Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[turbo]

You might also want to add that if the Generator has been disconnected from the Electrical Grid the Turbine would be driving a light load, even through the numerous reductions gears. The amount of steam to drive a turbine with a very light load is very small, while you can dissipate a lot of heat energy if the condenser is designed for that purpose.

For those who are first time readers, after you have a Reactor scram, you still have to dissipate a lot of heat. If a Reactor scrammed in an Earthquake it is most likely that the Turbine shut off valve also tripped to protect the turbine (as much as possible as the Earth is jumping.)

The only place where you can send the reactor steam is to the condenser.

I don't know how nuclear plants are designed, but the GE turbine-generators in conventional power plants are set to trip on very low radial excursions. Self-defense for the turbines. The quake probably tripped the turbines even before the reactors were scrammed.

 

[TCups]

OFF TOPIC, UNSOLICITED, BUT IMPORTANT

For the last 2 weeks, this forum has been an invaluable source of information and the exchange of ideas with some experts in the field that I would never have had access to otherwise. Actually, invaluable is the wrong word -- valuable is a better word. Valuable enough that I chose to make a contribution to the site to support it and the work it does.

All of you should think about doing the same. And after you think about it, then click on that little "Upgrade" button up there and chip in.

Thanks PhysicsForums.com for being here for all of us.

 

[Joe Neubarth]

I don't know how nuclear plants are designed, but the GE turbine-generators in conventional power plants are set to trip on very low radial excursions. Self-defense for the turbines. The quake probably tripped the turbines even before the reactors were scrammed.

I bet it was a tie. A trip of the steam valve to the turbine more than likely trips the rods in the Reactor.

 

[jensjakob]

http://www.areva.com/EN/news-8795/a...tions-for-b--barre.html?xtmc=fukushima&xtcr=1

Interesting reading.

 

[jensjakob]

0:27 and 1:31 - gives you an idea of the size of the RV cap. I don't think it has blasted anywhere.

But good illustratitions and good narrative.

 

[TCups]

0:27 and 1:31 - gives you an idea of the size of the RV cap. I don't think it has blasted anywhere.

But good illustratitions and good narrative.

There is a song about that . . .

"History shows again and again
how nature points out the folly of men.
Oh, no! There goes Tokyo!
Go, Go! Godzilla"

Blue Oyster Cult

PS: Love the new hat, G!
(sorry, someone had to post it, and I needed a bit of comic relief)

 

[britinjapan]

I just joined the forum, and tried to post a new thread but cannot find it. Apologies if it`s becuase I`m new, but I had a few quations about practically living in Tokyo. Any views would be appreciated.

1. Is the level of 0.30 micro-sieverts for a long period of time dangerous?

2. Iodine 131 and Cesium 134 and 137 are in drinking water (http://ftp.jaist.ac.jp/pub/emergency/monitoring.tokyo-eiken.go.jp/monitoring/w-past_data.html). Only one type of Cesium has been on the news. Any advice for these levels or types?

3. At what point does one leave for safety - either moving South or out? An explosion? At what radiation levels? When the Japanese Government make the radius 100km?

4. I`ve just recently heard about the MOX in reactor number 3. For the novice, any advice on what precautions to take?

Many thanks for a fine forum, and any views appreciated.

Rgds

 

[|Fred]

The by-pass is done to protect the turbine. It is afterall a steam turbine, not a water turbine. The low pressure turbine has espeically long blades that could be damage if they where sloshing through water. The by-pass is usually done with a minimal flow of steam.

I'm sorry there must be something I'm missing, as I do not understand:
When the core eventually cool down water will be below boiling point and no water will go into the turbines anyhow. Further more in the event that the core does not cool down like in the present case wouldn't it had made sens to switch back to the turbine, once they saw they had no power. The turbine would have help to cool down the stream and would have produce usefull electricity etc..

Basically I'm suggesting to run a power plant on beta decay energy. In a similar way one could try to slow down a car in a down slope, engine off with a gear engage.

I'm probably failing at a low level of understanding and would appreciate if some one could set me strait on this.

 

[turbo]

I'm sorry there must be something I'm missing, as I do not understand:
When the core eventually cool down water will be below boiling point and no water will go into the turbines anyhow. Further more in the event that the core does not cool down like in the present case wouldn't it had made sens to switch back to the turbine, once they saw they had no power. The turbine would have help to cool down the stream and would have produce usefull electricity etc..

Basically I'm suggesting to run a power plant on beta decay energy. In a similar way one could try to slow down a car in a down slope, engine off with a gear engage.

I'm probably failing at a low level of understanding and would appreciate if some one could set me strait on this.

If the steam feeding the turbine is not properly superheated and then accurately desuperheated before the initial feed stage, the pressure-drops across the stages and the tweaking between stage-groups will not work properly. You can't feed wet steam to a steam turbine without tearing it up. For that reason, you can't ramp down turbine-feed steam temperature/saturation during a shut-down. The feed systems aren't able to handle it.

 

[Astronuc]

1 kilorem (krem) = 10 sievert (Sv)
1 rem (rem) = 10 millisievert (mSv)
1 millirem (mrem) = 10 microsievert (µSv)
1 microrem (µrem) = 10 nanosievert (nSv)

or
1 sievert (Sv) = 100 rem (rem)
1 millisievert (mSv) = 100 millirem (mrem)
1 microsievert (µSv) = 100 microrem (µrem)
1 nanosievert (nSv) = 100 nanorem (nrem)

For typical exposures, see
http://www.new.ans.org/pi/resources/dosechart/

At sea-level, a typical annual exposure is something like 26 mrem per year or 0.003 mrem/hr = 3 µrem/hr or 0.03 µSv/hr. 0.3 µSv/hr, would be ten times normal, but it is not expect to last long. It should not be significant, but if one is uncomfortable with that, then one could drink bottled water or use a filter. External use should be OK.

I've heard the mention of Cs-137, but there is normally Cs-134. I'm not sure why it is not included. I have also heard that some radioiodine is in the water. Children should not drink water with radionuclides present.

When one leaves is a personal choice. If the radiation levels were increasing or stayed at a persistent level, then one might consider leaving. However, there are other options, such as drinking bottled water.

The irradiated MOX fuel should not be significantly different than irradiated UO2 fuel. Ideally, most of the irradiated fuel is confined within containment or at the plant, although it appears some might have founds its way into the ocean (?).

 

[Borek]

1. Is the level of 0.30 micro-sieverts for a long period of time dangerous?

0.30 μSv is a dose - and is perfectly safe, comparable with with a dose you can get from chest x-ray. However, as you ask about long period of time I guess you think about intensity - but intensity is expressed in Sv/time unit, be it μSv/day, mSv/hour or something similar. So, not knowing time unit it is impossible to answer your question.

Take a look here: http://xkcd.com/radiation/ but remember is speaks about doses, not about intensity.

 

[Astronuc]

I'm sorry there must be something I'm missing, as I do not understand:
When the core eventually cool down water will be below boiling point and no water will go into the turbines anyhow. Further more in the event that the core does not cool down like in the present case wouldn't it had made sens to switch back to the turbine, once they saw they had no power. The turbine would have help to cool down the stream and would have produce usefull electricity etc..

Basically I'm suggesting to run a power plant on beta decay energy. In a similar way one could try to slow down a car in a down slope, engine off with a gear engage.

I'm probably failing at a low level of understanding and would appreciate if some one could set me strait on this.

The beta decay just doesn't provide enough energy or steam to be use in the turbine. Nuclear plant steam turbines have essentially no superheat - the steam is essentially saturated. From my experience, turbines are normally engaged at about 12-14% power. It has to do with the moisture or 'wetness' in the steam, particularly in the low pressure turbine.

 

[|Fred]

Hi BritinJapan

A long exposure to 0.30 micro-sieverts /h is nothing to worry about http://xkcd.com/radiation/ actually if you go skying in the Alps this is more or less the kind of radioactivity you'll get .. So as long as you are not worried to get irradiated when you go skying you should be ok .

Cesium 134 has a short half life, every 3.16 Days half of the Ce134 decay.
As far as advise are concerned you can follow Japanese official advise , or get bottle watter for a few weeks / months .. assuming you drink watter, beer or coke will do just fine otherwise. (the regular diet of many people btw :roll )

I guess it depends where you are and how the situation evolve.

As far as Mox is concerned I don't think it changes anything really ... If heavy metal isotopes from the fuel get airborne in a big fire,in my opinion it will be just as bad (but may be I should be more picky as far as witch Actinide will kill me )

 

[britinjapan]

0.30 μSv is a dose - and is perfectly safe, comparable with with a dose you can get from chest x-ray. However, as you ask about long period of time I guess you think about intensity - but intensity is expressed in Sv/time unit, be it μSv/day, mSv/hour or something similar. So, not knowing time unit it is impossible to answer your question.

Take a look here: http://xkcd.com/radiation/ but remember is speaks about doses, not about intensity.

Apologies - I meant 0.30 micro sieverts per hour. That is the current level of radiation in Tokyo at the upper level of private measurers. The officlai levels seem around half that.

The following is micrograys per hour over the past few weeks

http://ftp.jaist.ac.jp/pub/emergency/monitoring.tokyo-eiken.go.jp/monitoring/past_data.html

Thanks

 

[britinjapan]

I've heard the mention of Cs-137, but there is normally Cs-134. I'm not sure why it is not included. I have also heard that some radioiodine is in the water. Children should not drink water with radionuclides present.

[/QUOTE]

Thanks for the views. There is both Cesium 134 and 137 in water. 0.92 and 1.22 Bq/Kg.

Rgds

Source http://ftp.jaist.ac.jp/pub/emergency/monitoring.tokyo-eiken.go.jp/monitoring/w-past_data.html

 

[|Fred]

I understand, but the fact that it is 10x what it was before does not mean it is to be considered concerning or high.. Check the radiation "level" in town in Europe, you'll see.
0.30 uSv/H assuming you are 24/7 exposed give you 2.6mSv/year the exact same radiation a Brit or a French is expose every year and about a third of the one in Sweden.

 

[Dancewithbear]

I have a couple of cooling questions. In a document I read it was indicated that Liquid Tin with inert gases could be injected to cool the reactor. Actually I think it said chopped tin but the idea was taken from Chernobyl where they used lead to cool the remains before the entombment with sand and concrete. Advantages stated were no circulation required, no/low RPV pressure, unlikely to lose coolant. They were recommending Tin because it was less toxic.

Would this be feasible in a BWR? Would you add Boron as well?

Secondly there is the issue of SFP cooling where it would seem Tin would not be suitable as the temps may be too low. Would it be feasible to use Gallium or Gallium-Boron?

 

[|Fred]

here is the proposition more in detail... (I have no clue)

The Ukrainian plan suggests that to bring the heat processes in Fukushima-1 reactors under control, it is necessary "first, to ensure a normal cooling mode in the spent fuel pools by pumping water, sea water as a last resort, into them; second, the type of reactor fuel coolant needs to be changed – water should be replaced with low-melting and chemically neutral metal, for instance tin, which will pull heat away from the fuel rods (molten or damaged) towards the inner walls of the reactor, while continuing to use sea water to cool down its outer walls". The tin 'lake' inside the reactor will "reduce the discharge of heavy fission products and bring ionizing radiation levels down. Chipped tin could be pumped in through steam communications under pressure using cylinders with helium or argo

otherwise they installed pumps that will pump the leaked turbine basement water to the condenser (of 1.2 and 3)

 

[shadowncs]

I have a couple of cooling questions. In a document I read it was indicated that Liquid Tin with inert gases could be injected to cool the reactor.

When I read that first (some Russian professor's suggestion if I remember) I thought gee, that's an out of the box idea. The problem I see (and I'm not an expert) are how do u cool the molten tin? In Chernobyl it would act as a heat sink to the huge concrete building, I guess. But here - the RPV is isolated. Where would that heat go?
As someone suggested here, Chernobyl was probably an easier problem to solve once it burned down. Hell, the core was all over so a more dissipated source of heat than a BWR.

Now if the RPV would be breached & core was on concrete I would see value in such an idea: drop tin in the containment to dissipate the heat. Let's all hope it won't be the case here...

Edit: after reading Fred's quote, it makes some sense. Tin is the heat sink from fuel to RPV, then water cools that.

 

[Dancewithbear]

Some other references I read on the topic of Liquid Metal cooled reactors indicated that LM cooled reactors have been used/studied for 50 years. Sodium seems to be the most predominate probably because of the temperature range and thermal transfer properties.

 

[Dancewithbear]

When I read that first (some Russian professor's suggestion if I remember) I thought gee, that's an out of the box idea. The problem I see (and I'm not an expert) are how do u cool the molten tin? In Chernobyl it would act as a heat sink to the huge concrete building, I guess. But here - the RPV is isolated. Where would that heat go?
As someone suggested here, Chernobyl was probably an easier problem to solve once it burned down. Hell, the core was all over so a more dissipated source of heat than a BWR.

Now if the RPV would be breached & core was on concrete I would see value in such an idea: drop tin in the containment to dissipate the heat. Let's all hope it won't be the case here...

Edit: after reading Fred's quote, it makes some sense. Tin is the heat sink from fuel to RPV, then water cools that.

Could you fill the RPV with LM and let the heat transfer to the flooded containment through the RPV wall? I don't know.. is there a heat exchanger in the RPV for say steam to the turbine?

 

[Reno Deano]

Why is it that in case of a shut down they bypass the turbine and route the steam directly to the condenser ?

Faster steam (heat) removal from the reactor and cooling of the steam. Extract steam is still used to run HPSI and LPSI, if needed. Plus if loose particles are considered (you never immediately know what caused a shut down) you would want to protect the next costly item in the plant and the item that gets the plant income.

 

[Bodge]

Latest SEA Water analysis (unfortunately only available in Japanese at the time...) Source Nisa
http://k.min.us/ijHnOk.jpg

edited with English version from tepco http://www.tepco.co.jp/en/press/corp-com/release/11032603-e.html
[PLAIN]http://k.min.us/ijHpSg.jpg

@AntonL
Sewage pipes does not mean SFP but pipes linking the core to the turbine

Why do Tepco use E-notation to express these numbers? They are nonsensical to the vast majority. Why not say 50,000 bec/litre of Iodine-131 for example? (per IAEA 26th March)

Can somebody please explain their way of expressing numbers? I understand normalised scientific notation, e.g. 5x10^4

Edit: Tepco are discussing cubic centimeters, IAEA litres: 1000/1 difference

 

[Joe Neubarth]

Apologies - I meant 0.30 micro sieverts per hour. That is the current level of radiation in Tokyo at the upper level of private measurers. The officlai levels seem around half that.

The following is micrograys per hour over the past few weeks

http://ftp.jaist.ac.jp/pub/emergency/monitoring.tokyo-eiken.go.jp/monitoring/past_data.html

Thanks

I'm 63. Because of two tumors I have had three CAT scans in the past two years. I do not even know what the dose rate if for a CAT scan, but I am willing to bet that I have received a lot more radiation from those CAT scans than you will be exposed to in Tokyo in the next year. I am still alive and the tumors are benign. I have a theory that a little radiation is good for you as it gives your body something to do.

 

[Dancewithbear]

When I read that first (some Russian professor's suggestion if I remember) I thought gee, that's an out of the box idea. The problem I see (and I'm not an expert) are how do u cool the molten tin? In Chernobyl it would act as a heat sink to the huge concrete building, I guess. But here - the RPV is isolated. Where would that heat go?
As someone suggested here, Chernobyl was probably an easier problem to solve once it burned down. Hell, the core was all over so a more dissipated source of heat than a BWR.

Now if the RPV would be breached & core was on concrete I would see value in such an idea: drop tin in the containment to dissipate the heat. Let's all hope it won't be the case here...

Edit: after reading Fred's quote, it makes some sense. Tin is the heat sink from fuel to RPV, then water cools that.

Any thoughts about using Liquid Gallium for the Spent Pool cooling. Gallium melts at ~29.76C (85.57F) and boiling point at 2204C/3999F.

I think you could easily add a heat exchanger to the spent pool.

 

[britinjapan]

I'm 63. Because of two tumors I have had three CAT scans in the past two years. I do not even know what the dose rate if for a CAT scan, but I am willing to bet that I have received a lot more radiation from those CAT scans than you will be exposed to in Tokyo in the next year. I am still alive and the tumors are benign. I have a theory that a little radiation is good for you as it gives your body something to do.

Thanks for that! All the best on your health Sir!

I imagine though that external and internal (ingested) radiation is a little different - so I`m avoiding drinking water for the moment...cheers (good reason to drink beer!)

 

[Bodge]

Just thought, re. my last post on E notation - does E equal 10 ?

 

[Bodge]

Cheers Joe, sounds like you've had a good old dose of gamma there - gives you superpowers in the end ;)

 

[downwinder]

I've heard the mention of Cs-137, but there is normally Cs-134. I'm not sure why it is not included. I have also heard that some radioiodine is in the water. Children should not drink water with radionuclides present.

The amount of Cs-137 and Cs-134 is predictable by the fission yield curves. In this situation where we have fresh fission products the ratio should be constant. see this link.
http://en.wikipedia.org/wiki/Nuclear_fission_product"

 

[Astronuc]

Just thought, re. my last post on E notation - does E equal 10 ?

Yes E is used instead of 10^. It's quite common, especially to those who are familiar with Fortran.