* Grid operator outlines four scenarios for 2035 energy mix
* Government withholds least pro-nuclear notes from debate
* Public debate to lead to decision on nuclear by early 2019
* Ahead of 2015 law, ministry withheld pro-renewables report
PARIS, Jan 25 (Reuters) - The French government is hampering discussion about how to reduce the country's reliance on nuclear energy by limiting debate about more radical alternatives, renewable energy advocates said on Thursday.
France's previous socialist government pledged to reduce the share of nuclear in power generation to 50 percent by 2025, from 75 percent today.
President Emmanuel Macron promised to respect that pledge during his election campaign last year, but since taking office he has pushed the target back by a decade.
Macron now wants to set new targets in a multi-year energy plan that will be debated this year and presented in early 2019.
But renewable energy activists say that at some workshops earlier this month, the government blocked discussion of scenarios under which France would radically reduce its nuclear power capacity, instead focusing on more pro-nuclear scenarios.
Energy and Environment Minister Nicolas Hulot has denied that the government favoured the most pro-nuclear scenarios, saying it merely eliminated the two most extreme scenarios and kept the "median" scenarios.
He did not specify which scenarios had been eliminated.
Late last year, French grid operator RTE published four 2035 scenarios under which nuclear capacity would be reduced to various degrees from the current 63 gigawatt (GW).
Under the "Volt" scenario, nuclear capacity would be cut to 55 GW by closing just nine of state-owned utility EDF's 58 nuclear reactors and leaving the share of nuclear in power production at 56 percent. The "Ampere" scenario would close 16 reactors and leave the share of nuclear at 46 percent.
Two more radical scenarios, "Watt" and "Hertz", would close as many as 52 and 25 reactors respectively, with the Watt scenario cutting the share of nuclear to as little as 11 percent. The remaining power would come from renewables (71 percent) and gas (18 percent).
"The Watt and Hertz scenarios were eliminated from the presentations at the government's request," said Yves Marignac of NegaWatt, a group which advocates higher renewables use.
NegaWatt took part in two workshops to prepare the public debate on the issue. It was joined by several energy-focused NGOs, EDF, nuclear firm Orano, and lobby groups. The debates are supposed to lead to a first draft of a multi-year energy plan by summer and a final plan in early 2019.
Its conclusions will be crucial for European power markets as they will determine how much nuclear baseload capacity remains available.
A source involved with organising the workshops confirmed the government had instructed RTE to withdraw two scenarios.
"All scenarios were mentioned, but only two were reviewed in detail," he said.
A ministry spokeswoman said two scenarios had indeed been removed from the presentation but declined to give details.
"It is inconceivable that these two scenarios would be withheld from public debate," NegaWatt's Thierry Salomon said.
France has withheld key information on nuclear before.
In the months before the parliament vote on the 2015 energy law, Hulot's predecessor Segolene Royal barred publication of an environment agency ADEME report showing France could switch to 100 percent renewables without extra costs.
"At least this time the information is public. But it looks like the government is putting the interests of the nuclear industry ahead of the energy policy debate," Salomon said.
> Link to ADEME report story: https://tinyurl.com/y84ow838 (Reporting by Geert De Clercq. Editing by Jane Merriman)