A Supplementary explanation added on the report on the steel beam falling into Unit 3 Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station in response to the additional directive document received from the Nuclear Regulation Authority A Supplementary explanation added on the report on the steel beam falling into Unit 3 Spent Fuel Pool at Fukushima Daiichi Nuclear Power Station in response to the additional directive document received from the Nuclear Regulation Authority