UPDATE 2-French uranium leak smaller than thought-Areva

(Adds Environment Minister's reaction paragraph 2, 3)

PARIS, July 9 (Reuters) - French nuclear firm Areva said on Wednesday a leak of liquid containing uranium from a site in southeastern France was smaller than initially thought.

Environment Minister Jean-Louis Borloo said the nuclear safety authority (ASN) would inspect the area on Thursday to determine the precise causes of the incident.

"All the conclusions will be drawn, notably in terms of any eventual legal or administrative follow up," Borloo said in a statement.

Areva CEPFi.PA said late on Tuesday that 30 cubic metres of liquid containing uranium, which was not enriched, was accidentally poured on the ground and into a river at the Tricastin nuclear site.

"Thirty cubic metres was poured but part of it was caught by a security system, which means that only 18 cubic metres actually fell on the ground and in the water," a spokesman for Socatri, an Areva subsidiary, said.

The prefecture or local government council of Vaucluse said a total of 74 kilograms of natural uranium fell into the water while 150 kilograms remained on ground on the Socatri premises.

Socatri specializes in the maintenance and dismantling of nuclear material as well as managing nuclear waste.

The Prefecture of Vaucluse added that the leaked uranium should only be found in microgrammes in river water. "The risk for the population is therefore low," it said in a statement.

The nuclear safety authority said the uranium concentration stood at 12 grammes per litre.

The prefecture added that in surface waters, the levels of uranium have remained far more than the norm, but had significantly diminished since the leak occurred.

Tests carried out at local lakes showed no uranium contamination, meaning that 100 evacuated bathers had not been affected, the prefecture added.

By way of precaution, the prefecture has banned all fishing, sailing and swimming in the affected area, as well as the use of affected waters for consumption or irrigation.

Environmental group Greenpeace France attacked Socatri for not alerting the relevant authorities fast enough.

"Contrary to what has been said, the leak took place on July 7 at 2300 (2100 GMT)," Greenpeace said in a statement.

"Socatri alerted the Nuclear Safety Authority on July 8 at 0730 (0530 GMT)," Greenpeace and the ASN said, adding that the company only realized the importance of the leak at noon, allowing the prefecture to take precautionary measures by 1300 (1100 GMT).

"Those delays are unacceptable," said Yannick Rousselet, head of energy campaigns at Greenpeace. (Reporting by Joseph Tandy and Muriel Boselli; editing by James Jukwey)