Electricity generated by fossil fuels in Great Britain drops to record low

The tariff for cooperating countries is 0%. The tariff for non cooperating countries is set appropriately for the estimated carbon content of the import or higher.

You're totally right that it's a relatively poor metric, but assuming we agree it's unlikely that the energy companies actively 'gamed' the metric (e.g. by agreeing to shut down gas and coal generation for that hour) it's still better to have that result, than to not have it.

Sorry but that’s not true:

Show me an academic source (a study and please no website that claims something with no sources) that claims nuclear power is carbon neutral. Just look at the 2(!) meta-studies that led to an estimated range of 3.7 to 110 grams of CO2 equivalent per kilowatt-hour (kWh) in IPCCs AR5 2014.

It's long been assumed that nuclear plants generate an average of 66 grams of CO2/kWh — (some studies believes the actual figure is much higher). New power plants, for example, generate more CO2 during construction than those built in previous decades, due to stricter safety regulations. Look at the statement in IPCC 2014 and the (self)critical statements of the authors. And then think again why even the IPCC keeps nuclear power relatively small.

> The ramp up and ramp down issue is handled by pairing nuclear power with storage, the same kind of storage that renewables uses.

That means they avoid ramp up and downs? Believe me, load-following power plants are very complex:

Is the operation of nuclear power plants compatible with renewable energy expansion plans? To assess whether the continued operation of nuclear power plants is compatible with the planned expansion of electricity generation from renewable energies, a model-based analysis of the future generation system was conducted. This analysis used framework data (including future electricity demand, energy carrier prices, and renewable energy expansion path) based on the assumptions used in the scenarios for the federal government's energy concept (Prognos/EWI/GWS 2010) and in the lead study of the Federal Ministry for the Environment, Nature Conservation, and Nuclear Safety (BMU) (DLR/IWES/IfnE 2010). Through minimizing the overall system costs for power plant and storage expansion, a power plant park was simulated for the model years 2020, 2025, and 2030. The combined operation of nuclear power plants, fossil fuel power plants, and renewable energy facilities was analyzed using an electricity market model. Based on the previously described technical possibilities for load-following operation of nuclear power plants, three possible future operating strategies were defined and examined in the scenarios: Conditionally flexible operation: This allows routine load change cycles of 100-50-100 (PWR) or 100-60-100 (BWR), meaning the minimum load of 50% (PWR) or 60% (BWR) of the nominal output is not undercut. This operating strategy has already been tested in some German nuclear power plants. Flex20 operation: It is assumed that nuclear power plants can also flexibly operate in the lower load range. For PWR, 20% was set as the minimum load level, as suggested by operating manuals. For BWR, based on expert discussions, 40% was assumed as the minimum load. Flex0 operation: Additionally, short-term downtimes are allowed. To take into account start-up and shut-down times, a minimum downtime of 3 hours and a minimum operating time of 1 hour were established.

As a measure of the flexibility of the conventional power plant fleet (including nuclear power plants), the amount of renewable energy (RE) electricity that needed to be curtailed was used for the various scenarios. The results for the model year 2030 are summarized below. The RE share of electricity generation here is – analogous to the BMU lead study – about 65%. The reference case is the scenario without extending the operating life of nuclear power plants, meaning that electricity generation from nuclear power plants is zero. Nevertheless, about 12 TWh of RE electricity would need to be curtailed.

With a 12-year extension of the operating life of nuclear power plants, this figure increases to about 21 TWh and with a 20-year extension to 28 TWh. This assumes a conditionally flexible operation of the nuclear power plants. This highlights the conflict potential between high RE penetration and the continued operation of nuclear power plants.

That the adherence to the minimum load is the critical limiting factor becomes clear when this assumption is relaxed and a Flex20 operation is assumed (i.e., the minimum load is only 20% for PWR and 40% for BWR). In the scenario with a 12-year extension, the amount of electricity that needs to be curtailed drops from 21 TWh in the conditionally flexible operation to 14 TWh (Flex20). Moreover, if short-term outages are also allowed (Flex0), this value drops to below 10 TWh. Remarkably, this is less than the amount of RE electricity that would need to be curtailed without nuclear power plants (12 TWh). This means that in the Flex0 scenario, electricity from RE could even be better integrated into the system than without nuclear power plants, as in this case the nuclear power plants can be operated more flexibly than the fossil power plant fleet.

To illustrate what the operation of a nuclear power plant would look like under these conditions, the number of cycles that would need to be driven in the various load ranges was calculated. In the scenario of a 12-year extension, about 350 cycles of 100-60-100 would be necessary in 2030 in the conditionally flexible operation. In the Flex20 operation, there would be about 200 cycles of 100-20-100 and an additional 200 cycles of 100-60-100. In the Flex0 operation, each nuclear power plant would on average run the cycle from full load to no load and back (100-0-100) about 100 times per year. Overall, each nuclear power plant would thus average about 2 to 3 start-up processes per week.