Can Radioactive Material Be Recycled?

[Astronuc]

Reprocessing has its own problems - such as remote handling of the PuO2 and MOX, and fuel rods and assembly. That has made MOX fuel quite expensive.

Actually Yes - From personal hands-on experience in the commercial industry, specifically in fuel manufacturing facilities in US and Europe.

I have handled UO2 (not ERU) fuel, but MOX (with Pu recycled from LWR spentfuel) fuel handling is done remotely. Please check Pu isotopic vector - Pu239, 240, 241 and 242 for LWR spentfuel. There are also trace amounts of Am-241.

Pu-240
Half life: 6564 years
Mode of decay: Alpha to U-236
Decay energy: 5.256 MeV
Mode of decay: SF
Branch ratio: 5.7E-6 %

Pu-241
Half life: 14.35 years
Mode of decay: Beta to Am-241
Decay energy: 0.021 MeV
Mode of decay: Alpha to U-237
Branch ratio: 0.0025 %
Decay energy: 5.140 MeV

Pu-242
Half life: 373300 years
Mode of decay: Alpha to U-238
Decay energy: 4.984 MeV
Mode of decay: SF
Branch ratio: 0.00055 %

Am-241
Half life: 432.2 years
Mode of decay: Alpha to Np-237
Decay energy: 5.638 MeV
SF negligible

Certainly WG MOX is more like to UO2.

 

[Arctic Fox]

Could you explain the "decay energy"?

I'm also trying to learn about RTGs and possible alternative fuels for it - Am-241 @ 5.638MeV > Pu-240 @ 5.256 MeV?

Isn't Am-241 inside smoke detectors?

And isn't Pu-240 weapons-grade material?

 

[hitssquad]

Weapons-grade plutonium

isnt Pu-240 weapons-grade material?

None of the even-numbered Plutonium isotopes are preferred for weapons. Pu-239 is the typically preferred weapons isotope. "Weapons grade" refers to the amount of weapons-preferrable isotope present. In the case of plutonium, weapons-grade is generally considered 93% or better Pu-239.

 

[Morbius]

Could you explain the "decay energy"?

I'm also trying to learn about RTGs and possible alternative fuels for it - Am-241 @ 5.638MeV > Pu-240 @ 5.256 MeV?

Isn't Am-241 inside smoke detectors?

And isn't Pu-240 weapons-grade material?

Arctic Fox,

When an atom is radioactive, it has "extra" nuclear energy that it
gets rid of by emitting radiation in some form. That radiation could be
a gamma ray, an alpha particle, or a beta particle [ electron ]. The energy
that is released when the atom decays is the decay energy.

An RTG puts that energy to use. The radioactive material becomes hot,
and the heat is converted to electricity by thermocouples or some other
method.

The radiation source in smoke detectors is Americium-241

"Weapons grade" plutonium is plutonium that has a high concentration
of Pu-239. The weapons designer doesn't want Pu-240 or other even
numbered isotopes in the weapons fuel. These even numbered isotopes,
especially Pu-242 have a propensity to spontaneously fission which is
undesired.

Dr. Gregory Greenman
Physicist

 

[russ_watters]

One little thing to add: "Envrionmentalists" tend to cite half-life as a measure of radioactivity, which is (sorta) correct, except that they get it backwards. You usually see long half-life=bad. But when something has a long half-life, that means it is't giving off much radiation compared to something with a shorter half-life.

 

[Morbius]

One little thing to add: "Envrionmentalists" tend to cite half-life as a measure of radioactivity, which is (sorta) correct, except that they get it backwards. You usually see long half-life=bad. But when something has a long half-life, that means it is't giving off much radiation compared to something with a shorter half-life.

Russ,

Very good point!

For example, U-238 has a half-life of 4.47 BILLION years - about the age
of the Earth.

Since Depleted Uranium is mostly U-238; the so-called "evironmentalists"
have a field day with that long half-life.

However, as Russ points out - that long half life is precisely because it
has such a low decay rate - and hence a low level of radioactivity.

U-238 is "almost" stable.

To take it to the logical conclusion; Lead-208 has an INFINITE half-life;
because Lead-208 is stable.

Dr. Gregory Greenman
Physicist

 

[CharlesP]

So no one has a better suggestion than Yucca Mountain and Yucca Mountain is in hot water. This is one reason that Nuclear power is not considered the answer to the energy crisis. Let's summarize:
Send to sun - expensive unreliable
Drop in volcano - stuff comes out of volcanos (15000 psi)
Ocean trench - not trusted
Burn up in reactor - not effective
Use in batteries - health hazard
Use Yucca for heat - degrades containment

It doesn't matter how long the list gets, its all bad news.

 

[brewnog]

CharlesP, are you really serious?

Reprocessing!

 

[russ_watters]

So no one has a better suggestion than Yucca Mountain and Yucca Mountain is in hot water. This is one reason that Nuclear power is not considered the answer to the energy crisis.

As already said a number of times, the problems with nuclear are entirely political. Both reprocessing and long-term storage are just fine scientifically.

 

[Astronuc]

Use Yucca for heat - degrades containment

What, pray tell, is the evidence to support this assertion?

In debate or classic rhetoric, it is customary to provide evidence in support of one's claim. In a technical matter such as this thread it would be appropriate to provide a calculation. What materials does one assume? What are the initial and boundary conditions of the thermal field? What degradation mechanism does one propose?

 

[CharlesP]

So no one has a better suggestion than Yucca Mountain and Yucca Mountain is in hot water. This is one reason that Nuclear power is not considered the answer to the energy crisis.

As already said a number of times, the problems with nuclear are entirely political. Both reprocessing and long-term storage are just fine scientifically.

That of course is an opinion which has been rejected by mainline scientists.
I saw in Physics Today that some study group determined that the Yucca project would not meet confinement time of 10,000 years and this is a big obstacle. I hope they solve their problems because this is the only hope for any long term confinement.
Reprocessing caused Rocky Flats which has caused many folk to decide that won't be permitted again.

 

[Astronuc]

In 10,000 years, most of the highly radioactive nuclides will have decayed to inert forms. Take two common isotopes Cs-137 (t1/2~ 30 yrs) and Sr-90 (t1/2~28.8 yrs). Cs-137 will experience 333 half-lives, and Sr-90 about 347 half-lives in 10,000 yrs. Their activities at that time will be exp(-333) and exp(-347) of the activity when placed in YM. Pretty small numbers.

The shorter half-life material will have even lower activity.

Radio nuclides with half-lives on the order of 100 years would have activities of exp(-100) - still a very small number.

But what about something with a half-life of say 1000 yrs. Well, it would decay to activities of exp(-10) = 4.5E-5. However, if one looks at the fission yields - the yields of long-lived isotopes are relatively low (say about 0.001 to 0.00001).

The concern then is the long-lived - low activity species with half-lives of 10,000 years or more.

But in 10,000 yrs, they will surrounded by inert material - metal oxides - which will probably have very low solubility.

But then the spent nuclear fuel is stored in corrosion resistant steel containers - or perhaps concrete - which is then surrounded by the rock of the mountain - which has been geologically stable for a few million years.

 

[CharlesP]

In 10,000 years, ...

But what about something with a half-life of say 1000 yrs. Well, it would decay to activities of exp(-10) = 4.5E-5. However, if one looks at the fission yields - the yields of long-lived isotopes are relatively low (say about 0.001 to 0.00001).

The concern then is the long-lived - low activity species with half-lives of 10,000 years or more.

But in 10,000 yrs, they will surrounded by inert material - metal oxides - which will probably have very low solubility.

But then the spent nuclear fuel is stored in corrosion resistant steel containers - or perhaps concrete - which is then surrounded by the rock of the mountain - which has been geologically stable for a few million years.

Steel and concrete have not passed stability tests for these time periods and the mountain and climate are both subject to unpredictable changes. Especially with humans doing everything suicidal imaginable.

 

[Morbius]

Steel and concrete have not passed stability tests for these time periods and the mountain and climate are both subject to unpredictable changes. Especially with humans doing everything suicidal imaginable.

Charles,

You have got to be the most ill-informed anti-nuclear propagandist
posting on this site.

Steel, concrete, and the volcanic tuff of the mountain have been extensively
studied, tested, and modeled:

http://www.llnl.gov/str/Glassley.html

The radioactivity of the waste will be much less than that of the ore
dug from the ground in a time period considerably less than any time
in which the containment might fail.

Dr. Gregory Greenman
Physicist

 

[russ_watters]

Playing devil's adovocate here (of a different sort), I think its an unreasonable constraint to expect any storage site to survive 10,000 years. Doing so assumes no further advances in nuclear technology will be made. Considering we've only known about nuclear power for 75 years or so, I think chances are pretty good the next hundred or thousand years of scientific discovery will reveal a way to deal with all that waste (dare I say - reprocessing!).

 

[brewnog]

Russ, faith in the future is indeed a wonderful thing!


In any case, I'm interested about this 'Rocky Flats' card which CharlesP seems to be playing a lot. Having seen reprocessing in action a number of times in the UK (and, I might add, reprocessing of waste originating from the US), I'd like to know more about the reasons it's currently outlawed. Morbius, you come across as reasonably well informed, (and also, much of what I've googled on the Rocky Flats issue seems to be horrific, unsubstantiated propaganda), - what happened?

 

[russ_watters]

HERE is some history of the site. Basically, they made nuclear weapons parts there (plutonium triggers) and they polluted a lot. I'm not real up on what the conspiracy theorists say about it though.

 

[Astronuc]

The Carter administration halted reprocessing out of concerns over the issue of 'proliferation' of Pu.

Economics in the US do not favor reprocessing at the moment - unless YM drags on - and back end costs start soaring. Europe, particularly France/Belgium, have entirely different fuel cycle economics. France and Belgium have a great deal of experience in reprocessing commercial spent fuel.

As for Rocky Flats - it was bad program management. Some folks thought that since they were in the weapons complex, they did not need to follow appropriate procedures or environmental regulations. This allowed for sloppiness.

The site provided by Russ_Watters pretty much describes the situation. It was unncessary. And it had nothing to do with technology - just bad (negligent and contemptible) decisions by those who were responsible for operating the plant. It is my experience that the vast majority of folks in the commercial nuclear industry do not behave in that manner.

 

[CharlesP]

The radioactivity of the waste will be much less than that of the ore dug from the ground in a time period considerably less than any time in which the containment might fail.

There is a study out which caused a stir in Congress which disagrees with that. I hope it is not a show stopper. We need mean quality men but Yucca is our only hope.

As for Rocky Flats - it was bad program management. Some folks thought that since they were in the weapons complex, they did not need to follow appropriate procedures or environmental regulations. This allowed for sloppiness...It is my experience that the vast majority of folks in the commercial nuclear industry do not behave in that manner.

That may be, but the present administration resembles the Rocky Flats managers, and with busted regulations the temptation may be too great. Once again we need "tough quality folk" and Three mile Island did not give me any confidence.
If the managers and bean counters could be locked out and engineers allowed to do their jobs, we might get a quality product- just what we need to keep us from freezing in the dark, just a few short years from now.
Rocky Flats is on prime land between Denver and Boulder. The area even outside the fence was so radioactive that some folks wanted to dig up the soil. Physics Today had a report on the waste tanks at Hanford that gave me the creeps. Of course today folks are much more careful.

 

[Morbius]

There is a study out which caused a stir in Congress which disagrees with that. I hope it is not a show stopper. We need mean quality men but Yucca is our only hope.

I don't know how some "study" can disagree with the Laws of Physics.

Nuclear waste does decay. The longest lived nuclear waste component
of any consequence is Cesium-137 which has a 30 year half-life.

So the radioactive decay of nuclear waste is bounded above by an
envelope with a 30 year half-life decay rate.

No study needed - it's just physics.

That may be, but the present administration resembles the Rocky Flats managers, and with busted regulations the temptation may be too great. Once again we need "tough quality folk" and Three mile Island did not give me any confidence.

Why do political prejudices always seem to dominate these discussions
of late? How nuclear power plants are run, and how engineers design
equipment is not dependent on the Administration in Washington.

President Bush and his minions are much too busy to be concerned about
how to run nuclear power plants.

If the managers and bean counters could be locked out and engineers allowed to do their jobs, we might get a quality product- just what we need to keep us from freezing in the dark, just a few short years from now.

When I was working toward my doctorate at M.I.T. - I attended a seminar
by the then president of the American Nuclear Society. He stated that
in the wake of TMI, scientists and engineers could tell the CEOs of
utilities that the nuclear power plant that they were running could
financially destroy their company if they don't run it correctly!

THAT gets their attention. Then he said the good news was "...we can
help you.." - the "we" being the engineers.

For the last quarter century - that IS the way it has been in the nuclear
industry. Utilities are extremely careful in the manner in which they
operate nuclear power plants.

Rocky Flats is on prime land between Denver and Boulder. The area even outside the fence was so radioactive that some folks wanted to dig up the soil. Physics Today had a report on the waste tanks at Hanford that gave me the creeps. Of course today folks are much more careful.

Rocky Flats was a weapons production plant. Rocky Flats took ingots
of Plutonium and fashioned them into the heart of a nuclear weapon.

How does that have anything to do with commercial nuclear power?

The operations conducted at Rocky Flats were not those that are done
in the commercial nuclear power industry.

The operator / contractor at Rocky Flats was Rockwell International -
the people that built the Space Shuttle. So Rocky Flats was managed
by a company that didn't have anything to do with nuclear power.

So how does the experience at Rocky Flats have anything to say with
regard to commercial nuclear power. It has virtually nothing in
common with commercial nuclear power.

Dr. Gregory Greenman
Physicist

 

[russ_watters]

When I was working toward my doctorate at M.I.T. - I attended a seminar
by the then president of the American Nuclear Society. He stated that
in the wake of TMI, scientists and engineers could tell the CEOs of
utilities that the nuclear power plant that they were running could
financially destroy their company if they don't run it correctly!

THAT gets their attention. Then he said the good news was "...we can
help you.." - the "we" being the engineers.

For the last quarter century - that IS the way it has been in the nuclear
industry. Utilities are extremely careful in the manner in which they
operate nuclear power plants.

Slightly related/OT, but this reminds me of the Morton Thykol (sp?) Engineering Ethics case study. The management of that company overruled their engineers on an engineering decision which led directly to the destruction of the Space Shuttle Challenger.

The point is that managers seem to me to be equally arrogant/ignorant in dealing with engineers and engineering decisions: but only once. One error caused by not listening to engineers is enough to destroy a company or even an industry when the stakes are this high. TMI was that one error and I believe Morbius when he says 'the management' got the message.

 

[brewnog]

...but Yucca is our only hope.

So basically, that's untrue. Reprocessing, and storage elsewhere, are both perfectly viable solutions which are being constantly discredited. I now see that Rocky Flats is not even an example of a waste disposal plant, let alone an example of why reprocessing should not be carried out in the US!

If reprocessing was inherently as dangerous as is being made out, I doubt the States would be as happy to outsource nuclear waste reprocessing as they currently are.

 

[Morbius]

So basically, that's untrue. Reprocessing, and storage elsewhere, are both perfectly viable solutions which are being constantly discredited. I now see that Rocky Flats is not even an example of a waste disposal plant, let alone an example of why reprocessing should not be carried out in the US!

If reprocessing was inherently as dangerous as is being made out, I doubt the States would be as happy to outsource nuclear waste reprocessing as they currently are.

brewnog,

Reprocessing isn't being opposed because it is dangerous - but because of
the type of waste reduction it represents.

The bulk of the material discharged from a reactor is U-238. U-238
represents the bulk of the material that went into the reactor, and the
bulk of the material that comes out.

The 3-4% of the fresh fuel that was U-235 has been fissioned - and
replaced by radioactive fission products. A small amount of U-238 has
been transmuted to Pu-239 and either fissions or remains in the fuel.

However, the bulk of the spent fuel is represented by U-238 that is no
more radioactive than when it was dug out of the ground.

Reprocessing allows one to separate the U-238 from the radioactive
fission products and actinides. It's the fission products and actinides
that are the true "nuclear waste".

One can visualize the degree of waste reduction from the following.
If all the electricity for a family of 4 were generated by nuclear power
for 20 years - the waste generated would fit in a shoebox.

If one reprocesses that shoebox full of waste - one is left with an amount
of waste that fits in a common pill bottle.

That's the reason some are opposed to reprocessing - it greatly reduces
the volume of waste. Some don't want to reduce the amount of waste.
They also don't want to open a facility to store the waste. Their
objective is to totally stop the back end of the nuclear fuel cycle - to
stop any way of dealing with the waste. They want the spent fuel to
accumulate in the cooling pools at the reactors. If they can stop the
disposal of waste - and the pools fill up - then the utility can't operate
the reactor which will generate more waste. They will have succeeded
in their true objective - shutting down the nuclear power industry.

Dr. Gregory Greenman
Physicist

 

[Arctic Fox]

brewnog,
They want the spent fuel to accumulate in the cooling pools at the reactors.

Sheesh, contact me via email and I'll give them a location in Mexico they can drop it off for me...

 

[brewnog]

Cheers for that Morbius, sorry, I wasn't implying that it was commonly being made out that it was dangerous, rather just that it seemed CharlesP was making it out as such.

But even with all that said, (esp. the bit about people being opposed to volume reduction), do you believe it *still* boils down to general public/political misconception?

 

[CharlesP]

Nuclear waste does decay. The longest lived nuclear waste component of any consequence is Cesium-137 which has a 30 year half-life.
So the radioactive decay of nuclear waste is bounded above by an
envelope with a 30 year half-life decay rate.

Using this as a starting point I did a rough calculation and came to the conclusion that a pill bottle of Cs137 will decay to about 600 atoms in 2100 years. (6x10E23 = 600x 10E21 = 600 x 2E70 --> 70x30 = 2100 years)
I think I could tolerate 600 radioactive atoms in my yard. That is a lot less than the cosmic ray background.
Then why does anyone care about containment longer than two thousand years?

 

[Astronuc]

Then why does anyone care about containment longer than two thousand years?

Because - some isotopes will moderate to long half-lives are still around, e.g.

Pu-239
Half life: 24,131 yr

Pu-240
Half life: 6564 years

Pu-242
Half life: 373,300 years

If particles of Pu-239 and 240 are inhaled into the lung or ingested into the body, there is a strong risk of cancer. There are those who are opposed to YM because they believe that something catastrophic will occur such that the Pu material will escape and find its way to populated areas where it will be absorbed in a favorable manner and cause cancer. Others believe that terrorists will sabotage a shipment of spent fuel on its way to YM, with the same results - dispersion of Pu and other fission products into the environment. However, shipping systems are designed to be secure and since they are massive, no one is going to grab and run off with a spent fuel container.

 

[Morbius]

Because - some isotopes will moderate to long half-lives are still around, e.g.

Pu-239
Half life: 24,131 yr

Pu-240
Half life: 6564 years

Pu-242
Half life: 373,300 years

If particles of Pu-239 and 240 are inhaled into the lung or ingested into the body, there is a strong risk of cancer. There are those who are opposed to YM because they believe that something catastrophic will occur such that the Pu material will escape and find its way to populated areas where it will be absorbed in a favorable manner and cause cancer. Others believe that terrorists will sabotage a shipment of spent fuel on its way to YM, with the same results - dispersion of Pu and other fission products into the environment. However, shipping systems are designed to be secure and since they are massive, no one is going to grab and run off with a spent fuel container.

Astronuc,

However, Pu-239, Pu-240, and Pu-242 are exactly the isotopes that will
be removed from the waste and recycled back to the reactor to be
fissioned if one reprocesses.

When one reprocesses nuclear waste, the Pu-239, Pu-240, and Pu-242
will no longer be in the waste stream that is buried.

That's another good reason to reprocess - it makes the disposal of
nuclear waste much, much easier! That's why countries other than the
USA, like Great Britain and France - reprocess their spent fuel.

It's a win-win situation; one gets additional "mileage" from the nuclear
fuel - by being able to get additional energy by fissioning the residual
Pu-239, Pu-240, and Pu-242 in spent fuel which will be separated out and
returned to the reactor as fuel. One eliminates the long lived isotopes
from the waste stream - so one doesn't need to worry about the long
lived isotopes - they are no longer in the waste stream.

Reprocessing just makes so much sense - which is why the obstructionist
anti-nuclear people got Congress to outlaw it in the USA back in 1978!

Dr. Gregory Greenman
Physicist

 

[Astronuc]

I agree that Pu-239, Pu-240, and Pu-242 are exactly the isotopes that will be removed from the waste stream and recycled if the US were to reprocess.

But the utilization of YM is for a once-through fuel cycle, which is where the US is today.

The point I was trying to make is that there are those opponents of YM who are afraid that these Pu isotopes will somehow leak out of YM and get into the environment. I happen to disagree with that scenario.

I would certainly be interested to see if someone in DOE or the commercial industry seriously considers reprocessing again.

 

[CharlesP]

One problem with reprocessing is that no chemical process is perfect. That means separation will be only approximate. There will be some of everything in each waste stream. That probably is not acceptable depending on the numbers which I don't have.

Then for more trouble - anyone remember Karen Silkwood? Wasn't a movie made about her?