Dear Matt,

Thank you for your query and for bringing up apple-to-apple comparison. Nuclear energy produces waste as byproduct of electricity generation, whereas solar PV and wind energy have no byproducts. Hence, full life cycle comparison is the only way to accurately compare carbon footprint of energy generation technology, and that means adding contribution of GHG emissions from decommissioning to the GHG emissions from material cultivation and fabrication, construction and operation.

Decommissioning of both wind energy and solar PV entails deconstruction process, disposal, recycling, and land reclamation where possible. According to meta-survey by Nugent and Sovacool, Wind energy emits 0.4 g CO2-eq/kWh to 364.8 g and a mean of 34.11 g, and Solar PV emits 1 g CO2-eq/kWh to 218 g and a mean of 49.91 g. These values include contribution of decommissioning, and it was found that recycling step mitigated GHG emissions by 19.4% for wind and 3.3% for solar PV. Assessing the lifecycle greenhouse gas emissions from solar PV and wind energy: A critical meta-survey, Energy Policy 65:229–244 · February 2014 (133 citations). 

https://www.researchgate.net/publication/259513614_Assessing_the_lifecycle_greenhouse_gas_emissions_from_solar_PV_and_wind_energy_A_critical_meta-survey

Nuclear power plant decommissioning entails managing non-radioactive waste disposal/recycling and temporary, long-term, and permanent radioactive waste storage after electricity generation and facility lifetime.

International Atomic Energy Agency or IAEA has approved three acceptable means of decommissioning: (i) immediate dismantling of facility enabling facility shutdown within a few months with immediate site availability for reuse or complete decommissioning, (ii) Safe storage of the facility that configures the reactor to store spent fuel for 40 – 60 years, after which the facility can be dismantled and decontaminated, and (iii) entombment of the facility (of smaller section of the facility) where the radioactive material can remain permanently in the facility until all radioactivity dies down (thousands of years) while this facility remains under surveillance and monitoring.

International Atomic Energy Agency (IAEA). 2000. Preparing for the End of the Line-Radioactive Residues from Nuclear Decommissioning. By Dennis Reisenweaver and Michele Laraia 

https://www.iaea.org/sites/default/files/42305085154.PDF

U.S. does not have nuclear waste recycling facility hence recycling is not an option. Therefore, the spent fuel is cooled in cooling tanks for 5 to 10 years before entombing it in dry casks made of steel and concrete, and (the casks) are designed to resist earthquakes, projectiles, tornadoes, floods, temperature extremes etc. Literally tons of steel and concrete is used to wrap up nuclear waste, and these facilities are under surveillance and monitoring.  Currently there are 60 sites in 34 states housing these casks under general license and 15 sites with specific licenses. 

https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/radwaste.html

https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/dry-cask-storage.html

Back to GHG emissions estimation.

My point is that the life cycle GHG emissions values are not valid for United States. Here is why…

Warner and Heath in their research and analysis publication entitled Life Cycle Greenhouse Gas Emissions of Nuclear Electricity Generation: Systematic Review and Harmonization, 2012 (70 citations) compiled a list of 99 unique scenarios of life cycle analysis (LCA) from 27 publications (down-selected from 274 publications for data quality control). They refined the GHG emissions estimates (median: 13 g CO2-eq/kWh, interquartile range (IQR) or range between 25 percentile and 75 percentile: 23 g CO2-eq/kWh, and range: 220 g CO2-eq/kWh) using harmonizing methods to new values of 12 g CO2-eq/kWh (mean), 17 g CO2-eq/kWh (IQR), and 110 g CO2-eq/kWh (range).

https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1530-9290.2012.00472.x

and supplemental information 

https://onlinelibrary.wiley.com/action/downloadSupplement?doi=10.1111%2Fj.1530-9290.2012.00472.x&file=JIEC_472_sm_suppmat.pdf

Here are some observations (based on Table 1 of the publication) and my questions / comments (Q /C).

Out of 99 unique scenarios …

1) 22 scenarios were from existing case studies, 33 hypothetical and 44 scenarios were for proposed future technologies. Meaning only 22% real data.

Q/C. What are the chances of hypothetical and proposed future technologies being adopted in the near future, and does it make sense to include their contribution (of 78% scenarios) in today’s LCA calculation? And if yes, how can their future contribution be accurately represented in today’s LCA calculation?

2) Life cycle analysis was performed using either process chain analysis (PCA) or hybrid method which is a mix of PCA and economic input-output analysis (EIO). The EIO methodology uses activities in our economy to estimate the materials and energy resources required, and the environmental emissions resulting from these resources. http://www.eiolca.net/  

Q/C. The accuracy of LCA from hybrid methodology is questionable as the number of parameters would vary with case by case basis. What is the guarantee that all relevant parameters were considered and given appropriate weightage? Per Jon von Neuman “With four parameters I can fit an elephant, and with five I can make him wiggle his trunk.” https://www.johndcook.com/blog/2011/06/21/how-to-fit-an-elephant/ 

3) LCA was performed using PCA methodology in 46 scenarios, and 53 scenarios used hybrid methodology.

4) 41/46 scenarios evaluated by PCA used empirical data, whereas 40/53 scenarios evaluated using hybrid methodology used theoretical data.

Q/C. Is hybrid methodology coupled with theoretical data compounding the uncertainties or diminishing them?

5) 37/40 scenarios from Europe (from 8 entities: Belgium, EU, Finland, France, Germany, Sweden, Switzerland, UCTE) reported PCA based LCA using empirical data. (UCTE ref. https://www.ucte.org/_library/systemadequacy/saf/UCTE_SAF_2007-2020_presentation.pdf)

6) Out of the 53 (hybrid + theoretical data based) scenarios, 25 were reported from Australia and 22 from Japan.

Q/C. Is heavy contribution (47%) from two countries (Australia and Japan) distorting the data set?

7) A total of 8 scenarios were reported for U.S., all were hypothetical cases, and of these 5 cases were evaluated using PCA and 3 using hybrid methodology.

Q/C. Is the nuclear energy scenario in the U.S. represented in a meaningful manner?

The authors clearly state under Limitations of Analysis (page 16)

“* Decommissioning was not usually described in detail; when described, most seem to closely resemble only “immediate dismantling,” not full decommissioning (see the Downstream Processes section of the supporting information on the Web).

*Mine rehabilitation, which may be associated with a significant portion of GHG emissions (Beerten et al. 2009), was rarely discussed and never evaluated in any LCAs passing screens.”

As mentioned earlier, U.S. does not have recycling capabilities hence the third option (entombment of the facility) is being used in this country and has significant GHG footprint given that both steel and cement industries are notoriously polluting.

https://www.globalefficiencyintel.com/s/How-Clean-is-the-US-Steel-Industry-11202019.pdf

https://www.globalefficiencyintel.com/s/Decarbonization-Roadmap-CA-Cement-Final-Spet-2019.pdf

 A comparison of the mean, interquartile range and range for existing case power plant scenarios evaluated using PCA (that used empirical data) with hypothetical and proposed future technologies scenarios evaluated using hybrid methodology (using theoretical data) would be a worthwhile next step. One of the authors, Dr. Ethan Warner from NREL (ethan.warner@nrel.gov) perhaps could help with this effort.

Hello Gary,

Please see my reply to Matt Chester's query. Hopefully that has answers to your query. Thank you.