Ontario’s already “flexible nuclear” CANDU even better by satisfying IESO requirements to replace flexible coal

October 20, 2012
By: Donald Jones, P.Eng., retired nuclear industry engineer, 2012 October.
A condensed version of this article will appear in the upcoming 2012 December edition of the Canadian Nuclear Society’s BULLETIN journal.

“The existing coal fleet, though running at vastly reduced levels from previous years, provides the IESO with desirable flexibility, such as quick ramping and operating reserve, under all market conditions. As Ontario’s coal-fired generation is shut down over the next two years, its associated flexibility will be lost. Therefore, future capacity additions should also possess this flexibility to help facilitate the management of maintenance outages, provide effective ramp capability, supply of operating reserve and even provide regulation when necessary”.

This statement appeared as the last paragraph in the “18-Month Outlook from 2012 Sept. to 2014 Feb.” put out by the Independent Electricity System Operator (IESO) on 2012 Sept. 12. Similar comments have appeared in previous 18-Month Outlooks and referenced in the Canadian Nuclear Society’s BULLETIN journal. Coal is very flexible and hydro is as well when allowed to manoeuvre, combined cycle gas turbines and present nuclear, particularly Darlington’s four units, less so (see reference 1). If there is to be any hope for significant nuclear new build in Ontario it must meet this IESO operational requirement. The Enhanced CANDU 6 (EC6) should meet it by its combination of up to 100 percent steam bypass for rapid manoeuvring followed up by relatively slower reactor power changes when the reactor is available to manoeuvre.  With a turbine governor system capable of automatic generation control this should permit control of generator output directly from an IESO signal, for automatic or manual grid frequency regulation when operating with steam bypass (see Appendix). France and Germany are more permissive than north America in operating their nuclear power plants and allow the grid operator to change plant output directly, which means reactor power changes since their units do not use steam bypass for load changes. This is equivalent to the IESO directly controlling the output of an existing Ontario unit while in the reactor-following-turbine mode of operation (see Appendix). Potentially the EC6 could be far more manoeuvrable than light water reactor new build in Europe that has to at least meet the flexibility regulations of the European Utilities Requirements (EUR) that are based on the requirements of the grid operators, subject to licensing approval by the specific nuclear regulator. The EC6 would have to comply with the manoeuvrability specifications of the EUR if it wants to be part of new build in Europe. The 100 percent steam bypass capability means that the EC6 will be able to provide full power output much quicker than the poison prevent mode of operation on the existing Ontario units to help restore the grid after a grid collapse since the reactor could remain at full power and the turbine would be supplying house load and be ready to quickly ramp up power when requested by the IESO. This also means zero to 100 percent full power maonoeuvrability capability during normal operation allowing a future Ontario grid to be powered by only clean reliable nuclear and hydro with no fossil fuel (reference 2). Now, how can the existing Ontario units meet the IESO requirements. Read the rest of this entry »