Tokyo: Some oil-tanker owners are seeking additional fees for carrying cargoes to Japan, the world's third-largest crude consumer, according to Stena Bulk AB, which operates a fleet of more than 80 vessels.

The world's biggest tanker firms, dry-bulk carriers and container lines said last week they are still servicing Japanese ports, judging there to be no threat to vessels or crew from radiation leaking from a crippled nuclear plant.

All vessels are avoiding a 30-kilometre exclusion zone around the Fukushima Dai-Ichi plant, about 220 kilometres north of Tokyo.

"I do think it commands a small premium," Erik Lewenhaupt, general manager of Stena Bulk Singapore, said by phone while declining to quantify the scale of the additional charge. "I wouldn't call it significant at the moment," he said.

Record-high readings of contaminated sea water were found on Friday near the plant, which was damaged by a magnitude-9 earthquake and 23-foot tsunami on March 11, Japan's Nuclear and Industrial Safety Agency said.

The International Maritime Organisation (IMO) said on March 21 there was no medical basis for restricting shipping, and the US Navy said on Thursday any radiation on vessels can be scrubbed off with soap and water and isn't harmful to people's health.

"At the moment, nothing has been done on it because it's Japanese cargoes going on Japanese ships, but there's an underlying feeling that perhaps owners could ask for 2.5 points more," said Bob Knight, head of tankers at Clarkson Plc, the world's biggest shipbroker.

Underlying feeling

He was referring to the industry's Worldscale system for determining charter rates.

While there have been no recent bookings to Japan, "if an owner knew he would go to Japan, he would definitely ask for a premium," said Nikos Varvaropoulos, a Dubai-based official at Optima Shipbrokers Ltd.

Owners are inserting clauses into their contracts to compensate them in the event ships or crews are affected by radiation, Varvaropoulos said.

Torm A/S, Europe's biggest shipper of oil products including gasoline and jet fuel, is not charging extra to go to Japan, Tina Revsbech, head of tankers at the Hellerup, Denmark- based company, said by phone. "We don't charge a premium," Revsbech said. "I don't see any reason to do it."

Ships sailing into nuclear zones aren't insured if radiation affects the vessels or their crews, according to information on the website of the UK.

P&I Club, which insures a fleet drawn from more than 50 nations. Shipping lines should "think very carefully" before refusing to sail to Japanese ports south of Kashima, Nick Burgess, head of the Japan team at law firm Ince & Co, said in a report March 30.

"If there was a real risk of exposure to unacceptable levels of radiation, then charterers might be in breach of the safe-port warranty in ordering the vessel to proceed," Burgess said in the report.

"Current information sources coming from Japan and elsewhere all suggest that the exclusion area does not extend to Tokyo or Yokohama and that levels of radiation there are low and within acceptable levels."