Mixed Oxide Fuel, or MOX Fuel, Advantages and Disadvantages

[wrecked_edsel]

The concerns about MOX are real, and do we really want to deal with the aftermath of it ie... higher dose rates, higher contamination levels, alpha contamination ? The chances of an accident copuld be increased by the use of MOX fuel. Are todays reactors able to handle the MOX type fuels. Let's hear some other opinions.

[Marco]

Here in Europe we use MOX elements since ten years or more. At our plant we don't know any problems regarding MOX fuel. What are the increased possibilities of an accident that you mentioned ? In our MOX elements is Plutonium from Sovjet atomic weapons contained, so we do a kind of disarmament with the help of commercial use of nuclear power.
Doesn't use US plants MOX fuel ?

[Kernwerker]

Hmm? well here in Germany we have been using MOX fuel assemblies for some time now. Except for some minor RP measurements i.e a bit higher neutron and gamma doserates compaired to "conventional" fuel assemblies and some alpha contamination precautions ( we never experienced any). Well we really never had any probs

[HydroDave63]

Edsel, the fuels engineers will tell you it is just as safe, etc. The real problem I see with MOX fuel, aside from the greatly increased alpha levels (what plant has NEVER had fuel flea problems/broken pins ?) is the shifted neutron spectrum. There will be more Pu-239 buildup at EOC, which can produce a positive moderator temp. coefficient. In a PWR you have the ability to change boration if there are surprises in the flux profile change from the Pu-239 buildup, but less room to maneuver CEAs at a BWR. I'd love to see the analysis done for a BWR 100% load rejection at End of Core, and prove that the void coefficient with a MOX core would NOT violate adequate shutdown margin requirements. Color me skeptical.

[Kernwerker]

Edsel, the fuels engineers will tell you it is just as safe, etc. The real problem I see with MOX fuel, aside from the greatly increased alpha levels (what plant has NEVER had fuel flea problems/broken pins ?) is the shifted neutron spectrum. There will be more Pu-239 buildup at EOC, which can produce a positive moderator temp. coefficient. In a PWR you have the ability to change boration if there are surprises in the flux profile change from the Pu-239 buildup, but less room to maneuver CEAs at a BWR. I'd love to see the analysis done for a BWR 100% load rejection at End of Core, and prove that the void coefficient with a MOX core would NOT violate adequate shutdown margin requirements. Color me skeptical.

Hmm a Pu-239 buildup? Well that would mean that we would have a higer resonance absortion peaks. But wouldnt the fuel temperature coefficient or doppler coefficient be the main reason for a buildup. What i mean doesnt the doppler coefficient have much greater effect then the the moderator coefficient? I mean since this effect is also called the prompt temperature coefficient meaning higher reactor power emmediately causes higher fuel temperature. Not sure if i said it right please correct me if i am wrong here

[happycobra]

I  am a newer! This is my first time to sent massage here!
I want to honw what will happened after the burnup reach 40GWd/t？
what's the key problem in this phase?
and how to solve it?

[NaehringJ]

i believe Catawba in south caroline will be the first US plant to use MOX fuel, im a skeptic about mox fuel on account of plutonium 239 having a half life of hundreds of millions of years

[jakester]

I believe, after the MOX is used, it should contain less PU-239 than it did when it went into the reactor. Also a "normal" load of fuel (not MOX) will contain some P239 after a cycle in the reactor. So, I wouldn't think that using MOX fuel is a bad thing......

[RDTroja]

...im a skeptic about mox fuel on account of plutonium 239 having a half life of hundreds of millions of years

Having a long half-life is not necessarily a bad thing. The real concern is the total amount of radioactive material. If it has a short half-life the radiation intensity (dose rate) will be high and the duration short. With a longer half-life, the duration will be long but the intensity low. Shorter half-life radioactive materials are actually harder to deal with (except for thiose half-lives so short that we never see them) because we have to take more protective measures to prevent higher exposures in the short term. Once the material is 'disposed of' all we have to do is the long term stewardship including occasional monitoring. And if you are concerned about long half-lives, check out U-238 -- at 4.5 Billion years I think we can safely say it is just as much of an issue as the Pu-239. In addition to that, not using the Pu-239 doesn't make it go away. As a matter of fact, it goes away faster if we split it up.

The only significant difference I can come up with is a slight change in the isotopic mix in the waste stream that may result in probably minor changes in dose and dose rates... but that may be positive instead of negative (more research than I am prepared to do right now.)

[aabrams]

i believe Catawba in south caroline will be the first US plant to use MOX fuel, im a skeptic about mox fuel on account of plutonium 239 having a half life of hundreds of millions of years

I'm pretty sure Pu-239's half-life is on the order of 24,000 years.  I would probably be more concerned about toxicity than radioactivity.

[RDTroja]

I'm pretty sure Pu-239's half-life is on the order of 24,000 years.  I would probably be more concerned about toxicity than radioactivity.

Very true. I didn't even look at that -- and it should have stuck out like a sore thumb. If the half life of Pu-239 was in the 'hundreds of millions of years' range it would probably be naturally occurring. I guess that really makes 4.5 billion years look long.

[SloGlo]

Very true. I didn't even look at that -- and it should have stuck out like a sore thumb. If the half life of Pu-239 was in the 'hundreds of millions of years' range it would probably be naturally occurring. I guess that really makes 4.5 billion years look long.

even 4.5e9 isn't all that long on the scale of long lifed isotopics.  but in order to return to the topic, dealing with after effects of the engineers of this world is what some of us do best.

[alphadude]

lot of times its dealing with low bid and production goals-