Radwaste management

No limits for Yucca mountain?

20 February 2009

The USA needs a solution to deal with its spent nuclear fuel and high-level waste arising beyond 2010. Will this be the removal of the cap on Yucca Mountain? By Claire Maden

Former US energy secretary Samuel W Bodman formally called for prompt action from Congress to remove the arbitrary statutory limit of 70,000 tonnes of heavy metal (tHM) imposed on the Yucca Mountain repository to defer the need for a second geologic repository in the USA.

A US Department of Energy (DoE) report on the likely need for a second repository, required under the 1982 US Nuclear Waste Policy Act (NWPA), has considered three alternative scenarios for dealing with spent fuel generated beyond 2010: remove Yucca Mountain’s statutory limit; site and build a second repository; or prolong the storage of spent fuel at reactor sites.

The NWPA, as passed in 1982, set out the process for the siting, construction and operation of one or more national repositories for the permanent disposal of the country’s spent nuclear fuel and high-level radioactive waste. Nine potential sites were identified and studied in the 1980s. A 1987 amendment to the act saw Yucca Mountain in Nevada selected as the only site for further study for the first national geologic repository, and the site’s approval was formally signed into law in 2002. The NWPA also stipulated that a report on the need for a second repository be presented to Congress between 1 January 2007 and 1 January 2010.

Bodman summarised the findings of the study succinctly in: The Report to the President and the Congress by the Secretary of Energy on the Need for a Second Repository, published in December 2008. “Unless Congress raises or eliminates the current statutory capacity limit of 70,000 metric tonnes of heavy metal, a second repository will be needed,” he said.

Two principal types of waste will be disposed of in Yucca Mountain: commercial spent nuclear fuel from power reactors, and DoE’s own spent nuclear fuel and high-level waste (HLW). DoE’s waste inventory is made up of the spent fuel accrued over the years from: government weapons programmes, research reactors, prototype reactors and nuclear powered naval vessels; and HLW from the reprocessing of spent fuel. The total DoE inventory currently stands at approximately 12,800tHM, already in excess of the 7000tHM allocated for it at Yucca Mountain, although with the exception of naval spent fuel the DoE inventory is not set to increase materially.

The inventory of commercial spent fuel from the country’s 104 operating power reactors plus 14 that have closed down currently stands at almost 58,000tHM, and is increasing by about 2000tHM per year. The inventory of civilian spent fuel is therefore set to exceed the 63,000tHM of Yucca Mountain capacity allocated to it by 2010 – even before possible life extensions to existing reactors, which could see the total inventory rise to around 130,000tHM (see graph). These projections, notes the DoE, do not take into account any waste arising from the operation of possible new reactors, even though construction and operating licence applications planned or pending for 34 new reactors in the USA.

The DoE filed an 8600-page construction licence application for Yucca Mountain with the Nuclear Regulatory Commission (NRC) in June 2008. As NRC’s review is anticipated to take four years, construction is unlikely to begin before 2013 at the earliest, with March 2017 the best-achievable startup date for receiving spent fuel.

Plenty of space

The NWPA as it stands places a statutory capacity limit of 70,000tHM on Yucca Mountain. However, the amount of waste that Yucca Mountain could actually accommodate would depend on the repository design: the heat load introduced into the rock mass from the waste and the volume of rock of sufficient quality to meet the design constraints. The repository layout as currently planned encompasses some 1250 acres but a total of 9500 acres of potential emplacement areas are available at the site. In addition, recent thermal loading studies have shown that the allowable thermal load is greater than the 55-70tHM/acre value currently used in calculations, and that significantly greater thermal loads could be accommodated by extending the time the repository is open and ventilated before final closure. An independent study published by the Electric Power Research Institute (EPRI) in 2006 concluded that the actual available physical disposal capacity at Yucca Mountain could accommodate at least four times that amount. Further site characterisation could potentially extend the capacity to as much as nine times the statutory limit.

The report limits its conclusions to projections of waste based on assumptions reflecting current US policy – that is, direct disposal of spent fuel. However, it notes that under a scenario of future nuclear growth, the use of reprocessing would not only extend the use of the Yucca Mountain and any second repository but could also offer opportunities for increased operational efficiencies and construction and operation costs.

What about the alternatives?

As already noted, removing the statutory 70,000tHM limit is one of three alternatives considered in the report, the other options being: beginning the process of siting, designing, licensing and building a second repository as soon as possible in order to be ready for the time when the statutory limit at Yucca Mountain has been reached; or deferring the decision altogether by prolonging the time that spent fuel and high level waste is stored at reactor sites and DoE sites.

Launching the siting process for a second repository would be fraught with legal issues. Only the first repository is authorised under the NWPA, so specific authorisation would be needed for a second repository; furthermore, the NWPA limits use of the Nuclear Waste Fund – the financing set aside for managing nuclear waste raised by a levy on nuclear power generation – to legally authorised facilities. The terms of the NWPA and the 1987 amendments making it specific to Yucca Mountain mean that it does not provide for the siting and licensing process for a second repository, so legislation would be needed to define these. The report calculates that a second repository would need to be operational by 2041 to enable DoE to continue accepting waste without disruption once Yucca Mountain reaches the 70,000tHM emplacement limit. This means that the siting process for a second repository would need to begin in 2011. This would require Congressional action to establish the siting process and provide the necessary funding by 2010.

Were Congress to choose to authorise a second repository programme, it would have recourse to the nine potential sites identified in the early 1980s before the NWPA was amended. These sites are spread over six states (see table). However, the original first and second repository programmes identified potential sites, or areas that could be evaluated as potential sites, in a total of 31 states, and a new siting process could further widen the types of geologic media and areas considered, meaning that all the states in the contiguous USA have a potential area that could be considered for a second repository. Finding a geologically suitable site, therefore, ought not to be a problem.

Defer the decision?

The final option – the indefinite deferral of the decision to build a second repository – would raise a number of significant issues. Without the removal of the 70,000tHM cap on Yucca Mountain, the deferral option would essentially mean that all spent fuel arising from US nuclear power plants after 2010 would have to be stored on site until a second repository was available.

The DoE’s failure to begin accepting spent fuel for disposal from utilities by the beginning of 1998, as required under the terms of the NWPA, has already led to court cases and awards of damages to utilities, and deferring a decision would likely result in further liabilities. DoE estimates that its liabilities associated with the delay in waste acceptance at Yucca Mountain alone could stack up to $11 billion by the time all the spent fuel is received at the first repository, assuming a 2020 startup. The Nuclear Waste Fund cannot be used to compensate utilities for their onsite storage costs so the bill for damages must ultimately be met by taxpayers.

Putting off the decision would also increase uncertainties about the DoE’s waste inventory in excess of the 7000tHM portion currently allocated to it at Yucca Mountain. The exact nature of waste conditioning to prepare it for disposal, such as solidification of liquid HLW, depends on the characteristics of the repository site and its design, but uncertainty over where and how the waste will ultimately be disposed of complicates such decisions. This in turn adds to costs of management at the sites where the waste is currently stored as well as further complicating DoE site cleanup and decommissioning.

Remove the limit, buy time

Plainly, the situation as it stands is pretty much untenable. While Yucca Mountain’s 70,000tHM limit remains in place a second repository will be needed. However, lifting the limit would provide the chance to defer a decision on future repository requirements. This would provide a breathing space during which the future growth of nuclear energy in the USA, plus impacts from future decisions on spent fuel recycling, as are being addressed under the remit of the Global Nuclear Energy Partnership (GNEP) initiative, will become clearer. In turn, this will enable a more informed decision on a second repository to be made at a later date.

Sites identified in the first repository screening programme in the early 1980s
Site - Geologic media

Vacherie Dome, Louisiana - Dome salt
Cypress Creek Dome, Mississippi - Dome salt
Richton Dome, Mississippi - Dome salt
Yucca Mountain, Nevada - Tuff
Deaf Smith County, Texas - Bedded salt
Swisher County, Texas - Bedded salt
Davis Canyon, Utah - Bedded salt
Lavender Canyon, Utah - Bedded salt
Hanford Site, Washington - Basalt flows

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