======================================================== April 18, 2003, 4:00PM A unit of nuclear plant is shut down By MICHAEL DAVIS Houston Chronicle Unit 1 of the South Texas Project nuclear plant near Bay City is shut down indefinitely after some residue from reactor coolant fluid was found on tubes near the bottom of the reactor, plant officials said Friday. Bay City is about 50 miles southwest of Houston. Theradioactive boric acid residue -- described by the company as about the size of one-half of an aspirin -- was discovered a week ago when the unit was shut down for scheduled refueling and maintenance The water flowing through the reactor to cool it contains boric acid. The powdery material was located on the outside of two instrument guide tubes where they enter the bottom of the reactor vessel. These contain instruments that measure reactor operations. "We found two very minor indications of a slight seepage at the bottom of the reactor vessel and are in the process of determining the root cause and to fix it," said Ed Halpin, plant manager for STP. "Unit 1 will not be returned to service until the problem is solved." Halpin could not say how long the repairs will take, but added that it will not have any effect on power consumers. STP officials are working with the Nuclear Regulatory Commission, which will review any plan for corrective action before it is put into place. "The unit is shut down and there is no danger to the public," said Victor Dricks, spokesman for the NRC in Fort Worth. "We have been impressed with the aggressive response of the licensee and are closely monitoring the situation." While the seepage discovered was minor, gone unchecked it could have led to very serious problems, said Jim Riccio, nuclear policy analyst with Greenpeace in Washington, D.C. "The real concern here is that if they had not found the leak, the crack could have grown large enough that they could not have made up the coolant loss," Riccio said. "You lose enough coolant, you melt the radioactive fuel rods in the core. Early indications are that the seepage may have come from a weld where the tube enters the bottom of the reactor, Riccio said. He attended an NRC conference in Washington earlier this week at which initial information on the discovery of the seepage was disclosed. "It stirred a few people up," Riccio said. The NRC has been advising nuclear plants using Westinghouse reactors -- as STP does -- about so called "thimble tube thinning," for 15 years, according to an agency bulletin on the problem dated July 26, 1988. Thimble tubes run inside of the incore guide tubes where the residue was found. "Wear of the thimble tubes results in degradation of the reactor coolant system's pressure boundary and can also create a potentially non-isolable leak of reactor coolant," according to the bulletin. Unit 2 at the plant just south of Bay City is running normally. Each unit has the capacity to produce 1,250 megawatts of electricity. The reactor vessel is housed inside the concrete and steel-lined containment building. In the meantime, the plant has a team of engineers who have re-examined all of the instrument guide tubes, and no additional residue was found, the company said. In November of last year, Unit 1 had an unscheduled outage after operators noticed some problems with the secondary cooling system, Halpin said. The reactor was shut down manually. The plant was plagued with problems a decade ago. It was shut down for most of 1993 by the NRC and a new management team was brought in by Houston Industries, the operator at the time. Now, the plant is managed by the STP Nuclear Operating Co. It is owned by AEP Texas Central Co., Austin Energy, City Public Service of San Antonio and Texas Genco. from the NRC website: +------------------------------------------------------------------------------+ |Power Reactor |Event Number: 39754 | +------------------------------------------------------------------------------+ +------------------------------------------------------------------------------+ | FACILITY: SOUTH TEXAS REGION: 4 |NOTIFICATION DATE: 04/13/2003| | UNIT: [1] [] [] STATE: TX |NOTIFICATION TIME: 19:06[EDT]| | RXTYPE: [1] W-4-LP,[2] W-4-LP |EVENT DATE: 04/13/2003| +------------------------------------------------+EVENT TIME: 16:56[CDT]| | NRC NOTIFIED BY: RON GIBBS |LAST UPDATE DATE: 04/13/2003| | HQ OPS OFFICER: STEVE SANDIN +-----------------------------+ +------------------------------------------------+PERSON ORGANIZATION | |EMERGENCY CLASS: NON EMERGENCY |DAVID LOVELESS R4 | |10 CFR SECTION: | | |ADEG 50.72(b)(3)(ii)(A) DEGRADED CONDITION | | | | | | | | | | | +-----+----------+-------+--------+-----------------+--------+-----------------+ |UNIT |SCRAM CODE|RX CRIT|INIT PWR| INIT RX MODE |CURR PWR| CURR RX MODE | +-----+----------+-------+--------+-----------------+--------+-----------------+ |1 N N 0 Cold Shutdown |0 Cold Shutdown | | | | | | | +------------------------------------------------------------------------------+ EVENT TEXT +------------------------------------------------------------------------------+ | REACTOR VESSEL BOTTOM HEAD DEGRADED CONDITION | | | | "On 4/12/2003, during the Unit 1 11th (1RE11) refueling outage, an | | inspection was performed of the vessel bottom head. This bare metal | | inspection identified a potential leak indication at the head to penetration | | interface for Bottom Mounted Instrumentation (BMI) penetrations 1 and 46. | | There was a small amount of residue around the outer circumference of the | | BMI penetrations. No wastage was observed. Samples of the residue were taken | | and the area was cleaned with demineralized water. Chemical sample results | | available as of 1300 on 4/13/2003 are not conclusive; however, they have | | confirmed that the residue found at the Penetration 46 contains boron, | | indicating that this could be an RCS leak. The residue removed from | | Penetration 1 was characterized as 'gummy' and its composition is still | | under investigation. Additional exams are planned to confirm the likely | | origin of the residue and to determine the scope of any repairs. There has | | been no indication of RCS leakage observed at the BMI penetrations during | | previous operational cycles. This notification is being made in accordance | | with 10 CFR 50.72(b)(3)(ii)(A)." | | | | Unit 1 will remain in mode 5 until appropriate corrective actions are | | identified. The licensee informed the NRC resident inspector. | +------------------------------------------------------------------------------+ New York Times Extraordinary Reactor Leak Gets the Industry's Attention By MATTHEW L. WALD WADSWORTH, Tex., April 30 - Reactor experts around the country hope that there is something unique about Reactor No. 1 at the South Texas Project here. If not, the little crust of white powder that technicians found at the bottom of the reactor vessel, a discovery that has brought operations here to a halt for the indefinite future, could be the beginning of a broad problem for the nuclear power industry. The powder, which managers here repeatedly compare in volume to about half an aspirin tablet, is boric acid, which is used in reactor cooling water to soak up excess neutrons, and its presence under the vessel presumably means there is a leak. Highly corrosive when damp, boric acid has been found in the last few years on the lids of reactor vessels around the world. A plant near Toledo, Ohio, accumulated 900 pounds, some of which ate away a football-size chunk of steel in the vessel lid, leaving only a thin stainless-steel liner and bringing the plant uncomfortably close to accident. But until the discovery here, on April 12, nobody had ever seen a leak on the bottom. A leak in that location is far harder to repair, and would be harder to control if a significant hole developed in the vessel, although the chances of accident seem far smaller than they did in Ohio. "It is something different," said Gary Parkey, vice president of the South Texas Project Nuclear Operating Company, which runs the two reactors here. Measuring the problem and then resolving it will take new applications of technology, he said, adding with no evident pleasure, "We are at the cutting edge of this issue." Until the discovery, in an inspection during a routine shutdown for maintenance, the Nuclear Regulatory Commission believed that it understood the mechanism for leaks in reactor vessels. It assumed that such leaks were caused by an occurrence called stress corrosion cracking, which, after long periods of operation, develops in hard metals that are under strain and high temperature. Not long ago, the commission developed a formula combining temperature and years of operation, and used it to tell reactor operators around the country whether they needed to shut down promptly for inspection or could do the job at a more convenient time. But the South Texas Project, here amid beef cattle and wildflowers 90 miles southwest of Houston, is only 15 years old, and its reactors operate at a relatively low temperature. That raises the possibility that there may be a problem even with plants that scored well in the regulatory commission's formula, and have not been inspected. "If this turns out to be stress corrosion cracking, and there's nothing unique about it, then it raises questions about the validity of that equation," said Brian W. Sheron, the commission's associate director for project licensing and technical analysis. That would be bad news for the nation's 102 other commercial power reactors, which despite vast electricity deregulation have prospered in the last few years, by achieving new levels of reliability. The South Texas Project boasted last year that its Reactor No. 1 generated more electricity than any other in the nation in 2001, and ranked eighth among the 433 power reactors worldwide. A majority of the plant is owned by two commercial companies: Reliant Energy and an American Electric Power subsidiary, AEP Central Power and Light; an additional 44 percent is owned by the municipal utilities of Austin and San Antonio. The plant's operators underscore that they caught the problem early. "There was no puddle, no buildup of boric acid on the bottom," said the general manager, Ed Halpin. David Lochbaum, a nuclear safety engineer at the Union of Concerned Scientists, a group often sharply critical of nuclear operators, also pointed out that the leak had been discovered early, but in an inspection, he said, that was more thorough than the regulatory commission requires. "It does show the prudence of looking periodically in places you don't expect to have problems," he said, "rather than blindly assuming you're not going to have problems except where you're looking." One difficulty at the Ohio plant, Davis-Besse, was that management delayed taking the time to remove thermal insulation around the vessel lid to check for leaks. As a result, corrosion continued unnoticed for years. That corrosion has been a nightmare for the Davis-Besse owners, keeping the plant shut for 14 months so far and probably some months to come. At both plants, the leaks occurred in places where the builders had installed "penetrations" of the vessel. At Davis-Besse, those penetrations allowed control rods to enter the core (to shut the reactor) and to be withdrawn (to start it up). Here, the penetrations are smaller, for dozens of pencil-size detectors that are pushed up into the core to measure the flow of neutrons, the subatomic particles that sustain the chain reaction. The leak apparently involves two of these penetrations. The safety implications of the problem seem manageable. Even if the reactor were to have spit out a tube through which a neutron detector enters, the hole would have been only 1.5 inches in diameter, well within the capacity of emergency pumps to keep up with. And though water in the reactor was kept at a pressure of 2,250 pounds, it is not clear that the reactor had been anywhere near to ejecting a tube by the time the boric acid was discovered little more than two weeks ago. Still, while managers here do not yet know the cause of the leak, or precisely how they will repair it, experts say the job will be complicated and will involve significant radiation hazards. The reason is that after months or years of sitting in the core, neutron detectors are intensely radioactive. If the fuel of Reactor No. 1 is removed, as operators expect for this repair, then the detectors will most likely rest at the bottom of the vessel, since they are not designed to be pushed into the middle of the reactor unless the fuel, and its associated hardware, are present. Mr. Halpin, the general manager, said engineers were working on a way to leave the probes in the middle of the vessel even with no fuel present. But if they rest at the bottom, then a technician working to repair the leak there could, in just a few minutes, receive from them as large a dose of radiation as the industry allows a worker in a year. Plant managers say they presume that the leaking parts are a pair of welds, each connecting one tube to the stainless-steel liner inside the vessel. But that place is too hard to reach for repairs, so they plan a weld on the lower surface, where the tubes exit the vessel, six inches outside the liner. The problem is that this would permanently leave cooling water with the corrosive boric acid in contact with the vessel wall, which is not stainless but instead plain old carbon-steel, which can corrode. Not only would the corrosion itself be a problem, but particles from the resulting rust could do damage as they floated around the reactor. The managers, however, argue that the volume of exposed carbon-steel would be very small, and that the temperature during operations is too high to allow corrosion anyway, a point on which they will have to satisfy the Nuclear Regulatory Commission before they can proceed. Members of the commission's staff will discuss the problem with the managers at a public meeting in Washington on Thursday. In the meantime, representatives from two associations of reactor operators, and from five nuclear plants, have visited here and are watching carefully. ======================================== ============================================= Austin Statesman June 6, 2003, 1:14PM Nuke plant's tiny leaks may have started four years ago By MICHAEL GRACZYK Associated Press Writer © 2003 The Associated Press Tiny cracks detected in one of the two reactors at the South Texas Project nuclear plant are so small it may have taken as long as four years before they manifested themselves as a noticeable leak, plant officials said Friday. "What appears to have happened, and based on the sample that was taken, these cracks initiated probably on an average of maybe four years ago and because they're so small and the amount of leakage so very small ... so minute, it just took really that long for any water to seep down in this area to be visible at the bottom of the vessel," Ed Halpin, general manager of the plant about 90 miles southwest of Houston near Bay City, said. Plant officials Thursday were in Rockville, Md., to discuss their findings and proposed repairs at a meeting of the Nuclear Regulatory Commission. "The real story there is not so much what was found, but what was not found," Halpin said. "We found no other cracks or anything that would give us any concern on the other penetrations. "Everything else was clean." Unit 1 of the twin reactor South Texas Project Electric Generating Station already was idled in March for routine refueling and maintenance when an inspection April 12 detected a tiny deposit containing boric acid on the bottom of the containment area of the reactor vessel. The residue was described as about half the size of an aspirin. "I think our initial inspection criteria worked," Halpin said. "We found it. It didn't find us." The small vertical cracks, known as "axial" cracks, were detected in two of the 58 instrumentation tubes inside the reactor vessel, specifically the No. 1 and No. 46 tubes. Instruments within the tubes measure the operations of the reactor. Robert Gramm, section chief section in the NRC group responsible for licensing activities at South Texas, agreed no other cracks have been found so far during numerous tests but that experts are continuing to try to determine what caused the problem in the first place. "At this point, several factors could be causing these cracks, from initial fabrication, possibly grinding or welding defects," he said Friday. "There could be some stress corrosion cracking going on or even some fatigue. There's multiple causal factors that haven't been isolated. They don't know what the true cause is." Framatome ANP, a Lynchburg, Va.-based nuclear plant services company, is developing the repairs, which will involve replacing a portion of the instrumentation tube, Halpin said. "We're in the process of conducting the mockups," he said. "We'll work through our repair over the next month. The bottom line is to do it right. So we're doing some extensive practicing and then we'll get out into the field shortly. "It is a procedure that is fairly extensive. It's one that our team will be ready for, though." Gramm described the repair as a "half-nozzle technique." "They basically go in and do some machining and remove the bottom half of a nozzle and replace it with upgraded material and re-weld that," he said. While similar repairs have been performed at other nuclear plants, the difference here is that it's being done at the bottom of a reactor vessel, Gramm said. Halpin said completion of the repairs should allow the plant to get back into operation late in the summer. Gramm said the goal was realistic "based on what we know today." "But more information will be coming to light between now and late summer and it's hard to predict what we might find out," he added. The two reactors produce 2,500 megawatts of electricity and serve more than 1 million homes in south central Texas. Unit 1 went into service in August 1988. Unit 2, which remains running, went into operation 10 months later. ============================================= June 6, 2003 NYTimes.com > National Repair Plan for Reactor With Leaks By MATTHEW L. WALD ROCKVILLE, Md., June 5 Ñ The managers of a Texas nuclear plant with two leaks at the bottom of its reactor vessel told the Nuclear Regulatory Commission today that they were backing away from their top theory on how the leaks developed. But, they said, they were nearly ready to fix them anyway. The operators of the plant, called the South Texas Project, 90 miles southwest of Houston, also told the agency staff that some residue left by the leaks was more than four years old and possibly much older. Previously, they had said the residue was not visible when the reactor was inspected last year. The leaks are in 2 of 58 nozzles on the underside of the reactor, which were installed to let operators push monitoring instruments into the nuclear core. The leaks were discovered when the plant was shut down for refueling in late March. At first, plant managers were inclined to believe that the leaks had been caused by a phenomenon in which the cooling water attacks metal that is under strain. But careful examination of the metal found flaws in some areas that had not been exposed to the water. The nozzles cannot be fully replaced because they are welded from the inside of the vessel. The managers' repair plan involves cutting off the portion of each nozzle that has the cracks, inserting a length of replacement pipe and welding it to the outside of the vessel. Leaving a gap between the old part of the nozzle and the replacement part, though, will allow the boron-laden cooling water to get access to areas that are not protected against corrosion. The Nuclear Regulatory Commission has approved "half-nozzle repair" for some structures at nuclear plants, but not for a reactor vessel. David Lochbaum, a nuclear engineer at the Union of Concerned Scientists, a group that often criticizes nuclear operators, said the two tubes so far had not presented a major safety problem because they leaked, leaving obvious deposits of boron, before they could break. If the proposed fix eliminates leaks but accelerates corrosion, Mr. Lochbaum said, "the first sign of a problem will not be a white residue but a loud bang and the rapid loss of water from the reactor vessel." ============== Houston Chronicle June 6, 2003, 1:14PM Nuke plant's tiny leaks may have started four years ago By MICHAEL GRACZYK Associated Press Writer © 2003 The Associated Press Tiny cracks detected in one of the two reactors at the South Texas Project nuclear plant are so small it may have taken as long as four years before they manifested themselves as a noticeable leak, plant officials said Friday. "What appears to have happened, and based on the sample that was taken, these cracks initiated probably on an average of maybe four years ago and because they're so small and the amount of leakage so very small ... so minute, it just took really that long for any water to seep down in this area to be visible at the bottom of the vessel," Ed Halpin, general manager of the plant about 90 miles southwest of Houston near Bay City, said. Plant officials Thursday were in Rockville, Md., to discuss their findings and proposed repairs at a meeting of the Nuclear Regulatory Commission. "The real story there is not so much what was found, but what was not found," Halpin said. "We found no other cracks or anything that would give us any concern on the other penetrations. "Everything else was clean." Unit 1 of the twin reactor South Texas Project Electric Generating Station already was idled in March for routine refueling and maintenance when an inspection April 12 detected a tiny deposit containing boric acid on the bottom of the containment area of the reactor vessel. The residue was described as about half the size of an aspirin. "I think our initial inspection criteria worked," Halpin said. "We found it. It didn't find us." The small vertical cracks, known as "axial" cracks, were detected in two of the 58 instrumentation tubes inside the reactor vessel, specifically the No. 1 and No. 46 tubes. Instruments within the tubes measure the operations of the reactor. Robert Gramm, section chief section in the NRC group responsible for licensing activities at South Texas, agreed no other cracks have been found so far during numerous tests but that experts are continuing to try to determine what caused the problem in the first place. "At this point, several factors could be causing these cracks, from initial fabrication, possibly grinding or welding defects," he said Friday. "There could be some stress corrosion cracking going on or even some fatigue. There's multiple causal factors that haven't been isolated. They don't know what the true cause is." Framatome ANP, a Lynchburg, Va.-based nuclear plant services company, is developing the repairs, which will involve replacing a portion of the instrumentation tube, Halpin said. "We're in the process of conducting the mockups," he said. "We'll work through our repair over the next month. The bottom line is to do it right. So we're doing some extensive practicing and then we'll get out into the field shortly. "It is a procedure that is fairly extensive. It's one that our team will be ready for, though." Gramm described the repair as a "half-nozzle technique." "They basically go in and do some machining and remove the bottom half of a nozzle and replace it with upgraded material and re-weld that," he said. While similar repairs have been performed at other nuclear plants, the difference here is that it's being done at the bottom of a reactor vessel, Gramm said. Halpin said completion of the repairs should allow the plant to get back into operation late in the summer. Gramm said the goal was realistic "based on what we know today." "But more information will be coming to light between now and late summer and it's hard to predict what we might find out," he added. The two reactors produce 2,500 megawatts of electricity and serve more than 1 million homes in south central Texas. Unit 1 went into service in August 1988. Unit 2, which remains running, went into operation 10 months later.