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

It is Sunday, 11:00 a.m. EDT here; 12:00 p.m. Sunday night in Japan.

It’s been three days since Japanese officials told us that three workers were exposed to potentially dangerous levels of irradiated water that had accummulated in the lower levels of the turbine/generator buildings connected to Reactor Unit 2 of the Fukushima Daiichi Nuclear Station.

Since then, the Japanese public has been exposed to revelations that there are similar puddles or pools of water in the turbine buildings for all four Units, that some of the “puddles” are 3-5 feet deep, and that others have highly elevated levels of radiation. How is it they’re just now discovering and reporting this? Officials still do not know the source of the water/leaks or its causes, nor what it means for the condition of each corresponding reactor or spent fuel storage pool.

And to top it off, the plant owner/operator, Tokyo Electric Power Comany (TEPCO) first reported radiation readings 10 million times normal at one unit, causing an immediate plant evacuation and risk of panic, only to announce later Sunday that these extreme measurements were in error. TEPCO officials apologized for the mistake, adding they were trying to get a more accurate measurement. The fact they didn’t immediately have a revised number, didn’t explain the mistake, and didn’t say when they’d have revised, accurate numbers was not reassuring. [Update: latest estimate says reading was 100,000 times normal levels.]

But take note, America; here is a picture of what an apology looks like.

Here’s what’s been reported in the last 24 hours or so. (See summaries at Kyodo News) from Sunday, March 27 Note: These levels were reported late Saturday; we don’t know whether the depths/readings are increasing or stable. Radiation levels from this Kyodo News report.]

Unit 1: Radioactive “puddle” in turbine room = 40 cm (about 15-16 inches)

Unit 2: Radioactive water level in lower turbine room = 1.0 meter deep; surface readings more than 1000 millisieverts/hour (the meter maxed out at 1000 milisieverts; actual measure unknown). Radioactive iodine-134 found at extremely high concentration of 2.9 billion becquerels per cubic centimeter; iodine-131 and cesium-137 also found, suggesting damage to core. According to Kyodo News:

At a radiation level of 1,000 millisieverts per hour, people could suffer a decrease in the number of lymphocytes — a type of white blood cell — in just 30 minutes, and half of the people could die within 30 days by staying in such conditions for four hours.

[Commentor lobster translates various dosage levels here. For a simplified comparison of various radiation levels and their possible effects, see this NYT chart.]

Unit 3: Radioactive water in turbine room = 1.5 meters deep; surface reading of 400 millisieverts/hour

Unit 4: The water level in turbine room = 80 centimeters (about 30 inches); radiation levels lower than other units, but recall that all of Unit 4′s fuel rod assemblies had been removed from the core to the spent fuel storage pool for inspection/maintenance prior to the earthquake.

What they don’t know: Where is the water coming from? Is some left from the tsunami? (The turbine building is on the seaward side of the reactor building, and the puddles are in lower level rooms.)

Are there leaks in pipes and/or valves coming into/going out of the turbine building from/to the reactor? In the same loop, there are also pipes/valves between the turbines and the condensor units, which turn the cooling steam back to water before returning it to the reactor. There’s another part of the loop for removing minerals from the water before returning it to the reactor, and those elements were reportedly (NYT) found in the water.

What is the source of the excessive radiation? Is it fuel/cladding deterioration within the core? A crack in the pressure suppression pool beneath the reactor (Unit 2)? Answering this requires analysis of the radioactive content of the water, but the levels of radiation are limiting their ability to conduct the analysis.

In the meantime, the dangerous radiation levels have limited other actions to regain control. Earlier hopes that connecting electrical power to each Unit would lead quickly to restoration of some normal cooling functions were dashed when they discovered pumps/valves in Unit 2 were damaged and must be replaced. We’ve had no recent word on progress there.

Off-site power is now restored to each Unit, but so far mostly for control room lighting. It remains unclear how much of the instrumentation is operable, which means they may not yet be able to get accurate readings on radiation, water pressures, temperature and levels inside each core, and they probably don’t yet know which pumps and valves are operable.

Reports a day ago said they were beginning to inject fresh water into the reactors. A later report Sunday said they hope to start injecting (which is correct?), and then they’ll try to get fresh water into the spent fuel storage ponds.

Recall that injections of sea water lead to corrosion and salt buildup around the fuel rods/assemblies in the reactor core and the spent fuel storage ponds. That buildup then limits the ability of cooling water to carry away heat, allowing the rods to continue to get hotter and become further damaged. So removing/limiting the salt buildup has become one of their all too many priorities.

Also, continuous sea water spraying and rain at the site outside have increased radioactive runoff into the sea. From Kyodo News:

Radioactive iodine-131 at a concentration 1,850.5 times the legal limit was detected in a seawater sample taken around 330 meters south of the plant, near a drainage outlet of the four troubled reactors, compared with 1,250.8 times the limit found Friday, the agency said.

So, in addition to the growing circle of civilian evacuations (now out to 30 kilometers), and bans/warnings about consumption of milk, produce, tap water, they now have to worry about ocean/sea-food contamination nearby. Officials are also warning water supply/treatment plants not to use rain water.

More as this nightmare unfolds.

Helpful Sources:

NHK live tv feed

Union of Concerned Scientists

Kyodo News: Japan Nuclear Crisis

Nuclear Power Plant Primer — good expert video

You can also find Unit by Unit status updates (pdf) at the IAEA site

NYT Radiation chart
Washington Post simple graphics

TEPCO press releases
NHK press releases
The Breakthrough Institute (including the Twitter feeds)