IGCC Postdoc Dominic Brennan Talks Nuclear Reactors, Algorithms, and Emissions

What motivated you to come to the United States for the fellowship?

IGCC has already played a big role in the course of my career. My PhD was pure nuclear engineering—but I was really interested in nuclear security. I wanted, ultimately, to combine the two. That’s where IGCC came in.

As I sought to transition from a pure science background to policy, I attended a number of nuclear security events, like the NATO Early Career Nuclear Strategist Workshop. As I was getting my start in this world, I saw—on LinkedIn of all places—IGCC’s Public Policy and Nuclear Threats (PPNT) Boot Camp.

I applied and got to attend the 2024 PPNT Boot Camp, and it was incredible. I absolutely loved it and couldn’t advertise it more if I tried. From there, I got more involved in tech policy, which brought me even closer to the work of IGCC.

Then, I saw [IGCC assistant director for programs and operations] Marie [Thiveos Stewart] post—again, on LinkedIn—about this fellowship. I applied and now I’m here.

Tell me more about your time at PPNT. It sounds like it was a very formative experience.

It was. I was incredibly fortunate because I was working and finishing my PhD at the time, and my boss gave me the time off. Since I was still a student, IGCC funded me to go over, otherwise it would have been very challenging to get to San Diego from England.

I was starting from scratch in this space—coming from the STEM background, I didn’t even know which authors I should be reading. But the speakers and presenters at PPNT are the recommended reading for courses on nuclear security and international relations, so it was a perfect place to get started.

I got to meet these great authors and ask them—really dumb questions [laughs]. They also gave me their own recommended reading, which helped me deep dive. And meeting loads of other people in the space was extremely helpful in getting me started.

What was your PhD dissertation about?

My PhD was very much an engineering doctorate. I focused on designing algorithms and simulating nuclear fuels. It was quite technical, but what I’m really interested in is the extent to which we can use and trust decision-making algorithms.

When it comes to how we design nuclear reactors, we essentially just run millions of design options, set parameters, and let the algorithm pick the best. This means that we, as humans, concede agency to the algorithm.

The question is: what else are we conceding? We don’t always know the assumptions that those algorithms are making—especially if we’re using someone else’s code. We use shortcuts to speed up these simulations, which are generally safe, but we can’t always know when or where they introduce risk.

And how will you follow-up this work under the IGCC fellowship?

My fellowship will develop a taxonomy of decision-making stages—problem definition, decomposition, simulation, algorithm choice, and final solution—identifying where algorithmic decisions can introduce or mitigate nuclear risks.

Hopefully, this behavioral framework can then be used as a simple tool to facilitate nuclear security discussions between AI developers, nuclear engineers, and policymakers.

You’re coming from the UK Department of Energy Security and Net Zero (DESNZ). Tell me about your experience there.

It was a fantastic experience to work at DESNZ and the UK civil service more generally. I joined while finishing up my PhD—basically, because my funding ran out. They put me into positions where I could learn, lead, and take on new responsibilities.

A lot of nuclear-related work there, I assume.

Actually, no. I joined their industrial decarbonization team, where we gave out government grants to private industry trying to reach net‑zero emissions. In the UK, that meant working with a lot of firms working to improve energy efficiency or install electric boilers in factories.

I learned quite a bit there about how the hard work to reduce emissions gets done. The real driving factor wasn’t climate, but energy costs. People were trying to improve the energy efficiency of their industry because reducing energy and heat consumption is a great way to save on costs.

But the department does deal a lot with nuclear power, which features heavily in Britain’s energy and climate strategy. The UK has been trying to revive its nuclear power industry for a long time, but now there’s new momentum for it as a 24/7 source of carbon-free power. And in the wake of the Russia-Ukraine War, the UK need to break its reliance on Russian gas.

In the United States, we’ve recently put climate to the side to focus on energy security. But in the UK, these goals are seen as more related, right?

Yes, they’re very complementary. And nuclear power is interesting because it’s a zero-carbon power source that has a lot of political credibility on the right and therefore gets bipartisan support in both the United States and the UK.

There are three big reasons for this bipartisan support. The first is energy security: when you have more nuclear power being produced in your country, you’re less reliant on fossil fuel imports. The second is affordability: the price of nuclear power is far less volatile than that of fossil fuels, and the UK has the highest industrial energy costs in Europe, so anything that reduces price volatility is valuable. Finally, there’s the net‑zero emissions argument, which drove nuclear power interest in the early 2000s, although that argument is falling out of favor now.

There’s wide political support for nuclear power, but cost remains a perennial barrier. Nuclear plants are really expensive to build. Right now, policymakers are trying to figure out how to reform planning and cost structures to help get more plants built.

I understand you attended the UN Climate Conference, COP27, in Sharm El Sheikh, Egypt. What brought you there and how was the experience?

I got to Sharm on an American Nuclear Society (ANS) ticket. How it works is that nongovernmental organizations (NGOs) like ANS bid for badges to attend the COP. ANS secured a number of these badges and then sent a global email to PhD students and early‑career professionals to enter a competition to be delegates at the COP. A friend and I entered and won.

We got to Egypt and spent four days manning a booth promoting peaceful nuclear power. This was huge because it was only the second year that nuclear was represented at the COP. We spoke with many delegates, especially from developing countries, about nuclear power.

The Global South’s interest in nuclear projects was my biggest takeaway from the conference. I met someone from a development bank and cornered them to ask why they wouldn’t support nuclear projects—they told me they’d support nuclear once the World Bank started funding it, which it now does. It was exciting and we felt accomplished providing a counternarrative to the many anti‑nuclear groups involved in climate activism.

Any highlights from your time in Sharm beyond the conference?

It was mostly business, rather than pleasure. The city is beautiful, and we were an hour bus ride from the venue, so we got to enjoy seeing it on our commute. But the days at COP were 7:00 a.m. to 9:00 p.m., so there wasn’t much time to do anything besides the conference.

The only exception was the last day, when we had a break in the schedule before flying back home. We went on an excursion to go freediving off the southeast coast—and it was incredible. On our way back home, we heard that the beach outpost we had dived from—all the huts, scuba gear, et cetera—had burnt in a fire that had sparked along the coast.

Oh wow, that’s crazy.

Yes, it was very sad, and I hope they were able to recover. I couldn’t recommend more the diving in Sharm El Sheikh. It’s beautiful.

Going back to nuclear—it seems like a lot of engineering expertise is needed to build more reactors. With your engineering background, do you ever think about returning to that instead of staying in policy?

[Laughs]. Indeed, before my PhD I was a nuclear engineer for a year at a consultancy where I was seconded to EDF Energy for practically the entire time. I wasn’t onsite working on the reactors, unfortunately. I mainly did the mathematical work on optimizing fuel costs.

But it is something to think about. In the UK, we’ve come to realize that after 30 years of not building reactors, we lost a nuclear-capable workforce. We haven’t just lost the people who can weld nuclear‑grade welds or pour nuclear‑grade concrete. Another thing that delays construction is having to train thousands of engineers to be able to get these projects to completion.

For me, personally, I find I’m more engaged reading about nuclear security and policy than the physics of fuel burn‑up. That’s just where my interests lie.

Tell me about the move to the United States. Any culture shock so far?

[Laughs]. It’s not that dissimilar from the UK.

I’ve been to the United States often for nuclear conferences, but this is the first time I’ve been longer than two weeks. The culture shock isn’t harsh. I’m really looking forward to experiencing U.S. national holidays—nobody does pomp and circumstance quite like the Americans.

How’s the move been so far?

I already have friends in D.C., so that’s helped to smooth the landing. And D.C. is great for museums, so I’ve been checking those out.

Do you miss Cambridge yet?

I do. It’s such a wonderful university and town. The historic buildings are all twice as old as the United States. It has beautiful gardens and stellar restaurants.

But Cambridge is also small, and having been there for five years, I feel like I’ve seen everything. It’s time to see something new.

That said, I do miss taking long walks by the River Cam, and the 48‑minute fast train to London. Here we’re eight, nine hours from New York City?

It’s only four on Amtrak, maybe five if you take a bus.

Still far too long for my taste.

Fair enough. Would you spend a lot of time in London?

Of course. I had to go in twice a week working at DESNZ, and I have lots of friends living in the city. I’m also a huge fan of West End Theater. I caught my last show, My Neighbor Totoro, right before I left for America. I highly recommend to anyone visiting London.

Noted. And you’re originally from Manchester, right?

Yes, nearby. I’m from a suburb called Cheadle Hulme, which just south of Stockport.

For a small island, you wouldn’t think that a quick trip up north would change the weather much, but it’s always a good few degrees cooler than London or Cambridge. It’s also rainier than Southern England, which I love. It’s very green. The rain makes me feel like I’m home when I visit.