The situation at the Fukushima Daiichi nuclear powerplant in Japan, badly damaged during the extremely severe earthquake and tsunami there a week ago, continues to stabilise. It is becoming more probable by the day that public health consequences will be zero and radiation health effects among workers at the site will be so minor as to be hard to measure. Nuclear experts are beginning to condemn the international hysteria which has followed the incident in increasingly blunt terms.
Seawater cooling of the three damaged reactor cores (Nos 1, 2 and 3) at the site continues. US officials and other foreign commentators continued to remain focused on a spent-fuel storage pool at the No 4 reactor (whose fuel had been removed and placed in the pool some three months prior to the quake).
Despite this, operations by Japanese powerplant technicians, military personnel and emergency services at the site focused instead on cooling the spent-fuel pool at the No 3 building, and on restoring grid electrical power at the plant. Japanese officials continued to contend that water remained in the No 4 pool and the situation there was less serious than that at No 3. Police riot vehicles mounting powerful water cannon and fire trucks were used to douse the spent-fuel pool at No 3 with water, causing steam to emerge – confirming that some cooling at least was being achieved. One of the fire trucks was reportedly lent by US military units based locally, though operated by Japanese troops.
World Nuclear News reports that radiation levels have generally decreased across the plant, though they remain hazardous in the immediate area of reactors 2 and 3; levels also climb temporarily when technicians open valves to vent steam from the damaged cores in order to allow fresh seawater coolant to be pumped in, prompting teams to retreat before venting is carried out. Nonetheless 180 personnel are now working within the site where and when radiation levels permit them to do so safely.
An external power line has now been laid out to the plant and latest reports indicate that this will be connected to its systems by tomorrow: final hookup has been delayed by steam-venting operations from the cores. Powerplant technicians hope that this will restore cooling service to reactor cores and spent-fuel pools across the plant, in particular to the pools at reactors 3 and 4. If normal water levels can be restored to the pools high levels of radiation above and immediately around the buildings will be cut off by the liquid's shielding effect. The buildings' roofs would normally help with this, but both have been blown off in previous hydrogen explosions.
Meanwhile, plant operator TEPCO said that on-site diesel generation serving units 5 and 6 – which are safely shut down, but which also have spent fuel in their storage pools – has been restored. The plant's diesels were mostly crippled by the tsunami which followed the quake: the wave was higher than the facility's protective barriers had been designed for. The prospect of any trouble at these reactors now seems remote.
The IAEA seems to accept that things are settling down: a senior official at the agency tells Reuters that the situation is now "reasonably stable".
Radiation readings at the site boundary remained low through Friday morning in Japan, dropping to 0.26 millisievert/hour. Personnel at the site are normally permitted to sustain 20 millisievert in a year: this has been raised to 250 millisievert owing to the emergency.
Normal dosage from background radiation is 2-3 millisievert annually: a chest CT scan delivers 7 millisievert. The highest radiation level detected anywhere beyond the site was a single brief reading of 0.17 millisievert at the boundary of the evacuation zone, but on average (Japanese government PDF/72KB) readings at the zone boundary are hardly above background.
Occasional brief readings of slightly heightened radiation – occasionally reported in scaremongering fashion as "10x normal" – have been detected as far afield as the outskirts of Tokyo, but these are insignificant in a health context. Even if they persisted unbroken for a year, local dosages at such a level would be no more than powerplant workers are allowed in normal times: and nuclear powerplant workers' cancer rate is actually lower than in the general population. Measurable blips in background radiation may be detectable around the world in coming weeks, and will no doubt be heavily reported on, but they will be more insignificant still.