The steam emanating from the top of Unit 3 Reactor Building indicates "no abnormality", according to plant owner Tokyo Electric Power Co. (TEPCO).
However "steam continues to be confirmed at the top of unit 3 reactor building intermittently since summer when debris removal was conducted on the top floor". The likely cause of the steam is "accumulated rainwater" and "no safety concerns indicated".
Steam has been visible since 18th July 2013, and has mostly been observed "on days with comparatively low temperature and high humidity and, upon almost all occasions, when rain had fallen before."
The steam has been observed around the edge of the shield plug of the Primary Containment Vessel (PCV), which is the upper structure of the reactor.
"No significant changes were found in either the main parameters related to the plant ... nor the monitoring post readings, which indicates no abnormality of the cooling of the reactor, nor dangers to human health, the company explained."
There has also been been "no significant change in the radiation dose and nuclide analysis results (dust sampling data) compared to those from before the steam was observed."
Radiation levels remain high on the the Reactor Building 3 and decontamination of the area will continue.
But despite the re-assuring message from TEPCO the situation remains critical. Another moderately severe earthquake could fracture the already badly damaged building's fuel storage pond and this would trigger an immediate need for emergency cooling of the spent fuel rods.
The current situation of Fukushima Daiichi may be seen via Live Camera at
Latest radiation dose monitoring results are posted at