Infantile Disorder San Onofre
Replacement of steam generators in nuclear power plants, "San Onofre" — the story lasting for years and cost billions of dollars. She opened the fundamental problems that have accumulated in the nuclear industry in the U.S..
The structure of the NPP "San Onofre" includes two operating unit — the second and third. They work under the pressure of light water reactors PWR capacity of up to 1100 MW (e). The first unit of the plant with a PWR reactor at 456 MW (e) was finally stopped in 1992, and today serves as a repository for spent nuclear fuel.
The second unit was commissioned in September 1982. Third went into operation exactly one year later — in September 1983.
The station on the Pacific coast of California, one of the first faced with the problem of alloy 600. The report NUREG-1823 authorship U.S. regulators said that the third block of the NPP "San Onofre" was first identified case of severe corrosion damage element of the alloy 600 — namely, fitting for instrumentation equipment on the volume compensator.
Like many other U.S. plants, nuclear power plants, "San Onofre" was forced to go to an early replacement of steam generators — also due to corrosion. The design lifetime of 40 years, PG could not withstand.
On the problem of alloy 600 electronic edition AtomInfo.Ru has written repeatedly. Alloy 600 — an alloy with a high content of nickel (76%), and he willingly used by Western designers in the projects 60-80's.
In 1959, a report on a scientific seminar on corrosion sounded warnings about increased susceptibility to corrosion of high-nickel alloys. They were ignored. As a result, in the 90th year on the western plants began a long and costly equipment replacement company affected by stress corrosion cracking of the primary circuit (PWSCC).
In the steam generators blocks № № 2-3 NPP "San Onofre" Alloy 600 were produced heat exchange tubes. The author of article no exact data about the speed with which the degradation of TOT on these blocks. But we know (from the reports EPRI), that the pace of killing ONE of Alloy 600 steam generator western projects an average of 0.3% per year.
In the XXI century, the United States lost their own ability to manufacture steam generators for nuclear power plants. It is not that Americans ignore it. But for the general public this fact is served in a nice wrapper «World Wide Components Fabrication». So, for the first blocks in the country with AP-1000 nuclear power plants, "Vogl" steam generators will be manufactured in South Korea, and blanks for them — in Japan.
American labor unions have been trying to reverse a nasty trend and return to the country of nuclear engineering. In 2010, the steel industry workers' union (USW) addressed an open letter to regulators, urging them to ban the use of imported equipment for the new U.S. units.
"I am concerned about the potential use of imported equipment for the reactors, as it not only limit the ability of our nation to combat the unacceptably high unemployment rate, but potentially jeopardize the health and safety of the people …… We are repeatedly confronted with examples of unsafe and does not meet standards of products supplied to consumers from China — dog food, heparin, tires and other products … These risks are real, "- said USW President Leo Gerard.
But the struggle of trade unions or to nothing, and the revival of the American Atommash has not moved one iota. Not surprisingly, the owners of nuclear power plants, "San Onofre" for the new steam generators had to apply abroad, namely in the Japanese corporation «Mitshubishi Heavy Industries» (MHI).
From the Japanese plant workers needed to produce and deliver the new steam generators are capable of reliably work out at least 20 or more years. Terms of the license blocks № № 2-3 NPP "San Onofre" completed in 2012-2013 (to achieve 40 years of service). But the owners of the station planned to extend for 20 years, and then, maybe, and a further 20.
Steam generator for San Onofre plant at MHI
MHI actively took up the execution of the order. But at first there were warning signs. During the inspection of the two PG for the third unit in the spring of 2010 revealed cracks in the welds. In operating conditions, cracks inevitably become a hotbed of corrosion damage. The results of the inspection were the subject of heated discussions with customers and regulators.
The Americans blamed the incident on Japanese artists. But the causes of microcracks NRC and the operating organization for a long time could not come together.
Regulators saw the root of all evil in the method of preparation of materials for welding, adopted by the Japanese factories.
In turn, the EO believed responsible changes in the technological process made factory workers in the manufacture of GHG for the third block. The plant was overloaded with orders and refused to hand-sanding the field of welding, explaining it by the fact that the physically unable to allocate for this operation tools.
In the end, the marriage was eliminated. But the bad taste left by the incident. The expert who is familiar with Western technology, said AtomInfo.Ru: «The place where a defect, always made GHG PWR problem. We are talking about seams welded plate (English-language terminology — divider plate or partition plate), separating the input and output steam chamber. "
A schematic view of the lower portion of the vertical GHG PWR.
The plate is marked as partition plate.
Problems with the quality of welding partition plate repeatedly observed in steam generators western projects — but mainly in the past. It was believed that in our time with this disaster could handle.
Recurrence of child illness nuclear engineering that occurred in the manufacture of steam generators for nuclear power plants, "San Onofre," was obliged to alert all parties involved. But apparently this does not happen.
Replacement of GHG
In 2009, nuclear power plants, "San Onofre" began work to replace the steam generators. This was preceded by an easy operation to deliver them from Japan.
From the Japanese factory in Kobe on board «Happy Ranger» steam generators arrived at the port of Long Beach, where barges were transported to the base of the U.S. Marine Corps 'Camp Pendleton' spaced from the station at 15 miles.
The last part of the way from the camp to the NPP Marines overcame heavy load with transfers and walking pace. Indeed, it can carry weights 640 tons of steam and a height of about 20 m? The correct answer is — very slowly. Transporter crawled on roads with a speed not more than 5 miles / hour.
Delivery route GHG NPP "San Onofre"
Conveyor with a steam generator in the way
Steam generator for the third unit delivered to the plant, "San Onofre"
The difficulties of transportation do not go to any comparison with the difficulties faced by staff in the proper time to replace equipment. It's hard work and additional radiation exposure on humans.
Mandatory element of each operation to replace a containment autopsy. Whenever new approach is needed — in the U.S. there is no case where containment would be able to open the template in the same way as the other block.
Specifically at nuclear power plants, "San Onofre" concrete containment dissected jets of pressurized water 25,000 feet per square inch. The steel containment dissected gas torches.
Autopsy containment — no similar case
The whole operation to replace the steam generators in nuclear power plants, "San Onofre" was finished in autumn 2010 PPR on the third block. EA spent to replace a total of more than 670 million dollars. It still seemed more profitable to close the station, as the transition to a non-nuclear power generation would require $ 1 billion for just the next 12 years.
But the benefits of EE and consumers would be able to get in one case — if the new steam generators would work fine.
In January 2012, for new nuclear power plant GHG "San Onofre" revealed damage to the TOT. Regulators require killing all tubes with defects and suspected defects. In addition, some of the tubes has been involved in the test program and U.S. regulations also subject to jamming.
As a result, the second unit was drowned 510 TOT, the third unit — 807 TOT. Total in each of the steam generators is contained by 9727 TOT.
The reasons for the accelerated release of tubes of different system called. One suggestion was outrageous — fretting about the type of pipe pipe (Tube to tube).
In other words, a steam heat transfer tube under the effect of the flow passing therethrough bent or shifted from their positions touching the adjacent tubes. The tubes were rubbing against each other and, of course, rubbed at the contact points.
A similar phenomenon should be completely ruled out the construction of steam generators. Fretting about pipe pipe for steam-generating science — something similar reactivity accidents for reactor physics. However, at the plant, "San Onofre" suspect this is exactly the way of formation of defects TOT.
A thorough inspection of all stations in the U.S. found that the California case is not alone. The report EPRI, presented in February 2012, contains a short extract from the database on the degradation of steam generators — fretting about the type of pipe pipe was found on two more units in the United States.
The names of the blocks with such fretting is not given in the report. However, other sources known — it blocks TMI-1 and «Arkansas One-1". It is interesting to note that there was fretting on the tubes of alloy 690TT — that is, in new steam generators manufactured to replace the old RICH.
Both units, "San Onofre" were pulled over for trial. Almost immediately it became clear — the owners of the station when replacing GHG engaged in "optimizing" process and the legal process to save time and money.
The most serious complaint about the look of the selected method of EO justify the replacement of steam generators.
When drafting the new PG has been used so-called optionlike-to-like. In this case, the new equipment is identical to the replaced, and the amount of justification and approval of the regulatory authority is sharply reduced.
In fact, the principle like-to-like at San Onofre was not fulfilled. In 9350 there was the original steam generators ONE and in the steam generators replacement — 9727. Project developers have identified this change as "minor" and did not violate the principle of similarity.
This change was not the only one. The wall thickness of the one in the new PG was chosen 0.043 inches, or 10.4% less than the thickness of the walls TOT source of GHGs. Alloy 600 was replaced by the alloy 690. Construction of tubes replaced with a U-shaped by a combination of U-shaped with two bends 90 °. Also changed the way mounting anti-vibration devices.
By the way, a professional developer of steam generators to the modification of the project did not attract. The operating organization and factory workers have decided that cope with the problem on their own.
Playing with the rules for the design worthy of condemnation, but is unlikely to give an answer to the question — why cases are fretting about the type of pipe pipe were found on two American units?
Lay claim to the manufacturer, at first glance, does not work. Not least because, in all three cases, different manufacturers — the companies of Japan (MHI), France and Canada. Thus, to explain the emergence of tube-to-tube obvious manufacturing defects can not be.
There is an interesting hypothesis that the reason lies in the effect of «hour-glassing», or hourglass effect. With this effect, the Americans and their Western counterparts faced in the romantic period of the development of nuclear energy — in the 60-70th years.
Hourglass effect was typical of the steam generators of western projects and the resultant desire factory technologists facilitate manufacturing methods of heat transfer tubes. He was manifested in the area of responsibility of the factory workers, but it was not considered a marriage — at least as long as the operation is not defined the relationship between the effect and the appearance of the contact tubes with each other.
If the hypothesis about the role of the hourglass effect in the events at nuclear power plants, "San Onofre" and fretting tube-to-tube will be taken as a basis, it threatens to turn into a hardball scandal. Hourglass effect — a typical manifestation of childhood diseases Atomic Energy, considered completely eliminated by today. Its resurgence can talk about the loss of cultural production and accumulated in the last century of experience manufacturing nuclear equipment.
Manifestation of the hourglass
The preliminary results
The history of the replacement of the steam generators in nuclear power plants, "San Onofre" has not yet been completed. The situation now looks like that.
The second and third blocks are idle since January 2012. The operating organization is seeking permission to start up a second unit for six months and then stop for a thorough inspection of the equipment. Regulators consider the documents prepared by the EA, which will take several months.
On start-up the third block it even comes. In September it began unloading fuel. Under the threat of layoffs hit about 700 plant workers. Experts believe that the block can be saved only new replacement SGs.
Investigations into the causes of accelerated failure of TOT continues. Do regulators have a list of almost 100 questions, the answers to that yet. Even the resignation of the chairman of the NRC Gregory Jacko, who held particularly rigid positions in the investigation, has not helped the station — the new head of NRC Alison Makfarlayn confirmed that the blocks do not return to work for "an extended period".
The theme of which revealed in the course of events at nuclear power plants, "San Onofre" children's diseases of the nuclear industry in the United States prefer not affect aloud.
See also: Engineering in the United States, neither build nor ride