Performance of Ontario’s CANDU nuclear generating stations in 2018

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.

All manoeuvred reductions in electrical output from Ontario’s nuclear stations to accommodate SBG are done by the flexible Bruce A and Bruce B stations using turbine steam bypass to the condensers and they get paid for the lost revenue. The provincially owned Darlington and Pickering stations do not manoeuvre but would have to come off line to accommodate SBG. 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.

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.

As the IESO puts it in its Media Centre’s, 2018 Electricity Data, “Nuclear manoeuvring capability offered by Bruce Power supports system reliability by reducing the output of nuclear units by approximately 300 MW each. This capability provides valuable flexibility to the system during period of low demand where surplus baseload generation (SBG) exists, and also helps the IESO prevent nuclear shutdowns. In 2018, there was a significant reduction in the nuclear curtailments and shutdowns due to planned nuclear outages, including refurbishments occurring during typical SBG periods, particularly the spring. As a result, there were only 115 nuclear manoeuvres in 2018, down from 511 in 2017, representing a total of 168 GWh or approximately 0.2 percent of total nuclear energy. No nuclear shutdowns were required in 2018”, and, “The IESO’s variable generation (VG) dispatch allows the system operator to harness the flexibility of wind and solar to help balance the electricity system. In mild weather conditions, the VG dispatch also helps avoid nuclear shutdowns during periods of surplus baseload generation (SBG).” – The VG curtailment also helps reduce or avoid nuclear manoeuvring of the Bruce units. The Bruce units could provide much more than a 300 MW electrical output reduction if they reduced their thermal output (reference 3) together with steam bypass.

Darlington

Darlington follows a three year outage cycle and unit 3 had its planned cyclical maintenance and inspection outage in 2018. Unit 2 was shutdown on 2016 October 15 to commence a refurbishment outage and was shutdown for all of 2018.

For some unknown reason the PRIS database did not have any data for unit 1. The annual generation information used to calculate the annual CF for unit 1 came from Scott Luft’s analysis of the IESO generation data for 2018. At the end of 2018 unit 2 had a lifetime CF of 73.4 percent; unit 3, 85.8 percent and unit 4, 86.0 percent. The annual CF for unit 1 was 97.5 percent (EAF unknown); unit 2, 0 percent (EAF 0 percent); unit 3, 75.2 percent (EAF 75.2 percent) and unit 4, 90.9 percent (EAF 90.7 percent). Darlington units do not provide flexible operation like Bruce A and B units during periods of SBG.  No significant difference between CF and EAF (really the UCF for Ontario units – reference 1) numbers. The three operating units had an average annual CF of 87.9 percent.

Bruce A

The four units are capable of providing valuable flexibility to the Ontario power grid during SBG periods by reducing electrical output, using steam bypass, without coming offline.

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 2018 units 1 and 2 had lifetime CFs of 69.3 percent and 66.3 percent respectively and annual CFs of 81.5 percent (EAF 79.9 percent) and 90.0 percent (EAF 88.1 percent).

At the end of 2018 units 3 and 4 had lifetime CFs (from original in-service date and do not include the effect of the mandated lay-up) of 74.1 percent and 73.3 percent respectively and annual CFs of 95.4 percent (EAF 92.2 percent) and 70.6 percent (EAF 69.1 percent). Unit 4 had a planned maintenance outage of 105 days in 2018. Bruce Power follows a three year outage cycle.

Bruce A had a four unit average annual CF of 84.4 percent (EAF 82.3 percent) and an average lifetime CF of 70.8 percent. Bruce A units seem to have done very little power manoeuvring in 2018 likely because of the Darlington unit 2 refurbishment outage and other maintenance outages.

Bruce B

The four units are capable of providing valuable flexibility to the Ontario power grid during SBG periods by reducing electrical output, using steam bypass, without coming offline.

At the end of 2018 unit 5 had a lifetime CF of 85.0 percent; unit 6,  82.4 percent; unit 7, 85.0 percent and unit 8, 82.7 percent, for an average lifetime CF of 83.8 percent. The annual CF for unit 5 was 98.9 percent (EAF 99.4 percent); unit 6, 98.6 percent (EAF 99.0 percent); unit 7, 99.4 percent (EAF 99.0 percent) and unit 8, 67.3 percent (EAF 67.1 percent), for an average annual CF of 91.0 percent (EAF 91.1 percent).

Little difference between CF and EAF numbers showing that Bruce B did very little power manoeuvring likely because of the Darlington unit 2 refurbishment outage and other nuclear unit outages. Bruce Power follows a three year outage cycle. After setting a site record of 623 consecutive days of operation earlier in 2018 unit 8 completed a planned maintenance and life extension outage of over 100 days in the fall.

Pickering (6 operating units)

The lifetime CFs in the IAEA database include the effect of the retubing outages on units 1 to 4 but ignores the mandated lay-ups and the subsequent refurbishments of units 1 and 4. Pickering units do not provide flexible operation like Bruce A and B units during periods of SBG.

Units 1 and 4 are part of the previously named Pickering A station (units 2 and 3 permanently shutdown) and units 5, 6, 7 and 8 constitute Pickering B. Units 4, 6 and 8 had their planned cyclical maintenance outages in 2018. Unit 4 ran for 344 consecutive days before coming offline for maintenance, the longest run in its history. Each year there are three planned maintenance outages on three different units since Pickering is on a two year outage cycle. A typical outage lasts about 100 days. Before its last outage in 2017 unit 1 had ran for 622 consecutive days, the longest run in its history, and unit 5 ran for 632 consecutive days, a unit record, before coming offline for its maintenance outage.

At the end of 2018 the lifetime CF for unit 1 was 65.0 percent; unit 4, 66.8 percent; unit 5, 74.2 percent; unit 6, 77.9 percent; unit 7, 77.9 percent and unit 8, 75.0 percent for an average lifetime CF of 72.8 percent. The annual CF for unit 1 was 93.2 percent (EAF 93.4 percent); unit 4, 61.9 percent  (EAF 62.1 percent); unit 5, 94.1 percent (EAF 94.8 percent); unit 6, 58.7 percent (EAF 58.7 percent); unit 7, 96.8 percent (EAF 96.7 percent) and unit 8, 58.1 percent (EAF 58.1 percent), for an average annual CF of 77.1 percent (EAF 77.3 percent). No significant difference between CF and EAF numbers.

Radioisotope Production

During the Bruce unit 8 outage radioactive isotope Cobalt-60 was harvested from the reactor. This Low Specific Activity (LSA) Cobalt-60 is used world wide to sterilize medical devices and food products. During the outage medical grade targets of Cobalt-59 for the production of (medical grade) High Specific Activity (HSA) Cobalt-60 were inserted into the reactor and will be irradiated then harvested at the unit’s next maintenance outage. The HSA Cobalt-60 will be used to treat brain tumours through the Gamma Knife. All four Bruce B units now produce HSA Cobalt-60 as well as the LSA Cobalt-60 that they have been producing for over 30 years. HSA Cobalt-60 was previously produced by the National Research Universal (NRU) reactor at Chalk River but the reactor was permanently shutdown on 2018 March 31 after operating for 60 years. Bruce Power is also examining the production of the radioisotope Lutetium-177 at the Bruce site for use in targeted radionuclide therapy to treat cancers like neuroendocrine tumours and prostate cancer. Medical-grade Lutetium is used to destroy cancer cells while leaving healthy cells unaffected.

During the unit 6 maintenance outage at Pickering radioactive isotope Cobalt-60 was harvested from the reactor and Cobalt-59 inserted to be irradiated and removed as Cobalt-60 at the next maintenance outage. Cobalt-60 is presently harvested from three units at Pickering B. Cobalt-60 is used world wide to sterilize medical devices and food products.

In 2018 June Ontario Power Generation announced that Darlington is to become a new source of Molybdenum-99 and will help ensure the world’s long-term supply of this critical medical isotope that is used in over 30 million life-saving diagnostic and medical treatments each year. Molybdenum-99  is the parent isotope of Technetium-99 which is used for skeletal, brain and organ imaging to detect and diagnose harmful diseases, including heart disease and cancer.

Performance Summary

The EAF given in the PRIS database is really the UCF for Ontario units.
For 2018 Darlington had an average annual CF for the three operating units of 87.9 percent. PRIS had no data on unit 1 – see earlier
For 2018 Bruce A had a four unit average annual CF of 84.4 percent  (EAF/UCF, 82.3 percent) and lifetime CF of 70.8 percent.
For 2018 Bruce B had a four unit average annual CF of 91.0 percent (EAF/UCF, 91.1 percent) and lifetime CF of 83.8 percent.
For 2018 Pickering had a six unit average annual CF of 77.1 percent (EAF/UCF 77.3 percent) and lifetime CF of 72.8 percent.

 

References

1. Confusion with the IAEA reactor performance data in the PRIS, Don Jones, 2017 July 28, https://thedonjonesarticles.wordpress.com/2017/07/30/confusion-with-the-iaea-reactor-performance-data-in-the-pris/

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. Why Ontario’s CANDU nuclear reactors don’t load-follow, Don Jones, 2018 July 21,  https://thedonjonesarticles.wordpress.com/2018/07/22/why-ontarios-candu-nuclear-reactors-dont-load-follow/

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