Fukushima Unit 4 SFP never went dry

[JimD]

The progress in cleaning up Fukushima is going very very slowly. But progress is being made. A new water purification system went into operation within the last week. That will allow TEPCO to get rid of the rapidly accumulating water with radioactivity in it. Some debris from the damaged plants has been removed but a huge amount of cleanup remains. A few workers have also received doses up to around 70 REM - serious doses. Not enough to cause immediate health issues but enough that some worry about their future is warranted.

Another interesting update is that the NRC has admitted that, contrary to what NRC Chairman Jaczko claimed in March, the spent fuel pit at Unit 4 did not go dry. The fuel is very likely to be fully intact. Good news for TEPCO and Japan. Might be bad news for Jaczko who is already receiving congressional attention for unilaterally shutting down NRC review of Yucca Mountain. Here is a link to a news piece:

http://www2.wnct.com/news/2011/jun/1...ke-ar-1123735/

Jim

[gerti]

Great, so they can get #4 ready in time for the next disaster. Now that 1000 square kilometers in one of the most densely populated countries are uninhabitable, they might as well go to town.

[LCHIEN]

of course that's the only good news. They finally admitted in the last couple of weeks that the reactors 1, 2, and 3 had significant core melting within 5 hours of loss of cooling... Something that every expert seemed to have assumed but TEPCO was unwilling to admit.

That complicates the cleanup even more, rather than just pulling rods out as per normal procedure for refueling they will have to fish out the bits and pieces of radioactive material and melted pieces of fuel rods in a melted slurry at the bottom of the primary containment vessel, which is very likely to have significant heat damage.

[JimD]

TMI had a little fuel melting too and the fuel was left in the bottom of the vessel, at least for now. When iodine is measured outside the plant we know that the UO2 pellets have been exposed to the coolant. It is not otherwise in the water to be released. So we knew very early there was fuel damage (TEPCO wasn't admitting it but their nuclear engineers knew it too, not sure what the top level understood). It will be a long time before that becomes a significant factor in the cleanup. A reasonable course of action is to just stabilize the plant and leave the reactor vessel alone for 10+ years to let the radioactivity die down to a small fraction of what it is now. That minimizes cost and maximizes safety. Near terms actions are to stop the leakage of water with activity from the plant site, get a better setup for cooling of the pools and reactors, and clean up all the debris from the hydrogen explosions. They will be working on at least the last item for months if not a year or more. I haven't seen a good timeline yet.

A separate cooling system for the spent fuel pools is in place at at least one unit now with plans to get on all of them soon. A limiting factor is all the debris in the way of dropping the pipes into the pool. High radioactivity makes it challenging to get the debris out of the way.

Useful surveys of the extent of the contamination of the surrounding area are underway. I don't think we really know enough to judge what the timeline or difficulty will be in the wider cleanup. One thing we do know is that the radioactivity release was on the order of 10% of Chernoybl. That is still a lot but helps to get it in the right perspective.

Jim

[gerti]

A new water purification system went into operation within the last week

German press reports that system only lasted 5 hours before higher than expected radiation damaged it.

[sailor55330]

This is one of the major reasons I just don't think we are ready for nuclear fuel. This accident is leaving a site that will need to be stabilized for 10 years before it's really "safe" enough to clean up. We are talking radioactive release levels of "only 10% of Chernobyl" in casual terms. Nuclear fuel might be cheaper, but ther risks are high when something goes wrong. I believe that Fukishima had many of the current industry safeguards in place, but it was still pretty close to a major global disaster. I don't honestly see how anyone can feel "good" about what happened at Fukishima. It was a major accident that wasn't far from a global incident. I do understand that it took two simultaneous natural disasters to trigger it and that occurence is very rare, but it happened and no one thought it would. Until we can completely control the enviroment that a nuclear reactor runs in, the "what if" factor is still there and when it does hit (and it has and does), the potential consequences are very severe.

[JimD]

The water puification system had a leaky valve but it wasn't damaged from radiation, at least that is not the report I have. It is expected back in operation very soon, probably is already.

It would be foolish to argue that nuclear power doesn't have risks. The problem is that there is no way to make electrical power that doesn't have risks. The question is which risks you want to have. The reasons I like nuclear is that the fuel is so relatively inexpensive that we can afford to spend a lot of money making it as safe as possible. Coal kills far more people from mining, emits more radiation, and potentially impacts the environment substantially from the CO2 and other effluents. Gas is cleaner but more expensive and not available everywhere. Solar and Wind seem clean until you understand how the installations are built and then they don't seem so clean. Solar and wind are also not dependable - we need electricity when the sun doesn't shine and when the wind doesn't blow. Noise polution and damage to birds are also a problem with wind. Hydro is good but not possible much more than is already in place in this country and there are some issues with wildlife. Oil is dirty and expensive and has air pollution problems similar to coal and gas (light oil more similar to gas, heavy more similar to coal). Nuclear is far from perfect but I think it is the best alternative when hydro is not available. Others are welcome to their opinion, of course.

Jim