Saturday, December 27, 2008

T6 Wedge fracture

What is a T6 wedge fracture?

The doctor's "education materials":

You have a compression fracture of one of the bones in your spine. This fracture occurs after minor injury (falling to the ground) in older persons with osteoporosis (thinning of the bones). It may also occur in young healthy persons after a severe trauma (car accident or fall from a height). This is a stable fracture and does not cause any injury to the spinal cord or nerves. This injury will take 4-6 weeks to heal and can be treated at home with bed rest and pain medicine.

In other words, a broken back. Linky, linky, linky...

This, my friends, is what happened to my DW this morning while sledding with our son.

There is this new, manufactured hill in town where the city has been doing construction to widen the roads, add a walk- and bike-path, and make it easier to cross town. We had driven past a few times and seen dozens of people out having fun. G has been asking if we could go. For Christmas, G received a sled on runners from his grandfather (GL); it was GL's when he was a boy. So, this morning, we decided to go and try out the hill with the "new" sled and a plastic sled we had purchased a week or so ago. We arrived and a big highway sign said, "No Parking, NOT a snowplay area." Yeah, right. Everyone was playing in the snow. Obviously this was a snowplay area.

So, we found a suitably steep slope, put G on the runners sled, and sent him off. He went all the way down, across the basin, and back up the other hill a bit. What fun! I came after him on the plastic sled. It was fast, and hard. I managed not to hurt myself. DW went next and she bounced along the slope. When we were all back at the top, DW said that we should find a more shallow slope. We did, G went down, and had fun. I went down, had fun. We came back up and went down again. G got tangled in his sled, hurt his knee a touch, but was fine. I went down on my stomache, without a sled. Slow, and fine. DW went next on the plastic sled, hit a jump (not purposely) at the bottom of the hill, and took flight. She landed on her back, compressing her T6 vertebra (not that we knew that at the time). A man nearby said he had probably broken a rib yesterday on this slope (but he was out again...). We went back up, G went down again, and then DW asked us to take her home. After some prodding by me, we went to the urgent care, and then to the ER (because UC doesn't do back x-rays). After a few hours at ER (very little wait in the lobby---we were triaged through pretty quickly), we got the above education.

The ER apparently receives about 22 sledding accident cases per day in winter. There were at least three sledding cases in there with us, one person was so bad off that he couldn't walk.

Apparently, the best way to go sledding is on your stomach, head first (with a bicycle helmet). Don't go on your bottom because you are very likely to get this kind of compression fracture in your back.

So, now DW is on hydrocodone, a mild, narcotic, semi-synthetic opiate. So, apparently she's a user. We're all keeping an eye on her. At least any cough she may have had will be relieved.

I don't have a scanner, so I can't show you her x-ray, but here are some good examples.

Be careful out there.

Next time, barring any other sudden cases of education, we'll be examining the potential dangers of nuclear energy w.r.t. accidents or sabotage.

Wednesday, December 24, 2008

Cons to nuclear power, part deux

So, I discussed waste and cost in the previous post. In this post I'll discuss proliferation.

3) Proliferation.
This basic argument against developing new nuclear energy technologies or power plants is based on the idea that somehow this nuclear technology can be used by rogues to develop nuclear weapons. The basic information on how to enrich uranium is already out there. I just discussed it in my previous posts. Gas diffusion is not difficult to accomplish. Centrifuge diffusion is not difficult to accomplish. Sure, it's expensive, but anyone who wants to and has the money can do it. So, why is the state department afraid of proliferation?

A) Nuclear enrichment abused; Iran as an example: Iran is a signatory of the Nuclear non-Proliferation Treaty (NPT), which basically says that only the P-5 (US, Russia, UK, France, and China), who have declared that they are nuclear weapons states, may produce or stockpile nuclear weapons. All signatories commit to collaborate on developing peaceful uses of nuclear energy. Iran is an NPT signatory. Russia has been helping Iran with nuclear fuel technologies, including enrichment. So far, that's all kosher according to the NPT... Enriching past the nuclear fuel to nuclear weapons grade uranium or plutonium basically just requires more diffusion cycles and more energy. Iran has more than enough oil and natural gas reserves to supply itself with energy for many many decades. Thus, the US is concerned that Iran is using the Russian technologies to build nuclear weapons rather than nuclear fuel. Considering Iran's wacked stance on some things, it's a valid concern, IMO.

Note that India and Pakistan, both of whom have had nuclear weapons since 1998 are not NPT signatories. North Korea is a signatory, as is South Africa.

So, we have several rogues who have or want to have nuclear weapons technologies. What does this have to do with nuclear power generation (specifically in the US)? Well, IMO, it has nothing to do with it. You cannot stop knowledge from proliferating. Just because Iran may be working toward having "The Bomb" doesn't mean we should necessarily hobble ourselves w.r.t. energy generation. Once a person or state has the knowledge of enrichment, they can go as far as they desire (and can afford) with that enrichment, so the only way we can stop them is to either destroy them or convince them it's not in their self-interest to build a bomb. The former isn't a reasoned option, so what can our state deptartment do to stop Iran from building a bomb? I dunno; I'm just a scientist, not a statesman, but I suspect our current path hasn't been working so well.

B) Redirection of already enriched nuclear fuel: This is theft or direct purchase of enriched fuel by a state or sub-state or group of wackos. Obviously the more states that have nuclear enrichment capabilities, the more opportunities to acquire enriched fuel that can then be made weapons-grade relatively easily. MIT estimates that there is enough enriched plutonium, produced from nuclear energy fuel generation, in Europe, Russia, and Japan to produce about 25,000 nuclear weapons, assuming 8kg/weapon. Obviously, only a few weapons are needed to greatly destabalize any given region.

Proliferation summary:
The means (knowledge and technology) of acquiring a nuclear weapon (via advanced enrichment) is not something we can easily control (see North Korea and Iran). The motive to acquire and use a nuclear weapon is something we (the US in particular) have not recently been very good at mitigating (see Iran). The opportunity to acquire a nuclear weapon or the fuel needed to make one is something we (the US) can stop within our borders and sphere of influence relatively easily. Stopping theft or purchase of Russian (for example) nuclear technology or fuel is not something we seem to have any hand in. The NPT has been fairly effective, but it only takes one state to feel threatened by another before it'll do what it feels it has to...

So, the expansion of today's nuclear power plants to non-nuclear (powered but not weaponed) states does pose some risks. Obviously the detonation of a nuclear weapon anywhere is cause for concern, and would likely be answered with a nuclear weapon. The cascade of responses could go all the way to WWIII. I do not know. I do not think it would take a nuclear weapon to start another world war, but I suspect the use of one would probably guarantee another large, if not world-wide war. This is obviously undesireable.

So, how can we mitigate the risks of nuclear weapons proliferation while still expanding nuclear power generation (or is it even possible)?

For one, the current fuel cycle is a pathway to weapons technology. There are other fuel cycles that do not lead to enriched, weapons-grade plutonium or uranium. These are not in wide-spread use, but they can be developed more aggressively and then spread to those countries that are looking to move to nuclear energy technologies.

For another, diffusing many of the tensions throughout the world is probably a good idea, regardless of the state of nuclear power proliferation. We do not need nuclear weapons to kill a lot of people...

Anyone who wants to can work out how to build a basic reactor. Such things are not difficult to do. The difficulty lies in ensuring that people don't want to move on to nuclear weapons...

I promised to say something about downblending in this topic's post. Downblending is the process of mixing weapons-grade and weapons-usable enriched fuels with depleted fuels to decrease the concentration of the fissible materials, in the process making nuclear power-grade fuels. This is a "new" way of more safely decreasing nuclear weapons stockpiles. In some ways this decreases proliferation risks by decreasing the ready availability of weapons-usable HEU that can be used in crude weapons, which can be made by relatively poor countries or groups (crude being similar in destructive scale to those used in WWII...).

Anyway, proliferation is a concern, but... The knowledge necessary for enriching materials to weapons-usable or weapons-grade form is easily obtainable, the technology isn't much more difficult to obtain, there is no need for nuclear weapons to kill many people or destabilize a region, and decreasing the desire to kill many people seems (to me) to be a more prudent approach than attempting to retroactively close Pandora's Box...

Saturday, December 20, 2008

Cons to nuclear power

Okay. I'm a month or so late... So shoot me.

Why should we NOT increase our use of nuclear power?

There are a number of arguments against nuclear power. The list below is not in any particular order.

1) cost
2) waste
3) proliferation
4) accidents or sabatoge

1) Cost: This is---at best---an inane argument, IMO. We can spend the money now on new technologies or we can spend the money later on health care, global warming mitigation, etc. Saying "it's too expensive to build or develop new nuclear power plants," is just whining. Yes, I am perfectly happy to be dismissive of and condescending to anyone arguing against nuclear power on the basis of cost.

2) Waste: This is the best argument (IMO, of course) against nuclear power.

2A) To get the uranium ore, we must mine for it. This creates long-lived contamination around the mining site. The uranium tailings contain over a dozen radioactive species, including thorium-230, radium-226, radon-222, and polonium-210. These are all hazardous materials, of course. If, as in past practices, the radioactive sand is left on the surface, it could be blown about by the wind, washed away by rains, etc. There is not actually a high concentration (compared with other nuclear waste materials) of hazardous materials by mass, but there will always be a large mass of tailings from any given mine. The most serious and probable human health hazard associated with the tailings is lung cancer caused by inhaling these radioactive products.

Anti-arguments: Here's the thing, though... The most dangerous, common rock, in terms of radioactivity, is granite. Your granite tabletop (if you're so lucky) is continuously producing radon gas. It's not much, and it's certainly not a health concern. Your drywall plaster is probably made of calcined gypsum. That's releasing more ionizing radiation than your granite counter top, and it's in every room of your house. It's still not a health concern. All the portland cement you see and use (home foundations, sidewalks, some freeways, buildings, etc., etc., etc.) are emitting as much or more radon as fly ash from coal-fired power plants. The uranium tailings from old mines are certainly dangerous, but new techniques in dealing with the tailings are in place, and even better ones are being developed. That's a pretty hand-wavy argument that the waste from mining is "safe." It's not safe. Neither is burning coal. Here is a paper that argues that the radiation dosage from mine tailings isn't terribly dangerous. That's only one side of the story, of course. This paper estimates the dosage someone living around a coal-fired plant will be exposed to. This paper discusses the comparison between coal and portland cement sources of radon. We see more cancers from pollution and cement-derived radon in our homes than we do from mine tailings, and increased nuclear power generation will only decrease the overall number of cancers, even if we continued to use the worst methods of dealing with uranium tailings.

2B) To get fissionable material (U235) from the uranium ore (uranium oxide, "yellow cake"), it must go through enrichment. (Stolen from here): Natural uranium is composed of 0.72% U-235 (the fissionable isotope), 99.27% U-238, and a trace quantity 0.0055% U-234 . The 0.72% U-235 is not sufficient to produce a self-sustaining critical chain reaction in U.S. style light-water reactors, although it is used in Canadian CANDU reactors. For light-water reactors, the fuel must be enriched to 2.5-3.5% U-235. Uranium is found as uranium oxide which when purified has a rich yellow color and is called "yellowcake". After reduction, the uranium must go through an isotope enrichment process. Even with the necessity of enrichment, it still takes only about 3 kg of natural uranium to supply the energy needs of one American for a year.

The byproducts of enrichment are basically depleted uranium (DU, which is pretty much just U238) and uranium hexafluoride gas (UF6). U238 is relatively safe, with a half-life of about 4.5 billion years, via the path of alpha decay. Alpha particles are just helium nuclei. They can be dangerous when ingested or inhaled, but are pretty much harmless externally (alpha particles are stopped by a single layer of dead skin cells). That's not to say that alpha decay is harmless. Radon gas, polonium 210, etc. are implicated in cancers and other nasty deaths if inhaled (Pu210 is thought to have been the material used to poison Alexander Litvinenko). U238 is also chemically toxic, and can have seriously bad effects on the liver, once again if ingested. U238 is now being used in a process called "downblending." I'll discuss downblending in the proliferation discussion. UF6 is a different beast altogether. UF6 is an extremely unstable waste compound that's not easy to store or handle. Here you can find a 118 page PDF on safe handling procedures for UF6. I haven't read it. Let it suffice to say that UF6 is mostly bad because of its chemical (not nuclear) toxicity. The uranium part of UF6 is obviously radioactive. The depleted UF6 (with mostly U238, not U235) is stored as waste. Any amount of water mixed with UF6 will turn it into a rather nasty acid, so the storage of UF6 is a difficult task.

I cannot argue against the dangers of depleted UF6... It is as dangerous as any other toxic chemical used in other manufacturing processes. Since it also contains U238, it's scary to a lot of people. I'm not any more concerned about UF6 than any other toxic chemical (melamine?) that is moved around this country and others.

2A and 2B are the wastes from the processing and creation of nuclear fuel. There are wastes that come out the back end of the nuclear power generation process.

2C) Spent fuel rods contain fisson products that emit beta and gamma particles. They also contain actinides that emit alpha particles. These products include uranium-234, neptunium-237, plutonium-238 and americium-241, and even sometimes some neutron emitters such as californium (Cf). None of these are pleasant products. Some are so radioactively hot that they're thermally hot.

Many countries, the US excluded, reprocess these products to extract any left-over U235 for re-use as a nuclear fuel. This increases the concentration of the radioactive products in the waste. It also increases the concentration of the toxic chemicals used to process the materials. The US just stores the waste as-is, without reprocessing. One can argue either way about what to do with these products. Since we're in the US, I'll briefly mention Yucca Mountain.

Some geologists have certified that Yucca Mountain would be a safe place to store these waste products. Others have argued that it is not safe. I'm not sure who is correct. I'm not sure how dangerous these products are in the long term. I am sure that if we were to spend some money paying scientists and engineers, they could figure out a workable solution. It would not be ideal, it would not please everyone.

So, waste is the biggie. It's not solved, but it's not nearly as bad as many people think.

I think this post is long enough for now. I'll post arguments 3 and 4 later...