Japan Earthquake: nuclear plants

andyr

Unfortunately the media decided to tell a Hollywood blockbuster story at a time when they could reassure and educate the masses. Just read through this entire thread, it will quickly change your perspective.

In future though, take mainstream populist news channels with a pinch of salt.

PietKuip

Which is very scary reading. Operators have abandoned the control room: nobody in the driving seat anymore.

marwood

DrDu doesn't seem very impressed with the ''scientific data'' being presented on the nei.cachefly.net site.

The reported decline in radiation levels to 60millirems/hr is over 2000 x background radiation levels, suggesting ?? ongoing emissions from the No.2 reactor steam venting? or from a leak in the No.2 reactor containment? or contamination of the ground area by emissions from the No.4 spent fuel pool fire? According to http://english.kyodonews.jp/news/2011/03/78352.html

''The utility firm said later in the day the massive radiation amount of 400 millisievert per hour, or 400,000 microsievert, was recorded around debris in front of the No. 3 reactor and that the material may have come from the nearby No. 4 reactor.''

As far as best, most likely, and worst case scenarios, as economic theory claims, accurate information is costly, especially when agents have incentives to conceal it (http://www.guardian.co.uk/world/2011...-up?CMP=twt_gu), so there is not sufficient information to make anything but speculations about most likely scenarios. For best case check the nuclear engery promoters opinions eg http://bravenewclimate.com/2011/03/1...ar-earthquake/ and for the worse case scenario see the anti-nuclear environmentalists opinions eg http://www.ucimc.org/content/meltdow...shima-reactors.

Seems that the No.1 and No.3 reactors are toast and will have to be de-constructed and recycled. The No.2 reactor may be recoverable after a 3 or 5 year down period for inspection and repair. Haven't seem much about the likely costs ...

aamrwc

The advice to ignore populists news channels is what I am trying to do. Hence, this is why I am here. I have read this complete thread and have not found a concise Best case, Most likely and Worst case outcome in layman's terms. Responses so far have not been useful. There is a lot of interesting info here but its is fragmented. Could really use the help. Thanks

marwood

Summary of each Fukushima Daiichi NPP reactor as of late Tue 15th Tokyo time.

http://www.jaif.or.jp/english/news_i...300189582P.pdf

Looks like No.2 is being cooled with seawater -- so will be non-recoverable.

promecheng

I wonder how much function they actually lose by abandoning the control room. It seems the site is still in "blackout", with no off-site or on-site electricity available to power any RHR or ECCS pumps or systems. Additionally, from reports it seems that their instrumentation is questionable as well, (RPV/containment level vs. pressure vs. radiation not agreeing). I am guessing that their current priorities are to make sure they keep the portable fire pumps fueled, ensure adequate seawater in the suction pit for the pumps and make sure they vent containment/RPV so as to prevent an overpressure situation and keep pressure low enough to be able to keep on pumping into those areas. On top of this they maybe trying to figure out how to get water back into one, or several spent fuel pools to prevent overheating. What's really concerning is unit 2 and the extent of the damage to the primary containment.

God bless the operators and workers still at the site. These people are heroes!

aamrwc

Thanks Marwood. These weren't of much use. I'm looking for rational analysis not emotion.

promecheng

The problem is there is not enough information on what has happened or what is currently happening at the site to make any useful predictions.

Additionally, there is no video feed into the reactor. Operators determine the state of the reactor through measurements of temperature, pressure, fluid flow, surrounding area radiation, etc. This information feeds into the control room.

Edited incorrect and speculative comments.

Reno Deano

If they abandon the control room it is for a good reason. They then go to the emergency remote control room. Most of the fuel within the spent fuel pool has been cooling for 1.5 to 3 years or more. The spent fuel pool does also contain fuel rods that have been removed from fuel bundles due to damage detected during a previous refueling, and reconstituting of a fuel bundle.

Here is a time line html of some interest: http://online.wsj.com/article/SB1000...%3Dinteractive

Reno Deano

US NRC issues analysis of Japanese actions:

http://www.nrc.gov/reading-rm/doc-co...011/11-049.pdf

promecheng

Is the suppression pool torus on the MK-1 design considered part of primary containment?

Reno Deano

NEI WEB UPDATE AS OF 2:15 P.M. EDT, TUESDAY, MARCH 15:

Excerpt: An explosion at Unit 2 of the Fukushima Daiichi plant earlier today has damaged the suppression chamber, which holds water and steam released from the reactor core. Personnel not directly supporting recovery efforts have been evacuated from the plant, with about 50 employees remaining, principally to restore cooling water in the reactors.

Later in the day, water level inside the Unit 2 reactor was measured at 1.7 meters below the top of the fuel rods, but it was rising as workers pumped sea water into the reactor, reports said.

Tokyo Electric Power Co. said that an oil leak in a cooling water pump at Unit 4 was the cause of a fire that burned for approximately 140 minutes. The fire was not in the spent fuel pool, as reported by several media outlets. Unit 4 was in a 105-day-long maintenance outage at the time of the earthquake and there is no fuel in the reactor.

Astronuc

Yes - it is in the volume that contains the pressure vessel and recirculation system.

If there is no fuel in the core of Unit 4, it means they did a full core offload - and the fuel resides in the SFP or other pool. I've seen thermals coming off older fuel.


This gives a pretty decent explanation of what got the plant in its present situation.
http://blogs.forbes.com/christopherh...shima-daiichi/

I don't necessarily agree with the conclusion/remedy regarding fluoride salt fueled reactors.

Texan99

Suppose a nuclear reactor were successfully shut down with control rods, but then the cooling system immediately failed and no one managed to do a single thing to get it running again. Does anyone really know whether the containment vessels currently in use should be expected to contain the whole meltdown without any significant release of contamination? In other words, I guess steam would build up in there like crazy, but is the vessel up to that task? Or is that just untested territory? In Three Mile Island, for instance, I've read that the core melted down about halfway without breaching the vessel, but I don't know how well the cooling system was functioning.

Special thanks to Reno Deano and Promechang, among others, for your very helpful posts for us laymen.

Texan99

What is the impact, if any, of a breach of the suppression pool torus on the ability of the containment vessel to hold in all the fissile materials? I mean, suppose you hacked a big hole in the torus. Could melted fuel run out there?

Astronuc

Some background on TMI-2's accident.
http://www.nrc.gov/reading-rm/doc-co...mile-isle.html

IF the Fukushima plant was able to cool the core, i.e., IF the EDGs had not failed and been able to cool the plants - we wouldn't be having this conversation.

But the ability to cool the cores of Units 1, 2 and 3 failed! That's the critical matter. One unit by itself is bad enough, but three units is three times as bad.

In a normal plant - all the fuel rods could fail. It doesn't matter outside of the utility, as long as the activity is contained in the primary system, and plants are so designed - with the assumption that they have cooling capability so that they primary systems doesn't build up pressure which has to be released. At Fukushima, they lost the cooling capability and that forced the release of fission products into the environment.

Now all other LWR (PWR and BWR) operators must ensure that their own plants will not suffer the same fate.

Astronuc

It depends on where the breach leads to. As long as the breach doesn't lead to the environment, that doesn't affect the public - only the staff that have to deal with whatever part of containment is directly affected by the breach.

Ideally, the fission products stay within the pressure vessel - except for those that have been vented. Otherwise, any fission product in the cooling water that ends up in the torus, will either stay in the torus, or within the primary containment.

Contamination of containment would be a complication of further operation - or complication for decommissioning.