spontaneous wigner energy releases causing graphite fires.

matthewwight
Posts: 47
Joined: Apr 25, 2011 10:01 pm

spontaneous wigner energy releases causing graphite fires.

Post by matthewwight » Jul 11, 2018 10:44 pm

I have an opponent who claims that spontaneous wigner energy releases cause graphite fires.

Is this applicable to a LFTR?

How can I best rebuke claims that this is a valid safety concern for LFTRs?

Thanks for all your help.

E Ireland
Posts: 1561
Joined: Jun 19, 2013 11:49 am

Re: spontaneous wigner energy releases causing graphite fire

Post by E Ireland » Jul 12, 2018 3:59 am

almost all graphite moderated power reactors keep the graphite sufficiently hot that the amount of Wigner energy that can build up will be extremely small.
This is especially true for an MSR because the graphite temperature will be well over 500C

matthewwight
Posts: 47
Joined: Apr 25, 2011 10:01 pm

Re: spontaneous wigner energy releases causing graphite fire

Post by matthewwight » Jul 12, 2018 8:14 am

Thank you for pointing me in the right direction. I was able to dig up a lot of material that confirms this.

E Ireland
Posts: 1561
Joined: Jun 19, 2013 11:49 am

Re: spontaneous wigner energy releases causing graphite fire

Post by E Ireland » Jul 12, 2018 10:25 am

matthewwight wrote:Thank you for pointing me in the right direction. I was able to dig up a lot of material that confirms this.
You're welcome.
The fun thing is that earlier Magnox stations (like the UKAEA reactors at Calder Hall and Chapelcross, and the first CEGB station at Bradwell) had provision to shutdown the reactors for a Wigner annealing, and the reactors at Bradwell were originally to be built with special modifications to the fuel channels to increase graphite temperature (sleeves to reduce gas exposure to the graphite), before improving heat transfer temperatures made it all redundant.

modifiedgenes
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Joined: Dec 09, 2017 4:31 pm

Re: spontaneous wigner energy releases causing graphite fire

Post by modifiedgenes » Jul 28, 2018 1:32 pm

Please bear with me, for I am nothing but an enthusiastic amateur at best, but does nuclear/reactor grade graphite even burn?

There are many contrasting opinions and viewpoints across a variety of sources, my understanding is that you won't burn graphite even with oxy-ace torches. It just doesn't want to cooperate.

Of course people may get confused with accidents like the Windscale fire where it was the fuel (and probably some of the cladding) that burned.

E Ireland
Posts: 1561
Joined: Jun 19, 2013 11:49 am

Re: spontaneous wigner energy releases causing graphite fire

Post by E Ireland » Jul 28, 2018 3:57 pm

modifiedgenes wrote:Please bear with me, for I am nothing but an enthusiastic amateur at best, but does nuclear/reactor grade graphite even burn?

There are many contrasting opinions and viewpoints across a variety of sources, my understanding is that you won't burn graphite even with oxy-ace torches. It just doesn't want to cooperate.

Of course people may get confused with accidents like the Windscale fire where it was the fuel (and probably some of the cladding) that burned.
It won't "burn" as such, but smouldering oxidation is a significant threat.
The rate of oxidation, whilst relatively low, is sufficiently high that it can cause the core to overheat in an accident.

modifiedgenes
Posts: 23
Joined: Dec 09, 2017 4:31 pm

Re: spontaneous wigner energy releases causing graphite fire

Post by modifiedgenes » Jul 31, 2018 6:41 pm

That explains that for me, thank you.

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