Ep 182: Christer Dahlgren - Principal Engineer, GE Hitachi Nuclear Energy
Sweden’s position on nuclear (0:09)
0:09-7:53 (Christer discusses Sweden’s position on nuclear power and how he became pro-nuclear from an anti-nuclear upbringing.)
Q. You grew up in Sweden? What was that like?
A. Christer Dahlgren is the Principal Engineer for GE’s BWRX300 project. He grew up in a town near Stockholm. During that time, Sweden gained over half of their power from nuclear energy. But after Chernobyl, attitudes towards nuclear changed in Sweden, including Christer’s parents who held an anti-nuclear position. Since Chernobyl, attitudes are beginning to change again. Sweden has achieved carbon free electricity and has used nuclear energy to power industry. While Sweden has developed their wind power, it does not generate enough power alone. Additionally, Sweden has expanded their hydropower as much as possible. If Sweden is unable to continue exporting clean power, neighboring countries will turn to rely on Poland or Germany’s coal power. Changing Sweden’s general views on nuclear power requires overcoming stigma. For Christer, this happened through research. He learned that, compared to other fuels, nuclear is extremely safe. It also takes little space and leaves little waste. Nuclear power also causes the economies of local communities to flourish due to the good pay and high employment.
Learning how to operate a nuclear reactor (7:54)
7:54-18:37 (Christer explains the new GE reactor design and how he transitioned from analytical work to nuclear power plant operations.)
Q. One of the things you’re looking at with the new BWRX300 design is reducing the number of people it takes to operate the plant, right?
A. Yes. Staffing a nuclear power plant is a high cost. The new BWRX300 will still require people to operate the plant, but will have less people and more centralized support than larger models. Smaller models will not reduce the number of nuclear employees overall. For instance, a large plant could staff 800 people while 20 small plants could staff 80 people each for a total of 1600 employees. Because smaller plants cost less and take up less space, more plants can be built than large models.
Christer first became interested in the nuclear industry after taking energy classes in college which sparked his interest in power production. He was then offered a place in the nuclear program at Sweden’s Royal Institute of Technology. Christer focused his master’s thesis on a small reactor that had existed in the center of Sweden. This reactor provided heat during the 1960s and 1970s, but was subjected to a major flooding event. Christer conducted thermohydraulic analysis of the plant and explored the consequences of the accident.
This type of reactor generates district heating which provides heat to a city. Christer sees district heating as an easier way to increase the number of nuclear reactors around the world because much of the current district heating is powered by coal. This is a great entry point for a light water reactor (LWR), which could be used to replace the coal power facilities. However, siting must first be explored to understand which cities can build an LWR. Some countries are not adapted for small reactors but instead only focus on large reactors. The US, on the other hand, may be shifting towards accepting more small modular reactors (SMRs) because the NRC has just proposed a change to the emergency protected zone (EPZ) regulations, which create a minimum boundary around a reactor to protect against accidents. SMRs can have smaller boundaries because they are smaller reactors, and the NRC is beginning to change regulations to reflect this.
After studying the district heating reactor in Sweden, Christer moved to the US and worked with an RBMK reactor, which is the same reactor design as Chernobyl, in Maryland. Christer decided to stay in the US to pursue a PhD at the University of Maryland in College Park. Here he simulated the loss of coolant accident. Christer then began wondering about the actual operations of a nuclear facility, and moved to Michigan to work at the Palisades power plant. He learned a great deal as a reactor operator, stating that he was able to learn something new everyday for 6 years. Coming from an analytical background, this opportunity taught Christer how take a more hands on approach to nuclear power, learning how to respond to events.
Licensing strategy for the BWRX300 (18:37)
18:37-26:54 (Christer gives an example of a nuclear event that he learned about as an operator. He also explains why he began working at GE and introduces the licensing strategy for the new BWRX300 design.)
Q. How do nuclear reactors respond to a transient?
A. The pressurizer within a nuclear reactor can maintain pressure in most transient (a change in the reactor coolant system involving temperature and/or pressure) cases. Several types of events can cause a transient. A pressurizer will not maintain pressure when there is a break in a pipe that causes a leak. It can, however, maintain pressure during a power loss. Transients are caused by either an operator action, such as an intentional cool down, or if, for example, a valve were to fail and open unexpectedly.
After 6 years, Christer grew bored of plant operations and moved to GE where he works on plant designs. He is currently working on the new BWRX300 design. Part of this process is anticipating the licensing process that GE will eventually go through. This includes communicating key issues early on with the NRC to review initial concerns, which will reduce licensing risks later on. To avoid prior problems of spending millions of dollars on licensing fees only for a design not to be built, GE is focusing this time on site specific licensing. This means that they make generic site assumptions to find the most optimum approach.
Optimizing the BWRX300 design (26:55)
26:55-34:46 (Christer discusses the overall approach to designing the BWRX300. )
Q. What was the overall strategy for BWRX300 and how does one design a plant from ideation through to it actually being built?
A. The BWRX300 design began with eliminating the coolant loss accident by simplifying systems. This change resulted in the possibility for a smaller plant design. The strategy was to keep the core systems at the highest safety class and fit them into the most optimum structure possible. This results in a design which is twice as cheap due to the decreased about of concrete required to build the plant. Concrete costs dominate overall project costs, pushing the design team to limit the amount of concrete in the design without sacrificing safety. This required a breakdown of the preconceived notions around what a nuclear plant looks like. This lead to moving the design of the plant underground, which also protects the plant from external hazards. They are also looking into the structures that could be moved outside of the plant to optimize the design further. Additionally, boiling water reactors (BWRs) run at a lower pressure than pressurized water reactors (PWRs), meaning less concrete does not create pressure issues that may be present in PWRs. The BWRX300 design also utilizes metal and has removed the pumping systems. The reactor will be built in a factory and shipped to the site, meaning the design will be further optimized to ensure it can be shipped over roads and assembled on site.
Justifying BWRs over PWRs (34:47)
34:47-43:45 (Christer notes the reason for forging, instead of welding, a pressure vessel. He also discusses his support in designing a BWR instead of a PWR.)
Q. Has anyone pushed back on the requirement to have a forged (single piece) pressure vessel?
A. The configuration of a reactor vessel drives whether or not it is forged. Welds require further inspections, so to save on operation and maintenance (O&M) costs, GE prefers forging. Christer has studied welds from old reactors to determine the effect of neutron bombardment and notes that there is an effect when welding using copper and nickel material. The size of the vessel can also not be reduced greatly because there must be space inside the vessel for the converted steam in a boiling water reactor (BWR). However, they are still smaller than PWRs and can be forged easily in one piece. Additionally, welding creates more complications, and Christer is focusing on simplicity for the BWRX300l.
Even if Christer did not work at GE, he would still choose a BWR over a PWR. This is because the new design must be cheaper and inspections of PWRs are more costly. BWRs and PWRs operate similarly in terms of performance, but the BWRX300 has a more simple design than PWRs. Christer notes that cost can make or break a project, and so optimization is key to the design’s success. Christer’s team is still working on the logistics of optimizing the serviceability of the design, but notes the inclusion of equipment hatches to ensure maintenance can be carried out. Additionally, the fuel building is inside the reactor at the top of the reactor vessel, so there is no transfer of fuel. While the lifetime of the design is shorter than PWRs, the lower cost justifies this because investors will receive a return much sooner.
Designing plants differently (43:46)
43:46-48:51 (Christer discusses the ways he has pushed to do things differently in the nuclear design process.)
Q. How do you find it to be when pushing to do things differently than the way they have been done before?
A. Christer works with experts in the nuclear industry. His colleagues have the historical knowledge of designs that have and have not worked. Christer therefore knows if the new ideas will work or not. For instance, Christer is confident when discussing the decision to use natural circulation instead of pumps. Pumps change the pump flow rate which decreases or increases power output. However, the BWRX300 is based on the previous BSWR design, which does not include pumps and has already undergone the expensive licensing process. It is therefore much cheaper for the BWRX300 design to rely on natural circulation.
Additionally, Christer is changing safety classifications. He looks closely at the International Atomic Energy Agency (IAEA) regulations involving defense lines. Defense lines state that a nuclear plant must have multiple safety systems. Christer optimizes safety by overlaying plant functions and running probabilistic risk analyses. He uses this data to identify redundant safety features and aims to create a framework that creates a rigorous defense line architecture for all systems. This creates a new, transparent decision making process for safety systems and safety classifications.
Approaching different countries for safety approval (48:52)
48:52-54:15 (Christer explains the need for safety systems and the differences between various country’s nuclear regulatory systems.)
Q. Your plant is underground, so how could any radionuclides escape from underground in the case of a meltdown?
A. The design is essentially a cylinder with a pool on top. We do, however, need additional safety systems. These include SCRAM (emergency shutdown), isolation and heat exchange. Additionally, systems must have backup functions and there must be 3 tiers of safety systems.
Although this new safety system has been approved by both Finland and the UK, GE has yet to talk with the NRC. Both Finland and the UK have a tough but pragmatic nuclear culture. Finland requires a great deal of information before approving a project. The UK prefers to engage in dialogue. Canada is IAEA-centric and has rational safety classifications based on where a function is applied. The IAEA has a good framework, allowing GE to adapt to be country-specific.
Christer’s timeline for saving the world (54:16)
54:16-1:02:29 (Christer explains why the BWRX300 will not be built in the next 2 years. He also explains the importance of nuclear energy for the future of humanity.)
Q. What is your timeline for saving the world?
A. The first BWRX300 is expected to be built by 2030. Meeting this goal depends on both GE performance and the willingness of the customer to help, such as by finding a site. Speeding up the design process to build a plant in 2 years relies on a firm commitment from the customer, identifying a site and conducting investigations. However, licensing slows the design process down. Even in countries that do not have existing nuclear regulations, GE must wait for the country to establish one, which is not a fast process. This means that we must wait more than 2 years for the first BWRX300 to be constructed.
In Christer’s mind, nuclear power is important for the future of humanity because decarbonization can not be achieved through renewables alone. Nuclear energy can achieve a decarbonized electric system and district heating on a major scale. Further, nuclear is critical to stopping and reversing climate change. As the number of customers enable more small, cheap plants to be built, costs will decrease and more countries will be able to finance and implement nuclear projects. Christer’s overall goal for nuclear is to create a low cost power that will not rely on government subsidies.