Japan Earthquake: nuclear plants


by gmax137
Tags: earthquake, japan, nuclear
SteveElbows
SteveElbows is offline
#7291
May15-11, 11:06 AM
P: 630
Quote Quote by SteveElbows View Post
Thanks for finding the official document about this stuff, its very interesting, and we should just forget all about the '16 hours' that Kyodo story mentions.
Oops, I worded that badly. What I meant is that 16 hours is not when fuel began to be uncovered, the document shows that this is when they think the fuel fell to the rpv bottom.
clancy688
clancy688 is offline
#7292
May15-11, 11:08 AM
P: 546
Quote Quote by bytepirate View Post
obviously, they are using a different data set:
http://www.tepco.co.jp/en/press/corp.../110515e10.pdf
water level at bottom of fuel at 19:30 on 3/11
Thank you very much! That data sheet is VERY interesting. I think the data Stolfi and others used came from NISA or TEPCO.

looking at the #3 data, this is a little scary....
For me it's rather scary what happens with a BWR/3 when emergency power supply fails - it's immediately doomed.
Fast decrease in water height started only minutes after power failure. Only two hours later the top of the fuel was uncovered. And three and a half hours later the fuel was completely uncovered. Which means that the passive cooling equipment (Isolation Condenser) was totally useless. There are not many BWR/3 or older in use... I asked wikipedia, one is in spain, the rest in the USA: Dresden NPP (2x), Monticello NPP (1x), Nine Mile Point NPP (1x, BWR/2), Oyster Creek (1x, BWR/2), Pilgrim NPP (1x), Quad Cities NPP (2x) and Santa Maria de Garona NPP in Spain (1x). I think the operators of those plants should make sure now that there's always emergency power available... without relying on passive cooling systems.
Now I'm interested in such a report regarding Unit 2 and 3... showing if the BWR/4 design with RCIC was considerably better in providing emergency cooling.


One question for the physicists: core temperature began rising very fast, but once it reached 2900 degrees it suddenly stopped rising. Why? I'd expect a temperature graph resembling a function of ln(x), not such a sudden stop.

And another question (for everybody): What's the data TEPCO used for that sheet, and where did it come from? It doesn't seem to be an estimate, since there are bumps in those graphs, indicating they are build on accurate data.

Quote Quote by SteveElbows View Post
Thanks for finding the official document about this stuff, its very interesting, and we should just forget all about the '16 hours' that Kyodo story mentions.
But the document states exactly that 16 hours after the earthquake, the core had totally molten down. Look at the four images at page 3.
ernal_student
ernal_student is offline
#7293
May15-11, 11:13 AM
P: 34
Quote Quote by clancy688 View Post
The meltdown occured before venting and before the fuel rods got exposed?
It might help to recall the details with this excerpt from the accumulated information on the related wikipedia page:
On 11 March at 14:46 JST, unit 1 scrammed successfully in response to the earthquake though evacuated workers reported violent shaking and burst pipes within the reactor building. All generated electrical power was lost following the tsunami leaving only emergency batteries, able to run some of the monitoring and control systems. At 15:42, TEPCO declared a "Nuclear Emergency Situation" for units 1 and 2 because "reactor water coolant injection could not be confirmed for the emergency core cooling systems." [...]

After the loss of site power, unit 1 initially continued cooling using the isolation condenser system; by midnight water levels in the reactor were falling and TEPCO gave warnings of the possibility of radioactive releases. In the early hours of 12 March, TEPCO reported that radiation levels were rising in the turbine building for unit 1 and that it was considering venting some of the mounting pressure into the atmosphere, which could result in the release of some radioactivity. Chief Cabinet Secretary Yukio Edano stated later in the morning the amount of potential radiation would be small and that the prevailing winds were blowing out to sea. At 02:00 JST, the pressure inside the reactor containment was reported to be 600 kPa (6 bar or 87 psi), 200 kPa higher than under normal conditions. At 05:30 JST, the pressure inside reactor 1 was reported to be 2.1 times the "design capacity", 820 kPa.Isolation cooling ceased to operate between midnight and 11:00 JST 12 March, at which point TEPCO started relieving pressure and injecting water. One employee working inside unit 1 at this time received a radiation dose of 106 mSv and was later sent to a hospital to have his condition assessed.

Rising heat within the containment area led to increasing pressure. Electricity was needed for both the cooling water pumps and ventilation fans used to drive gases through heat exchangers within the containment. Releasing gases from the reactor is necessary if pressure becomes too high and has the benefit of cooling the reactor as water boils off but this also means cooling water is being lost and must be replaced. If there was no damage to the fuel elements, water inside the reactor should be only slightly radioactive.

In a press release at 07:00 JST 12 March, TEPCO stated, "Measurement of radioactive material (iodine, etc.) by monitoring car indicates increasing value compared to normal level. One of the monitoring posts is also indicating higher than normal level." Dose rates recorded on the main gate rose from 69 nGy/h (for gamma radiation, equivalent to 69 nSv/h) at 04:00 JST, 12 March, to 866 nGy/h 40 minutes later, before hitting a peak of 0.3855 mSv/h at 10:30 JST.

At 13:30 JST, workers detected radioactive caesium-137 and iodine-131 near reactor 1, which indicated some of the core's fuel had been damaged. Cooling water levels had fallen so much that parts of the nuclear fuel rods were exposed and partial melting might have occurred. Radiation levels at the site boundary exceeded the regulatory limits. [...]

At 15:36 JST on 12 March, there was an explosion in the reactor building at unit 1.
The press release came out at what is now considered the approximate time of the meltdown - during the period of increased gamma radiation.
intric8
intric8 is offline
#7294
May15-11, 11:24 AM
P: 24
"Does anyone have any reliable info on the nuclear plants - the reports on the news seem garbled to me."
Weeks ago, someone mentioned the very first message in this thread (above), and how things have changed so little with Tepco that this comment is still very appropriate today.

Ringing truer than ever.
triumph61
triumph61 is offline
#7295
May15-11, 11:36 AM
P: 68
According to Tepco, hyrogen produced in the overheating of the reactor core at Unit 3 flowed through a gas treatment line and entered Unit No. 4 due to a breakdown of valves. Hydrogen leaked from ducts in the second, third and fourth floors of the reactor building at Unit 4 and ignited a massive explosion.

http://online.wsj.com/article/SB1000...776621604.html
clancy688
clancy688 is offline
#7296
May15-11, 11:57 AM
P: 546
Quote Quote by triumph61 View Post
According to Tepco, hyrogen produced in the overheating of the reactor core at Unit 3 flowed through a gas treatment line and entered Unit No. 4 due to a breakdown of valves. Hydrogen leaked from ducts in the second, third and fourth floors of the reactor building at Unit 4 and ignited a massive explosion.

http://online.wsj.com/article/SB1000...776621604.html
Did they actually solve the Unit 4 explosion mystery? Sounds to good to be true... hence it can't be true! (just kidding... but what's up with them... suddenly releasing informations)
AntonL
AntonL is offline
#7297
May15-11, 12:04 PM
P: 521
Quote Quote by triumph61 View Post
According to Tepco, hyrogen produced in the overheating of the reactor core at Unit 3 flowed through a gas treatment line and entered Unit No. 4 due to a breakdown of valves. Hydrogen leaked from ducts in the second, third and fourth floors of the reactor building at Unit 4 and ignited a massive explosion.

http://online.wsj.com/article/SB1000...776621604.html
Quote Quote by clancy688 View Post
Did they actually solve the Unit 4 explosion mystery? Sounds to good to be true... hence it can't be true! (just kidding... but what's up with them... suddenly releasing informations)
Tepco have been reading this forum for ideas, I postulated this a month ago
Quote Quote by AntonL View Post
But where does the Hydrogen come from for the explosion, forum members here agree that the explosion centre was lower down in the building on the north side, which does make sense because of the observed damage.

For that scenario I can also give a very imaginative explanation. When unit 3 was vented, could unit 4 have pumped hydrogen steam into unit 3. Unit 3 and 4 share a common exhaust stack and there was no power for fans to work to aid the exhaust procedure, Furthemore, we do not know if there are any dampers in the system and if installed I would imagine they fail open when power is lost.

Lets assume unit 3 pumped unit 4 full of steam and hydrogen, this would then be into the suppression chamber, then H2 will leak into the primary containment chamber, it would not immediately escape to the roof, as there is a seal between the reactor vessel and PCV so that PCV is not flooded during fuel transfer. The Hydrogen could have leaked out through the access hatch which would not have been sealed due to the maintenance taking place, This access hatch is on the ground floor, which is the right level for a lower explosion centre. The only question why the long delay between units 3 and 4 exploding.
and again later
Quote Quote by AntonL View Post
this new underwater video of SFP4 certainly seems to rule out that SFP4 boiled dry and Hydrogen produced by overheating fuel rods and, so how did the Hydrogen get into reactor 4 building? In my opinion, only two possibilities remain:
1. Hydrogen being pumped into the building during venting of unit 3. Unit 3 and 4 share a common exhaust stack and there was no power for fans to work to aid the exhaust procedure.
2. Radiolysis of water as per post #6068

Do you have any other ideas?
PietKuip
PietKuip is offline
#7298
May15-11, 12:12 PM
P: 184
Quote Quote by clancy688 View Post
One question for the physicists: core temperature began rising very fast, but once it reached 2900 degrees it suddenly stopped rising. Why? I'd expect a temperature graph resembling a function of ln(x), not such a sudden stop.
It stops at the boiling point of corium. The boiling point of iron is 2750 C.
StrangeBeauty
StrangeBeauty is offline
#7299
May15-11, 12:16 PM
P: 61
Quote Quote by clancy688 View Post
(just kidding... but what's up with them... suddenly releasing informations)
The cynic in me says the answer is "Please don't look at #3 too closely right now! Oh look! #1 melted down 16 in hrs two months ago! #4 was blown up by #3!" The "shiny object distraction technique" in action. I hope I'm very wrong. :)
clancy688
clancy688 is offline
#7300
May15-11, 12:23 PM
P: 546
Quote Quote by PietKuip View Post
It stops at the boiling point of corium. The boiling point of iron is 2750 C.
Thanks. And how could they measure those numbers?


And another question: Where do I get up to date sensor data of Unit 3?
PietKuip
PietKuip is offline
#7301
May15-11, 12:26 PM
P: 184
Quote Quote by clancy688 View Post
Thanks. And how could they measure those numbers?
These are calculations. The timing is made to fit the measured temperatures at different places.
clancy688
clancy688 is offline
#7302
May15-11, 12:29 PM
P: 546
Quote Quote by PietKuip View Post
These are calculations. The timing is made to fit the measured temperatures at different places.
I meant, where did they get the numbers to build their graphs in the TEPCO press release regarding the melt down. The graphs shown there don't look as if they were done with calculation data.
|Fred
|Fred is offline
#7303
May15-11, 12:38 PM
P: 312
Quote Quote by clancy688 View Post
Then you should've watched german tv... quite the opposite.
As far as the opinion given in this board was concerned, the exact expertise was (if I recall corectly) " if there is water in the RCV then meltdown is unlikely ". The available data indicated there was some watter.

I do believe that the given statement still stand
GJBRKS
GJBRKS is offline
#7304
May15-11, 12:48 PM
P: 82
Quote Quote by bytepirate View Post
obviously, they are using a different data set:
http://www.tepco.co.jp/en/press/corp.../110515e10.pdf
water level at bottom of fuel at 19:30 on 3/11

i am not sure, where the other data set, that stolfi et al are using originates from.

'On the other hand, as the temperature of the RPV of Unit 1 is in the range of 100C - 120C, stable cooling is being achieved'

looking at the #3 data, this is a little scary....
Wow , that link finally makes it clear where to find the D/W HVH temperature sensor :



And if its BELOW the RPV , then the increasing temperature reading for Unit 3 ( up to 197 Celsius from 125 Celsius within 24 hours) could mean that corium has breached into the containment just now ...
Astronuc
Astronuc is online now
#7305
May15-11, 12:53 PM
Admin
Astronuc's Avatar
P: 21,628
Quote Quote by bytepirate View Post
obviously, they are using a different data set:
http://www.tepco.co.jp/en/press/corp.../110515e10.pdf
water level at bottom of fuel at 19:30 on 3/11

i am not sure, where the other data set, that stolfi et al are using originates from.

'On the other hand, as the temperature of the RPV of Unit 1 is in the range of 100C - 120C, stable cooling is being achieved'

looking at the #3 data, this is a little scary....
I should point out that the 110515e10.pdf is an analysis - a model - and may not reflect physical reality, which is often the case in licensing/safety analysis. Effectively, to get to fuel pellet melting, they would have to assume near adiabatic conditions.

They also claim to have water in the bottom of the RPV, but not the core. The progression seems somewhat unreal.
Godzilla1985
Godzilla1985 is offline
#7306
May15-11, 12:57 PM
P: 9
Eh, come on. Given TEPCO's own statements concerning #1 in that WSJ article, do you really think any of those gauges can be trusted? #3 probably had a full meltdown after 16 hours as well, and the corium dropped through some time around the 21st of March when that thick black smoke appeared...
~kujala~
~kujala~ is offline
#7307
May15-11, 12:59 PM
P: 110
Nice work, Anton!
(BTW: I remember there were some counterarguments against your theory. Now that TEPCO has adopted your theory is there any more validity in these counterarguments? TEPCO engineers must know their plants so their evaluations about possible theories have a certain level of assertiveness, which the outsiders lack.)
triumph61
triumph61 is offline
#7308
May15-11, 01:00 PM
P: 68
The work to install a supporting structure for the floor of the
Spent Fuel Pool of Unit 4 was started. (From May 9.)


http://www.nisa.meti.go.jp/english/f...110510-1-1.pdf

Has someone checked the Situation IN Unit 4??


Register to reply

Related Discussions
8.9 earthquake in Japan: tsunami warnings Current Events 671
New Nuclear Plants Nuclear Engineering 9
Gen IV Nuclear Plants Nuclear Engineering 10
New Nuclear Plants Nuclear Engineering 14
Astronomer Predicts Major Earthquake for Japan General Discussion 65