Japan Earthquake: nuclear plants

eXorikos

Last time I checked with a proportional counter (friday) background (indoors) was 5-10cps...

The significance of those number also depends on the type of radiation and the place where the contamination is on/in the body. Just cps or cps says nothing really.

alxm

Well, it does seem to be where the explosion occured though. I just found this cutaway which at least seems to say as much. Although there seems to be a lot of conflicting information out there; one report claimed it occurred between the outside wall and a steel containment wall, which I'd interpreted as a Mark-III kind of containment, which isn't correct for the Fukushima reactor.

Yup, it'd require heavy investments though. A friend of mine was until recently involved in the upgrades in-progress at Oskarshamn, which is a BWR contemporary to Fukushima (although it's a different, ASEA design)

promecheng

The structure that was destroyed does contain the crane to lift the containment cover and is used during fueling operations. I'm not sure if it is considered secondary containment, but I do believe that it is a bit more secure than a simple metal enclosure. During refueling operations there is a small amount of radioactivity present and I believe the environment within the top portion of the building is controlled and not freely vented to the outside.

Another concern with the loss of the top part of the building is the spent fuel pool. I believe that the SPF is within the structure that was destroyed. If the water in the SPF was lost during the blast, the spent fuel can overheat and potentially melt. With no structure to contain the environment above the SPF any release of radiation would be freely vented to the outside.

Also, I believe that the unit-1 reactor is a BWR/4 design by GE with a MK-1 containment design. I believe this is typical with the wet-well torus design used to suppress a Loss of Coolant Accident (LOCA) within the primary containment. Any steam would be directed to the wet well where it would exit the venting system submerged, and thus condense and relieve any pressure buildup.

Astronuc

It does appear that the spent fuel pool is in the upper level of the contaiment, unless they have it in another building adjacent to containment.

I hope they are maintaining cooling there too.

It would appear from pictures that the overhead crane is probably damaged, and possibly the fuel handling machine(s).

Attached Thumbnails

 

edgepflow

Are the pumps they are using to pump seawater for reactor cooling motor driven or steam turbine driven? Are these the pumps designed for this emergency cooling or an alternate configuration?

promecheng

I think I read on TEPCO's, (Tokyo Electric Power Co.), website http://www.tepco.co.jp/en/press/corp...e/index-e.html that they were using Fire Pumps to inject seawater into the reactor. These are probably portable diesel-powered pumps that they have somehow hooked up to the Emergency Core Cooling System (ECCS), either the Core Sprayer system or the Low-Pressure Core Injection (LPCI) system. I think they still do not have AC power at the site to power their permanently installed pumping systems.

Basically these Fire Pumps are only used as a last resort, when all else fails. I know plants here in the U.S. also have Fire Pumps available in case of worst-case scenarios, like loss of site power and loss of all Emergency Diesel Generators.

promecheng

Here are some pictures and sketches of a BWR. I got them from a good site if your interested in learning more on nuclear power plants, http://www.nucleartourist.com/

Another cutaway of a BWR/3 or BWR/4 with MK-1 containment:
http://www.nucleartourist.com/imagemaps/rx-bldg1.jpg

Pictures of reactor building floor during refueling outage. I believe this is looking inside the part of the building that was destroyed:
http://www.nucleartourist.com/images/rflg-fl2.jpg
http://www.nucleartourist.com/images/rflg-fl1.jpg

Reactor head being lifted during refueling. They have already lifted the top of the primary containment, which is a very thick steel-reinforced concrete cover and weighs many tons. (notice people near reactor are wearing protective suits):
http://www.nucleartourist.com/images/headlift.jpg

Pictures of inside of torus:
http://www.nucleartourist.com/images/torus1.jpg
http://www.nucleartourist.com/images/torus2.jpg

Sketch of emergency cooling systems: (Note, this appears to be from a later design BWR, probably BWR/5 or BWR/6. The systems will be similar however for the BWR/3 or /4:
http://www.nucleartourist.com/images/nmp-g3.gif

PietKuip

I had used the latest release. The count rates are on page 13; "measured without shoes, though the first measurement exceeded 100,000 cpm" sounds like that was the highest reading the instrument could give.

The same pdf also says: "A radiation level exceeding 500 microSv/h was monitored at the site boundary (15:29, March 12)." Also this sounds as if the meters had maxed out.

Indeed, this is up to a 1000 times background levels. Maybe this was the origin of news reports mentioning that factor.

If a school yard gets contaminated like that, local agriculture is in big trouble.

PietKuip

It is not dangerous to have shoes on which give 100 000 counts per minute. Just take them off, rinse them, and your problem is solved. If it is on your body, just take a shower (if showers are working in the afflicted area).

But it seems indicative of a large surface contamination over quite a large area, which means that the amount of radioactivity that was released is large.

The Japanese authorities should be able to give estimates on how many becquerel of activity were released into the environment. This cannot have been a negligible amount.

lapsedgeo

As a lapsed geographer of many years (and a Mum) trying to explain not only the earthquake and the tsunami but also what on earth is going on with the reactors to her teenage son thank you for posting such helpful information - it's certainly keeping me up to date in a way that the media aren't.[

PietKuip

Another indication that there was a major release of radioactivity: Dutch radio just reported that the enhanced radiation levels at Onaga would be due to wind-driven activity from Fukushima.

This reminds me of how the Chernobyl accident first became public when radiation monitors at a Swedish reactor showed high levels of radiation.

Astronuc

Is one refering to Onagawa plant? What is meant by enhanced?

There is some concern about the spent fuel pool at FK-I, Unit 1 and whether or not it went dry. I would hope they have checked that.


NEI has put together a pretty informative page/site:
http://www.nei.org/newsandevents/inf...n-that-region/

The have a general BWR Mk I diagram
http://i1107.photobucket.com/albums/...orDesign_3.jpg

PietKuip

Yes, I meant the plant Onagawa plant. Levels were 21 microsievert or four times as much (depends on how one reads the information - maybe they have an alert level of 21 microSievert, levels were four times their alert threshold).

Anyway, if that indeed came from over 50 miles upwind, the release at Fukushima was gigantic. Which means that the authorities have been lying.

Vanadium 50

microsievert per what? 21 uSv is 2.1 mR. Typical backgrounds are 1 mR/day.

PietKuip

Sorry: microsievert per hour, according to this.

My point is not that it would be terribly dangerous at Onagawa, but that the amount of activity released at Fukushima was massive.

Astronuc

The cited report mentions 21 Sv, but not the time period, hr or day or otherwise.

1 μSv = 0.1 mrem
Nominal background = 2400 μSv/yr or about 0.27 μSv/hr
http://www.unscear.org/docs/reports/gareport.pdf

So the activity is not so clear.

Meanwhile - reports indicate that the activity at the Onagawa has returned to normal, so the increase in activity was transient rather than ongoing.

While the release of radioactive material from Fukushima is significant, it is premature to call it massive (and massive has not been quantified).

turbo

And where was it measured? When I was an environmental process chemist at a pulp mill, we measured emissions as far from the plant as legally allowable. Games that the EPA allows businesses to engage in.