Sites: GlobalSpec.com | GlobalSpec Electronics | CR4 | Electronics360
Login | Register
The Engineer's Place for News and Discussion®


Rockaholic Adventures

Rockaholic Adventures is the place for conversation and discussion about outdoor excursions. You'll also read reviews written from the perspective of today's technologically-advanced outdoorsman - one with a background in engineering and geology. Here, you'll find everything from discussions about geology-related engineering disasters to insights about how advances in technology have transformed modern-day extreme sports.

Rockaholic Adventures also covers topics such as urban planning and other anthro-induced changes to the access and preservation of natural areas. The blog's owner, Shawn, holds an A.S. from Hudson Valley Community College (HVCC) with a concentration in science and engineering, and a B.S. from the State University of New York (SUNY) at Albany with a major in geology.

Previous in Blog: The Catastrophe of the “Islands of the Dogs”   Next in Blog: The Missing Carbon Problem (Part 1)
Close

Comments Format:






Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







7 comments

Difficulties in Characterizing Uranium

Posted November 03, 2008 5:00 AM by Shawn

Uranium, a destructive-but-useful heavy radioactive element, can pose a tough challenge when characterized by analytical techniques. Uranium has three naturally occurring isotopes: U-238, U-235 and U-234. We almost never deal with pure isotopes, but rather identify uranium by the percentage of which isotopes are present. Naturally-occurring uranium is composed of 99.28% U-238, 0.71% U-235, and 0.0054% U-234. Enriched uranium, which is used for nuclear warheads and nuclear reactors, is enriched in U-235, the most radioactive isotope of uranium. Depleted uranium (DU) has a lower percentage of U-235 and higher levels of the most abundant and stable isotope, U-238. DU is used as a counterweight in aircraft and, because it combusts spontaneously on impact, in the military's heavy-armor piercing ammunition.

Now that we have identified the material, we can start to identify possible problems when doing analytical chemistry on samples containing uranium. The mass differential between the heavy isotopes is negligible, and most conventional analytical techniques are incapable of identifying uranium isotopes. These methods are only useful in identifying the element and not the percentage of which isotopes are present. Isotopic analysis is a fundamental requirement for several health studies as we need to prove the source of the uranium present. We can't prove that a party is responsible for a health problem unless we can tag their substance as present. In our discussion, the isotopic analysis will prove if it is a synthetic substance and what processing methods are likely to produce that material.

Knowing the limitation of your equipment is useful, but even identifying the abundance of the element in your sample can be complex. The heavy isotopes are decaying with a rather short half-life and are prone to forming complex inorganic molecules. Before you can analyze a sample, you must grind and dry it. In this state, health concerns become a risk because powdered samples are highly susceptible to forming aerosols, and inhalation of this known carcinogen could lead to fatal outcomes. After your sample has been ground to a fine dust and dried thoroughly, you still have the large complex molecules present. Several digestion steps to free up the organic and inorganic matter include the use of other caustic substances such as HF or nitric acids.

After digesting and preparing your samples, you can run your choice of instrumentation along with a few blanks and standards for increased confidence in your results. Ultimately, the complications facing the characterization of uranium lie with the difficult digestion steps, safety measures, and - in the case of isotopic analysis - the fine tuning of the instrument used to characterize samples.

Resources:

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

http://www.atsdr.cdc.gov/toxprofiles/phs150.html

http://www.ehjournal.net/content/4/1/17

Reply

Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru
United States - Member - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Jul 2008
Posts: 1163
Good Answers: 37
#1

Re: Difficulties in Characterizing Uranium

11/03/2008 4:25 PM

While chemistry gives me bad flashbacks of outliers on my report card, I do find this blog intriguing. But while that may be so, I would like to not have traces of uranium in my path! I find it would be just as much bad luck as crossing a black cat in an alleyway!

Reply
Power-User

Join Date: Apr 2005
Location: Averill Park, NY
Posts: 222
Good Answers: 4
#2
In reply to #1

Re: Difficulties in Characterizing Uranium

11/04/2008 12:57 PM

Lab work is definately not everyones cup of tea. Toxic chemicals, radioactive aerosols, field work that may include possible exposure and other health risks are abundant. Have you read about fume hoods and the influence someone can have on the airflow simply by walking at a face past a workstation?

__________________
"There isn't a scientific community. It's a culture. It is a very undisciplined organization." ~ Francois Rabelais
Reply
Guru
United States - Member - New Member Engineering Fields - Electrical Engineering - New Member

Join Date: Jul 2008
Posts: 1163
Good Answers: 37
#3
In reply to #2

Re: Difficulties in Characterizing Uranium

11/04/2008 1:07 PM

I have never heard of the dangers of a scientist briskly walking past fume hoods. It is funny because our high school redid the science rooms and added fume hoods for chemistry and such. The only difference is getting high schooler to even move to begin with is a daunting task! Are brisk walks now considered hazardous to our health?

Reply
Anonymous Poster
#4
In reply to #3

Re: Difficulties in Characterizing Uranium

11/07/2008 4:49 PM

It is a difference of perspective. Working chemists take much greater risks than most people in doing their jobs for less than almost any other normal person. There are always efforts to minimize the risk, though many of these are directed at minimizing public exposure, and exposure of the non-chemist workers. The chemists just accept the lower pay and health risk as part of doing the job. They buy into the idea that they understand the risk more than others would and therefore must be willing to take greater risks as part of their job properly.

A good example, when i was younger i worked at a haz waste facility in the lab as a chemist characterizing waste samples for recylcing or disposal. We dropped an unknown sample on the floor that was in the process of characterization. Every chemist in the building came to see the sample and discuss cleaning it up while we were cleaning it up. Everybody, including the secretaries and salesmen, in all the other building evacuated like we had a nuclear bomb fall in the lab, and the firemen , well they could not even get in the facility gate (they would have been absolutely no help anyways). There was the expectation amongst management standing way out in the parking lot that the chemists will clean everything up. FYI fume hood capacity to recover vapors is easily influenced by local air flows, they are there as much for the general public to keep opinion that the environment is safe for the workers, and unsafe for others, as they are for any real safety measure. It is just a good thing that acetone is pretty much non-toxic, though you do feel like taking an immediate nap sometimes just wherever you happening to be standing.

Reply
Guru

Join Date: Jul 2006
Location: "Dancing over the abyss."
Posts: 4900
Good Answers: 240
#5

Re: Difficulties in Characterizing Uranium

11/08/2008 7:06 PM

"Before you can analyze a sample, you must grind and dry it. In this state, health concerns become a risk because powdered samples are highly susceptible to forming aerosols, and inhalation of this known carcinogen could lead to fatal outcomes. After your sample has been ground to a fine dust and dried thoroughly, you still have the large complex molecules present. "

Glove boxes, baby. Glove boxes.

milo

__________________
People say between two opposed opinions the truth lies in the middle. Not at all! Between them lies the problem, what is unseeable,eternally active life, contemplated in repose. Goethe
Reply
Guru

Join Date: Sep 2006
Posts: 4545
Good Answers: 90
#6

Re: Difficulties in Characterizing Uranium

01/10/2009 8:33 PM

"Before you can analyze a sample, you must grind and dry it. In this state, health concerns become a risk because powdered samples are highly susceptible to forming aerosols, and inhalation of this known carcinogen could lead to fatal outcomes. After your sample has been ground to a fine dust and dried thoroughly, you still have the large complex molecules present. Several digestion steps to free up the organic and inorganic matter include the use of other caustic substances such as HF or nitric acids."

One thing to consider is that if your final sample contains substantial amounts of metallic uranium in the form of a "fine dust," you risk fire or explosion. Powdered U is pyrophoric and can ignite spontaneously in air. You should, furthermore, prepare your samples in an inert atmosphere because U oxides rapidly, even if it doesn't catch fire.

Reply
Guru

Join Date: Sep 2006
Posts: 4545
Good Answers: 90
#7

Re: Difficulties in Characterizing Uranium

01/10/2009 8:36 PM

Your assay techniques also do not include mass spectrometry which does reveal the proportions of isotopes present in a sample, uranium and otherwise.

Reply
Reply to Blog Entry 7 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Copy to Clipboard

Users who posted comments:

Anonymous Poster (1); Jaxy (2); Milo (1); Shawn (1); user-deleted-13 (2)

Previous in Blog: The Catastrophe of the “Islands of the Dogs”   Next in Blog: The Missing Carbon Problem (Part 1)
You might be interested in: Analytical and Chemical Standards, Analytical Laboratory Services, Environmental Testing and Analysis Services