Cherenkov radiation

[Hydro]

Can only hope it's similar to the previous ones, a hydrogen explosion that does not damage the primary containment. It's almost as if something is conspiring to throw all destructive forces at these reactors, an earthquake, tsunami, explosions....what's next, a meteor strike?

 

[WatcherZero]

Blast at Reactor No. 2, the well at the bottom of the containment vessel appears to have been blown out, all but 50 staff have been evacuated.

Now a fire broke out at a spent fuel pond at Reactor No. 4 IAEA says large amount of radiation released into the atmosphere. Everyone within 30km told to stay indoors and a 30km no fly zone has now been implemented. Reports radiation levels at No. 2 reactor where the containment vessel has been damaged are 400x legal safe limit.

 

[ralphchadkirk]

Blast at Reactor No. 2, the well at the bottom of the containment vessel appears to have been blown out, all but 50 staff have been evacuated.

Now a fire broke out at a spent fuel pond at Reactor No. 4 IAEA says large amount of radiation released into the atmosphere. Everyone within 30km told to stay indoors and a 30km no fly zone has now been implemented. Reports radiation levels at No. 2 reactor where the containment vessel has been damaged are 400x legal safe limit.

Getting very serious now. They reckon the containment vessel of the reactor has been damaged for the first time - apparently radiation levels rose to 8 times the annual permitted dose.

 

[WatcherZero]

The cause of the fire at Reactor No. 4 spent fuel pond appears to be another hydrogen explosion smaller than the three previous ones. The firs is out now thankfully. New report from the government, tempertures rising at another two reactors.

 

[boing_uk]

Unfortunately, I do fear that the media are just fuelling the drama and not actually being wholly truthful.

"Radiation 8 times normal". Whats normal? Radiation is high in Cornwall, for instance compared to say somewhere like Lincolnshire. Is Cornwall being evacuated?

And what are the radiation products being released? Are they long half life products, or short ones?

At this stage I am not succumbing to the panic and hysteria being bandied around; there is no real evidence one way or the other and the news stories are making it sound as though it is now the fault of the nuclear power stations that people are without food homes and shelter.

 

[ralphchadkirk]

"Radiation 8 times normal". Whats normal? Radiation is high in Cornwall, for instance compared to say somewhere like Lincolnshire. Is Cornwall being evacuated?

The readings by the reactor are 400mS/hr. The average annual dosage is 3 mS.

And what are the radiation products being released? Are they long half life products, or short ones?

Make your own mind up - the Japanese government have told all in 30km of Fukushima to stay inside.

 

[strange6]

Okay boys and girls.. all this talk about neutrons, uranium 238, deuterium, tritium and so on is all very easy and a waste of our time. Frankly, it's rather patronising to think we don't all know everything there is to know already.

Can we therefore get back to talking about the more complicated things like UK railway ticketing and interpreting the NrCOC?

Errrr, please note the title of this child forum - General Discussion. That means non- railway related topics

 

[jon0844]

Can only hope it's similar to the previous ones, a hydrogen explosion that does not damage the primary containment. It's almost as if something is conspiring to throw all destructive forces at these reactors, an earthquake, tsunami, explosions....what's next, a meteor strike?

No, it's the wanting from the world media for something horrible to happen.

Sky in particular seem dead set on painting the worst possible picture and will probably be disappointed if half the country isn't wiped out.

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Errrr, please note the title of this child forum - General Discussion. That means non- railway related topics

[facepalm]
Oh my god. It was a joke. I deliberately didn't put a smiley as I thought my comment would be obvious.
[/facepalm]

Oh,

:cry:

 

[WatcherZero]

The radiation level in Chiba near Tokyo has risen to first 4x background radiation and now 10x background radiation, its downwind of any leaks at Fukashima. There are two 8m sq. holes in the reactor No.4 outer building after the earlier small blast, the water level in the spent fuel storage pond where the earlier fire occured is now falling as its in the process of boiling away.

 

[umontu]

No, it's the wanting from the world media for something horrible to happen.

Sky in particular seem dead set on painting the worst possible picture and will probably be disappointed if half the country isn't wiped out.

Isn't that how Sky always likes things?

Through having read bbc news it sounds to me like it is going to happen.

 

[jon0844]

Sky does seem to be gradually becoming more like Faux News, like having silly sound effects and now having created a montage of tsunami videos with awful music/sound effects as if it's some Hollywood movie trailer - and not one of death and destruction and REAL LIFE.

To be fair to Sky, they have resisted certain changes that would have made them a carbon copy of Fox years ago - but when it's a gradual change, it's perhaps even worse as people don't notice. Had they changed overnight, I'm sure there would have been an uproar.

 

[umontu]

Well this is their home page as of now, looks like a poster for a disaster film. It's obviously been done up in photoshop.
I think they've taken it too far, personally.

Anyways back to the reactor, Strange6 is this likely to do something similar to Three mile island? And how likely is it going to effect the world in terms of radioactive materials released?

 

[WatcherZero]

Ive found BBC has been more on the ball on the Japanese coverage posting stuff a couple of hours before Sky whereas usually Sky is the first to post stuff as they dont verify it first. I imagine having a proper foreign new translation service is helping them here while Sky is waiting on stuff to be translated to English by other broadcasters.

 

[Hydro]

The readings by the reactor are 400mS/hr. The average annual dosage is 3 mS.

Make your own mind up - the Japanese government have told all in 30km of Fukushima to stay inside.

Sensible precautions. Until it is determined what products are being released, how far the material is being spread, and the persistance of the radioactivity, it's common sense. Highly unstable radioactive material can produce extremely high levels of radiation at and close to the source, but these products are so unstable, they tend to vanish pretty quickly. What may be 400mS/hr at one distance, will be steadily reducing the further you get from the source. However, there may be more persistant particles with longer half lives that could present a much greater health risk.

When I was in the military doing Chemical, Biological, Radiological and Nuclear combat training, part of the Chemical part was dealing with what was known as "persistent agents". Chemicals that once disseminated, tended to hang about and present a risk. Some chemical agents were incredibly poisonous, yet were easily dispersed to harmless quantities (for example, some gaseous agents easily scatter to the wind into concentrations low enough to present very little risk). Something similar happens to radioactivity, except in this case it's to do with the stability of the product. Unstable, highly radioactive compounds don't "persist", they decay far too quickly. However, others can hang about a lot longer. It will pay to see what particles through analysis what exactly this reactor is chucking out.

In the meantime, it's entirely sensible to take all precautions necessary.

 

[ralphchadkirk]

If that were true, surely the exclusion zone would have been 20km straight off as soon as they knew radioactive particles were being released. The fact that its been increased slowly over time suggests they know what is coming out is quite dangerous. Of course, it's also in the governments best interests to keep people thinking it's safe so as not to cause a mass panic.

 

[Hydro]

The fact that its been increased slowly over time suggests they know what is coming out is quite dangerous.

Of course, there are a lot of factors at play here. The strength of the explosion could throw radioactive dust far and wide quickly, prevailing winds can carry them further quicker, widening the area of contamination. Radioactive decay is about time. If the particles were fairly confined and not going anywere, then high radiation levels will be contained long enough to decay fairly harmlessly. As there have been explosions, even the wind strength, these particles are not waiting out their decay period statically, they are potentially now decaying at the same rate, but whilst being thrown at great speed over a wide distance. They may still cease being radioactive rather quickly, except they have travelled further as they are moving faster.

All speculation though, I'm just trying to consider all possibilities. The authorities of course will plan for the worst case, which is extremely prudent.

EDIT: Radiation levels are reportedly falling, according the BBC.

 

[WatcherZero]

Perssonel at two US airbases 200 miles from Fukushima have been ordered to stay inside after radiation was detected, its obviously travelling with the wind.

 

[ralphchadkirk]

Hydro; the critical factor seems to be the state of decay the particles were in at the moment they were released from the reactor. Of course, there are billions of them at different states, so it's an impossible task.
Now, they need to know the spread of particles, the isotopes involved and the half lives tk be able to deal with it.

 

[Hydro]

That's the challenge, tracking the spread of any contamination and trying to contain it if needs be. The hope is that it can blow out to sea away from populated areas and disperse in it's own time, which hopefully is likely with a release of radioactive steam. It's any radioactive dust from the explosions that would be the major issue as obviously the dust will fall back to earth.

 

[strange6]

No, it's the wanting from the world media for something horrible to happen.

Sky in particular seem dead set on painting the worst possible picture and will probably be disappointed if half the country isn't wiped out.

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[facepalm]
Oh my god. It was a joke. I deliberately didn't put a smiley as I thought my comment would be obvious.
[/facepalm]

Oh,

:cry:

You fool, man! Unfortunately, I'm no mind reader as to the tone of a post if you don't put a smiley! Grrrrrrrrrrrrrrrrrrrr

 

[Dennis]

All this talk about Sieverts has got me baffled; anyone care to explain in words of one syllable or less what one is and how it is relevant?

 

[Barn]

The blue image that you see is called Cherenkov radiation and if ever you saw such a phenomenon in air (the photo is taken with the source (a mini, experimental reactor core) in water)you would be dead within seconds, having been exposed to a lethal amount of radiation.

Technically speaking, would Cherenkov radiation actually exist in air?

 

[boing_uk]

All this talk about Sieverts has got me baffled; anyone care to explain in words of one syllable or less what one is and how it is relevant?

They're a bit like perverts, but smaller, and exposure to them over the long term is just as damaging.

For instance; a quick flash of a winkie isnt going to damage you too much; but a full on instance of nastiness... well, you get the idea and its scalability. Similarly with radiation; a 400mSv blast over the space of 30 minutes isnt going to do you that much harm - but at that level over the day is going to make you a little ill.

 

[jon0844]

Interesting comparison. Now if only Sky could use that same analogy!

 

[Hydro]

Technically speaking, would Cherenkov radiation actually exist in air?

I'm sure it does, I think it's been has been observed in cyclotrons in the 1930's.

 

[ralphchadkirk]

Technically speaking, would Cherenkov radiation actually exist in air?

Yes - have a look at the Goiânia accident IAEA report. Although there is debate as to whether it was fluorescence or Cherenkov radiation.

 

[LexyBoy]

Yes - have a look at the Goiânia accident IAEA report. Although there is debate as to whether it was fluorescence or Cherenkov radiation.

Presumably since the phase velocity of light in air is pretty close to c, the Cherenkov radiation observed would be much less.

Could Cherenkov radiation be considered as a kind of fluorescence anyway? The process seems similar albeit caused by a polarisation rather than excitation. (IANANP).

 

[strange6]

Technically speaking, would Cherenkov radiation actually exist in air?

Don't quote me on this (it's a long time since I have done nuclear physics) but I think technically, it would be very, very unlikely that Cherenkov radiation would be seen in air. You do need some kind of dielectric medium (like water) for it to be visible. However, a blue glow or flash can be seen in air during criticallity accidents but it probably wouldn't be Chernekov radiation. Instead, it would be the spectral emission (in the UV region of the Electromagnetic spectrum) of excited nitrogen and oxygen ions in the air, these excited ions being caused by the intense energy emitted by the 'radiation' of the criticality accident, when they are returning to their 'ground states' i.e unexcited states.
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Presumably since the phase velocity of light in air is pretty close to c, the Cherenkov radiation observed would be much less.

Could Cherenkov radiation be considered as a kind of fluorescence anyway? The process seems similar albeit caused by a polarisation rather than excitation. (IANANP).

It wouldn't be observed at all for values close to c. For cherenkov radiation, the speed of a charged particle must have a value greater than c. That's why you are very unlikely to see Cherenkov radiation in air because you would need to energise the particle hugely for it to penetrate the air at speeds greater than that of light. And even a nuclear fission process would not generate that amount of energy needed

 

[Spaceflower]

Surely, the water they're spraying on the reactors will end up radioactive. Where will this end up.

 

[ralphchadkirk]

It wouldn't be observed at all for values close to c. For cherenkov radiation, the speed of a charged particle must have a value greater than c. That's why you are very unlikely to see Cherenkov radiation in air because you would need to energise the particle hugely for it to penetrate the air at speeds greater than that of light. And even a nuclear fission process would not generate that amount of energy needed

Why does the IAEA recognise that it could be Cherenkov radiation then?