If you’ve got a standby generator bolted to the side of your house, you’ve probably heard it wake itself up on a quiet morning. Most of them run a short exercise cycle every week or two, just to prove the engine still starts before the day you actually need it. Annoying? A little. But it beats finding out during an ice storm that the thing’s dead.<\/p>\n
Nuclear plants do the same thing, just with much bigger diesels and a lot more paperwork. And at one plant in southwest France, getting one of those generators ready for its routine test has now lined up with a reactor shutting itself down. Again.<\/p>\n
EDF, the French utility that runs the country’s reactors, says unit 2 at its Blayais plant shut down automatically at 8:40 a.m. local time on Saturday, October 24<\/a> (2:40 a.m. Eastern), while its teams were preparing a periodic test on one of the unit’s backup diesel generators. The 900-megawatt reactor didn’t get back on the grid until 4 a.m. on Wednesday, October 28.<\/p>\n That works out to a little over 92 hours offline. And yes, I counted the time change, because France set its clocks back an hour in the early hours of that Sunday. So technically the reactor got an extra hour off. Lucky reactor.<\/p>\n Blayais sits on the Gironde estuary in the town of Braud-et-Saint-Louis, about 30 miles north-northwest of Bordeaux. It has four reactors. Unit 1 has been shut down for scheduled maintenance since late August, so units 3 and 4 kept the place producing on their own. EDF says the event had no consequences for the safety of the plant, its staff or the environment.<\/p>\n It’s a fair question. A reactor makes electricity, so why would it ever need a generator?<\/p>\n Basically, a reactor doesn’t stop making heat the moment it shuts down. The fuel keeps putting out what engineers call decay heat long afterward, and pumps have to keep moving water through the core to carry it away. Those pumps need power. Normally it comes from the grid, but if the plant loses its connection to the outside world, the backup diesels are what keep the cooling going.<\/p>\n All of France’s operating reactors have two emergency diesel generator sets, according to the country’s nuclear safety experts. At Blayais, EDF says reactors 2, 3 and 4 also each got a third one, an “ultimate backup diesel,” as part of a package of extra safety gear for extreme events. That’s the kind of upgrade France ordered after the Fukushima accident. And since nobody wants to learn a generator is broken on the day it matters, the plant starts them up on a schedule to make sure they work.<\/p>\n The shutdown itself is the reactor’s protection system doing what it was built to do. When sensors pick up something outside normal operating conditions, control rods drop into the core and stop the chain reaction within seconds. EDF describes the automatic trip as a protection designed into the reactor from the start.<\/p>\n Here’s where it gets a bit more interesting.<\/p>\n On September 1, at 10:05 a.m., the same reactor shut itself down while a functional test was running on one of its backup diesel engines. That time, EDF did give a cause<\/a>: an electrical panel malfunctioned during the test. Unit 2 stayed offline until 10:50 a.m. on September 12, a little over 11 days.<\/p>\n Then on September 23, at 11:45 p.m., the plant’s operators took unit 2 offline on purpose to work on a piece of equipment in the non-nuclear part of the facility. It came back at 11:45 p.m. on October 4, exactly 11 days later. Twenty days after that, it tripped again during the diesel test prep.<\/p>\n And that’s a reactor that had only just finished a long refueling and maintenance stop. France’s nuclear regulator, ASNR, says unit 2 was shut down on April 11 and got back to full power on July 7. Put it all together and unit 2 spent nearly 26 of the 57 days between September 1 and October 28 off the grid. That’s a pretty rough fall for one reactor.<\/p>\n So what tripped it on October 24? I don’t know, and EDF hasn’t said. Its first notice said teams were running checks to pin down the exact origin, and the update announcing the restart didn’t name one. I’m also not going to tell you the September and October trips are connected, because EDF hasn’t said that either. They could be two completely different problems that happened to show up around the same kind of job.<\/p>\n Still, two automatic shutdowns during diesel generator work on the same reactor in 53 days is arguably what I’d most like EDF to explain. The Blayais site posts a regular roundup of the events it declares to the regulator, so that’s probably where any rating of these two will show up, if one comes.<\/p>\n So why should you care about one French reactor? Mostly scale.<\/p>\n Blayais runs four 900-megawatt pressurized water reactors, the same type that makes up most of the US fleet, and they’ve been running for more than 40 years. EDF says the plant produced 23 terawatt-hours last year and covers about half the electricity needs of Nouvelle-Aquitaine, the region around Bordeaux. It also says 2,196 people work there between EDF and its contractors.<\/p>\n It’s an open-loop plant, too, which is why you won’t see any cooling towers there. In plain terms, Blayais pulls water straight out of the estuary, runs it through its condensers to turn steam back into water, and sends it back a few degrees warmer. That water never touches the reactor core, since it runs in a separate circuit. EDF’s own figures put the intake at about 1.24 trillion gallons a year. If you read our story about jellyfish clogging the seawater filters at Gravelines<\/a>, you’ve already seen what can go wrong at that end of a plant. Nothing EDF has published points to the water side in this case, though.<\/p>\n Probably not on its own. An automatic shutdown is a safety system doing exactly what it’s designed to do, and in its latest annual report, ASNR put Blayais’s safety record on par with the rest of EDF’s fleet.<\/p>\n It hasn’t been the quietest October for EDF’s reactors in the southwest, though. Upstream at the Golfech plant, on the Garonne River that feeds the same estuary, the 1,300-megawatt unit 2 shut itself down automatically at about 1:05 a.m. on October 14. EDF traced that one to a malfunction in a piece of control equipment, and the reactor was back on the grid at 11:05 a.m. on October 22. Golfech 2 had already spent chunks of the summer offline when the Garonne ran too warm, part of the same heat squeeze behind the river-temperature shutdowns we covered this summer<\/a>.<\/p>\n If anything, EDF’s paperwork is reassuring. The utility posted both Blayais notices the same day, with times down to the minute, which is frankly more detail than I usually get from my own power company when the lights go out.<\/p>\n The timing’s a little awkward for EDF, too. Units 2, 3 and 4 at Blayais are going through their fourth periodic safety review, the once-a-decade check French law requires of every reactor, and this round feeds into the regulator’s conditions for running them past 40 years. A public inquiry on that review<\/a> opened on October 26, two days after the trip, with in-person sessions at five local town halls and comments accepted online.<\/p>\n That inquiry runs until November 25, and anyone can file comments on the online register before then.<\/p>\n","protected":false},"excerpt":{"rendered":" If you’ve got a standby generator bolted to the side of your house, you’ve probably heard it wake itself up … <\/p>\nSo why does a nuclear plant need a diesel engine?<\/h2>\n
Unit 2 has tripped during diesel work twice since September<\/h2>\n
Blayais covers about half its region’s electricity needs<\/h2>\n
So is this a big deal?<\/h2>\n