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Nuclear events taking place in Japan.

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Adam Munich

Sun Apr 03 2011, 02:20AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

A reactor likely went critical. Blue flashes of light are associated with practicality accidents...

Nah

Mon Apr 04 2011, 01:05AM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

Sigh.....

What will happen to the dream of nuclear power now?

Proud Mary

Mon Apr 04 2011, 01:21AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Grenadier wrote ...

A reactor likely went critical. Blue flashes of light are associated with practicality accidents...

Blue ÄŒerenkov radiation is commonly seen in 'swimming pool' reactors and spent fuel pools in the normal course of operation. ÄŒerenkov radiation is produced when beta particles travel faster than the phase velocity of light in water.

big5824

Mon Apr 04 2011, 01:26AM

Registered Member #1687 Joined: Tue Sept 09 2008, 08:47PM
Location: UK, Darlington
Posts: 240

To me the big question now is will these events help or hinder the development of fusion power?

Adam Munich

Mon Apr 04 2011, 04:59AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

I'm well aware what ÄŒerenkov radiation is, but there are 2 possibilites:

1) A bright blue flash in the air, seen with other criticality accidents such as the demon core mishaps most certainly means the reactor went critical.

2) A bright flash of ÄŒerenkov radiation, which means the reactor has had a huge surge in power (gone critical).

Patrick

Mon Apr 04 2011, 05:18AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Grenadier wrote ...

I'm well aware what ÄŒerenkov radiation is, but there are 2 possibilites:

1) A bright blue flash in the air, seen with other criticality accidents such as the demon core mishaps most certainly means the reactor went critical.

2) A bright flash of ÄŒerenkov radiation, which means the reactor has had a huge surge in power (gone critical).

The blue flash is not Cherenkov radiation for in-air-criticality events, its just energetic nitrogen and oxygen, but the blue light from reactors(tions) underwater (or other dielectric medium) is definately Cherenkov radiation. These two cases are often misconstrued as being the same, Just to be clear.

Energetic Nitrogen-Oxygen blue glow and Cherenkov blue glow are both signs of criticality. (EDIT: but also other emissive conditions too, not just critcality)

Steve Conner

Mon Apr 04 2011, 06:58AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The linked article doesn't say that anyone actually saw any blue flashes of light around the Fukushima site, though. Tepco say that they detected neutrons 1.5km away, which is almost as worrying.

Proud Mary

Mon Apr 04 2011, 08:56AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Grenadier wrote ...

I'm well aware what ÄŒerenkov radiation is, but there are 2 possibilites: ... A bright flash of ÄŒerenkov radiation, which means the reactor has had a huge surge in power (gone critical).

This isn't right. ÄŒerenkov radiation might be seen when a reactor had 'a huge surge in power,' but is also commonly seen in spent fuel cooling pools which have not 'gone critical':

"Cherenkov light emission and detection
Cherenkov light is created as particles move faster than the speed of light in a certain medium. In water pools with spent nuclear fuel, this light appears as a result of gamma-ray interaction with the water. Photons emitted from the spent fuel Compton scatter on electrons in the water, thereby giving them enough energy to reach the high speeds needed for Cherenkov light emission. Due to its short wavelength of typically 280-400 nm, the light appears bluish. Relatively strong Cherenkov light seen in the pool can be taken as evidence of irradiated fuel assemblies being present, since only strong sources of radioactivity have this effect."

See: Modelling Cherenkov light from irradiated nuclear fuel assemblies using GEANT4 here:

Nicko

Mon Apr 04 2011, 02:49PM

Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615

Proud Mary wrote ...

Cherenkov light is created as particles move faster than the speed of light in a certain medium.

The above sentence is a tad misleading - specifically, this is only the phase velocity component of a particle in a dielectric medium exceeding the phase velocity of light in that medium.

Proud Mary

Mon Apr 04 2011, 02:53PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Nicko wrote ...

Proud Mary wrote ...

Cherenkov light is created as particles move faster than the speed of light in a certain medium.

The above sentence is a tad misleading - specifically, this is only the phase velocity component of a particle in a dielectric medium exceeding the phase velocity of light in that medium.

I wrote above: ÄŒerenkov radiation is produced when beta particles travel faster than the phase velocity of light in water.

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