Tokyo Electric Power Co. says it is planning to change its information disclosure policy for the crippled Fukushima No. 1 nuclear plant and release all data on radiation-contaminated dust and water if it is deemed they are affecting the surrounding environment.

The decision, made during a board meeting last Friday, was in response to the failure to disclose a leak of radioactive rainwater that came to light last month.

Officials said Tepco will nail down the new policy by March 30 and present it to its nuclear reform monitoring panel of external experts.

Last month, Tepco said radiation-contaminated rainwater flowing through a drainage ditch that runs close to reactor buildings at Fukushima No. 1 had been leaking into the sea. The water's radiation level exceeded legal limits, it said.

Tepco said it became aware of the situation last spring but did not disclose it, thinking the information was not of interest to the public compared with updates on decommissioning efforts at the plant, including the condition of tanks being used to store highly tainted water.

Tepco eventually disclosed the information late last month after it identified what appeared to be the source of contamination for the leaked rainwater.

"The reform committee suggested that we disclose data swiftly even when we can't fully explain what the data means, so the new information disclosure policy will be more focused on swiftness of disclosure," Tepco spokesman Isao Shirai said Monday during a news conference.

Asked how much data remains undisclosed, Shirai said that to the best of his knowledge much of the data has already been released. But he added that some of the data subject to regular monitoring is not disclosed unless it involves high levels of radiation.