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NNadir Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-02-09 11:05 PM
Original message
Prospects for increasing our complement of nuclear chemists are improving.
I am very clear in stating that every single anti-nuke I encounter relies wholly and totally on ignorance to make his, her, or it's case.

For a long time, entrenched and agressively promoted nuclear ignorance has been causing great damage to the future prospects of humanity. In part this is a result of the difficulty associated with understanding nuclear science - 100% of nuclear energy's critics that I encounter are lazy little bourgeois brats who have never bothered to open a science book in their pathetic lives.

But look, the future will not belong to these old tired dogmatic farts - if there is to be a future - and that's why I'm pleased to see an entire symposium at the upcoming American Chemical Society meeting in Washington D.C. to nuclear education.

http://oasys2.confex.com/acs/238nm/techprogram /

The program:

Sponsored by: NUCL
Cosponsored by: CHED
Organizer: Jeff C. Bryan
1:30 PM 161 Academic and national laboratory collaborations for teaching nuclear materials chemistry
Peter K. Dorhout
2:00 PM 162 Introducing nuclear chemistry at the University of Wisconsin-La Crosse
Jeff C. Bryan
2:30 PM 163 Teaching nuclear chemistry: A unique adventure in chemical education trying to build an island of stability
Donald R. Neu
3:00 PM 164 Uranium to electricity: The chemistry of the nuclear fuel cycle
Frank Settle
3:30 PM Intermission

3:50 PM 165 Teaching nuclear chemistry at Washington University
Demetrios G. Sarantites
4:20 PM 166 Radiochemical experiments using exempt quantities of radioisotopes
Dale D. Ensor
4:50 PM 167 Nuclear chemistry education at SUNY Albany
Thomas M Semkow

There will also be sections on fuel cycles, and graduate seminars, including one that really looks cool on radiolytic conversion in the a solid/liquid phase matrix of insoluble silver oxide into even more insoluble silver iodide under radiolytic conditions.

Ignorance is tough to defeat and is entrenched, but education is the best way to defeat ignorance.
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NYC_SKP Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-02-09 11:12 PM
Response to Original message
1. Speaking of education
Forwarded to me by a high school teacher.
Can you say whether or not the exercise below is a reasonable representation of fission?
The sum of the masses is less after the reaction.

~~~~~~~~~~~~~~~~~

235U + n → 92Kr + 141Ba + 2n (+Energy)

Calculate the masses of uranium-235, krypton-92, and barium-141. The mass of a neutron is 1.00866 amu (atomic mass units).

Mass of U-235= __________

Mass of Kr-92= __________

Mass of Ba-141= __________

Now add up the masses on both sides of the equation:

Left side Right side

U-235 ________ Kr-92 _________

+ n ________ + Ba-141 _________

+ 2n _________

Total=________ Total= __________

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thanks in advance.
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MannyGoldstein Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-02-09 11:17 PM
Response to Reply #1
2. Don't Know The Exact Science, But The Concept is Correct
Nuclear fusion (and fission) operate by inducing reactions that lose mass. The "lost" mass is converted into energy, but even a tiny loss of mass is a HUGE chunk of energy, thanks to E=MC^2.
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NNadir Donating Member (1000+ posts) Send PM | Profile | Ignore Sun Aug-02-09 11:46 PM
Response to Reply #1
3. You are missing a nucleon.
On the right side you have 235 + 1 = 236; on the left you have 141 + 92 + 2 = 235.

So no, the reaction is not reasonable.

You may correct it by changing the mass number of either fission product or adding another neutron. (Neutrons are released in various permutations, but typically average between 2 and 3. Your reaction would be correct were it U-235 + 1 n -> Ba-141 + Kr-92 + 3 n.

The mass numbers of each isotope can be found in the table of nuclides: http://atom.kaeri.re.kr /

This table shows all known nuclides, and you may click on various parts of it to find the isotopes in question and their masses. By noting the difference in the sum of the masses on the right and left side, you will find the mass defect of the reaction and be able to calculate from the familiar Einstein relationship E = dm c2 the amount of energy released. (dm is the change in mass for a mole of atoms undergoing this reaction.

Actually, the reaction you have given will quickly result in three fast nuclear decays, to La-141 then to Ce-141 and then Pr-141, the latter being stable, releasing even more energy. The longest lived nucleon in this series is Ce-141, which has a half-life of 30.501 days. (Ba-141 forms in about 5.94% of fissions in U-235.)

The situation with Kr-92 is even faster. The series is Kr-92 -> Rb-92 -> Sr-92 -> Y-92 -> Zr-92, the latter being stable. The longest lived isotope in this series is Y-92, which has a half-life of 3.54 hours.

So you may wish, to find the total energy released, choose to find the mass defect for Zr-92 + Pr-141 and assume about 1 MeV for each neutron which will be released as heat, and ignoring the effects of any captured neutrons.

The reaction I have postulated above releases no long lived radioactive species.



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NYC_SKP Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-03-09 12:25 AM
Response to Reply #3
4. Thanks, I thought that it might need to be 3n.
And I gather that the mass deficit is < 1, a fraction of that of a nucleon, right?

I'll have to use the chart that you linked (thank you) to get the exact figures and do the math.

:thumbsup:
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bananas Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-03-09 01:27 AM
Response to Reply #4
5. Yeah, the energy released is from the energy binding the nucleus together
and it's small compared to the mass of a neutron.

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NNadir Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-03-09 07:15 PM
Response to Reply #4
8. The mass of a mole of neutrons, roughly 1 gram, is the energy equivalent
Edited on Mon Aug-03-09 07:21 PM by NNadir
of 90 trillion joules or the equivalent - in familiar terms - of about 700,000 gallons of gasoline.

In nuclear terms, the mass of a neutron is equivalent to about 940 MeV. A typical fission event is about 200 MeV per fission (involving much larger masses since a uranium-235 nucleus is roughly 235 as massive as a neutron), of which about 190 MeV may be considered recoverable as heat that is convertible to exergy, with 10 MeV being neutrinos and high energy gamma rays that are not recoverable. (One could argue about gamma rays, but not neutrinos). So yes, a fission consumes less than the mass of a neutron as mass.

Free neutrons have a short half life, and unless they are captured in a nucleus, will quickly decay to give protons. As a practical matter, neutrons are seldom around long enough to decay. A "fast" neutron at 1 MeV is traveling about 13 km/sec, but they go only a very short distance before colliding with a nucleus. The mean free path of a neutron in matter is a function the composition of the matter and, oddly enough, the speed of the neutron.

In the table of nuclides, this sort of thing is described as a "cross section" and there are many different types of "cross section" (whimsically measured the unit "barns" which is a function of the apparent cross sectional area of a nucleus's silouette.) Types of cross section are scattering, capture, fission, and specific cross sections for esoteric types of nuclear reactions.
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bananas Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-03-09 08:19 PM
Response to Reply #4
9. How long has this person been teaching high school chemistry?
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HamdenRice Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-03-09 07:12 AM
Response to Original message
6. Unfathomable stupidity
"100% of nuclear energy's critics that I encounter are lazy little bourgeois brats"

You automatically discredit yourself every time.
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Name removed Donating Member (0 posts) Send PM | Profile | Ignore Mon Aug-03-09 06:49 PM
Response to Reply #6
7. Deleted message
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