there's probably a lot of molten fuel at ththe bottom of the reactor. becau we didn't know how much fuel, if any was further down in the reactor's containment vessel. the point of the vessel is to stop radioactive material from leaking out. if it turns out to be molten fuel, it would be the first they have found since the 2011 disaster. fuel mixed with debris penetrated the reactor and fell into the containment vessel underneath. so it very much depends on how much fuel has leaked out. it could speed up the clean-up process depending on the amount. at the moment, we still don't know. the government and tepco plan to send in a robot equipped with a radiation measuring device next month to make an assessment. here's the schedule the government wants to follow. they intend to draft a plan by this summer on how to limit debris from all three reactors. they want to finalize the details. by the first half of fiscal 2018. they want to begin actually removing the debris by 2021 . they say the whole process could take up to 40 years. >>> the fallout over u.s. pre

they released footage of what they think may be molten fuel. if confirmed, the finding would be the first of its kind. >> reporter: this video shows right under the reactor core deposits can be seen on the metal platform. tokyo electric power company officials say the deposits may be something they've been looking for, molten fuel. on monday workers sent an unmanned camera probe into the containment vessel of the number two reactor. that's one of the three reactors at fukushima daiichi plant where meltdowns occurred following the massive earthquake and tsunami in 2011. researchers believe that overheated fuel started to melt, went through a barrier and mixed with debris. workers have tried for years to locate the fuel. confirmation of the latest finding would greatly boost the decommissioning process. the officials plan to send in another set of devices early next month for further exploration. they hope to decide the method for the most difficult task, removing the fuel, later this year. ayumi chikaraishi, nhk world, tokyo. >>> japanese govern

. >> a molten salt reactor uses liquid fuel rather than solid fuel. >> reporter: having uranium dissolvedliquid offers some safety advantages. if the fuel gets too hot, the liquid expands, and the uranium atoms become too dispersed to maintain a nuclear chain reaction, it shuts itself down. and in the case of a station blackout, like fukushima, the liquid fuel drains into a larger tank where it cools down passively. no electricity needed. at oak ridge, they successfully ran and tested a molten salt reactor for four years and it worked. but building a reactor that can withstand something as corrosive as a very hot bath of salt is a huge engineering challenge. at oak ridge, the funding ended before they could work on that. so the corrosion problem is the focus of early testing for leslie's dewan's startup company, transatomic. >> we can make something that works for five years, that works for ten years, like, that we certainly know. what we are trying to figure out now is whether we can use newer materials or new methods of corrosion control to extend the lifetime of the facility, because u