By Arjun Makhijani, Ph.D. and M.V. Ramana, Ph.D.
Small modular nuclear reactors, or SMRs, are designed to generate less than 300 megawatts of electricity – several times less than typical reactors, which have a range of 1,000 to 1,600 MW. While the individual standardized modules would be small, plans typically call for several modules to be installed at a single power generation site.
The nuclear industry and the U. S. Department of Energy are promoting the development of SMRs, supposedly to head off the most severe impacts of climate change. But are SMRs a practical and realistic technology for this purpose?
To answer, two factors are paramount to consider – time and cost. These factors can be used to divide SMRs into two broad categories:
Economics and scale
Nuclear reactors are large because of economies of scale. A reactor that produces three times as much power as an SMR does not need three times as much steel or three times as many workers. This economic penalty for small size was one reason for the early shutdown of many small reactors built in the U.S. in the 1950s and 1960s.
The SMR track record so far
The track record so far points to the same kind of dismal economic failure for SMRs as their larger cousins. Figure 2 shows the capital cost escalation for the proposed NuScale reactor and actual costs of two foreign SMRs. As a result, the total cost of a proposed project in Idaho using the NuScale design has already risen from around $3 billion, in 2015, to $6.1 billion, in 2020, long before any concrete has been poured.
Lazard, a Wall Street financial advisory firm, estimates the cost of utility-scale solar and wind to be about $40 per megawatt-hour. The corresponding figure for nuclear is four times as high, about $160 per MWh – a difference that is more than enough to use complementary technologies, such as demand response and storage, to compensate for the intermittency of solar and wind.
SMRs and the climate crisis
The climate problem is urgent. The IPCC and other international bodies have warned that to stop irreversible damage from climate change, we need to reduce emissions drastically within the next decade. The SMR contribution in the next decade will be essentially zero. The prospects for SMRs beyond that are also bleak, given that entire supply chains would need to be established after the first ones have been built, tested and proven in the field.
Water use is another concern that is expected to intensify in the future. Nuclear plants have very high water withdrawal requirements. A single 300 MW reactor operating at 90 percent capacity factor would withdraw 160 million to 390 million gallons of water every day, heating it up before discharge. Reducing the demand for water by using air cooling will require the addition of a tower and large electric fans – further raising the construction cost and reducing output of electricity by up to 7 percent of the capacity of the reactor.
Finally, SMRs will also produce many kinds of radioactive nuclear waste, because the reactors are smaller in physical size and because of refueling practices adopted for economic reasons. SMRs based on light water designs, such as NuScale, will also produce a larger mass of nuclear waste per MWh of electricity generated. The federal government is already paying billions of dollars in fines for not fulfilling its contractual obligations to take possession of spent fuel from existing reactors. The legislative plan in the 1982 Nuclear Waste Policy Act was for a deep geologic disposal repository to open in 1998. After nearly four decades, that plan has come to naught.