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Fukushima I: four reactors in trouble.

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I am not underestimating anything.

 

The issue here is of answering the question of what happens if the reactor goes critical and in particular when the control rods are fully inserted which would normally be a shut down state where if the fuel is old the reactor already produces shit loads of power.

 

It is not obvious to me how a boiling water reactor will burn like the chernobyl reactor which had tonnes of graphite inside it which caught fire and burnt.

 

I dont understand what problem you are having here.

 

Reactors have variable power.

 

They might have 1 shit load at low power and 10 shit loads at full power.

 

However since these are boiling water reactors where absense of water moderates the reactor towards lower power maybe you get half a shit load if it goes critical where even in a shut down state with water there is an enormous amount of shit being produced by these stinking reactors.

 

But come on please. Lets be sensible and nut it out so we can agree.

 

I think there we are misunderstanding one-another here. From what the report said, the fuel that was removed from reactor 4 was in the storage tank (ie no control rods!). But, the water level in the storage tank was falling, hence increased heat. Then they (the company that operates the reactors) said that there was a risk that this fuel could go critical.

 

While I believe this may just be a "true scientist" commenting (hence he cannot say it is impossible as there is a tiny tiny chance) the consequences would be very bad. That's all I was saying.

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As far as I remember, this is the optimum operating condition.

 

You need to work thru the following thought experiment

 

Build the pile of blocks of U until it gets warm.

 

Add another block to make it warmer - these are only small blocks so you wont suddenly find yourself cooking.

 

Now get a rod of boron and insert it a gap in the pile and observe how the temperature is proportional to the amount the boron sticks into the gap.

 

This pile is not simply on or off but can be regulated with the boron.

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Reactors have variable power.

 

They might have 1 shit load at low power and 10 shit loads at full power.

No, that's not how they work. I see now the misunderstanding. It's more like a resonant effect. Ie s**t loads (at critical) or tiny loads (at sub critical). That's why they are used for base load, they cannot be turned up and down just like that.

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I think there we are misunderstanding one-another here. From what the report said, the fuel that was removed from reactor 4 was in the storage tank (ie no control rods!). But, the water level in the storage tank was falling, hence increased heat. Then they (the company that operates the reactors) said that there was a risk that this fuel could go critical.

 

While I believe this may just be a "true scientist" commenting (hence he cannot say it is impossible as there is a tiny tiny chance) the consequences would be very bad. That's all I was saying.

 

I made my comment about the reactor being critical when a comment was made about re-criticality of the reactor?

 

I said it did not mean anything more than fission was occuring. The question was then how much fission.

 

If the used fuel in the cooling pond (storage tank) goes critical it does not mean anything other than fission has begun for that configuration where it could be a lower power event in that configuration where the problem is already one of lack of cooling.

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I made my comment about the reactor being critical when a comment was made about re-criticality of the reactor?

 

I said it did not mean anything more than fission was occuring. The question was then how much fission.

 

If the used fuel in the cooling pond (storage tank) goes critical it does not mean anything other than fission has begun for that configuration where it could be a lower power event in that configuration where the problem is already one of lack of cooling.

Hi AAK, Please see previous post. At criticality, it can run away without control. When sub critical it eventually dies out (less and less atoms split each cycle, so it stops). They cannot be turned up and down like a gas fire.

 

Right NCIS has started, gotta go.

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French & others highly critical of Japanese Government:

http://www.dailymail.co.uk/news/article-1366670/Japan-earthquake-tsunami-French-claim-scale-nuclear-disaster-hidden.html

 

Get out of Tokyo: Foreign Office tells all Britons to leave toxic radiation zone as Japanese 'lose control' of stricken reactor

 

By David Derbyshire

Last updated at 8:17 PM on 16th March 2011

 

* U.S nuclear chief: 'There is nothing preventing meltdown'

* French minister: 'Let's not beat about the bush, they've essentially lost control'

* Radioactive steam spews into atmosphere from reactor number three

* Experts warn that crisis is 'approaching point of no return' as officials run out of options

* Officials commandeer police water cannon to spray complex

* Attempts to dump water on reactors by helicopter fail

* Two more previously stable reactors begin to heat up

* Rich scramble to book private jets out the country as fleeing passengers pack Tokyo airport

* Workers battling nuclear meltdown evacuated for hours today after radiation levels increased

 

The UK government is urging all British nationals to leave Tokyo as soon as possible amid fresh safety fears.

 

The Foreign Office this evening issued a statement recommending that all Britons leave the area for their own safety. At least 17,000 UK citizens live in Japan, the vast majority of them in Tokyo.

 

The plea came as the crisis at the Fukushima nuclear plant in northeast Japan worsened with the chief of the U.S. Nuclear Regulatory Commission (NRC) warning tonight that all the cooling water has gone from one of the spent fuel pools. That means there is nothing to stop the fuel rods getting hotter and ultimately melting down.

 

Read more: http://www.dailymail.co.uk/news/article-1366670/Japan-earthquake-tsunami-French-claim-scale-nuclear-disaster-hidden.html#ixzz1GnakCjOE

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No, that's not how they work. I see now the misunderstanding. It's more like a resonant effect. Ie s**t loads (at critical) or tiny loads (at sub critical). That's why they are used for base load, they cannot be turned up and down just like that.

 

They are used for base load because they are supposedly the cheapest power and they cost so much to make that you have to run them like airlines to justify the cost, where gas turbines which can be throttled up in a few minutes dont have the same temperature stress peculiarities as for example fuel can fractures due to temperature differences.

 

Read up on Chernobyl to see them attempting to get into a low power configuration to run a test where supposedly they wanted to show what would happen if the main grid failed for water pump operation where they did not want to try it at full power. They went to low power too quickly and then xenon gas in the fuel cans moderated the reactor more than they had planned for so they pulled out the control rods further and the reactor was in a very dangerous unstable configuration.

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NRC: No Water In Spent Fuel Pool Of Japan Plant

 

WASHINGTON March 16, 2011, 03:57 pm ET

 

The chief of the U.S. Nuclear Regulatory Commission said Wednesday that all the water is gone from one of the spent fuel pools at Japan's most troubled nuclear plant, but Japanese officials denied it.

 

If NRC Chairman Gregory Jaczko is correct, this would mean there's nothing to stop the fuel rods from getting hotter and ultimately melting down. The outer shell of the rods could also ignite with enough force to propel the radioactive fuel inside over a wide area.

 

Jaczko did not say Wednesday how the information was obtained, but the NRC and U.S. Department of Energy both have experts on site at the Fukushima Dai-ichi complex of six reactors. He said the spent fuel pool of the complex's Unit 4 reactor has lost water.

 

Jaczko said officials believe radiation levels are extremely high, and that could affect workers' ability to stop temperatures from escalating.

 

Japan's nuclear safety agency and Tokyo Electric Power Co., which operates the complex, deny water is gone from the pool. Utility spokesman Hajime Motojuku said the "condition is stable" at Unit 4.

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Hi AAK, Please see previous post. At criticality, it can run away without control. When sub critical it eventually dies out (less and less atoms split each cycle, so it stops). They cannot be turned up and down like a gas fire.

 

Unlike my moderatable pile of blocks and hand held boron rod a reactor costs a few hundred million.

 

The key to successful design is to ensure they can be operated in a variety of configurations and still be stable. In a boiling water reactor more boiling causes automatic moderation and less boiling where less boiling causes more power. The nature of the boiler is that there is a random amount of boiling occuring near a randomly decaying fuel supply. The design moderates a complexly changing process automatically.

 

But as the fuel ages for example the control rods are pulled out near those aging fuel rods and left further in where the new fuel has been placed.

 

Please consult your colleague. I am sure he can help resolve this.

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'Condition is stable' just means the water is almost gone and the rods are very hot, many of the fuel cans have burst but it is not getting any hotter and no worse than the highly radioactive stable situation they have now.

 

The Japanese are telling us everything we need to know.

 

For example NHK said earlier that the police have decided to pour water on the reactor using some kind of firehose. The fact the police made that decision shows how bad things are.

 

When they early said they were using helicopters to spray water onto the fuel rod pond you knew the rods were no longer contained and it was so facking radioactive there that nobody could go up there with a hose and place it in the pond. Confirmed when they told you that flights were stopped as the radioactivity was massively high. Then along came the police with their fire hose

 

And they released the pictures showing the place blown to hell where access thru the debris would be more or less impossible and control systems and pipes were totally wrecked.

 

The emperor said he was very worried and asked people to pray........

 

Even so at the moment it is a smokey mess and that is maybe all it is for some considerable time yet and it is a huge World with billions and billions of tons of air compared to the tiny number of tonnes of fuel.

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Unlike my moderatable pile of blocks and hand held boron rod a reactor costs a few hundred million.

 

The key to successful design is to ensure they can be operated in a variety of configurations and still be stable. In a boiling water reactor more boiling causes automatic moderation and less boiling where less boiling causes more power. The nature of the boiler is that there is a random amount of boiling occuring near a randomly decaying fuel supply. The design moderates a complexly changing process automatically.

 

But as the fuel ages for example the control rods are pulled out near those aging fuel rods and left further in where the new fuel has been placed.

 

Please consult your colleague. I am sure he can help resolve this.

 

No need, it's resolved. I'm sorry but the point you seem to be missing is that they cannot be turned up and down like a gas or coal power station. That is why they are used for base load. They are not cheaper than others either.

 

You are also confusing random with variable (and predictable). As the fuel runs out, the control rods can be withdrawn more. However, they are still running at the critical point, as designed.

 

Right, off to bed.

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As for things melting or mixing, in relation to criticality, these two stories shed some light on it (how easily it can happen by just mixing the wrong things, e.g. if something melts):

 

http://en.wikipedia.org/wiki/Cecil_Kelley_criticality_accident

The accident involved plutonium compounds dissolved in liquid chemical reagents, and it caused the death of one man – Cecil Kelley, a chemical operator – from severe radiation poisoning within 35 hours.

 

http://listverse.com/2010/03/25/10-famous-incidences-of-death-by-radiation/

Japan’s worst nuclear radiation accident took place at a uranium reprocessing facility in Tokaimura, northeast of Tokyo, on September 30, 1999. The direct cause of the criticality accident was workers putting uranyl nitrate solution containing about 16.6 kg of uranium, exceeding the critical mass, into a precipitation tank. The tank was not designed to dissolve this type of solution and was not configured to prevent eventual criticality.

 

Three workers were exposed to lethal radiation doses.

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No need, it's resolved. I'm sorry but the point you seem to be missing is that they cannot be turned up and down like a gas or coal power station. That is why they are used for base load. They are not cheaper than others either.

 

You are also confusing random with variable (and predictable). As the fuel runs out, the control rods can be withdrawn more. However, they are still running at the critical point, as designed.

 

Right, off to bed.

 

In a boiling water reactor the standard way of controlling the power produced by fission so the reactor power follows the required load is to alter the flow of water which is one of the moderators.

 

http://www.free-ed.net/sweethaven/MiscTech/Nuclear/Lesson0403.pdf

 

A positive reactivity addition also occurs when

flow is increased in a two-phase (steam-water) cooled system. Increasing the flow rate decreases

the fraction of steam voids in the coolant and results in a positive reactivity addition. This

property of the moderator in a two-phase system is used extensively in commercial BWRs.

Normal power variations required to follow load changes on BWRs are achieved by varying the

coolant/moderator flow rate.

 

But when i said this i was a bit muddled up:

 

In the case of the undamaged Japanese reactors the control rods are inserted where if they are slightly removed the reactor goes critical for that configuration which means it operates at low power.

 

But when you said the following you were not allowing for the fact that the control rods and the water are both moderators where as i mentioned before there are two phase considerations related to reactor power which is altered by flow.

 

 

What? The design of the reactor will have a critical configuration dependent upon the amount of fuel and the configuration of the fuel rods. The flow of the water is irrelevant re criticality, it is taking the heat away. Also, as I have already said, the control rods "control" the reaction.

 

I was also wrong about my block of U experiment. As you said it would also be warm when sub critical and would be dangerously unstable at the critical point

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In a boiling water reactor the standard way of controlling the power produced by fission so the reactor power follows the required load is to alter the flow of the moderator which is water.

 

http://www.free-ed.net/sweethaven/MiscTech/Nuclear/Lesson0403.pdf

 

A positive reactivity addition also occurs when

flow is increased in a two-phase (steam-water) cooled system. Increasing the flow rate decreases

the fraction of steam voids in the coolant and results in a positive reactivity addition. This

property of the moderator in a two-phase system is used extensively in commercial BWRs.

Normal power variations required to follow load changes on BWRs are achieved by varying the

coolant/moderator flow rate.

Couldn't sleep.

 

That seems reasonable. (For a BWR) Not economical though.

 

So, point is it looks grim. What is the weather forecast for the area?

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But when you said the following you were not allowing for the fact that the control rods and the water are both moderators where as i mentioned before there are two phase considerations related to reactor temperature which is altered by flow.

OK, but the control rods are not moderators (possibly why we have been misunderstanding one another, or maybe because I'm tierd :rolleyes: ). The control rods mop up excess neutrons, whereas the moderator thermalises them (slows them) to enable the U235 to capture them. However, yes they will both affect the reaction rates in a BWR (but not in a PWR).

 

 

Just watching the news now. Increasingly looks like the weather will blow winds south to Tokyo. Any release of large amounts of radiation now could have alarming effects (ie if people panic and all try to leave Tokyo (As I probably would if I were there).

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I work in the nuke industry and I knew from the moment I heard about the problem that this was going to be MAJOR.

 

As far as I can see there is little option other than to flood the place with sea water.

 

I suspect that the radiation spikes were criticality events from damaged / melted fuel. Take the 11mSv dose at the gate and then work out the distance to the closest reactor and then apply inverse square law... The reaction was very significant. The spikes are consistent with solid criticality events. The solid criticalities usually disperse the material so it doesn't immediately go critical again (unless it forms the correct geometry).

 

Personally I think that spraying with water without massive volumes and flows is like dripping water onto a kettle element which will create more radioactive vapour and possibly hydrogen. Again they need to work out the cooling flows to bring the temperatures in the reactor down. They will know the heat generation from the rods. So they can work out the water volumes required to bring the temperatures down.

 

They need to get new electrical supplies to the site, new sea water pumps and purge the plants with sea water and get some neutron absorbers in there somehow. I really feel sorry for the guys doing the work, the earthquake and tsunami must have tied both hands behind the back.

 

I fear this idea of a police spraying water could end badly as it might cause more criticality events. I guess it shows how desperate they are...

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OK, but the control rods are not moderators (possibly why we have been misunderstanding one another, or maybe because I'm tierd :rolleyes: ). The control rods mop up excess neutrons, whereas the moderator thermalises them (slows them) to enable the U235 to capture them. However, yes they will both affect the reaction rates in a BWR (but not in a PWR).

 

 

Just watching the news now. Increasingly looks like the weather will blow winds south to Tokyo. Any release of large amounts of radiation now could have alarming effects (ie if people panic and all try to leave Tokyo (As I probably would if I were there).

 

Thanks for helping me to understand this stuff better. 02:43 here so i will be fading away soon.

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Thanks for helping me to understand this stuff better. 02:43 here so i will be fading away soon.

Thank you too, a good bit of revision and I have learnt a good bit more about BWR's (I previously studied other types i.e. PWR Pebble bed, fast breeder etc).

 

Time to try and sleep again.

 

But can't help thinking about the guys at the plant, they are some seriously brave soles. They are operating in levels way above "safe" now.

 

I fear this idea of a police spraying water could end badly as it might cause more criticality events. I guess it shows how desperate they are...

 

Yes, desperate indeed.

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Thank you too, a good bit of revision and I have learnt a good bit more about BWR's (I previously studied other types i.e. PWR Pebble bed, fast breeder etc).

 

Time to try and sleep again.

 

But can't help thinking about the guys at the plant, they are some seriously brave soles. They are operating in levels way above "safe" now.

 

 

 

Yes, desperate indeed.

 

Strangely the news is that TEPCO are planning on connecting to the available grid but are meanwhile setting up a power plant so they can run the pumps outside the reactors

 

Why with the resources of all of Japan at their disposal are they planning on connecting to the existing grid? It is now about 5 days since the Prime minister announced a disaster was in progress and that all means of getting all avaliable forms of generator power was underway to run the cooling pumps - presumably they thought about hooking up to the local grid?

 

And even stranger why have they not got tugs with powerful hoses pouring huge amounts of water on the reactors from the sea with the crew protected in air tight boxes and shields?

 

There was a guy on TV just now saying their second priority is to get power and first is to pump water. ??

 

http://www3.nhk.or.jp/nhkworld/r/movie/index.html

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It is not obvious to me how a boiling water reactor will burn like the chernobyl reactor which had tonnes of graphite inside it which caught fire and burnt.

 

 

 

Class D Metal fire.

http://en.wikipedia.org/wiki/Fire_classes

Certain metals are flammable or combustible. Fires involving such are designated "Class D" in both systems. Examples of such metals include sodium, titanium, magnesium, potassium, uranium, lithium, plutonium, and calcium. Magnesium and titanium fires are common. When one of these combustible metals ignites, it can easily and rapidly spread to surrounding ordinary combustible materials.

...

Metal fires represent a unique hazard because people are often not aware of the characteristics of these fires and are not properly prepared to fight them.

 

Of course it can burn. It is not generlly recommended to fight a class D fire with water. However, they need cooling so let's hope the rods dont start to actually burn due to lack of cooling. Melting is far from burning.

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And it gets worse...again! *sigh*

 

An article from the Natural News quotes an email they recieved from someone known to them:

“…nuclear reactors use bundles of enriched uranium packed into stainless steel fuel rods in order to generate the heat that drives the turbines. You need to keep these bundles of pins cool otherwise they melt or burst.

 

Now, it seems the Fukushima power plant pulled spent fuel bundles (a collection of fuel rods) and stored them on site rather than shipping them to another location. Speculation is that in addition to the fires that are damaging the working reactor, these storage areas of their spent fuel bundles could [now] be on fire. This vastly compounds the problem of any meltdown, as this spent fuel will add to the contamination [because] it is extremely toxic.

 

In other words, as well as dealing with a potential meltdown, you also have the toxic products from the depleted fuel pins adding to the pollution. This is extraordinarily bad. The spent fuel bundles should have been relocated away from the reactor core a long, long time ago. Given the earthquake realities of Japan, these reactor building were basically dirty bombs waiting to be set off by a [natural] disaster.”

 

I want to thank this individual for his continued reporting from Tokyo and assure him that if he chooses to send more information to NaturalNews, we will of course continue to protect his anonymity.

 

Nuclear plant becomes dirty bomb waiting to go off

 

The upshot of his assessment of the situation is that the Fukushima power plant is now a “dirty bomb” waiting to happen. And it’s on fire right now. Radiation levels are rising so rapidly that it’s not even safe to work near the plant. This is very rapidly headed into a situation where suicidal volunteers are going to have to “rush in” and do some work on the plant, spend only a few minutes there, then evacuate as quickly as possible. And they’ll still get cancer.

 

This is exactly what happened in Chernobyl following the accident there in 1987. Hundreds of brave volunteers basically committed suicide in order to erect the containment vessel over the melted-down reactor and thereby prevent further radiation from escaping directly into the environment.

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Class D Metal fire.

http://en.wikipedia.org/wiki/Fire_classes

 

 

Of course it can burn. It is not generlly recommended to fight a class D fire with water. However, they need cooling so let's hope the rods dont start to actually burn due to lack of cooling. Melting is far from burning.

 

The fuel is uranium oxide? It is already oxidised. The fuel can is made of Zircaloy which will burn if powdered but passifies otherwise - i am not sure it will burn when solid metal with the oxide coating. The other contents of the decayed fuel i am not sure about. Much of it will vaporise but will it significantly burn?

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The fuel is uranium oxide? It is already oxidised. The fuel can is made of Zircaloy which will burn if powdered but passifies otherwise - i am not sure it will burn when solid metal with the oxide coating. The other contents of the decayed fuel i am not sure about. Much of it will vaporise but will it significantly burn?

Yes, good point - the oxide will not burn. I guess it depends on the composition of the rods. #3 had Mixed oxide fuel, right? - are there other metals in there? Let's hope you are right. They must have thought of this.

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They must have thought of this.

 

Not necessarly. All the control room guys might be already dead. It seems telling that the police 'decided' to use a water cannon on the reactor.

 

And apparently a fire engine is on the way from Tokyo to assist in pumping???????´

 

Why dont we see huge number of linemen connecting up the power as a national priority? Why is connecting the lines the second priority??

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Not necessarly. All the control room guys might be already dead. It seems telling that the police 'decided' to use a water cannon on the reactor.

 

And apparently a fire engine is on the way from Tokyo to assist in pumping???????´

 

Why dont we see huge number of linemen connecting up the power as a national priority? Why is connecting the lines the second priority??

agreed, i don't know why they wait to see if helicopter drops are successful; why not try both heli drops and water-cannon simultaneously?

 

I think this operation seems to be mismanaged, but we are not there so we don't know the details.

I suspect the reactors' pumps would not be able to be powered in their current state.

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