Over the past several days, it seems like there is a lot of misinformation and disinformation being floated regarding what's happening with the troubled nuclear Fukushima nuclear plants in Japan. As developments warrant, I'll try to clarify things a bit, in as non-technical terms as possible.
By way of credentialing myself, I'm an Institute for Nuclear Power Operations-certified systems engineer in GE Boiling Water Reactors (BWRs), and worked for over 20 years in the industry with a large architect engineering (A/E) firm and an electric company with a nuclear portfolio. I've worked directly at four BWR plants, including one similar to the Fukushima plants. Ok, with that out of the way...
Disclaimer - Information being released by the plant owner (Tokyo Electric Power Company), the Japanese government oversight agency (NISA), reactor design company (GE Hitachi) has been scant. I assume this is because they're busy trying to gain control of a bad situation.
Having spent time in the industry, and having been exposed to the public relations apparatus of the industry, I have very little faith in the limited information that is being released. The bottom line: take everything you read or hear about the events at the Fukushima plants with a grain of salt. There is a lot of anecdotal information that leads to some obvious conclusions, but there is very little hard data that allows even someone with my experience to fully understand what's going on. If someone on TV says the reactor core is melting out of the bottom of the reactor vessel, don't believe them. If someone on TV says there are flowers blooming and everything's peachy in the nuclear world, don't believe them, either. More after the jump.
My first WTF? diary was a Q&A, giving a high level overview of what appears to be happening at the Fukushima facility. It also drew a few conclusions based on observable and reported data. I'll try to stick to that, and avoid speculation.
Here's a side-by-side comparison, before and after, of the Unit 1 reactor building, which suffered an explosion on Saturday from a buildup of hydrogen gas in the building:
Notice that the top part of the building is basically destroyed. The hydrogen explosion that occurred was very powerful, and it's not surprising that the top part of the building is completely gone. This is a reinforced concrete structure, feet thick. It would also not be surprising to find that the pressure wave from the first explosion destroyed or disabled most electrical, controls, instrumentation, and mechanical equipment inside of the building. So, the operating assumption needs to be that any remediation that's happening is with the total absence of hard data of the conditions inside the reactor vessel itself. And all work that's ongoing to control the reactor is manual - in other words, there are some heroic efforts being made by workers to manually reconnect and locally operate pumps, valves, and other equipment needed to flood the reactor vessel with any kind of cooling water (fresh or seawater) or nuclear reaction moderator, such as boric acid (boron absorbs neutrons and lowers reactivity in the core).
Here's a cutaway drawing of the plant:
Transposing the drawing with the above photo, a couple of things are pretty clear.
- The new and spent fuel pools (the swimming pool looking things toward the top of the drawing) are now, at a minimum, completely exposed to the environment. It's impossible to determine at this time if the cooling water flow to the pools has been maintained, or if the spent fuel is exposed and releasing radioactivity. This report isn't encouraging, but there's almost no information available regarding status of the spent fuel pool.
- All equipment used to access the internals of the reactor vessel (where the reactor core is housed) is gone. The gantry crane above the vessel, which is used to remove the vessel head and other shielding around the top of the vessel, is not even visible in the photo.
- There are most likely piles of rubble everywhere in the building, making accessibility to equipment and piping difficult, if not impossible.
The bottom line is that the plant operators most likely have very little (if any) hard data or instrumentation to tell them exactly what's happening inside of the reactor vessel itself.
Two other incidental pieces of information are concerning. The Japanese government has apparently evacuated, or is ordering the evacuation, of 200,000 people in the area around the plant. This is precautionary, to an extent, but also an indication of how serious this thing really is. Additionally, the U.S. Navy has pulled back ships because of detected airborne radiation out at sea, and 17 sailors have been contaminated during relief efforts.
All of the incidental information adds up to a very serious picture.
Then, yesterday evening, another hydrogen explosion occurred, this at the Unit 3 plant. You can literally see large chunks of the building falling back to earth from the explosion cloud. This looks bigger than the explosion at Unit 1 on Saturday.
It is almost impossible for me to imagine how the fuel pools have remained intact in either of the blown reactor buildings. That's my primary concern at the moment, and very few in the media are asking the question or evaluating the consequences. I suppose that's not surprising - they're looking for the TMI or Chernobyl - a full core melt inside the reactor vessel.
I also continue to have concerns about whether or not one or more of the reactors has suffered at least a partial failure to shut down, ie. failure of all control rods to insert into the reactor core. According to Sky News, TEPCO has said that the Unit 2 reactor core was uncovered. And that's in one of the intact buildings.
As more information becomes available today, I'll endeavor to update this diary.
Update, 12PM EDT: One thing that occurred to me a little while ago is that simply getting engineers, equipment, and supplies to the plant site has to be a logistical nightmare because of the tsunami, and there's only so much backup equipment and materials onsite. This may have as much of a long term impact on prospects for recovery as anything else.
In the comments below, I noted that this is truly an unprecedented event in the history of nuclear energy. It really is. The challenges at each of the individual Fukushima reactors are no doubt different, and there is only so much technical expertise to go around. Also, at least at units 1 & 3, there's likely no solid data on what's happening inside the reactor cores, simply because all of the instrumentation was probably impacted by the explosions.
The media continues to be very conservative in addressing the potential impact (long and short term), and what's actually happening at the plants. I continue to take all media reports with a grain of salt. All information and data so far has been anecdotal at best, and downright misleading in some cases.
Update 2, 3PM EDT: Big hat tip to commenter Panglozz, who provided a link to an aerial photo of the Unit 1 and Unit 3 reactor buildings, which experienced explosions on Saturday and Sunday, respectively. I've taken the liberty of cropping and zooming the individual units, and I'll provide some commentary on what I see. Here's a link to the original hi res photo:
Unit 1: This is the plant that experienced an explosion on Saturday:
What I see here is that it appears as if the roof of the reactor building cleanly pancaked onto the refueling floor. There is no equipment really visible. The gantry crane in the building is gone. The spent and new fuel pools are not visible, which is clearly concerning - either the pools are gone, or totally buried underneath the roof debris (if what I suspect about pancaking is correct). Either way, there's no way to tell what the status of the pools might be by looking at this photo.
Unit 3: This is the plant that experienced an explosion on Sunday evening, U.S. time.
What a mangled mess. The explosion was clearly more powerful at Unit 3. Again, there are no fuel pools visible, which means either they are buried under the debris, or that they no longer exist. So, where's the spent fuel? Who knows. If the pools do in fact still exist, they're inaccessible. The bottom line is that there's no way to get around the refueling floor, and the building actually looks in much worse shape than Unit 1. It also appears as if either the ejecta from the explosion landed on the Unit 3 turbine building (foreground), or that the turbine building was also significantly damaged in the explosion.
Either way, my concerns are heightened regarding operability of any equipment in either Unit 1 or Unit 3, and particularly about the status of the spent fuel pools in both units.