Assistant Professor of Mechanical and Nuclear Engineering
Virginia Commonwealth University
Nov 12, 2019
Choosing the unique specialty of nuclear engineering (1:02)
1:02-6:50 (Braden explains why he transitioned from a math to a nuclear engineering and why he chose to study at Texas A&M.)
Q. How did you first become interested in nuclear energy?
A. Braden focuses on security and radiation measurements at Virginia Commonwealth University. Braden was originally a math major but switched to engineering because he wanted to solve real world problems. Braden specializes in nuclear engineering because he wanted to focus on something unique.
Braden attended Texas A&M for all three degrees. Braden grew up in Southern California and had considered UC Berkeley, but chose Texas A&M because the university has two test reactors and courses listed under nuclear engineering. He focused his Master’s on nuclear materials but wanted to switch his focus for his PhD to nuclear nonproliferation and radiation measurements. Nonproliferation is making sure that nuclear materials do not become nuclear weapons. Braden thinks of it as stopping the spread of nuclear weapons and nuclear weapons technology.
Measuring neutrons in nuclear materials (6:51)
6:51-9:41 (Braden explains his PhD focus and how neutrons are measured to account for all nuclear material.)
Q. What was the focus of your specific research during your PhD?
A. Braden looked at safeguards, specifically measuring neutrons as a way to account for all nuclear materials. This is used to verify the stated amounts of materials, such as plutonium. This is done by measuring the radiation signature of the neutrons and the gamma rays emitted from the plutonium. Other methods are used in combination, such as radioactive decay to measure the amount of heat emitted. Devices are used to measure gamma rays, but a higher efficiency is needed to measure neutrons, so they are measured isotropically, or in all directions, so the material is encased in a detector. Measuring plutonium is safe, but handlers wear detectors to measure the dose they are receiving.
Reactor versus weapon plutonium (9:42)
9:42-18:43 (Braden explains the difference between plutonium-239 and plutonium-240. He also discusses )
Q. Does plutonium-239 have a different amount of spontaneous fission events than plutonium-240 and are you able to calculate the ratio between the two using the detectors?
A. Yes, there is a different number of spontaneous fission events between the two. Generally, neutrons tell the amount of plutonium-240, so if the entire material was plutonium-240, this would be the mass. Each plutonium isotope emits a different gamma wave energy, so this can be used to calculate a relative concentration. Plutonium’s Z, or atomic number, is 94, meaning plutonium has 94 electrons and is fairly dense.
The majority of the plutonium in the world is trapped in used fuel. Plutonium as an element is also separated from nuclear waste when it is repurposed. This could then be used to create nuclear weapons. Nuclear weapons production required the ratio of plutonium-240 to be minimized. The weapons grade ratio is about 5 percent plutonium-240 and 95 percent plutonium-239. Reactor grade has a higher percentage of plutonium-240. Researchers are reminded not to explore too much into the exact weapons grade because the information does not want to be widely distributed. The government approves 80 percent plutonium-238, but a reactor is not able to go below this. Braden is attempting to quantify the usefulness of specific plutonium isotopes for weapons use through heat transfer calculations to show that some isotopes can deform weapons. His goal is to reduce the attempts to use plutonium in weapons.
Braden’s experience in the UAE (18:44)
18:44-30:44 (Braden explains why he worked in the UAE and his experience there.)
Q. You had an interesting experience in the UAE?
A. After graduating from Texas A&M, Braden worked at the Nevada National Security site but realized he wanted to return to academia. Braden knew somebody at Khalifa University in the UAE in nuclear engineering who told Braden that the department needed a postdoc with experience in radiation measurement. Braden decided to take the opportunity to not only return to academia, but gain experience living in another country.
Braden saw both advantages and disadvantages of living in the UAE. One advantage Braden experienced was the stronger work-life balance present in the UAE. For example, when Braden’s daughter was born, his boss told him to take off work until he felt ready to return rather than giving Braden a set period of time. An interesting thing to note was that many people in Abu Dhabi spend little time outdoors to avoid the heat and dust. Additionally, only 20 percent of the population is from the UAE, while 80 percent are foreigners who make up the workforce, including nuclear engineers and researchers. When Braden asked locals about their views on climate change, they would respond that the UAE leaders were making good decisions, so individuals did not have to make decisions. Braden saw that women used education as a way to gain independence. Women who pursued a higher education could avoid marrying at an early age. Once they have graduated with a PhD, they had more ability to determine when they got married. Braden noticed that female students averaged higher grades than the male students.
Braden returned to the US after the position ended. He was also ready to return because he found that because there is more time spent on enjoying life, productivity in the workplace is lower than in the US. This means that the number of publications an academic will put out is lower, meaning resumes are less competitive when finding jobs in other countries. Braden then followed the path to Virginia Commonwealth University and has been there for three years.
Inadequate high school preparation (30:45)
30:45-37:59 (Braden discusses how his teaching has been challenged by new students who have not been adequately prepared in high school.)
Q. What are some of the things you focus on when teaching?
A. Braden has identified that a challenge is when students transition from high school to college because the rigour in high schools has lessened over time. Students are having an easier time passing high school, meaning they can spend less time studying and still graduate. This produces college students who do not have basic mathematics skills. This leads many engineering students to change majors and not graduate with an engineering degree. Braden has noted that students who take time off after high school to gain real world experience put more time and effort into their engineering degrees because they have a better understanding of why they want to become an engineer. Braden focuses on keeping firm in his decision to not lessen the requirements to pass his engineering courses and believes high schools must improve preparing students for college.
Reducing nuclear material attractiveness (38:00)
38:00-43:55 (Braden explains how he primarily teaches nonproliferation and nuclear security. He discusses how neptunium can be used to pollute fuel and decrease the ability to use plutonium for nuclear weapons.)
Q. What subjects do you focused on in your teaching?
A. Braden likes to teach what he researchers, including nonproliferation and nuclear security. Lately, Braden has been interested in nuclear material attractiveness. He researches how attractive it is to turn a material into a nuclear weapon and if there are quantifiable ways to reduce the attractiveness. The main ways to create plutonium-240 is the amount of fissions that occur in the fuel, known as burnup. The longer the fuel is in the reactor, the more the isotopes shift away from desireable weapons grade plutonium. Braden is devising a way to pollute the fuel in such a way that does not impact operation economics but encourages proliferation resistance. Adding neptunium to the fuel may work because neptunium captures a neutron, creating plutonium-238, which is not good for weapons use. Neptunium comes from recycling fuel. Currently, though, fuel fabrication facilities only work with uranium, meaning there will be infrastructure costs to implement this. Additionally, Braden has noticed that people care more about economics than proliferation.
A future of solar versus nuclear (43:56)
43:56-47:18 (Braden explains how he foresees a future of solar energy improving and becoming nuclear’s primary competitor. He also discusses nuclear’s primary benefits.)
Q. What is your take on the future of nuclear energy?
A. Braden thinks there are a lot of unknowns. Solar is a primary competitor and is improving rapidly. Braden notes, though, that nuclear energy has advantages that the energy market does not consider. The first is the environmental benefit. The second focuses on decreasing the need for energy imports, which increases a country’s vulnerability. Producing all needed energy decreases a country’s reliance on another state. Reliability is the third, meaning power can still be generated during severe weather events.