Monday, September 10, 2012

Wading into the "nuclear zombie" horde

Tomorrow evening, the NNSA will be hosting a public meeting concerning its Supplemental Environmental Impact Statement on the disposition of surplus weapons-grade plutonium (WGPu) as mixed-oxide ("MOX") fuel for consumption in power reactors.

This is not a new policy - the decision to dispose of the surplus weapons material was put into place during negotiations with the Russians which took place during the Clinton Administration. The goal was quite simple: with the Cold War at an end, both countries had far greater stocks of weapons material than reasonably necessary for defense, and disposing of this material was determined to be a national security priority. In particular, both the U.S. and the Russians have agreed to dispose of 34 metric tons (about 75,000 pounds) of surplus bomb material.

Such an agreement is similar in form to the "Megatons to Megawatts" program now winding down, in which surplus highly-enriched uranium (HEU) formerly for weapons was down-blended into low-enriched uranium (LEU) for reactor fuel and permanently destroyed.

Scrambled eggs / plutonium
The NNSA proposal works along the same lines - take what is currently a weapons-grade asset and blend it down (in this case, convert the plutonium into an oxide powder and blend it to about a 4% mixture with uranium) and then burn it in reactors. The advantage to this approach is relatively straightforward: by burning the plutonium in reactors, the plutonium isotopic makeup becomes "scrambled" - basically rendering it useless for weapons, even if it were ever recovered from the spent MOX fuel. Further, the irradiated fuel adds a second physical barrier to theft and diversion - namely that now this material is now trapped inside a highly radioactive fuel rod. (The treaty agreement likewise forbids the two countries from reprocessing the spent MOX fuel for several decades.)

So who would object to what sounds like a sensible application of the "swords to plowshares" concept?


Specifically, "nuclear zombies." Greenpeace and other anti-nuclear activists, in continuing their slow decline into generalized misanthropy over any stated concern for the environment, have come out in force against the NNSA proposal, going so far as to set up shop in Chattanooga. Their particular M.O. in this has been a series of "nuclear zombie" theatrics - starting with a TVA hearing on completing the mothballed reactor project at Watts Barr Unit 2. The anti-nuclear critics leaped upon the construction restart as reviving a "zombie" reactor build (once dead, now undead - yes, clever there folks) and have been working with the meme since.

In keeping with the theme, I'll be leading a contingent of trained nuclear engineering students zombie hunters  from the University of Tennessee down to the public meeting tomorrow both as a show of support and more importantly as a resource in trained experts who can sort the facts from the theatrics.

As always though with zombies, it's important to remember the most important rule of dealing with zombies: Always remember the double-tap. As we prepare for the charge into the zombie horde, it's thus useful to put down a few of the "living dead" arguments out there which seemingly seem to lumber on from beyond the grave. As a good companion piece, I also highly recommend Dan Yurman's full frontal assault on the zombie horde.

Zombie argument #1: MOX fuel is unsafe

Several countries, including France and Japan, already use MOX fuel in their reactors. This plutonium comes from recycling the plutonium that is built up in uranium fuel as reactors are operated. (Thus, to emphasize: plutonium in reactors is not a foreign concept - in the course of regular operations, plutonium is built up and burned within the fuel. In fact, near the end of a fuel bundle's lifetime, much of the energy produced from fission comes from the fissioning of plutonium itself, in addition to the depleting fissile uranium in the fuel).

Plutonium fuel does burn a bit "hotter" (fission releases a nominally larger amount of energy for plutonium compared to uranium), but as Yurman points out in the above article, this is relatively similar to how a wood-burning stove works. Certain woods burn hotter (think hardwoods); but control of the reactor power and temperature is governed by many devices beyond the fuel, including burnable poisons and control rods which regulate the reaction rate. The goal of MOX fuel is essentially to use it as a replacement for ordinary uranium fuel - meaning the reactors are to run at the same power level as before. This is a well-understood concept.

Further, the MOX fuel would not compose more than a fraction of the core loading. Yurman points out that TVA's initial plan (if they decide to participate in the MOX fuel program) would likely involve starting out with a loading of about 8 assemblies in the reactor; pressurized water reactors typically will have around 193 assemblies, meaning MOX will start off making up around 4% of the core, with an eventual ramp-up to around 40%.

Zombie argument #2: MOX is an inferior way to dispose of plutonium

Of the more sophisticated "zombie arguments out there, one that seems to arise again and again is the idea that disposing of plutonium in MOX fuel - be it from civilian reprocessing or from disposal of surplus weapons materials - is an inefficient and expensive way to deal with the problem. Instead, they say, we should dispose of the material in glass logs ("vitrification") and then bury the glass logs in a deep geologic repository. Such approach has been vocally promoted by the now-current chairwoman of the NRC, Dr. Allison MacFarlane. (Have the zombies gotten to her too, do you suppose?)

In particular, some critics have pointed out the formerly proposed "two track" approach first sketched out by scientists and engineers with the Department of Energy at Savannah River, where the conversion of weapons material will take place. There are of course two problems with this - the first being that this approach was originally proposed because of identified problems in handling about 9 metric tons of the plutonium, as it was contaminated and deemed potentially unsuitable. (The remaining 25 metric tons were to be converted into MOX). However, as those problems were overcome, the decision was made to proceed exclusively on the MOX track, thus saving money by not creating two separate facilities.

From a strictly technical standpoint, disposal of surplus plutonium in MOX fuel is the preferred pathway of numerous technical and scientific organizations, including the National Academy of Sciences, the American Nuclear Society, as well as numerous academic organizations, including the Harvard Project on Managing the Atom. (It's rare when I agree with the last party, so you know there's something going on when that one happens).

Second, and perhaps more important, is the fact that there is significant diplomatic pressure from the Russians to convert and burn the material as MOX fuel rather than to vitrify it, as they are concerned that the vitrified material encased in glass logs may one day be recoverable. By contrast, once the MOX fuel has been irradiated, not only is the material far more difficult to handle, but the plutonium content itself becomes contaminated with "unfavorable" species of plutonium which render the material unusable for weapons use. Thus, the MOX route represents a more permanent disposal pathway.

Finally, a factor which should not be neglected, is that MOX fuel represents a viable way to extract a useful resource - energy - out of what was formerly simply an implement of mass destruction. One can quibble that the economic costs of the MOX route do not necessarily outweigh the economic value of the electricity produced, but regardless the material would have to be converted into a form suitable for disposal - be it for conversion into glass logs or into reactor fuel. In this regard, it is useful to look at this from a marginal cost perspective - i.e., the benefit of electricity should not be weighed against the full cost of the MOX fabrication facility but against the marginal difference in the cost of the MOX facility versus vitrification. In this regard, MOX begins to look like a much better deal, even if it doesn't break even. (Lacking for immediately accessible numbers, this is difficult to quantify).

Zombie Argument #3: Nobody wants MOX

A relatively specious argument which can be relatively swiftly put down. First, TVA has expressed interest - hence why these hearings are taking place in the first place. In addition to TVA, Duke Energy has also expressed potential interest in purchasing the converted MOX fuel from the Savannah River Site.

Most of the reason U.S. utilities have been reluctant to purchase MOX fuel for reactors up until now comes down to cost - pound for pound, MOX fuel does cost more, and utilities receive no credit back toward fees paid into the nuclear waste fund for any net reduction in waste sent to an (eventual) repository. (The Megatons to Megawatts program, by contrast, produced a fuel which is the same exact form as used in current reactors - hence, it was cheaper and easier).

However, because the NNSA plan is explicitly designed to dispose of surplus weapons material, it is being done with a subsidy to offset this cost. (Again, to emphasize: what is being paid for is to ensure a final disposition of the plutonium.)

Closing thoughts

Like with ordinary zombies, I'm not even really sure we can expect the level of sophisticated arguments that I've deconstructed above so much as a slow grope for brains. (Yes, cheap shot, I know.) I say this only because I remain unconvinced that "nuclear zombie" demonstrations, which Greenpeace and other anti-nuclear organizations have invested considerable resources into, have anything to do with setting the tone for well-reasoned, thoughtful consideration of alternatives.

Ash with his boomstick
If you need to find me at the meeting tomorrow, I'll be the guy with the
. (Note: No one's bringing any weapons. Please don't sue.)
Regardless, I will be there tomorrow, braving the zombie horde. If you're anywhere around the Chattanooga area tomorrow, do consider joining us. One of the key points I have continued to emphasize with my students is the need to simply show up - not only such that groups interested more in theatrics than in debate don't simply carry the day by default, but also such that we can be there as a resource - answering questions from the non-zombified public and putting to (final) rest some of the more putrified misinformation.

The hearing will be at the Chattanooga Convention Center (1150 Carter Street
Chattanooga, TN). Open house starts at 5:30, followed by a technical presentation by the NNSA at 6:30 and public comments following up 8:00.

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