[Intro Music]
Ontario Power Generation owns and operates
the Pickering and Darlington Nuclear Generating Stations. 
The two stations have a combined generating capacity
of about 6,600 megawatts, 
which meets more than 30 percent
of Ontario’s electricity needs.
The Pickering nuclear station
is comprised of six operating CANDU units
that generate approximately
14 percent of Ontario’s needs. 
Safety of the public and staff is OPG’s top priority. 
Pickering Nuclear has been maintained
and safely operated for more than 40 years. 
Our nuclear stations are designed with
multiple safety systems 
and are staffed by station personnel who are well trained 
to ensure safe operation of the station.
All CANDU stations like
Pickering Nuclear Generating Station
have multiple diverse, independent safety systems,
backup electrical power,
cooling water supplies,
and other barriers for protecting the public
in the extremely unlikely scenario
of a major nuclear event.  
This video will illustrate the many barriers
that are currently in place at the Pickering station, 
and the enhancements that are
being made to these barriers 
to further prevent an event similar to Fukushima 
from occurring at Pickering.
The fundamental nuclear safety principles 
followed by all staff at OPG nuclear facilities 
are based on what is referred to as the three C’s
Control,
Cool and Contain.
For all activities,
priority is given to ensuring that at all times 
the reactor power is controlled,
that the fuel is cooled
and that radiation is contained. 
Supporting the 3Cs principle are five levels of defence
which ensure that multiple independent
and diverse barriers
are maintained to protect the 3Cs at all times.
The 5 levels of defence
assure that the likelihood of accidents are minimized
and that the resulting likelihood of a large
radiological release is extremely small.
Pickering’s 5 levels of defence are:
Robust design and conservative operation
Reliable process systems 
Multi groups of engineered safety systems
Flexible emergency mitigation equipment
Comprehensive emergency preparedness plans
The following illustrates how Control,
Cool and Contain function
and the robustness of Pickering’s design
which is the 1st level of defence.
If an event occurs where it is required,
reactor power is automatically reduced,
and the reactor is shutdown.
This is the first C,  
Control.  
Although the reactor is shutdown, 
the fuel in the reactor continues
to generate a small amount of heat,
so the fuel is continuously cooled.
Like all other Nuclear Power Plants,
Pickering’s normal process systems 
are capable of cooling the reactor.  
If normal cooling is interrupted, 
a unique and reliable design feature of all CANDU stations
called natural circulation, 
will continue to cool the fuel.
Natural circulation provides enough time
for normal power to be restored
or an alternative means of cooling to be established.
Another important feature of the CANDU design
is the ability to cool the reactor
using the very large inventory of water
in the Moderator Tank.
In the unlikely event that natural circulation fails,
maintaining the Moderator Tank filled
and continuously replenished with water
water will keep the reactor cool.
Any steam that is created from fuel cooling
that may be released to the Reactor Building
is managed by Air Conditioning Units.
The ACUs cool and condense the steam
and thereby reduces pressure within containment.
The Pickering Vacuum Building,
another important design feature
for all multi-unit CANDU stations,
is also available to condense and contain any steam.
The Pickering containment system
minimizes radiological releases
by virtue of its very large volume,
thick concrete structure
and maintained at negative pressure
by the Vacuum Building.
To control containment pressure in the longer term,
a filtered air discharge system
comprised of high efficiency filters
can be used for controlled filtered venting.
To illustrate how the 3Cs are protected
by the multiple levels of defence,
consider a station  event where there is a
total sustained loss of all off-site electrical power.  
The Pickering station has multiple diverse and independent
sources of on-site electrical power
that prevent the loss of off-site power 
from progressing to a total station black-out.
If power from the electrical grid becomes unavailable, 
selected Pickering unit will continue to power 
the reliable station process systems automatically.
These systems are the 2nd level of defence.
Also available is the Auxiliary Power System 
that is comprised of two redundant jet engine powered
generators that can power the station process systems.
With electrical loads being supplied by a Pickering unit 
or the Auxiliary Power System,
Pickering’s process systems will ensure
that the 3Cs are maintained. 
This will safely end the event. 
Like all other CANDU stations, 
Pickering has two groups of diverse
engineered safety systems 
that can each protect the 3Cs independently.
Pickering A units were originally designed 
with one group of engineered safety systems,
which ensure that the reactor power is controlled,
the fuel is cooled, and radiation is contained.
Since its initial operation, Pickering A has been
modernized to have an equivalent 2nd group,
which are additional independent and diverse
engineered safety systems to further protect the 3Cs.
These two groups of safety systems
are the 3rd level of defence.
The primary group of safety systems
are automatically powered by Standby Generators
upon loss of the electrical grid.
There are twelve Standby Generators at Pickering
of which only four are required to power the safety systems
and assure that the 3Cs are maintained.
An independent, diverse and seismically qualified
secondary group of safety systems
are also available to protect the 3Cs.
This secondary group of systems
are powered by the Emergency Power Generators
and select Standby Generators.
Successful operation of either group
of the engineered safety systems
will safely end the event 
and prevent a large radiological release.
Although it is very unlikely,
should the engineered safety systems fail to end the event,
Pickering has in place severe
accident management procedures
and supporting flexible Emergency Mitigation Equipment.
This is the 4th level of defence
that has been significantly enhanced
following the lessons learned of the Fukushima event.
The equipment consists of portable diesel
powered generators and pumps that allow the repowering
of essential station systems
and cooling water addition through
permanently installed quick connections.
With the successful protection of the 3Cs being achieved
through Emergency Mitigation Equipment,
the event is safely ended
and large radiological releases are prevented.
For a complete Station Blackout
and a resulting large radiological release to occur,
all the previous four levels of defence would have to fail –
this is extremely unlikely.
Although Pickering has an excellent safety record
and the risk of a large radiological release
is already extremely low,
further safety enhancements are committed
in the Periodic Safety Review
Integrated Implementation Plan.
The cooling capabilities of the 3rd level of defence
at Units 1 and 4 are being strengthened.
A new plant modification is being made
that will allow the use of existing diesel firewater pumps
to provide additional back-up cooling water.
The diesel fire pumps would be unaffected by losses
of both off-site and on-site electrical power.   
The above modifications further bolsters defence in depth
and practically eliminates the likelihood
of a severe accident progressing beyond the capabilities
of the 3rd level of defence.
Pickering will also enhance the reliability
of the EME function that supports
controlled, filtered venting.
When these modifications are factored into the
probabilistic safety assessment
the calculated risk of Pickering will be comparable
to the risk limits that have been established for a new plant.
Although further safety enhancements are being made
and the likelihood of a severe event at Pickering
has been practically  eliminated,
OPG and the Province of Ontario
have in place comprehensive emergency response plans
that cater to a large-scale nuclear emergency.
This is the fifth level of defence.
As illustrated in the recent large-scale Emergency exercise
that was conducted at Pickering in 2017,
emergency preparedness procedures are in place
and incorporated into periodic drills
and exercises for emergency response.
The Pickering Nuclear Generating Station
plays an important role in providing clean low cost power
for the Province of Ontario.
With its robust design,
multiple diverse redundant safety features
and safety-first operating philosophy,
the Pickering Nuclear Generating station
will continue to operate safely
through to the end of commercial operations in 2024.
