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Can reactors react? Is a decarbonized electricity system with a mix of fluctuating renewables and nuclear reasonable?

AuteurC.Morris, IASS
Datumjanuari 2018

Uit de publicatie:

Can reactors react?
Is a decarbonized electricity system with a mix of
fluctuating renewables and nuclear reasonable?
Craig Morris

Institute for Advanced Sustainability Studies (IASS)
Potsdam, January 2018

In Nov 2017, the French government postponed its plan from 2015 to reduce the 
share of nuclear from 75% to 50% because it did not believe it could replace 
the missing 25% with renewables alone; power from natural gas would be needed, 
thereby increasing carbon emissions. One aspect remains overlooked in the 
French discussion: the potential inability of the country’s reactor fleet to 
ramp enough in order to make space for significant shares of wind and solar 
power. This oversight is typical of the current discussion about low-carbon 
power scenarios in English as well – but not in German.1
“Deep decarbonization” has become a buzzword in the energy sector in recent 
years. How can we achieve a low-carbon energy supply? Mobility is expected to 
be increasingly electric, as will heating and cooling. The power sector will 
therefore be more important. Nuclear power is a source of very low-carbon 
electricity. Yet, markets are focusing on wind and solar, and there are signs 
that the priority given to them is hurting the profitability of baseload plants, 
including nuclear. Recent academic studies focusing on climate change mitigation 
have therefore argued that nuclear should be included along with wind and solar 
towards creating the most affordable clean power supply.
Germany’s nuclear phaseout is partly based on an understanding that baseload 
cannot flexibly accommodate fluctuating wind and solar,2 with nuclear being the 
least flexible of all conventional options. A discussion about this “inherent 
conflict” (Systemkonflikt) took place roughly from 2008-2011; the second phaseout 
of 2011 put an end to the debate. That phaseout also marked the point when 
Germany became the focus of international attention; the previous discussion in 
Germany about the flexibility of nuclear thus went largely unnoticed abroad. 
This paper summarizes that debate, possibly for the first time in English. 
Those calling for a “balanced” mix of nuclear, wind, and solar assume that 
nuclear reactors can ramp up and down sufficiently to back up wind and solar – 
when the subject of nuclear load-following is mentioned at all. In a 2016 final 
report on a symposium entitled “Getting to Deep De-carbonization: What Role for 
Nuclear Power?”, the Bulletin of the Atomic Scientists does not use the words 
“flexible” or “capacity factor” at all. Ramping and load-following were 
apparently not discussed (Stover 2016). 
This omission stands in stark contrast to the focus of the TAB study from 
Germany discussed below.