Japan must avoid being "over-conservative" in decontaminating areas affected by radiation from the Fukushima disaster.
Japan is faced with cleaning up tsunami-hit Fukushima Daiichi nuclear power plant, located 240 kilometres northeast of Tokyo, and the surrounding regions.
Radiation has spread from the plant, fuelling public fear and forcing some 80,000 people to leave their homes after the government banned entry within a 20 km radius of Daiichi.
Removing layers of topsoil from areas contaminated by radiation is one of the methods being considered by Japan, but the team of 12 experts sent by the International Atomic Agency (IAEA) said it would be impractical.
"We are not saying the government's approach is over-conservative, what we want is for the government to avoid becoming over-conservative in the future," said Tero Tapio Varjoranta, the team's deputy leader.
Efforts to bring the plant under control have progressed steadily, but Japan still faces the challenge of decontaminating vast land affected by the disaster, which the environmental ministry says could be about 2,400 square km, an area roughly the size of Luxembourg.
Japan's environmental ministry has said the method of scraping off surface soil could result in about 29 million cubic metres of radioactive waste that needs to be disposed, and finding a final storage place for the debris is seen as a major headache for the government.
"Where applicable, there are methods that do not require storage. There are about 60 remediation technologies available. We are taking the advice from our experiences in Chernobyl, where a lot of mistakes were made," Varjoranta said.
Some of the methods included mixing up the removed topsoil with clean material for the construction of roads and reinforcement of banks, or storing them in various layers, the IAEA says.
The IAEA team, which will end its nine-day mission on Saturday, will present a final report to the Japanese government next month.
"The word 'conservative' appeared several times in the report. We have been working based on the concept of the public's safety and I don't think that is wrong," said Goshi Hosono, Japan's environmental minister, after being presented with a draft report by the IAEA officials.
But he added: "We need to take their advice into consideration when we create our road map for the storage of radioactive waste."