Add nuclear about sector-coupled-euro-calliope HOT 3 OPEN

Since there are a few countries with capacity ranges, I plan to allow construction of capacity in those ranges with costs from this DIW report. Which would be:

investment: 4500 USD2018/kW (similar to the European mean collated in this study and the value used for 2040 from the IEA's world energy model)
annual O&M: 93,280 USD2018/MW/year
om_prod(?): 2.14 USD2018/MWh
om_con: 10.11 USD2018/MWh
capacity factor: 0.85 (0.75 in IEA's world energy model)
lifetime: 40 years (60 years according to Barkatullah and Ahmad)

The IEA's world energy model gives a 2040 fuel + O&M cost of 35 USD2017/MWh. Distributing the annual O&M to MWh based on a capacity factor of 0.75, and the fuel cost to produced electricity (40% energy_eff) would lead to the DIW fuel + O&M being ~41 USD2018/MWh, which is a 17% higher than used by the IEA for 2040, but is in line with that given in the IEA projected cost of generating electricity 2020. The projected costs give annual O&M of 85,000, om_prod of 1.5 and om_con of 10.33, giving 40 USD(2019?)/MWh, assuming a 0.75 capacity factor and 40% energy_eff.

The 17% difference between the WEM and other sources doesn't seem to be related to the reference year, since the WEM also uses this lower price in 2019. The DIW report refers to Barkatullah and Ahmad for its O&M and fuel costs; the latter does not cite any sources for the cost assumptions used. However, given a lack of alternative sources, and the similarity between total costs from Barkatullah & Ahmad and IEA projected cost of generating electricity 2020, I plan to use this data, amounting to (assuming 1USD2018->0.85EUR2018 and 1EUR2018->0.96EUR2015):

energy_cap: 3,672 EUR2015/kW
annual O&M: 76,116 EUR2015/MW/year
om_prod(?): 1.75 EUR2015/MWh
om_con: 8.25 EUR2015/MWh
capacity factor: 0.75-0.85 (set as a constraint)
lifetime: 50 years

from sector-coupled-euro-calliope.

BEIS gives another source of costs for the 2025 model year:

energy_cap: 3700-5100 GBP/kW
annual O&M: 72,900 GBP/MW/year + 10,000 GBP/MW/year (insurance)
om_prod: 5 GBP/MWh (no indication of whether it includes fuel)
capacity factor: 0.9
lifetime: 60 years

These are higher than the costs I intend on using.

from sector-coupled-euro-calliope.

Following discussion in calliope-project/euro-calliope#226, the fuel prices will be updated to relate to electricity output (om_prod), not input (om_con).

from sector-coupled-euro-calliope.