Dieseldude4x4

Even though the rods drop and boron gets injected, there is so much decay heat both in the fuel and in all the metal that it keeps going for a while. This is a big unit we are talking about with a lot of metal to cool down.

Dieseldude4x4

They probably could have had the tsunami not taken out the main circ pumps. They could have continued to power them and cool down normally. The diesel fuel oil tanks were protected by a 6 meter wall but unfortunately, the wave was 7 meters and floated the fuel oil tanks away. No fuel, no engine, no power for the pumps. Anything or force that moves a continent eight feet like it did here, I don't believe you can design for that.

Dieseldude4x4

Even after the reactor trips, you still have to carry away the decay heat both from the fuel and cooling down the massive metal reactor and associated piping systems. It is kinda like running your truck under full load on the interstate and all of a sudden you reach up and shut off the key. The engine will still heat up for a little while before it begins to cool (not to over simplify here but this is the best way I can think to tell you). This is kinda like that only on a much much larger scale. The boron is injected to slow down the fission process where the little particles bounce around into one another and split off releasing heat energy. WHEN everything works like it is designed, it is a very safe process. The rods dropping into the core start the cooldown process and the boron helps slow everything down too.

Timberwolf2

Nuclear Physics 101?
Uranium atom gets split, known as "fission". Two new elements (plus free neutrons) are the result. New elements are unstable, go through a decay process until they are stable. Thus "decay heat". Reactor never really shuts down, thus the use of a logarithmic scale on the power. Full power is 1 X 10/2, 10 % is 1 X 10/1, 1 % is 1 X 10-1, 0.1 % is 1 X 10-2, and so on down to 1 X 10-7 or 0.0000001 %.
The main principle to generating power is a sustainable reaction brought about by controlling the number of neutrons avail. to cause more fissions. One further fission from each previous fission. Boron is a neutron absorber, thus it removes neutrons in the core, thus it can reduce the fission process to almost nil. Boron is used to control the reactivity during normal operation and also to shutdown the reaction process long term.
Even when there are lots of neutrons avail., the has to be many other parameters met to sustain the reaction. This would take many pages to explain.

Dieseldude4x4

Latest update from NEI:

March 15, 2011 – NEI UPDATE on Japanese Reactors as of 8:30 a.m.
Included below is the most current update from Tokyo Electric Company:
=====================
(1) Transfer of Fukushima Daiichi Power Station Workers
At approximately 6:00 today, an abnormal noise began emanating from nearby the pressure suppression chamber of Fukushima Daiichi Power Station. Given that the pressure within this chamber had decreased, it was believed that this was an indication that an abnormality had arisen. From this point on, while water injection operations are still underway, the temporary transfer to a safe place of TEPCO employees and workers from other companies not directly involved with this work has begun.
Currently, at Fukushima Dai-ichi Power Station, the remaining workers are doing their best to secure the safety and security of the site.
The parameters for Unit 2’s nuclear containment vessel and the containment vessel show no significant change.
We are aware of and sincerely apologize for the great distress and inconvenience this incident has caused to not just those inhabitants residing in the immediate vicinity but also society at large.
Q and A for this release.
------------------
Q. Is there any change of the value at the monitoring post?
A. At the monitoring post 4,
Before the abnormal sounds : 73.2μSv / h (6AM) After the abnormal sounds : 1,941μSv / h (7:50AM)
Q. Is it hydrogen explosion?
A. At 6:14AM, odd sounds happened near the pressure restraint room and the pressure in the pressure restraint room goes down low. So, we think that it caused some problem in the room.
We are investigating further information.
Q. Are there any injured people?
A. We do not know at this moment.
==================================
(2)Building Damage of Fukushima Daiichi Nuclear Power Station Unit 4
15 Mar, 2011
TEPCO
Fukushima Daiichi Nuclear Power Station
At approximately 6:00AM, a large sound occurred on the site of the power station. After that, damage was confirmed around the roof of the reactor building on the 4th floor.
After usage, fuel is stored in a pool designated for spent fuel.
The status of the plant and the effects of offsite radioactivity are now under investigation.
TEPCO continues to take all measure to restore the safety and security of the site and are monitoring the site’s immediate surroundings.
Q and A
Q What is the pool temperature?
A Normal temperature is around 25 C, but at 4:18 on March 14 it was 84 C.
We have no record after this.
====================================
(3) [Unit 1 Fukushima Daiichi] 1F-4 Fire Reactor building of 1F-4 is on fire. Efforts are being made to extinguish the fire.
The cause of this fire is estimated hydrogen explosion due to increase of spent fuel pool temperature.

====================================
(4) Other information
At 10:22 a.m. on March 15, monitoring result shown 30 mSv/hr between unit 2 and 3,
400 mSv/hr near unit 3, 100 mSv/hr near unit 4.
The reason of this high value is attributed to the fire at unit 4.
(Monitoring results before and after the unit 2 explosion changed little.)
Number of Personnel at the site was 800 at 6:00am, now reduced to 50, necessary for water injection to unit 1,2 and 3. Water injection to units 1,2 and 3 are in progress. Reactor pressure is stable.


Walter Hill
Director, Member Communications
Nuclear Energy Institute
1776 I Street NW, Suite 400
Washington, DC 20006
www.nei.org
P: 202-739-8047
F: 202-533-0148
M: 202-497-8230
E: whh@nei.org

chaikwa

Dieseldude4x4, what is your opinion on this whole situation becoming a large scale radiation problem that will affect a large area?

Dieseldude4x4

I can't see into the future but as long as they can keep the fuel in the reactor, there is and will be some radiation releases but mostly airborne as is happening right now. I would not say this is would never get as bad as the one in Russia but it is most unlikely since these are two entirely different designs. Best case the fuel melts and stays in the vessel similar to TMI. The one unit was due to be shut down permanently this week since they are all 70's vintage plants. These units are pretty much done for ever as far as power generation goes. It will take a long long time to cool down and then years to develop a decomissioning plan after that. From the status of the situation right now, I do not believe it will be a wide scale issue as you put it. It will have far reaching effects on the nuclear industry as did TMI. Hope this answers your question.

chaikwa

It does. Thanks!

I was just wondering if the radiation contamination would render miles and miles of that city uninhabitable because of a major breach, like Russia. Or worse because there are more generating plants.

My interest is from the fact that I used to be the Deputy of Emergency Management in a town that bordered the Seabrook NH Nuke plant and I often wondered about some aspects of our emergency plans that I helped design and implement.

Dieseldude4x4

The Japan Atomic Energy Agency (JAEA) reported an explosion in the suppression pool at Fukushima Daiichi Unit 2, at 7:14 p.m. EDT on March 14. Reactor water level was reported to be at 2.7 meters below the top of the fuel. The pressure in the suppression pool decreased from 3 atmospheres to 1 atmosphere. Radiation readings at the site increased to 96 millirem per hour.

Dose rates at Fukushima Daiichi as reported at 10:22 p.m. EDT on March 14 were:
• Near Unit 3 reactor building 40 rem/hr
• Near Unit 4 reactor building 10 rem/hr
• At site boundary 821 millirem/hr.
• Kitaibaraki (200 km south of site) 0.4 millirem/hr.

We are working on getting updated information on radiation and dose rates at and near the plant.

Station personnel not directly supporting reactor recovery efforts have been evacuated, leaving approximately 50 staff members at the site. Operators are no longer in the main control room due to high radiation levels.

Safety relief valves were able to be re-opened and seawater injection into the reactor core was restarted around 1 a.m. EDT on March 15 and is continuing.

Mexstan

Just read the news that the 50 workers remaining at the plant are doing so at the risk of their lives. Apparently they are all older guys who have elected to stay and do what they can to stop the radiation.

Onemoparnut

Now the news is saying that everyone has left the plant but who knows if they know what they are talking about or not

Dieseldude4x4

Don't know about the older guys thing but they are staying.
Latest word from last night through my secret source in the business says the reactors are still intact which is a good thing even as bad as it is.

bkrukow

This stuff is WAY over my head but how do you shut something like this down?? And if the shut down process has been started how long does it take. If it cant be shut down what is the ultimate end game?? I would asume that a Chernoble type scenario is a worst case scenario but if that happens how do you clean it up?? I realize that the radiation contaminated the surounding area at Chernoble and it uninhabitable but what happend to the nucliar material that was there??

Don M

Shutting down a plant is a long process, but even after the shutdown happens, the fuel rods have to be cooled for months in water pools. Usually as little as 6 weeks will cool them enough that they wont melt down though.

Under the reactor is a large core catcher, or if you will....a basin or large tub. If the water systems all fail and the rods cant be kept cool, the rods will melt and fall directly into this basin where they will spread out and cool on their own. This tub contains the melted rods, but lots of radiation will be released from the meltdown. If the surrounding buildings are intact then large amounts of radiation will not escape and damage will be limited to the local area.

If it all melts down and falls into the basin....water can be pumped into the basin at a later time to speed cooling of the whole mess. Refractory material or fire brick like material is what the basin is partially constructed of.

Reports are some of the rods are partially melted. Usually you have 2 plus weeks to get a new water loop circulating or started if all the others have failed. This tells me a pool wall or pool floor is leaking from cracks.

bkrukow

So if there is a leak and the water is dropping then why isent pumping new water in keeping this mess under controle? In my mind I am thinking that the way they are talking abought the water isues that they need a constant circulation of water to cool them and that because that isent happening stuff is overheating. I am completely dumb to this stuff but I am trying to learn. If Boron is a obsorbing agent why are tehy not pumping truck loads of it in to slow/stop the nucliar process or did they already and this mess is just a result of the left over heat that needs to cool and the radiation leaking is stricly from the exposed rods? I know lotsa questions and Ime probobly way off but I have never given any thought to how this stuff works and I am the type that likes to know.