UPDATE 1-Nuclear shutdown costs mount in Germany -report
* German nuclear operators face 18 bln eur closure costs
* Final total might exceed utilities' 32.5 bln eur provisions
* Nuclear industry association says does not have cost estimate (Adds shares, analyst comment, amount of provisions)
FRANKFURT, Sept 28 (Reuters) - Germany's four operators of nuclear power stations, including E.ON (EONGn.DE) and RWE , face a bill of 18 billion euros ($24.5 billion) for decommissioning the country's reactors, possibly exceeding provisions, a newspaper reported.
Total costs might yet top the 32.5 billion euros that companies have set aside for expenses relating to the shutdown, German newspaper Handelsblatt said, citing environmentalists.
That is because the cost of storing nuclear waste produced during the lifetime of the 17 facilities are excluded from estimates, Handelsblatt said, citing a study from consultancy Arthur D. Little.
Germany this year decided to shut all nuclear power facilities in the next decade, reversing a plan that had extended the lifespan of the facilities well into the 2030s.
"The quantification of dismantling costs is in line with our estimate amounting to 1 billion euros per block," but "such estimates comprise several uncertainties", said Landesbank Baden-Wuerttemberg (LBBW) analyst Bernhard Jeggle.
"On the other hand, the provisioning for dismantling costs is based on several studies which have been checked several times in Germany."
E.ON shares dropped 1.1 percent and RWE slid 2 percent by 0827 GMT, while European utilities on the Stoxx 600 utilities Europe were down 0.9 percent.
A spokesman for the German atomic forum, the industry association of German nuclear producers, said it did not have an estimate for decommissioning costs.
"Companies are still calculating the costs," he said.
Arthur D. Little was not immediately available to comment.
Utilities and the German government admit it is not possible to exactly determine decommissioning costs. The energy companies say their provisions seek to take that into account.
Four utilities are operating nuclear power plants in Germany: E.ON had nuclear-related provisions of 16 billion euros at the end of 2010, RWE 10 billion euros, Vattenfall's German unit 1.3 billion and Energie Baden-Wuerttemberg 5.2 billion.
"We do not expect any increase in provisioning despite some uncertainties in the longer term," LBBW's Jeggle said.
($1 = 0.733 Euros) (Reporting By Peter Dinkloh; Editing by David Hulmes)