Original URL: http://www.theregister.co.uk/2011/03/21/fukushima_after_weekend_2/

Fukushima: Situation improving all the time

Food, water samples OK, Hyper Rescue Super Pump in action

By Lewis Page

Posted in Science, 21st March 2011 12:03 GMT

Events at the quake- and tsunami-stricken Fukushima Daiichi nuclear powerplant in Japan went well at the weekend, with two reactors there successfully brought into cold shutdown under off-site power, power lines hooked up to other cores being cooled using seawater and some progress in refilling spent-fuel storage pools. Initial food sampling from the region around indicates that no significant quantities of hazardous radioisotopes have escaped from the plant.

World Nuclear News reports that reactors 5 and 6, which were hooked up to a new power line from off site on Friday, were then able to restart their cooling systems and bring their cores to "cold shutdown", where the core coolant is at less than 100°C. Spent-fuel cooling ponds at these units are also being chilled effectively and brought to normal status.

Elsewhere at the plant, operators reported that offsite power was now also available at reactors 1 and 2, bringing various instruments and readings back online. As of Sunday, plant owner TEPCO hoped that main cooling would also be brought back at these units as it survived the quake in functional condition and was only lost when backup diesel generators were destroyed in the following tsunami. TEPCO expects to restore power at units 3 and 4 within days.

The focus of workers at the site has remained the spent-fuel pool at No 3, where waters levels were feared to have fallen dangerously low last week - raising the prospect of damage to the rods from their own internal heat. The elite Tokyo fire-brigade "Hyper Rescue" unit arrived at the site and commenced operations over the weekend, deploying a truck with a 22-metre arm able to spray 3 tonnes of water per minute - "in combination with Super Pump Truck", reports WNN.

Hyper Rescue reportedly sprayed the No 3 fuel pond with this equipment for more than 13 hours continuously yesterday (it can be operated remotely) delivering more than two thousand tonnes of water before shifting to No 4. The spent-fuel pool there had caused the Japanese authorities less concern than the one at No 3 as helicopter overflights last week had appeared to show it still held some water, though US officials chose to differ and described it as the priority problem at the plant. WNN reports that the general temperature observed at the two buildings' rooftops using thermal imagers is now below 100°C, and that radiation nearby continues to drop steadily. Latest readings there indicate levels of 2.75 millisievert/hr, indicating that workers need to carefully manage their time spent close to the two units: they can sustain a total annual dose of 250 millisievert under emergency rules before being withdrawn from the operation.

There was briefly some concern on Sunday at rising pressure levels inside the core of Reactor 3, and it appeared that heavy venting of radioactive steam would be required - potentially from the reactor containment rather than the suppression chamber, raising the prospect of heightened radiation levels similar to those seen last Tuesday when it is thought that the suppression chamber of Reactor 2 was damaged. However in the event no such venting was required and operations on site were able to continue.

Meanwhile sampling of food from farms in Fukushima province revealed that so far, in line with expectations, no dangerous radioisotopes have been released from the plant in significant quantities. The primary health threat is iodine-131, which can be dangerous to children and younger adults even in very small amounts as it concentrates in their thyroid glands. This can cause a slightly elevated risk of thyroid cancer later in life, enough that over a large population the effects will be apparent - though no individual need worry greatly as there will still be only one chance in several thousand of ever developing thyroid problems even for those very severely affected.

Another positive factor is that radio-iodine has a half-life of just eight days and thus it disappears within months. According to the Japanese government, the levels detected in food samples thus far would have to be consumed for a lifetime to do harm: if someone drank milk containing radio-iodine at the levels seen in the affected samples for a year, the effect on the thyroid would be the same as a single CT scan. (That would be impossible in this case as all the radio-iodine from Fukushima will have decayed away within weeks.) Nonetheless the Japanese government has advised that evacuees below the age of 40 from the 20km zone around the plant should take iodine pills (or syrup for children) as a precaution: the presence of non-radioactive iodine in the body prevents iodine-131 being taken up by the thyroid.

UK gov's top boffin says idea that Japan is concealing danger is 'completely paranoid'

The longer-lived isotope caesium-137 has also been detected in foodstuffs from the region, although again in very small amounts. It's not yet clear what the effects from this could be: after Chernobyl, where huge amounts of caesium were released, affected farmland had to be abandoned for varying periods but this seems highly unlikely in this case.

Tapwater in northeastern Japan remains entirely safe: though today's instruments can detect extremely tiny amounts of radioisotopes, in most cases none at all could be found. A few detections of iodine-131 were made, but well within normal safe limits - such water could be drunk for a lifetime without ill effects.

Chief cabinet secretary Yukiyo Edano said that the Japanese government would continue to monitor food and water across the country and that if any bans or limits on consumption were required they would be put in place: based on current indications no action was required.

Nowhere outside the powerplant boundaries has a radiation level of any concern to health been measured. On Friday the UK government's chief scientific advisor John Beddington described the Japanese evacuation measures as "sensible and proportionate" and said that even in a nightmare worst case with an explosion hurling material from a fully-melted core high into the air the situation in Tokyo would still be "absolutely no issue.  The problems are [in that situation] within 30 kilometres of the reactor."

He added:

Even if you had a completely paranoid view that somehow the radiation was being concealed, you can’t do it, it’s monitored throughout the world.  We know we can actually monitor exactly what the radiation levels are around there externally so it’s just not happening.

Unfortunately the situation is still not being clearly reported and some foreign embassies including the UK's have begun dispensing iodine pills to their nationals in Tokyo and/or advising them to leave, further inflaming the situation. Panic is reportedly spreading among the expat community there, not helped by the fact that the US is arranging evacuation flights for its citizens.

Analysis

The situation at the Fukushima Daiichi plant appears to be moving into its closing stages. Barring an unexpected change in circumstances there, the problems will soon be firmly under control without any worker at the site having sustained measurable health consequences from radiation - a testament to the steely professionalism with which they have managed the incident. The Fukushima Daiichi and Daini plants (the two hardest hit, with one worker who was in a crane cab as the quake hit being killed and two others missing since the tsunami struck) seem to have been very, very safe places to be compared to just about anywhere else in the stricken region.

Public health consequences also look to be nil based on reports thus far, apart from possible psychological problems from needless stress and panic.

The reactors involved are a 40-year-old design and much less safe than modern ones. They were hit by an earthquake five times as strong as they were built to take, followed by a tsunami wave now assessed as having being more than 12 metres high - twice the height their defences were specified to withstand. It now appears that despite all this they have not and will not harm a hair on anyone's head radiologically. Even everyday physical-trauma casualties have been very low compared to those seen elsewhere in the disaster zone.

Consider that if you simply work in an office or do something else generally considered very safe, there still exists a tiny chance of fatal disaster. Your office might be hit by a meteorite or a crashing plane or a runaway truck. A factory nearby might burn down or blow up, releasing dangerous pollution, and you might get ill or die. There might, as we see in Japan, be a terrible earthquake and tsunami.

You in your office might also cause harm or risk to others, for instance by filing misleading news stories and causing needless panic and stress, or by directing the operations of a normal not-very-safe industry or sector of activity which could present dangers to people in the event of a disaster striking - housing, transport, financial services etc.

If instead of working in your office you went out and spent your time operating a nuclear powerplant, we now see that the chance of any harm resulting to you or anyone else would be almost nil no matter what happened.

Operating nuclear power stations is not just very safe, or safer than other methods of generating power. It has to be one of the safest forms of activity undertaken by the human race. ®