March 15th, 2011 – 1930 EDT – USNRC Emergency Operations Center Status Update

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Earthquake/Tsunami Status Update March 15, 2011 1930 EDT

USNRC Emergency Operations Center Status Update

March 15, 2011
Earthquake / Tsunami Status Update
Compiled by Executive Briefing Team
Caution – This information may be dated and is subject to constant change.
Changes/Additions from previous updates are underlined

Status of Japanese Facilities (This information is compiled from available sources, including press releases by the Tokyo Electric Power Company (TEPCO) and information from the International Atomic Energy Agency (IAEA)).

IAEA reports that at 1331 UTC on March 15, 2011 a 6.1 magnitude earthquake occurred in eastern Honshu, approximately 100 km from the Hamaoka nuclear power plant. Operational units at the plant remain in safe status after the earthquake.


Background:

There are 14 operational Boiling Water Reactors (BWRs) proximal to the earthquake zone (6 at Fukushima Daiichi, 4 at Fukushima Daini, 3 at Onagawa, and 1 at Tokai)

Current Understanding of Japanese Reactor Status (This information is compiled from TEPCO press releases and IAEA information releases.)


Fukushima Daiichi

Japanese national government instructed evacuation for local residents within a 20km radius of the site boundary and sheltering in place out to 30 km for residents who stayed behind. IAEA confirms a no fly zone out to 30 km around the Fukushima Daiichi plant. As of 1830 EDT on March 15, 2011, there have been no updates to protective actions.

Japanese authorities classified the event at a Level 4 “Accident with Local Consequences” on the International Nuclear and Radiological Event Scale (INES) based on radioactive dose measurements at the site boundary exceeding limit values.

All available information indicates that the majority of releases from the Fukushima site have been carried out to sea by the prevailing winds. Forecast meteorological data for the 24 hour period (until 1700 EDT on March 16, 2011) indicates wind remaining toward offshore (N, NW).


Units 1, 2, and 3: shutdown due to earthquake

– At approximately 1000 EDT (March 14, 2011), Unit 2 core was again uncovered.

Units 4, 5, and 6: shutdown due to outage, prior to earthquake

All Units: all AC power on-site lost.

Operators and other personnel not directly involved in water injection have been evacuated. 40-50 persons have been left onsite to mitigate accident.


Unit 1

Core damage occurred due to insufficient cooling water caused by loss of offsite power and onsite diesel generators following the tsunami
– As of 2200 JST (0900 EDT) on March 14, it is reported that sea water is being injected.
– Containment described as “functional.”
– Hydrogen explosion from ,overheated fuel-water reaction has damaged reactor building roof.
– Sea water is being injected with reported stable cooling
– The spent fuel pool level is unknown
– High radiation levels reduced to 600 mSv/hour (60 mrem/hour) at 0200 EDT on March 15, 2011 at site gate. (Site gate is same for each unit).

Unit 2

– Core damage occurred due to insufficient cooling water caused by loss of offsite power and onsite diesel generators following the tsunami
– Reactor Core Isolation Cooling (RCIC) has failed.
– Hydrogen explosion from overheated fuel-water reaction damaged the reactor building
– Sea water injection restarted with reports of non-stable conditions.
– There are reports of a loud sound at Unit 2 in the vicinity of the suppression chamber. It was reported at 0730 EDT on March 15, 2011 that containment is intact (better than Previously thought).
– High radiation levels reduced to 600 mSv/hour (60 mrem/hour) at 0200 EDT on March 15, 2011 at site gate. (Site gate is same for each unit).
– The spent fuel pool level is unknown

Unit 3

– Core damage due to insufficient cooling water caused by loss of offsite power and onsite diesel generators following the tsunami
– Sea water is being injected with reported stable cooling
– Hydrogen explosion from overheated fuel-water reaction has damaged reactor building roof.
– Primary containment described as “functional.”
– There is no spent fuel pool information
– High radiation levels reduced to 600 mSv/hour (60 mrem/hour) at 0200 EDT on March 15, 2011 at site gate. (Site gate is same for each unit).

Unit 4

– First fire in the reactor building was a small generator lube oil fire. IAEA reports that fire was put out at 2200 EDT, March 14.
– High radiation levels reduced to 600 mSv/hour (60 mrem/hour) at 0200 EDT on March 15, 2011 at site gate. (Site gate is same for each unit).
– Second fire began 1645 EDT, March 14, 2011 in reactor building. Reports indicate that this fire is not yet contained. TEPCO is determining whether to use helicopter or fire truck to fight fire. Fuel reported to be uncovered.
– Radiation level in the area of unit 4 reported to be 30R/hour following second fire.
– There is a possible water loss from the spent fuel pool and operators are having difficulty providing adequate cooling and water level to the pool.
– There are reports of possible hydrogen explosion due to uncovered fuel in the spent fuel pool (awaiting visual confirmation).
– High radiation dose rates measured between Units 3 and 4, source is suspected to be the partially uncovered Unit 4 spent fuel pool.

Unit 5

– The reactor is stable.
Spent fuel pool is reported to be heating up.

Unit 6

– The reactor is stable.
– Spent fuel pool is reported to be heating up.


NRC Evaluation of Radiation Measurements from the USS Ronald Reagan and USS George Washington

On the morning of March 13, 2011, Naval Reactors notified the NRC that dose rates were being measured from the flight deck of the USS Reagan that was -130 nautical miles off the Japanese coast. Dose rates from the overhead “plume” were approximately 0.6 mrem per hour gamma with no measurable activity on the ship surfaces.

The NRC had received an IAEA report showing dose rates of 100 mrem/hr up wind at the site boundary measured – 20 hours earlier and press reports for the previous (Jay of plant venting.

Given the meteorological conditions; wind speed of 3-5 mph and the calm ‘Class D and E’ weather stability for the 20-24 hour time period, a plume with low dose rates from the venting is credible at this location.

NRC staff believes that US Naval readings are not inconsistent based on reports and shine dose measurements received from Japanese officials during venting from Fukushima Daiichi Units 1,2, and 3.

The Navy sent the contamination samples to a base in Japan to perform an isotopic analysis to determine the actual radio-nuclides. The principle radionuclides identified were iodine, cesium, and technetium, consistent with a release from a nuclear reactor.

The US 7th Fleet has repositioned its ships out of the downwind plume direction from the Fukushima Daiichi Nuclear Power Plant after detecting low level contamination in the air and on its aircraft operating in the area.

The US Navy identified radioloqical data from the USS Georqe Washington located at Yokosuka Base at 0300 EDT on March 15, 2011 that showed an air sample of 7E-9 uCi/mL, from which the Navy estimated a dose rate of 1.5 mrem/hour.


Reactor Safety Team Worst Case Analysis

Hypothetical Worst Case Daiichi Units 1, 2 and 3 Accident Sequence Based on our Knowledge of Current Plant Conditions

In this hypothetical event in which no cooling water is added to the core, the water level in the core will decrease, exposing the top of the core to a steam environment and a subsequent heatup of the fuel rods.

As the water continues to boil and recede toward the core bottom, the heatup rate of the rods will increase rapidly resulting in fuel cladding failure and melt. With the continued lack of cooling water, the melting rods will relocate toward the bottom of the core and eventually into the lower plenum of the reactor vessel. Molten fuel and core debris entering the lower plenum will then cause the lower plenum liquid to boil.

If cooling water is added to the drywell to a level above the top elevation of the lower plenum, lower head failure can be prevented. With no cooling water added to the drywell, the lower head will fail by creep rupture allowing molten fuel to enter the drywell. Moreover, the absence of cooling water to the drywell could also result in a containment failure.

With cooling water added to the drywell, however, a containment venting capability is also needed to preclude failure from over-pressurization. A containment failure will result in a large radioactive release to the environment.

Please note that failure to add water to the core and drywell is a hypothetical worst case event that will result in containment failure and radioactive release to the environment.


Protective Measures Team (PMT) Worst Case Analysis

On March 15, 2011, the PMT ran RASCAL offsite dose estimations for a hypothetical x-vessel core failure with loss of containment at a boiling water reactor (BWR) similar to Fukushima Daiichi Unit 2 with loss of containment.

Two estimates were run:

1) no change in wind direction (wind toward Tokyo) and

2) with the predicted wind shift counterclockwise over the island and back out to sea.

For the steady wind direction scenario, Protective Action Guides (PAGs) (>1 rem Total Effective Dose Equivalent (TEDE) and >5 rem Committed Dose Equivalent (CDE)) were exceeded at 50 miles beyond Unit 2.

For the wind shift scenario, PAGs were exceeded between 30 to 40 miles.

Another RASCAL run with assumptions to model the Fukushima Unit 4 spent fuel pool (SFP) was updated to reflect a spent fuel inventory of 1331 bundles.

Since observed meteorological data is unavailable, forecast meteorological data for the 24 hour release period, which indicate wind shifting offshore, were used.

For the meteorological conditions utilized, at 20 miles, the PAG for TEDE is 1.4 rem, slightly above the 1 rem PAG. At 30 miles, the TEDE is 0.9 rem.

As of 1900 EDT on March 15, 2011, we believe the runs are bounding for all four units. The PMT is working to update the RASCAL run for the Unit 4 spent fuel pool, using actual meteorological parameters.


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