Ep 103: Nicholas Cahill - Reactor Engineer, Calvert Cliffs Nuclear Plant
1 - Profile of a Navy Nuclear Electrician
Bret Kugelmass: What was it like growing up in New Jersey?
Nicholas Cahill: Nicholas Cahill grew up in a densely populated area in New Jersey where all the towns connected to each other with no gaps in between. He had an interest in computer science in middle and high school, leading him to join the Navy to learn more about computer science. Once in, he realized there were multiple fields he could go into related to computer science and he was offered an opportunity to work in the nuclear part of the Navy. Cahill had to take the ASVAB test when he entered the Navy which decided which jobs he would qualify for. The nuclear field has multiple rates, such as an electrician, an electronics technician, or a mechanics; Cahill became an electrician. Navy technology was a little dated, but was a tried and true reliable analog system. Cahill served on the U.S.S. Louisiana ballistic missile submarine out of King’s Bay, Georgia. As an electrician on a six-hour watch, he would monitor equipment and listen for early signs of failure or look for temperature indications. This included continuous monitoring of electrical power production and shifting the plant operations around for maintenance. The six-hour watch shift was followed by a six-hour maintenance shift and a six-hour sleep shift before starting the next 18-hour day.
2 - Criticality Analysis of Fuel Storage
Bret Kugelmass: Why did you decide to stay in nuclear after spending nine years in the Navy?
Nicholas Cahill: After spending nine years in the nuclear Navy, Nicholas Cahill became an advocate for the technology as he learned more about its carbon-free impact on climate change. Nuclear energy is the safest energy production method due to its energy density and the actual repercussions of minor issues on-site are low impact. While in the Navy, Cahill spent three years in upstate New York teaching nuclear operators in the Navy how to operate a fully functional nuclear engine room. He taught them how to work, stand watch, and make trends. In parallel with his job function with the Navy, Cahill got to attend Rensselaer Polytechnic Institute (RPI) where he received his nuclear engineering degree. An opportunity came out with Constellation Energy and Cahill transitioned from a Navy operator into a civilian nuclear engineer. His duties were split between reactor engineering and fuel or safety analysis. Criticality analysis looks as the process of getting the fuel assembly from the new fuel storage area to spent fuel and back into the core. In the original spent fuel pool, fuel was separated by more space to avoid criticality. More fuels can pack closer together is neutron absorbers, such as boron, are placed in between and in the water. He works with a lot of software tools to assist with criticality analysis of fuel storage and they make sure he is executing safe actions.
3 - How Reactor Engineers Support Operations
Bret Kugelmass: How did you switch from the Constellation group to the Exelon group?
Nicholas Cahill: Constellation Energy merged with Exelon, becoming the largest nuclear generation company in the nation. Nicholas Cahill stayed at Calvert Cliffs during the transition. He pulled more out of the safety analysis side, doing less design-type work in reactor engineering and now more operational support, such as moving fuel and maneuvering power levels. Certain plants in the industry will have to change power to follow load based on the economics of electrical energy production. Calvert Cliffs may maneuver power for maintenance items, which could be planned or caused by unexpected conditions related to the Chesapeake Bay. A reactor engineer helps the plant move through the maintenance evolution, specifically what is going on in the core. They may tell the operators how to maneuver the plant in certain control rods or diluting the reactor coolant system to change power, while keeping an eye on peaking factors. Operations has surveillances performed based on technical specifications which specify the frequency between surveillances, depending on the parameter. Some parameters monitored are core tilt and axial shape index. Reactor engineers make sure the plant is not producing too much power in one portion of the core based on technical specifications.
4 - Maintaining Reactor Power and Water Chemistry
Bret Kugelmass: What’s the process of receiving data on power production and making adjustments?
Nicholas Cahill: Boiling water reactors (BWR’s) are able to insert individual control rods which come up from the bottom, compared to pressurized water reactors (PWR’s) like at Calvert Cliffs in which control rods come into the top. BWR’s have more of a challenge in shaping their power. Calvert Cliffs will typically run with all of the control rods out so it doesn’t have to be shaped as much. Reactivity is controlled with boron in the water; the amount of boron can be reduced by putting neutron absorber in the fuel itself. When the plant is operating at 100% power, which is normal operation at Calvert Cliffs, a boron level is maintained. As nuclear fuel is burned out, the boron is diluted with water to bring power back up. The rate that fuel burns is pretty constant, but the changing in boron depends on burning of neutron absorbers as well. Minimizing the water put into the core is important because it becomes wastewater that has to be cleaned up and takes multiple steps to process. Nicholas Cahill participates in a reactivity management program which looks at issues on-site and opportunities to improve either the procedure process or human performance. This is used to identify what challenges the plant is having. He is also part of an industry working group that has multiple different technologies from the PWR world and shares issues and improvements. Cahill advocates for nuclear energy, and science in general, in the community by going around to schools to promote STEM education.
5 - Carbon-Free Base Load Power
Bret Kugelmass: Why is nuclear energy important?
Nicholas Cahill: Nuclear energy is one of the safest ways to have a base load generator. The country is bridging from being a heavy carbon producing electricity generator to having carbon-free and sustainable energy sources, nuclear is the base load energy producer needed to make it to the future of sustainable energy. Exelon has a huge part in solar, wind, and geothermal power as well, but nuclear energy will be the base load for the meantime.