Cherenkov radiation

[strange6]

I'm a qualified nuclear engineer so I thought I would offer my services to those who are interested in the current japanese nuclear reactor story in terms of answering any questions that you may have. I have attached a photograph of what a real reactor core would look like. 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. I think that nuclear science is absolutely fascinating so feel free to ask any questions that you may have!

 

[Hydro]

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.

As seen in the unfortunate demise of Louis Slotin at Los Alamos after messing around with fissile material for a bomb core, but he took days to die, the poor sod.

Nuclear physics is something I take quite a keen interest in, ever since a tour of Dungeness B when I was young.

 

[strange6]

As seen in the unfortunate demise of Louis Slotin at Los Alamos after messing around with fissile material for a bomb core, but he took days to die, the poor sod.

Nuclear physics is something I take quite a keen interest in, ever since a tour of Dungeness B when I was young.

Yup, I think he was the only one within the room who was just that bit too close to the critical mass which was, in terms of volume/mass, miniscule. I believe Richard Feynman did some amazing mathematical calculations at the time that predicted his demise

 

[Some Might Say]

What kinda fallout are we talking if the reactor does meltdown?

 

[Hydro]

The same material also did for Harry Daghlian (it became known as the Demon Core). The risks these men took with fissile material is unbelievable.

The Demon Core was used in a test on Bikini Atoll in 1946, having claimed two lives before it was ever weaponised.

I've paid a visit to the reactor at the Technical University in Budapest, a small scale test reactor for the nuclear physics students. Fascinating place.

 

[strange6]

What kinda fallout are we talking if the reactor does meltdown?

Well, if the core does overheat and go into meltdown, then it would burn through the containing vessel into the ground and would hit groundwater which would result in massive hydrogen build-up and a big explosion which would would send all sorts of nasty radioisotopes into the atmosphere. The China Syndrome in other words. Not very good at all

 

[Some Might Say]

Well, if the core does overheat and go into meltdown, then it would burn through the containing vessel into the ground and would hit groundwater which would result in massive hydrogen build-up and a big explosion which would would send all sorts of nasty radioisotopes into the atmosphere. The China Syndrome in other words. Not very good at all

Oh dear. I remember they had to build a concrete base underneath the Chernobyl reactor to prevent a second explosion.

 

[strange6]

The same material also did for Harry Daghlian (it became known as the Demon Core). The risks these men took with fissile material is unbelievable.

The Demon Core was used in a test on Bikini Atoll in 1946, having claimed two lives before it was ever weaponised.

I've paid a visit to the reactor at the Technical University in Budapest, a small scale test reactor for the nuclear physics students. Fascinating place.

The material was actually Plutonium and they were experimenting at the time with subcritical neutrality using Beryllium. Unfortunatly Slotin cocked-up and allowed a Be reflector to fall into a prime position around the Pu core resulting in a flash of Chernekov radiation
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Oh dear. I remember they had to build a concrete base underneath the Chernobyl reactor to prevent a second explosion.

Not so much a second explosion because the first explosion did all the damage in that it blasted the actual reactor core and its contents into the atmosphere. They had to build a concrete sarcophagos over the actual exposed core, which was still burning intensely, to prevent it from releasing more radioactivity into the environment.

 

[ainsworth74]

They had to build a concrete sarcophagos over the actual exposed core

How's the effort to replace that going? Last I heard it was in a very poor condition with plenty of holes and in a poor state of repair raising fears that it could collapse and release a small cloud of radioactive concrete dust.

 

[strange6]

How's the effort to replace that going? Last I heard it was in a very poor condition with plenty of holes and in a poor state of repair raising fears that it could collapse and release a small cloud of radioactive concrete dust.

Yes, you're right. The original sarcophagos was a rush job and it soon started crumbling I believe. I believe a new generation sarcophagos is to be built before 2015 which should last at least 100 years

 

[Jonny]

I'm mildly suprised that Cherenkov radiation comes out blue: after all the Simpsons' intro scene has a glowing green one that Homer accidentaly takes home but loses down a drain on route (D'oh!). OK, so it's a cartoon.
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The same material also did for Harry Daghlian (it became known as the Demon Core). The risks these men took with fissile material is unbelievable.

The Demon Core was used in a test on Bikini Atoll in 1946, having claimed two lives before it was ever weaponised.

I've paid a visit to the reactor at the Technical University in Budapest, a small scale test reactor for the nuclear physics students. Fascinating place.

There's some interesting stuff on wikipedia about this, http://en.wikipedia.org/wiki/Louis_Slotin makes a good starting point.
It seems accurate enough, even by Wikipedia's standards. My interest is wanting to know what Enola Gay (the 1980 song) was named after...

 

[flymo]

It's hard to believe Chernobyl was 25 years ago now. There is an eerie sight about 15 or so miles SW of the nuclear site, where some of the vehicles that were used in the clean up of the incident are now stored, or rather abandoned. Helicopters, trucks, cars and other vehicles are there just rusting away. Nothing much else to be done with them really just a strange reminder of the incident.

 

[ralphchadkirk]

It's hard to believe Chernobyl was 25 years ago now. There is an eerie sight about 15 or so miles SW of the nuclear site, where some of the vehicles that were used in the clean up of the incident are now stored, or rather abandoned. Helicopters, trucks, cars and other vehicles are there just rusting away. Nothing much else to be done with them really just a strange reminder of the incident.

Pripyat is utterly abandoned now, so it's a very creepy, but good, reminder of what life was like towards the end of the Soviet regime. Things are (apart from the expected decay) exactly as they were left.
The only people left in it are a man and wife who refused to leave in 1986, and who refused to leave now. They live off the ground there, and are surprisingly, still alive.
I have always found nuclear physics and reactors in general fascinating, and in fact my father worked at Harwell in Oxfordshire on the research nuclear reactors.
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Well, if the core does overheat and go into meltdown, then it would burn through the containing vessel into the ground and would hit groundwater which would result in massive hydrogen build-up and a big explosion which would would send all sorts of nasty radioisotopes into the atmosphere. The China Syndrome in other words. Not very good at all

Apparently the core did partially meltdown. 160 people are now suffering from radiation sickness.

 

[Dennis]

My interest is wanting to know what Enola Gay (the 1980 song) was named after...

Check out the Sash remix of the OMD classic (is on youtube) for a short narrative.

 

[strange6]

It's hard to believe Chernobyl was 25 years ago now. There is an eerie sight about 15 or so miles SW of the nuclear site, where some of the vehicles that were used in the clean up of the incident are now stored, or rather abandoned. Helicopters, trucks, cars and other vehicles are there just rusting away. Nothing much else to be done with them really just a strange reminder of the incident.

Surprisingly, the local wildlife around Chernobyl is flourishing, despite the still very high levels of activity in the region. Remarkable

 

[Hydro]

I have always found nuclear physics and reactors in general fascinating, and in fact my father worked at Harwell in Oxfordshire on the research nuclear reactors.

I'm really interested in all those nuclear research facilities that cropped up in the 40's, 50's and 60's. The era of the "white heat of technology". The work of the AERE and AWRE really pushed what we understand about the components of the universe, never mind just nuclear weapons and power. A lot of the former AERE facilities are now closed and under decommissioning, but Culham and Harwell still thankfully thrive.

 

[WatcherZero]

Evacuation cordon around the Fukushima plants extended to 20km now, 170,000 people evacuated from their homes. After the explosion at Number 1 reactor it seems to be under control but now number 2 is on the verge of meltdown.


Now a totally different nuclear plant at Onagawa has declared a level 1 incident to the IAEA, rising radiation levels that they havent identified the source of.

 

[strange6]

Evacuation cordon around the Fukushima plants extended to 20km now, 170,000 people evacuated from their homes. After the explosion at Number 1 reactor it seems to be under control but now number 2 is on the verge of meltdown.


Now a totally different nuclear plant at Onagawa has declared a level 1 incident to the IAEA, rising radiation levels that they havent identified the source of.

I think it's No 3 actually which is a totally different type of reactor to that of No1 as it uses Plutonium fuel, as well as Uranium, which makes it that little bit more dangerous!

 

[Hydro]

The outer concrete shield on No.3 has exploded in a similar hydrogen related explosion, apparently. Another reactor has lost it's cooling system. The reactor containment is said to be holding. Radiation levels appear to be raised, but not as bad as could be, supposedly peaking at a level equivalent to a medical X-ray.

Really says something about the design of the reactor containment vessels to apparently withstand a gigantic earthquake and a powerful explosion, and for the radiation levels to be so low after such events.

 

[ainsworth74]

It's starting to get just a little bit exciting over in Japan:

Japan earthquake: Meltdown alert at Fukushima reactor

Technicians are battling to stabilise a third reactor at a quake-stricken Japanese nuclear plant, following the latest explosion to rock the facility.

Fukushima Daiichi plant's operators said they could not rule out a fuel rod meltdown, after a cooling system broke.

They are frantically injecting more water into reactor 2 after its fuel rods became almost fully exposed.

A cooling system breakdown preceded explosions at the plant's reactor 3 on Monday and reactor 1 on Saturday.

The latest blast, said to have been caused by a hydrogen build-up, injured 11 people, one of them seriously, and sent a huge column of smoke billowing into the air.

The Tokyo Electric Power Company, which runs the plant, is playing down any health risk,.

The utility says thick containment walls shielding the reactor cores have remained intact so far.

But the US said it had moved one of its aircraft carriers from the area after detecting low-level radiation 160km (100 miles) offshore.

Tens of thousands of people have been evacuated from a 20-km exclusion zone around the Fukushima Daiichi plant.

Experts say a disaster on the scale of Chernobyl in the 1980s is highly unlikely because the reactors are built to a much higher standard and have much more rigorous safety measures.

Source

 

[Hydro]

More water Captain!

Does the injection of water increase the likelihood of the accumulation of the hydrogen that leads to the explosions? I remember reading something about the Windscale fire about the reluctance to use water to cool the graphite pile, due to the possibility of the extreme temperatures stripping the water into oxygen and hydrogen, and causing an explosion. The Windscale event wasn't quite a meltdown in the traditional sense, rather more of a uranium fire in an air cooled graphite reactor, but the theory is similar.

EDIT: It wasn't the extreme temperatures, rather the molten metal oxidising on contact with water, creating hydrogen. If the Japanese reactor has partially melted, then the water coming into contact with the molten metal may be creating the hydrogen, which in turn is leading to the explosions?

 

[gordonthemoron]

It's been a long time since I worked at Windscale (as a student) and I'm now a bit hazy regarding the physics of reactors. The news reports keep speaking of cooling (water) but don't reactors have graphite control rods to stop the reaction?

as an aside, I have stood on top of the reactor at North Pile which caught fire in 1957

 

[Hydro]

I believe, in my rather limited understanding, that the control rods will stop the reaction, but the reactor continues producing decay heat as the fission products from the reaction decay. Like a radioactive version of letting boiling water cool down, it still produces steam even though it's off the heat.

 

[ralphchadkirk]

As far as I understand it, the control rods do not "stop" the reaction per se, but absorb the electrons which are being produced and then hitting other atoms - the chain reaction.

Hydro; I think my father worked on Daphne and Pluto (both of which have gone now I think). I've been to Harwell since, and it's a high tech physics park now with the addition of Diamond Light. The locals no longer think it's a jam factory!

 

[scotsman]

Just a myth-buster for those of you who believed what the news was spewing over the weekend.

UIAMM,

"radiation levels 1000x higher than normal" - caused by the venting of steam from the core, containing Hydrogen-14 - which has a half-life of 5 seconds! Therefore the levels would have been back to normal in less than 20 seconds and the Hydrogen-14 would have decayed away to practically nothing in under 2 minutes

 

[ralphchadkirk]

Just a myth-buster for those of you who believed what the news was spewing over the weekend.

UIAMM,

"radiation levels 1000x higher than normal" - caused by the venting of steam from the core, containing Hydrogen-14 - which has a half-life of 5 seconds! Therefore the levels would have been back to normal in less than 20 seconds and the Hydrogen-14 would have decayed away to practically nothing in under 2 minutes

You seem to be missing the fact that the entire core was uncovered by water for an unknown amount of time, which is what we're worrying about.

There were also Caesium isotopes present - it wasn't just Hydrogen-14.

 

[scotsman]

You seem to be missing the fact that the entire core was uncovered by water for an unknown amount of time, which is what we're worrying about.

There were also Caesium isotopes present - it wasn't just Hydrogen-14.

The point I was referring to was when that had not happened

 

[Peter Mugridge]

Interesting snippet in the Daily Telegraph today: The reactor which is causing the big problem is an older one that was designed to withstand a quake of magnitude 8.2; the more modern ones are designed to withstand a magnitude 9.0 ( which, incidentally, is the level to which this event has now been upgraded ).

 

[ainsworth74]

Interesting snippet in the Daily Telegraph today

Interesting that, but I think it's a bit of red herring. My understanding is that it is not the earthquake that is causing the present problems with the reactors but the combination of earthquake and then tsunami. The reactors behaved as intended during and in the immediate aftermath of the earthquake (i.e. they shut down and switched to back up generators) however when the tsunami hit it knocked out the generators (leaving the cooling running on short term batteries) and caused further damage that has now led to the present situation. If it had just been an earthquake I don' think we would be having the present problems.

 

[ChrisCooper]

The big problem doesn't seem to be the reactors themselves though, or the earthquake, but the Tsunami taking out the backup diesel generators which were supplying the emergency cooling. The quake alone would probably have not caused any problems, beyond shutdown.

See me and ainsworth74 posted almost exactly the same at the same time!