Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[TCups]

So I guess containment, even in the case of a powerful explosion is factored into the design. The design seems to be such that energy from an explosion would be partially channeled either sideways or down or both. In the absence of more information I think I'll avoid speculation.

There is the problem of radioactive contamination from Unit 3. Specifically, this evidence I again summarize and put forward to review. It has been previously released by various sources and discussed in several of the preceding posts in this thread:

1) the timeline of radiation spikes shows the highest spike immediately following the blast at Unit 3.

2) it was reported that workers were initially pulled back after the explosion at Unit 3 because of concern of radiation after the blast.

3) it was reported access to Unit 3 was temporarily limited by high level radiation on the ground

4) it was reported that military tanks with dozer blades were to be brought into clear the radioactive debris so work could continue (no pictures of that I have seen, or confirmation that it actually happened as far as I know).

5) an unsourced diagram that showed the locations of the highest levels of measured radiation on the ground around Fukushima 1,2,3 and 4 shows the highest levels around Bldg 3 and has a positive correlation with visible debris blasted from the east, west, and south sides of Bldg 3, including some higher readings on the east side of Turbine Bldg 3 where side wall panels of Reactor Bldg 3 blew across the roof.

A counter hypothesis might be that the explosion at Bldg 4 was from the SFP and SFP4 hydrogen production, and that this may have been the source of high level radioactive debris (less likely, IMO). Even so, if that were possible, then it is equally possible that the same mechanism may have been at play in whole or in part in the explosion of Bldg 3.

Therefore, I conclude that the blast from Unit 3 carried high level radioactive waste with it.

If so, then regarding this high level waste in the explosion debris of Unit 3:
1) was it from the spent fuel pool of 3?
2) was it from the (damaged) reactor core of Unit 3?

Ultimately, those would seem to be the only two sources of high level ground debris.

3) how could an explosion, if powered only by vented hydrogen from the containment of Unit 3, and originating from the top floor of Bldg 3, disperse high level waste as ground debris from either of these sources?

Think about it.

 

[M. Bachmeier]

There is the problem of radioactive contamination from Unit 3. Specifically, this evidence I again summarize and put forward to review. It has been previously released by various sources and discussed in several of the preceding posts in this thread:

1) the timeline of radiation spikes shows the highest spike immediately following the blast at Unit 3.

2) it was reported that workers were initially pulled back after the explosion at Unit 3 because of concern of radiation after the blast.

3) it was reported access to Unit 3 was temporarily limited by high level radiation on the ground

4) it was reported that military tanks with dozer blades were brought into clear the radioactive debris so work could continue (no pictures of that I have seen).

5) a diagram that showed the locations of the highest levels of measured radiation on the ground around Fukushima 1,2,3 and 4 shows the highest levels around Bldg 3 and has a positive correlation with visible debris blasted from the east, west, and south sides of Bldg 3, including some higher readings on the east side of Turbine Bldg 3 where side wall panels of Reactor Bldg 3 blew across the roof.

A counter hypothesis might be that the explosion at Bldg 4 was from the SFP and SFP4 hydrogen production, and that this may have been the source of high level radioactive debris (less likely, IMO). Even so, if that were possible, then it is equally possible that the same mechanism may have been at play in whole or in part in the explosion of Bldg 3.

Therefore, I conclude that the blast from Unit 3 carried high level radioactive waste with it.

If so, then regarding this high level waste in the explosion debris of Unit 3:
1) was it from the spent fuel pool of 3?
2) was it from the (damaged) reactor core of Unit 3?

Ultimately, those would seem to be the only two sources of high level ground debris.

3) how could an explosion, if powered only by vented hydrogen from the containment of Unit 3, and originating from the top floor of Bldg 3, disperse high level waste as ground debris from either of these sources?

Think about it.

Well I've been considering some of the orange debris and wondered if some of it might not be a portion of the dry-well cap. And in keeping with your theory, a heavy steel dome shaped cap would be like the plate used in an explosive device for directional control (directional charge). In a dome like structure the point where it is attached to the upper reactor would seem a likely weak point, not to mention concerns that have been mentioned in the past about ensuring proper dry-well mounting.

If the orange debris is 3/4 inch steel section from the cap it would match your description sideways then upper energy release at unit 3.

 

[|Fred]

I've started to create this using all released data.. but it's kind of taking me to much time since I'm not using the appropriate tool (picture editor)
[PLAIN]http://k.min.us/imgwBU.gif

 

[TCups]

Well I've been considering some of the orange debris and wondered if some of it might not be a portion of the dry-well cap. And in keeping with your theory, a heavy steel dome shaped cap would be like the plate used in an explosive device for directional control (directional charge). In a dome like structure the point where it is attached to the upper reactor would seem a likely weak point, not to mention concerns that have been mentioned in the past about ensuring proper dry-well mounting.

If the orange debris is 3/4 inch steel section from the cap it would match your description sideways then upper energy release at unit 3.

Somewhere, way back there, there was a post about the color scheme of painting various equipment in a nuc power plant. In short, there may be lots of stuff painted different colors, including red.

I doubt that the drywell cap has been completely blown off and even if so, that it were blown, it was not exploded, shrapnel-like, into many small pieces. More likely, it would be yet another bullet-like projectile, along with the drywell plug. But that is just my SWAG (scientific wild - guess) vs. WAG (wild - guess). Remember that the cap would tend to vent hydrogen gas into the upper portions of the dry wall containment and region of the fuel transfer chute and gate under as little as 2 ATM of pressure, if previous post references are correct.

 

[curious11]

for graphs, use open office calc...
http://www.openoffice.org/

 

[AntonL]

Refering to https://www.physicsforums.com/showpost.php?p=3210895&postcount=1342" and below plan the building is about 125 meters long (google earth)
then the flooded area is about 1650 m2

Pools of water that may have seeped from either the reactor cores or spent fuel pools were
also found in the turbine buildings of the No. 2 and No. 4 reactors, measuring up to 1 meter
and 80 centimeters deep, respectively, while those near the No. 1 and No. 3 reactors were
up to 40 cm and 1.5 meters deep.

1 40cm
2 100cm
3 150cm
4 80cm
confirms that the source of the water is from unit 3 and has leaked into the neighbouring
units through cable tunnels. The cable tunnels would be fire proofed between the buildings
restricting the flow hence the varied heights

at the time of measurement volume of water is about 6000m3

 

[timeasterday]

I've started to create this using all released data.. but it's kind of taking me to much time since I'm not using the appropriate tool (picture editor)

What is the significance of the red line at 4 atm?

 

[havemercy]

March 25' Areva's analyses of the case, i don't know if it is usefull or useless

http://www.scribd.com/doc/51564602?secret_password=th7hw1mmpjwnfmd0mbj

 

[Astronuc]

What is the significance of the red line at 4 atm?

That is supposed to be about the maximum design pressure of the primary containment. In theory it should hold for a pressure somewhat above 4 atm.

 

[|Fred]

Yes Astronuc, and according to this gentleman it sustained up to 8 before leaking http://www.ustream.tv/recorded/13414000
Now, What I 'm not sure to have right is: is this value is for the core (primary) or the drywell

 

[AntonL]

Yes Astronuc, and according to this gentleman it sustained up to 8 before leaking http://www.ustream.tv/recorded/13414000
Now, What I 'm not sure to have right is if this value is for the core (primary) or the drywell

refer to the attached for specification

 

[Dancewithbear]

Can anyone direct me to information that would help quantify the differences in meltdown scenarios between MOX and non MOX fuel reactors?

i.e. all things being equal what is the additional risk?

Can we reasonably quantify it as some percent (5%) worse due to higher PU levels?

TIA, DWB

 

[|Fred]

Can anyone direct me to information that would help quantify the differences in meltdown scenarios between MOX and non MOX fuel reactors?

Of course post n°590 of this Thread
https://www.physicsforums.com/showpost.php?p=3198811&postcount=590

Courtesy of Google MOX+www.physicsforums.com

 

[Ivan Seeking]

I have a mundane question. Is Plutonium more toxic or radioactive than Uranium? I thought it was, but a spokesman from the Nuclear Safety Agency specifically denied this. Other "experts" seem to contradict his statement.

 

[Astronuc]

I have a mundane question. Is Plutonium more toxic or radioactive than Uranium? I thought it was, but a spokesman from the Nuclear Safety Agency specifically denied this. Other "experts" seem to contradict his statement.

Pu isotopes have shorter half-lives than the two main U isotopes, U-235 and U-238. Radiologically, the same number of atoms of Pu would be more radioactive.

Uranium dioxide fuel contains up to 5% U-235. The FK BWR fuel should have a peak enrichment around 4% U-235.

MOX might contain about 5%, which would be a mix of Pu-239, 240, 241 and 242. Pu-240 and Pu-242 also undergo spontaneous fission.

See attached figure.

 

[Ivan Seeking]

Pu isotopes have shorter half-lives than the two main U isotopes, U-235 and U-238. Radiologically, the same number of atoms of Pu would be more radioactive.

So he was lying? It was a flat denial. Could there be any other explanation for his answer?

 

[Joe Neubarth]

I have a mundane question. Is Plutonium more toxic or radioactive than Uranium? I thought it was, but a spokesman from the Nuclear Safety Agency specifically denied this. Other "experts" seem to contradict his statement.

Chemical Toxicity I believe would be a yes. You do not want to snort Plutonium Oxide dust.

 

[Astronuc]

So he was lying? It was a flat denial. Could there be any other explanation for his answer?

I don't know the context. If he was referring to fresh fuel, he would be wrong. He might be thinking of irradiated UO2 and MOX fuel, which develop a similar array of fission products. In fact, UO2 becomes MOX fuel as it is irradiated.

How Pu is radiologically more hazardous than U.

Chemically, both being heavy metals, they may be comparable in toxicity.

 

[|Fred]

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

 

[AntonL]

Here is a time line of the explosions and reported CV venting
Unit 1 - 12.03.2011 at 15:36 : CVv 15:00 on 12.03.11
Unit 3 - 14.03.2011 at 11:01 : CVv 09:20 on 13.03.11
Unit 4 - 15.03.2011 at 06:14
Unit 2 - 15.03.2011 at 06:20 : CVv 11:55 on 13.03.11

There is a correlation between Unit 1 CV venting and Hydrogen blast.

Below SFP data FU = fuel units followed by pool volume and heat load of the FU
Unit 1 - 292 FU 1200m3 60kW
Unit 2 - 587 FU 1425m3 400kW
Unit 3 - 514 FU 1425m3 200kW
Unit 4 - 1331 FU 1425m3 2000kW + 200 brand new FU (yes 2MW not a typo)

This sets a new light on my earlier proposal
Unit 1 exploded due to H2 leak of venting system - possibly Earth quake damage
[STRIKE]Unit 2 to 4 exploded due to hydrogen generation from equipment pools.[/STRIKE]

https://www.physicsforums.com/attachment.php?attachmentid=33572&stc=1&d=1301164813

From above slide, and knowledge gained I revise what I posted earlier

Unit 1 - Explosion after venting - H2 leak in venting system
Unit 2 - Explosion at Torus - Torus has small leak, possibly a crack allowing H2 to vent.
Unit 3 - Explosion due to H2 leak at PVC-dome due to high pressure
Unit 4 - Explosion due to H2 generated in SFP
Core damage in all three working reactors.
And the water leak problem still to be found

Four units and four different failure modes leads to one conclusion:
BWR are not as safe as they are said to be. It is time to switch them off.


Conclusions already made by industry experts (see attached pdf file)
1. All existing power plants' passive emergency cooling systems (BWR's
RCIC and PWR's turbine-driven auxiliary feedwater system) should be inspected
and reinforced to assure their reliability during adverse condition. Onsite
emergency generators should be further protected.
2. PWR is more resilient than BWR because of its steam generator secondary
water inventory and size of containment. This gives larger margin to core damage
and containment failure. Further review is still necessary to improve the safety
level.
3. Spent fuel pool safety has been grossly overlooked. A hardened and
independent top spray system is necessary for all nuclear power plants.

Please read attached pdf file - the most authoritative analysis yet found.

 

[JUrban]

Regarding the multimile US hose reel systems in Okinawa I mentioned earlier that are now under consideration, and contaminated water handling now underway by tepco, I was considering the feasibility of pumping back into local lakes that are drained for freshwater via hose reel systems. They would of course first be lined by geomembrane to prevent groundwater intrusion. Ideally the lakes could concentrate the contamination via evaporation to then at sufficient concentration be drained, perhaps into collapsible membrane tanks.

The question I have is based on what we know about the radioisotope species in that basement water, would they be effectively concentrated via evaporation ponds?

 

[dave2004]

I have a mundane question. Is Plutonium more toxic or radioactive than Uranium? I thought it was, but a spokesman from the Nuclear Safety Agency specifically denied this. Other "experts" seem to contradict his statement.

I found something here:
http://www.tpub.com/content/doe2/doe-std-1128-98_ch1/doe-std-1128-98_ch10039.htm

"...The radiological toxicity of reactor-produced plutonium far exceeds the
chemical toxicity of this heavy element..."
..."In contrast to uranium, the chemical
toxicity of plutonium is insignificant in comparison to the hazard arising
from its natural radioactivity." Moreover, "the toxicity of plutonium and
other transuranic elements," according to Voelz et al. (1985), "has only
been studied in animals since acute toxicity has never been observed in
man for these elements and epidemiologic studies have not produced
positive results." ...

 

[Reno Deano]

Yes Astronuc, and according to this gentleman it sustained up to 8 before leaking http://www.ustream.tv/recorded/13414000
Now, What I 'm not sure to have right is: is this value is for the core (primary) or the drywell

Note the significant bolting of the Drywell Cap and the fact it has a relief valve on it. There is the hydrogen release point, if indeed the pressure rose to 8 atm. Normally reliefs are set at 125-150 percent of design relief pressure. That is unless the 4 atm included a 150 percent safety factor.

 

[TCups]

https://www.physicsforums.com/attachment.php?attachmentid=33572&stc=1&d=1301164813

From above slide, and knowledge gained I revise what I posted earlier

Unit 1 - Explosion after venting - H2 leak in venting system
Unit 2 - Explosion at Torus - Torus has small leak, possibly a crack allowing H2 to vent.
Unit 3 - Explosion due to H2 leak at PVC-dome due to high pressure
Unit 4 - Explosion due to H2 generated in SFP
Core damage in all three working reactors.
And the water leak problem still to be found

Four units and four different failure modes leads to one conclusion:
BWR are not as safe as they are said to be. It is time to switch them off.


Conclusions already made by industry experts (see attached pdf file)
1. All existing power plants' passive emergency cooling systems (BWR's
RCIC and PWR's turbine-driven auxiliary feedwater system) should be inspected
and reinforced to assure their reliability during adverse condition. Onsite
emergency generators should be further protected.
2. PWR is more resilient than BWR because of its steam generator secondary
water inventory and size of containment. This gives larger margin to core damage
and containment failure. Further review is still necessary to improve the safety
level.
3. Spent fuel pool safety has been grossly overlooked. A hardened and
independent top spray system is necessary for all nuclear power plants.

Please read attached pdf file - the most authoritative analysis yet found.

Anton: At glance, I'd say you missed something on the Japanese slide. Look again, Grasshopper!

Unit 1 - Explosion after venting - H2 leak in venting system
Unit 2 - Explosion at Torus - Torus has small leak, possibly a crack allowing H2 to vent.
Unit 3 - Explosion due to H2 leak at PVC-dome due to high pressure AND H2 from SFP
Unit 4 - Explosion due to H2 generated in SFP


But more to read. Thanks.

 

[PietKuip]

http://news.yahoo.com/s/ap/as_japan_earthquake;_ylt=Ao6GXsSDQnvGdeAge5aI74Os0NUE;_ylu=X3oDMTNrMTVydHNzBGFzc2V0A2FwLzIwMTEwMzI2L2FzX2phcGFuX2VhcnRocXVha2UEY2NvZGUDbW9zdHBvcHVsYXIEY3BvcwMzBHBvcwMxMARwdANob21lX2Nva2UEc2VjA3luX3RvcF9zdG9yeQRzbGsDamFwYW5zZ292ZXJu" :

Defense Minister Yoshimi Kitazawa said late Friday that the U.S. government had made "an extremely urgent" request to switch to fresh water. He said the U.S. military was sending water to nearby Onahama Bay and that water injections could begin in the next few days.

The U.S. 7th Fleet confirmed that barges loaded with 500,000 gallons of fresh water supplies were on their way.

At least someone seems to be worried about the Cl-38.

 

[downwinder]

I have a mundane question. Is Plutonium more toxic or radioactive than Uranium? I thought it was, but a spokesman from the Nuclear Safety Agency specifically denied this. Other "experts" seem to contradict his statement.

Plutonium is far more hazardous than Uranium. Plutonium has a very high specific activity as compared to Uranium. It takes very little Plutonium to cause radiological damage from the alpha particles once inhaled. As I recall a lung burden of Plutonium is around 16 nanoCuries.
In the case of MOX fuel once the plutonium is encased in the fuel assembly and undergoes fission the resulting fission yield curves are close to the Uranium fission yields and the fission products become a higher hazard level than Plutonium. Again look at the specific activities.

 

[83729780]

Fukushima Nuclear Accident Update (26 March 2011, 15:15 UTC)

The IAEA has been informed by Japanese authorities that fresh water is now being used in place of sea water to cool the reactor pressure vessels at Units 1, 2 and 3 at the Fukushima nuclear power plant. The switch to fresh water is preferable as it leaves fewer deposits in components and is less corrosive than sea water.

http://www.iaea.org/newscenter/news/tsunamiupdate01.html

Will they now vent less steam in order to wash away as much salt as possible?

---

oh, a couple of people asked two pages back whether or not it was speculation that the pressure gauges in 2 and 3 were malfunctioning. This from IAEA yesterday:

Reactor pressure is decreasing at Unit 1 and so is seawater injection. On the other hand, pressure readings in the reactor pressure vessels remain unreliable in Unit 2 and have become unreliable in Unit 3

But see this from latest JAIF report:

Reactor 2:

Reactor pressure (26th 10:40)
(A) -0.014MPaG, (B) -0.016MPaG

CV pressure (26th 10:40)
0.115MPaabs
​

Reactor 3:

Reactor pressure (26th 10:00)
(A) 0.038MPaG, (B) -0.101MPaG

CV pressure (26th 10:00)
0.1066MPaabs​

http://www.jaif.or.jp/english/news_images/pdf/ENGNEWS01_1301137974P.pdf

(reactor pressure readings are gauge, not absolute)

So it appears the pressure gauges in 2 and 3 may be functional and the pressures therein are equal to atmospheric.

 

[Astronuc]

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

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.

 

[Joe Neubarth]

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.

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.

 

[jensjakob]

Btw - who produces the MOX used in #3? I read that it came from France?

 

[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.