Ontario’s IESO uses wind and solar to reduce the carbon intensity of its electricity system

October 15, 2019

By: Donald Jones, retired nuclear industry engineer, 2019 October 15.

Combined Cycle Gas Turbine (CCGT) power plants produce electricity very efficiently with steady state baseload and intermediate load overall efficiencies of over 60 percent for newer units. Most presently operating units would have somewhat lower efficiencies. Unfortunately on most power grids with significant wind and/or solar generation they rarely operate at steady state (reference 1).

Operating CCGT plants at part load and stopping and starting the gas turbine(s) leads to lower plant efficiency and increased emissions of greenhouse gases per megawatt-hour generated as well as wear and tear on the units. Every time a CCGT is warming up gas is being burned while the gas turbine is slowly increasing power and warming up the heat recovery steam generators (HRSG), and the steam turbine when steam becomes available. This increases the heat rate giving higher kg GHG/MWh. If a CCGT had a bypass stack the gas turbine could be delivering power very quickly but at high heat rate (low overall efficiency) since it would be operating simple cycle and giving higher kg GHG/MWh. When increasing power (manoeuvring/ramping) in the operating range the HRSG and steam turbine metal have to be warmed up which takes away gas for no useful power output, increasing kg GHG/MWh.

Ontario has a very low carbon intensity electricity grid averaging 40 g CO2e/kWh. In 2018 more than 93 percent of the electricity generated in Ontario came from non-GHG emitting resources, predominantly nuclear and hydro with some wind and solar. Nuclear provided 61 percent of generation in 2018. There is about 10000 MW of gas-fired and oil-fired generation connected to the transmission grid mostly CCGTs burning natural gas and just under 5000 MW (nameplate capacity) of wind and solar. CCGTs are used to meet peak load demands and provide operational flexibility. Read the rest of this entry »


CANDU 6 Performance in 2018

April 22, 2019

By: Donald Jones, retired nuclear industry engineer, 2019 April 21

History

The two lead CANDU 6 projects were Gentilly 2 in Quebec and Point Lepreau in New Brunswick and these were quickly followed by Embalse in Argentina and Wolsong, now Wolsong 1, in South Korea and all came into service in the early to mid 1980s. These can be regarded as the first tranche of CANDU 6 build.

The second tranche of CANDU 6 units came with Wolsong 2, 3 and 4 in South Korea, Cernavoda 1 and 2 in Romania, and Qinshan 3-1 and 3-2 in China (the other units at Qinshan site are not CANDU), all entering service between 1996 to 2007. Each of the second tranche CANDU 6 units incorporate lessons learned from operation of the earlier units with changes to meet latest regulatory codes and standards.

Capacity Factor

The Capacity Factors are taken from the PRIS (Power Reactor Information System) database of the IAEA (International Atomic Energy Agency). Note that the Load Factor term used in the PRIS database has the same meaning as Capacity Factor (CF). Capacity Factors are based on the (net) Reference Unit Power and on the (net) Electricity Supplied figures, as defined in the PRIS database. The Energy Availability Factor (EAF) is another performance indicator and is shown in the PRIS database. The EAF adjusts the available energy generation for energy losses attributed to plant management, planned and unplanned, and for external energy losses beyond the control of plant management. The Unit Capability Factor (UCF), another performance metric, only includes energy losses attributed to plant management and excludes the external losses beyond control of plant management like load cycling/load following, grid failures, earthquakes, cooling water temperature higher than reference temperature, floods, lightning strikes, labour disputes outside the plant etc. The UCF seems a much better indicator of how well the unit is being managed than either CF or EAF but it is not specifically identified in the PRIS database (reference 1). Note that Bruce Power and Ontario Power Generation use UCF as a performance indicator.

CANDU 6 Units

Point Lepreau, New Brunswick, Canada. At the end of 2018 the lifetime CF since start of commercial operation in 1983 was 70.9 percent, including the refurbishment outage, and the annual CF for 2018 was 84.6 percent (EAF 84.5 percent). Read the rest of this entry »


Performance of Ontario’s CANDU nuclear generating stations in 2018

April 10, 2019

By: Donald Jones, retired nuclear industry engineer, 2019 April 9

The raw performance data for 2018 are taken from the Power Reactor Information System (PRIS) database of the International Atomic Energy Agency (IAEA). Note that the Load Factor term used in the PRIS database has the same meaning as Capacity Factor (CF). CFs are based on the (net) Reference Unit Power and on the (net) Electricity Supplied, as defined in the PRIS database. For Ontario, at least, the Energy Availability Factor in the PRIS database can be read as the Unit Capability Factor (reference 1). For some unknown reason PRIS database had no data on Darlington unit 1 for 2018.

The performance of some of Ontario’s nuclear generating stations is affected by the surplus baseload generation (SBG) in the province. Some nuclear units saw electricity output reductions during periods of surplus baseload generation (SBG). This means the CFs are not a true performance indicator for those units (reference 2). A better metric of performance in these cases would be the Unit Capability Factor (UCF – used by Ontario Power Generation and by Bruce Power). The Energy Availability Factor (EAF) is another performance indicator and is shown in the PRIS database. The EAF adjusts the available energy generation for energy losses attributed to plant management, planned and unplanned, and for external energy losses beyond the control of plant management while the UCF only includes energy losses attributed to plant management and excludes the external losses beyond control of plant management like load cycling/load following, grid failures, earthquakes, cooling water temperature higher than reference temperature, floods, lightning strikes, labour disputes outside the plant etc.

For Ontario there should be little significant difference between CF,  UCF and EAF for units that do not load cycle (an external energy loss) since other external energy losses will be close to zero. For units that load cycle the UCF will be higher than the EAF and higher than the CF but the EAF should  not be significantly different from the CF. For example, going back to 2017 PRIS data, Bruce B unit 7 had a 2017 annual CF of 92.8 percent and an EAF of 96.3 percent. However based on what was just said above this EAF of 96.3 percent must really be a UCF of 96.3 percent and this anomaly will apply to all EAFs given in this article.The UCF and the EAF are based on reference ambient conditions so, unlike the CF, they cannot exceed 100 percent. In some cases the CF can be more than the EAF because the cooling water temperature is lower than the reference temperature and that increases the electrical output of the unit.
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CANDU cousins in India – Performance in 2018

April 3, 2019

By: Donald Jones, retired nuclear industry engineer, 2019 April 1 

Most of India’s nuclear reactors are of the pressurized heavy water reactor (PHWR) type with horizontal pressure tubes, just like the Canadian designed CANDU. In fact the first PHWR (not the first nuclear reactor) in India was the Rajasthan Atomic Power Project (RAPP) unit and was a CANDU designed by Atomic Energy of Canada Limited (AECL) that used the Douglas Point unit in Ontario as reference design but modified to aid localization. RAPP-1 entered commercial operation 1973 December. While RAPP-1 was being constructed the design of  RAPP-2 was started. However the detonation of a nuclear device by India in 1974 curtailed completion of the design by AECL and India was on its own as far as nuclear technology was concerned. The design was completed by India and RAPP-2 eventually entered commercial operation in 1981 April. Since those early days India has developed its own indigenous designs of  PHWRs with net electrical outputs of 202 MW, 490 MW, and 630 MW. They bear little to no resemblance to Douglas Point. All 14 PHWR units operating in 2018 (excludes RAPP-1 which has been shutdown since 2004, Kakrapar units 1 and 2 which were shutdown due to coolant channel leaks, and Madras unit 1 which was shutdown during 2018 for some unknown reason) were 202 MW (220 MW gross) except for two 490 MW (540 MW gross) units. There were four 630 MW (700 MW gross) units under construction with none in operation. All PHWR power units, except for RAPP-1, are designed, owned, and operated by Nuclear Power Corporation of India Ltd. Several of the country’s PHWRs have been refurbished for extended life operation. For more detailed information on the Indian nuclear program see, Nuclear Power in India (reference 1).

The performance data are taken from the Power Reactor Information System (PRIS) database of the International Atomic Energy Agency (IAEA). Note that the Load Factor term used in the PRIS database has the same meaning as Capacity Factor (CF). CFs are based on the (net) Reference Unit Power and on the (net) Electricity Supplied, as defined in the PRIS database, so capacities referenced in this article are net electrical MW output. The lifetime, or cumulative, CF is based on the date of commercial operation and will include the outage time if the unit has been refurbished. Only the performance of India’s PHWRs is reviewed in detail but India’s four operating non-PHWR units are mentioned.
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CANDU nuclear generating station response to a blackout of the power grid

September 27, 2018

By: Don Jones, retired nuclear industry engineer, 2018 September 27

This is an overview of how a present day CANDU unit (excludes Pickering Generating Station that does not have turbine steam bypass capability and Bruce A that does not have adjuster rods – see later) responds to the loss of the power grid, a load rejection. The design intent is to keep the unit operating to supply its own service loads (house load) while disconnected from the grid and to be ready to reconnect to the grid when the grid becomes available.

All actions are automatic. When the loss of the power grid is detected the circuit breakers connecting the turbine-generator to the grid open. If house load is normally supplied by the unit service transformer the unit service loads (reactor heat transport circulating pumps, boiler feed pumps, condenser cooling water pumps, and other loads) are not affected by the de-energized grid. If the system service transformer were supplying half the unit service loads an automatic transfer would occur to transfer those loads to the unit service transformer. Reactor power is quickly stepped back to around 60 percent of full power by dropping the four mechanical control absorbers (rods) part way into the core, the valves supplying steam to the turbine-generator are closed, and the condenser steam discharge valves (CSDVs) are fully opened to prevent a rise in boiler pressure sufficient to cause opening of the boiler main steam safety valves. The  CSDVs allow the steam that would have gone through the turbine-generator to go directly to the condenser. As the boiler pressure drops because of the fully open CSDVs the CSDVs are partially closed by the boiler pressure control system to maintain boiler pressure at  setpoint. The turbine governor adjusts to supply just enough steam to take care of the house load, around 7 percent of full power.
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Why Ontario’s CANDU nuclear reactors don’t load-follow

July 22, 2018

By: Donald Jones, retired nuclear industry engineer, 2018 July 21
Ontario`s electricity power grid can have surpluses of baseload generation. On windy, sunny, low demand days, a large surplus. This means that the baseload generators, nuclear, run-of-river hydro, wind and solar, need to be manoeuvred. In 2016 Ontario’s Independent Electricity System Operator allowed the curtailment of most of the wind and solar generation before the manoeuvring of nuclear. Before this other generators on the grid had to reduce power to accommodate the generation from wind and solar even though it made no environmental, economic or technical sense to do so since nuclear and hydro supply most of Ontario’s electricity. Hydro manoeuvring is relatively straightforward, nuclear not so.

For example, an item from Ontario Power Generation’s (OPG) 2009 Annual Report confirms that Darlington and Pickering are, “not designed for fluctuating production levels to meet peaking demand“. Under the definition of Nuclear Unit Capability Factor, page 26, it states, “OPG’s nuclear stations are baseload facilities as they have low marginal cost and are not designed for fluctuating production levels to meet peaking demand……“.  However this is not totally correct. Although not designed to respond to frequent IESO (Independent Electricity System Operator) load-following dispatches the design of the CANDU plants did offer the potential for load-cycling (power reduced overnight/weekends) and this has been demonstrated. In the past some domestic units and off-shore units (CANDU 6) did accumulate considerable good experience with load-cycling by manoeuvring the reactor, with some deep power reductions, but not on a continuous daily basis. For example back in the 1980s several of the Bruce B units experienced nine months of load-cycling including deep (down to 60 percent full power, or lower) and shallow reactor power reductions. Analytical studies based on results of in-reactor testing at the Chalk River Laboratories showed that the reactor fuel could withstand daily and weekly load-cycling. However since then, as will be shown below, regulatory concern has restricted any manoeuvring of the nuclear reactor in order to suit market conditions on the power grid.

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Performance of Ontario’s CANDU nuclear generating stations in 2017

April 3, 2018

By: Donald Jones, retired nuclear industry engineer, 2018 March 29

The raw performance data for 2017 are taken from the Power Reactor Information System (PRIS) database of the International Atomic Energy Agency (IAEA). Note that the Load Factor term used in the PRIS database has the same meaning as Capacity Factor (CF). CFs are based on the (net) Reference Unit Power and on the (net) Electricity Supplied, as defined in the PRIS database. For Ontario, at least, the Energy Availability Factor in the PRIS database can be read as the Unit Capability Factor, see later. More information and performance data for 2016 are in references 1 and 2.

The performance of some of Ontario’s nuclear generating stations is affected by the surplus baseload generation (SBG) in the province. The surplus usually arises because of unreliable intermittent wind generation coming in at times of low demand and wind generation is expected to increase even more over the next several years. Some nuclear units saw electricity output reductions during periods of surplus baseload generation (SBG). This means the CFs are not a true performance indicator for those units (reference 3). A better metric of performance in these cases would be the Unit Capability Factor (UCF – used by Ontario Power Generation and by Bruce Power). The Energy Availability Factor (EAF) is another performance indicator and is shown in the PRIS database. The EAF adjusts the available energy generation for energy losses attributed to plant management, planned and unplanned, and for external energy losses beyond the control of plant management while the UCF only includes energy losses attributed to plant management and excludes the external losses beyond control of plant management like load cycling/load following, grid failures, earthquakes, cooling water temperature higher than reference temperature, floods, lightning strikes, labour disputes outside the plant etc.
Read the rest of this entry »