[chimera]

The bottom line is that unprocessed, light-water reactor spent fuel rods are a very poor waste form for permanent disposal in a geologic repository, with the potential to cause high-consequence scenarios. Yucca Mountain should not be a permanent repository for unprocessed light water reactor spent fuel - rather it should be a centralized, monitored retrievable storage facility.

An MRS facility certainly makes sense from a technical and resource utilization viewpoint. As I recall the MRS concept was floated for a time prior to the YM decision, and the opposition from the pols and various assorted wacko groups was even more vociferous than for YM at this stage. Why? Because the MRS is perceived by the wackos as being beneficial to the industry, whereas YM, while beneficial in the sense of answering the "what do we do with the waste" boogeyman they always bring up, is perceived as less beneficial because it closes the door on commercial reprocessing.

So while MRS makes sense, the reality is that the political system may not allow it, but will allow a permanent repository. It may not be the best thing to do, but may be the best we can do under the present circumstances. It will do some good in the sense of keeping LWR technology viable by defusing the wackos' argument about "nobody knows what to do with the waste". If YM is operational, we will know what to do with the waste, even if it isn't the best thing to do from a technical, economic, or strategic viewpoint. But we may not have any choice.

So, we have reached a point of agreement. I like that. Gives me the warm and fuzzies. In the interests of fairness and trying to see the other side of the coin, I understand what you are saying about the diversion risks. I will respectfully agree to disagree on the "plutonium mine" hazard scenario and its relative probability of occurrence and possible consequences. I just think it is a less likely scenario than you do. Repository siting and construction, the design and fabrication of the canisters (BTW, you probably can't break them open at the welds, because with existing joining technology it is possible to make the weld zones stronger than the native metal), the allowance of conservative design margins and assumptions in the risk analyses, all lead me to think reasonable steps have been taken to reduce that risk. And, from my (numerous) dealings with the NRC, I think they will take a "reasonable person" approach and give lower weight to less likely scenarios when it comes to making a licensing decision.

So, any other loose ends to tie up in this discussion?

[drmatt]

I agree for the most part with your interpretation of the politics, but there is a little bit of momentum these days to re-visit alternatives to direct disposal of unprocessed LWR spent fuel. In fact, I am presently working on a DOE-funded project to develop transmutation fuels - so even DOE is not putting all of their eggs in one repository.

With regard to MRS, Yucca Mountain (as presently designed) will in effect be an MRS facility for at least the first 100 years or so after it opens. That's because the current design requires the drift tunnels to be actively ventilated for 60 years, otherwise fuel inside the canisters would overheat. Natural ventilation is then relied upon for another 40 years or so. So there are no plans to backfill the tunnels (which I think enhances somewhat long-term proliferation risks). DOE adopted this design because the unventilated, backfilled repository was limited to a very sparse loading of about 4 canisters per acre, because of the decay heat load of the spent fuel and its impact on the structural integrity of the tunnels. When you look at all the extraordinary measures DOE has adopted in order to try and make this repository design work (million dollar canisters, titanium rock/drip shields, adding neutron poison to the canisters, active ventilation, etc.) it becomes increasingly obvious (at least to me) that unprocessed LWR spent fuel is just not the right thing to leave in the ground.

Thanks for the give and take - it's been a good discussion.