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struggle4progress Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Jan-28-05 08:14 PM
Original message
Construction completed at SRS tritium extraction facility
The Associated Press
January 28, 2005

<snip> Westinghouse Savannah River Co., which oversees daily operations at the Savannah River Site, was penalized by the Department of Energy in 2003 for delays and cost overruns. <snip>

The $506 million project is key to the nation's nuclear weapons stockpile. The new facility restores the country's ability to make tritium, which hasn't been produced since 1988. Tritium, a radioactive form of hydrogen gas, is needed for modern nuclear weapons but decays quickly and needs to be replenished. <snip>

Keeping hydrogen bombs working ...

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NNadir Donating Member (1000+ posts) Send PM | Profile | Ignore Fri Jan-28-05 11:03 PM
Response to Original message
1. Tritium, besides keeping nuclear weapons working is an essential
Edited on Fri Jan-28-05 11:45 PM by NNadir
tracer material in research.

It is worth noting that there are quite literally millions of persons on the planet today who would be dead without the the technological availability of tritium.

Many people fantasize about an age of fusion power. Without access to tritium, such even discussing such an age would be impossible.

Like all technological materials, including, say gasoline, tritium has its positive uses and its negative uses. Sane people do not advocate the construction of nuclear weapons; but on the other hand neither would sane and moral people demand that tritium be banned.

Like Carbon-14, tritium is a naturally occurring material, resulting from the interaction of cosmic rays with the upper atmosphere. The total amount of tritium existing from natural sources is roughly 7 kilograms. Roughly 5.5% of tritium decays each year, meaning that in order to maintain tritium inventories, about 400 grams must be produced each year in the atmosphere.

Less than 1% of the Tritium now found on earth was formed naturally. Most of the tritium now existent formed in the super high neutron fluxes found in nuclear explosions (including underground nuclear explosions), the manufacture of hydrogen bombs and the operation of nuclear reactors, especially those moderated by heavy water, like the CANDU. The tritium formed in the latter case is unfortunately not recoverable since its concentration is extremely low relative to deuterium, it's mother isotope. (Deuterium has a very low neutron capture cross section which is why it is used in these types of reactors.)

Commercially tritium is made from Li-6 by placing it in a neutron flux. The nuclear reaction by which it is created commercially is the Li-6(n,alpha)H-3 reaction. This reaction is often performed in university research reactors.

Interestingly, the major toxicity associated with tritium has very little to do with its radioactivity. Organisms containing large amounts of tritium die because of the profound isotope effect associated with tritium. This is because the ratio of masses for tritium and ordinary hydrogen-1 is the highest for any two isotopes of the same element known. Because hydrogen bonding, hydride transfer, and proton transfers are essential to life, the slowing of these reactions due to isotope effects is often fatal. (This same effect is possible using ordinary heavy water, deuterium oxide, but it is nowhere near as pronounced.)

Even increased by a ration of 99:1 with respect to its natural occurrence, the radioactivity associated with all the tritium is completely trivial when compared with naturally occurring radiation. The radioactivity of the ocean associated with the natural occurrence of potassium-40 in seawater for instance is roughly 500 billion curies (2 X 10^22 Beq). Normal operation of nuclear power plants worldwide produce about 4.0 X 10^15 Beq of Tritium (4 hundred thousand curies) or 1/20 millionth of this activity on a decay basis. Since however the energy of tritium decay is much lower than the far more dangerous K-40 however, the total dose equivalent for tritium is extremely trivial.

It is estimated that the total exposure to tritium from all sources, weapons testing, nuclear power production, tritium in medical testing and tracer studies, and nuclear weapons production accounts for an absorbed dose of 2.6 X 10^-8 Gray per year. Since a fatal dose of radiation is about 300 gray (LD50) this means that the total exposure is about 1 ten billionth of a fatal dose. For beta decaying isotopes like tritium, the conversion between grays and Sieverts is unity. The background radiation that most people experience is about 3.6 X 10-3 Sieverts = (for tritium) 3.6 X 10^-3 Gray. This means that the total dose equivalent radioactivity for tritium of all sources is (2.6 X 10-8)/(3.6 X 10-3) = 7 X 10^-6 or 1 seven millionth of total background from natural sources. (For people who live in Denver or other places at high altitude, or who fly alot on airplanes, background radiation is much higher than this figure.)

Thus concern about tritium exposure is a tempest in a very tiny teapot.

The amount of tritium in nuclear weapons, while classified, is not huge. In fact most thermonuclear weapons generate much of their tritium for fusion reactions in situ, from the lithium in lithium deuteride, which forms tritium with the high neutron flux available in nuclear explosions. Here is a somewhat detailed description of a thermonuclear weapon. Note the presence of a small amount of tritium and deuterium gas at the core of the primary.

One important research use for tritium is to obtain its decay product, Helium-3, which is not available on earth by any natural process and is best obtained by collecting the decay product of tritium. (This takes some patience since the half-life of tritium is about 12.26 years.) The properties of Helium-3 have lead to new understandings of the properties of matter. Liquid helium-3 has essentially zero viscosity and will actually flow up the walls of containers in which it is kept. Formerly helium-3 was very important in extremely low temperature cryogenic work, although magnetic cooling techniques have rendered this use somewhat less important than it once was.

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struggle4progress Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Jan-29-05 06:51 PM
Response to Reply #1
3. Hmmm. I consider much of what you say misleading, at best.
It is true that T can be a useful label in biochemical research. But its sometime use as a tracer in hydrogeological studies is completely unnecessary: stable isotopes provide a satisfactory alternative.

Nobody gets very excited about external beta exposure, but internal exposure is very different story. Because free T is naturally lost with the radiolytic decomposition of labelled compounds, and (being very small) passes easily through gloves and other normal laboratory protective gear, contact with labelled compounds or breathing air in contact with labelled compounds will likely provide an internal radiosource. Similarly, contact with or respiration of a tritiated water (say THO) will provide an internal source.

Mean residence time for absorbed T is believed to be of the order of a month, but this does not distinguish between pools, and any fraction of T incorporated chemically into tissue would not be expected to flush with the extra- or intracellular waters. Because of the low mean residence time, conventional wisdom holds that a small one-time T exposure is of relatively little concern: this reasoning, however, would not remain valid in the case of chronic exposure. Nor would the reasoning remain valid in situations involves substantial cell synthetic activity (such as embryogenesis), when the likelihood of producing T-labelled tissue is increased. Experiments, in fact, have demonstrated genetic damage in animal populations fed with constant low doses of THO and animal models indicate special vulnerability to higher doses earlier in life. Such effects are radiological in nature and occur at doses orders of magnitude below "the 50% saturation by body weight with THO" level needed to observe immediate fatality, which is sometimes attributed to isotope effects.

Much T produced by power plants is simply released into ambient air or
water, largely because nobody knows how to control it easily. It thus becomes a chronic source to specific populations downwind or downstream. Perhaps as an external source, T would be of minor concern; however, as it is prudent to assume contact with free T or THO essentially implies ingestion, some of this released T becomes a source of internal emission. It is not immediately comparable to isotopes dissolved in the deep sea, far from most humans.

And I find your cheery little paean to tritium to be a bizarre response to the news, that the USA is once again making the stuff to keep its apocalyptic fusion bombs functional ...

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NNadir Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Jan-29-05 08:03 PM
Response to Reply #3
4. Um, sounds cute, but nobody on earth has as much tritium as they
Edited on Sat Jan-29-05 08:32 PM by NNadir
do potassium-40. Potassium-40 has a decay energy of 1.505 million electron volts whereas tritium has a decay energy of 19 thousand electron volts. Assuming one can work with decimals this means that the decay energy of potassium-40 is 1.505-0.019 MeV = 1.486 million electron volts more energetic than that of tritium. Since there are, as I've indicated above, 500 billion curies of potassium-40 in the seas alone (and this is ignoring crustal rock, bananas and potassium supplements in health food stores) I think that reasonable people should be able to make some assessment about the importance of this tritium risk, which, to a sensible person at least, is a close to zero as you can get without actually being zero. This is at least true in comparison with the normal state of affairs on the planet for the past 4 billion or so years.

The fact is, as the above calculations here and my earlier post show show, tritium is nowhere on the planet a serious health risk as naturally occurring potassium. (It is my somewhat exotic opinion that calculations are always more important than specious and misleading statements like ones that pretend in defiance of reality that all internal beta emmission is somehow a function of nuclear weapons plants.) Therefore if one were being so incredibly neurotic as to worrying about "internal radiation" one would be far better served to lay out all the potassium ions (especially because there are so many of them) in one's blood in neat little rows on the shag carpet and pick through them with a set of very, very, very, very tiny zircon encrusted tweezers rather than to work one's self up into a state of panic about tritium that might leak out of Savannah River.

One would need to understand something about radiation to get this point, but understanding radiation is not widely accomplished on this planet. What is even more disturbing about the abysmal ignorance that characterizes statements generally made about the alleged dangers of radioactivity is the accompanying pseudoscientific mumbo-jumbo that is more remarkable for what it misses than for what it explains.

For the record, I am second to no one in my abhorrence of nuclear weapons, but I am quite sure that civilized nations inhabited by well educated and clear thinking individuals will have the capacity to produce tritium and besides that have lots and lots and lots of nuclear power plants that serve other purposes than tritium production. In fact, as I've shown here in many, many posts that the ONLY and I do mean ONLY path to nuclear disarmament is the controlled fission of highly isotopically purified actinides.

As to what is and is not bizarre, well, I think I'll leave that one alone.
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struggle4progress Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Jan-29-05 08:46 PM
Response to Reply #4
5. Reasonable people, who want to quantify ...
Edited on Sat Jan-29-05 09:28 PM by struggle4progress
... the relative risks posed by natural K40 (about which we can do essentially nothing) and anthropogenic H3, might do more meaningful calculations than you propose.

The halflife of K40 is of the order 10^9 year, that of H3 only about 10^1 year. Assuming, for simplicity, stationary concentrations of both isotopes, you'll find, over a typical human lifetime (say 10^2 year), only a negligible fraction of the K40 decaying, and a large fraction of the H3 decaying.
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NNadir Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Jan-29-05 09:55 PM
Response to Reply #5
6. Look up what a "curie" is.
Edited on Sat Jan-29-05 10:49 PM by NNadir
A curie is 3.7 X 10^10 Beq. One Bequerel is one nuclear decay.

This means that 500 billion curies of potassium-40 is 5 X 3.7 X 10^10 X 10^11 = 1.8 X 10^22 Beq or 1.8 X 10^22 decays per second. That there are this many decays is not a function of the half-life of potassium-40, which while not irrelevant to the question hardly tells the whole story, but is more a function of the vast amounts of potassium-40 on the planet.

Now if I were giving a student a quiz and I wanted him to demonstrate a modicum of understanding of radioactivity, for say, an introductory physics course, I might ask him or her to demonstrate that he or she understood the radioactive decay law (dN = -kN dt) by demonstrating that that the more radioactive material one has the more decays he or she will see.

I might phrase a quiz like this: Let us assume that the 437 nuclear commercial powerplants operating on the planet each have 1 kilogram of tritium in them. (The best students would immediately understand that is an absurdly high number given the low neutron capture cross section of deuterium and the low levels of ternary fission resulting a tritium discharge fragment. Powerplants typically have at most a few grams of tritium, if that.)

What, under these circumstances would be the total radioactivity associated with the decay of tritium (half-life 12.26 years) in Beq and in curies?

Then I might add this statement:

The ocean contains 6.6 X 10^20 grams of potassium. Of this 0.0117% is radioactive potassium-40. Given that the half-life of potassium-40 is 1.28 billion years, what is the total activity associated with the potassium-40 found in the ocean?

Then I might ask this question:

What is the ratio of the activity of tritium in 437 nuclear power plants each with one kilo of tritium in them to the activity associated with potassium-40 in the ocean?

(The answer to this last question would require, of course, an ability to answer the first two questions, which in turn would assume an ability to understand that the number of decaying nuclei is of equal importance as the half-life.)

Before a student could read my post #2 above and understand it and what it says, he or she would be probably need to be able to get 100% on this quiz. If however one did not understand radioactivity, and was not able to come to do the calculations that such a quiz would require, he or she would be might have difficulty reading my post #2 above and drawing useful conclusions about what it says. Of course, I cannot give quizzes on DU before making my posts. I am already arrogant enough without trying that particular bit of obnoxiousness.

I put my posts there for people who either have the capability of reading and understanding what they say, or, who have the time to read the links provided to teach themselves how to do the interpret my remarks. Some people have told me they find my remarks useful and others tell me frankly and honestly that they have no clue about what I am saying. A third class of persons demonstrate that they have no clue about what I am saying while insisting that they do understand what I say.

Like everyone else on DU, I am doing the best I can. I have, of course, a very distinct case on the relative risks of energy decisions and frequently I am frustrated by my poor ability to explain what I know in simpler terms than those in which I think and learn. While the third class of readers described above frustrate me even more than my own failings do, one must often deal in public discourse with clueless people who attempt to carry unjustifiable authority. (This for instance, accounts for the person occupying the White House.) Still the purpose of public discourse is not to attempt to educate those who cannot be educated or refuse to be educated, but to effect intercourse with those on such a level as to teach and to be taught, i.e. to engage in a mutual exchange that might help people to develop and disseminate a broad understanding of how we might best respond to the very real crisis we face.
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hunter Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Jan-29-05 10:44 PM
Response to Reply #3
7. Hydrogenated vegetable oils kill more people than tritium...
That stuff is totally unatural, but man, it's in everything. I try not to eat it, but avoiding it is not easy.

Yes, tritium is used in nuclear weapons, sort of the same way that "primer" is used in bullets. Tritium is also used in glow-in-the dark EXIT signs, and stuff like that. It's not terribly dangerous stuff compared to a lot of other stuff most of us commonly use in our daily lives.

Think of it this way -- if you get gasoline on your hands at self-service gas station, there is a small possibility that you will die because of that. A very small, but real possibility...

The first thing to recognize is that we are not going to stop the manufacture or maintainence of existing nuclear weapons by banning tritium production.

Many of the powerful people who are running this world would feel utterly naked without their nuclear bombs. They would secretly make tritium if they had to. They would import it from enemies such as Iran and North Korea if they had to.

In my opinion it is better to have a domestic tritium production program running more or less in the open, than a more dangerous covert tritium production program.

I make no apologies for tritium, it is bad stuff. But there is a whole lot of crap in my world that is much worse.
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Massacure Donating Member (1000+ posts) Send PM | Profile | Ignore Sat Jan-29-05 05:00 PM
Response to Original message
2. Scratch this post.
Edited on Sat Jan-29-05 05:02 PM by Massacure
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