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 Post subject: Tritium risks
PostPosted: Sep 03, 2015 10:52 am 
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I understand that tritium is generated in practically all nuclear reactors and more is generated with lithium and it is common practice to capture the tritium.
If we don't capture the tritium, large scale nuclear power will easily more than double atmospheric tritium levels and this would be easy to measure.
My question is: As long as background level of radiation from all sources remains reasonable, is there any rational reason to particularly fear tritium or how much might it be all right to increase atmospheric levels of tritium?


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 Post subject: Re: Tritium risks
PostPosted: Sep 03, 2015 8:54 pm 
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I am quite convinced that hormesis is the general law of the biosphere. But I also suspect there may be a reverse effect even there.

The hormesis effect in radiation damage occurs because radiation has an up-rating effect on repair activity. So even though the radiation does damage proportional to dose, it also (to a point) up-rates repair activity in excess of that damage. Thus the harm is reduced.

HOWEVER, it seems plausible to me that the ultra low energy of a tritium ß decay might fail to cause the up-rate effect so tht the damage would still occur but the added repair would not. Thus, it may be that tritum is the only isotope (or among the very few) for which hormesis does NOT apply.

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 Post subject: Re: Tritium risks
PostPosted: Sep 04, 2015 1:57 am 
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KitemanSA wrote:
I am quite convinced that hormesis is...
Radiation hormesis is linked to the well-known pseudoscience of homeopathy. This hypothesis is often discussed by nuclear power proponents who would like to claim "radiation is good for you". Their lunatic fraction considers it completely true and proven, while ignoring the fact that it's not accepted by international authorities. Professional wingnut Ann Coulter has taken a shine to this theory as well, stating that the radiation released during the Fukushima disaster is healthy and would prevent cancer.

moderator, lockdown request.


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 Post subject: Re: Tritium risks
PostPosted: Sep 04, 2015 5:23 am 
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A quick look here https://en.wikipedia.org/wiki/Tritium allows some comparisons:

Quote:
Worldwide, the production of tritium from natural sources is 148,000 terabecquerels per year. The global equilibrium inventory of tritium created by natural sources remains approximately constant at 2,590,000 terabecquerels.


and:
Quote:
In January 2014 it was made public that a total of 875 TBq (2.45 g) of tritium are on the site of Fukushima Daiichi,


So if ALL the tritium at Fukushima got released, it would add 1 part in 3000 to global tritium levels. If we had 3,000 reactors of similar scale to Fukushima, with no measures to capture trtium, yes, we could double the natural amounts of tritium.

Most of the tritium is captured. The MSR designs can capture it and bottle it as water. it can then be sold on:

Quote:
Commercial demand for tritium is 400 grams per year[3] and the cost is approximately US $30,000 per gram.[31]


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 Post subject: Re: Tritium risks
PostPosted: Sep 04, 2015 6:22 am 
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Turns out highly tritiated water is a very difficult thing to store.
It corrodes welds like there is no tomorrow.
That is why tritium is stored as a dry hydride normally.


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 Post subject: Re: Tritium risks
PostPosted: Sep 04, 2015 10:40 am 
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E Ireland wrote:
Turns out highly tritiated water is a very difficult thing to store.
It corrodes welds like there is no tomorrow.
That is why tritium is stored as a dry hydride normally.


Interesting. Why is it so different to normal water?

I suppose if you get a trutium turning into a helium you have a OH wondering around looking for something to corrode.

Would it be easier just to freeze it in ice cubes?


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 Post subject: Re: Tritium risks
PostPosted: Sep 04, 2015 12:10 pm 
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Its a combination of the direct decay effect you mention creating .OH radicals as well as simple ionisation by the beta particles being pumped out by the decaying nuclei.

Tritiated water ends up full of various free radicals which attack anything and everything.
As welds disrupt the crystal structure of the metal they are the most obvious places to be attacked.

Freezing it would probably help - but I am not sure what the heat being pumped out by 90% tritiated water is like.


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 Post subject: Re: Tritium risks
PostPosted: Sep 04, 2015 3:04 pm 
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E Ireland wrote:
Freezing it would probably help - but I am not sure what the heat being pumped out by 90% tritiated water is like.

I am just an amateur, but here is my estimate (which was fun to do):
Molecular weight is about 16+3+3=22
Number of molecules/g ~= 6.0221415 * 10^23 * 12/22 ~= 3.28 * 10^23 /g
Energy from decay about 18.6 keV * 1.60218*10^-19 J/eV ~= 2.9 * 10^-15 J
Half-life of H-3: 389 Ms -> f(t) = e^(-t*ln(2)/(389*10^6)) describes number of H-3 remaining -> ln(2)/(389*10^6) ~= 1.78 * 10^-9 is number of decays/s at t=0.
Multiplying to get W/g: 3.28 * 10^23 * 2.9 * 10^-15 * 1.78 * 10^-9 ~= 1.69 W/g so about 1.5W/g at 90% tritium or 1.5 kW/kg.
Edit cause I forgot that: 2 tritium/molecule means twice the energy: 3 kW/kg.
Seems difficult to store as ice.


Last edited by Koistinen on Sep 05, 2015 6:42 am, edited 2 times in total.

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 Post subject: Re: Tritium risks
PostPosted: Sep 04, 2015 4:11 pm 
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BSFusion wrote:
KitemanSA wrote:
I am quite convinced that hormesis is...
Radiation hormesis is linked to the well-known pseudoscience of homeopathy.

Ridiculous. The majority of data supports hormesis. Please educate yourself before making such ludicrous statements in the future.

Start here:
http://radiationeffects.org
http://dose-response.org
http://www.belleonline.com/newsletters.htm

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 Post subject: Re: Tritium risks
PostPosted: Sep 05, 2015 7:14 am 
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BSFusion wrote:
KitemanSA wrote:
I am quite convinced that hormesis is...
Radiation hormesis is linked to the well-known pseudoscience of homeopathy. This hypothesis is often discussed by nuclear power proponents who would like to claim "radiation is good for you". Their lunatic fraction considers it completely true and proven, while ignoring the fact that it's not accepted by international authorities. Professional wingnut Ann Coulter has taken a shine to this theory as well, stating that the radiation released during the Fukushima disaster is healthy and would prevent cancer.

moderator, lockdown request.

The statements of Ann Coulter are an unreliable source of information on how the world works. Look at better sources, such as those suggested by KitemanSA.


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 Post subject: Re: Tritium risks
PostPosted: Sep 05, 2015 9:36 am 
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I've often said that TEPCO should take all its tritiated deionized water to a stable glacier in the artic or antarctic and freeze it into said glacier. There it will stay for the ~120 years it needs to disappear.

That way, they don't have to try to remove it (concentrate it) from thelarge volumes of water they have in their tanks.

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 Post subject: Re: Tritium risks
PostPosted: Sep 17, 2015 12:59 am 
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Here is my understanding of the risks and uses of tritium so far:

Large scale nuclear development (1PW) would increase the production of tritium on earth by about 10-1000 times.

If it were released into the air or oceans, the risks are unknown but likely small. They could be understood better, particularly the mitigating effect of hormesis.
The radiation from tritium is different because it is weaker, and it can be speculated that the weakness would fail to provoke hormesis. The ultraviolet sunlight which is 1000 times weaker and still seem to provoke hormesis as seem to be indicated by the fact that people who get plenty sun tend to get more skin cancer but less of other cancers, I think enough less to make it a small benefit except for those who get sunburned rather than tanned.

The captured tritium can today be sold at about USD 30k/g with 400 g/year used but with increased production the price should go down unless people figure out new ways to use it, perhaps in fusion reactors? With the molten salt designs it would be easier to produce concentrated tritium as it need not get diluted in water.

There is an idea of storing it in ice in the arctic or antarctic, though this would not help if the ice melts through climate change, but that would of course be a much bigger problem than the release of tritium.

Anyone got something to add?


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 Post subject: Re: Tritium risks
PostPosted: Sep 17, 2015 7:45 pm 
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It seems to me that the Fukushima water could be pumped into a deep aquifer. Some aquifer are salty and unusable for drinking and known to have water that has not been near the surface for thousands of years. Any excess time and money spent on the tritium problem delays the rest of the cleanup effort.

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 Post subject: Re: Tritium risks
PostPosted: Sep 19, 2015 1:03 pm 
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BSFusion wrote:
KitemanSA wrote:
I am quite convinced that hormesis is...
Radiation hormesis is linked to the well-known pseudoscience of homeopathy. This hypothesis is often discussed by nuclear power proponents who would like to claim "radiation is good for you". Their lunatic fraction considers it completely true and proven, while ignoring the fact that it's not accepted by international authorities. Professional wingnut Ann Coulter has taken a shine to this theory as well, stating that the radiation released during the Fukushima disaster is healthy and would prevent cancer.

moderator, lockdown request.


Homeopathy is nonsense because it postulates an effect from 'nothing' ... dilution until the active species is not present, and then some 'memory' in the solvent, which has no physical basis. Hormesis is clearly not nonsense ... it's true for many toxins ... because biological systems have defense mechanisms that persist after exposure.

It pretty easy to say ... 'theory I don't like' is just like 'the moon is made of green cheese' ... it's hardly a rational argument.


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 Post subject: Re: Tritium risks
PostPosted: Sep 23, 2015 5:56 pm 
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Tritium production from BWR's are particularly low 10x lower than PWRs which in turn are much lower than CANDUs. Molten salt reactors with beryllium are about half of CANDUs and with lithium and beryllium about the same.

Storage of tritium is normally done as a hydride. For a 1GWe power plant you need around 4 kg of titanium to serve as the collector of tritium - expanded by however much hydrogen you have bleeding into the system.

Storing as water is generally not recommended as water spills and leaks etc. The hydride form needs to be heated to 500C or more to release it.

Never worried about the heat generation - it is pretty small.


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