1 - Probabilistic Risk Assessment in Nuclear
Bret Kugelmass: What brought you to nuclear to begin with?
Mark Flaherty: Mark Flaherty began working in nuclear power when he graduated from college in 1986. He is second generation power worker; his father worked in nuclear power at Calvert Cliffs coming out of the Navy in the early 1970’s, where Flaherty is now the Site Vice President. While he was growing up, Flaherty saw the hard work of the nuclear power plant team and the commitment to the team and had memories of plant outages. He was always very mechanically inclined, went to school, and working in a nuclear power plant was a natural fit for him. After graduation, Flaherty started out as a contractor at his dad’s facility, then moved to Davis-Besse in Ohio where he worked as an engineer doing probabilistic risk assessment (PRA). PRA helps develop, from a risk-based perspective, areas or locations where there might be opportunities to add design margin. After Three Mile Island in 1979, the nuclear industry focused on developing new tools to evaluate potential vulnerabilities with the existing plants and adding margin against the vulnerabilities. PRA was one of those new tools. Mark Flaherty and his family moved to the Ginna Nuclear Power Plant outside Rochester, NY, ultimately going on to get his senior reactor operator (SRO) certification allowing him to be a shift technical advisor. After that, Flaherty moved into leadership positions in engineering and regulatory assurance of the organization.
2 - Comparisons of Ginna and Calvert Cliff Stations
Bret Kugelmass: How was the transition from working at a plant to working at the corporate office?
Mark Flaherty: Mark Flaherty had a good transition from working at a plant to working at the corporate office, getting more involved in some of the financial pieces and some of the other industry organizations, like the Electric Power Research Institute (EPRI) and the Nuclear Energy Institute (NEI). After Constellation Energy purchased Ginna, Flaherty was able to bring a lot of the history and site culture back to the corporate offices, as well as some of the decisions that had been made historically. Ginna is a two-loop Westinghouse pressurized water reactor (PWR) that was built from 1966 to 1969 and new features had been added along the way. Davis-Besse was a 600 MW B&W PWR and Calvert Cliffs is a two-unit, two-loop 900 MW Combustion Engineering PWR. Calvert Cliffs had two steam generators per unit, but Calvert Cliffs has four reactor coolant pumps, while Ginna had one steam generator and two pumps. For Combustion Engineering and Westinghouse PWR’s, both reactor coolant pumps must be operational at all times.
3 - Calvert Cliffs Nuclear Power Station
Bret Kugelmass: At what point did you transition back to being on the plant side of nuclear?
Mark Flaherty: Mark Flaherty came to Calvert Cliffs in 2006 as part of his promotion to fill the role of Engineering Site Director. In this role, he was responsible for all engineering activities at the station including design engineering for plant changes, systems engineering for performance monitoring, programs engineering for station health, and capital asset management for the station. While he may not have known every component in the plant, Flaherty knew when to start asking questions and the right type of questions to ask. Right now, Calvert Cliffs is going through centralization with Exelon, which looks at ways to optimize costs for running a nuclear plant. The design organization is a very classic organization that can be centralized because making a change to a system at one plant can easily translate into a change at another plant. The majority of Exelon plants are boiling water reactors (BWR) and about one-third are pressurized water reactors (PWR). Baltimore Gas & Electric (BGE) was the original constructor at Calvert Cliffs in the 1970’s and there were a combination of issues during construction. Calvert Cliffs has two vendors supplying turbines for the site and the operators are licensed to operate both units. With all the rain on the East Coast this summer, the Chesapeake Bay has been churning and a hurricane is on the way, so grass and silt has to be removed from the condenser water boxes. Large amounts of water are needed to condense steam to turn it back into water; Calvert Cliffs draws approximately 2.3 million gallons per minute from the Chesapeake Bay between the two units.
4 - Water, the Environment, and Nuclear Power
Bret Kugelmass: Can other power plants be put by rivers and lakes as well for their water source?
Mark Flaherty: Condensing steam depends on the temperature difference allowed for the water that goes in versus the water that goes out and flow rate. If the delta T is limited, like Calvert Cliffs’ delta T limit at 12 degrees Fahrenheit, discharge water can’t be any more than 12 degrees higher than water taken in by the plant. Rivers are typically smaller bodies of water but may be allowed a larger delta T. The Chesapeake Bay is a brackish water which brings unique aspects of any sea life, such as barnacles, crabs, and jellyfish. Plants located on a river or lake may be more challenged with zebra mussels or smaller fish. Any engineering firm hired to design a new plant would look at all the operating experience and lessons learned from previous builds as opportunities to do things better. Regulations have evolved, in many cases substantially, since the 1950’s and 60’s when the plants were originally sited. After four and a half years, Mark Flaherty returned to corporate offices to be the general manager of all engineering across the three Constellation nuclear sites. Constellation merged with Exelon in 2013. Prior to the merger, Flaherty was brought back to Calvert Cliffs as the plant manager. A plant manager focuses on making sure that the people there have the right standards and are following the expectations. Flaherty sets aside time to have conversations with the craft and workforce to answer questions and get feedback. The biggest challenge is whether the price of nuclear electricity really compensates for the entire big picture of what nuclear brings to the table.
5 - Operational Excellence at Calvert Cliffs
Bret Kugelmass: How can we make sure nuclear is being compensated for its carbon-free nature?
Mark Flaherty: The zero carbon emissions that nuclear power brings to the table is not reflected in the current market. Nuclear power plants are typically viewed as base load, meaning they were designed and expected to run 100% of the time at 100% power. Each of the units shuts down every two years for three weeks to refuel the reactor. That capability is unique to nuclear power. Calvert Cliffs has one of the best operational records as far as keeping the plans at 100% power and keeping the units running very safely and reliably, including efficiently and effectively doing maintenance and refueling the reactor during outages. The Exelon management model created a lot of opportunities for the station to capitalize and implement going forward. Exelon is providing a lot of capital investment for the long term operation of the Calvert Cliffs units.
6 - Exelon’s Target Nuclear Electricity Cost
Bret Kugelmass: Where does Calvert Cliffs fit in the map of how likely nuclear is to survive in the market?
Mark Flaherty: Constellation Energy was formed by the break-up of the original Baltimore Gas & Electric around 1999. From that point, Calvert Cliffs became an unregulated entity, meaning they are expected to produce power and get paid from the marketplace for that power. A regulated utility, as commonly found in the South, is compensated for the units whether they operate or not. There is still oversight from the Nuclear Regulatory Commission (NRC). Exelon has a vision of getting off as a fleet a $25 per megawatt all in. This provides a target that the company will still be profitable if the generation cost for the units can be achieved. Nuclear power can be expensive and has been historically. Each unit is different and increased regulations have worked together to create financial challenges for the industry. Part of the vision to provide cheap electricity is through centralization and working with regulators. Mark Flaherty served as plant manager at Calvert Cliffs for four and a half years and was given the opportunity to become Site Vice President at the plant. Flaherty is always looking out for what opportunities he can grant to his people as part of his legacy. The goal of his team to use nuclear power to safely and reliably produce electrical power for their community. Calvert Cliffs produces one-third of the electricity in the state of Maryland. There is a long term future for nuclear power at all of Exelon’s nuclear power plants.