This post provides an update to the various situation summaries at Fukushima Daiichi. Please switch to using this post for comments on the latest status reports and news to hand (the old one is now out of date). For general comments on, use the FD Open Thread #2, and for analysis of the event with respect to future lessons for nuclear power, use this post. Full situation summaries from TEPCO, FEPC and JAIF are given at the bottom of this report.

This is a dramatic before and after photo of the Fukushima Daiichi plant. Click on the image to see more b/a images of the earthquake/tsunami damaged Sendai region (controlled with a swipe tool).

Below is a very brief summary of some key events of the last few days, since the previous status report:

1. There has been concern about salt accumulation in reactor vessels 1-3 (as steam evaporates the injected sea water, the salt is left behind, and if concentrations build to beyond the saturation point, it will begin to deposit and potentially insulate the fuel assemblies). However, NEI now reports the following welcome news:

Fresh water is being injected into the reactor pressure vessel at reactor 3 at Fukushima Daiichi nuclear power plant, Japan’s Nuclear and Industrial Safety Agency said. TEPCO said that radioactive materials discovered at the reactor 3 turbine building possibly came from water from the reactor system, not the spent fuel pool. TEPCO made that statement after collecting samples of contaminated water in the reactor 3 turbine building and conducting a gamma-emitting nuclide analysis of the sample. The reactor pressure and drywell pressure at reactor 3 remained stable on Friday, leading TEPCO to believe that “the reactor pressure vessel is not seriously damaged. Cooling efforts at Reactor 1 already had switched back to fresh water cooling. Reactor 2 is still being injected with seawater, but is expected to switch to fresh water soon.

The temperature at the bottom head of the reactor pressure vessels are now 149 C (unit 1), 104 C (unit 2) and 111 C (unit 3) — detailed data in reports below.

2. TEPCO Workers laying cables in the turbine hall of unit 3 stood in ankle-deep stagnant water and their feet were irradiated with beta rays (~180 mSv dose), with shallow burns, after ignoring their dosiometer warnings. They have since been hospitalised. Details in the reports below. 17 personnel have now received doses of >100 mSv, but none >250 mSv — the dose allowed by authorities in the current situation.

3. Water spraying continues on spent fuel ponds 2, 3 and 4, to ensure the uranium fuel rods remain covered. The temperature in unit 2 pool was recently measured at 52 C (see detailed data below).

4. On radiation: levels around the plant perimeter are relatively low and steadily decreasing. Levels of I-131 in drinking water supplies in Tokyo are now below regulated limits and restrictions have been lifted. The IAEA radiation monitoring data, at a distance of 34 to 62 km from Fukushima Daiichi, showed very low levels. To quote:

On 25th March, the IAEA radiation monitoring team made additional measurements at distances from 34 to 62 km from the Fukushima nuclear power plant. At these locations, the dose rate ranged from 0.73 to 8.8 microsievert per hour. At the same locations, results of beta-gamma contamination measurements ranged from 0.07 to 0.96 Megabecquerel per square metre.

5. World Nuclear News provides a new summary: Fukushima Daiichi two weeks on. To quote:

Investigations are now underway into the unexpectedly high level of contamination in the water, particularly as the basement of the turbine building is not a recognised radiation area. One theory is that there is a leak from the reactor circuit, but pressures in the reactor vessel indicate this must be elsewhere in the loop. Despite this disappointment, steady progress continues to be made on site. Instrumentation is being recovered at units 1, 2 and 4 and lights are on in the control rooms of units 1 and 3. Power connections have reached all the units and checks are underway before normal systems can be re-energised. The shared pond for used fuel pond has now been reconnected.

Here are some interesting photographs from inside the buildings, taken on 23 March by by the Operational Safety Inspector.

6. Geoff Russell (a regular BNC author on food and climate change issues) has a really good piece, reflecting on many of the issues discussed here over the last few weeks. His original title was: Japanese nukes … good news in a bleak landscape.

Some useful technical details are available from NISA Major Parameters 1800 March 25, and the NISA summary conditions report for each reactor (click on the diagram below to access the PDF):

Below is a situation update of the Fukushima Daiichi site, from TEPCO Washington office:

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(1) Result of the investigation on highly radiated workers.

Below are the investigation results of their working environment. Radiation dose rate of surface of the water is approximately 400 mSv/h. Result of gamma-ray nuclide analyses based on sampling of the stagnant water on the basement floor of the turbine building of Unit 1 of Fukushima Dai-ichi Nuclear Power Station. We are assessing radiation dose of 2 worker’s leg skin by beta ray. This incident would be caused because the workers regarded radiation dose of working area as low from survey result of radiation dose on March 23, it was about 0.5 mSv/hr at 5:00 and no major water puddle there. Workers continued working without recognizing change of work environment although their APD were alarming during the work TEPCO has thoroughly instructed its employees and contractor workers to pay attention to the alarm of their APD and evacuate when necessary.

Regarding this event, Fukushima Labor Bureau gave TEPCO verbal instructions. After summerising lessons learned and future measures to this event, TEPCO will report related government ministries and agencies to make sure radiation control thoroughly.

(2) High radiation water may come from the unit 3 reactor, not spent fuel pool.

As for the leakage of radioactive materials at Unit 3 turbine building, we assume the water came from the reactor. We collected sample of the contaminated water in the turbine building of Unit 3 and conducted the gamma-emitting nuclide analysis. We confirmed the following nuclides with short half-life.

Nuclides half-life (days) density (bq/cubic centimeter)

Iodine 131 8.06 1.2 x 10E6

Cesium 136 13.16 2.3 x 10E4

Barium 140 12.75 5.2 x 10E4

There are 148 fuel rods with less than one year of cooling period in the spent fuel pool at Unit 3. Those fuel rods were transferred to the spent fuel pool between Jun 23 and 28, 2010 having had more than 200 days of cooling period. Nuclides with short half-life had sufficient time for decay in the spent fuel pool, so it seems possible that the contaminated water in the turbine building is from the reactor.

We do not deny possibility that there might be certain damage to the reactor of Unit 3. Even should that be the case, as plant parameters such as the reactor pressure and D/W pressure is stable , we presume that RPV is not seriously damaged.

We are injecting seawater and from the night of March 25, fresh water into the reactor. The water turns into steam and comes out from the reactor vessel through the SRV, then depressurized at the suppression chamber and condensed to water. This flow of water is cooling the reactor. Having experienced fluctuations of temperature and pressure, the containment function might be loosened somewhere. In any event, the above is a possibility, not yet confirmed.

(3) Water injection into the pools and the reactors.

Unit 1: Sea water injection into the reactor pressure vessel, from 3:37 pm on March 25th, we have started to inject fresh water into it.

Unit 2: From 10:30 am on March 25th, seawater injection through Fuel Pool Cooling and Filtering System (FPC) was started. This finished at 0:19 pm.

Unit 3 From 5:35 am on March 24th, seawater injection through Fuel Pool Cooling and Filtering System (FPC) was started and finished at 4:05 pm.

Spraying at the spent fuel pool by Kawasaki City Fire Department was carried out from 1:28 pm to 4:00 pm on March 25th.

Unit 4: From 2:35 pm on March 24th, spraying water by the concrete pumping vehicle was conducted and ended at approximately 5:30 pm on the same day.

From 6:05 am on March 25th, seawater injection through Fuel Pool Cooling and Filtering System (FPC) was started and finished at 10:20 am.

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Here is the latest FEPC status report:

Radiation Levels At 7:00PM (JST) on March 25, radiation level at main gate (approximately 3,281 feet from Unit 2 reactor building) of Fukushima Daiichi Nuclear Power Station: 199.5 micro Sv/hour. Measurement results of environmental radioactivity level around Fukushima Nuclear Power Station announced at 7:00PM on March 25 are shown in the attached PDF file. English version is available at: http://www.mext.go.jp/english/radioactivity_level/detail/1303962.htm For comparison, a human receives 2,400 micro Sv per year from natural radiation in the form of sunlight, radon, and other sources. One chest CT scan generates 6,900 micro Sv per scan.

Fukushima Daiichi Unit 1 reactor At 11:00AM on March 25, activities for the injection of freshwater in place of seawater into the reactor core started and at 3:37PM, the injection of freshwater into the reactor core started. At 2:00PM on March 25, pressure inside the reactor core: 0.342MPa. At 2:00PM on March 25, water level inside the reactor core: 1.65 meters below the top of the fuel rods. At 2:00PM on March 25, pressure inside the primary containment vessel: 0.280MPaabs.

Fukushima Daiichi Unit 2 reactor At 10:00AM on March 25, the temperature of the spent fuel pool: 82.4 degrees Fahrenheit. At 10:30AM on March25, TEPCO began to inject seawater into the spent fuel pool via cooling and purification line, until at 12:19PM (approximately 38 tons in total). At 11:00AM on March 25, activities for the injection of freshwater in place of seawater into the reactor core started. At 2:00PM on March 25, pressure inside the reactor core: -0.016MPa. At 2:00PM on March 25, water level inside the reactor core: 1.4 meters below the top of the fuel rods. At 2:00PM on March 25, pressure inside the primary containment vessel: 0.12MPaabs. As of 7:00PM on March 25, approximately 96 tons of water in total has been injected into the spent fuel storage pool. As of 7:00PM on March 25, external power generation is connected and the functionality of the electric devices is being checked. As of 7:30PM on March 25, the injection of seawater into the reactor core continues.



Fukushima Daiichi Unit 3 reactor At 11:00AM on March 25, activities for the injection of freshwater in place of seawater into the reactor core started and at 6:02PM, the injection of freshwater into the reactor core started. At 1:28PM on March 25, Kawasaki City Fire Department began to shoot water aimed at the spent fuel pool until 4:00PM (approximately 450 tons in total). At 2:00PM on March 25, pressure inside the reactor core: 0.038MPa. At 2:00PM on March 25, pressure inside the primary containment vessel: 0.1089MPaabs. At 2:10PM on March 25, water level inside the reactor core: 1.9 meters below the top of the fuel rods. As of 7:00PM on March 25, approximately 4,497 tons of water in total has been shot to the spent fuel storage pool.

Fukushima Daiichi Unit 4 reactor At 6:05AM on March25, TEPCO began to inject seawater into the spent fuel pool via cooling and purification line, until at 10:20APM. At 7:05PM on March 25, TEPCO began to shoot water aimed at the spent fuel pool, with a specialized vehicle normally used for pumping concrete. As of 7:00PM on March 25, approximately 685 tons of water in total has been shot to the spent fuel storage pool. As of 7:00PM on March 25, external power generation is connected and the functionality of the electric devices is being checked.

Fukushima Daiichi Unit 5 reactor At 3:00PM on March 25, the temperature of the spent fuel pool: 98.4 degrees Fahrenheit. At 3:00PM on March 25, the temperature of the water in the reactor core: 129.0 degrees Fahrenheit.

Fukushima Daiichi Unit 6 reactor At 3:00PM on March 25, the temperature of the spent fuel pool: 69.8 degrees Fahrenheit.

Fukushima Daiichi Common Spent Fuel Pool As of 7:00PM on March 25, approximately 130 tons of water in total has been injected to the spent fuel storage pool.



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Finally, the latest Japan Atomic Industrial Forum summary table (21:00 March 25):