Nuclear Related Questions

Do you guys have any questions related to the Nuclear field?  I am a Nuclear Engineering student.

Originally posted by Zellot yo so what other color can that reactor make besides blue and how much power can that reactor put out

Unfortunately, the only color it can make is blue.  In the past, we use to be able to make the light flash really bright.

Our schools reactor is 1,000,000 Watts thermal.  Rather than producing electricity, we use free neutrons we create for research.

Civilian power reactors are literally hundreds of times more powerful than our school's.  They range from ~800 - 1,200 MW electric.

After the fuel is "burned" in the reactor, we will produce about a trashcan's worth or spent fuel.  This fuel, although looking the same, will remain unhealthily radioactive for many maybe 500 years or less.  Luckily, a few inches of lead shields us from essentially all of the spent fuel's radiation.

Yes, it does have a half life.  Dr. McCarthy, former professor at Stanford said this, "After 10 years, the fission products are 1,000 times less radioactive, and after 500 years, the fission products will be less radioactive than the uranium ore they are originally derived from."  We have to wait that long...

Although we have temporary storage on site, yes, the government, specifically Department of Energy, will haul off our spent fuel eventually.  We generate maybe a trashcan size every decade.  I think we refueled last in the late 90s or early 2000s.

Commercial nuclear power plants produce ~3 cubic meters of spent fuel each year.  If you were to stack all of the spent fuel ever generate by the US nuclear power industry, it would fit on a football field about 3 meters high!  So, yes, it is a big issue, but by no means unmanageable or vast.

The white suites are for the Plasma science lab and aren't related to the reactor program.  Touching stuff with tissues doesn't cut it there. haha

Although there are ways to separate the waste into components through "reprocessing," there is no way to make the long lived radioactive particles less radioactive.  Only time will do that.  "Reprocessing" the fuel reduces the volume of waste to be stored to about one tenth of it's original size.  While we currently do not reprocess fuel in the US, it doesn't "go bad" or anything.  We could always do it later.

We cannot use the fuel again, even after the radiation is essentially undetectable.

You've got the jist of a half-life.  A half-life is a length of time.  After that time has pa**ed, half of your sample has decayed away.  See the chart below.   Although the amount of radiation emitted drops off really fast, we have to wait until a sample decays to levels comparable to the ore it was made from to deem it "safe."

# of half-lives	1/1	100
1	1/2	50
2	1/4	25
3	1/8	12	.5
4	1/16	6	.25
5	1/32	3	.125

After the time it up, it's just like other trash.  The fuel is generally ceramic.

Several a few of concrete or many feet water will shield us from radiation.  We do use the lead bricks in select areas.  They are really heavy.

When we leave, we do have to screen ourselves.  We slide our hands and feet (most likely to pick up something) over detectors.  Fortunately, I've never set one off.  haha

I read somewhere that we would need to build about 10,000 more reactors to supply enough power for the world's consumption (when we run out of fossil fuels). But the problem with that is there's only approx. a 50 year supply of uranium ore. Are there any alternative nuclear fuel sources being studied? If not, we had better get cracking on solar power because that's the only source that's virtually limitless.

Originally posted by BAIN I read somewhere that we would need to build about 10,000 more reactors to supply enough power for the world's consumption (when we run out of fossil fuels). But the problem with that is there's only approx. a 50 year supply of uranium ore. Are there any alternative nuclear fuel sources being studied? If not, we had better get cracking on solar power because that's the only source that's virtually limitless.

In short,
We cannot provide enough electricity for for the world to run solely off of Nuclear fission from a rare isotope U235 (less than 1% of Uranium found) alone.  If nuclear is to rise suddenly to meet the demands of the world, we would have to use "fast reactors."  Currently, very few of these exist.

50 years is too conservative.  The lowest I've seen is 80.  By that time, the plasma science kids should have created a steady state fusion reactor like ITER that can produce electricity for the ma**es.  If you are looking at the 300+ year timeframe for emergy production, only Nuclear Fusion, Solar, Geothermal, Hydroelectric and Wind are esentially limitless.  Essencially, all of the energies we use, including those above, are some storage of nuclear fusion from the hearts of stars.  But, that is a different discussion.  haha.


In depth,

On a lot of nuke plants,
So, the US has 104 Nuclear Power Plants supplying ~25 of our nations electricity.  Replacing all of the fossil fuel plants would take ~300 new plants.  This inflates to ~420 new reactors, if we add an expected ~30% increase in electrical consumption by 2025.  To be practical, it is impossible for this to happen.  There are several key bottlenecks stopping rampant nuclear power plant construction, namely heavy forgings, that prevent us from simply whipping up as many power plants as we want.  Also, Florida Power and Light released what they were paying for a new reactor, at lease 6 billion per reactor.  The private power firms that operate these facilities only have the capital to build a small handful of plants a piece.

Fuel Projections,
Part 1,
In brief, our profs say we have ~80-120 years of Uranium left, based on current consumption, new plants operating, and expected finds of Uranium.  Now, it is important to know what we are talking about here.  Not all Uranium is created equal.  There are two major isotopes, a variation, of the Uranium atom that we are concerned about, U235 and U238.  While one is slightly heavier than the other, it also occurs much more frequently.  U239 is 99.3% of the ore we mine.   Unfortunately, current reactors need concentrations of the much lower concentration isotope U235, naturally occurring @ 0.7% of natural ore.  Through enrichment, they raise this up to 3-5% for commercial reactors. After this small percentage of the fuel is "burned" down to 1%, after 3 years, it is thrown away.  Destined to be separated from society for at lease 500 years.
Part 2,
There is a way to "burn" this much more prevalent isotope U238 by using a technology called fast reactors.  However, this technology, although feasible, is not as competitive as traditional "slow or moderated" designs.  If we were to switch to the fast reactor design, which would require new reactors - not just retrofitting our current fleet, we could use the ~80% of spent fuel or waste that is still the U238 isotope that was put in to start with. 
Fast reactors would greatly expand the amount of energy we could make from nuclear fission.  We could last for several hundred years off of fast reactors from U238, since they use an isotope that is greater than 99% of the ore we mine, and not less than 1% like the U235 we so desire.  Lastly, we are in no danger of running out of Uranium for our current fleet of reactors.  At most, we are looking at 60 years of reactor operation.  This is far below even the most conservative estimates.