Aletho News

Fukushima Update – May 11

Moon of Alabama

The big mess at the Fukushima Daiichi plant continues as the damaged reactors there are still releasing radioactive substances into the environment. A new leak through a cable shaft and to the cooling water intake of the no 3 reactor to the sea was found only today.

At the no 1 plant the reactor vessel continues to be fed with cooling water but can not be filled up above the level of the exposed nuclear fuel likely because of leaking pipe connections at a certain height. Now the primary containment vessel around the reactor vessel will get filled with water. This creates a “water sarcophagus” to cool the reactor vessel from the outside. So far over 9,900 tons of water have been pumped into it. Eventually water will be filled high enough to submerge the reactor vessel and thereby refill it through the leaking pipe connection.

Yesterday workers could access the inner no 1 reactor building for the very first time and they tried to install some new monitoring systems as the old ones are broken. Before the access door was opened and the workers could enter air was pushed through the building and through filters to reduce the radiation in the building. This was not very successful. Tepco had hoped to reduce radiation there to 1 millisievert per hour, but some areas inside the building that eventually need to be entered still have radiation levels between 600 and 700 millisieverts per hour, much higher than the maximum 250 millisievert lifetime(!) radiation limit that nuclear workers can be exposed to in emergency cases. Those areas will need to get shielded off before work around them can continue.

The spent fuel pool in no 1 continues to get refilled with water which then continues to evaporate through the severely damaged roof. Hydrazine was added to the water as corrosion inhibitor.

The number no 2 reactor vessel and primary containment are still leaking water into the basement of the machine hall of no 2 and 3 and from there through various ways into the environment. Work has started to pump the water out for decontamination and to block all ways from the basement into the environment. Eventually the leak in the containment vessel (likely at the damaged torus outside the primary containment which holds condensation water) will have to be repaired to allow for restoring a permanent cooling loop or to attempt to create a “water sarcophagus” around it. This will be very difficult to achieve as the water coming from the leak is radioactive.

The no 2 spent fuel pool seems for now to be fine as an improvised cooling loop has been established for it.

The no 3 reactor shows increasing reactor vessel temperature. Over the last 10 days the temperature temperature at the feedwater nozzle increased from below 100 degrees centigrade to over 221 degrees now. As the reactor vessel and primary containment is also likely damaged this also increases evaporation and releases into the environment.

The spent fuel pool in no 3 continues to get intermittently refilled with water which then continues to evaporate through the severely damaged roof. A camera view (see May 10 entry) into the water filled pool showed only tons of heavy debris from the collapsed roof.

The heavily damaged no 4 building had no active reactor at the time of the quake but a full spent fuel pool. A few days ago a camera view (see entry at May 8) into the pool showed no visible damage to the fuel elements but some rubble on top of them. Some gas bubbles were coming up from the fuel elements which points to some damaged fuel rods and continued hydrate release.

According to this Russia News report there is some speculation (starting at 3:10) that the building of reactor no 4 began to lean to one side. NISA, the Japanese regulator had ordered Tepco to check the statics of that building some weeks ago. Maybe they had good reason to do so?

In the general surrounding of the plant rubble gets removed with remote operated machines and synthetic resin gets sprayed on all surfaces to prevent radioactive dust from coming up.

Some people where allowed to visit the evacuated areas to remove items from their homes. The government seems to finally adopt the evacuated area to a real assessment of the radiation. It had at first created a 20 kilometers and then a 30 kilometer circular evacuation zone. But the days after the explosions at the plant the wind blew over land towards north-northwest before turning back to the sea and that area has of course higher radiation levels now even beyond the 30 kilometer zone than areas more near to but south of the reactors. (I remember seeing a German radiation prediction chart just a few days after the reactor explosions that showed just that. What took the Japanese government so long to come to this conclusion?) Higher levels of radiation have been found in wastewater facilities beyond the current evacuation area. This will likely be from runoff water that went into the sewage. The sludge that the wastewater facilities create is used to produce cement which will now be slightly radiated.

The prime minister of Japan has ordered another nuclear site with six reactors, Hamaoka, to shut down as it stands above a tectonic fault which is suspected to create a big quake and probably soon. This will increase the electricity deficit this summer, which will lead to blackouts and further economic damage.

Additional resources:
Update from Dr. Saji former Secretariat of Japan’s Nuclear Safety Commission <— NEW!
AllThingsNuclear Union of Concerned Scientists
Bulletin of the Atomic Scientists
Atomic power review blog
Digital Globe Sat Pictures
IAEA Newscenter
NISA Japanese Nuclear Regulator
Japan Atomic Industry Forum (regular updates)
Japanese government press releases in English
Kyodo News Agency
Asahi Shimbun leading Japanese newspaper in English
NHK World TV via Ustream
Status reports for the German Federal Government by the Gesellschaft für Reaktorsicherheit in German language

May 11, 2011 - Posted by aletho | Nuclear Power