Many people are advocating fission-based nuclear power plants as a favored approach to producing electrical power without emitting greenhouse gases.  Unlike renewable energy systems such as wind turbines and solar photovoltaic systems, fission reactors can generate power around the clock, and can easily adjust power production up or down to meet demand at the time.  Nuclear power plant technology has evolved since the early forms of power generating reactors.   These were developed from designs originally created to produce fuel for nuclear weapons and to propel naval ships and submarines.  Many of the safety issues raised by major accidents such as Three Mile Island, Chernobyl, and Fukushima have been addressed by more modern reactor designs.  The new reactor designs are unquestionably safer and more secure in their operation than previous designs.  New power reactor designs include modular configurations that can be sized up or down to better meet the needs of a location.  Some new designs use thorium fuel rather than enriched uranium.

However, a whole-systems perspective on nuclear power plants raises a number of concerns for using this approach as a means to avoid the adverse climate impacts of producing grid electrical power.  In particular, it is critical to consider the entire life cycle of a nuclear power system from cradle to grave when evaluating how “green” such a system actually is.

1. The creation of the nuclear fuel typically involves the consumption of large amounts of energy from non-renewable sources. This occurs particularly in the mining and refining of the uranium ore and the enrichment of the uranium fissionable isotope mix to the levels required by power plants.
2. The construction of the nuclear power plants themselves also typically involves the consumption of large amounts of non-renewable energy. This is needed to produce the steel and concrete materials used in the plant and to build the plant itself.
3. Nuclear power plants typically require access to large amounts of water for cooling. Plants situated in coastal areas are likely to be affected by sea level rise, and plants placed next to rivers will take the water and largely evaporate it into the atmosphere for the cooling cycle.  As a result, the water is unavailable for other uses, at a time of severe freshwater shortages.
4. Nuclear power plants have a limited life, at which point they must be dismantled and the plant’s radiation-damaged materials disposed of. The time and cost to dismantle a nuclear power plant can be considerably greater than the time and cost to build it in the first place, and a good deal of non-renewable energy is likely to be used in the deconstruction process.
5. Considering all these factors, a study published in 1988[1] concluded that a large nuclear-power regime, involving a continuing construction program of starting one new 1000-MW system each month for 100 years, would yield a relatively small amount of net energy, even under optimistic assumptions. Under less-optimistic assumptions the net-energy yield is negligible to negative. While this study is admittedly quite old now, the principles used in the computation appear to remain relevant and viable today.

There are a number of other factors besides end-to-end net energy production that should be considered when evaluating nuclear power plants for non-fossil fuel based electrical energy generation.

1. Nuclear power plants actually depend on external electrical power to be maintained while they are not generating power themselves. This power is required to keep the pumps for cooling water operating, both inside the reactor and in the cooling ponds where used reactor fuel rods are stored for many years while their radioactivity declines.  While the plants have backup fossil-fuel powered generators for periods when the grid is down, the amount of fuel stored on site is typically only sufficient for a relatively short time.  If the cooling is interrupted for any substantial period, catastrophic effects can occur.  This is particularly true if the cooling ponds go dry and the cladding on the fuel rods catches fire.  This can result in the release of large amounts of high level radioactivity to the atmosphere.  There are a number of scenarios where the provision of grid power to a nuclear power plant could be interrupted for an extended period–for example as a result of a cyber attack on the grid system or a severe solar flare event that knocks out grid control electronic systems.
2. The problem of permanent safe storage of high-level radioactive waste has never been adequately solved. To date, no repositories for such wastes have been created in the United States.  High-level radioactive wastes need to be actively managed for centuries, even millennia, in order to be safe.  It is unclear that management over such a period can be guaranteed with any confidence.
3. Nuclear power plants require a large cadre of highly-trained personnel to manage, operate, maintain, and repair the systems. Bad things will happen if these personnel are not available when necessary, for example as a result of disease pandemic conditions.  Nuclear power plants are examples of systems that must be attended and managed continuously, as they cannot simply be put into a safe state and left alone for an extended period.
4. Nuclear power plants need to have exceptionally strong protections against cyberattacks. Up to now, cybersecurity of nuclear power plants has not received sufficient attention to provide adequate safety.  There are many cyber exposures presented by existing nuclear power plant designs.
5. Nuclear power plants are particularly dangerous targets for physical attack, by either conventional or nuclear explosives. They are difficult-to-impossible to harden sufficiently that their security can be guaranteed.  Damage from a major physical attack may not be recoverable.

My perception is that the advocates for nuclear power as a major component of the energy production portfolio for “green energy” are obscuring many of the reasons for being cautious about this option.

[1] The net-energy yield of nuclear power, by GeneTynerSr¹ RobertCostanza² Richard G.Fowler³

^a Oklahoma Institute for a Viable Future, P.O. Box 2607, Norman, OK 73070, U.S.A,^b Coastal Ecology Institute, Center for Wetland Resources, Louisiana State University, Baton Rouge, LA 70803-7503 U.S.A. ^c University of Oklahoma, 1309 Avondale, Norman, OK 73069, U.S.A.  Published in the journal Energy, Elsevier, Volume 13, Issue 1, January 1988, pp. 73-81.