Ep 227: Robert Bean - Professor, Nuclear Engineering, Purdue University
Early experience in nuclear academia (1:22)
1:22-10:51 (Robert Bean explains how he first became interested in nuclear engineering and what sparked his interest in academia)
Q: How did you get into the nuclear space?
A: Robert Bean originally wanted to go into the Navy to become a fighter pilot. When he found out he was too tall to become a pilot, Robert decided to pursue engineering at Purdue University so he could design airplanes. He was also interested in nuclear, which led him to fusion-powered spacecraft. Robert didn’t end up working in that field, but it got him into the nuclear space. Between freshman and sophomore year, Robert spent two years as a missionary. When Robert returned to school, he found that the nuclear classes really clicked and were the most interesting part of his education. Nuclear is abstract because you never see the thing you’re working with.
Robert sees his students gain confidence as they go to their first job and show that they do know all the things they’ve been talking about in school. At the same time, Robert hopes his students realize they don’t know everything and strives to provide that balance in his classes. The primary classes Robert teaches are the radiation detection classes. One of the labs is the neutron demonstration, which allows students to give predictions, complete the experiment, and figure out why they were wrong.
Becoming a radiation detection specialist (10:51)
10:51-24:35 (Robert’s post-graduate path to becoming an expert in radiation detection and how he became involved in designing nuclear facilities for safeguards)
Q: What was your first professional job outside of school?
A: Robert Bean stayed in college for his PhD, which later allowed him to become a professor, and paid for graduate school by being an employee of the university and teaching radiation detection classes. His first job was at the Idaho National Laboratory as the radiation detection person for the safeguards team. Safety is what’s done to make sure people don’t get hurt, equipment doesn’t get destroyed, and the public doesn’t get exposed to the radioactive material. Safeguards are things done to make sure the radioactive material is not lost or stolen. A significant fraction of safeguard work is done by measuring the radiation given off by the nuclear material. Robert’s first job was to teach the technicians on the team how to use the radiation detection equipment.
All radiation interaction leads to ionization and excitation of electrons. The detector collects a signal to provide knowledge something with radiation interacted with the detector. Every radioactive isotope gives off a unique signature of gamma energy and quantity. This spectrum can be measured to identify what the radioactive source is and how much of it there is. Typically the gamma rays emitted by radioactive decay are measured. Since uranium-235 and uranium-238 have different half-lives, gamma rays from each can be distinguished and the enrichment can be determined by looking at both. An Active Well Coincidence Counter injects a neutron source so the neutrons can cause fission. This active interrogation allows one to look at the neutrons produced from the fission. This is helpful when gamma rays cannot be used in measurement due to shielding. Plutonium almost always has some measure of plutonium-240, since plutonium-239 absorbs a neutron but doesn’t fission since it is in neutron flux. Since plutonium gives off neutrons, neutrons don’t have to be injected to take a measurement.
Robert Bean worked in radiation detection at Idaho National Labs for 10 years. He eventually shifted over from the safeguards team in the field into more international safeguards and safeguard design. He looked at how to change a design process for a facility so it is designed with the safeguards in mind from the beginning. Most of the benefit comes from getting the right people involved at the front end and making sure the safeguards inspector can get access to the right areas to get the information needed.
Teaching others about nuclear energy (24:35)
24:35-38:11 (Robert reflects on his time in Washington as an advisor to the NNSA and how it brought him back to Purdue University as a full-time faculty member)
Q: What happened next in your story?
A: Robert Bean had always considered that if he left the lab, he would return to university. At the time he accepted an offer to Purdue University, Robert was on assignment in Washington, D.C. as an advisor to one of the NNSA (National Nuclear Security Administration) groups that funded a lot of the projects at Idaho National Labs. The program aimed to bring the lab prospective to Washington and to bring the Washington perspective back to the lab. Once the assignment in Washington ended, Robert put in his notice at Idaho National Lab and started working at Purdue. He is now taking care of the reactor and teaching the same labs he did as a graduate student, but now as part of the faculty. Robert has acquired special knowledge in the specific area of radiation that allows him to bring his specialization to the team.
Robert does a lot of public tours of the reactor, which provides him with opportunities to teach people who know nothing about nuclear a little bit about the technology. He utilizes and promotes the analogy of cooking something on the stove. Not many people, other than the mechanical engineers, understand the heat transfer and the chemistry in cooking. However, every person knows how to use the stove properly and how to notice when something is wrong. The public doesn’t have to understand the nuclear physics; they have to understand whether the plant down the street is operating safely.
Some things that can be measured lead to associated standards, such as lead, arsenic, or radiation. When the ability to measure gets better, standards are dropped to make it safer. However, wisdom must be used to figure out when to do that. One motto at Idaho National Lab is, “Don’t let perfect be the enemy of good enough.” When “good enough” is achieved, one should question whether they should do more. Sometimes the answer is yes, sometimes the answer is no. A real diverse team needs diversity of experience, ways of thinking, and ways of approaching a problem.
Purdue University reactor research (38:11)
38:11-46:04 (A highlight of the Purdue University reactor and some of the current research projects utilizing the facility, including projects in physics and health science)
Q: Tell us about the reactor at Purdue University.
A: Purdue University has the first all-digital reactor under Nuclear Regulatory Commissioning (NRC) licensing. Critical is a state of the reactor where the neutron balance is maintained and is absolutely not related to how many neutrons per second are currently flying around in the reactor. A reactor could be critical at low power or high power. In theory, it could be critical zero power because the reactor is in a state in which the chain reaction would be maintained but there are currently no neutrons present. The reactor is licensed for 10,000 W of thermal heat which is in an appropriate range for providing neutrons for some irradiation for people and seeing temperature effects. Because of the small size, the potential for accidents is basically nothing, which allows students to be on the controls with an operator standing by. The fuel is a two foot cube and includes 16 fuel assemblies with a row of graphite reflector assemblies. It sits at the bottom of a 20 foot deep pool.
Neutron activation analysis is the exposure of something to neutrons and using a gamma detector to detect and measure radioactive isotopes. One physics professor at Purdue is looking at variation in half-life, suspecting that physics is a factor and that the variation is not just because of experimental uncertainty. His experiment is to put down different shapes, like a sphere, cylinder, or cube, of material into the reactor to be exposed to neutrons and measure any differences. A health sciences professor at Purdue has developed a technique to measure heavy metal poisoning. China is having a lot of problems with mine tailings contaminating water supply as it goes through industrialization. She developed a technique which puts a radiation source on someone’s shin bone and uses an x-ray detector to see if there is heavy metal inside the bone. The possible, small but non-zero, risk from the radiation is balanced with the fact that the person might have heavy metal poisoning. If there is heavy metal contamination in someone’s body, it will also be in their toenails. So the professor took some toenail clippings and irradiated them in the reactor. Some of the atoms absorbed neutrons, were put on the gamma detector, which showed that heavy metals were present. She is now working to demonstrate the relationship between the heavy metal content of the body and the heavy metal content of toenail clippings.
Future of small modular reactors (46:04)
46:04-56:20 (Robert Bean explains some of the challenges of nuclear reactor deployment and potential benefits of building small modular reactors)
Q: Why can’t we put one of your reactors in every town?
A: The Purdue reactor is a big open tank that doesn’t produce any electricity. One the reactor starts to be scaled up, the complexity grows dramatically. There is a breakpoint in the economics whether it would be worth building. However, a large number of small reactors could be built versus the small number of large reactors that currently exist. The licensing process is working on small modular reactors (SMR), which serve two primary goals. One goal is getting nuclear power to places like Indonesia that doesn’t need 1,000 MW plants, but instead needs lots of little reactors on their islands. The first SMR to get hopefully deployed will be NuScale, who is working with the Department of Energy to build a prototype at Idaho National Lab.
The Purdue reactor is allowed to make 10,000 W of thermal energy, but this would not be worth it economically outside the university environment because of the loss. In order to take the reactor design and scale it to 1 MW, the reactor would need more cooling power and piping, but is not much more complex. The dream of nuclear power is to produce about 100 MW, which is enough for a city and can still be built small. Once one reactor is built, it creates a revenue stream through electricity production, or possibly district heat, that could fund more reactors. If process heat is the only product, the complexities become a lot less restrictive. Industry has shown an interest in nuclear process heat. Even though they aren’t prepared to take the risk in producing it, they see the benefit if it was to get developed.
Robert Bean imagines that the future of energy in 100 years is probably orbital solar stations. The problem with solar is that the sun only shines half the time on your system. In the time to reach that point, a nuclear system of some kind will be needed. Nuclear offers a lot of advantages, but it does have a high capital cost. Once these facilities are built, they have decades-long lifetimes and have the cheapest electricity production, with the exception of natural gas in the current economy. The technical, social, political, emotional, and economic sides of nuclear cannot be separated. There will continue to be an energy mix, but as long as nuclear maintains its safe and reliable track record, it will continue being part of the mix.