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Japanese Reactor Safety following tsunami (Fukushima Daiichi)

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By Ron Rubendra - Posted on 13 March 2011

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As many of you are aware Japan has recently suffered a major tsunami caused by one of the largest earthquakes in recorded history. There has been (a still be determined) enormous loss of life just from this and the situation is still developing.  

What we do know is that there has been major failures in the local infrastructure and judging by the tsunami footage that has been aired, this is not surprising .
As a consequence of this, one of the number of Japanese light water reactors at Fukushima (Unit 1 reactor at the Fukushima Daiichi nuclear power plant), close to the event, has suffered a catastrophic failure of its safety systems. The power reactors are boiling water reactors (BWRs) ranging between (439MW to 1067MW) (this compares to ANSTO’s OPAL research reactor in Sydney of 20MW). These are, I believe, LEU (low enriched uranium) reactors.
News reports indicate that a LOCA (loss of coolant accident) has occurred where the fuel rods are not able to be cooled. The primary coolant systems have failed, as have the backup systems (diesel and electric) from the effects of the tsunami. This has led to possible breach of fuel rod's cladding and the partial release of the source term (indicated by the iodine and caesium fission products) from the reactor containment (this has not been confirmed). The Japanese nuclear authorities have begun implementing their safety management plans and have attempted to flood the reactor with sea water (with boron as a moderator) to try to keep it cool and reduce the nuclear interactions.
The closest residents have been evacuated and they have also started iodine prophylaxis with surrounding residents and implementation procedures to reduce inhalation and ingestion hazards.
The IAEA report that this is a INES Level 4 event ('Accident with Local Consequences') here  
The dose rate was reported to peak at a maximum of 1.2 mSv/hr at the outside of the reactor plant. Other reports indicate 0.065mSv/hr in reactor control room. Other reports of ~100 mSv are here which if correct are significant but not fatal (LD50 is ~5000mSv).  
The NYT has articles here and here  
Background (from here)
·         Japan needs to import some 80% of its energy requirements.
·         Its first commercial nuclear power reactor began operating in mid 1966, and nuclear energy has been a national strategic priority since 1973.
·         The country's 54 reactors provide some 30% of the country's electricity and this is expected to increase to at least 40% by 2017.
·         Japan has a full fuel cycle set-up, including enrichment and reprocessing of used fuel for recycle.
Please discuss and add information.
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There's been a lot more news reporting on more events at the reactor. Some of it, I feel, is a bit sensational. The IAEA have some more rational reporting here .

(Let's not forget that while focus on the safety of the reactors is important - the whole east coast is still suffering from the effects of the earthquake/ tsunami and the associated recovery is underway).

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Reported in today's papers that radiation levels are back to normal here

Ron Rubendra MARPS

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