Thursday, September 29, 2011

Dissecting the BRC report, Part II: Where interim storage falls short

Perhaps the worst that could be said for the BRC report is in its overall lack of ambition. In particular, the BRC declined to comment on the viability of Yucca Mountain as a geologic repository, noting:

We take no position on the Administration’s request to withdraw the license application. We simply note that regardless what happens with Yucca Mountain, the U.S. inventory of spent nuclear fuel will soon exceed the amount that can be legally emplaced at this site until a second repository is in operation. So under current law, the United States will need to find a new disposal site even if Yucca Mountain goes forward. We believe the approach set forth here provides the best strategy for assuring continued progress, regardless of the fate of Yucca Mountain.
Unfortunately, combined with the Commission's lack of interest in endorsing alternative fuel cycle strategies such as partial or full recycling of long-lived actinides (such as the remaining uranium, plutonium, and minor actinide species which make up the bulk of spent fuel by mass), this leaves little in the way of any actual immediate solutions for spent fuel management. Instead, as I noted prior, what this simply amounts to is turning back the clock on the process - wiser, but nonetheless no further along.

Projected spent nuclear fuel discharges (courtesy of OCRWM)


The commission is of course correct that at the current rate, even were Yucca Mountain to open tomorrow, the nation would soon require a second repository, given the regulatory capacity (not the technical capacity) of the site. What thus  can be said in the commission's defense is that many of its recommendations would apply equally to any future repository required, even assuming Yucca Mountain were to open.


Estimated "wet storage" capacity at reactors, per the NRC. 
Indeed, spent fuel storage at reactors is a growing problem, made worse by the stalemate over Yucca Mountain. Coloring much of the report are concerns over the events at Fukushima, most especially in terms of managing spent fuel pools which are quickly reaching capacity.

Thus, concerns over waste management have begun to intersect with safety concerns, leading to an increase push for "dry storage" of older fuel. The safety concern is somewhat ill-placed, given that only older fuel (generally on the order of 5-10 years following final discharge) can be safely placed in dry storage (as the decay heat of such fuel is low enough to allow for air cooling). The fuel bundles which can be thus moved out of "wet storage" are thus not those at risk of damage in the event of a loss of coolant in the spent fuel pool; rather, any move to remove these bundles has more to do with lowering the total amount of radioactivity in the pool (as well as increasing safety margins in the pool) as well as making room for newer fuel being ejected from the core.

Yet dry storage is neither a substitute for wet storage ("younger", hotter fuel can't go into dry storage) nor a substitute for permanent disposal (dry storage casks, while being suitable for storage on the order of decades or more, is not designed to permanently isolate spent fuel from the environment and is subject to environmental attack).

However, all of this assumes no change from the once-through cycle, where only a fraction of the usable uranium is fissioned and the entire fuel assembly is thrown away with no further recovery of usable materials.

"Buying time" with interim storage

This is perhaps the most glaring flaw in the Commission's report; despite soliciting the testimony of numerous fuel cycle experts (and even in some cases, nuclear energy opponents), the capstone of their recommendations - centralized interim storage - amounts to a rather sophisticated way of simply buying time. In evaluating each of the technical solutions to nuclear waste management, the Commission declined to endorse any, concluding that interim storage leading to some form of geologic disposal is ultimately necessary:
We concluded that while new reactor and fuel cycle technologies may hold promise for achieving substantial benefits in terms of broadly held safety, economic, environmental, and energy security goals and therefore merit continued public and private R&D investment, no currently available or reasonably foreseeable reactor and fuel cycle technology developments—including advances in reprocess and recycle technologies—have the potential to fundamentally alter the waste management challenge this nation confronts over at least the next several decades, if not longer. Put another way, we do not believe that today’s recycle technologies or new technology developments in the next three to four decades will change the underlying need for an integrated strategy that combines safe, interim storage of SNF with expeditious progress toward siting and licensing a permanent disposal facility or facilities. This is particularly true of defense HLW and some forms of government-owned spent fuel that can and should be prioritized for direct disposal at an appropriate repository.
(Emphasis added).

A resonant theme throughout the report is the idea of "keeping one's options open" - in other words, avoiding any irreversible commitment to one technological choice, be it direct disposal or reprocessing. Hence one finds the conclusion for interim storage - a solution which is by its nature temporary. A key problem here however is that temporary solutions, while affording flexibility down the line, are also solutions which leave the issue still unresolved - the very problem which forced this crisis to begin with.

In fairness, the Commission found numerous technical and economic advantages to centralized interim storage, including reducing overall costs for security (especially compared to spent fuel stored at reactors which have been shutdown); the savings in comparison to on-site storage each reactor would make such a site largely self-financing, particularly given the cost of "orphaned" fuel at shutdown reactors. Additionally, centralized storage may afford certain new technical capacities such as mixing spent fuel assemblies in disposal packages in order to "even out" thermal loading in the repository. Finally, an interim storage site could easily be used as a staging area for both reprocessing or as a location to coordinate  final geologic disposal of assemblies.

So where exactly is the problem? The problem is in that this is it. Outside of recommendations for the process of repository siting, this is where the endorsements of technical solutions for nuclear waste management by the Commission end. Hence, the problem. One wonders why it took an entire commission of experts over a year to come to a set of solutions that, while helpful, have been already proposed by nuclear experts (including myself) for any number of years now.


To their credit, the Commission at least acknowledges the connection between interim storage and a credible process for establishing a repository, noting that the two activities cannot simply be carried out in isolation (particularly lest the centralized interim storage site be seen as a de facto permanent site).
Not that Deus Ex...


Yet much of their conclusion, and in particular their reluctance to endorse any of the suite of technological solutions for waste, implies waiting for some form of transformational technology whose technical and economic benefits solve their problem for them. Unfortunately, this is what folks in literature like to refer to as a "Deus Ex Machina" - in other words, a contrivance in which a divine entity swoops in and saves the hero from an otherwise insolvable crisis.

Overlooking incentives

One rather glaring omission in the Commisssion's report is an evaluation of the economic incentives "baked in" to current nuclear waste management policy. As of now, nuclear operators pay a $0.001/kWh fee to the federal government for each unit of electricity produced. While fine in theory (a "polluter pays" arrangement is certainly a forward-thinking way of handling such issues), this overlooks several perverse incentives such a policy produces by using a flat fee arrangement.

First is the linkage between the spent fuel and repository capacity. The overall capacity of a geologic repository is controlled chiefly by temperature - in other words, by the heat being produced by spent fuel rods. This in turn is linked to content of the rods - over the short term (i.e., the first 100 years following emplacement), the primary heat generators are radioactive cesium and strontium, each with half-lives of about thirty years. Thus, after about 100 years, the inventory of these isotopes (and subsequent heat) has decayed to roughly one-tenth of the original content. Over the extreme long-term (i.e., thousands of years), the heat capacity of the repository is controlled by long-lived actinides, specifically plutonium and americium. 

Were these species removed, technical studies have shown that the capacity of the repository could be increased ten to a hundred-fold in the same physical footprint, thereby eliminating the need for additional repositories. Thus, reprocessing spent fuel plays a critical role in such a planning process.

Yet the current fee structure does not charge based on the relative heat content of fuel (or, similarly, volume and total activity). There is thus no built-in incentive for operators to thus seek out ways to minimize these quantities - either through extended on-site storage (i.e., allowing time to do some of the work for them before shipping off waste for disposal) or reprocessing.

Additionally, because the fees are paid as power is generated, rather than when waste is disposed, the cost of disposal has already been "paid for" - and very few utilities (private or public) are so public-spirited as to pay twice for the privilege of waste management (such as paying for the cost of reprocessing fuel).

While uranium and plutonium can be recovered for re-use in spent fuel, reprocessing is expensive compared to mining and enriching new uranium from the ground; estimates show that the cost of raw uranium ore would have to rise appreciably - as much as ten times the current price - to make reprocessing competitive with mining an enriching new uranium. This of course frequently used as an argument by the opponents of reprocessing, but what this fails to account for is the cost of disposal; in particular, it is assumed the cost of disposing of waste is fixed. Yet this assumes after one repository fills, the next will be equally as inexpensive to locate and construct - a rather tenuous assumption. (Additionally, this line of argument neglects the consideration that fuel composes a tiny 10% of electricity costs for nuclear; thus, additional cost premiums for reprocessing are in essence a drop in the bucket.)

An alternative would be a pricing strategy which takes scarcity into account, which charges on the basis of total heat content (and potentially volume and activity) rather than in terms of electricity produced alone. Likewise, charging said fee at the time of disposal rather than immediately would encourage alternative solutions, from reprocessing to interim storage. (The issue of "stranded costs" could easily be handled as reactor decommissioning costs are now, where utilities are required to set aside funds during the operating life of the reactor to pay for its decommissioning and final disposal).

Missing the connection: nonproliferation

An additional point of emphasis in the BRC report is in the connection between the fuel cycle (specifically, waste management) and nonproliferation concerns. Nonproliferation has been (rightly or wrongly) at the fore of nuclear waste management decisions, from President Ford's temporary moratorium on domestic reprocessing, followed by President Carter's permanent shutdown, premised explicitly on nonproliferation concerns.

The BRC report correctly recognizes the linkage between waste management and nonproliferation, in particular the need for multilateral fuel cycle strategies that obviate the need for the spread of sensitive fuel cycle facilities (such as those for enrichment and reprocessing). While the topic of nonproliferation and the fuel cycle easily warrants its own post, in general a U.S. policy of fuel "leasing" (where fuel is enriched and manufactured here, leased to foreign reactors, and returned to the United States for final disposition) can be a vital tool in promoting a more proliferation-resistent fuel cycle cycle.

This argument is explicitly explored in the report; however, what is neglected is that absent a credible, permanent solution for waste, such a "fuel leasing" policy is politically dead in the water. Further, even assuming the development of a permanent repository, it is difficult to conceive of widespread public support for such a policy, given the limited availability of repository capacity.

This would be where the disconnect emerges; in order to credibly advance a fuel leasing strategy (thereby advancing nonproliferation goals), it is highly likely that some form of waste reduction would be required in order to minimize demands upon any given repository. In other words, half-measures such as interim storage are simply insufficient.

Conclusion

The BRC was obviously handed a rather trying and delicate task - trying to untangle three decades of U.S. nuclear waste management policy which had largely found its way into a dead-end. And while many of its instincts are admirable - such as advocating a strategy which is flexible and avoids technological lock-in, this philosophy is taken to an extreme, leading to paralysis in advocating a path forward. Instead, most of what the commission has produced is a call for additional breathing room - itself not bad, but a far cry from the long-term solutions required for spent fuel management.

While a rethought process for siting a geologic repository may fill some of this role, the Commission's reluctance to endorse any technological solutions to waste management (or a clear decision framework for adopting such a technology) is perhaps the report's most glaring shortfall.