Fukushima, Japan nuclear news update

Conditions appear to have stabilized on site. Grid power is now available in all the units. However, electrical equipment still must be checked before it can be switched on. Obviously, getting cooling systems back into operation is a priority. The lights are on in the control room for reactor three, and bringing this back into service will enable better monitoring of the situation. Operations to add water to the spent fuel pools of Reactor 3 and 4 continues. A concrete pumper with an extending boom has been brought in to provide water at unit 4. However, aerial surveillance suggests that water doesn't stay in the pools, and that they are leaking.

Some radiation has been detected leaking into the ocean.

The bottom line is that the situation is stable but still not safe.

When the Reactor buildings at unit 2 and unit 4 suffered explosions on March 15th, the blasts occurred within 6 minutes of each other. I think that this is odd. Perhaps it indicates that the explosions were somehow linked.

pdf status report from JAIF

Why the Fukushima crisis has people worried

The images below have been adjusted to the same scale.  One is an image of  Northern Japan, and the other shows the size of the area affected by radiation from Chernobyl. The arrow indicates the location of the nuclear plant.

This only relates to long term health impacts. At Chernobyl, only workers at the site were affected by radiation sickness. The images show how bad a Chernobyl style release could be for the Japanese.

 
(Images from wikimaps and wikipedia)

The precise patterns of fallout would depend on wind directions and rain fall. Tokyo is the world's largest metropolitan area, with 35 million people.

Fortunately, the latest news from Japan is good. Major progress has been made in adding water to spent fuel ponds and restoring cooling. However, there is much still to be done.

More gadgets for Fukushima

Might disaster be avoided?

AERIAL WATER TOWER / HYDRAULIC PLATFORM

I can't find data on the height of the spent fuel pond, but it appears to be less than 50 meters above the ground.  Google Earth indicates that the original reactor buildings were 80 meters high. There are a few fire-fighting vehicles which can reach that high. Once positioned and aimed, the crew could abandon the vehicle, leaving it to deliver water to the spent fuel pond. If it could be connected to the  Hytrans water supply system which I mentioned in my last post, then a continuous stream of water could be delivered to the spent fuel pond indefinitely. Set up time for these systems is of the order of minutes rather than hours.

The HLA from Finnish firm Bronto Skylift can deliver 3800 litres per minute (228 tonnes per hour) of water to over 100 meters above ground level. It also has substantial horizontal reach, allowing it to poke into the reactor building to reach the fuel pond. The pictures show it in operation.

I think this might just work, but the setup time will expose the crew to a substantial radiation dose.
http://www.bronto.fi/sivu.aspx?taso=1&id=125

FOX NBC RECONNAISSANCE VEHICLE

The M93 Fox is a vehicle used by the military to map areas affected by radioactive fallout and chemical contamination. If the worst happens in Japan, these vehicles and their crews will be in demand to map contaminated areas. The US military has a number of these vehicles.
http://en.wikipedia.org/wiki/M93_Fox
http://www.globalsecurity.org/military/systems/ground/m93a1.htm

BRADLEY FIGHTING VEHICLE

This is normally used to carry soldiers on the battlefield. They are equipped with ventilation systems which can filter out radioactive particles and protect the troops inside. Thick steel armor also shields the occupants from radiation. Bradleys could be used to transport people through contaminated areas.
http://en.wikipedia.org/wiki/Bradley_fighting_vehicle


GLOBAL HAWK UAV

This large, high flying unmanned airplane can keep the reactors under surveillance and warn of any changes. It has infra-red cameras which would be ideal for detecting fires and hot spots.
http://en.wikipedia.org/wiki/Northrop_Grumman_RQ-4_Global_Hawk


UPDATE: Saturday:  The Japanese appear to be thinking along similar lines.  the Yomiuri Shimbun newspaper reports that they are sending some fire trucks and a hose laying system from Tokyo. Quote:

One large ladder truck is capable of spraying water from about 40 meters above the ground, while an elevating squirt truck can blast 3.8 tons of water per minute from a height of 22 meters by remote control, the fire department said. These high positions will allow water to be sprayed onto the storage pool, which is in the upper part of the reactor building. Other vehicles include a hose layer to extend hose lines. A hose layer carries 72 hoses, which can be connected to "Super Pumper" trucks to build a long-distance pumping system. The system is designed so water can be pumped from the sea or a river as much as two kilometers away to maintain a constant supply to the engines, according to the fire department.

The Fire Engine Photos website has a picture of one of the "Super Pumper" hose laying systems here. It belongs to the elite "Hyper Rescue" squad.

Send in the robots!

I have noticed some people commenting elsewhere about sending in various types of robot to save the plant. So I looked around the web and found quite a few things that would be potentially useful.


UNMANNED K-MAX HELICOPTER

This is capable of lifting about 2 tons, and it would be ideal for water drops onto the reactor. In fact it would have a lot of potential uses in this situation, and hopefully Japan is being made aware of its capability. This was developed for airborne resupply of isolated soldiers. It dropped 16 payloads in recent tests. It does have a cockpit so it can be flown manned if necessary.
http://www.gizmag.com/k-max-unmanned-helicopter-milestones/17969/


RADIO CONTROLLED HELICOPTERS WITH CAMERAS

There are a huge variety of small radio controlled helicopters which could be flown into the reactor buildings to get a closer look at the damage. A big limitation is that they have to be within line of sight of the radio controller, and maximum range is about 300 meters. Endurance is about 20 minutes before the battery runs out.

Tiny wireless cameras are available for these things, with a mass of only 9 grams.

Probably the coolest of all these is the Dragenflyer X6 flying camera. It looks like something out of James Bond. Be sure to check out the Youtube video below.





http://inventorspot.com/articles/draganflyer_x6_camera_007_would_love_27309


US NAVY FIRESCOUT

This is a really nice robotic flying camera. Endurance is 8 hours.

http://en.wikipedia.org/wiki/Northrop_Grumman_MQ-8_Fire_Scout


ROBOT BULLDOZER

For clearing debris around the reactors, what about this 60 tonne robot bulldozer from Israel? The Israelis use it to clear roads of mines.

http://www.theregister.co.uk/2009/03/31/idf_robot_d9_revelations/


HYTRANS FIREWATER SUPPLY SYSTEM

This system can deliver 3000 litres per minute of water over several kilometers, using flexible hoses like the one in the picture. The Berkeley,CA fire department recently bought one for fighting fires after an earthquake. It can be rapidly deployed from trucks. Something like this could potentially provide a way to get water to the reactors and spent fuel ponds.
http://www.hytransfiresystem.com/


ROBOT FIRE ENGINE

The Japanese have developed a small robot fire engine called the Rainbow 5. If this could be lowered onto the roof of Reactor 3, maybe it could insert a hose into the spent fuel pond.
http://www.youtube.com/watch?v=KOSh8dNGzYo





BUT WILL THE ELECTRONICS SURVIVE?


One potential snag is that most of these gadgets depend on silicon microchips. These microchips are somewhat vulnerable to strong radiation, which can cause computer errors.

Fukushima: Japanese for Chernobyl

What's the big picture here? Deep within the radioactive ruins of the Fukushima
Daiichi nuclear complex, there lie four swimming pool like structures. These are
the spent fuel ponds. These are full of used fuel rods from the nuclear reactors.
Spent fuel must be kept covered with water to absorb the radiation from it and
keep it cool.

Heat from the spent fuel is slowly evaporating the water in the ponds. Under
normal circumstances topping up the water level would not be a problem, but the
situation at Fukushima is not normal. Over the past few days, the reactor
buildings have been ripped apart by hydrogen explosions. The ponds are located on
the upper levels in the buildings, and normal access routes to them are probably
destroyed or blocked by debris. The blasts may have cracked the concrete
structure of the ponds themselves, causing water leaks. Piping and
instrumentation cables leading to the ponds have probably been destroyed.

What makes this much worse is that the hydrogen explosions have also punctured at
least two of the reactor containments. The whole Fukushima site is now covered in
dangerous radiation, and levels near the reactors are reported to be lethal.
The bottom line here us that there little chance that the plant workers will be
able to maintain the water levels in the fuel rods. That fuel is going to be
exposed to the air.

What happens then? The fuel will heat up, and the metal cladding will react with
the water to liberate hydrogen. This will lead to further hydrogen explosions. At
some point the water will all boil away. Fuel temperatures will then rise much
further.

Expert opinion differs on what happens next. Some experts say that the fuel will
not catch fire. Others say that the fuel will burn, and I strongly agree with
that. Put a large pile of flammable stuff in a metal lined basin which tends to
retain heat, then raise the temperature, and something is going to ignite.
Experts I have read seem to agree that a spent fuel pond fire is one of the worst
things that can happen in a nuclear plant. It is as bad as a core meltdown, if
not worse. It will release huge amounts of radiation into the air, which will
then go where ever the winds take it.

Major spent fuel pond fires are now all but inevitable. This will be every bit as
bad as Chernobyl. That is why the French are telling their citizens to leave the
country, and why the US is advising Americans to stay 50 miles away.

ARE THE PONDS ALREADY BURNING?

Some US experts believe that the water in the spent fuel pond at Reactor 4 has
already gone. The reactor building has been blown apart by a hydrogen explosion,
and they think that the exposed fuel rods are the source of the hydrogen. There
have been signs of a fire inside the building.

I think the US experts are wrong. The spent fuel pond is at the top of the
structure. Hydrogen tends to rise, and it would not sink down into the lower
levels of the building. Hydrogen from the fuel ponds would blow the roof off, but
would not produce the kind of damage visible in building 4. The hydrogen that
blew up building 4 came from somewhere else. However it is possible that the
explosion damaged the pond and that all the water leaked out.

The Japanese say that the water is still there and that the temperature is 86
Celsius, far above normal. I suspect that the Japanese are correct, but it
doesn't really make much difference. There is no feasible way to top the water
up.

Radioactive steam leaking at Fukushima

Various reports on the web indicate high radiation levels near Reactor 3. The media is reporting that radioactive steam is venting from that reactor and that containment has been lost.

This satellite picture shows Reactor 3 just after it exploded. There is steam venting clearly visible. This venting is almost certainly not a design feature. It is coming from an area which has been totally destroyed by the blast. I suspect it shows a breach in containment which was caused by the explosion. Various reports on the web indicate high radiation levels near Reactor 3.

There have been many reports of intentional venting of the containment. When the plant does that, the gas is passed through filters in order to remove as much radiation as possible. Then it is emitted from a tall smokestack.

AN EVEN BIGGER PROBLEM?

Somewhere in the radioactive ruins of Reactor 3 there is a swimming pool like tank called a spent fuel pond. It has been reported that there is some fuel in the pond. Such ponds often contain many reactors worth of radiation.

Heat from the spent fuel evaporates the water, and under normal circumstances several percent a day of the volume would be lost. If the explosion has damaged the tank and it is leaking then levels could fall more quickly. If all the water were to be lost, then the fuel rods would overheat and probably catch fire. That would lead to a Chernobyl style release of radiation.

It is essential that the water in this pool is kept topped up, but how will this be done? The pool is high up in the reactor structure, in an area subject to intense radiation. Normal access routes to the pool may be impassable.  Pipes feeding the pool may have been destroyed in the explosion.

Here is the question. Do the Japanese know what the water level is, or were the instrument cables destroyed in the explosion? Do they have the ability to top up the water level?

If not, then Japan has a very big problem.

A LITTLE GOOD NEWS

Latest reports are that the fire in Reactor 4 had nothing to do with spent fuel. It is now said that an oil leak was to blame.

UPDATE: There are conflicting reports on the fire.
UPDATE: Latest photographs make it clear that Reactor 4 has suffered a massive explosion. The damage is almost as bad as Reactor 3. I wonder if hydrogen from #3 somehow got into #4, perhaps via the ventilation system?

Nuclear disaster goes from bad to worse

The Fukushima disaster is now spinning out of control.

REACTOR 2 BREACHES CONTAINMENT

The explosion yesterday from Reactor 3 destroyed most of the pumps that were cooling Reactor 2. Reactor 2 started down the now familiar path of falling water levels, exposed fuel rods, fuel melting, and hydrogen generation.

However, this time the result has been a breach of the containment. At the base of the reactor there is a big circular steel tube called the "Wet well". This has the shape of a donut or torus, and it is normally partly filled with water. It is connected to the "Dry Well", which contains the reactor, by big steel tubes.

The Japanese now believe that this is leaking, maybe as a result of too much internal pressure, or maybe as the result of a hydrogen explosion.

The Wet well and the Dry Well together make up the containment. Both must stay intact to contain radiation if a meltdown occurs.

SPENT FUEL PONDS

When I was annotating this diagram for the last post, I was wondering about something that looked like a spent fuel storage pond sitting at the top of the reactor. I was hoping that it was just temporary storage, which would be empty.

Today other people have started commenting on it, so I have marked it in tonight's post. It now seems as if there may be a lot of spent fuel stored in that pond.

It is in an extremely vulnerable position, right at the top of the reactor. Fortunately, the hydrogen explosions have so far blown away surrounding structure while leaving the spent fuel storage ponds intact. If the fuel was to be ejected from the pond it would subject the whole site to intense radiation which would be immediately detectable. If exposed to air, the fuel would probably also catch fire. This would release large amounts of radiation.

The fuel generates heat, and it will tend to boil water out of the pool. The pool needs to kept topped up.

WHAT IS SPENT FUEL?

When fuel is removed from a reactor it is extremely radioactive and still producing significant amounts of heat. A large crane lifts the fuel out of the reactor vessel and lowers it into a deep tank of water. This is the spent fuel pool. The water blocks the radiation, and keeps the fuel cool.
In time, the radiation and heat production drops. Eventually, the fuel is put into a large metal container, lifted out of the pool by a crane, and lowered onto a railway car for transport.

REPORTS OF FIRE IN REACTOR FOUR

This is odd, because Reactor Four was supposed to be shut down for maintenance. It is possible that some supplies left behind by the maintenance workers caught fire. Things like electrical cables can burn, and there was a serious fire at Brown's Ferry many years ago which was started by a maintenance worker.

A far more disturbing possibility is that the spent fuel is burning. That might happen if all the water in the spent fuel pool boiled away. If fuel is burning, large amount of radiation will be detected.