 years old when it is finally closed down. As one might imagine, there are all sorts of complications associated with keeping a nuclear reactor operating for 60 years, and only time will tell if this extreme feat of technological maintenance can actually be accomplished.
Spent nuclear fuel “rods” for Unit 3 are kept in a separate building located adjacent to the reactor “containment” building, as described earlier. These “rods” are packed in bundles and are then submerged in boron-treated water pools, 40 ft. deep, with a 25 ft. deep water cover on the bundles. All of the spent fuel “rods” are kept at the plant site, now nearly 35 years worth. The company is planning to keep all 60 years worth of existing and future spent fuel rods on site by using a dry cast concrete storage system for the older, cooler “rods” as they age, thus allowing hotter “rod” bundles to be kept in the existing water storage pools. This arrangement is common in the nuclear power generating industry, and is similar to the spent fuel pool at Fukushima, located outside their reactor buildings. Crystal River Unit 3 has the three separate systems to supply water to the spent fuel pool including main pumps, diesel electric back-up, and as a last resort, battery pump backup. The primary difference between Unit 3 and Fukushima is that Unit 3 is not located on a known earthquake fault line, and has already experienced several hurricane high-water events.
This is the end of Part One of the article. In Part Two, we will examine the emergency evacuation plans for the Tampa Bay area and discuss the various players involved with those evacuation plans, including County Emergency Operation
s, MacDill AFB, County Sheriffs, Tampa Police, and citizen groups such as Amateur Radio Emergency Services (ARES/RACES), etc.