تجزیه و تحلیل هزینه تاسیسات بازفرآوری سوخت هسته ای صرف شده ایالات متحده آمریکا

The US Department of Energy is actively seeking ways in which to delay or obviate the need for additional nuclear waste repositories beyond Yucca Mountain. All of the realistic approaches require the reprocessing of spent nuclear fuel. However, the US currently lacks the infrastructure to do this and the costs of building and operating the required facilities are poorly established. Recent studies have also suggested that there is a financial advantage to delaying the deployment of such facilities. We consider a system of government owned reprocessing plants, each with a 40 year service life, that would reprocess spent nuclear fuel generated between 2010 and 2100. Using published data for the component costs, and a social discount rate appropriate for intergenerational analyses, we establish the unit cost for reprocessing and show that it increases slightly if deployment of infrastructure is delayed by a decade. The analysis indicates that achieving higher spent fuel discharge burnup is the most important pathway to reducing the overall cost of reprocessing. The analysis also suggests that a nuclear power production fee would be a way for the US government to recover the costs in a manner that is relatively insensitive to discount and nuclear power growth rates.

Nuclear power accounts for 20% of the electricity production in the United States and concerns over global warming and energy independence have rekindled calls for an increase in its use (National energy policy, 2001). The current US fleet of light–water reactors (LWRs) produces around 2000 tonnes of spent fuel (SF) heavy metal each year all of which is destined for interment at Yucca Mountain along with the existing inventory of stockpiled SF. However, at current production rates the expected capacity of this repository will be met by 2010 (Richter et al., 2002, Schneider et al., 2003 and Xu et al., 2005). While appropriate engineering could increase the amount of SF that can be stored safely at Yucca Mountain, it is unlikely that the repository could handle more SF than that anticipated from the LWRs that are in operation today2 (Richter et al., 2002 and Schneider et al., 2003). Because of this, a 1987 amendment to the US Nuclear Waste Policy Act mandates the Secretary of Energy to report on a site for a second repository by 2010 (Nuclear Waste Policy Amendments Act, 1987). However, the difficulties encountered with opening Yucca Mountain have led the US Department of Energy (DOE) to seek strategies that would significantly delay, or even eliminate, the need for further geological disposal sites. For this reason it is prudent to consider the costs of reprocessing SF produced at 2010. The capacity of Yucca Mountain is limited by the thermal and radiological output of the materials that will be interred (DOE, 2005a). Because of this, considerable attention has been given to developing methods for transmuting the long lived radioisotopes that are contained in LWR SF into more benign or shorter lived forms. All of the plausible methods for doing this involve recycling these isotopes through a nuclear reactor. Depending on the technologies that will be employed for this purpose, the capacity of Yucca Mountain (or a repository of similar design) could be extended by orders of magnitude (Richter et al., 2002). Central to this approach is the ability to reprocess LWR SF in order to extract the requisite isotopes for recycle. At present, the US has no facilities that are capable of doing this on an industrial scale and a number of recent reports suggest that it would be advantageous to delay construction of such facilities for economic reasons (e.g. Anolabehere et al., 2003). Reprocessing facilities built in the US will very likely be financed and operated by the federal government (National Research Council, 1996, pp 430). As a result, the US congress has mandated that a significant benefit must be achievable from reprocessing based fuel cycles by 2100 in order for federally funded R&D to continue. In response the DOE has set a goal of achieving sustained recycle of transuranics by 2100 and this will require that all SF discharged between 2010 and 2100 be reprocessed. The cost of doing this is poorly understood and depends on the times at which the required infrastructure is built, becomes operational, the time at which reprocessing of SF must be completed, as well as the time at which associated facilities are decommissioned. Until the required facilities are in place, the inventory of SF, and the required interim storage capacity, will continue to increase as will the capacity of the required reprocessing facilities. Reprocessing costs are therefore a function of their deployment time: the sooner the facilities are put in place, the smaller they can be, but the higher the discounted value of their capital expenditures and the longer that they incur operational expenses. The present contribution analyses the minimum cost of opening, operating and decommissioning a US governmental facility that would reprocess spent nuclear fuel, discharged between 2010 and 2100, under a best case scenario in which all facilities operate at 100% capacity with no private financing required. The costing model depends on the time at which infrastructure is deployed, intergenerational discount rate, demand growth for nuclear power, plant life, spent fuel burnup (i.e. amount of energy that is liberated from a unit mass of nuclear fuel) and the unit costs associated with reprocessing and decommissioning.

The cost impact of delaying the deployment of a reprocessing facility was found to be minor. Postponing deployment by ten years, from 2020 to 2030, increase the discounted reprocessing system costs by 2.5%, which is in contrast to the conventional thinking that delaying the deployment of reprocessing infrastructure will reduce its discounted cost. Previous cost estimates have used a relatively high time value of money, whereas an intergenerational discount rate of about 2% more accurately reflects the long-term, sustained nature of the SF disposition effort. • The discounted systems cost of the first reprocessing facility is $622/kgHM and $760/kgHM for plants with 40 with a 30 year service lives, respectively. These reprocessing costs are about 25% below those that have been reported for the THORP facility when adjusted for inflation. However, the THORP facility operated as a commercial enterprise, whereas the figures given here represent “at cost” reprocessing in which all facilities operated at 100% capacity and no private financing was needed. • The back end system cost, in mills/kWh(e), is not strongly dependent on either the nuclear power growth nor the discount rates. Within the space of growth rate between 0.5% and 2.5% per year and the discount rate between 0.005 and 4.0% the cost of reprocessing, in mills/kWh(e), varies by less than 15%. • The discharge burnup of LWR fuel was found to strongly affect the reprocessing system costs. In fact, the systems cost is almost directly proportional to discharge burnup, with a 10% increase in fuel burnup leading to a slightly greater than 10% cost savings. This results because better energy extraction per unit mass of fuel leads to fewer tons of fuel being discharged per year and a smaller infrastructure for all aspects of the back end systems. • Regardless of deployment scenario, it will be difficult to attain a back-end cost that could be covered by the 1 mill/kWh(e) charge currently being charged to utilities. To achieve such a low cost, fuel discharge burnup would have to increase considerably and construction and operating costs would need to be improved from the levels achieved at La Hague and THORP.