Are there fissionable isotopes of any element with short-lived radioactive isotopes?

bananan

might be more expensive than uranium or plutonium, but storage costs and environmental impact and anti-nuke activism might be muted if there was an isotope of any element, say an isotope of iodine, that when fissioned, gives off energy AND short-lived radioactive isotopes.

so, say, hypothetically speaking, iodine captures a neutron from say plutonium, and becomes a radioactive isotope of iodine, which fissions into non-radiactive iron isotope and radioactive tritium isotope with a short half life.

the upfront cost of using iodine might be more expensive, but the overall cost might be less expensive.

Astronuc

Nothing below U-233 is readily fissionable by low to intermediate energy neutron absorption.

Pa-231 is fissile with thermal and epithermal neutrons, but has a very low cross-section < 1b, and more on the order of 1-100 mb. Th-232 is effectively fissionable with fast neutrons only, >1 MeV and higher.

http://oldserver.ba.infn.it/~ntof/pr.../TH_PROPv7.pdf

Pu-241 has a half-life of 14.290 y and is fissile. The isotope Americium-241 (which results from the 14-year half-life decay of Pu-241 which accumulates in reactor grade plutonium with increasing burnup) emits highly penetrating gamma rays, increasing the radioactive exposure of any personnel handling the material.

See Morbius's discussion of 'fissionable' vs 'fissile'.

Morbius

bananan,

First I'd like to address an issue of terminology.

The term you want to use above is not "fissionable" but "fissile".

"Fissile" means that the nuclide is fissioned by a neutron of ANY energy.

"Fissionable" means that the nuclide can be fissioned by a neutron, but only if it has
kinetic energy above a nuclide-dependent threshold.

For example, U-238 is actually "fissionable" because it will fission with fast neutrons
with energy in excess of about 1 MeV. However, U-238 can't be used as a reactor
fuel alone.

So allow me to rephrase your question into "are there any fissile isotopes of any
element....."

Consistent with Astronuc's reply above; for fissile isotopes, you have your choice of
U-233, U-235, or Pu-239.

Unfortunately, there's no nuclide that fits your criteria above that produces energy,
produces only short-lived daughters, is acceptable to the anti-nukes.... If there was,
then we'd be using it.

Dr. Gregory Greenman
Physicist

bananan

I understand from wiki that india is using Thorium as a supply fuel. Could there be a combination of Thorium, uranium and plutinion that when placed with spent radiactive fuel, might cause it to decay quicker?

Morbius

bananan,

In the "Thorium cycle", you use Th-232 as a fertile material to breed fissile U-233.

Then you burn the U-233 for power and make more U-233.

Putting combinations of different materials together doesn't affect the radioactivity.

The radioactive decay characteristics depend on what's going on in the nucleus.

The nucleus has no way of knowing what's also in the mix. In terms of length scale;
all those other materials are a LONG, LONG, LONG way away from the nucleus.

Dr. Gregory Greenman
Physicist

Astronuc

This might be helpful.

Some Physics of Uranium
http://www.uic.com.au/uicphys.htm

Thorium fuel was used in at least two reactors in the US - Shippingport and Indian Point 1. IIRC, the fuel did use U-235 dispersed in thoria.

bananan

THank you Dr. Greenman,

But those radiactive elements, which are the waste products and the objections of greenies, are they Fissionable (I hope I used the right term this time), in that if they are in the pressence of high-neutron flux, as a result of either uranium or plutonium, can either capture a neutron and transform into another element or split directly, into waste products with shorter decay?

Alternatively, would it be possible to combine a source of high neutron flux uranium or plutonium, with a lower atomic number material, say carbon-14, so that should carbon 14 capture a neutron, it gives off energy and decay or transform into something nonradioactive.

Thanks

Astronuc

Many fission products already decay rapidly. It's the longer living isotopes which present a problem, e.g. Cs-137 and Sr-90, but these decay with about about 29-30 year half-life.

http://www.nndc.bnl.gov/chart/ - one can select a section and zoom in on the appropriate radionuclide.

Any nucleus can be 'transmuted' into a new isotope by neutron capture, and that is one reason nuclear fuel has to be periodically removed from a reactor - the fission producst compete with the fissile material for neutrons - and isotopes of Xe and Kr build up causing pressurization of the fuel and swelling of the ceramic or metal matrix.

One idea has been to recover the U, Pu and other transuranics and burn those in a so-called actinide burner. This approach gets rid of some of the long-lived radionuclides and utilizes the thermal energy.

These might be of use - http://www.uic.com.au/nip.htm

Morbius

bananan,

There are two classes of materials in nuclear waste. One class is the "fission products";
these are the remnants of nuclear fuel that has fissioned. They are all fairly short-lived;
as Astronuc points out, the longest lived fission products are Sr-90 and Cs-137 which
have half-lives of 29 years and 30 years, respectively.

The other class of materials in nuclear waste, are the "transuranics" or "actinides".
These are the long lived wastes, and there are both "fissile" and "fissionable" nuclides
in this group. This group would include Pu-239, which is "fissile" and has a half-life
of about 24,000 years. You correctly surmise that the rest are "fissionable".

The way to get rid of these long-lived components of nuclear waste is to reprocess the
nuclear waste and recycle the long-lived components back to the reactors to be burned
as fuel, as you suggest above.

This was always the intention of the nuclear power program in the USA; to reprocess
spent fuel and recycle the long-lived waste components back to the reactor. The USA
was setup to do this in the early '70s, but the "greenies" went to court to block it;
claiming that there must be an environmental impact report before the USA could
authorize reprocessing.

So the AEC, and its successor ERDA, did an environmental impact statement called the
GESMO - Generic Environmental Statement for Mixed Oxide. [ When reprocessed
actinides are returned to the reactor as fuel, they are in oxide form, and mixed with
fresh uranium dioxide to form a fuel known as "mixed oxide" or "MOX". ]

Shortly thereafter, the "greenies" got Congress to OUTLAW the reprocessing and
recycling of nuclear waste in the USA!!!

One has to understand, the "greenies" evidently don't want a solution to the nuclear
waste problem. They want to shutdown nuclear power in the USA. That's why they
have opposed recycling nuclear waste. They have opposed Yucca Mountain.
They oppose power companies even shipping the waste out of the power plant.

The strategy of the "greenies" is to back-up the nuclear fuel cycle so that nuclear
power plants won't have any place to put spent fuel. If the power company doesn't
have any place to put spent fuel; then they can't unload their last core of spent fuel
and reload the reactor with fresh fuel. The nuclear power plant will have to shutdown;
and the "greenies" will have accomplished their purpose.

A solution to the nuclear waste "problem" is the LAST thing the "greenies" are interested in.

Nations like Great Britain, France, and Japan routinely reprocess and recycle spent
nuclear fuel in exactly the manner you suggest without the problem of obstruction by
the "greenies".

If ALL the electricity used by a family of four for 20 years were generated by
nuclear power; the accumulated nuclear waste due to that electricity generation would
fit in a shoebox if it was not reprocessed. If it was reprocessed, then the equivalent
amount of nuclear waste for the family of 4 for 20 years would fit in a pill bottle or
shot-glass.

Most of the volume and mass of nuclear waste [ >90%] is U-238; no more dangerous
or radioactive than the day it was dug out of the ground.

Dr. Gregory Greenman
Physicist

bananan

Dear Dr. Gregory Greenman,

I'm surprised that these facts are not usually presented on the nuclear debate. While I'm infavor of environmental issues, I think nuclear might be a good way to address global warming.

Is it possible to reprocess the radiactive long-lived waste, both fissile and fissionable, on-site? Greenies and after 911 are afraid of terrorists/accidents if it is done off site. Also, I understand U-238 can be bred into plutonium.

IMHO, improving an existing technology that exists now (fission) is better than the countless billions poured on a pipe dream (fusion). I've argued in other forums that if we invest in billions to recycle nuclear waste rather than nuclear fusion, then we can reduce CO2 emissions now, rather than wait another 100 years for fusion to become online (if it does at all).

I've read extensively on nuclear technology. I understand that pebble bed technology, while safe, is a once-through cycle that produces considerable waste. It was done experimentally at South Africa.

I am under the impression that long-lived nuclear waste disposal, in peaceful Western democracies, is the primary objection to nuke, with safety (i.e Chernobyl) being second.

Morbius

bananan,

YES - on site reprocessing is indeed feasible.

That is one of the principal features of the Integral Fast Reactor [ IFR ] that I worked
on in the early part of my career when I was at Argonne National Laboratory.

Here is an interview my former boss, Dr. Charles Till; did with PBS's Frontline in a program
entitled "Nuclear Reaction" hosted by Pulitzer Prize winning author Richard Rhodes
[ "The Making of the Atomic Bomb" ]:

http://www.pbs.org/wgbh/pages/frontl...iews/till.html

As Dr. Till mentions, the fuel for the IFR is in metalic form, as opposed to the oxide
ceramic found in most reactors. By keeping the fuel in metalic form, it is particularly
easy to do the reprocessing. Instead of needing a chemical processing plant, as one
needs with oxide fuel; IFR fuel is reprocessed using metallurgical techniques, namely
"halide slagging" followed by "electrorefining".

As Dr. Till mentions, the plutonium / actinide containing output of this process can NOT
be used as nuclear weapons fuel, but CAN be recycled back to the IFR to be burned.
Therefore the IFR doesn't impose a proliferation risk.

Because the metallurical process is much simpler than chemical reprocessing, the
reprocessing plant can be placed on-site, as you suggest. The plutonium / actinides
never leave the high-radiation region of the plant; so there is no opportunity for theft.

The following web page, courtesy of the Nuclear Engineering Department at the
University of California - Berkeley mentions the on site nature of the IFR's
reprocessing system under the heading of "Diversion":

http://www.nuc.berkeley.edu/designs/ifr/anlw.html

In addition, the IFR was "inherently safe". It did not rely on engineered systems to
shutdown and cool the reactor. All that is needed to keep the IFR safe, is that the
laws of Physics work - which they ALWAYS do.

As stated in the article; the IFR is "almost too good to be true" as Richard Rhodes
phrased it. It's really too bad that President Clinton cancelled the IFR in 1994.

Dr. Gregory Greenman
Physicist

theCandyman

Ronaldo Szilard, Nuclear Science and Engineering director of INL, came to give a talk my my university today. He was talking about the NGNP, and later I had asked if it was similar to the IFR design. Would it also be able to process waste on site?

bananan

Hi,
Well I've been reading the wiki article on generation IV
http://en.wikipedia.org/wiki/Generation_IV_reactor

I'm a little surprised that none will be online at least until 2030 given that fission nuclear plants do exist. If fusion could be performed beyond the break-even point tomorrow, I infer it won't go commericial until 2050. Personally, I'd rather see money diverted from fusion research into fission reactor designs. (That, and the stupid war in Iraq and war on Terrorism). I, uh, vote democrats, and I'm rather disappointed it was a democrat that killed IFR.

I'm surprised that of the designs proposed once-through cycles are seriously considered, as greenies really dislike radioactive waste. Which of the designs of Gen IV do you and nuclear physics community think is most promising?

* 1.1.1 Very-High-Temperature Reactor (VHTR)
* 1.1.2 Supercritical-Water-Cooled Reactor (SCWR)
* 1.1.3 Molten Salt Reactor (MSR)

1.2 Fast reactors

* 1.2.1 Gas-Cooled Fast Reactor (GFR)
* 1.2.2 Sodium-Cooled Fast Reactor (SFR)
* 1.2.3 Lead-Cooled Fast Reactor (LFR)

Astronuc

It's a matter of selecting the right structural materials for a 60 year lifetime - which has yet to be demonstrated, and then convincing a utility to accept the risk of a multibillion dollar/euro investment.

Even with new Gen-III plants utilities are faced with obstacles in building them, and much of that has to do with the disposition of spent fuel.

Of the list above, I'd say MSR and Lead (or Pb-Bi) are least likely, and SCWR is problematic with respect to material performance. As temperatures and pressures increase, so do the challenges to materials performance.

Azael

Astro or Morbius. Now when Bush has openly stated his war feelings for nuclear power. Is there any plans to restart projects like the IFR over there in the states?

Morbius

Azael,

The Bush Administration has put forth an initiative called the GNEP -
Global Nuclear Energy Partnership:

http://www.gnep.energy.gov/

http://fpc.state.gov/fpc/61808.htm

It's a fairly new initiative, just really getting started.

How this initiative will fair with the new composition of the Congress is anybody's guess.

Dr. Gregory Greenman
Physicist

Morbius

bananan,

Bill Clinton and Al Gore CAMPAIGNED on the fact that federal monies were given to
national labs to work on nuclear programs. They promised to put an end to that
practice and shutdown research on nuclear power. That's what they did - and said
so at the time.

Clinton stated that nuclear power research "wasn't needed" in his first
State of the Union address in 1993:

http://www.presidency.ucsb.edu/ws/index.php?pid=47232

"We are eliminating programs that are no longer needed, such as
nuclear power research and development. We're slashing subsidies
and canceling wasteful projects."

--President William J. Clinton, February 17, 1993

Dr. Gregory Greenman
Physicist