March 11th, 2011 – What the NRC knew as of 11:00 pm

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What do we know as of 11 pm 3/11/2011

1. TEPCO press release indicates loss of all power at Units 1, 2, and 3 at 1:46 AM Eastern time (3:46 PM local Japan time)
2. TEPCO press release indicates Unit 4 shutdown due to earthquake, Units 5 and 6 were already in an outage and shutdown.

a. No more information Unit 4 is available.

3. TEPCO press release indicates units 1, 2, and 3 automatically shutdown at 1:46 AM Eastern time (3:46 PM local Japan time)
4. TEPCO press release indicates all three Units offsite power was lost at approximately 1:46 AM Eastern time (3:46 PM local Japan time) leading to automatic startup of emergency diesel generators
5. TEPCO press release indicates at 2:41 AM Eastern time (4:41 PM local Japan time), emergency diesel generators shutdown for Units 1, 2, and 3 resulting a complete loss of Alternating Current for all units.
6. The staff believes that DC power via batteries is all that remains.

a. These batteries would have been exhausted without mitigation in approximately 4-6 hours which is 6:41 – 8:41 AM Eastern time (8:41 – 10:41 PM local Japan time)

7. IAEA report as of 2:45 PM Eastern time (4:45 AM 03/12/11 local Japan time) indicates that Unit 1 water level was approximately 51 inches above the top of the core. For Unit 2, core coverage was approximately 138 inches. For Unit 3, IAEA indicated that power is being supplied.
8. The staff believes the worst case scenario for the Unit I would be core damage in 13 hours or about 4:00 PM Eastern time (6:00 AM 03/12/11 local Japan time).

a. This assumes immediate loss of AC and no mitigation (apparently not the case for this situation).

9. Based on staff calculations worst case scenario for Unit 1 would lead to significant offsite releases at approximately 20 hours assuming no mitigation.

a. This assumes immediate loss of AC and loss of Isolation Condenser (apparently not the case for this situation).

b.. Evacuations were ordered for a two mile radius early in the event.

c. Given this order, protection of the public is being addressed.

10. As of 10:44 PM Eastern time (12:44 PM 03/12/11 local Japan time), Units 1 and 2 have been without alternating current power for 20 hours.
11. Evacuations extended to 10 km. as of approx. 7:00 PM Eastern time (9:00 AM local Japan time).
12. NRC Phone call with Exelon (VP of Quad Cities Site)

a. Exelon simulated the Fukushima event with Quad Cities simulator – simulator results significantly different from the Fukushima plant indication (containment pressure predicted by simulator was 2.5 psi vs. approximately 85 psi reported for Unit 1)

b. Diesel fuel tanks for the diesels were severed by the 35-40 ft tsunami.

c. Engineering building apparently collapsed.

13. Phone call with GEH (Hernando Madronero)

a. GEH indicated that there has been no direct contact with TEPCO.

b. GEH provided similar information as Exelon call.

14. E-Mail from Shunsuke Kondo, Chairman of the Japan Atomic Energy Commission to Daniel Poneman, Deputy Secretary DOE – UPDATE Fukushima Daiichi Unit 1

a. Information recently obtained is not inconsistent with NRC previous hypothesis which was based on wire reports and public information

b. High radiation associated with containment venting suggest core damage, the extent of which is not known

c. TEPCO appears to be taking extraordinary measures to supply water to the reactor, including using power supply trucks and batteries to supply power. The reactor vessel level is stabilized, possibly indicating a measure of control

d. TEPCO is venting containment under high radiation conditions; wind direction is to see

Summary:

No additional information has been provided to reverse our previous hypothesis. Assuming no mitigation, Unit 1 would lead to core damage in approximately 13 hours
after the earthquake and significant offsite releases at [approximately 20 hours.

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