Performance of Ontario’s CANDU nuclear generating stations in 2015

By: Donald Jones, P.Eng., retired nuclear industry engineer, 2016 March 19

At the end of 2015 Darlington had a four unit average lifetime Capacity Factor (CF) of 83.6 percent and an average annual CF of 76.1 percent. Bruce A had a four unit average lifetime CF of 69 percent and an average annual CF of 86.1 percent. Bruce B had a four unit average lifetime CF of 83.5 percent and an average annual CF of 84.4 percent. The six unit Pickering station had a six unit average lifetime CF of 72.4 percent and an average annual CF of 78.6 percent. Performance data for 2014 are discussed in reference 1.

The raw performance data for 2015 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 CF. CFs are based on the (net) Reference Unit Power and on the (net) Electricity Supplied, as defined in the PRIS database.

The performance of some of Ontario’s nuclear generating stations is affected by the surplus of generation 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 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) or the Energy Availability Factors (EAF) that are shown in the PRIS database. The EAF adjusts the available energy generation for energy losses attributed to plant management 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 attributed to grid related unavailability and other things. This means that on unreliable grids, for example, UCF will be significantly higher than EAF but for Ontario there will be no significant difference. The UCF and the EAF take into account reductions in plant output due to load cycling and load following. For units that load cycle and/or load follow the CF will be significantly lower than the EAF. For example, Bruce B unit 5 has a 2015 annual CF of 86.4 percent and an EAF of 91 percent. 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 is more than the EAF because of lower than design cooling water temperatures that increase the electrical output of the unit. The only reason for using the EAF here (see later for Bruce units) instead of the UCF is that EAFs are now available in PRIS and UCFs are not presently available (well, the author could not find them).

All manoeuvred reductions in electrical output from Ontario’s nuclear stations to accommodate the much more expensive wind generation are done by the flexible Bruce A and Bruce B stations using turbine steam bypass to condenser and they get paid for the lost revenue. Of course it makes little environmental, economic or technical sense to reduce the low cost output from nuclear stations, with practically zero greenhouse gas emissions, to accommodate expensive unreliable wind generation on the grid that is not needed anyway. The provincially owned Darlington and Pickering stations do not manoeuvre but would have to come off line to accommodate wind and they would not get paid for the lost revenue. While the Bruce electricity output reductions are easily seen from the hourly Generator Output and Capability Report on the website of Ontario’s Independent Electricity System Operator (IESO) it is more difficult to know if nuclear unit shutdowns are to mitigate SBG or are due to forced outages. Maybe an outage was extended, or a planned outage was rescheduled, to accommodate anticipated SBG. However, according to the Bruce Site Updates website there were just two nuclear shutdowns (units 3 and 5) caused by SBG in 2015 compared to one in 2014.

From 2013 September wind generation was curtailed when flexible nuclear manoeuvring reached its limit and before any nuclear unit had to be shutdown and go off line. Starting early 2016 the rules changed again allowing flexible wind generation and solar generation to be curtailed before manoeuvring down nuclear units. Wind operators get paid for the generation that they could have produced under the forecast wind conditions.

Darlington

The four Darlington units came in-service between 1990 and 1993. The design of the primary heat transport system basically follows CANDU 6 although the reactor itself is basically the Bruce A design. At the end of 2015 unit 1 had a lifetime CF of 83.9 percent; unit 2, 79.1 percent; unit 3, 85.9 percent and unit 4, 85.7 percent, for an average lifetime CF of 83.6 percent. The annual CF for unit 1 was 71.3 percent; unit 2, 83.3 percent; unit 3, 64.9 percent and unit 4, 84.9 percent, for an average annual CF of 76.1 percent. The Darlington Station had a month long planned Vacuum Building Outage in 2015 and this, combined with some planned maintenance that extended the outage to about 48 days, affected the CF.

The units had some early start up technical issues but quickly became reliable performers. In 2012 Darlington received a prestigious Award of Excellence from the Institute of Nuclear Power Operations (INPO) which recognizes achievements in safety, operations and management. Darlington units do not provide flexible operation like Bruce A and B units during periods of SBG.

From late 2007 Darlington Station has been preparing for a major refurbishment to start in 2016 October and finish in 2026. Unit 2 will be the first unit to be refurbished followed by units 3, 1, and 4. Based on preliminary outage schedule information Darlington unit 2 will have operated for 26 years by the time it starts refurbishment, while units 3, 1, and 4 would have operated for 26, 29, and 29 years respectively. On 2015 December 23 the Canadian Nuclear Safety Commission (CNSC) licenced the Darlington units to operate up to a maximum of 235,000 equivalent full power hours (EFPHs) at the time of the refurbishment outage. The licence is valid from 2016 January 01 to 2025 November 30. The author doesn’t know if the refurbishment will include improvements to the steam bypass system and a change to the station’s Power Reactor Operating Licence to allow reactor manoeuvring for load cycling and/or load following. The reactor need be manoeuvred quite slowly since it would just be following up on the manoeuvre made by the quicker acting steam bypass system and would be a major attribute during periods of SBG.

Bruce Power

Bruce Power will begin main component replacement (refurbishing) on units 3 to 8 in 2020, starting with unit 6, then units 3, 4, 5, 7, and 8 to add about another 30 to 35 years of operational life to each unit. Starting in 2016 and continuing to 2053 the company will be investing in other life-extension activities that will add a combined 30 reactor-years of operational life to the units, pre-refurbishment. These are the kinds of activities that have been successfully carried out on Bruce Power’s units since 2001. As an example of the result of these activities, unit 8 would have been operating for 43 years prior to commencement of its refurbishment outage in 2030. On 2015 May 28 the CNSC licenced the eight units to operate up to a maximum of 247,000 EFPHs at the time of the unit refurbishment outage. However, by the time unit 8 reaches its refurbishment outage it could have accumulated about 308,000 EFPHs so Bruce Power will have to make its case to the CNSC to allow this higher limit when applying for its new operating licence in 2020. Other units will also likely exceed the 247,000 EFPH number (reference 3). The present new single operating licence now applies to Bruce A and Bruce B and is valid from 2015 June 01 to 2020 May 31.

The refurbishment could provide an opportunity to increase the capacity of the steam bypass system to allow deeper reductions (deeper than the present 300 MWe per unit) in unit electrical output at times of SBG. Alternatively Bruce Power could discuss with the nuclear regulator changes to the station’s Power Reactor Operating Licence to allow reactor manoeuvring, in concert with steam bypass, to provide the same deep (deeper than the present 300 MWe per unit) reductions in electrical output when needed. The reactor need be manoeuvred quite slowly since it would just be following up on the manoeuvre made by the quicker acting steam bypass system.

In 2015 December Bruce Power was honoured with the Platts Global Energy Award for Industry Leadership in the power sector. Established in 1999 and often described as the “Oscars of the energy industry,” the Platts Global Energy Awards highlight corporate and individual innovation, leadership and superior performance in 17 categories that span the entire energy complex. In 2014 Bruce Power was awarded the Institute of Nuclear Power Operators (INPO) Award of Excellence in recognition of its world-class performance.

Bruce A

The four Bruce A units came in-service between 1977 and 1979. Bruce A design is many ways different from Pickering A, the first four unit nuclear station in Ontario. Bruce unit 2 was laid-up in 1995 due to lead contamination and the rest of the units were laid-up between 1996 and 1998 as part of Ontario Power Generation’s nuclear improvement program so that operations could concentrate on Bruce B. Units 3 and 4 were returned to service in 2004 January and 2003 November respectively. Units 1 and 2 both came back to commercial operation in 2012 October after being off line for 15 and 17 years respectively. Units 1 and 2 have been refurbished with new fuel channel assemblies, some new feeders, new steam generators, and with other significant improvements. The four units provide valuable flexibility to the Ontario power grid during SBG periods by reducing electrical output without coming off line.

Lifetime CFs in the IAEA database for units 1 and 2 relate to the original in-service dates and do not include the effect of the mandated lay-up that incorporated retubing. At the end of 2015 units 1 and 2 had lifetime CFs of 66.8 percent and 63.5 percent respectively and annual CFs of 87.4 percent and 99.6 percent. Bruce units are the only ones on the Ontario grid to supply significant output reductions when dispatched by the system operator. The annual EAFs (defined earlier) for units 1 and 2 at the end of 2015 were 87 percent and 98.6 percent respectively. Using the (net) electricity supplied figures and the reference power figure in the IAEA database gives the calculated “refurbished lifetime” CFs, since coming back into service after retubing, as 82 percent for unit 1 and 88 percent for unit 2.

At the end of 2015 units 3 and 4 had lifetime CFs (from original in-service date and do not include the effect of the mandated lay-up) of 73.2 percent and 72.3 percent respectively and annual CFs of 88.9 percent and 68.6 percent. The annual EAFs for units 3 and 4 at the end of 2015 were 89 percent and 68.3 percent respectively. Unit 4 had a long planned maintenance outage during the year.

Bruce A had a four unit average annual CF of 86.1 percent and an average lifetime CF of 69 percent. The average four unit annual EAF was 85.7 percent. There were several planned long maintenance outages on Bruce A in 2015 and some forced outages which lowered the CF. Bruce A units seem to have done very little steam bypass power manoeuvring in 2015.

Bruce B

The four Bruce B units came in-service between 1984 and 1987. The Bruce B design is basically the Bruce A design with improvements. At the end of 2015 unit 5 had a lifetime CF of 84.7; unit 6, 81.5 percent; unit 7, 84.7 percent and unit 8, 83.2 percent, for an average lifetime CF of 83.5 percent. The annual CF for unit 5 was 86.4 percent; unit 6, 74.7 percent; unit 7, 88.4 percent and unit 8 , 87.9 percent, for an average annual CF of 84.4 percent. The four units provide valuable flexibility to the Ontario power grid during SBG periods by reducing electrical output without coming off line. At the end of 2015 the annual EAF average for the four units was 87.4 percent. It looks as if Bruce B did most of the steam bypass power manoeuvring in 2015.The Bruce B Station had about a month long planned Vacuum Building Outage in 2015 and this, combined with some planned and forced outages, lowered the annual CF figures. A week before the Vacuum Building Outage unit 6 went into an 84 day maintenance outage.

Pickering

All six operating units at Pickering will be shutdown by 2024. The intent is to shutdown two units by 2022 and the remaining four will be shutdown by 2024. By 2022 Pickering units 1 and 4 would have been operating for about 50 years and units 5, 6, 7 and 8 for about 38 years. Pickering A and B are now operated by Ontario Power Generation as one station but for clarity the following description will keep the old distinction.

Pickering A (units 1 and 4)

The four Pickering A units came in-service between 1971 and 1973. Pickering A was really the first commercial nuclear station in Ontario. The feasibility of the CANDU design had been proved earlier with the 25 MWe gross Nuclear Power Demonstration (NPD) unit at Rolphton (in-service 1962) and the larger 220 MWe gross unit at Douglas Point (in-service 1968). The Pickering A station was voluntarily laid up in 1997 as part of Ontario Power Generation’s nuclear improvement program so that operations could concentrate on Pickering B. The intention was to bring the units into conformance with the latest regulatory standards so that they could be returned to service. In the end only units 1 and 4 were refurbished and returned to service, in 2005 November and 2003 September respectively, and units 2 and 3 were permanently shutdown.

At the end of 2015 units 1 and 4 had lifetime CFs of 63.6 percent and 66.7 percent respectively and annual CFs of 57.6 percent and 94.6 percent. The lifetime CFs in the IAEA database include the effect of the retubing outages but ignores the mandated lay-up of the units for refurbishments. As well as being laid-up these units have had long periods of shutdown including one for the replacement of pressure tubes in all four units over the period 1985 – 1992 and one in 2007 to improve safety related electrical connections between the Pickering A and B stations. These units do not provide flexible operation like Bruce A and B units during periods of SBG.

Pickering B

The four Pickering B units came in-service between 1983 and 1986. The Pickering B design was based on Pickering A, that was designed in the 1960s, but with much improved safety systems. At the end of 2015 the lifetime CF for unit 5 was 73.2 percent; unit 6, 77.5 percent; unit 7, 77.6 percent and unit 8, 76.0 percent, for an average lifetime CF of 76 percent. The annual CF for unit 5 was 64.9 percent; for unit 6, 67.2 percent; for unit 7, 92.3 percent and for unit 8, 94.9 percent, for an average annual CF of 79.8 percent.

The Pickering station six unit average annual CF was 78.6 percent and the average annual EAF was 78.8 percent.

In 1994 unit 7 set a world record, that still stands, for continuous power production with a run of 894 days (2.45 years). Pickering B units do not provide flexible operation like Bruce A and B units during periods of SBG.

Performance Summary

For 2015 Darlington had a four unit average annual CF of 76.1 percent and an average annual EAF of 76.1 percent.
For 2015 Bruce A had a four unit average annual CF of 86.1 percent and an average annual EAF of 85.7 percent.
For 2015 Bruce B had a four unit average annual CF of 84.4 percent and an average annual EAF of 87.4 percent.
For 2015 Pickering had a six unit average annual CF of 78.6 percent and an average annual EAF of 78.8 percent.

References

1. Performance of Ontario’s CANDU nuclear generating stations in 2014, Don Jones, 2015 March 24,
https://thedonjonesarticles.wordpress.com/2015/03/24/performance-of-ontarios-candu-nuclear-generating-stations-in-2014/

2. Wind and nuclear and the increasing irrelevance of capacity factor in Ontario, Don Jones, 2014 February, https://thedonjonesarticles.wordpress.com/2014/02/22/wind-and-nuclear-and-the-increasing-irrelevance-of-capacity-factor-in-ontario-2014-february/

3. CANDUs with 80 year operating life! Don Jones, 2014 March 04, https://thedonjonesarticles.wordpress.com/2014/03/04/candus-with-80-year-operating-life-2014-march/

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