POWER December 2010 - 54

PLANT SAFETY
keys available for the room where manual
head gate closing controls were located, so
the metal doors had to be smashed.
In sum, the accident completely destroyed
Units 2, 7, and 9. Units 5 and 6 were damaged
but were repairable. The remaining five
units were seriously damaged.
Call for Help
Within the first hours after the accident, the
Ministry of Russian Federation for Civil
Defense directed rescuers from across the
country to SSH with the primary mission of
finding and rescuing survivors as quickly as
possible. Within 24 hours, more than 1,500
rescue workers arrived and began working.
Fourteen survivors were rescued in this operation.
Unfortunately, the final death toll
had risen to 75 by the time rescue operations
were suspended on August 29. Most of the
fatalities were to workers who were working
either on the turbine gallery or in the flooded
rooms below (Figure 7).
The equipment destruction also caused
damage to the surrounding environment
from releases of industrial oils. More than
100 metric tons of oil were released into
the river, which killed thousands of fish
in downstream trout farms. Rescue teams
used special chemicals spread by helicopters
to congeal oil that was later manually
removed from the water. By their quick
action, rescue teams managed to minimize
the environmental damage caused by these
oil spills.
Investigations into the Cause
of Failure
A number of forensic investigations where
carried out following the incident. Turbine
foundation bolts were subjected to thorough
examination. The bolts found were
broken, and fatigue damage covered an
average of 65% of a bolt's cross-sectional
area. Some of the bolts had no traces of nut
breaking, meaning that nuts had not even
been installed on the bolts.
Unit 2 medium-level maintenance had
been performed from January 14 to March
16, 2009, for the controls upgrades but also
to eliminate the excessive vibration. Vibration
remained after repairs were completed.
The logs and discussions with plant staff
indicate that Unit 2 was again removed
from service in early August due to continuing
excessive vibration and was held in
reserve. Moreover, Unit 2 was started and
placed into baseload operation the evening
of August 16 and then immediately placed
into " regulating mode " in the early morning
of August 17. That means it was subjected
to more intense cycling service to
follow loads, forcing the unit into multiple
passes through " not recommended " zones
of output power (see Figure 4). Those
stresses were in addition to the long-term
excessive rotating vibration already being
experienced by the unit (see Figure 5).
The logs show that on August 17, 2009,
at 8:13 a.m., ARPJC had set Unit 2 output
power in the " not recommended " zone in
8. Winter freeze. Last winter, ice buildup on the spillway limited the amount of water that
could pass downstream. Workers unsuccessfully attempted to use chain saws to break up the
ice that formed on the spillway. Courtesy: Kirill Elesin, EKRA-Sibir Ltd.
order to meet grid demands, and the plant
operations staff did not object. This was
the final decision-following a long history
of ignoring operating and maintenance
deficiencies and obvious fatigue cracks
in the turbine mounting structure-that
caused the almost complete destruction of
the SSH.
Post-Accident Operation
The accident required all the river water to
pass through the spillway while repairs are
under way. The spillway was not designed to
conduct such large amounts of water in winter.
In addition, last winter the spillway was
covered with enormous amounts of ice, which
was ineffectively removed by means of chain
saws (Figure 8). This problem has been solved
by running some of the restored units and finishing
construction of in-rock bypass channels
that became operational in June 2010.
Spring flood surges in 2011 are again expected
to add water to the Sayno basin in
incredible amounts-up to 6,400 m3
million gps). Water discharge through the
dam spillway is expected to be 3,850 m3
/s (1
million gps). The long-term damage caused
by excessive water flow through the spillway
is unknown.
Rebuilding Continues
Plant reconstruction work continues at full
speed, but the focus seems to be on repairs
rather than on design improvements to ensure
that a similar accident doesn't occur.
At first, the work focused on Units 5 and 6,
which were not seriously damaged by the
accident. The reassembly of those units was
thoroughly scrutinized by the manufacturer,
Power Machines Public Corp., and all the new
engineering solutions were coordinated with
Lenhydroproject Public Corp., which was the
general designer of Sayano-Shushenskaya.
On December 30, 2009, operation of
Unit 6 was restored, and it was successfully
tested in open-circuit operating mode.
On February 24, 2010, operation of Unit
6 was successfully demonstrated with Russian
Prime Minister Vladimir Putin present.
Unit 5 was completely restored and
restarted on March 22, 2010, bringing the
station's capacity up to 1,280 MW.
Operation of Unit 4 was restored on August
2, adding another 640 MW to SSH's capacity.
At the commissioning ceremony, Deputy
Prime Minister of the Russian Federation
Igor Sechin promised that all the decisions
concerning the restoration process will meet
new technical requirements and standards set
by governmental supervisory authorities for
hydropower plant operation.
The restoration of Unit 3 is projected to be
complete by the end of this year. If so, RusHy54
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