Fukushima 1 Nuclear Accident Day 13: Wednesday, 23 March

00:34
The BBC reported that external power cables were connected to all units at Fukushima I nuclear power plant and lighting was back on again in the control room of unit 3.
10:15
MSNBC reports that at some point over the prior 24 hour period, "emergency crews dumped 18 tons of seawater into nearly boiling storage pool holding spent nuclear fuel at Unit 2, cooling it to 105 °F (41 °C)".
19:00
Reported I-131 plume across Pacific ocean and USA. Data collected by CTBTO and reported by ZAMG.
21:00
TEPCO status report
Status of Fukushima I at 21:00 on 23 March

Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6
Power output (MWe) 460 784 784 784 784 1100
Type of reactor BWR-3 BWR-4 BWR-4 BWR-4 BWR-4 BWR-5
Status at earthquake In service -> shutdown In service -> shutdown In service -> shutdown Outage Outage Outage
Core and Fuel Integrity (Loaded fuel assemblies & mass estimation) Damaged
(400 ≈ 83 t UO2 singly)		 Damaged
(548 ≈ 114 t UO2)		 Damaged
(548 ≈ 106 t UO2 8 t PuO2)		 No fuel rods Not damaged
(548 ≈ 114 t UO2)		 Not damaged
(764 ≈ 148 t UO2)
Pressure vessel integrity Unknown Unknown Unknown Not damaged Not damaged Not damaged
Containment integrity Not damaged Damage suspected Might be ”Not damaged” Not damaged Not damaged Not damaged
Core cooling system 1 (ECCS/RHR) Not functional Not functional Not functional Not necessary Functional Functional
Core cooling system 2 (RCIC/MUWC) Not functional Not functional Not functional Not necessary Functioning (in cold shutdown) Functioning (in cold shutdown)
Building integrity Severely damaged Slightly damaged Severely damaged Severely damaged Vent hole opened on rooftop to prevent hydrogen explosion Vent hole opened on rooftop to prevent hydrogen explosion
Reactor pressure vessel, water level Fuel exposed Fuel exposed Fuel exposed Safe Safe Safe
Reactor pressure vessel, pressure Stable Unknown Unknown Safe Safe Safe
Containment pressure Stable Stable Decreasing after Mar. 20th increase Safe Safe Safe
Seawater injection into core Continuing Continuing Continuing Not necessary Not necessary Not necessary
Seawater injection into containment building (confirming) To be decided (confirming) Not necessary Not necessary Not necessary
Containment venting Temporarily stopped Temporarily stopped Temporarily stopped Not necessary Not necessary Not necessary
Integrity of fuel in Spent Fuel Pool (Stored spent fuel assemblies & mass estimation) Unknown
(292 ≈ 60 t)		 Unknown
(587 ≈ 122 t)		 Possibly damaged
(514 ≈ 106 t)		 Possibly damaged
(1331 ≈ 312 t)		 Not Damaged
(946 ≈ 196 t)		 Not Damaged
(876 ≈ 182 t)
Cooling of the Spent Fuel Pool (SFP) Water injection to be considered Seawater Injection conducted on Mar. 20th Water level low,
Water injection continuing,
effectiveness has been confirmed		 Water level low,
Water injection continuing,
Hydrogen from SFP exploded		 Pool cooling capability was recovered Pool cooling capability was recovered
Main Control Room Habitability & Operability Poor due to loss of AC power Poor due to loss of AC power Poor due to loss of AC power (Lighting has been recovered) Poor due to loss of AC power (Lighting has been recovered) Not damaged (estimate) Not damaged (estimate)
Environmental effect (NPS border)

The Main Gate: 265.4 µSv/h at 15:00, Mar. 23. Radioactive nuclides exceeding the legal standard were detected in milk produced in Fukushima and Ibaraki prefectures and spinach and some other vegetables produced in Fukushima, Ibaraki and other prefectures. Also, radioactive Iodine exceeding the standard set by Nuclear Safety Commission was detected in tap water in Fukushima prefecture. The level of the radioactivity detected is low enough not to do harm to the health of people who take those products or water for a limited time. Monitoring results of seawater sampled at coasts in the surrounding area of the station showed that radioactive Iodine, I-131, and Cesium, Cs-134, 137, exceeding the regulatory limit were detected.
Evacuation radius 20 km from Nuclear Power Station (NPS). People who live between 20 km to 30 km from the Fukushima I Nuclear Power Station are to stay indoors.
INES (estimated by NISA) Level 5 Level 5 Level 5 Level 3 - -
Remarks Immediate threat is damage of the fuels in the fuel pool outside the containment vessel. The operation for spraying water to the pool is continuing at Unit 3 and 4.

Work to recover AC power for Unit 1 through 6 is in progress. External AC power has reached to Unit 2, 4, 5 and 6 and is now available in all the units. Integrity check of electric equipment is going on in each unit, which must be done before energizing them. Lighting has been recovered at Unit 3 Main Control Room. External AC power has replaced with the emergency diesel generator in Unit 5 and 6.

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