* EDF publicly disagrees with regulator closure order
* Says dike strengthening to be carried out within a month
* Plant to shut down in coming days, EDF hopes for Nov restart
* Shut-down increases worry over winter supply, prices jump (Adds IRSN comment on flooding risk, Greenpeace comment)
By Bate Felix and Sudip Kar-Gupta
PARIS, Sept 28 (Reuters) - French utility EDF will temporarily shut down all four reactors at its Tricastin nuclear power plant after regulator ASN identified flaws in a canal dike bordering the plant.
ASN said in a statement that while the dikes are being strengthened, there there was a risk of flooding which could lead to a major accident at the plant, which is located along the Rhone river in the heart of France’s Provence wine and tourism region.
The planned shut-down forced EDF to revise down its overall nuclear output target for 2017, pushing its share price down 3.6 percent - its worst intraday loss in almost three months.
“Flooding could lead to a nuclear fuel meltdown accident in the reactors at the Tricastin nuclear power plant,” ASN said.
EDF’s four Tricastin reactors have a combined capacity of 3,600 megawatts, and their shutdown will add to worries that nuclear-reliant France could face tight power supply in winter after ASN identified other flaws at separate sites.
French front-month electricity futures jumped 2.54 percent to 42.45 euros per megawatt, remaining just below a year high set earlier this month.
In a highly unusual public disagreement with its regulator, EDF said it did not share ASN’s views but would nonetheless implement the decision “without undue delay”.
“We are convinced that the Tricastin reactors could remain in operation while the dike reinforcement works are being carried out,” Philippe Sasseigne, the head of EDF’s French reactor fleet, told reporters on a call.
He added that the four reactors would be switched off in the coming two to three days and that he hoped that they could reopen in early November, provided EDF gets ASN clearance to do so.
In the coming month, works will be carried out to strengthen the dike in order to guarantee its ability to withstand a major earthquake.
ASN’s technical arm IRSN said in a note that the Tricastin nuclear plant is located about six metres below the Donzere-Mondragon canal and that a major earthquake could cause its gravel dikes to liquefy.
This could flood the Tricastin reactors and cause a meltdown of the nuclear fuel in the reactors and the spent-fuel cooling pools, in a nuclear accident similar to the one in Fukushima, Japan in 2011.
IRSN said nuclear group Areva also has several major nuclear installations - including uranium conversion and enrichment facilities - at the site, metres below the canal level and equally vulnerable to flooding.
Greenpeace said in a statement it was irresponsible to build a nuclear plant below the water level of a canal.
EDF on Thursday lowered its 2017 nuclear generation target to 385-392 TWh, from a previous target of 390-400 TWh, but confirmed its 2017 and 2018 financial targets.
Writing and additional reporting by Geert De Clercq; Editing by Richard Lough and Adrian Croft