PEER REVIEW – Electrical

FUKUSHIMA DAIICHI POWER LOSS

There was a back-up 66kV transmission line from the transmission network of Tohoku Electric
Power Company, but the back-up line failed to feed Unit 1 via a metal-clad type circuit (M/C) of
Unit 1 due to mismatched
sockets.

The EQ caused loss of off-site supply, because of loss of all seven grid connections to the site.

The earthquake caused a lot of damage in the switchyards at the NPP
At the nearby Shin-Fukushima substation to whichit is connected and to the circuits
between them, including:
o Collapse of one transmission tower, built on sloping ground, because of a
landslide caused by the earthquake;
o Damage to underground cables by subsidence;
o Collapse of several high voltage circuit breakers;
o Distortion, damage or collapse of several line switches (disconnectors);
o Failure of suspension insulators;
o Failure of an overhead earth wire (ground wire) which fell on the equipment below
it

The height of the tsunami at the Fukushima Daiichi flooded the site and the equipment that was
damaged by the flooding included
o most of the high voltage switchyards
o high voltage distribution boards at the NPP

Because of the extent of the damage caused by the earthquake and flooding,
o it was not possible to restart the diesel generators
o it was not possible to restore electrical power from the grid for several days
o batteries were completely discharged after a few hours.

Loss of the external power supply
Okuma 1L,2L : Breakers were broken due to the earthquake
Okuma 3L : Under modification after the earthquake

Units 5 & 6 Pylons damage by the earthquake caused loss of off-site power supply

Two mobile power supply (500kv) trucks were brought, each feeding power to two 6.6kv/
480V transformers

9 km of temporary wiring was laid and fed units 1-4 and the Rad Waste Building

Motors were replace (TBD which motors)

By the end of March 2011 the following was accomplished to re-route power to Daiichi plants

SHIN-FUKUSHIMA SUBSTATION

A direct tie from the 500 KV incoming feeders to the substation was re-routed
through tower number 26 and futuba tower number 2 directly to units 5 & 6

A direct tie from the 500 KV incoming feeders to the substation was routed
through a temporary transformer cart (reduced to 275 kv) and then to the
Okuma3L line to a temporary MC cart and switch cart. Power from the switch cart
fed power to units 3 and 4

A direct line (66kv) from Toden Gensiryoku Line (Tohoku Electric Power) was fed to a
backup transformer (66/9.9 kv) and fed power to units 1 & 2

By Mid-May the following was accomplished
• The temporary transformer cart at the Shin-Fukushima cart was removed and the 500KV
fed directly through the same route above to temporary switch cart, transformer cart and
MC cart at the Daiichi substation and fed power to units 3 & 4
• The Okuma line 2L was restored and fed power to a temporary switch cart, transformer
cart and MC cart at the Daiichi substation and fed power to units 1 & 2
• The direct line (66kv) from Toden Gensiryoku Line (Tohoku Electric Power) which fed to
a backup transformer (66/9.9 kv) at the Daiichi substation was used as a backup power
source for units 1 & 2

The following table will show the plants and a chronology of actions for electrical restoration

FUKUSHIMA DAIICHI ELECTRICAL RESTORATION

Date Operation and Restoration Status

Date Operation and Restoration Status
Power Access/Restoration

Status Immediately

after 1F-1,2 Shutdown

3/11/13 Temporary MCR lighting on (Temporary small engine generator)
3/12/13 Power source for Unit 1 Instrument restored (Temporary small

engine generator)

Power source for Unit 1 Instrument restored (power source cart)

Temporary small engine generator destroyed by H2 explosion

Temporary MCR lighting on (another temporary small engine

generator)

3/19/13 Backup transformer ~ Unit 1 & 2 temporary M/C (A) cable laid
3/20/13 Off-site power restored (P/C2C power received)
Power Access/Restoration

Status Immediately

after 1F-3,4 Shutdown

3/11/13 Temporary MCR lighting on (Temporary small engine generator)
3/11/13 P/C 4D restored (power source cart)
3/14/11 Yonomori Line 1L step-down transformer cart (66/

6.9kW)

connected to the Shin-Fukushima

Substation

Yonomori Line 1L ~ Okuma Line 3L

connected

Power source for Unit 1 Instrument restored (power source cart)

The power source cart destroyed by H2 explosion

3/18/11 Unit 3 & 4 MC, Switch installation location
3/22/11 Off-site power restored (P/C4D power received)
Power Access/Restoration

Status Immediately

after 1F-6 Shutdown

3/11/13 DG6B startup (6A and 6H were shut down by the

tsunami, 6B is an air-cooled type)

SGTS(B) startup, DC125V/250V (B system) restoration

3/12/11 DC125V/250V (A system) restoration
3/13/11 MUWC(B) startup
3/19/11 RHR 6B startup, temporary RHRS alternative pump startup

(power source cart)

DG6A startup (March 21 shutdown)

3/20/11 Cold shutdown condition
3/22/11 Off-site power restored (M/C6C, 6D power received)
3/23/11 Temporary RHRS alternative pump switched to off-site power
Power Access/Restoration

Status Immediately

after 1F-5 Shutdown

3/12/11 DC125V/250 restoration
3/13/11 MUWC(A), SGTS(A) startup
3/18/11 Temporary RHRS alternative pump startup (power source cart)
3/19/11 RHR 5C startup
3/20/11 Cold shutdown condition
3/22/11 Off-site power restored (M/C6C, 6D power received)
3/23/11 Temporary RHRS alternative pump switched to off-site power

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