The document discusses the conceptual design of the electrical power system for a proposed 80MWe CANDU small modular reactor. It outlines the objectives, loads, requirements, and evaluated power sources. It determines that a microgrid powered by 2 or more diesel generators would satisfy reliability needs for Class IV power, while a single diesel generator could provide Class III power due to meeting reliability, availability, and startup time requirements. The conclusions recommend this configuration for the conceptual electrical system design.

1. Prepared by Kandarp Mehta
Guided by Dr. Glenn Harvel

2. Sequence of Main Points
 Objective
 Overview of CANDU 80 Small Modular Reactor (SMR)
 Electrical Systems and its purpose
 Design Methodology for a conceptual Electrical Systems of a CANDU 80
 Requirements of the Electrical Systems
 Selection of a Reference Model
 Major Class IV – Class I loads of a CANDU 6
 Scaling Factor
 Major Class IV – Class I loads of a CANDU 80 Mwe
 Evaluated Power Sources
 Criteria for Prioritizing the Requirements
 High, Medium and Low possibility criteria to meet the identified requirements
 Concluding Remarks
 Future Work
 References
 Q&A

3. Objective
 The Small Modular Reactor technology is the latest trend in nuclear
power industry.
 CANDU 80 Mwe reactor is in the conceptual design phase.
 In addition, the Small Modular Reactor is a good option for the
remote or off-grid location, so the Electrical Systems would play a
key role of providing electrical power to the station loads important
to safety during normal operation, shutdown, AOOs, DBAs or severe
accidents.
 The objective of this project is to evaluate various power sources
capable to provide electrical power to the station loads important to
safety for a conceptual design of the Electrical Systems for a CANDU
80 Mwe type Small Modular Reactor (SMR).

4. Overview of CANDU 80 SMR
 Small Modular Reactor (SMR): An advance reactor with an electrical output < 300 Mwe and
factory-fabricated modules / components (components of Nuclear Steam Supply System)
 A CANDU pressure tube can be considered as the module because every pressure tube is
identical and interchangeable.
 Smaller version of the highly successful CANDU nuclear power plants developed in Canada
 300 MWth / 102 MWe type pressurized heavy water Small Modular Reactor
 Single unit power plant
 Systems, Structures and Components of a CANDU 80 are identical to the established CANDU
with little advancement in technology
 Lower capital investment than the larger nuclear plants
 Well suited for the remote or off-grid locations
 Electrical Power in MWe: 102 Mwe (Gross), 95 - 96 Mwe* (Net)
 Station Service Power: 7-8 % of Gross Electrical Power = 6 - 7 MWe

5. Electrical Systems
 An arrangement of electrical power sources, distribution systems, load groups, and
all associated protective relaying, instrumentation, and controls to supply power to
safety-related loads (CSA N290.5)
 Safety-related loads are the component or components of a safety, safety-related, or
safety support system that require electrical or pneumatic energy and essential to safety
of nuclear power plant (CSA N290.5)
 The distribution system incorporates the components such as buses, transformers, switching
devices, cables, rectifiers, inverters etc. that connect the power sources to the load groups.
 Load group = Distribution components+ safety-related loads
 The main purpose of Electrical Systems is to supply sufficient power to safety-
related loads (or SSCs important to safety) to satisfy the safety requirements of a nuclear
power plant through following means: Two - Group Separation, Division Separation, Classes
of power

6. Courtesy: (J. Vucetic, CNSC, 2015)

7. Class of Power Voltage levels Allowable interruption time
Class IV 13.8 kV, 4.16 kV, 600 V To supply the loads which can sustain
long-term power failure [indefinite time]
11.6 kV, 6.3 kV, 600 V
Class III 4.16 kV, 600 V To supply the loads that can be interrupted
only for short duration. [up to 5 min]
Class II 600 V, 120 V (1-Ph) To supply the loads which cannot tolerate
any interruption. [up to 4 millisecond]
Class I 48 VDC,220 V/250 VDC To supply the loads which cannot tolerate
any interruption [uninterruptible]
(University Network of Excellence in Nuclear Engineering, 2014)

8. Design Methodology for a conceptual Electrical
Systems of a CANDU 80

10. Steps for the conceptual Electrical Systems for a CANDU 80
 Establishment of the project objective
 Establishment of the design requirements
 Selection of a Reference Model
 Identification and classification of the safety-related loads or SSCs important to
safety and determination of their associated power consumption [from a Reference
Model]
 Determination of Scale-down factor for a CANDU 80 loads
 Evaluation of various power sources for the Class IV-Class I power systems
 Selection of power sources from the evaluated power sources on the basis of their
ability to meet the identified requirements.

11. Requirements of the Electrical Systems
 Starting Reliability : 5 Attempts
 Capacity : 12 MWe (For Class IV), 1.5 Mwe (For Class III)
 Starting Time : 30 Seconds
 Availability : 100%
 Frequency Deviation : +/- 2%
 Voltage Variation : +/- 10%
 Capability : 3 minutes to accept loads
 Fuel Storage Capacity : 4-7 days
 Mission Time : 8 – 72 hours
 Automatic Start-up : Yes
 Feasibility : Acquire less space and no hazards

12. Reference Model
 CANDU 6 as the reference model
 Set high performance in Canada as well as in overseas countries:
China, Argentina, Romania, South Korea
 Single unit station, a very successful and proven design
 CANDU 9 has been scaled up from a CANDU 6
 Therefore, it is easier to use the identical design features of the
CANDU 6 and scale it down to 80 Mwe for a CANDU 80.

13. Major Class IV loads of a CANDU 6
Components No. CANDU 6
MW HP
Heat Transport Main Circulating Pumps 4 6.7 9000
Boiler Feed Pumps Main 3 3.7 4975
Condensate Extraction Main 2 1.9 2500
Condenser Cooling Water 2 2.6 3500
Generator Excitation - 5.7 -
Heating and Ventilation equipments - - -
Normal Lighting Systems - 0.3 -
Water cooling system for Generator’s stator winding (Centrifugal pumps) 2 75 kW 100
(Steed, 2006)

14. Major Class III loads of a CANDU 6
Components No. CANDU 6
MW HP
Moderator Circulation Pumps 100%
capacity
Main Motors 2 0.75 1000
Pony Motors 2 15 kW 20
Shutdown Cooling System Pumps 2 0.22 300
Boiler Feed Pumps Auxiliary 1 0.26 350
Condensate Extraction Auxiliary 1 56 kW 75
ECC pumps 100% Capacity 2 0.52 700
Recirculating Cooling Water 3 0.75 1000
Raw Service Water 4 0.41 550
* Turbine Turning Gear - 0.055 75
Class I power rectifiers - - -
Fire water pumps - - -
Instrument air compressors 6+2 0.45 600
(Steed, 2006) (University Network of Excellence in Nuclear Engineering, 2014)

15. Major Class II loads of a CANDU 6
Digital control computers (DCCs)
Reactor Regulation Instrumentation
Safety systems equipments
Emergency lighting (600 V power distribution)
Electrically operated process valves (600 V power distribution)
Auxiliary oil pumps on the turbine and generator (600 V power distribution)
Some critical motors
(University Network of Excellence in Nuclear Engineering, 2014)

16. Major Class I loads of a CANDU 6
Components CANDU 6
MW HP MVA Volts
Class II inverters - - 0.15 600 V
120VAC
*DC Seal Oil pumps for Generator 7.5 kW 10 - 120 V
*DC lube oil pump for turbine-Gen bearings 55 kW 75 - 120 V
Turbine Trip circuits - - - 250 V
*Turbine turning gear 55 kW - -
DC stator cooling pumps - - - 120 V
Control & Protection systems
for EDS
- - - -
Logic, Command circuits, control and operator interfaces for
process and safety systems
- - - 48 V
Switchgear control circuit - - - 250 V
(University Network of Excellence in Nuclear Engineering, 2014) (Steed, 2006)

17. Scaling Factor
 Avg. gross electrical power of CANDU 6 reactors in Canada & abroad=7690 MWe / 11 reactors
= 699 MWe
 Avg. net electrical power of CANDU 6 reactors in Canada & abroad =7165 MWe / 11 reactors
= 651 MWe
 Avg. Station Service Power of CANDU 6 reactors in Canada & abroad= 525 MWe / 11 reactors
= 48 MWe
 Gross electrical power of a CANDU 80 Mwe = 102 MWe
 Gross electrical power of a CANDU 80 Mwe = 95 - 96 MWe *
 Station Service Power of a CANDU 80 Mwe = 6-7 MWe
 Scale down factor for a CANDU 80 = Electrical power of CANDU 80 X 100%
Electrical power of CANDU 6
= 102 MWe = 95 MWe = 7 Mwe = 15 %
699 MWe 651 MWe 48 MWe

18.  Note that 15% scaling factor is not applicable to some SSCs because it varies with function
of SSCs and number of particular SSCs used in CANDU 80..
 For example:
Reactor coolant flow in CANDU 80 = 1630 kg/s
Reactor coolant flow in CANDU 6 = 7600 kg/s
Motor rating of PHT pump of CANDU 80 :
Reactor coolant flow in CANDU 80 * Motor rating of PHT pump of CANDU 6
Reactor coolant flow in CANDU 6
Therefore, Motor rating of PHT pump of CANDU 80 = [1630 /7600] * 6.7 Mwe = 1.46 MWe
There are 2 PHT pumps in a CANDU 80.

19. Major Class IV loads of a CANDU 80 Mwe
Components No. CANDU 6 (48 MW) CANDU 80 (6-7 MW)
MW Volts No. MW Volts
Heat Transport Main Circulating Pumps 4 6.7 13800 2 1.46 4160
Boiler Feed Pumps Main 3 3.7 13800 3 0.56 4160
Condensate Extraction Main 2 1.9 4160 2 0.29 2300
Condenser Cooling Water 2 2.6 4160 2 0.39 2300/
4160
Normal Lighting Systems - 0.3 600 V - 0.045 600 V
Water cooling system for Generator’s stator winding
(Centrifugal pumps)
2 75 kW 120 V
MCC
2 11 kW 120 V
MCC
(Steed, 2006)

20. Major Class III loads of a CANDU 80 Mwe
Components No. CANDU 6 (9.6 MW) CANDU 80 (1.5 MW)
MW MW
Moderator Circulation Pumps
100% capacity
Main Motors 2 0.75 0.11
Pony Motors 2 15 kW 2.3 kW
Shutdown Cooling System Pumps 2 0.22 30
Boiler Feed Pumps Auxiliary 1 0.26 0.033
Condensate Extraction Auxiliary 1 56 kW 8.4 kW
ECC pumps 100% Capacity 2 0.52 0.078
Recirculating Cooling Water 3 0.75 0.11
Raw Service Water 4 0.41 0.062
(Steed, 2006)

21. Major Class II loads of a CANDU 80 Mwe
Loads CANDU 6 (Volts) CANDU 80 (Volts)
Digital control computers (DCCs) 120 V 120 V
Reactor Regulation Instrumentation - -
Safety systems equipments 120 V 120 V
Emergency lighting 600 V 600 V
Electrically operated process valves 600 V 600 V
Auxiliary oil pumps on the turbine and
generator
600 V 600 V
Some critical motors 600 V 600 V
(University Network of Excellence in Nuclear Engineering, 2014) (CNSC, 1993)

22. Major Class I loads of a CANDU 80 Mwe
Components CANDU 6 CANDU 80
kW Volts kW Volts
Class II inverters 0.15 MVA 600 V
120VAC
- 600 V
120VAC
*DC Seal Oil pumps for Generator 7.5 120 V 1.125 120 V
*DC lube oil pump for turbine-Gen bearings 55 120 V 8.25 120 V
Turbine Trip circuits - 250 V - 250 V
*Turbine turning gear 55 - 8.25 -
DC stator cooling pumps - 120 V - 120 V
Control & Protection systems for EDS - - - -
Logic, Command circuits, control and operator interfaces for
process and safety systems
- 48 V - 48 V
Switchgear control circuit - 250 V - 250 V
(University Network of Excellence in Nuclear Engineering, 2014) (Steed, 2006) (CNSC, 1993)

23. Evaluated Power Sources
Power Sources Classes of Power
Grid / Micro Grid using DGs IV
Unit’s Generator IV
Hydro Power Plant IV
Diesel Generator III
Gas Turbine III
Reciprocating Engine Genset III
UPS II
Battery I
Thermoelectric Generator I
Fuel Cell I
PV Cell I

24. Results

25. Criteria for Prioritizing the Requirements
 In this project, the identified requirements have been prioritized in following three
categories:
High Priority Requirements : Failure to comply with the requirements would make the
power sources unsuitable for the Electrical System for the
safety of the NPP.
Power source is incapable to supply sufficient power.
For example: Capacity, Start-up time
Medium Priority Requirements : Failure to comply with the requirements would reduce the
effectiveness of the power sources , but capable to supply the
electrical power to the station loads.
For example: Maintainability, Sensitivity to fluctuations
Low Priority Requirements : Failure to comply with the requirements would not affect the
operation of the power sources.
For example: Capital cost, Mobility

26. High, Medium and Low possibility criteria to meet
the identified requirements

32.  Only microgrid or grid and unit's generator satisfy the established requirements.
 As a CANDU 80 SMR is the good option for a remote off-grid location, there would be no
availability of the grid. Hence, in this project, the microgrid or grid powered by the 2 or more
diesel generators has been considered for the class IV power supply.
 The class IV power supply should provide power through at least 2 or more feeders from
different sources, and by providing power from 2 of more diesel generators would satisfy that
requirement.
 The diesel generator has been chosen as a class III power supply because it satisfies the
reliability, availability, start up time, fuel storage, stability and feasibility requirements.
 Gas Turbine has not been considered because its start-up time is 40 seconds, and Natural
gas is tremendously dangerous.
 Natural gas is highly flammable and toxic, so the leaks may cause fire or explosion.
 The fuel cells and PV cells: lack of reliability, capacity, mission time and availability
 Thermoelectric generators : lack of reliability, capacity and availability
 Battery and UPS: satisfy the mission time and fast start-up without interruption compare to
other sources.

34. Concluding Remarks
The main focus of the EPS conceptual design has been on the evaluation
of the power sources that can comply with the reliability, availability,
mission time, start-up time, capacity and feasibility requirements. This
project has identified following power sources for the conceptual
electrical systems for a CANDU 80:
Class IV Grid / Micro grid using 12 - 15 MWe Diesel
Generators [Alstom-GE]
Class III 2 MWe Diesel Generators [Mitsubishi]
Class II UPS
Class I Two 120 cells 912 Ah Lead Calcium
batteries

35. Future Work
The Gas turbine would become a good alternative for the diesel generators if the
systems can tolerate power interruption for 40 seconds. Hence, the gas turbine would
be studied for the micro grid and class III power supply as a part of future work.
Furthermore, the Deterministic Safety Analysis and Probabilistic Safety Assessment
need to be provided in the future for demonstrating that the EPS meets the safety
requirements during the normal operation, potential accidents, AOO,DBAs and
BDBAs.

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42. THANK YOU

43. Q & A