On Mon, 11 Mar 2019 at 16:10, Peter Blodow <[email protected]> wrote:
Suddenly, a wave occurred, higher than the usual ones, so that they had > to run back to dry grounds, but all of them got we pants. He wondered > why that nuclear plant was built so close to the sea, considering the > fact that even without any catastrophic event the water raised up to the > very walls of the facility. We discussed what had happened later and > Dieter's comment was: no wonder at all to me. And that seemed to be the > opinion of many others of the expert team, too. > The plant had been placed where it is now only under the aspect of > economy (safety being put aside) since the pumps für cooling water would > need much more power if the reactors would have been placed higher up or > farther away from the coast. I am sure that everybody dealing with the > question of locating these reactors has the same opinion. I really don't see why... Lets say the current pipes are 2m in diameter. So you move the plant 1km inland, maybe 20m higher. Then you lay 4m diameter pipes, horizontally, inland to the station. Inlet and outlet. The pumps now draw from a small well at the inlet side. So the only additional cost would be to lift the water 20m Am 10.03.2019 um 17:51 schrieb Jon Elson: > >> On Saturday 09 March 2019 23:43:26 Gregg Eshelman via Emc-users wrote: >> >>> >>> The one problem I see as being really troublesome with the design of >>> Fukushima is that it apparently was incapable of being fully self >>> powering of all its systems at any time. > No, not true. They had at least SEVEN Diesel generators. Crazily, > many of them were in the basement of the buildings, where they could > get flooded. Also, a number of them were sea-water cooled, and when > the tsunami hit, the first thing it did was submerge the giant sea > water pump motor and short it out. So, they lost all their sea water > cooling. >>> Who designs a power plant >>> able to run for 25 years or so, producing electricity, without needing >>> to be refueled, that does not tap its own power generation to run all >>> of its electronics, pumps etc? > The problem is the turbines, alternators and their exciters are not > designed to run over a 1000:1 power range. This was what caused the > big mess at Chernobyl. In the US, we require a UPS on the most > critical items such as primary coolant circulating pumps. Then, we > back that up with fast-start Diesel generators that can be on line at > full power in under six seconds. This stuff is REALLY expensive, > especially a UPS that will run FOUR 1000 Hp pumps. The Russians > didn;t want to pay for that, so they came up with the idea they could > run the critical loads off the inertia of the turbine-alternator set > for a minute while the Diesels came on line. This did require the > alternator exciter to be able to regulate the alternator's output > voltage basically down to zero current. Well, after making the mods > to the exciter, they had to test it. Doing a test like this on an > actual, operating reactor requires extremely careful planning, and > training of all personnel in exactly what to do, when, and what to do > if anything diverges from the plan. > > So, they scheduled this test to be done right before a refueling > shutdown. But, somebody didn't get the word, and shut down the > reactor. Uranium reactors build up a huge amount of radioactive > iodine as a fission daughter product, and it is a strong neutron > absorber. So, right after you shut down the reactor, the iodine > builds up, and poisons the reaction, It can take a whole DAY for the > reaction to build back up and "burn off" the iodine. Well, they > needed the reactor to be above some power level to run the test, so > they pulled all the control rods ALL the way out, to try to get some > reaction going again. Now, when ready for refueling, the reactor is > full of Plutonium, which is more reactive than uranium. (Note, the > Chernobyl RBMK-1000 reactor is identical to a graphite pile Plutonium > production reactor they used for their weapons program, so it is > ENGINEERED to make Plutonium, it isn't an unwanted byproduct like > commercial power reactors.) So, when refueling is needed, the reactor > is quite unstable with all that Plutonium, and pulling the control > rods all the way out makes it worse. So, they cut over from grid > power to their own alternator, and as the station ran off the inertia > of the alternator, the alternator SLOWED DOWN! This meant the > frequency decreased, and any pumps running off that power began to > slow down. Now, the next horror of the RBMK-1000 is that it has a > "positive void coefficient". That means that if the cooling water > boils, it INCREASES the nuclear reaction rate! > This is due to the graphite being the neutron moderator, and the water > being a neutron absorber. It isn't clear exactly what the next chain > of events and actions were, but at some point they canceled the test > and scrammed the reactor. Another odd feature of the control rods of > that reactor is the bottom half meter of them has a big graphite > plug. The control rods sit in the middle of the cooling water pipes > of the reactor (the RBMK-1000 is not immersed in water like most other > reactors). So, driving dozens of control rods inward opposed the flow > of the cooling water, the water started to boil, the slugs of graphite > entering the core increased the reactivity, and the reaction ran away > very quickly. > > This insane test, of course, should have NEVER been done on a fueled > reactor. But, that's Russia for you. >>> No nuclear power plant should require >>> an external electricity supply for anything as long as at least one >>> reactor is 'hot' and one turbine is running. > Well, that's why they have BANKS of Diesel generators! >>> IMHO, an ideal >>> multi-reactor power plant should have one small >>> reactor/turbine/generator set for powering everything in the facility. > No, you have to have massive amounts of electrical power to even begin > to start a small reactor. > The Callaway County plant is a pressurized water reactor, and has FOUR > 1000 Hp circulating pumps. In fact, the bring-up procedure after a > shutdown is to use the pumps to warm the reactor to near operating > temperature, as the reactor itself would raise the temperature too > quickly. >>> One the size of what's used in a nuclear submarine. Under normal >>> conditions its output would be added to what the big reactors and >>> generators produce, but in an emergency where the big reactors are >>> shut down, the little one would stay up and running, in its well >>> armored and isolated, flood proof, building, supported on isolating >>> springs. > Diesel generators can be started in seconds when needed, a reactor > takes hours or DAYS to be started safely. >>> When the earthquake hit, Fukushima went to automatic shutdown. >>> Apparently the external power supply also went down so the diesel >>> generators kicked in. That's where the trouble began. The tsunami took >>> out the generators, which shut down the cooling pumps. Since there >>> wasn't any other way to get power to the pumps to cool down the >>> reactor cores, they heated up to the point where the water in the >>> vessels split into hydrogen and oxygen, which then caused explosions. > Well, not exactly right. The various items in the reactor core must > not absorb neutrons or the reactor won't work. With a limited choice > of material, it is practice to make the fuel rod cladding from > Zirconium. Hot Zirconium in water is kind of like pouring water on > burning Magnesium, it splits the water to get the Oxygen. This can > start as soon as the reactor core is uncovered, and the Zirconium > burns fine in pressurized steam. From a neutron perspective, > Zirconium is ideal, from all other perspectives, it is one of the > worst things to use. >>> Better protected generators, and more of them, plus modern control >>> systems with the ability to quickly self test for damage and get back >>> online after a SCRAM initiated by the earthquake sensors - might have >>> gotten one core back online and the facility back under self power in >>> the time between the quake and the tsunami hitting. But that couldn't >>> happen because Fukushima was forced to be frozen in the technological >>> past. >>> >>> Is Japan still keeping all their nuclear plants idle? > No, they have restarted a few of their better-engineered plants. > > Of course, the concept of placing the oldest plants RIGHT on the ocean > in the country that has known about the tsunami phenomenon for > thousands of years was just insane. They DO have a problem that the > government is under the thumb of industry there. > > (My apologies for a very long answer to an off-topic thread.) > > Jon > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
