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a traveler at a velocity 0.9 times the speed of light will make the trip in only a few years

A speck of paint put a nearly quarter inch wide pit in the window of the space shuttle.

http://www.space.com/spacewatch/space_junk.html

Bear in mind as the article mentions orbital velocities are as slow as 17,500 mph. The speed of light is approx. 670,000,000 mph.

http://en.wikipedia.org/wiki/Speed_of_light

If you're going at 0.9c, hitting anything the size of a golf is going to end your trip real quick!

A golf ball has the mass of about 0.046kg.

http://hypertextbook.com/facts/1999/ImranArif.shtml

At 0.9c it would have about 5.4*10^15 J of KE.

http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/releng.html

In contrast, a 20 kiloton fission bomb has about 8.4*10^13 J.

http://www.chemcases.com/nuclear/nc-09.htm

Another way to look at it is this... you're not going towards Alpha Centauri at 0.9c ... Alpha Centauri is coming towards you at 0.9c.

Granted the space between here and Alpha Centauri is mostly empty, but what are the chances of hitting anything within a couple of orders of magnitude of the mass of a golf ball b/w here and Alpha Centauri? Even hitting something 1/100 its mass at that speed is going to be like a small nuke going off.

Yes, Iraq did have a nuclear program, back in the 1970s and 1980s. It didn't go well. They couldn't get any of the separation processes to work. A mid-level physicist in the program defected to the US and wrote a book about it, which gives a view of the strange world of working for Saddam Hussein. If he was annoyed at a manager, he sent them to a torture camp to be tortured for a while, then put them back to work. If they did well, he gave them one of his ex-mistresses.

Iraq tried to build calutrons, which do isotope separation in one or two steps but can process only tiny amounts of material. So it's necessary to build a large number of them to enrich enough uranium for a weapon. The US built some sizable calutron plants during WWII, but they were too slow to be useful when fed with natural uranium. They were used as a final upgrade step for uranium partially enriched in the gaseous diffusion plants. None of the other nuclear powers ever bothered much with calutrons, except little research-sized units. Iraq never actually built enough calutron capacity to accomplish much.

Iraq's yellowcake (uranium oxide, unenriched) is left over from that era. Extraction of yellowcake from raw ore is an ordinary chemical process, usually performed somewhere near the mine. It's the first and easiest step of the process, and that's as far as Iraq got.

Point three is called cracking. A quick google search finds some more information pretty quickly, and if you have disposable funds,
this or this seem like pretty good resources. There's also a Journal of Petroleum Geochemistry, if you're interested.

Lab re-creation is not really necessary; the commercial form of cracking is called petroleum refining.

I only thought it was weird that messing with the liver did it. I thought they did it all the time with certain types of leukemia with big doses of radiation, by killing off the patients existing immune system and then doing a bone marrow transplant. Maybe I misunderstood and they were using relatives to donate the bone marrow?

http://www.neurologyreviews.com/dec04/nr_dec04_bonemarrow.html
http://www.chemcases.com/cisplat/cisplat20.htm

That 48 tons of waste per plant per year could be greatly reduced with spent fuel reprocessing. Most other nuclear nations, including the UK and France, go this route, which is a lot more sensible than just burying everything, however due to some really boneheaded decisions made by President Carter, it's never been done recently in the United States.

Until it was banned, we had a whole system under construction for reprocessing spent fuel that would have reduced the scope of the problem we're now faced with. However, in 1977 the research was cut off, and further development and implementation was banned; although President Reagan quietly reversed the ban, nobody has been willing to put money into it. Except of course the military, their ability to manufacture plutonium for weapons purposes was never affected, something which strikes me as endlessly ironic, given that Carter's justification for banning reprocessing was ostensibly to prevent the spread of nuclear weapons.

By processing the spent fuel assemblies promptly (before they sit around and create a lot of secondary contamination) you reduce the volume of waste that has to be stored for long periods, and you also get a non-trivial amount of new fuel back (even out of reactors that aren't specifically designed to breed new fuel). Either one of those goals would make the procedure worthwhile in my opinion, pick your favorite and count the other one as a bonus. Right now we're burying tons of waste which isn't itself that radioactive or long-lived or even toxic, but because it's physically joined to stuff that is. The actual volume of long-lived high-level waste produced by a plant isn't that much, if you do the right reprocessing first.

The plan in the United States was a process called PUREX; you can Google it for more information. The French do their reprocessing at COGMA LaHague, and the Brits do it at a commercial facility called THORP.

More information here as well:
http://chemcases.com/nuclear/nc-13.htm

Also, there is of course, the initial radiation expsosure while they're installing the shields. And lets hope those water bags dont leak, too.

You don't have to worry about the water bags ... they will be made by Dow Corning.

This is not the great wonder that it appears to be on it's surface. This product, ethanol, has proven to be a very hazardous when combusted. The byproduct of burning or combusting ethanol dissolves very easily in water, but leaves the carcinogens intact. Read the official report on what is is doing and has already done to our environment here at ChemCases,. The following is a link to an article on CBS News last month the makes that connection between Ethanol and MTBE and pollution; This is serious stuff and making this very harmful fuel even cheaper ought to have us very worried. Where are the articles on how to solve this problem, there aren't any because a solution doesn't exist yet.

> Also, the higher temperatures will form more carbon monoxide vs dioxide ratios than normal

Carbon compounds are not much of a problem, since there's no carbon involved! I don't think any carbon dioxide from the ambient air would get converted to carbon monoxide, and there's no other source of carbon.

Meanwhile, there are ways of dealing with the nitrogen problem. The promotional materials for this hydrogen scooter don't specify if they use a catalytic converter, which dramatically reduces the emission of nitrogen compounds. A good converter would probably do the trick.

- Peter

Evaculate all the people, detonate a neutron bomb at high altitude, move back in and operate normally. The spray of neutrons from such a bomb would make all the radioactive atoms decay on the spot.

I won't ask for people to check what they're writing for relevance... after all, I enjoy many of the comments I read here, but it is considered bad style to criticize the work of others without enough commonalities between the work and the critical remarks.