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Japan Nuclear Watch: A Time Line -March 11th -March 16th

8:42 am in Uncategorized by Bill Egnor

Reactor Containment & Fuel Storage from UCS; (h/t commenter lobster)

It’s Wednesday evening in Japan, mid-morning in US east coast.

We’ve had a lot of information on the Japanese nuclear disaster. Given that there were three operating reactors at the time of the earthquake and there have been problems with four (three of them with the reactors themselves and on at Unit 4 regarding the rods in the storage pool) I thought it would be worth while to start a time line of events to help everyone keep it all straight in their minds.

Since this has been rather chaotic and there is concern that there has been some holding back of information from TEPCO (Tokyo Electric Power Company) officials I am going to only use information that I can get in more than one place.

A note on times; all times are going to be Japan Standard Time, so they will be a day ahead. Also for some events we don’t have a time stamp so I will just give them in approximate order, based on when they were reported.

March 11th

2:46 pm

- Three reactors active at Daiichi Nuclear Power Station, Units 1, 2 and 3. Unit 4-6 are in active. Unit 4 has fuel rods removed from maintenance. Units 5 and 6 are in cold shut down mode.

-9.0 earthquake strikes off of coast of Honshu prefecture.

-Reactors in affected area begin emergency shutdown procedures. Control rods are automatically inserted into the reactor cores to curtail fission. Shut down is successful, fission stops.

-Heat production by the cores falls to 6% of that during operation.


3:45-Approximately

-Massive tsunami waves strike the Japanese coast. Wide spread devastation occurs. Power grid is knocked out in the area around Daiichi and much of the north eastern coast of Japan.

-Tsunami strikes Daiichi plant. Generators and fuel storage on ocean side of plant. All diesel storage washed away.

-Power fails at Daiichi, coolant stops circulating in Units 1-3. Diesel back ups for the pumps fail due to tsunami damage and lack of fuel. Switching system also wiped out by tsunami.

-Circulation of water in cooling ponds stops.

- Temperatures in the cores begin to rise, increasing the amount of steam inside the reactors. Pressure increases, water level around the core fall.

-Fail safe, battery operated, cooling systems begins operation. Battery life estimated at 8 hours


5pm – Approximately

-Japanese officials call press conference and announce that there is a state of emergency for the area around the plant. They state that here is a problem with the cooling system in Unit 1 but that there has not been any release of radioactivity.

6:24pm

-2,000 residents nearest power plant advised to evacuate, but not ordered to do so.

-Technicians at the plants attempt to bring in new batteries and diesel generators to keep fail safe pumps going, and to start emergency back up cooling system.

-Kyodo News reports that radiation at Unit 1 control room is 1,000 times normal. Indications that the core is either uncovered or close to it.

- Operators vent steam from Unit 1 to lower pressure

10pm – Approximately

– Mandatory evacuation orders go out to 45,000 people within 6 miles of the Daiichi NPS.

11pm

– Sec. State Clinton announces that US Air Force brought coolant to the plant. This is most likely boric acid which is used as coolant and moderates nuclear reactions better than purified water.
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Japan Nuclear Watch: Monday Noon Update – 3 Reactors In Partial Meltdown

8:25 am in Uncategorized by Bill Egnor

This cutaway diagram shows the central reactor vessel and thick concrete containment in a typical boiling water reactor of the same era as Fukushima Daiichi 1 (image: www.world-nuclear-news.org)

Things continue to develop at the Daiichi and Daini nuclear power stations in Japan today. As you have already heard, a second reactor building exploded at Daiichi, it was the Unit 3 which had been experiencing the same problems as Unit 1, which also exploded.

What is believed to have happened is that hydrogen gas which was released along with the steam to reduce the pressure in the reactor vessel built up in the generation building and then a random spark ignited it. The building is seen to have the same kinds of damage that the Unit 1 building had.

Additionally Unit 2 has been reported to have exposed the rods and is in the process of at least a partial melt down at this time. What does this mean? It is likely that they will be experiencing the same pressure and hydrogen problems that Units 1 and 3 have had, with a similar danger of hydrogen explosion.

There has been a lot of talk that the reactor vessel (the actual structure of the reactor) might have been ruptured by these explosions because of the detection of Cesium (a fission by product). The main reason I find this unlikely at this time is that if the reactor vessel had failed two things would have happened.

The first is that the pressure within the vessel would have fallen to normal atmospheric pressure, this would have flashed most of the water in the vessel to steam by lowering the boiling point of that water. The second is that there would have been a massive increase in the amount of radiation detected.

While there have been reports of radiation detected at long distances (60 miles) we have to remember that venting of radioactive steam has been going on for three days now and that it could have traveled. We also are not being told how high this increase in radioactivity is. That is an important metric as very small increases can be detected.

We are now getting reports through the BBC that fuel rods in all three of these reactors are melting. The issue here is the way that they have been adding sea water to the reactors. It is being done through a system of fire hoses. They are using diesel powered pumps and the New York Times quotes and official as saying:

“The pump ran out of fuel,” Mr. Edano said, “and the process of inserting water took longer than expected, so the fuel rods were likely exposed from the water for a while.”

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