That's the rational human response to what appears at the time to be a life-threatening event.It was pretty much get out any way you could, and run away.
NUCENG said:US BWRs I am familiar with have pump houses to protect the cooling water pumps for General Service Water, Emergency Service Water and Circulating Water systems. These buildings are safety-related, sesmically qualified and water tight where to protect the pump motors. Impeller shafts drive the impellers through a water sealed fitting on the motor floor. Power cables can be elevatedor routed in water tight conduits. So it is possible to protect pumps from flooding damage even if they are located near the water edge.
Most Curious said:Do the seawater pumps have a safety for loss of NPSH?
Surely they sucked air when the sea retreated in the moments before the tusnami!
biffvernon said:That's the rational human response to what appears at the time to be a life-threatening event.
Nuclear power stations ought to be designed to be safe whenever all the staff unexpectedly rush for the exit and the electricity supply fails. How many of the world's power plants fit that?
NUCENG said:This report is a verbatim quote from other news reports. My first criticism is the description of a 3 cm or 7 cm fault. A linear crack is not a significant leak. Leakage requires a differential pressure AND a break AREA. If this is a newsperson misquote and the answer is 3 cm2 or 7 cm2 that is way less than the area that would be classified as containment failure.
http://search.japantimes.co.jp/cgi-bin/nn20110526a1.htmlTepco said if it hypothesizes that a breach of about 3 cm wide occurred at the reactor 1 containment vessel 18 hours after the quake and widened to about 7 cm 50 hours later
"If we do our analysis on the premise that there was a leak in the piping, it matches (data) in reality," a Tepco official said at a news conference.
biffvernon said:That's the rational human response to what appears at the time to be a life-threatening event.
Nuclear power stations ought to be designed to be safe whenever all the staff unexpectedly rush for the exit and the electricity supply fails. How many of the world's power plants fit that?
All this is about the design basis. Of course it's possible to design more systems, pools, heat exchangers, cooling towers but first you have to set up your design basis. Then if something bad happens you can check if it was an error in build, in design or in design basis.WhoWee said:About 7,000(?) posts ago I also pondered the possibility of a mechanical backup. It seems reasonable something could operate off the excess heat - like a giant thermostat - to open and let sea/fresh water in - then close when the temperature drops?
NUCENG said:Each of the plants has three circulating water pumps (Unit 1 may only have 2). Those are the largest pumps in your pictures. Each plant probably also has two general service water pumps and two emergency service water pumps. If you look at Unit 4 you see the four small pumps and three circular areas at the inlet that are where the motors for the circulating water pumps should be. Since the plant was in an outage the motors may have been removed for maintenance. Or they may have been destroyed in the tsunami.
jlduh said:I add a picture showing how they look like -these are from N°5 reactor and got hit by this big blue structure, but they look similar to the others:
http://www.netimago.com/image_202944.html
tsutsuji said:Yesterday I found a Tepco report confirming that unit 4's 3 main seawater pumps were removed for maintenance : https://www.physicsforums.com/showthread.php?p=3321704#post3321704
What is the purpose of "service water pumps" ?
The trajectory of the big blue structure, a gantry crane, is shown on page 40 of http://www.tepco.co.jp/nu/fukushima-np/images/handouts_110525_01-j.pdf. I guess this is the crane that is used, among other purposes, when the pumps are removed for maintenance.
NUCENG said:General service water pumps feed non-safety coolers/ Emergency service water feeds the safety related coolers such as the diesels.
seeyouaunty said:http://search.japantimes.co.jp/cgi-bin/nn20110526a1.html
Seems to me that if there is a crack that is 7cm wide (not long, but wide) that would make the opening at least ~40cm2. Its worth noting that this is a hypothesis by Tepco to explain the various instrument readings from the reactor, so they probably have a particular flow-rate in mind for the theoretical leak.
[PLAIN]http://www2.jnes.go.jp/atom-db/en/trouble/individ/power/g/g20051102/051102.gifjlduh said:Do we know more on this for the various reactors/plants? Which pumps did fail?
These pumps should at least be put in a bunker if they have to stay close to the sea...
At Daini, from the picture i posted, i don't see the main pumps being inside a building. This picture is from the 12th of March, one day after the tsunami.
Astronuc said:It's been years since I've done a calculation on the turbine side, but I remember a vacuum drawn on the condenser since the water temperature is cold (relative to the turbine) and the vapor pressure is very low - less the 1 atm. That water would be passed to the reheaters coming off the LP stages.
tsutsuji said:Thanks. The two safety-related ones are probably those belonging to the 12 (=6 units x 2) failed "RHR sea water systems" mentioned on page 50 of http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_110525_01-e.pdf
zapperzero said:http://www.japantoday.com/category/national/view/japan-ends-projections-of-radioactive-substance-spread-from-nuclear-plant
NUCENG said:1 Bq per 72 hours of I131? We wish! Obviously the reporter dropped a few orders of magnitude.
clancy688 said:Isn't that probably well below the radioactivity release of an normally operating NPP? Just wondering...
NUCENG said:That would be considered leakage, not containment failure.
NUCENG said:TThat is about 2% of the decay rate of potassium in a banana. ;-}
Today, TEPCO admits the Reactor 1's Reactor Pressure Vessel (RPV) may have broken right after the earthquake and the pipe connected to the High Pressure Coolant Injection system (HPCI) for the Reactor 3 probably also broke during the earthquake. (The article linked below doesn't say the piping is for the HPCI, but the earlier Mainichi Japanese article on May 25 says so.)
A diagram showing temperature changes at the reactor's containment vessel indicates that temperatures and pressure momentarily shot up immediately after the quake.
Mitsuhiko Tanaka, a former nuclear reactor design engineer, says high-temperature steam apparently leaked out to the containment vessel after either the reactor's pressure vessel or its accessory piping was partially damaged.
The operator, Tokyo Electric Power Co., admitted Wednesday that critical cooling piping at the same plant's No. 3 reactor may also have been damaged in the quake.
NUCENG said:US BWRs I am familiar with have pump houses to protect the cooling water pumps for General Service Water, Emergency Service Water and Circulating Water systems. These buildings are safety-related, sesmically qualified and water tight where to protect the pump motors. Impeller shafts drive the impellers through a water sealed fitting on the motor floor. Power cables can be elevatedor routed in water tight conduits. So it is possible to protect pumps from flooding damage even if they are located near the water edge.
elektrownik said:What is with unit 2 sfp ? They can't fill it with water, size is the same like in unit 4, but in unit 4 after injection water level is ~6400mm, in unit 2 (after injestion) only ~3500mm, also the temperature jumps are strange, maybe sensor damage ? Temperature is bigger after water injection...
for example
5/22 11:00 2000mm 46C
5/23 05:00 4000mm 70C
5/26 05:00 3000mm 45C
NUCENG said:During BWR plant operation there are areas that get to 1 Sv per hour primarily near steam piping due to N-16 gamma radiation. These areas are locked high radiation errors where personnel access is not allowed during operation. Examples include the steam jet air ejector area, the reactor water cleanup area, and the steam tunnel between the reactor building and turbine building.
NUCENG said:US BWRs I am familiar with have pump houses to protect the cooling water pumps for General Service Water, Emergency Service Water and Circulating Water systems. These buildings are safety-related, sesmically qualified and water tight where to protect the pump motors. Impeller shafts drive the impellers through a water sealed fitting on the motor floor. Power cables can be elevatedor routed in water tight conduits. So it is possible to protect pumps from flooding damage even if they are located near the water edge.
Rive said:This also imply the possibility of direct release from an RPV (or less likely from an SFP): otherwise it would be trapped in the torus.
NUCENG said:Again, I am not saying there wasn't seismic damage. there were reports of water leakage inside reactor buildings, but apparently it was not radioactive as some workers feared. Unit 3 had a fairly significant delay before starting RCIC or HPCI and there is no clear explanation why. But both systems were used later. There was speculation that the Unit 1 Isolation Condenser failed due to sesmic damage, but now it appears that was operator action that secured the system after only a few minutes. I just haven't seen any conclusive evidence of safety system failures prior to the tsunami.