Japan Earthquake: Nuclear Plants at Fukushima Daiichi

[Angry Citizen]

And I would further ask, "What exactly is the significance of those numbers?" Is that even a significant quantity of radiation?

 

[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]

The upper level of containment, the metal walls and roof, was destroyed. That structure is over the inner containment, which is reinforced concrete. I believe the reinforced containment had the pressure increase, which was vented. The venting would be through those stacks (towers) that one sees behind (to the west of) the units. Venting into the upper containment would not be the case as far as I know.

Well, it does seem to be where the explosion occurred though. I just found http://www.nei.org/filefolder/BoilingWaterReactorDesign.jpg" 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.

In theory though, it's life could have been extended another 20 years.

Yup, it'd require heavy investments though. A friend of mine was until recently involved in the upgrades in-progress at http://en.wikipedia.org/wiki/Oskarshamn_Nuclear_Power_Plant" , which is a BWR contemporary to Fukushima (although it's a different, ASEA design)

 

[promecheng]

It also houses the crane(s) to lift the containment cover and vessel components. I haven't seen pictures of the crane.

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).

 

[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]

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?

I think I read on TEPCO's, (Tokyo Electric Power Co.), website http://www.tepco.co.jp/en/press/corp-com/release/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]

What exactly is the source of those numbers? The link provides several pdfs.

I had used the http://www.nisa.meti.go.jp/english/files/en20110313-3.pdf" . 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.

Normal background btw is about 1-2 cps (60-120 cpm). Background comes from normal solar/cosmic radiation, and natural sources such as granite, and long-lived isotopes like K-40.

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]

And I would further ask, "What exactly is the significance of those numbers?" Is that even a significant quantity of radiation?

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]

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.

Is one referring 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/information-on-the-japanese-earthquake-and-reactors-in-that-region/

The have a general BWR Mk I diagram
http://i1107.photobucket.com/albums/h384/reactor1/BoilingWaterReactorDesign_3.jpg

 

[PietKuip]

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

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]

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

Sorry: microsievert per hour, according to http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=ja&tl=en&u=http%3A%2F%2Fmainichi.jp%2Fphoto%2Fnews%2F20110314k0000m040057000c.html".

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

 

[Astronuc]

Sorry: microsievert per hour, according to http://translate.google.com/translate?js=n&prev=_t&hl=en&ie=UTF-8&layout=2&eotf=1&sl=ja&tl=en&u=http%3A%2F%2Fmainichi.jp%2Fphoto%2Fnews%2F20110314k0000m040057000c.html".

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

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.

 

[marwood]

21 microsievrts per hour according to the linked reference ''Tohoku Electric Power said, Onagawa (I long to) from a nuclear power plant (town Onagawa, Miyagi Prefecture Ishinomaki) on-site radiation monitoring system, the reference value of the reporting obligations prescribed by a Nuclear Disaster Special Measures Law about four times the radiation dose (21 microsievert per hour) is detected.''

The alleged source being the Fukushima Daiichi plant located approx 120 kilometers to the south. Given 120 kilometers of diffusion, assumedly by some sort of Brownian motion type process, the Fukushima release must have been very substantial.

 

[turbo]

The alleged source being the Fukushima Daiichi plant located approx 120 kilometers to the south. Given 120 kilometers of diffusion, assumedly by some sort of Brownian motion type process, the Fukushima release must have been very substantial.

We can't assume that, though. Particulate and aerosol releases can be very directional with well-concentrated plumes.

 

[marwood]

NHK TV showing video of smoke rising from Fukushima Daichi No 3
http://www.kcet.org/disasterinjapan/

 

[Reno Deano]

Just how do you compare CPM and MicroSV? Answer: you don't without calibration standards. One is relative response to unknown source and the other is Dose. Sounds like technician talk!

 

[rogerl]

Guys. Supposed the fuel rods melted and become molten, do fission still occur in molten state or not anymore?

 

[PietKuip]

Guys. Supposed the fuel rods melted and become molten, do fission still occur in molten state or not anymore?

Immediately after the quake, the control rods were automatically inserted, and the fission chain reaction stopped. The heat production now is due to decay of the radioactive fission products, and is only about 10 % of the power when the reactor is on.

 

[rogerl]

Immediately after the quake, the control rods were automatically inserted, and the fission chain reaction stopped. The heat production now is due to decay of the radioactive fission products, and is only about 10 % of the power when the reactor is on.

I know. But supposed the controls rods were not inserted and the fuel rods melt and become molten and there is a tough cement underneath that prevent further falling underneath the plant. Would the uranium still fission when it's already in the molten state or would fission only occur when the uranium is solid?

 

[Borek]

For fission it doesn't matter whether the fuel is solid or melted.

 

[Astronuc]

I know. But supposed the controls rods were not inserted and the fuel rods melt and become molten and there is a tough cement underneath that prevent further falling underneath the plant. Would the uranium still fission when it's already in the molten state or would fission only occur when the uranium is solid?

The fission reaction would have eventually stopped but more slowly since the core configuration would have been disrupted. During operation of a BWR, some control rods are in the core for control of reactivity, i.e., to keep the core critical at steady state. The control rods are gradually withdraw during the cycle as the enriched uranium is depeleted (consumed) in a carefully devised sequence such that the core is always just near critical, otherwise the power is slowing increasing or decreasing depending on the need for power increase or decrease. Toward end of cycle, when much of the fissile material has been used, the control rods are all out (all rods out, ARO). The reactor can continue for some days afterward, and then it is shutdown for refueling and maintenance.

If the fuel melted it would displace the water and reduce the moderation, which would make the core slightly subcritical at some point in time, and the fission reaction would decrease.

However, we know that the control rods did insert in the Fukushima reactors, and the fission reactions ceased. The problem is that fission products continue to decay after the fission reaction is stopped, and that heat must be removed from the core/fuel following shutdown. The heat removal did occur for sometime after shutdown, first using power from emergency diesel generators, and then on batteries. However, at some point the cooling capacity was reduced or lost and some part of the core overheated.

Subsequently, Units 1 and 3 were flooded with seawater to maintain the cooling of the reactors.

From the continuity of matter property, what goes into a system, must come out elsewhere if mass in the system is constant. So, if some seawater goes in, it must come out somewhere as water or steam. It is the steam that is occasionally vented to keep the pressure down. However, this means that the system is no longer closed to the environment, and some fission products, mostly gases Xe and Kr, and perhaps some volatiles, e.g., I, will escape to the atmosphere.

The objective now is to cool the reactor core and minimize the release of radioactive substances to the environment.

 

[LanceV]

Subsequently, Units 1 and 3 were flooded with seawater to maintain the cooling of the reactors.

I still haven't found out what exactly they flooded with sea water.
Do they just replace lost water in the RPV by sea water? Or are they trying to cool the RPV from the outside by flooding the containment? Or both?
The use of boron suggests the former but I keep hearing about the latter.

Does anybody know more?

 

[nlsherrill]

The fission reaction would have eventually stopped but more slowly since the core configuration would have been disrupted. During operation of a BWR, some control rods are in the core for control of reactivity, i.e., to keep the core critical at steady state. The control rods are gradually withdraw during the cycle as the enriched uranium is depeleted (consumed) in a carefully devised sequence such that the core is always just near critical, otherwise the power is slowing increasing or decreasing depending on the need for power increase or decrease. Toward end of cycle, when much of the fissile material has been used, the control rods are all out (all rods out, ARO). The reactor can continue for some days afterward, and then it is shutdown for refueling and maintenance.

If the fuel melted it would displace the water and reduce the moderation, which would make the core slightly subcritical at some point in time, and the fission reaction would decrease.

However, we know that the control rods did insert in the Fukushima reactors, and the fission reactions ceased. The problem is that fission products continue to decay after the fission reaction is stopped, and that heat must be removed from the core/fuel following shutdown. The heat removal did occur for sometime after shutdown, first using power from emergency diesel generators, and then on batteries. However, at some point the cooling capacity was reduced or lost and some part of the core overheated.

Subsequently, Units 1 and 3 were flooded with seawater to maintain the cooling of the reactors.

From the continuity of matter property, what goes into a system, must come out elsewhere if mass in the system is constant. So, if some seawater goes in, it must come out somewhere as water or steam. It is the steam that is occasionally vented to keep the pressure down. However, this means that the system is no longer closed to the environment, and some fission products, mostly gases Xe and Kr, and perhaps some volatiles, e.g., I, will escape to the atmosphere.

The objective now is to cool the reactor core and minimize the release of radioactive substances to the environment.

So, when the news reports that there is a danger of radiation exposure...what exactly is being exposed? I think I know the very basics of the core, which is essentially uranium fuel rods that are bombarded by free neutrons right? Where does Xe, Kr, and I come from? Are these what uranium decays too? When people get radiation sickness/exposure, what is harming them? electromagnetic radiation or something else?

Clearly I have no clue what I'm talking about, but I would like too.

 

[Reno Deano]

Hypothetical People external to the plant and workers (real) near or within the plant would be the things being exposed to radiation. Eventhough the melted fuel losses its favorable geometry for substained criticality, some neutrons and high energy gammas will continue to prolong the fission process, but at a significantly lower pace and would be considered subcritical. The attached link discusses the fission fragment spectrum of radioisotopes.

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fisfrag.html

 

[Astronuc]

So, when the news reports that there is a danger of radiation exposure...what exactly is being exposed? I think I know the very basics of the core, which is essentially uranium fuel rods that are bombarded by free neutrons right? Where does Xe, Kr, and I come from? Are these what uranium decays too? When people get radiation sickness/exposure, what is harming them? electromagnetic radiation or something else?

Clearly I have no clue what I'm talking about, but I would like too.

Steam from the primary system would carry Xe and Kr (noble) gases, and perhaps some I and Br which are volatiles. It is expected that I and Br would form oxides, and react chemically to form iodates and bromates, if not iodides and bromides.

Xe, Kr, I, Br are fission products produced when U-236 (U235+n) fissions. There are other fission products such as Cs, Ba, La, . . . . and Rb, Sr, Y, . . . which are essentially in solid form, and the unused U, Pu, . . . which is in the fuel. Normally these are surrounded by a metal alloy of Zr, but that alloy has probably corroded/oxidized, and no longer performs its function, which is the keep the fuel (UO2 and fission products) separated from the coolant.

The fuel and fission products can oxidize into particles on the order of several microns, and this can be then dispersed in the coolant.

The noble gases can readily escape into the steam, and it is hoped that much of the fuel will remain intact.

There are also core components, e.g. control rods, and other structures that are made of stainless steel, typically SS304. The control rods contain boron carbide (B4C) and perhaps Hf, which are neutron absorbers used to control/limit the fission reaction or shutdown the reactor. If the temperatures in the core got to ~1300-1400 C, then the control rods could have melted. Above 1000 C, they could have gotten soft and deformed.

When people are exposed to radiation, it is usually beta and gamma radiation, or possibly alpha particles if isotopes of heavy elements, e.g., Rn, Ra, U or tranuranics were ingested or inhaled. Alpha particles are stopped by clothing or skin. Beta particles are more penetrating, and gamma photons are the most penetrating.

Ionizing radiation harms cells by radiolysis of the water (which forms peroxide and hydrogen), which can then chemically react with the complex molecules like DNA, RNA, proteins, vitamins, enzymes, coenzymes, . . . . which are necessary for cells to function.

A little radiation is not necessarily bad. Cells can be repared, or dead cells are simply discarded and replaced. The more radiation, the more cellular necrosis, the more one can become seriously ill. Some damaged cells may mutate into cancers. Nerve cells are particularly sensitive to radiation, and they are not so easily replaced.

 

[TCups]

For fission it doesn't matter whether the fuel is solid or melted.

Borek: I think the question is (at least mine is. . . ) this: if the core melts and becomes a molten mixture of fissile materials + melted control rods, even if the reactor's fuel has been "killed" with sea water and boron, is it still possible that the molten mixture might become "critical"?

And even if not, how long will the ongoing heat of decay (at 10% of the level of an operational reactor mentioned) persist in the absence of cooling water?

Finally, are either the primary steel containment vessel or the reinforced concrete secondary containment, or both up to the task of containment of a core meltdown and if so, for how long?

 

[Astronuc]

I still haven't found out what exactly they flooded with sea water.
Do they just replace lost water in the RPV by sea water? Or are they trying to cool the RPV from the outside by flooding the containment? Or both?
The use of boron suggests the former but I keep hearing about the latter.

Does anybody know more?

As far as I know, they were trying to inject seawater into the pressure vessel, ostensibly through the piping system used by the ECCS. Flooding containment is also a possibility, but that's mostly outside of the RPV which contains the core, and which is where the cooling water must go.

The steam is venting somehow, through pressure relief valves, and then the personnel have to vent the containment. So the seawater goes in, and some steam comes out, and there has to be a mass balance.

How they are cooling the seawater once it's heated is not clear.

If they pump seawater into the RPV/primary system, and it is flowing out into containment, that could mean an open valve or pipe break. HOWEVER, there is no information about the integrity of the RPV or piping within containment. We can only wait for further information from the site.

 

[misnderstudge]

well as a civil defence member (non physicist member) i don't think the risk is high at all, but in its history now is the closest to a risk there has been as far as i am aware. they will properly have to cold start it (i think no facts to back that up) which is very expensive and take months. i am surprised World Agency of Planetary Monitoring and Earthquake Risk Reduction,(WAPMERR) has said nothing at all. oh and the chance even if it was to go of a thermal explosion is so small it is practically 0

 

[LanceV]

Flooding containment is also a possibility, but that's mostly outside of the RPV which contains the core, and which is where the cooling water must go.

Yes, but the question is can they inject water into the core? Maybe the pressure is to high. Or there is a danger of explosion when water hits the hot fuel rods.

The steam is venting somehow, through pressure relief valves, and then the personnel have to vent the containment. So the seawater goes in, and some steam comes out, and there has to be a mass balance.

At first I was under the impression that the sea water is circulated through the reactor. Maybe by extracting it via the suppression pool and then back into the sea. If the core is not molten this would probably result in only a minor pollution.

But it is hard to find any definite information. It seems that there is nobody twittering from the control room. Maybe they are busy atm.

 

[misnderstudge]

if it was they would circle the rods not by direct contact but by going around it as such, and when it cools down then flood it or there would be a large cloud were they stand. slow cool then rapid cool can't remember the real name for it but i think you may understand

 

[DrDu]

I just noticed that in Ibaraki which is maybe 50 km south of Fukushima, ambient dose rates are rising (to about 180 nGy/h) for the first time since the earthquake. Apparently, the wind is turning.

See:
http://www.bousai.ne.jp/eng/

For Fukushima itself, values are still not available on that site.

 

[Astronuc]

if it was they would circle the rods not by direct contact but by going around it as such, and when it cools down then flood it or there would be a large cloud were they stand. slow cool then rapid cool can't remember the real name for it but i think you may understand

Maybe one is thinking of reflood or quenching (rapid cooling).

The details for each unit are different and unknown.

Apparently Units 1 and 3 lost EDGs and/or electrical buses between EDGs and ECCS due to tsunami. The tsunami did take out some of the fuel systems for the EDGs, but also may have damaged the electrical equipment.

As far as I know, they are pumping water through the piping in order to cool the core, and/or they are flooding the primary containment.

We lack the details, so we don't know what systems are available.


Apparently the US 7th Fleet has detected radiation at sea and are moving out of the area.

Any sustained activity offsite is a bit worrisome because it means radioactivity is getting of site in significant (not quantified) amounts.

Onagawa 'emergency'

A technical emergency was declared at 12.50pm today at the Onagawa nuclear power plant after radiation levels in the plant site reached 21 microSieverts per hour. At this level plant, owner Tohoku Electric Power Company is legally obligated to inform government of the fact. Within just ten minutes, however, the level had dropped to 10 microSieverts per hour.

. . . .

The increase in radioactivity at Onagawa has been attributed to releases from Fukushima.

Potential contamination of the public is being studied by Japanese authorities as over 170,000 residents are evacuated from within 20 kilometres of Fukushima Daini and Daiichi nuclear power plants. Nine people's results have shown some degree of contamination.

Japan's Nuclear and Industrial Safety Agency (Nisa) – part of the Ministry of Economy, Trade and Industry (Meti) – said that out of about 100 residents evacuated from Futaba by buses, nine people were found to have been exposed. The pathway of their exposure is currently under investigation.

One person was measured to have an exposure of 18,000 counts per minute (cpm); another had a measurement of between 30,000 and 36,000 cpm; while a third evacuee had an exposure of 40,000 cpm. A fourth person initially gave a reading of over 100,000 cpm, but a second measurement taken after the person had removed their shoes was just under 40,000 cpm. Another five people were said to have "very small counts".Radiation levels have been monitored across the Fukushima Daiichi and Daini sites. As of 10.00pm today, Tepco said that radiation levels were lower and stable. The maximum level detected on the 12 March was at 3.29pm when levels reached 1015 microsieverts per hour.

On-site casualties

At Fukushima Daiini unit 3 one worker received a radiation dose of 106 mSv. This is a notable dose, but comparable to levels deemed acceptable in emergency situations by some national nuclear safety regulators.
. . . .

Source: http://www.world-nuclear-news.org/RS-Contamination_found_on_evacuated_residents-1303114.html

Some colleagues indicated that World Nuclear News is one of the best sites for information on the ongoing situation.

 

[Reno Deano]

"A little radiation is not necessarily bad. Cells can be repared, or dead cells are simply discarded and replaced. The more radiation, the more cellular necrosis, the more one can become seriously ill. Some damaged cells may mutate into cancers. Nerve cells are particularly sensitive to radiation, and they are not so easily replaced."

Considering human evolution occurred during higher levels of terrestrial radiation in the far past, More than a little radiation exposure is not that concerning, except for the weak. I and many of my fellows Nukes have life-time whole body doses exceeding 40 Rem, and are relatively healthy at our retirement ages.

 

[Reno Deano]

Japanese asking for help: http://www.nrc.gov/reading-rm/doc-collections/news/2011/11-047.pdf"

 

[Reno Deano]

Old news, but insight to US Actions at West Coast Nuclear Pwr Plants (all PWRs):

http://pbadupws.nrc.gov/docs/ML1107/ML110700503.pdf"

 

[Astronuc]

"A little radiation is not necessarily bad. Cells can be repared, or dead cells are simply discarded and replaced. The more radiation, the more cellular necrosis, the more one can become seriously ill. Some damaged cells may mutate into cancers. Nerve cells are particularly sensitive to radiation, and they are not so easily replaced."

Considering human evolution occurred during higher levels of terrestrial radiation in the far past, More than a little radiation exposure is not that concerning, except for the weak. I and many of my fellows Nukes have life-time whole body doses exceeding 40 Rem, and are relatively healthy at our retirement ages.

I have also been exposed to radiation well beyond what the average person in the general population would receive, and I'm fine.

On the other hand, I've had one colleague develop thyroid problems, possibly related to exposure.

Still, the industry doesn't need to be unnecessarily exposing the general population (especially pregnant women, babies and children) to radiation - as is currently the case.

 

[Reno Deano]

Apparently the US 7th Fleet has detected radiation at sea and are moving out of the area.

Knowing the Navy they flew through the downwind radionuclide concentrations and brought it back aboard the ship. Some of the highest contamination found external of the reactor compartments on an aircraft carrier is the fresh air intake filters for the ship. When planes lands they shake off accumulated contamination (Cs-137 and other radionuclide's) from their high altitude flights, which is quickly sucked into the fresh air plenums outboard of the flight deck.

 

[marwood]

''When planes lands they shake off accumulated contamination (Cs-137 and other radionuclide's) from their high altitude flights ..."

Is the contamination distribution denser at high altitudes (and up into the jet stream) or do the planes come back with greater contamination because of their path length through the contaminated air being longer?

 

[intric8]

Latest reports of Japan officials bowing in unison to express their remorse and other discouraging comments about the status of all three reactors have me feeling like its game over.

No water>no coolant>2200F+ temperatures>?

Is it inevitable at this point?

 

[Reno Deano]

Is the contamination distribution denser at high altitudes (and up into the jet stream) or do the planes come back with greater contamination because of their path length through the contaminated air being longer?

Its the path length and time immersed. There is long lived 1950's & 1960's weapons testing contamination circulating around up there.

 

[jarvik]

Its the path length and time immersed. There is long lived 1950's & 1960's weapons testing contamination circulating around up there.

I don't think the fission products of the 50s and 60s tests contribute any relevant amount of contamination to these flights. My impression is that the fallout from the atmospheric tests (and other inputs) rain out to the earth’s surface largely within a year or so of their input. Events such as large forest fires can return small but measurable amounts of this 60s fallout back into the atmosphere.

However, I would bet that the current contamination of US aircraft spoken of is >99% sourced to current reactor issues in Japan and not appreciably due to 50s/60s era sources.

 

[turbo]

Is one referring 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.

I have been looking for info on the risks of a dry spent fuel pool. Unfortunately, there is little middle-of-the road info out there. Lots of the worst-case scenarios, though many of them have the fingerprints of Fairewinds Associates on them. Phrases like "Chernobyl on steroids" etc. The NRC materials I found were comforting about the level of safety required, but very light on the risks.

This software simulator site quiz says that the severity of an SFP failure would be on a par with a "worst case power accident".
http://www.microsimtech.com/sfpquiz/default.htm

Can you help clarify, Astro?

 

[gmax137]

I think the worst case scenario for a 'dry spent fuel pool' is overheating to the point where the zirc cladding oxidizes rapidly (in other words, it burns). If you are old enough, you may remember seeing a zirconium fire - the old flashbulbs (think reporters with big crown graphic 4x5 cameras) used zirconium wire. The good news is that, as long as the pool is intact, all you need to do to prevent the 'dry' part of the scenario is add water to make up for any boiloff.

 

[rogerl]

In a nuclear reactor, there are as many as a thousand fuel rods. But there only appears to be a dozen or so control rods which are put amongst the thousands of fuel rods. How does this stop nuclear reaction within each rod? Or in a nuclear reactor. Do neutrons from different fuel rods hit other fuel rods at a distance and the control boron rods are supposed to block or absorb them? But how can the few control rods absorb the neutrons from thousands of fuel rods?